Loading...
Piazza Serena TR 30092 BCPR2021-0027 - Geotechnical ReportENGINEERS + GEOLOGISTS + ENVIRONMENTAL SCIENTISTS December 20, 2021 J.N. 21-176 RICHMOND AMERICAN HOMES 391 North Main Street, Suite 205 Corona, California 92880 Attention: Mr. Edgar Gomez Subject: Updated Geotechnical Recommendations and Review of Precise Grading Plans, Bella at Piazza Serena Project, Lots 1, 5-14, 20-47, 57-69 and 90-97, Tract 30092, City of La Quinta, Riverside County, California References: See Attached List Dear Mr. Gomez: Per your request, Petra Geosciences, Inc. (Petra) is providing herein our updated geotechnical recommendations for the subject 60 graded residential lots within Tract 30092 in the city of La Quinta (Figure 1). This report is based on our review of pertinent geotechnical reports (referenced herein), our recent due diligence assessment (Petra, 2021 a), the requirements of the 2019 California Building Code (CBC), and our engineering judgment and professional opinion. The purpose of this report is to present geotechnical recommendations for site precise grading, and for the proposed site improvements. Although we previously provided foundation design recommendations (Petra, 2021b), they have been reiterated herein for ease of reference. General Site Overview Overall, Tract 30092 is comprised of 97 lots within approximately 38 acres of land, 37 lots of which are currently occupied with single-family homes and not a part of the proposed development. Rough graded Lots 1, 5 through 14, 20 through 47, 57 through 69, and 90 through 97 comprise the subject lots for this project. Underground utilities appear to have been constructed and stubbed behind the curb, and interior tract streets are asphalt paved with a base layer (see site layout shown on Figure 2). Overall, the subject property is bounded by Monroe Street on the east, 58t' Avenue on the south, an existing residential tract on the north, and offices and yard of the Imperial Irrigation District (IID) La Quinta office on the west. Across 58' Avenue to the south and Monroe Street to the east is active farmland. The gated entrance to the subject property is off 58t1i Avenue. Interior asphalt -paved streets include IL Serenata Drive, Pasatiempo Court, Residenza Court, Canata Drive, Arpeggio Drive, Fiori del Deserto Drive, Pompeti, and Offices Strategically Positioned Throughout Southern California RIVERSIDE COUNTY OFFICE 40880 County Center Drive, Suite M, Temecula, CA 92591 T:951.600.9271 F:951.719.1499 For more information visit us online at www.i)etra-inc.com RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 2 Vida Bella Drive. Prior to development, elevations within the subject site were on the order of -60 to -66 feet above mean sea level (msl) and sloping to the southeast. Previous Site Grading Earth Systems Southwest (ESSW) provided observation and testing during rough grading of Tract 30092 which started on January 17, 2005 (ESSW, 2005). ESSW indicated that their intermittent observation and testing during grading operations ended on April 7, 2005. Prior to grading the site consisted of vacant desert land with sparse to heavy desert vegetation. The site was moistures conditioned prior to clearing vegetation. The lots were over -excavated to a depth of 2 feet below footings or 3 feet below finish pad, whichever was greater. The exposed surface was processed by either moistening or drying of soils and compacting to a minimum of 90 percent to a depth of 12 inches. Fill materials consisting of onsite and import soils were then placed in thin lifts, moisture conditioned, and compacted. Areas not meeting 90 percent compaction were reworked and retested. After reworking of low - density areas, test results indicate that a minimum of 90 percent relative compaction has been obtained within the areas tested. ESSW stated that, based upon intermittent observations and testing during grading operation, from January 17 through April 7, 2005 on this project, it is their opinion that the grading has met the intent of the recommendations of the referenced geotechnical engineering report, as well as the grading ordinances of the City of La Quinta. Discussion of Previous Site Grading Petra reviewed the reported compaction test results provided in the final report by ESSW (2005). It appears that all failing tests were retested and reported to achieve a minimum 90 percent relative compaction. Elevation(s) of the retests were not provided. Description of the compaction test locations were not identified by lot number. What appears to be removal bottom tests were not identified with elevations. Finish grade tests were listed for 22 locations of the 97 lots within the tract. Finish grade tests were not identified with elevations. Without test elevations, it is difficult to ascertain the total amount of fill underlying each lot. We reviewed the five compaction maps attached to the ESSW (2005) final report. No tests were plotted on 16 of the 97 lots. On 14 lots, only the bottom removal test(s) are plotted. Assuming that an over -excavation depth of 3 feet below finish pad grade was completed, 8 lots have 3 feet or more fill without compaction tests reported, and 8 lots with between 2 and 3 feet of fill without compaction tests reported. 16 F%TFA SOLID AS A ROCK GEOSCIENCES- RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 3 In our review of Google Earth aerial photographs of the subject property, it was noted that earthwork continued after the July 11, 2005 date of the ESSW final report. In an aerial photograph dated December 2005, the tract was rough graded, model homes were under construction on Lots 2 through 4, and foundation/slab construction was underway on 15 of the 37 lots that are not a part of the subject property. In addition, a well -developed, green belt of vegetation was noted along the rear of subject Lots 41 through 47. Although clarity of the color photograph is limited, the water well on Lot 41 may still be present. An aerial photograph dated January 16, 2006 depicted what appeared to be extensive watering of haul roads throughout the subject lots and what appeared to be import trucks within Lots 30 to 41. Additionally, highly hummocky surfaces visible on Lots 5 through 14 suggests that stockpiled soils covered the lots. The green belt along the rear of Lots 41 through 47 is no longer visible. For comparison purposes, a 2006 USDA color aerial provided by EDR (Petra, 2021c) depicts similar watering of the subject pads and hummocky pad surfaces on Subject Lots 6 through 10 and possible on subject Lots 25 through 29. Furthermore, what appears to be a depression on subject Lot 41 suggests the abandoned well excavation has not been backfilled. As a result the aforementioned deficiencies, Petra conducted a field assessment of graded conditions within the subject property, using both hollow -stem borings and Cone Penetration Test (CPT) soundings. Our assessment is discussed later in this report. Current Site Conditions In March 2021, a representative of Petra conducted a site reconnaissance to observe the current surface conditions at subject site. A wrought iron electrical gate was noted at the south entrance to the site on Paseotiempo Court. Another wrought iron gate was also noted at the east end of Vida Bella Drive. Block walls exist along the perimeter of the tract, and along the boundary of occupied lots and the subject lots. Wooden fencing with locked gates were observed across interior streets, separating existing residences from the subject vacant lots. Underground utilities were noted within the interior streets, and laterals were stubbed behind the curb and gutter. Multiple pad -mounted transformers were observed onsite during our site reconnaissance. Streetlights were not observed. At the time of our site reconnaissance, the surface of the subject pads was level with no detectable signs of significant desiccation cracks. Erosional remnants were common to temporary slopes along the front of the pads, in some cases extending well back into the lot. In some areas, interior pad voids were observed suggesting localized water infiltration and either piping or soil collapse. Some of these voids were up to 0 GE■�G ENCi EM SOLID AS A ROCK RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 4 one or two foot wide, two feet in length and one to two feet in depth. In one instance (Lot 44), a large void was observed behind the curb, suggesting piping along a utility line. A light to locally dense amount of vegetation was observed on the graded pads, which included weeds, bushes, and scattered small trees. Weeds were also observed emanating from asphalt street cracks and from asphalt street/curb and gutter contacts. Occasional small piles containing concrete or brick fragments were noted on the subject property, and scattered surface gravel were locally common. Well -developed bushes and grasses were noted at the rear of Lots 91 and 93. At the time of our reconnaissance, free water and saturated soils were not present; however, enough water has been seeping from this area to create a shallow erosional feature extending from the vegetation at the rear of Lot 91 to the street. Efflorescence staining was noted along the base of the block wall at the boundary between the subject vacant lots and existing residences. Precise Grading Plan Review Proposed Construction and Precise Grading The purpose of this review is to verify that the proposed precise grading plans for the subject lots are consistent with geotechnical grading and foundation recommendations provided herein. Our review of the Model and Production Precise Grading Plans prepared by Hunsaker and Associates, Inc. (H&A, undated) indicate that one-story, single-family homes with attached garages are proposed. The single-family residences will be of wood -frame construction with first floor slabs constructed on -grade. Concrete driveways will provide access to the adjacent streets and walkways will provide access from the driveways to the front doors. The building pads will be graded to collect any rear and side yard surface water and deliver it drain inlets and a network of subsurface area drains to transmit it to the adjacent street curb outlets. All subject lots appear to be presently in a rough -graded condition with surface elevations at or near the previous rough grades. Minor cuts and fills of less than 0.5 foot appear to be required within the subject lots to provide positive drainage away from the residence. Earth swales are proposed within the rear and side yard areas to collect surface water and convey it to the front yards via area drains. The flow lines of the earth swales are proposed at a minimum gradient of one-half percent. PEI FM SOL10 AS A ROCK GEOSCIENCES- RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 5 On the model precise grading plans, finish pad elevations vary between adjacent lots by 0.5 foot or less. On the production precise grading plans, finish pad elevations vary between adjacent lots by 0 to 1.8 feet with most in the 0.4- to 0.5-foot range. Based upon our review, model and production lots precise grading plans by Hunsaker and Associates Irvine, Inc. (undated) are consistent with geotechnical grading and foundation recommendations provided herein. Supplemental Field Assessment and Laboratory Testing A representative of Petra previously conducted an initial site reconnaissance and performed photo documentation to evaluate the current condition of the property and mark -out for DigAlert clearance. Petra returned to the site on March 17, 2021 to conduct a limited field exploration to evaluate the natural subsurface soils, assess shallow groundwater depths and assess liquefaction potential. The initial field work included the drilling of three Cone Penetration Test (CPT) soundings (CPT-1 through CPT-3). Subsequently, Petra returned to the subject site to drill, log, and sample 15 hollow -stem auger borings (B-1 through B-15) on March 23, 2021. Boring Logs and CPT sounding results are provided in Appendix A. CPT soundings were completed to a depth of 65 feet below the ground surface (bgs). Seismic shear wave velocities were measured in one CPT at five-foot intervals. Groundwater depth was also measured in one CPT. Hollow stem auger borings were drilled and sampled to a maximum depth of approximately 9.5 feet below existing grades. Relatively undisturbed ring and disturbed, representative bulk samples of soil were collected from the borings for laboratory testing. Following sampling, the borings were backfilled with spoils. Locations of the borings and CPT soundings are depicted on Figure 2. Boring Data Based on our observations and sampling conducted from the 15 exploratory hollow -stem auger borings, sufficient removals appear to have been performed within the site during the previous remedial grading operations. The compacted fills encountered within our borings were found to be supported by medium dense alluvium. Based on our review of the original site topography, finish pad grades and assumed remedial removal depths recommended by ESSW (2004), we anticipated approximately 3 feet of compacted fills to support the subject building pads. Following our 15 borings, we observed the subject lots to be mostly supported by fills 2.5 to 4 feet in thickness. Based on the hollow -stem auger drill rig sampler blow counts, visual observations of the samples obtained during drilling and a comparison of the drive sample data, the in -place engineered fill materials at the 15 total borings (approximately one per every 4 lots) were observed to be II �� SOLID AS A ROCK GEOSCIENCES"° RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 6 sufficiently well compacted; however, near surface soils appear dry and slightly desiccated with the passage of time, i.e., 15 years since grading was completed. Cone Penetration Test (CPT) Soundings Additionally, three CPT soundings were performed within the subject property (identified herein as CPT-1 through CPT-3) to a maximum depth of 65.45 feet bgs. The locations of our borings and CPT soundings are shown on Figure 2. In accordance with the 2019 CBC, average shear -wave velocity measurements are required to determine the Soil Profile Type Classification of earth materials underlying the subject site to a depth of 30 meters (98.43 feet). Soil Profile Type is used to determine seismic design parameters provided later in this report. In CPT-1, shear wave measurements were made from the probe with a tip depth of 5.25 feet to 65.29 feet below the ground surface. Geophone depths were placed at a depth of 0.66 foot higher than the tip. Energy waves were generated by the CPT truck conducting a series of surface impacts. Travel time, as measured from the ground surface to the geophone, measures the S-wave velocity at approximate 5-foot intervals. The final measured velocity is 994 feet per second (f/s) at 64.63 feet. Based upon this data, a Soil Profile Type of D was used for the subject site classification. Laboratory Testing Limited laboratory testing has been completed on various representative samples collected from the drill rig locations for classification and engineering analysis purposes. Testing includes in situ density and moisture content, maximum density and optimum moisture content, expansion potential, and soil corrosivity. Results of limited in-house testing of representative samples indicate that the expansion index (EI) of the soils are in the very low to low EI range. An explanation of testing procedures and a summary of laboratory test results are provided in Appendix B. The in -site dry density and moisture content results are presented on the boring logs (Appendix A). FINDINGS Groundwater Borings drilled by Sladden (2001) and ESSW (2004) reported that groundwater was encountered at depths of 25 to 30 feet and 38 feet below the ground surface, respectively; however, ESSW stated that historical groundwater depth may have been as shallow as 5 feet below the ground surface (1961). Historical data from a State well near the southeast corner of Monroe Street and Airport Boulevard reported groundwater at a depth of approximately 15 feet below the ground surface in 1963 (CVWD, 2013). 0 SOLID AS A ROCK GEOSCIENCES"6 RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 7 Groundwater was not encountered in Petra's recent borings to a maximum depth of 9.5 feet below grade. In the recent CPT soundings groundwater was encountered at a depth of approximately 65 feet. Faulting and Nearby Seismic Sources Based on our review of the referenced geologic maps and literature, no active faults are known to project through the property. Furthermore, the site does not lie within the boundaries of an "Earthquake Fault Zone" as defined by the State of California in the Alquist-Priolo Earthquake Fault Zoning Act (CGS, 2018). The Alquist-Priolo Earthquake Fault Zoning Act (AP Act) defines an active fault as one that "has had surface displacement within Holocene time (about the last 11,000 years)." The main objective of the AP Act is to prevent the construction of dwellings on top of active faults that could displace the ground surface resulting in loss of life and property. No evidence of faulting was reported on the subject property by former consultants Sladden (2001) or ESSW (2004) or was observed within the subject site during our recent field work. According to the USGS Unified Hazard Tool website and/or 2010 CGS Fault Activity Map of California, the Coachella segment of the San Andreas Fault zone, located approximately 7.5 miles east-northeast of the site, would probably generate the most severe site ground motions and, therefore, is the majority contributor to the deterministic minimum component of the ground motion models. The subject site is located at less than 9.5 miles (15 km) from the surface projection of this fault system, which is capable of producing a magnitude 7 or larger events with a slip rate along the fault greater than 0.04 inch per year. As such, the site should be considered as a Near -Fault Site in accordance with ASCE 7-16, Section 11.4.1. It should be noted that a concealed fault is mapped along the west side of the Coachella Valley, orientated roughly parallel to the Santa Rosa Mountains (Sneed, and Bryant, 2010; Sneed and Bryant, 2020). This fault is not mapped on the State of California Alquist-Priolo Map, State Fault Map, or the Riverside County Fault Map. Due to the small scale of maps provided in the subsidence reports for Coachella Valley (Sneed, Bryant, and Solt, 2010; Sneed and Bryant, 2020), it appears that this concealed fault either crosses the southwest portion of Tract 30092 or lies just beyond the tract boundary. Strong Ground Motions The site is in a seismically active area of Southern California and will likely be subjected to very strong seismically related ground shaking during the anticipated life span of the project. Structures within the site should therefore be designed and constructed to resist the effects of strong ground motion in accordance 1 6 PE 1M SOLID AS A ROCK RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 8 with the 2019 California Building Code (2019 CBC). Based on our CPT soundings, the site may be classified as Site Class D (Appendix A). Secondary Seismic Effects The site and immediate area exhibit gentle -sloping land that is not typically prone to landsliding. Secondary effects of seismic activity normally considered as possible hazards to a site include several types of ground failure. Various general types of ground failures, which might occur because of severe ground shaking at the site include liquefaction, ground subsidence, ground lurching and lateral spreading. The probability of occurrence of each type of ground failure depends on the severity of the earthquake, distance from faults, topography, subsoil, and groundwater conditions, in addition to other factors. Based on site conditions and gentle topography across the site, landsliding, significant ground lurching, and lateral spreading are considered unlikely at the site. The potential for liquefaction and ground subsidence due to seismic shaking is anticipated to be high. A site -specific analysis of liquefaction and seismic -related subsidence (dynamic settlement) is discussed later in this text. Data from the liquefaction analysis in provided in Appendix C. Seismically induced flooding that might be considered a potential hazard to a site normally includes flooding due to tsunami or seiche (i.e., a wave -like oscillation of the surface of water in an enclosed basin) that may be initiated by a strong earthquake or failure of a major reservoir or retention structure upstream of the site. No major reservoirs are located up -gradient within the near vicinity of the site. The potential for seiche is considered very low. Preliminary Seismic Design Parameters Earthquake loads on earthen structures and buildings are a function of ground acceleration which may be determined from the site -specific ground motion analysis. Alternatively, a design response spectrum can be developed for certain sites based on the code guidelines. To provide the design team with the parameters necessary to construct the design acceleration response spectrum for this project, we used two computer applications. Specifically, the first computer application, which was jointly developed by Structural Engineering Association of California (SEAOC) and California's Office of Statewide Health Planning and Development (OSHPD), the SEA/OSHPD Seismic Design Maps Tool website, https://seismicmaps.org, is used to calculate the ground motion parameters (Appendix D). The second computer application, the United Stated Geological Survey (USGS) Unified Hazard Tool website, https://earthquake.usgs.gov/hazards/interactive/, is used to estimate the earthquake magnitude and the distance to surface projection of the fault. GEOS ENCi EM SOLID AS A ROCK RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 9 A seismic risk category of II was assigned to the proposed building in accordance with 2019 CBC, Table 1604.5. To run the above computer applications, site latitude and longitude, risk category and knowledge of "Site Class" are required. The site class definition depends on the average shear wave velocity, Vs30, within the upper 30 meters (approximately 100 feet) of site soils. A seismic risk category of D was assigned to the proposed building(s) in accordance with 2019 CBC, Table 1604.5. A shear wave velocity of 994 feet per second (288 meters per second) for the upper 100 feet was used for the site based on direct measurement of small -strain shear wave velocity and ASCE 7-16, Article 20.4 procedure. As such, in accordance with ASCE 7-16, Table 20.3-1, Site Class D (D- Stiff Soil as per SEA/OSHPD software) has been assigned to the subject site. The following table, Table 1, provides parameters required to construct the seismic response coefficient, C5, curve based on ASCE 7-16, Article 12.8 guidelines. {Remainder of page intentionally left blank} OPEMASOLID AS A ROCK RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta TABLE 1 Seismic Design Parameters December 20, 2021 J.N. 21-176 Page 10 Ground Motion Parameters Specific Reference Parameter Unit Value Site Latitude (North) - 33.6292 ° Site Longitude (West) - -116.2354 ° Site Class Definition Section 1613.2.2 0), Chapter 20 (2) D (4) - Assumed Seismic Risk Category Table 1604.5 (I) II - Mw - Earthquake Magnitude USGS Unified Hazard Tool (3) 8.01 (3) - R — Distance to Surface Projection of Fault USGS Unified Hazard Tool (3) 11.94 (3) Km S, - Mapped Spectral Response Acceleration Figure 1613.2.1(1) (I) 1.5 (4) G Short Period 0.2 second SI - Mapped Spectral Response Acceleration Figure 1613.2.1(2) (I) 0.6 (4) G Long Period 1.0 second Fa — Short Period (0.2 second) Site Coefficient Table 1613.2.3(1) (I) 1.0 (4) - F, — Long Period (1.0 second) Site Coefficient Table 1613.2.3(2) (I) null (4) - SMs — NICER Spectral Response Acceleration Parameter Equation 16-36 (I) 1.5 (4) G Adjusted for Site Class Effect 0.2 second SI n - NICER Spectral Response Acceleration Parameter Equation 16-37 (I) null (4) G Adjusted for Site Class Effect 1.0 second SDS - Design Spectral Response Acceleration at 0.2-s Equation 16-38 0) 1.0(4) G SDI - Design Spectral Response Acceleration at 1-s Equation 16-39 (I) null (4) G To = 0.2 SDI/ SDS Section 11.4.6 (2) null (4) S T8= SDI/ SDS Section 11.4.6 (2) null (4) S TL - Long Period Transition Period Figure 22-14 (2) 8 (4) S PGA - Peak Ground Acceleration at MCEG M Figure 22-9 (2) 0.608 (4) G FPGA - Site Coefficient Adjusted for Site Class Effect (2) Table 11.8-1 (2) 1.1 (4) - PGAM —Peak Ground Acceleration (2) Equation 11.8-1 (2) 0.669 (4) G Adjusted for Site Class Effect Design PGA z (2/3 PGAM) - Slope Stability M Similar to Eqs. 16-38 & 16-39 (2) 0.446 G Design PGA z (0.4 SDS) — Short Retaining Walls W Equation 11.4-5 (2) 0.6 G CRS - Short Period Risk Coefficient Figure 22-18A (2) 0.91 (4) - CRI - Long Period Risk Coefficient Figure 22-19A (2) 0.892 (4) - SDC - Seismic Design Category M Section 1613.2.5 (I) null (4) - References: I'I California Building Code (CBC), 2019, California Code of Regulations, Title 24, Part 2, Volume I and II. 2) American Society of Civil Engineers/Structural Engineering Institute (ASCE/SEI), 2016, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, Standards 7-16. 0) USGS Unified Hazard Tool - https:Hearthquake.usas.gov/hazards/interactive/ (4) SEI/OSHPD Seismic Design Map Application — https://seismicmaps.org Related References: Federal Emergency Management Agency (FEMA), 2015, NEHERP (National Earthquake Hazards Reduction Program) Recommended Seismic Provision for New Building and Other Structures FEMA P-1050 . Notes: * PGA Calculated at the MCE return period of 2475 years (2 percent chance of exceedance in 50 years). t PGA Calculated at the Design Level of % of MCE; approximately equivalent to a return period of475 years (10 percent chance of exceedance in 50 years). # PGA Calculated for short, stubby retaining walls with an infinitesimal (zero) fundamental period. § The designation provided herein may be superseded by the structural engineer in accordance with Section 1613.2.5.1, if applicable. I� GE■ O ENCSOLID AS A ROCK RICHMOND AMERICAN HOMES December 20, 2021 Bella at Piazza Serena Project /La Quinta J.N. 21-176 Page 11 Discussion General Owing to the characteristics of the subsurface soils, as defined by Site Class D-Stiff Soil designation, and proximity of the site to the sources of major ground shaking, the site is expected to experience strong ground shaking during its anticipated life span. Under these circumstances, where the code -specified design response spectrum may not adequately characterize site response, the 2019 CBC typically requires a site - specific seismic response analysis to be performed. This requirement is signified/identified by the "null" values that are output using SEA/OSHPD software in determination of short period, but mostly, in determination of long period seismic parameters, see Table 1. For conditions where a "null" value is reported for the site, a variety of design approaches are permitted by 2019 CBC and ASCE 7-16 in lieu of a site -specific seismic hazard analysis. For any specific site, these alternative design approaches, which include Equivalent Lateral Force (ELF) procedure, Modal Response Spectrum Analysis (MRSA) procedure, Linear Response History Analysis (LRHA) procedure and Simplified Design procedure, among other methods, are expected to provide results that may or may not be more economical than those that are obtained if a site -specific seismic hazards analysis is performed. These design approaches and their limitations should be evaluated by the project structural engineer. Seismic Design Category Please note that the Seismic Design Category, SDC, is also designated as "null" in Table 1. For condition where the mapped spectral response acceleration parameter at 1 — second period, S1, is less than 0.75, the 2019 CBC, Section 1613.2.5.1 allows that seismic design category to be determined from Table 1613.2.5(1) alone provided that all 4 requirements concerning fundamental period of structure, story drift, seismic response coefficient, and relative rigidity of the diaphra s are met. Our interpretation of ASCE 7-16 is that for conditions where one or more of these 4 conditions are not met, seismic design category should be assigned based on: 1) 2019 CBC, Table 1613.2.5(1), 2) structure's risk category and 3) the value of SDs, at the discretion of the project structural engineer. Equivalent Lateral Force Method Should the Equivalent Lateral Force (ELF) method be used for seismic design of structural elements, the value of Constant Velocity Domain Transition Period, Ts, is estimated to be 6.8 seconds and the value of Long Period Transition Period, TL, is provided in Table 1 for construction of Seismic Response Coefficient — Period (Cs -T) curve that is used in the ELF procedure. G $ ■ �A SOLID AS A ROCK RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 12 As stated herein, the subject site is considered to be within a Site Class D-Stiff Soil. A site -specific ground motion hazard analysis is not required for structures on Site Class D-Stiff Soil with Si > 0.2 provided that the Seismic Response Coefficient, CS, is determined in accordance with ASCE 7-16, Article 12.8 and structural design is performed in accordance with Equivalent Lateral Force (ELF) procedure. CONCLUSIONS AND RECOMMENDATIONS Site Suitability Based on the current design, as -graded conditions and our current involvement with the project, the proposed residential construction within the site is feasible from a geotechnical standpoint if accomplished in accordance with the City of La Quinta requirements and our following recommendations. Primary Geologic/Geotechnical Considerations Groundwater Previous subsurface data (Sladden, 2001) (ESSW, 2004) reported groundwater was encountered at depths of 25 to 30 feet and 38 feet below the ground surface, respectively; however, ESSW stated that historical groundwater depth may have been as shallow as 5 feet below the ground surface (1961). Historical data from a State well near the southeast corner of Monroe Street and Airport Boulevard reported groundwater at a depth of approximately 15 feet below the ground surface in 1963. Groundwater was not encountered in Petra's recent borings to a maximum depth of 9.5 feet below grade. In the CPT soundings, however, groundwater was encountered a depth of approximately 65 feet. General area groundwater is not anticipated to affect the proposed remedial grading operations; however, contingencies should be planned for cases where localized areas of saturated soils requiring stabilization are encountered. For example, thick vegetations in proximity to the rear of Lots 91 and 93 suggests surface or near surface water seepage from adjacent development. Fault Rupture The site is not located within a currently designated State of California Alquist-Priolo Earthquake Fault Zone (CGS, 2021), nor is it within a Riverside County Fault Zone (County of Riverside, 2003, 2019). In addition, no known active faults have been identified on the site. While fault rupture would most likely occur along previously established fault traces, fault rupture could occur at other locations. However, the potential for active fault rupture at the site is considered to be very low. 1VF%TFA SOLID AS A ROCK GEOSCIENCES- RICHMOND AMERICAN HOMES December 20, 2021 Bella at Piazza Serena Project /La Quinta J.N. 21-176 Page 13 Liquefaction and Seismically Induced Settlement Assessment of liquefaction potential for a particular site requires knowledge of a number of regional as well as site -specific parameters, including the estimated design earthquake magnitude, the distance to the assumed causative fault and the associated probable peak horizontal ground acceleration at the site, subsurface stratigraphy and soil characteristics and groundwater elevation. Parameters such as distance to causative faults and estimated probable peak horizontal ground acceleration can readily be determined using published references, or by utilizing a commercially available computer program specifically designed to perform a probabilistic analysis. Stratigraphy and soil characteristics can only be accurately determined by means of a site -specific subsurface evaluation combined with appropriate laboratory analysis of representative samples of onsite soils. Liquefaction occurs when dynamic loading of a saturated sand or silt causes pore -water pressures to increase to levels where grain -to -grain contact is lost and material temporarily behaves as a viscous fluid. Liquefaction can cause settlement of the ground surface, settlement and tilting of engineered structures, flotation of buoyant buried structures and fissuring of the ground surface. A common manifestation of liquefaction is the formation of sand boils — short-lived fountains of soil and water that emerge from fissures or vents and leave freshly deposited conical mounds of sand or silt on the ground surface. Riverside County identifies the subject property within a zone of liquefaction potential (County of Riverside Mapping Portal, 2019). In view of the depth to groundwater and unconsolidated to consolidated young alluvial wash/fan materials encountered during our field exploration, the potential for manifestation of liquefaction induced features and dynamic settlement is anticipated to be high. Site -Specific Liquefaction Analysis In April 1991, the State of California enacted the Seismic Hazards Mapping Act (Public Resources Code, Division 2, Chapters 7-8). The purpose of the Act is to protect the public safety from the effects of strong ground shaking, liquefaction, landslides, or other ground failure. The Act defines mitigation as "... those measures that are consistent with established practice and reduce seismic risk to acceptable levels." Acceptable level of risk is defined as "that level that provides reasonable protection of the public safety, though it does not necessarily ensure continued structural integrity and functionality of the project [California Code of Regulations; Section 3721 (a)]." In the context of that Act, mitigation of the potential liquefaction hazards at this site to appropriate levels of risk can be accomplished through appropriate foundation and/or subsurface improvement design. OGPET CM SOLID AS A ROCK RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 14 Based on site exploration, this site is considered susceptible to seismic liquefaction. This is due primarily to the documented presence of unconsolidated granular (sandy) soils in the area, the shallow groundwater conditions, and to the proximity of seismic sources. For this reason, a site -specific liquefaction analysis was performed as part of this evaluation. Assessment of liquefaction potential for a particular site requires knowledge of a number of regional as well as site -specific parameters, including the estimated design earthquake magnitude, and the associated probable peak horizontal ground acceleration at the site, subsurface stratigraphy, and soil characteristics. Parameters such as estimated probable peak horizontal ground acceleration can readily be determined using published references, or by utilizing a commercially available computer program specifically designed to perform a probabilistic analysis. On the other hand, stratigraphy and soil characteristics can only be accurately determined by means of a site -specific subsurface investigation combined with appropriate laboratory analysis of representative samples of onsite soils. Propagating earthquake waves induce shearing stresses and strains in soil materials during strong ground shaking. This process rearranges the structure of granular soils such that there is an increase in density, with a corresponding decrease in volume, which results in vertical settlement. Dynamic settlement has been well documented in wet, sandy deposits undergoing liquefaction (see Tokimatsu and Seed, 1987) and in relatively dry sediments as well (Stewart et al, 1996). Specific methods to analyze potential wet and dry dynamic settlement are reported in Tokimatsu and Seed (1987), and specifically dry settlement in Pradel (1998) and Stewart et al. (2001; 2002) respectively. Most of the referenced papers focus on the seismic effects on dry, clean sands of a uniform grain size, though several reports extend the literature to fine- grained soils (Stewart et al., 2001 & 2002). State guidelines for evaluating dynamic settlement are provided in the California Geological Survey Special Publication 117A (CGS, 2008). As noted previously herein, groundwater was observed to be at a depth of 65 feet at the time of field evaluation; however, information provided by Sladden (2001) and ES SW (2004) reported that groundwater was encountered at depths of 25 to 30 feet and 38 feet below the ground surface, respectively; however, ESSW stated that historical groundwater depth may have been as shallow as 5 feet below the ground surface in 1961. More accurately, historical data from a State well near the southeast corner of Monroe Street and Airport Boulevard reported groundwater at a depth of approximately 10 to 15 feet below the ground surface in 1963 (CVWD, 2013). We have used a conservative value of 10 feet for our liquefaction analysis (Appendix Q. 10 PE I FU SOLID AS A ROCK GEOSCIENCES- RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta Analyses Using CPT Sounding Results December 20, 2021 J.N. 21-176 Page 15 We performed four CPT soundings at the site for use in the liquefaction analysis. Our analysis using the CPT data provides continuous penetration resistance data rather than borehole data using SPT sampling that must be averaged over discrete sampling increments (e.g., 5 or 10 feet). A variety of computer programs are available that were developed specifically for liquefaction and seismic settlement analyses. For purposes of this study, we selected the commercially available software program CLiq Version 3.3.1.14 (GeoLogismiki, 2021) that implements updated versions of the NCEER procedure as recommended by Dr. Peter Robertson (2010), or that of Professors Idriss and Boulanger (2008, 2014). The procedures were based on the methods originally recommended by Seed and Idriss (1982). Analysis Results and Assessment of Liquefaction Effects Section 1803.5.12.3 of the 2019 CBC requires the "assessment of potential consequences of liquefaction and soil strength loss, including, but not limited to" the following items, which we will discuss in the order that they appear in the code. 2019 CBC Section 1803.5.12.3 — 3.1— Estimation of total and differential settlement; Analyses with historic high groundwater estimated at 10 feet below the ground surface indicated that the major potentially liquefiable zones are from approximately 10 to 60 feet below the ground surface in CPT- 1 thru CPT-3. A factor of safety of 1.3 was used in our analysis in accordance with the procedures of CGS publication SP 117A. To determine the estimated seismically induced settlement from the CPT soundings we used the Robertson (2009) modifications to the NCEER procedure to estimate the free field settlement. Tabulated results of the estimated settlement for this analysis method are shown in Table 2 below. The results of the other methods are shown on the summary comparison plot printouts. Please note, total seismic settlement is based on the depth of our evaluation at each location. TABLE 2 Seismically Induced Settlement Boring No. Total Dry Sand Settlement (in.) Total Liquefaction Settlement (in.) Total Seismic Induced Settlement (in.) CPT-1 Negligible 3 '/2 3 '/2 CPT-2 Negligible 4 '/4 4 '/4 CPT-3 Negligible 2 '/4 2 '/4 0 GE■�G ENC� SOLID AS A ROCK RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 16 Based on our calculations, total seismically induced settlement at the three CPT locations is not considered excessive in accordance with guidelines provided in the California Geotechnical Survey Special Publication 117A (CGA, 2008). Because of the potential of differential settlement resulting from soil liquefaction, preliminary recommendations for one- and two-story residential structures may include using post -tensioned tendons designed to accommodate the estimated differential settlement of less than 2 inch in a 40-foot span. The minimum goal of liquefaction mitigation should be to provide a foundation system that can withstand the expected movement without causing such structural damage so as to pose a life -safety hazard (such as structural collapse from excessive drift). The conclusions expressed herein are reached based on sparsely located CPT soundings and, to a lesser extent, on conventional boring data. Soil Strength Loss The results of our analysis show that subsurface soils are not subject to significant strength loss during a strong seismic event. As a result, the post -liquefaction bearing capacity for shallow foundation elements will not be significantly reduced from the static condition. Surface Manifestation of Liquefaction Based on the method outlined by Ishihara (1985) and considering the depth of the shallow liquefiable layers identified by the results of CPT soundings (approximately 15 to 40 feet below the existing ground surface), the overall depth of underlying liquefiable layers, the thickness of the non -liquefiable layers above the upper liquefiable zone may not be sufficient to prevent surface manifestation of liquefaction, such as sand boil and loss of bearing. Further, structures that enclose a void space such as pipelines, manholes, or buried vaults may be subject to buoyant forces if they are located within layers below 10± feet from the ground surface where we noted that liquefaction was likely to occur for this site. Such structures may need to be anchored if they are not located within areas mitigated by remedial grading. Geotechnical Issues Not Related to Seismicity Subsidence Subsidence is the settlement or deformation of the land surface caused by several different conditions (including tectonic activity and petroleum production); however, it is most commonly associated with changes in groundwater levels. Long-term withdrawal of groundwater around the subject site has lowered the water table considerably, and this has resulted in 50 or more feet of subsidence in some areas of the Coachella Valley (Sneed, Brandt and Solt, 2014). Although partial recovery of the settlement may be 11M I SOLID AS A ROCK RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 17 possible if the water table is recharged and if the vertical stress increases induced at the groundwater low point were not generally higher than the past pressure, most subsidence is not recoverable when the stress has increased beyond the highest past pressure. According to Chapter 6.0 of the County of Riverside General Plan (Riverside County, 2008), the subject site lies within an area that is susceptible to subsidence. Policy 5-3.8 of Chapter 6.0 requires that a geotechnical evaluation of subsidence be performed if a site lies within a documented subsidence area, or an area that is susceptible to subsidence as shown on Figure S-7 of that document. As stated in the plan, "differential displacement and fissures occur at or near the valley margin, and along faults. In the County of Riverside, the worst damage to structures, because of regional subsidence, may be expected at the valley margins. " We note the following findings in relation to our assessment of the subsidence hazard at the site: • The subject property lies within the La Quinta Subsidence Area (Sneed, Brandt and Solt, 2014). The Area is the southernmost of three subsidence area, namely the Palm Desert, Indian Wells, and La Quinta. • The site does lie in proximity to the valley margin where differential ground subsidence from groundwater extraction could be magnified. Based on our review of published USGS reports, the site appears to lie near the southerly edge of a section of documented subsidence. Current studies (Sneed, Brandt and Solt, 2014) suggest the site vicinity to be in an area of previous, highly extensive, documented subsidence. • The site does lie within subsidence areas as documented by Riverside County (2008; 2014) and Sneed, Brandt and Solt (2014); therefore, the probability of subsidence due to groundwater extraction is judged to be high for the subject site. • The most rapidly subsiding portion of the La Quinta Subsidence Area is approximately bounded by Avenue 48 (if extended westward) on the north, Avenue 60 (if extended westward) on the south, the Santa Rosa Mountains on the west, and streets varying from Jefferson Street to Monroe Street on the east. Time -series plots of subsidence at four of the five selected golf course sites within the La Quinta Subsidence Area indicated subsidence ranged from about 1.53 feet to about 1.97 feet from June 27, 1995 to September 19, 2010 (Sneed, Brandt and Solt, 2014). At two time -series locations in general proximity to the subject property (one on the order of 2 miles to the northwest and one on the order of 1.5 miles to the southwest), subsidence rates were fairly steady at about 0.13 and 0.06 foot per year (ft./yr.), respectively. Subsidence rates slowed to about 0.04 ft./yr. at the location northwest of the subject property during mid 2009 through 2010. The site located southwest of the subject property showed uplift at a rate of about 0.05 ft./yr. during this same period (Sneed, Brandt and Solt, 2014). F%-TFA SOLID AS A ROCK GEOSCIENCES- RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 18 Water levels measured in the late 2000's in many wells in the La Quinta Area were at the lowest recorded historic levels; however, water levels in and near the La Quinta Area stabilized in mid- 2008 and recovered. Stabilization and recovery of water levels coincided with increased Colorado River water deliveries to the Thomas E. Levy Recharge Facility. Concomitant subsidence and declining water levels within the Area during 1993 to 2010, and reduced subsidence rates and recovering water levels in the La Quinta Areas in 2009 to 2010, indicated that aquifer -system compaction could be causing subsidence (Sneed, Brandt and Solt, 2014). Petra more recently conducted a cursory review of an update subsidence report for the Coachella Valley for 2010 through 2017 (Sneed and Brandt, 2020). The maximum subsidence in the La Quinta Area during December 2014 through June 2017 was about 0.26 feet at several areas. The most rapidly subsiding part of the La Quinta Subsidence Area is generally bounded by Avenue 48 on the north, Avenue 58 on the south, Santa Rosa mountains on the west, and Monroe Street on the east. The subject property, located at the northwest corner of Monroe Street and Avenue 58, lies within the southeastern corner of this area. Using the same two time -series locations in general proximity to the subject property, subsidence rates from the northwest location decreased from as much as 0.13 ft./yr. to less than 0.04 ft./yr. from 1995-2010 to 2014-2017. Subsidence rates at the southwest location decreased from as much as 0.05 ft./yr. to about 0.01 ft./yr. from 1995-2010 to 2014-2017 (Sneed and Brandt, 2020). Based on the above information, although additional settlement at the site from subsidence should be expected, we are not aware of any currently available methods of determining the magnitude or time frame within such deformation may occur. Compressible Soils Compressible soils do not appear to be a primary geotechnical factor affecting the project site; however, surface soils are weathered, and localized soil piles have been dumped on the subject property. Surface soils will require removal and recompaction to a depth of 1 foot below existing grades. Soil piles will require reprocessing prior to placement s fill as needed. EARTHWORK RECOMMENDATIONS General Earthwork Recommendations Earthwork should be performed in accordance with the Grading Code of the County of Riverside, in addition to the applicable provisions of the 2019 CBC. Grading should also be performed in accordance with the following site -specific recommendations prepared by Petra based on the proposed construction. Standard Grading Specification are presented in Appendix E. II �� SOLID AS A ROCK GEOSCIENCES"° RICHMOND AMERICAN HOMES December 20, 2021 Bella at Piazza Serena Project /La Quinta J.N. 21-176 Page 19 Geotechnical Observations and Testing Prior to the start of earthwork, a meeting should be held at the site with the owner, contractor, and geotechnical consultant to discuss the work schedule and geotechnical aspects of the grading. Earthwork, which in this instance will generally entail removal and re -compaction of the near surface soils, should be accomplished under full-time observation and testing of the geotechnical consultant. A representative of the project geotechnical consultant should be present onsite during all earthwork operations to document proper placement and compaction of fills, as well as to document compliance with the other recommendations presented herein. Clearing and Grubbing All existing weeds, grasses, brush, shrubs, trees, and similar vegetation existing within areas to be graded should be stripped and removed from the site. Clearing operations should also include the demolition and removal of all existing improvements (irrigation lines, valve risers, concrete water distribution boxes, light posts, wind machines, trailers, barns/sheds, etc.), any remaining trash, debris, vegetation, and similar deleterious materials. Any cavities or excavations created upon removal of structures or existing trees (i.e., root ball) or any unknown subsurface structure(s) should be cleared of loose soil, shaped to provide access for backfilling and compaction equipment and then backfilled with properly compacted fill. Note that deleterious materials may be encountered within the site and may need to be removed by hand, i.e., root pickers, during the grading operations. The project geotechnical consultant should provide periodic observation and testing services during clearing and grubbing operations to document compliance with the above recommendations. In addition, should unusual or adverse soil conditions or buried structures be encountered during grading that are not described herein, these conditions should be brought to the immediate attention of the project geotechnical consultant for corrective recommendations. Building Pad Preparation and Precise Grading Approximately 15 years has elapsed since rough grading of the subject building pads was completed. The building pads generally have a light to heavy amount of vegetation growth and minimal scattered trash and debris. All vegetation, debris, trash etc. should be cleared and hauled offsite. Voids created by removal of large bushes and trees shall be cleaned of loose soil and the backfll compacted to at least 90 percent relative density per ASTM D 1557. *FWTFA SOLID AS A ROCK GEOSCIENCES- RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 20 During our fieldwork, we observed that the upper 2 to 3f feet of building pad soils were very dry to dry. All building pad areas will require surficial remedial grading to establish drainage and re-establish moisture conditions. Due to the depth of erosion, utility trench failures, and occasional piping features of near surface fill soils, prior to each phase of precise grading, the building pad soils should be over excavated to a depth of 12 inches and the exposed bottom surface scarified to a depth of 10- to 12-inches and thoroughly moisture condition to at least 2 percent above optimum moisture content. The re -processed bottom should then be re -compacted in -place to at least 90 percent, and then compacted fill placement of soils at least two percent above optimum moisture content to finish grades. Large brush and tree root removal will require deeper excavation to accommodate voids. The City may ask for formal recertification letters during each phase of lot precise grading. Minor cuts for pad driveways are expected, as well as well as minor cuts and/or fills for sidewalks behind curb and gutter. Soils within the building pad areas and slopes have been slightly to heavily eroded with the passage of time. Therefore, remedial grading will be required to reprocess all disturbed, desiccated and eroded surficial soils and create suitable pads for the construction of the proposed improvements. That is, following clearing/grubbing operations, the near surface soils, where desiccated, should be scarified to a depth of at least 8 to 10 inches, thoroughly moisture -conditioned to near two percent above optimum and then recompacted in -place to a minimum relative compaction of 90 percent based on ASTM D 1557. It is recommended that the deeper erosional gullies (i.e., those deeper than 8 inches) that would not be eliminated during pad and slope restoration should be widened as necessary to provide equipment access, cleared of all loose soil and/or desiccated soil material and debris, and backfilled with properly moisture - conditioned onsite soils and compacted to a minimum relative compaction of 90 percent. Following the remedial grading, the site may be brought to proposed finish elevation and proper surface drainage may be established. A representative of the project geotechnical consultant should be present during clearing, remedial grading and backfill operations. It should be noted that the sequence of precise grading, as recommended above, is left to grading contractor's discretion. However, our experience indicates that for conditions where site surficial soils exist at a moisture content well below optimum, the grading operation may be performed more efficiently if the soils are thoroughly moisture conditioned utilizing a temporary sprinkler system prior to scarification and recompaction. Exposed bottom surfaces areas to receive compacted fill should be observed and approved by the project geotechnical consultant prior to fill placement. No fill should be placed without prior approval from the 1* FWTFA SOLID AS A ROCK GEOSCIENCES- RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 21 geotechnical consultant. The project geotechnical consultant should also be present on -site during grading operations to document proper placement and adequate compaction of fill, as well as to observe compliance with the other recommendations presented herein. Precise Grading and Drainage Surface and subsurface drainage systems consisting of sloping concrete flatwork, drainage swales and side and front yard subsurface area drains will be constructed on the subject lots to collect and direct all surface water to the adjacent streets. In addition, the ground surface around the proposed buildings should be sloped to provide a positive drainage gradient away from the structures. The purpose of the drainage systems is to prevent ponding of surface water within the level areas of the site and against building foundations and associated site improvements. The drainage systems should be properly maintained throughout the life of the proposed development. Section 1804.3 of the 2019 CBC requires that "The ground immediately adjacent to the foundation shall be sloped away from the building at a slope of not less than one unit vertical in 20 units horizontal (5-percent slope) for a minimum distance of 10 feet (3048 mm) measured perpendicular to the face of the wall." Further, "Swales used for this purpose shall be sloped a minimum of 2 percent, where located within 10 feet (3048 mm) of the building foundation". These provisions fall under the purview of the Design Civil Engineer. However, exceptions to allow modifications to these criteria are provided within the same section of the Code as "Where climatic or soil conditions warrant, the slope of the ground away from the building foundations is permitted to be reduced to not less than one unit in 48 units horizontal (2-percent slope)." This exemption provision appears to fall under the purview of the Geotechnical Engineer -of -Record. It is our understanding that the state -of -the -practice for projects in various cities and unincorporated areas of Riverside County, as well as throughout Southern California, has been to construct earthen slopes at 2 percent minimum gradient away from the foundations and at 1 percent minimum for earthen swale gradients. Structures constructed and properly maintained under those criteria have performed satisfactorily. Therefore, considering the semi -arid climate, site soil conditions and an appropriate irrigation regime, Petra considers that the implementation of 2 percent slopes away from the structures and 1 percent swales to be acceptable for the subject lots. It should be emphasized that the homeowners are cautioned that the slopes away from the structures and swales to be properly maintained, not to be obstructed, and that future improvements not to alter established I�V ROETFM GECSOLID AS A ROCK RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 22 gradients unless replaced with suitable alternative drainage systems. Further, where the flow line of the swale exists within five feet of the structure, adjacent footings shall be deepened appropriately to maintain minimum embedment requirements, measured from the flow line of the swale. Suitability of Site Soils as Fill Site soils are suitable for use in engineered fills provided they are clean from organics and/or debris. Wet alluvial soils may also be encountered during site grading (depending upon the time of year grading occurs) and may require drying back before being reused as fill. Oversize rock, that exceeding 12 inches, should be excluded from placement in the upper seven feet of the building pads. Fill Placement Fill materials should be placed in approximately 6- to 8-inch-thick loose lifts, watered or air-dried as necessary to achieve a moisture content approximately 2 percent above optimum moisture condition, and then compacted in -place to no less than 90 percent relative compaction. The laboratory maximum dry density and optimum moisture content for each major soil type should be determined in accordance with ASTM D 1557. Import Soils for Grading Although not anticipated, if import soils are needed to achieve final design grades, import soils should be free of deleterious materials, oversize rock, and any hazardous materials. The soils should also be non - expansive and essentially non -corrosive and approved by the project geotechnical consultant prior to being brought onsite. The geotechnical consultant should inspect the potential borrow site and conduct testing of the soil at least three days before the commencement of import operations. FOUNDATION DESIGN RECOMMENDATIONS Expansive Soil Conditions Limited testing by this office found soils within the subject tract indicated a very low to low to expansion potential. Due to the sporadic nature of the expansion tests, we recommend designing all lots for low EI category. If desired, additional sampling and testing of pad grade soils during future precise grading could be performed to determine which lots exhibit very low expansion potential versus low expansion potential. 7& FETFA SOLID AS A ROCK GEOSCIENCES- RICHMOND AMERICAN HOMES December 20, 2021 Bella at Piazza Serena Project /La Quinta J.N. 21-176 Page 23 Allowable Soil Bearim Capacity A basic allowable soil bearing capacity of 1,500 pounds per square foot, including dead and live loads, may be utilized for design of 24-inch square pad footing and 12-inch-wide continuous footings founded at a minimum depth of 12 inches below the lowest adjacent final grade. This value may be increased by 20 percent for each additional foot of depth and by 10 percent for each additional foot of width to a maximum value of 2,500 pounds per square foot. Recommended allowable bearing values include both dead and live loads and may be increased by one-third for short duration wind and seismic forces. Lateral Resistance A passive earth pressure of 250 pounds per square foot per foot of depth, to a maximum value of 2,500 pounds per square foot, may be used to determine lateral bearing resistance for footings. In addition, a coefficient of friction of 0.30 times the dead load forces may be used between concrete and the supporting soils to determine lateral sliding resistance. The above values may be increased by one-third when designing for transient wind or seismic forces. It should be noted that the above values are based on the condition where footings are cast in direct contact with compacted fill or competent native soils. In cases where the footing sides are formed, all backfill placed against the footings upon removal of forms should be compacted to at least 90 percent of the applicable maximum dry density. Footing Settlement Static — Based on the allowable bearing values provided above, total static settlement of the footings is anticipated to be less than 1 inch. Differential settlement is expected to be less than 0.5 inch over a horizontal span of 40 feet. Most of the settlement is likely to take place as footing loads are applied or shortly thereafter. Dynamic — Utilizing cone penetration test (CPT) data, a detailed analysis of liquefaction potential was conducted as a part of Petra's previous evaluation (Petra, 2021b). The calculated dynamic settlement at the three CPT sounding locations ranged from 21/4 to 41/4 inches. The total seismically induced settlement at the three locations is not considered excessive in accordance with guidelines provided in the California Geotechnical Survey Special Publication 117A (CGA, 2008). Because of the potential of differential settlement resulting from soil liquefaction, post -tensioned foundations are recommended tendons designed to accommodate the estimated differential dynamic settlement of 2 inches over a 40-foot span. It should be noted that the minimum goal of liquefaction mitigation should be to provide a foundation system that can withstand the expected movement without *FWTFA SOLID AS A ROCK GEOSCIENCES- RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 24 causing such structural damage so as to pose a life -safety hazard (such as structural collapse from excessive drift). Post -Tensioned Slab -on -Ground System In view of the high potential for liquefaction at the site, Petra recommends utilizing the parameters for Low expansion potential as a minimum to better accommodate potential dynamic settlement. Should the design engineer choose to follow the most current procedure published by the Post -Tensioning Institute (PTI DC10.5-12), the following minimum design criteria are provided in the following table. TABLE 3 Presumptive Post -Tensioned Slab -on -Ground Design Parameters for PTI Procedure Soil Information Approximate Depth of Constant Suction, feet 9 Approximate Soil Suction, pF 3.9 Inferred Thornthwaite Index: -20 Average Edge Moisture Variation Distance, em in feet: Center Lift 9.0 Ed e Lift 4.7 Anticipated Swell, ym in inches: Center Lift 0.35 Edge Lift 0.65 Modulus of Subgrade Reaction The modulus of subgrade reaction for design of load bearing elements depends on the size of the element and soil -structure interaction. However, as a first level of approximation, this value may be assumed to be 125 pounds per cubic inch. Minimum Design Recommendations The soil values provided above may be utilized by the project structural engineer to design post -tensioned slabs on -ground in accordance with Section 1808.6.2 of the 2019 CBC and the PTI publication. Thicker floor slabs and larger footing sizes may be required for structural reasons and should govern the design if more restrictive than the minimum recommendations provided below: 1. Exterior continuous footings for one- and two-story structures should be founded at a minimum depth of 18 inches below the lowest adjacent finished ground surface. Interior footings may be founded at a minimum depth of 12 inches below the tops of the finish floor slabs. II �� SOLID AS A ROCK GEOSCIENCES"° RICHMOND AMERICAN HOMES December 20, 2021 Bella at Piazza Serena Project /La Quinta J.N. 21-176 Page 25 2. In accordance with Table 1809.7 of 2019 CBC for light -frame construction, all continuous footings should have minimum width of 12 inches for one- and two-story construction. We recommend all continuous footings should be reinforced with a minimum of two No. 4 bars, one top and one bottom. Alternatively, post -tensioned tendons may be utilized in the perimeter continuous footings in lieu of the reinforcement bars. 3. A minimum 12-inch-wide grade beam founded at the same depth as adjacent footings should be provided across the garage entrances or similar openings (such as large doors or bay windows). The grade beam should be reinforced in a similar manner as provided above. 4. Interior isolated pad footings, if required, should be a minimum of 24 inches square and founded at a minimum depth of 12 inches below the bottoms of the adjacent floor slabs. Pad footings should be reinforced with No. 4 bars spaced a maximum of 18 inches on centers, both ways, placed near the bottoms of the footings. Exterior isolated pad footings intended for support of roof overhangs such as second -story decks, patio covers, and similar construction should be a minimum of 24 inches square and founded at a minimum depth of 18 inches below the lowest adjacent final grade. The pad footings should be reinforced with No. 4 bars spaced a maximum of 18 inches on centers, both ways, placed near the bottoms of the footings. Exterior isolated pad footings may need to be connected to adjacent pad and/or continuous footings via tie beams at the discretion of the project structural engineer. 6. The thickness of the floor slabs should be determined by the project structural engineer with consideration given to the expansion potential of the on -site soils; however, we recommend that a minimum slab thickness of 4 inches be considered. As an alternative to designing 4-inch-thick post -tensioned slabs with perimeter footings as described in Items 1 and 2 above, the structural engineer may design the foundation system using a thickened slab design. The minimum thickness of this uniformly thick slab should be 8 inches. The engineer in charge of post -tensioned slab design may also opt to use any combination of slab thickness and footing embedment depth as deemed appropriate based on their engineering experience and judgment. Living area concrete floor slabs and areas to receive moisture sensitive floor covering should be underlain with a moisture vapor retarder consisting of a minimum 10-mil-thick polyethylene or polyolefin membrane that meets the minimum requirements of ASTM E96 and ASTM E 1745 for vapor retarders (such as Husky Yellow Guard®, Stego(& Wrap, or equivalent). All laps within the membrane should be sealed, and at least 2 inches of clean sand should be placed over the membrane to promote uniform curing of the concrete. To reduce the potential for punctures, the membrane should be placed on a pad surface that has been graded smooth without any sharp protrusions. If a smooth surface cannot be achieved by grading, consideration should be given to lowering the pad finished grade an additional inch and then placing a 1-inch-thick leveling course of sand across the pad surface prior to the placement of the membrane. At the present time, some slab designers, geotechnical professionals, and concrete experts view the sand layer below the slab (blotting sand) as a place for entrapment of excess moisture that could adversely impact moisture -sensitive floor coverings. As a preventive measure, the potential for moisture intrusion into the concrete slab could be reduced if the concrete is placed directly on the vapor retarder. However, if this sand layer is omitted, appropriate curing methods must be implemented to ensure that the concrete slab cures OPETMSOLID AS A ROCK RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 26 uniformly. A qualified materials engineer with experience in slab design and construction should provide recommendations for alternative methods of curing and supervise the construction process to ensure uniform slab curing. Additional steps would also need to be taken to prevent puncturing of the vapor retarder during concrete placement. 9. Garage floor slabs should be reinforced in a similar manner as living area floor slabs. Consideration should be given to placement of a moisture vapor retarder below the garage slab, similar to that provided in Item 6 above, should the garage slab be overlain with moisture sensitive floor covering. 10. Presaturation of the subgrade below floor slabs will not be required; however, prior to placing concrete, the subgrade below all dwelling and garage floor slab areas should be thoroughly moistened to achieve a moisture content that is at least equal to or slightly greater than optimum moisture content to a minimum depth of 12 inches below the bottoms of the slabs. 11. The minimum dimensions provided herein may be modified (increased or decreased subject to the constraints of Chapter 18 of the 2019 CBC and PTI DC 10.5) by the structural engineer responsible for foundation design based on his/her calculations, engineering experience and judgment. General Corrosivity Screening As a screening level study, limited chemical and electrical tests were performed on samples considered representative of the onsite soils to identify potential corrosive characteristics of these soils. The common indicators associated with soil corrosivity include water-soluble sulfate and chloride levels, pH (a measure of acidity), and minimum electrical resistivity. It should be noted that Petra does not practice corrosion engineering; therefore, the test results, opinion and engineering judgment provided herein should be considered as general guidelines only. Additional analyses would be warranted, especially, for cases where buried metallic building materials (such as copper and cast or ductile iron pipes) in contact with site soils are planned for the project. In many cases, the project geotechnical engineer may not be informed of these choices. Therefore, for conditions where such elements are considered, we recommend that other, relevant project design professionals (e.g., the architect, landscape architect, civil and/or structural engineer) also consider recommending a qualified corrosion engineer to conduct additional sampling and testing of near -surface soils during the final stages of site grading to provide a complete assessment of soil corrosivity. Recommendations to mitigate the detrimental effects of corrosive soils on buried metallic and other building materials that may be exposed to corrosive soils should be provided by the corrosion engineer as deemed appropriate. In general, a soil's water-soluble sulfate levels and pH relate to the potential for concrete degradation; water-soluble chlorides in soils impact ferrous metals embedded or encased in concrete, e.g., reinforcing steel; and electrical resistivity is a measure of a soil's corrosion potential to a variety of buried metals used in the building industry, such as copper tubing and cast or ductile iron pipes. Table 4, below, presents the 1* F%1FM SOLID AS A ROCK GEOSCIENCESm RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 27 range of each category of individual test results with an interpretation of current code indicators and guidelines that are commonly used in this industry. The table includes the code -related classifications of the soils as they relate to the various tests, as well as a general recommendation for possible mitigation measures in view of the potential adverse impact on various components of the proposed structures in direct contact with site soils. The guidelines provided herein should be evaluated and confirmed, or modified, in their entirety by the project structural engineer, corrosion engineer and/or the contractor responsible for concrete placement for structural concrete used in exterior and interior footings, interior slabs on -ground, garage slabs, wall foundations and concrete exposed to weather such as driveways, patios, porches, walkways, ramps, steps, curbs, etc. TABLE 4 Soil Corrosivity Screening Results Test Test Results Classification General Recommendations 0.0855 percent So' Type II cement; min. f c= 2,500 psi; no water/cement Soluble ratio restrictions Type II cement; Maximum water/cement ratio of the fresh Sulfates (Cal 417) 0.1140 percent Sly) - Moderate concrete should not exceed 0.50, f,�'(2) should not be less than 4,000 psi. pH (Cal 643) 8.1 and 8.15 Moderately No special recommendations 908 and 1,320 CV) - Moderate Residence: Increase concrete cover thickness; f�1(2) should not Soluble ppm be less than 2,500 psi. Consult a corrosion engineer Chloride 908 and 1,320 Pools/Decking: Increase concrete cover thickness; Maximum (Cal 422) C2(4)- Severe water/cement ratio of the fresh concrete should not exceed ppm 0.40; f�1(2) should not be less than 5,000 psi. Resistivity 240 and 360 Extremely Consult a corrosion engineer (Cal 643) 1 ohm -cm I Corrosive(5) Notes: 1. ACI 318-14, Section 19.3 2. ACI 318-14, Section 19.3 3. Pierre R. Roberge, "Handbook of Corrosion Engineering" Post -Grading Considerations Utility Trench Backfill All utility trench backfill should be compacted to a minimum relative compaction of 90 percent. Trench backfill materials should be placed in maximum lifts approximately 8- to 12-inch thick, moisture conditioned as necessary to achieve slightly above optimum moisture conditions, and mechanically compacted in place with a hydra -hammer, pneumatic tamper, or similar equipment to achieve a minimum 10 FSTFA SOLID AS A ROCK GEOSCIENCES— RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 28 relative compaction of 90 percent. A representative of this firm should probe and test the backfills to document the adequate compaction has been achieved. For shallow trenches where pipe or utilities might be damaged by mechanical compaction equipment, imported sand having a Sand Equivalent (SE) value of 30 or greater may be used for backfilling. Sand backfill materials should be watered to achieve above optimum moisture conditions, and then tamped with hand -operated pneumatic tampers to ensure proper consolidation of the backfill. No specific relative compaction will be required; however, observation, probing and, if deemed necessary, testing should be performed by a representative of this firm to verify that the backfill is adequately compacted and will not be subject to excessive settlement. Where an exterior or interior utility trench is proposed in a direction that is parallel to a building footing, the bottom of the trench should not extend below a 1:1 plane projected downward from the bottom edge of the adjacent footing. Where this condition occurs, the adjacent footing should be deepened, or the trench backfilled and compacted prior to construction of the footing. Masonry Block Screen Walls Due to the minor potential for surface manifestation of liquefaction, we recommend footings for appurtenant structures, such as property line walls, trash enclosure walls, barbeque stands, etc., should be designed for an allowable bearing capacity of 1,000 ps£ Footings for masonry block walls may be designed in accordance with the lateral resistance values provided previously for building footings. However, as a minimum, the wall footings should be embedded at a minimum depth of 18 inches below the lowest adjacent final grade. The footings should also be reinforced with a minimum of four No. 4 bars, two near top and two near bottom. In order to minimize the potential for unsightly cracking related to the possible effects of differential settlement and/or expansion, positive separations (construction joints) should also be provided in the block walls at each corner and at horizontal intervals of approximately 20 to 25 feet. The separations should be provided in the blocks and not extend through the footings. The footings should be poured monolithically with continuous reinforcement bars to serve as effective "grade beams" below the walls. Exterior Concrete Flatwork General Near -surface compacted fill soils within the site are variable in expansion behavior and are expected to exhibit low expansion potential. Due to typical project scheduling constraints, it may not be feasible to 10 PE I FM SOLID AS A ROCK GEOSCIENCES- RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 29 collect additional samples of subgrade soils for testing to verify their expansion potential immediately prior to pouring concrete. For this reason, we recommend that all exterior concrete flatwork such as sidewalks, patio slabs, large decorative slabs, concrete subslabs that will be covered with decorative pavers, private and/or public vehicular driveways and/or access roads within and adjacent to the site be designed by the project architect and/or structural engineer with consideration given to mitigating the potential cracking and uplift that can develop in soils exhibiting expansion index values that fall in the medium category. The guidelines that follow should be considered as minimums and are subject to review and revision by the project architect, structural engineer and/or landscape consultant as deemed appropriate. If sufficient time will be allowed in the project schedule for verification sampling and testing prior to the concrete pour, the test results generated may dictate that a somewhat less conservative design could be used. Thickness and Joint Spacing To reduce the potential of unsightly cracking, concrete walkways, patio -type slabs, large decorative slabs and concrete subslabs to be covered with decorative pavers should be at least 4 inches thick and provided with construction joints or expansion joints every 6 feet or less. Private driveways that will be designed for the use of passenger cars for access to private garages should also be at least 4 inches thick and provided with construction joints or expansion joints every 10 feet or less. Concrete pavement that will be designed based on an unlimited number of applications of an 18-kip single -axle load in public access areas or segments of road that will be paved with concrete (such as bus stops and cross -walks) or access roads and driveways, which serve multiple residential units or garages, that will be subject to heavy truck loadings should have a minimum thickness of 5 inches and be provided with control joints spaced at maximum 10- foot intervals. A modulus of subgrade reaction of 100 pounds per cubic foot may be used for design of the public and access roads. Reinforcement All concrete walkways, patio -type slabs, large decorative slabs, concrete subslabs to be covered with decorative pavers and private driveways that will be designed for the use of passenger cars for access to private garages should be reinforced with a minimum of No. 3 bars spaced 24 inches on centers, both ways. Alternatively, the slab reinforcement may consist of welded wire mesh of the sheet type (not rolled) with 6x6/W1.4xW1.4 designation in accordance with the Wire Reinforcement Institute (WRI). Concrete pavement that will be designed based on an unlimited number of applications of an 18-kip single -axle load in public access areas, segments of road that will be paved with concrete (such as bus stops and crosswalks) or access roads that will be subject to heavy truck loadings should be reinforced with a minimum of No. 3 GEO I SOLID AS A ROCK RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta December 20, 2021 J.N. 21-176 Page 30 bars spaced 18 inches on centers, both ways. Alternatively, the slab reinforcement may consist of welded wire mesh of the sheet type with 6x6/W2.9xW2.9 designation in accordance with the Wire Reinforcement Institute (WRI). The reinforcement should be properly positioned near the middle of the slabs. The reinforcement recommendations provided herein are intended as guidelines to achieve adequate performance for anticipated soil conditions. The project architect, civil and/or structural engineer should make appropriate adjustments in reinforcement type, size and spacing to account for concrete internal (e.g., shrinkage and thermal) and external (e.g., applied loads) forces as deemed necessary. Edge Beams (Optional) Where the outer edges of concrete flatwork are to be bordered by landscaping, it is recommended that consideration be given to the use of edge beams (thickened edges) to prevent excessive infiltration and accumulation of water under the slabs. Edge beams, if used, should be 6 to 8 inches wide, extend 8 inches below the tops of the finish slab surfaces. Edge beams are not mandatory; however, their inclusion in flatwork construction adjacent to landscaped areas is intended to reduce the potential for vertical and horizontal movement and subsequent cracking of the flatwork related to uplift forces that can develop in expansive soils. Subuade Preparation Compaction To reduce the potential for distress to concrete flatwork, the subgrade soils below concrete flatwork areas to a minimum depth of 15 inches (or deeper, as either prescribed elsewhere in this report or determined in the field) should be moisture conditioned to at least equal to, or slightly greater than, the optimum moisture content and then compacted to a minimum relative compaction of 90 percent. Where concrete public roads, concrete segments of roads and/or concrete access driveways are proposed, the upper 6 inches of subgrade soil should be compacted to a minimum 95 percent relative compaction. Pre -Moistening As a further measure to reduce the potential for concrete flatwork cracking, subgrade soils should be thoroughly moistened prior to placing concrete. The moisture content of the soils should be at least 1.2 times the optimum moisture content and penetrate to a minimum depth of 15 inches into the subgrade. Flooding or ponding of the subgrade is not considered feasible to achieve the above moisture conditions since this method would likely require construction of numerous earth berms to contain the water. 10 PETFA SOLID AS A ROCK GEOSCIENCES- RICHMOND AMERICAN HOMES December 20, 2021 Bella at Piazza Serena Project /La Quinta J.N. 21-176 Page 31 Therefore, moisture conditioning should be achieved with sprinklers, or a light spray applied to the subgrade over a period of few to several days just prior to pouring concrete. Pre -watering of the soils is intended to promote uniform curing of the concrete, reduce the development of shrinkage cracks, and reduce the potential for differential expansion pressure on freshly poured flatwork. A representative of the project geotechnical consultant should observe and verify the density and moisture content of the soils, and the depth of moisture penetration prior to pouring concrete. Drainage Drainage from patios and other flatwork areas should be directed to local area drains and/or graded earth swales designed to carry runoff water to the adjacent streets or other approved drainage structures. The concrete flatwork should be sloped at a minimum gradient of one percent, or as prescribed by project civil engineer or local codes, away from building foundations, retaining walls, masonry garden walls and slope areas. Tree Wells Tree wells are not recommended in concrete flatwork areas since they introduce excessive water into the subgrade soils and allow root invasion, both of which can cause heaving and cracking of the flatwork. Final Pavement Improvements The existing private streets, at least 15 years old, were observed to have random linear cracking and cracking that appeared to be along utility trenches, including two water valve cans and a manhole on Vida Bella Drive. No alligator cracking, indicating pavement failure, was observed. Vegetation growth is also common within pavement cracks. In a desert environment, thermal asphalt cracking is not uncommon especially on untraveled streets. Settlement around sewer manholes and water values should be excavated and repaired. In Vida Bella Drive, settlement around existing utility repair patches, will require further evaluation. A large scar behind the curb on Lots 43/44 was likely created by piping along a utility conduit, which may affect adjacent lots and possibly street laterals. In most cases, we recommend crack sealing with a bituminous, or comparable, material prior to the final pavement cap. FWTFASOLID AS A ROCK GEOSCIENCES- RICHMOND AMERICAN HOMES December 20, 2021 Bella at Piazza Serena Project /La Quinta J.N. 21-176 Page 32 Plan Reviews, Future Improvements and/or Grading Petra should review any subsequent or revised plans when they become available and issue an addendum letter to this report. If additional site improvements are considered in the future, our firm should be notified so that we may provide design recommendations to mitigate movement, settlement and/or tilting of the structures. Potential problems can develop when drainage on the pads and slopes is altered in any way such as placement of fill and construction of new walkways, patios, landscape walls, swimming pools, spas and/or planters. Therefore, it is recommended that we be engaged to review the final design drawings, specifications, and grading plan prior to any new construction. If we are not provided the opportunity to review these documents with respect to the geotechnical aspects of new construction and grading, it should not be assumed that the recommendations provided herein are wholly or impart applicable to the proposed improvements. REPORT LIMITATIONS This report is based on the proposed residential tract and the geotechnical observations made during our literature review of the prior consultant's as -graded report, field exploration, and our limited soil laboratory testing within the site. No representatives of Petra were present during the previous grading activities that have been completed to -date at this site. This report has been prepared consistent with that level of care being provided by other professionals providing similar services at the same locale and in the same time period. The contents of this report are professional opinions and as such, are not to be considered a guaranty or warranty. Based on our findings, the conclusions and recommendations presented herein and within the referenced report by our firm were prepared in conformance with generally accepted professional engineering practices. GE■�G ENC SOLID AS A ROCK G RICHMOND AMERICAN HOMES December 20, 2021 Bella at Piazza Serena Project /La Quinta J.N. 21-176 Page 33 We appreciate this opportunity to be of service. If you have questions, please contact this office. Respectfully submitted, PETRA GEOSCIENCES, INC. f - I 22./20/21 Edward Lump �'!'' PF0 P. Z(Z Siamak Jafroudi, PhD oFCSSI Associate Geologist c 4+� No.1924 �'° A Senior Principal Engineer �pQ� JAF��9l CEG 1924 m GE 2024 C+ a o W No. GE002024 P1 EL/SJ/lv ` q��O106 Q�N * i �F CA1.�F� Attachments: References �y cto�� Figure 1 — Site Location Map s= CA1�F Figure 2 — Exploration Location Map Appendix A — Exploration Logs - Borings Appendix B — Laboratory Test Procedures / Laboratory Data Summary Appendix C — Liquefaction Analysis and CPT Sounding Logs Appendix D — Seismic Design Parameters Appendix E — Standard Grading Specifications Distribution: (1) Addressee (1) Mr. Ben Etemadi, Hunsaker & Associates W:\2020-2025\2021\100\21-176\Reports\21-176 250 Precise Grading Plan Review and Update Recs.docx 0 V= I'RA SOLID AS A ROCK RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta REFERENCES December 20, 2021 J.N. 21-176 Page 34 American Concrete Institute, 2008, Building Code Requirements for Structural Concrete (ACI 318-08) and Commentary. American Society for Testing and Materials (ASTM) - Standard - Section Four - Construction, Volume 04.08 Soil and Rock. Bryant, W.A., and Hart, E.W., 2007, Fault -Rupture Hazard Zones in California, Alquist-Priolo Earthquake Fault Zoning Act with Index to Earthquake Fault Zones Maps, California Geological Survey, Special Publication 42. California Building Code (2019), California Code of Regulations, Title 24, Par 2, Volume 2 of 2, Based on the 2018 International Building Code, California Building Standards Commission. California Geologic Survey, 2021, Earthquake Zones of Required Investigation, Wildomar Quadrangle, accessed March, hllps://maps.conservation.ca.gov/cgs/EQZApp/app/ California Department of Water Resources (DWR), 1964, Coachella Valley Investigation, Bulletin 108, dated July. California Department of Water Resources, 2004, California Groundwater - Bulletin 118. 2021, Water Data Library, accessed March, http://www.water.ca.gov/waterdatalibrgU/groundwater/ Cao, T., et al., 2003, Revised 2002 California Probabilistic Seismic Hazard Maps, June 2003: California Geological Survey. Coachella Valley Water District (CVWD), 2013, Engineer's Report on Water Supply and Replenishment Assessment, Lower Whitewater River Subbasin Area of Benefit, 2013-2014, dated April. County of Riverside, 2021, Map My County System, version 10.0, accessed March, https://gis.cogI tyofriverside.us/Html5Viewer/?viewer-MMC_Public Earth Systems Southwest (ESSW), 2004, Geotechnical Engineering Report, La Quinta 97 Tract 30092, Proposed 39- Acre Residential Development, NWC of Monroe Street and Avenue 58, La Quinta, Riverside County, California, for K. Hovnanian Forecast Homes, Inc., File Number 09870-01, 04-11-795, dated December 6. 2005, Final Report of Testing and Observations Performed During Grading, Tract 30092, La Quinta, California, for K. Hovnanian Forecast Homes, Inc., File Number 09870-02, 05-07-743, dated July 11. Google EarthTM 2021, by Google Earth, Inc., http://www.google.com/earth/index.html, accessed March. Hunsaker and Associates Irvine, Inc., 2021a, Model Precise Grading Plan, Tract 30092, Lots 94 - 97, undated. 2021b, Precise Grading Plan, Tract 30092, Lots 1, 5-14, 20-47, Lots 57-69 and 90-93, undated. International Conference of Building Officials, 1998, "Maps of Known Active Fault Near -Source Zones in California and Adjacent Portions of Nevada", California Division of Mines and Geology. Jennings, C.W. and Bryant, W.A., 2010, Fault Activity Map of California: California Geological Survey, Geologic Data Map No. 6. Lancaster, Hayhurst & Bedrossian, 2012, Preliminary Geologic Map of Quaternary Surficial Deposits in Southern California Palm Springs 30'x 60' Quadrangle, CGS Special Report 217, Plate 24. PETRASOL10 AS A ROCK �� GEOSCIENCES'" RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta REFERENCES December 20, 2021 J.N. 21-176 Page 35 Office of Statewide Health Planning and Development (OSHPD), 2021, Seismic Design Maps, U.S. Seismic Design Maps (seismicmaps.org) Petra Geotechnical, Inc., 2010, Feasibility -Level Geotechnical Review, Lots 1, 5-14, 20-47, 57-69, and 90-97 of Tract 30092, Piazza Serena Project, Northwest Corner of Monroe and Avenue 58, City of La Quinta, Riverside County, California, for Capstone Advisors, J.N. 356-10, dated November 19. Petra Geosciences, Inc., 2021 a, Feasibility/Due-Diligence Geotechnical Review Report, Piazza Serena Project, 60 Vacant Residential Lots within Tract 30092, Northwest Corner Monroe Street and 58th Avenue, City of La Quinta, Riverside County, California, J.N. 21-176, dated April 9. 2021b, Post -Tension Foundation Recommendations, 60 Vacant Residential Lots within Tract 30092, Piazza Serena Project, Northwest Corner Monroe Street and 58th Avenue, City of La Quinta, Riverside County, California, J.N. 21-176, August 23. Riverside County RCIT, Map My County, 2021, accessed March, http://mmc.rivcoit.org/MMC Public/Viewer.html?Viewer--MMC Public Sladden Engineering (Sladden), 2001, Geotechnical Investigation, Tentative Tract 30092, Avenue 58 and Monroe Street, La Quinta Area, Riverside County, California, for Barton Properties, Inc., Project No. 544-1029, 01- 02-070, dated February 9. 2004, Geotechnical Update, Residential Development, Avenue 58 and Monroe Street, La Quinta, California, for Forecast Homes, Project No. 544-1029, 04-09-611, dated August 31. Sneed, M., Brandt, J.T., and Solt, M., 2014, Land Subsidence, Groundwater Levels, and Geology in the Coachella Valley, California, 1993-2010, USGS Scientific Investigation Report 2014-5075. Sneed, M. and Brandt, J.T., 2020, Detection and Measurement of Land Subsidence and Uplift Using Global Positioning System Surveys and Interferometric Synthetic Aperture Radar, Coachella Valley, California, 2010 - 2017, USGS Scientific Investigations Report 2020-5093, Southern California Earthquake Center (SCEC), 1999, Recommended Procedures for Implementation of DMG Special Publication 117, Guidelines for Analyzing and Mitigating Liquefaction Hazards in California: organized through the Southern California Earthquake Center, University of Southern California. Southern California Earthquake Data Center (SCEDC), 2014, http://www.data.scec.org/significant/index.html. Standard Specifications for Public Works Construction (Greenbook), 2009, BNI Publishers. Tokimatsu, K.; Seed, H.B.; 1987; Evaluation of settlements in sands due to earthquake shaking; Journal of Geotechnical Engineering: Vol. 113, No. 8, p. 861-879. United States Geologic Survey (U.S.G.S.), 1996a, Probabilistic Seismic Hazard Assessment for the State of California, Open -File Report 96-706. 1996b, National Seismic -Hazards Maps, Open -File Report 96-532. 2002, Documentations for the 2002 Update of the National Seismic Hazard Maps, Open -File Report 02-20. PETRASOL10 AS A ROCK �� GEOSCIENCES'" RICHMOND AMERICAN HOMES Bella at Piazza Serena Project /La Quinta REFERENCES December 20, 2021 J.N. 21-176 Page 36 2007, Preliminary Documentation for the 2007 Update of the United States National Seismic Hazard Maps, Seismic Hazards Mapping Project, Open -File Report 2007-June Draft. 2011, Earthquake Ground Motion Parameters, Version 5.1.0, utilizing ASCE 7 Standard Analysis Option, dated February 10. 2021, Unified Hazard Tool Calculator, Unified Hazard Tool (usgs.eov) Wire Reinforcement Institute (WRI), 1996, Design of Slabs on Ground. ItPETRA SOL10 AS A ROCK GEOSCIENCES'" FIGURES PETRASOLID AS A ROCK GEOSCIENCES- Bermuda 4'r D ones La Quinta It4Ek r.,n Indio '/SITE a` Vi sta Santa Rosa LEGEND 'II" -Approximate Site Location I- Reproduced from The National Map Viewer, USGS (2021) 86 Cochran A gym. Coachella PETRAoGEOSCIENCOUNTY CENTER DRIVE, SUITE M TEMECULA, CALIFORNIA 9CES, INC. 2591 PHONE: (951) 600-9271 COSTA MESA MURRIETA PALM DESERT SANTACLARITA Site Location Map Piazza Serena - Tract No. 30092 La Quinta, Riverside County, California DATE: December2021 J.N.: 21-176 Figure 1 DWG BY: epl SCALE: NTS o-� • C:PT= � B-11 • B-14 Rik B-12 s %l3 r • CPT-1 • B-2 �� .t � j • B-3 w ^. t w CPT-2 w • ' B-6 Ip IB-5 ., • r — % 0 Orr, LEGEND PETRAoGECOUNTY CENTER DRIVE, SUITE M TEMECUOSCIENLA, CALIFORNIA 9CES, INC. 2591 PHONE: (951) 600-9271 s • COSTAMESA MURRIETA PALM DESERT SANTACLARITA -Approximate Site Location Boring and CPT Location Map B-15 • -Approximate Boring Location Piazza Serena - Tract No. 30092 La Quinta, Riverside County, California CPT-3 M -Approximate CPT Location DATE: December2021 J.N.: 21-176 Figure 2 - reproduced from Google Earth, 2021, photo date 12-2019 DWG BY: epl SCALE: NTS APPENDIX A EXPLORATION LOGS IWPETRA SOI 10 AS A ROCK IF GEOSCIENCES- Soil Classification 1 PETRA 0 Moisture Conten Dry Slightly Moist Moist Very Moist Wet (Saturated) Rlodifiers Trace < 1 % Few 1 - 5% Some 5 - 12 % Numerous 12 - 20 % Grain Size Description Sieve Size Gram Size Approximate Size Boulders >12" >12" Larger than basketball -sized Cobbles 3 - 12" 3 - 12" Fist -sized to basketball -sized Gravel coarse 3/4 - 3" 3/4 - 3" Thumb -sized to fist -sized fine #4 - 3/4" 0.19 - 0.75" Pea -sized to thumb -sized Sand coarse #10 - #4 0.079 - 0.19" Rock salt -sized to ea -sized medium #40 - #10 0.017 - 0.079" Sugar -sized to rock salt -sized fine #200 - #40 0.0029 - 0.017" Flour -sized to sugar -sized to Fines Passm 0 <0.00 9 Flour -sized and smaller anoula incivae:. PREFERRED ORDLP I. Group Name 2. Group Symbol 3. Color 4. Moisture Content 5. Relative Density / Consistency 6. Gram Sim Range 7. Structure 8. Odor 9. Additional comments indicating soil characteristics which might affect engineering properties Q © Unified Soil.Classification System,.t . Well -graded gravels,gravel-sand mixtures, little or no fines GRAVELS Clean Gravels GW GP Poorly -graded gravels, avcl-sand mixtures, little or no fines 3 more than half of coarse Jess than 5% fines) Gravels GM Silty Gravels, poorly -graded gravel-sand•silt mixtures y a fraction is larger than #4 sieve with fines GC Clayey Gravels, poorly -graded gravel -sand -clay mixtures a $ d Cc: SANDS Clean Sands W Well -graded sands, gravelly sands, littleorno fines m a 5 more than half of coarse less than 5% fines SP Poorly -graded sands, gravelly sands, little Or no fines E v g fraction is smaller than # Sands SM Silty Sands, poorly -graded sand -gravel -silt mixtures N c H sieve with fines SC Clayey Sands. poor y-gta sand -gravel -clay mixtures MI- Inorganic silts & very Fine sands, silty or clayey fine sands, A vi ,', SILTS At CLAYS clayey silts with slight plasticity vi ." Liquid Limit CL Inorganic clays of low to medium plasticity, gravelly clays, ` = s $ Less Than 50 sandy clays, silty clays, lean clays OL Organic siltys & clays of low plasticity w ._ y i= rn' c Z SILTS & CLAYS MH Ivor anic silts, micaceous or iatomaceous fine sand or silt CII Inn anice claw ofhigh plasticity, fat clays N a H Liquid Limit r OH I Organic silts and clays of medium -to -high plasticity Greater7han 50 Highly Organic Soils IPT I Peat, humus swamp soils with high organic content © Consistency - Fine Grained Soils., Apparent Density SPT (# blows/foot) Modified CAS lei Sampler (# blows/foot) Field Test Very Soft <2 <3 Easily Penetrated by thumb: exudes between thumb and fingers when sau=ed in hand Soft 2-4 3-6 Easily penetrated one inch by thumb• molded by fight finger pressure Firm 5-8 7-12 Penetrated over 1/2 inch by diumb with moderatc effort,• molded bv strone fin er oressure Stiff 9-15 13-25 Indented about 1/2 inch by thumb but penetrated only with great effort Very Stiff 16-30 26-50 Rea fly indented by thumbnail Hard >30 >50 Indented with difficulty by thumbnail © Relative Density - Coarse Grained Soils Apparent Density SPT (# blows/foot) Modified CA Sampler (# blows/foot) Field Test Very Loose <4 <5 Easily penetrated withl/2-inchreinfo nod pushedb band Loose 4-10 5-12 Easflv Penettuted with 1/2-inch reinf=mg rod pushed by hand Medium Dense 11-30 13-35 Easily penetrated 1-foot with 1/2-inch reinforcing rod driven with a 5-lb hammer Dense 31-50 36-60 Difficult to penetimted 1-foot with 1/2-inch reinforcing rod driven with a 5-lb hammer Very Dense >50 >60 Penetrated only a few inches with 1/2-inch reinforcing rod driven with a 5-lb hammer EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-1 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: Drill Method: 8" Hollw Stem Auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description W A T E R Samples Laboratory Tests Blows per 6 in. C o e B u k Moisture Content M Dry Density (pcf) Other Lab Tests 0 5 10 15 20 25 30 == ARTIFICIAL FILL (afl `Sandy Silt (ML�gray,dry-, very stiff, veryfine�rained sand. Silty Sand (SM): gray, dry, very dense, very fine grained sand. ALLUVIUM (Qal) - Silt ML _gray dry, Stiff--------------------------------- Sand with silt (SPA gray, dry, medium dense, fine grained sand. Silt ML : gray, dry, stiff, trace seashells. 50/5" 36 50/6" 11 15 21 6 8 11 4.0 2.5 3.5 6.3 99.9 97.0 97.9 80.4 . Total Depth= 9.5 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FH PLATE Petra Geosciences, Inc. EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-2 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: 03/23/2021 Drill Method: 8" Hollow Stem Auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description W A T E R Samples Laboratory Tests Blows per 6 in. C o e B u k Moisture Content M Dry Density (pcf) Other Lab Tests 0 5 10 15 20 25 30 ARTIFICIAL FILL (aQ Silt ML : gray, dry, stiff. Becomes very stiff ALLUVIUM (Qal) Silt ML : light gray, to gray, dry, very stiff. Silty Sand (SM): gray, dry, very stiff, very fine grained. 32 50 6" 10 15 18 9 11 17 8.7 13.0 8.5 109.7 80.3 93.4 = ====== : = Total Depth= 6.5 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FH PLATE Petra Geosciences, Inc. EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-3 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: 03/23/2021 Drill Method: 8" Hollow Stem Auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description W A T E R Samples Laboratory Tests Blows per 6 in. C o e B u k Moisture Content M Dry Density (pcf) Other Lab Tests 0 5 10 15 20 25 30 ARTIFICIAL FILL (afl Silt ML : gray, dry, stiff. Becomes Hard. ALLUVIUM (Qal) Silt with sand (ML)L gray, dry, very stiff, trace very fine grained sand. Becomes stiff,Trace seashells. 27 28 33 14 16 17 7 10 12 5.7 3.4 19.5 115.0 92.3 88.6 Total Depth= 6 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FH PLATE Petra Geosciences, Inc. EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-4 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: 03/23/2021 Drill Method: 8" Hollow Stem Auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description W A T E R Samples Laboratory Tests Blows per 6 in. C o e B u k Moisture Content N Dry Density (pcf) Other Lab Tests 0 5 10 15 20 25 30 AV ARTIFICIAL FILL (af) Sandy Silt (ML): gray, slightly moist, very stiff. Becomes hard. ---------------------------------------------- ALLUVIUM (Qal) Silt with sand (MLY gray, dry, hard, very fine grained sand. Becomes grayish brown, very stiff. 25 31 29 26 37 40 12 13 15 6.0 8.0 4.4 111.7 111.9 94.7 Total Depth= 6.5 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FLI PLATE Petra Geosciences, Inc. EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-5 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: 03/23/2021 Drill Method: 8" Hollow Stem Auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description fin/ A T E R Samples Laboratory Tests Blows per 6 in. C o e B u k Moisture Content N Dry Density (pcf) Other Lab Tests 0 5 10 15 20 25 30 ARTIFICIAL FILL (af) Silt ML : gray, dry, stiff. Sandy Silt (SM): gary, dry, hard, very fine grained sand, trace seashells. ALLUVIUM (gall Sand with silt (SP): gray, dry, dense, fine grained. Same as above. 38 50/6" 19 22 25 12 17 22 4.9 7.4 1.7 107.7 93.3 100.1 == °. Total Depth= 7.5 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FLI PLATE Petra Geosciences, Inc. EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-6 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: 03/23/2021 Drill Method: 8" Hollow Stem Auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description W A T E R Samples Laboratory Tests Blows per 6 in. C o e B u k Moisture Content M Dry Density (pcf) Other Lab Tests 0KXXXXXXX 5 10 15 20 25 30 Kxxxxxxxx ARTIFICIAL FILL (af) Silt ML : gray, dry, stiff. Becomes hard. Becomes grayish brown,slightly moist, hard. Same as above. ALLUVIUM (Qaq Sand with silt (SP-SM): gray, slightly moist, dense, fine grained sand. Sandy Silt Ml-: olive brown to grayish -brown, moist very stiff. 27 50 6" 25 37 47 14 25 33 11 20 20 7.7 5.4 7.3 2.9 100.1 111.2 97.1 99.5 ... � .. Total Depth= 8.5 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FH PLATE Petra Geosciences, Inc. EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-7 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: 03/23/2021 Drill Method: 8" Hollow Stem Auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description W A T E R Samples Laboratory Tests Blows per 6 in. C o e B u k Moisture Content M Dry Density (pcf) Other Lab Tests 0 5 10 15 20 25 30 ====== ARTIFICIAL FILL (afl Silt ML : gray, dry, stiff. Sandy Silt (ML): grayish brown, moist, hard, fine grained sand. ALLUVIUM Mal) Silty Sand (SM): grayish brown, moist, dense, fine grained. Same as above. 17 23 36 18 24 31 22 34 44 4.7 6.6 5.7 117.9 102.8 117.7 Total Depth= 6.0 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FH PLATE Petra Geosciences, Inc. EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-8 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: 03/23/2021 Drill Method: 8" Hollow Stem Auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description fin/ A T E R Samples Laboratory Tests Blows per 6 in. C o e B u k Moisture Content N Dry Density (pcf) Other Lab Tests 0 5 10 15 20 25 30 ARTIFICIAL FILL (af) Silt ML _gray, dry, stiff.___ Same as above with trace very fine grained sand, hard. ------------------------------------------------------ ALLUVIUM (Qal) Silt ML : gray, slightly moist, hard, trace seashells. Same as above. 28 50/6" 14 21 32 18 27 36 4.8 7.8 7.2 104.7 97.3 111.1 Total Depth= 6.5 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FLI PLATE Petra Geosciences, Inc. EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-9 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: 03/23/2021 Drill Method: 8" Hollow Stem Auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description W A T E R Samples Laboratory Tests Blows per 6 in. C o e B u k Moisture Content M Dry Density (pcf) Other Lab Tests 0 5— 10 15 20 25 30 ARTIFICIAL FILL (aQ Silt ML : gray, dry, hard. Becomes moist. _ Same as above. ALLUVIUM (Qal) Sandy Silt (ML): gray, moist, hard, very fine grained sand. Becomes grayish brown, moist, with trace seashells. 30 32 40 19 34 50/6" 20 31 31 8.2 9.9 11.9 112.1 115.4 115.1 Total Depth= 6.0 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FH PLATE Petra Geosciences, Inc. EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-10 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: 03/23/2021 Drill Method: 8" Hollow Stem Auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description W A T E R Samples Laboratory Tests Blows per 6 in. C o e B u k Moisture Content M Dry Density (pcf) Other Lab Tests 0 5 10 15 20 25 30 ARTIFICIAL FILL (aQ Silt ML _gray_, dry, stiff. Silty Sand (SM): grayish brown, moist, very dense, fine grained sand. Silty Sand (SM-ML . gray, moist, stiff to dense, fine grained sand. ALLUVIUM (Qaq Silty Sand (SM): gray, moist, hard, fine grained sand, trace seashells. 50 6" 20 28 39 23 38 39 7.2 12.4 7.1 112.8 119.0 115.2 _ Total Depth= 6.5 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FH PLATE Petra Geosciences, Inc. EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-11 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: 03/23/2021 Drill Method: 8" Hollow Stem Auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description fin/ A T E R Samples Laboratory Tests Blows per 6 in. C o e B u k Moisture Content N Dry Density (pcf) Other Lab Tests 0 5 10 15 20 25 30 ARTIFICIAL FILL (af) Silt ML _gray, dry, firm___ ------------------------------- Same as above with tarce fine grained sand. Same as above with fine gravel up to 1" in diameter. ALLUVIUM (gall Silt ML : gray, dray, hard, with trace orang oxidation staining, trace seashells. 9 18 14 50/4" 33 26 35 5.7 7.8 3.8 101.1 98.2 93.4 Total Depth= 6.0 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FLI PLATE Petra Geosciences, Inc. EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-12 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: 03/23/2021 Drill Method: 8" Hollow Stem auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description W A T E R Samples Laboratory Tests Blows per 6 in. C 0 e B u k Moisture Content N Dry Density (pcf) Other Lab Tests 0 —AVBecomes 5 10 15 20 25 30 ARTIFICIAL FILL (af) Silt ML : gray, dry, stiff. hard, trace strings ALLUVIUM (Qall Sandy silt (ML): gray, dry, hard, fine grained sand, trace seashells. Silt ML : off white, dry, very stiff. Silty Sand (SMY gray, moist, medium dense, fine grained sand. Sandy Silt (ML . gray, grayish yellow, dry, very stiff, fine grained sand. 23 50 5" 26 36 50 17 21 24 8 12 17 9.1 6.9 10.0 3.6 96.9 110.2 103.7 101.1 Total Depth= 8.5 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FLI PLATE Petra Geosciences, Inc. EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-13 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: 03/23/2021 Drill Method: 8" Hollow Stem Auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description W A T E R Samples Laboratory Tests Blows per 6 in. C o e B u k Moisture Content M Dry Density (pcf) Other Lab Tests 0 5 10 15 20 25 30 xxxxxV XXXXXXV ARTIFICIAL FILL (aQ Silt ML : gray, dry, stiff. Becomes grayish brown, slightly moist. 24 50/6" 19 50/6" 19 23 7.7 11.2 6.8 103.8 110.1 94.2 ALLUVIUM (Qal) Sand Silt ML : slightly moist, hard, rained sand. == gray, Silt Sand SM : gray, slightly moist, dense, traceporosity.24 Y ( 9 Y 9 Y Total Depth= 6.5 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FH PLATE Petra Geosciences, Inc. EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-14 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: 03/23/2021 Drill Method: 8" Hollow Stem Auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description fin/ A T E R Samples Laboratory Tests Blows per 6 in. C o e B u k Moisture Content N Dry Density (pcf) Other Lab Tests 0 5 10 15 20 25 30 AV ARTIFICIAL FILL (af) Silt ML : gray, dry, stiff. Becomes Slightly moist, hard. ---------------------------------------------- ALLUVIUM (Qal) Silt ML : grayish brown, slightly moist, hard. Same as above. 27 42 50/6" 24 30 32 18 35 42 7.5 6.1 9.5 114.4 106.3 114.1 Total Depth= 6.5 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FLI PLATE Petra Geosciences, Inc. EXPLORATION LOG Project: Piazza Serena - Tract No. 30092 Boring No.: B-15 Location: La Quinta, Riverside County, California Elevation: Job No.: 21-179 Client: Richmond American Homes Date: 03/23/2021 Drill Method: 8" Hollow Stem Auger Driving Weight: 140lbs/30" Logged By: KTM Depth (Feet) Lith- olo 9Y Material Description W A T E R Samples Laboratory Tests Blows per 6 in. C o e B u k Moisture Content M Dry Density (pcf) Other Lab Tests 0 5 10 15 20 25 30 ARTIFICIAL FILL (afl Silt ML : gray, dry, stiff. Becomes dark gray, moist, hard. Becomes gary. ALLUVIUM (Qal) _ Sandy Silt (ML): grayish brown, moist, hard, fine grainedsan_d_._ Silty Sand (SM� gray, moist, very dense, fine grained sand. 26 46 48 18 38 50/6" 27 35 45 9.3 11.2 11.6 118.4 115.7 102.1 Total Depth= 6.0 ft No groundwater encountered during drilling Boring Backfilled with cuttings on 03/23/2021. FH PLATE Petra Geosciences, Inc. APPENDIX B LABORATORY TEST PROCEDURES LABORATORYDATA SUMMARY PETRASOLID AS A ROCK GEOSCIENCES- LABORATORY TEST PROCEDURES Soil Classification Soils encountered within the exploratory borings were initially classified in the field in general accordance with the visual -manual procedures of the Unified Soil Classification System (ASTM D 2488). The samples were re-examined in the laboratory and the classifications reviewed and then revised where appropriate. The assigned group symbols are presented in the Boring Logs (Appendix A). In -Situ Moisture and Density Moisture content and unit dry density of in -place soils were determined in representative strata. Test data are summarized in the Boring Logs (Appendix A). Maximum Dry Density and Optimum Moisture Content The maximum dry density and optimum moisture content of the on -site soils were determined for selected bulk samples in accordance with current version of ASTM D 1557. The results of these tests are presented on Table B. Expansion Index The expansion index of onsite soils was determined per ASTM D 4829. The expansion index and expansion potential are presented in Table B. Corrosivity Tests Chemical analyses were performed on selected samples to determine concentrations of soluble sulfate and chloride, as well as pH and resistivity. These tests were performed in accordance with California Test Method Nos. 417 (sulfate), 422 (chloride) and 643 (pH and resistivity). Test results are presented in Table B. PETRA GEOSCIENCES, INC. Laboratory Address: 1251 W. Pomona Road, Unit 103, Corona, CA, 92882 J.N. 21-176 TABLE B LABORATORY DATA SUMMARY Laboratory Maximum Dry Density Sample Location Soil Type Optimum Moisture Maximum Dry Density ( cf) B-1 @ 0-5' Fine-grain Sandy SILT 12.0 120.0 B-8 @ 0-5' Fine- to medium grain Sandy SILT 12.5 118.5 B-13 @ 0-5' Fine-grain Sandy SILT 13.5 118.0 PER ASTM D 1557 Corrosivity Sample Location Sulfate' Chloride 3 PH Resistivity3 (%) m (Ohm -cm) CPT-1 @ 0-1.5' 0.0855 908 8.15 360 CPT-2 @ 0-1.5' 0.1140 1320 8.1 240 (1) PER CALIFORNIA TEST METHOD NO. 417 (2) PER CALIFORNIA TEST METHOD NO. 422 (3) PER CALIFORNIA TEST METHOD NO. 643 Expansion Index Sample Location Depth feet Soil Type Expansion' Index Expansion Potential CPT-1 @ 0-1.5' Fine-grain Sandy SILT 20 Very Low CPT-2 @ 0-1.5' Fine- to medium grain Sandy SILT 31 Low CPT-3 @ 0-1.5' Fine-grain Sandy SILT 28 Low (1) PER ASTM D 4829 PETRA GEOSCIENCES, INC. Laboratory Address: 1251 W. Pomona Road, Unit 103, Corona, CA, 92882 J.N. 21-176 PLATE B-1 APPENDIX C LIQ UEFA CTION ANALYSIS AND CPT SO UNDING L O GS 1VPETRAS01 /OAS A ,ROCK GEOSCIENCES' TABLE OF CONTENTS CPT-1 results Summary data report CPT-2 results Summary data report CPT-3 results Summary data report 15 CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:16 PM Project file: S:\!PR03ECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Ana lysis\Liquefaction-M8\Liquefaction Analysis.clq A PETRCosta Petra Geosciences, Inc. Airway Suite K s Mesa, CA 92626 http://www.petra-inc.com/ Project title : 21-176 Piazza Serena (RAH) Location : 58th Ave and Monroe St, La Quinta CPT file: CPT-1 Input parameters and analysis data Analysis method: NCEER (1998) G.W.T. (in -situ): 65.00 ft Use fill: No Clay like behavior Fines correction method: NCEER (1998) G.W.T. (earthq.): 10.00 ft Fill height: N/A applied: Sands only Points to test: Based on Ic value Average results interval: 3 Fill weight: N/A Limit depth applied: Yes Earthquake magnitude M w: 8.00 Ic cut-off value: 2.60 Trans. detect. applied: Yes Limit depth: 60.00 ft Peak ground acceleration: 0.73 Unit weight calculation: Based on SBT K. applied: Yes MSF method: Method based Cone resistance Friction Ratio SBTn Plot CRR plot FS Plot 0 5 10 15 20 25 w 30 35 40 45 50 55 60 65 0.8 0.7 0.6 0.5 0 0.4 Ln P J..+ u 0.3 u a U 0.2 0.1 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 0 5 10 15 20 25 30 35 40 45 50 55 60 65 100 200 300 0 2 4 6 8 10 1 2 3 4 0 0.2 0.4 O.E 0 0.5 1 1.5 2 qt (tsf) Rf (%) Ic (Robertson 1990) CRR & CSR Factor of safety M„,=71/2, sigma'=1 atm base curve Summary of liquefaction potential 1,0 0.1 1 10 Normalized friction ratio (%) Zone A, : Cyclic liquefaction likely depending on size and duration of cyclic loading Zone A2: Cyclic liquefaction and strength loss likely depending on loading and ground geometry Zone B: Liquefaction and post -earthquake strength loss unlikely, check cyclic softening 0 20 40 60 80 100 120 140 160 180 200 Zone C: Cyclic liquefaction and strength loss possible depending on soil plasticity, Qtn,Cs brittleness/sensitivity, strain to peak undrained strength and ground geometry UglrpMdjon N I ------- - ------ ------ ------ ------ -t- ♦jr--4^--- ----------------------------------- ------- ------- ------- • ♦ t —-------------------------------------------------------- ---- - ------------------------------------------------------- ---- -------------- 'Pb Liquefaction CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:11 PM 1 Project file: S:\!PR03ECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Ana lysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. Cone resistance Friction Ratio 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 v 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 1. I------- IF- ?2 -+-- CPT basic interpretation plots Pore pressure SBT Plot 10 q< <<bi ) Ri io) u kNaij Input parameters and analysis data 2 4 6 8- 10- 12- 14- 16- 18- 20 22 24 26 28 30 r r 32 34 36 38 40 42 44 , 46 48 50 52 54 56 58 60 62 64 1 2 3 Ic(SBT) Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fil weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 KQ applied: Yes Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavior appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft CPT name: CPT-1 Soil Behaviour Type 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 11 4 0 1 2 3 4 5 6 7 8 9 10 1112 13 14 15 16 17 18 SBT (Robertson et al. 1986) SBT legend 1. Sensitive fine grained 4. Clayey silt to silty 7. Gravely sand to sand ■ 2. Organic material 5. Silty sand to sandy silt ■ 8. Very stiff sand to 3. Clay to silty clay 6. Clean sand to silty sand 9. Very stiff fine grained CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:11 PM 2 Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. c 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 v 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 CPT basic interpretation plots (normalized) Norm. cone resistance Norm. friction ratio Nom. pore pressure ratio SBTn Plot 24 M ---- 18 ---- 20 22 24 ---- 26 - 28 -- 30 w -- t 32 +� ---- � 34 2 4 6 8 to 12 22 24 26 28 30 w s 32 +� � 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 Qtn Fr (%) Bq Input parameters and analysis data Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fill weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 KQ applied: Yes Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavior appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft c 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 1 2 3 4 Ic (Robertson 1990) CPT name: CPT-1 Norm. Soil Behaviour Type 0 1 2 3 4 5 6 7 8 9 10 1112 13 14 15 16 17 18 SBTn(Robertson 1990) SBTn legend 1. Sensitive fine grained 4. Clayey silt to silty 7. Gravely sand to sand ■ 2. Organic material 5. Silty sand to sandy silt ■ 8. Very stiff sand to 3. Clay to silty clay 6. Clean sand to silty sand 9. Very stiff fine grained CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:11 PM 3 Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. Liquefaction analysis overall plots (intermediate results) Total cone resistance SBTn Index Norm. cone resistance Grain char. factor 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 CL 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w r 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w s 32 C � 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 2 4 6 8 10 12 - 14 - L6 L8 20 Z2 24 26 Z8 30 - 32 34 36 38 30 32 34 - 46 - 48 - 50 - 52 54 56 58 50 52 - 100 200 300 1 2 3 4 0 50 100 150 20( 0 1 2 3 4 5 6 7 8 9 10 qt (tsf) Ic (Robertson 1990) Qtn Kc Input parameters and analysis data Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fil weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 KQ applied: Yes Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavior appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:11 PM Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq CPT name: CPT-1 Corrected norm. cone resistance 22 -+- 12+- 524- 52-+- Qtn,cs 4 This software is licensed to: Petra Geosciences, inc. CRR plot 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 v 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 Fa 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w r 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 Liquefaction analysis overall plots FS Plot Liquefaction potential Vertical settlements 2 4 6 8 10 12 14 16 18 20 22 24 26 28 ,r 30 w s 32 C � 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 0 0.2 0.4 O.E 0 0.5 1 1.5 2 0 5 10 15 20 CRR & CSR Factor of safety LPI Input parameters and analysis data Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fill weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 KQ applied: Yes Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavior appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft 4 6 8 10 12 14 16 18 20 22 24 26 28 } 30 w r 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 ra CPT name: CPT-1 Lateral displacements 2-------------- -- 4------------------- ------------------- 6------------------- ------------------- 8------------------- ------------------- 10------------------- ------------------- 12 ------------------- ------------------- 14 ------------------- ------------------- 16------------------- ------------------- 18------------------- ------------------- 20------------------- ------------------- 22------------------- ------------------- 24------------------- ------------------- 26------------------- ------------------- 28------------------- ------------------- 30------------------- ------------------- 32------------------- ------------------- 34------------------- ------------------- 36------------------- ------------------- 38------------------- ------------------- 40------------------- ------------------- 42------------------- ------------------- 44------------------- ------------------- 46------------------- ------------------- 48------------------- ------------------- 50------------------- ------------------- 52------------------- ------------------- 54------------------- ------------------- 56------------------- ------------------- 58------------------- ------------------- 60------------------- ------------------- 62------------------- ------------------- 64 - - - - - - - ----------------------- 0 1 2 3 0 Settlement (in) Displacement (in) F.S. color scheme LPI color scheme Almost certain it will liquefy Very high risk Very likely to liquefy High risk Liquefaction and no liq. are equally likely EJ Low risk Unlike to liquefy Almost certain it will not liquefy CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:11 PM 5 Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. 1,000 N U c m N 100 O N o_ a U 14 N 10 E o` Z Ilk% S ter. ♦ 1 Normalized friction ratio (%) Input parameters and analysis data Liquefaction analysis summary plots 0.8 0.7 9 0.6 Ln 0.5 U O C� 0.4 M 0.3 U U 0.2 0.1 2 0 10 CPT name: CPT-1 >. 8.0 m 7.0 v uL 6.0 0 6 5.0 0 VI v 4.0 c Y U 3.0 2.0 1.0 0.0 0 20 40 60 80 100 120 140 160 180 200 0 1 2 3 4 5 6 7 8 9 10 Qtn,cs Thickness of surface layer, H1 (m) Analysis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fill weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 K. applied: Yes Earthquake magnitude M w: 8.00 Unit weight calculation: Based on SBT C lay like behav or appied: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:11 PM 6 Project file: S:\!PR03ECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Ana lysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. Norm. cone resistance 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 CL 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 cn 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w r 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 cn Check for strength loss plots (Robertson (2010)) Grain char. factor Corrected norm. cone resistance SBTn Index 4 6 8 10 12 14 16 18 20 22 24 26 28 ,r 30 w s 32 C � 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 Gd 2 4 6 8 10 12 14 L6 L8 20 22 M 26 28 30 32- 34- 36- 38 30 42- 44- 46- 48- 50- 52- 54- 56- 58- 50- 52- 54- 0 100 200 300 400 0 1 2 3 4 5 6 7 8 9 10 0 50 100 150 20( 1 2 3 4 Qtn Kc Qtn,cs Ic (Robertson 1990) Input parameters and analysis data Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fill weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 KQ applied: Yes Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavior appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:11 PM Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq CPT name: CPT-1 Liquefied Su/Sig'v 22 -+-- 12 -+-- 52 4-- 52------- �------- ;------- q.---I-------1 54 — Peak Su ratio — U Su ratio �)u/big v 7 A PETRCosta Petra Geosciences, Inc. Airway Suite K s Mesa, CA 92626 http://www.petra-inc.com/ Project title : 21-176 Piazza Serena (RAH) Location : 58th Ave and Monroe St, La Quinta CPT file: CPT-2 Input parameters and analysis data Analysis method: NCEER (1998) G.W.T. (in -situ): 65.00 ft Use fill: No Clay like behavior Fines correction method: NCEER (1998) G.W.T. (earthq.): 10.00 ft Fill height: N/A applied: Sands only Points to test: Based on Ic value Average results interval: 3 Fill weight: N/A Limit depth applied: Yes Earthquake magnitude M w: 8.00 Ic cut-off value: 2.60 Trans. detect. applied: Yes Limit depth: 60.00 ft Peak ground acceleration: 0.73 Unit weight calculation: Based on SBT K. applied: Yes MSF method: Method based Cone resistance Friction Ratio SBTn Plot CRR plot FS Plot 0 5 10 15 20 25 w 30 35 40 45 50 55 60 65 0.8 0.7 0.6 0.5 0 O 0.4 V) P J..+ u 0.3 T U 0.2 0.1 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 0 5 10 15 20 25 30 35 40 45 50 55 60 65 100 200 300 0 2 4 6 8 10 1 2 3 4 0 0.2 0.4 O.E 0 0.5 1 1.5 2 qt (tsf) Rf (%) Ic (Robertson 1990) CRR & CSR Factor of safety M„,=71/2, sigma'=1 atm base curve Summary of liquefaction potential 1,0 00 7 � 8 91 9 �� N11► 2 5 ' t 10 �. C , 2 1 0.1 1 10 Normalized friction ratio (%) Zone A, : Cyclic liquefaction likely depending on size and duration of cyclic loading Zone A2: Cyclic liquefaction and strength loss likely depending on loading and ground geometry Zone B: Liquefaction and post -earthquake strength loss unlikely, check cyclic softening 0 20 40 60 80 100 120 140 160 180 200 Zone C: Cyclic liquefaction and strength loss possible depending on soil plasticity, Qtn,Cs brittleness/sensitivity, strain to peak undrained strength and ground geometry UqOeMdjon - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ---------- ----�------ I — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — s�-- 41---- ---- ------ - ------ - ------ -------- ------- -------------t----t--- ¢------ ------- - ------ - ------ ------- ______¢___ __¢------ ¢--- -------------- 'Pb Liquefaction CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:13 PM 8 Project file: S:\!PR03ECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Ana lysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. Cone resistance 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 v 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 2 4 6 8 ?2 -+- CPT basic interpretation plots Friction Ratio Pore pressure SBT Plot 22 -1- 424- i24- 52 -+- 100 200 300 0 2 4 6 8 10 0 2 4 qt (tsf) Rf (%) u (psi) Input parameters and analysis data Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fill weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 K° applied: Yes Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavior appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 1 2 3 4 Ic(SBT) CPT name: CPT-2 Soil Behaviour Type 0 1 2 3 4 5 6 7 8 9 10 1112 13 14 15 16 17 18 SBT (Robertson et al. 1986) SBT legend 1. Sensitive fine grained 4. Clayey silt to silty 7. Gravely sand to sand ■ 2. Organic material 5. Silty sand to sandy silt ■ 8. Very stiff sand to 3. Clay to silty clay 6. Clean sand to silty sand 9. Very stiff fine grained CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:13 PM 9 Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. c 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 v 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 CPT basic interpretation plots (normalized) Norm. cone resistance Norm. friction ratio Nom. pore pressure ratio SBTn Plot 2 4 6 8 M ---- 18 ---- 20 22 24 ---- 26 - 28 -- 30 w - t 32 +� ---- � 34 2 4 6 8 to 12 22 24 26 28 30 w s 32 +� � 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 Qtn Fr (%) Bq Input parameters and analysis data Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fill weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 KQ applied: Yes Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavior appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft c 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 1 2 3 4 Ic (Robertson 1990) CPT name: CPT-2 Norm. Soil Behaviour Type 0 1 2 3 4 5 6 7 8 9 10 1112 13 14 15 16 17 18 SBTn(Robertson 1990) SBTn legend 1. Sensitive fine grained 4. Clayey silt to silty 7. Gravely sand to sand ■ 2. Organic material 5. Silty sand to sandy silt ■ 8. Very stiff sand to 3. Clay to silty clay 6. Clean sand to silty sand 9. Very stiff fine grained CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:13 PM 10 Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. Liquefaction analysis overall plots (intermediate results) Total cone resistance SBTn Index Norm. cone resistance Grain char. factor 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 CL 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w r 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 4 6 8 10 12 14 16 18 20 22 24 26 28 ,r 30 w s 32 C � 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 2 4 6 8 10 12 - 14 - L6 L8 20 Z2 24 26 Z8 30 - 32 34 36 38 30 32 34 - 46 - 48 - 50 - 52 54 56 58 50 52 - 100 200 300 1 2 3 4 0 50 100 150 20( 0 1 2 3 4 5 6 7 8 9 10 qt (tsf) Ic (Robertson 1990) Qtn Kc Input parameters and analysis data Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fil weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 KQ applied: Yes Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavior appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:13 PM Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq CPT name: CPT-2 Corrected norm. cone resistance 22 -+- 12+- 524- 52-+- Qtn,cs This software is licensed to: Petra Geosciences, inc. CRR plot 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 v 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 Fa 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w r 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 Liquefaction analysis overall plots FS Plot Liquefaction potential Vertical settlements 2 4 6 8 10 12 14 16 18 20 22 24 26 28 ,r 30 w s 32 C � 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 0 0.2 0.4 O.E 0 0.5 1 1.5 2 0 5 10 15 20 CRR & CSR Factor of safety LPI Input parameters and analysis data Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fill weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 KQ applied: Yes Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavior appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft 4 6 8 10 12 14 16 18 20 22 24 26 28 } 30 w r 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 ra CPT name: CPT-2 Lateral displacements 2-------------- -- 4------------------- ------------------- 6------------------- ------------------- 8------------------- ------------------- 10------------------- ------------------- 12 ------------------- ------------------- 14 ------------------- ------------------- 16------------------- ------------------- 18------------------- ------------------- 20------------------- ------------------- 22------------------- ------------------- 24------------------- ------------------- 26------------------- ------------------- 28------------------- ------------------- 30------------------- ------------------- 32------------------- ------------------- 34------------------- ------------------- 36------------------- ------------------- 38------------------- ------------------- 40------------------- ------------------- 42------------------- ------------------- 44------------------- ------------------- 46------------------- ------------------- 48------------------- ------------------- 50------------------- ------------------- 52------------------- ------------------- 54------------------- ------------------- 56------------------- ------------------- 58------------------- ------------------- 60------------------- ------------------- 62------------------- ------------------- 64 - - - - - - - ----------------------- 0 1 2 3 4 0 Settlement (in) Displacement (in) F.S. color scheme LPI color scheme Almost certain it will liquefy Very high risk Very likely to liquefy High risk Liquefaction and no liq. are equally likely EJ Low risk Unlike to liquefy Almost certain it will not liquefy CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:13 PM 12 Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. 1,000 N U C co N 100 c 0 W o_ F- a U 14 N 10 E o` Z 1 Liquefaction analysis summary plots >. 8.0 m 7.0 v uL 6.0 0 6 5.0 0 VI v 4.0 c Y U 3.0 2.0 1.0 0.0 0.1 1 10 0 20 40 60 80 100 120 140 160 180 200 0 1 2 3 4 5 6 7 8 9 10 Normalized friction ratio (%) Qtn,cs Thickness of surface layer, H1 (m) CPT name: CPT-2 Input parameters and analysis data 0.8 0.7 0.6 vri 0.5 0 C� 0.4 M Ln L/) v7 0.3 T U 0.2 0.1 Analysis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fill weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 K. applied: Yes Earthquake magnitude M w: 8.00 Unit weight calculation: Based on SBT C lay like behav or appied: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:13 PM 13 Project file: S:\!PR03ECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Ana lysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. Norm. cone resistance 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 CL 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 1. 6 8 10 12 14 16 18 20 22 24 26 28 30 w r 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 11 Check for strength loss plots (Robertson (2010)) Grain char. factor Corrected norm. cone resistance SBTn Index 4 6 8 10 12 14 16 18 20 22 24 26 28 ,r 30 w s 32 C � 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 2 4 6 8 10 12 14 L6 L8 20 22 M 26 28 30- 32- 34- 36- 38-1 40- 42- 44- 46- 48- 50- 52- 54- 56- 58- 50- 52- 54- 0 100 200 300 0 1 2 3 4 5 6 7 8 9 10 0 50 100 150 20( 1 2 3 4 Qtn Kc Qtn,cs Ic (Robertson 1990) Input parameters and analysis data Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fill weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 KQ applied: Yes Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavior appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:13 PM Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq CPT name: CPT-2 Liquefied Su/Sig'v 22 -+-- 12+-- 52 4-- 52---------------;-------*-------'-- 54 — Peak Su ratio — Uq. Su ratio ou/aiy v 14 A PETRCosta Petra Geosciences, Inc. Airway Suite K s Mesa, CA 92626 http://www.petra-inc.com/ Project title : 21-176 Piazza Serena (RAH) Location : 58th Ave and Monroe St, La Quinta CPT file: CPT-3 Input parameters and analysis data Analysis method: NCEER (1998) G.W.T. (in -situ): 65.00 ft Use fill: No Clay like behavior Fines correction method: NCEER (1998) G.W.T. (earthq.): 10.00 ft Fill height: N/A applied: Sands only Points to test: Based on Ic value Average results interval: 3 Fill weight: N/A Limit depth applied: Yes Earthquake magnitude M w: 8.00 Ic cut-off value: 2.60 Trans. detect. applied: Yes Limit depth: 60.00 ft Peak ground acceleration: 0.73 Unit weight calculation: Based on SBT K. applied: Yes MSF method: Method based Cone resistance Friction Ratio SBTn Plot CRR plot FS Plot 0 0 5 ------ 5 10 -------------------- 10 15 -------L------L-------- 15 20 ------- t-------------- 20 25 -------------- F-------- 25 w 30---- -- ---------- L------ -- 30 QJ 35--- ---------- h-------- 35 40 ------ '------------ 40 45 ----= 45 50 ----------------I---- - - 50 55 ------T- ----------- 55 60 ---------------- 60 65 ----- 65 0.8 0.7 0.6 X_ 0.5 0 0.4 V) P J..+ u 0.3 u a U 0.2 0.1 Ot 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 100 200 30( 0 2 4 6 8 10 1 2 3 4 0 0.2 0.4 O.E 0 0.5 1 1.5 2 qt (tsf) Rf (%) Ic (Robertson 1990) CRR & CSR Factor of safety M„,=7112, sigma'=1 atm base curve Summary of liquefaction potential 1,0 44 0.1 1 10 I ----- I I I I I ------- Normalized Normalized friction ratio (%) Zone A, : Cyclic liquefaction likely depending on size and duration of cyclic loading �r1b q 1 ' ue facticm Zone A2: Cyclic liquefaction and strength loss likely depending on loading and ground ���geometry Zone B: Liquefaction and post -earthquake strength loss unlikely, check cyclic softening 20 40 60 80 100 120 140 160 180 200 Zone C: Cyclic liquefaction and strength loss possible depending on soil plasticity, Qtn,Cs brittleness/sensitivity, strain to peak undrained strength and ground geometry CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:14 PM 15 Project file: S:\!PR03ECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Ana lysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 v 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 CPT basic interpretation plots Cone resistance Friction Ratio Pore pressure SBT Plot ?2 -+- 22 -1- 424- 52 4- 524- 100 200 30( 0 2 4 6 8 10 0 5 10 15 qt (tsf) Rf (%) u (psi) Input parameters and analysis data Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fill weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 K° applied: Yes Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavior appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 1 2 3 4 Ic(SBT) CPT name: CPT-3 Soil Behaviour Type 0 1 2 3 4 5 6 7 8 9 10 1112 13 14 15 16 17 18 SBT (Robertson et al. 1986) SBT legend 1. Sensitive fine grained 4. Clayey silt to silty 7. Gravely sand to sand ■ 2. Organic material 5. Silty sand to sandy silt ■ 8. Very stiff sand to 3. Clay to silty clay 6. Clean sand to silty sand 9. Very stiff fine grained CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:14 PM 16 Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 v 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 CPT basic interpretation plots (normalized) Norm. cone resistance Norm. friction ratio Nom. pore pressure ratio SBTn Plot 2 4 6 8, !2 !2 4 0- 2- 4- 6- 8- 10- 12- 14- 16- 18- 20- 22- 24 26 28 30 ! w r 32 34 36 38 40 42 44- 46- �q 48- 50- 52- 54- 56- 58- 60- 62- 64- 2 4 6 8 10 -0.2 0 0.2 0.4 0.6 0.8 1 1 Qtn Fr (%) Bq Input parameters and analysis data Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fill weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 KQ applied: Yes Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavior appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft 2 3 4 Ic (Robertson 1990) 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 CPT name: CPT-3 Norm. Soil Behaviour Type 0 1 2 3 4 5 6 7 8 9 10 1112 13 14 15 16 17 18 SBTn(Robertson 1990) SBTn legend 1. Sensitive fine grained 4. Clayey silt to silty 7. Gravely sand to sand ■ 2. Organic material 5. Silty sand to sandy silt ■ 8. Very stiff sand to 3. Clay to silty clay 6. Clean sand to silty sand 9. Very stiff fine grained CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:14 PM 17 Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. Liquefaction analysis overall plots (intermediate results) Total cone resistance SBTn Index Norm. cone resistance Grain char. factor 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 CL 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w r 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 6�0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 ,r 30 w s 32 C � 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 2-- 4-- 6-- 8- 10- 12-- 14-- 1-6- 18 20 Z2 ?4 ?6 Zg 30 32 34 36 38 t0 12 14 16 18 50 52 54 56 58 50 52 100 200 30( 1 2 3 4 0 50 100 150 20( 0 1 2 3 4 5 6 7 8 9 10 qt (tsf) Ic (Robertson 1990) Qtn Kc Input parameters and analysis data Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fil weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 KQ applied: Yes Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavior appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:14 PM Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq CPT name: CPT-3 Corrected norm. cone resistance 0 50 100 150 20( Qtn,cs 18 This software is licensed to: Petra Geosciences, inc. 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 v 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 Liquefaction analysis overall plots CRR plot FS Plot Liquefaction potential Vertical settlements 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w r 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 0 0 2 2 4 4 6 6 8 8 10 10 12 -- 12 14 14 16----- 16 18----- 18 20 20 22 -------- 22 24 ----- 24 26 ---- 26 28 -------- 28 30 s 32--- ---- 30 r 32 34 C 34 36 36 38 38 40 40 42 42 44 44 46 46 48 48 50 50 52 52 54 54 56 56 58 58 60 60 62 62 64 64 22 -+- 12+- 52 4- 524- CPT name: CPT-3 Lateral displacements 0 0.2 0.4 O.E 0 0.5 1 1.5 2 0 5 10 15 20 0 0.5 1 1.5 2 0 CRR & CSR Factor of safety LPI Settlement (in) Displacement (in) Input parameters and analysis data F.S. color scheme LPI color scheme Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fill weight: N/A Almost certain it will liquefy ❑ Very high risk Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Very likely to liquefy 0 High risk Points to test: Based on Ic value Ic cut-off value: 2.60 KQ applied: Yes Liquefaction and no liq. are equally likely Low risk Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavbr appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Unlike to liquefy Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft Almost certain it will not liquefy CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:14 PM 19 Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. 1,000 C t6 N 100 LA O N o_ F- a U 14 N 10 E o` Z 1 0.1 1 10 Normalized friction ratio (%) Input parameters and analysis data Liquefaction analysis summary plots 0.8 0.7 0.6 Ln 0.5 U_ O C� 0.4 M v7 0.3 T U 0.2 0.1 0 CPT name: CPT-3 >. 8.0 m 7.0 v 6.0 w v 6 5.0 0 VI v 4.0 c Y U 3.0 2.0 1.0 0.0 0 20 40 60 80 100 120 140 160 180 200 0 1 2 3 4 5 6 7 8 9 10 Qtn,cs Thickness of surface layer, H1 (m) Analysis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fill weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 K. applied: Yes Earthquake magnitude M w: 8.00 Unit weight calculation: Based on SBT C lay like behav or appied: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:14 PM 20 Project file: S:\!PR03ECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Ana lysis\Liquefaction-M8\Liquefaction Analysis.clq This software is licensed to: Petra Geosciences, inc. Norm. cone resistance 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w 32 CL 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 w r 32 OL 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 Check for strength loss plots (Robertson (2010)) Grain char. factor Corrected norm. cone resistance SBTn Index 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 ,r 30 w s 32 C � 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 0 100 200 300 400 0 1 2 3 4 5 6 7 8 9 10 0 50 100 150 20( 1 2 3 4 Qtn Kc Qtn,cs Ic (Robertson 1990) Input parameters and analysis data Anay sis method: NCEER (1998) Depth to water table (erthq.): 10.00 ft Fill weight: N/A Fines correction method: NCEER (1998) Average results interval: 3 Transition detect. applied: Yes Points to test: Based on Ic value Ic cut-off value: 2.60 KQ applied: Yes Earthquake magnitude M W: 8.00 Unit weight calculation: Based on SBT Clay like behavior appried: Sands only Peak ground acceleration: 0.73 Use fill: No Limit depth applied: Yes Depth to water table (insitu): 65.00 ft Fill height: N/A Limit depth: 60.00 ft CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software - Report created on: 3/28/2021, 7:27:14 PM Project file: S:\!PROJECTS\2021\100\21-176 Piazza Serena (RAH)\Calcs & Analysis\Liquefaction-M8\Liquefaction Analysis.clq CPT name: CPT-3 Liquefied Su/Sig'v 22 -+- 12+- 52 4- 524- 1 1 — Peak Su ratio — Liq. Su ratio Tr—�Trf—�T�1 Su/Sig'v 21 Procedure for the evaluation of soil liquefaction resistance, NCEER (1998) Calculation of soil resistance against liquefaction is performed according to the Robertson & Wride (1998) procedure. The procedure used in the software, slightly differs from the one originally published in NCEER-97-0022 (Proceedings of the NCEER Workshop on Evaluation of Liquefaction Resistance of Soils). The revised procedure is presented below in the form of a fbwchartl: ck : tip resistance, f, : sleeve friction CJVU, o,.'O' : in -situ vertical total and effective stress units : all in kl'a initial stress exponent": n = 1.0 and calculate Q, F. and 1, iflc<_ 1.64,n=0.5 if 1.64<Ic<3.30,n=(Ic— 1.64)0.3+0.5 If lc > 3.30, It = 1.0 iterate until the change in n, An < 0.01 if CFVO, > 300 kPa. let n = 1_0 for all soils aupdated from Robertson and W ride (1998 ) Cn — 1(m) A (Flo Q = (q, —610) Cn = fs 1(1(1 100 (qc —6o ) 1, = VJ3.47— log Q)Z+(1.22+log F) J if is S 1.64, 1.0 if 1.64 < lc < 2.60. Ke = -0.4031ca + 5.581 lea —21.63 42 + 33.75 h; — 17.88 if le > 2.60, evaluate using other criteria; likely nonliquefiable if F > I % BUI. if 1.64 < Ic < 2.36 and F < 0.5%, set k = 1.0 (q,Lv)cr = KeQ 3 CRR7_5 — 93 I (q`t�,1 +0.08, if 50 5 (qe�)c: < 160 CRR7.5=0.833•I (,iv) J+0.05,if(ckjk)cs<50 if is �! 2.60, evaluate using other criteria; likely nonliquifiable if F > 1% ' "Estimating liquefaction -induced ground settlements from CPT for level ground", G. Zhang, P.K. Robertson, and RWI. Brach an CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software 22 Procedure for the evaluation of soil liquefaction resistance (all soils), Robertson (2010) Calculation of soil resistance against liquefaction is performed according to the Robertson & Wride (1998) procedure. This procedure used in the software, slightly differs from the one originally published in NCEER-97-0022 (Proceedings of the NCEER Workshop on Evaluation of Liquefaction Resistance of Soils). The revised procedure is presented below in the form of a fbwchartl: CPT qt, fs, ovo, a'vo, pa — 1 atm all same units as p. Initial stress exponent: n — 1 A. Calculate Qr,,, F,, I, n=0.381(1;)+0.05(�," J-0.15 `` Po n<-1.0 Iterate until change in n, An <— 0.01 OM [(qt —cr.,)I 0CX F, =�*100 PQ lq — ) 1, = J3.47 — log Q,, )2 + (1.22 + log F, )_ r I� r,O ) ( 2.50 < I, < 2.70 ) ( I, > 2.70 If k <— 1.64, Kc = 1.0 When 1.64 < Ic 5 2.60 Kc = 5.581,3 — 0.403 I, — 21.63 42 + 33.75Ic—17.88) K, = 6 x 10-7 Q, Y6.76 If 1.64 < Ic < 2.36 AND F, < 0.5%, set K, =1.0 Qtn.cs = Kc • Qtn CRR, , — 93 �):'.C` , + 0.08 11000- CRR,s = 0.053Q,.Ka 50 —< 0.,, ,. _< 160 ' RK Robertson, 2009. "Perf or rre rice based earthquake design using the CPT", Keynote Lecture, International Conference on Perforrrance-based Design in Earthquake GeotechnicaI Engineering —from case history to practice, IS -Tokyo, June 2009 CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software 23 Procedure for the evaluation of soil liquefaction resistance, Idriss & Boulanger (2008) CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software 24 Procedure for the evaluation of soil liquefaction resistance (sandy soils), Moss et al. (2006) CPT qt, fs, Ic I< < I, cut-off Initial estimate using raw tip measurements, friction ratio. Calculate qk,l. Repeat until an acceptable convergence tolerance is achieved. R f If' -fi' f3 C Cq = a v qt, i = Cq clt CRR = exp q 045.c� -- .110-Rf')-�.001-Rf)+c-4-0.850 Rf,I-0.848-InhAwl-0.002-Inla,�I-20.923+1.632-0-1�t! l 1 7,177 CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software 25 Procedure for the evaluation of soil liquefaction resistance, Boulanger & Idriss(2014) CRRV-7 S,a; -]m" FSra = CSRM-7 s.0-; -1°n° CSRst-7.5,0:-lm„ = 0.65 q" a,= rd I 1 d, g MSF K° rd = exp [a(z)+,6(z) • M] a(z)=-1.012-1.126sin z +5.1331 (11.73 / P(z) = 0. 106 + 0.118 sin z +5.142 (11.28 ) K,=1-C,In<-1.1 lP°) C° = 1 5 0.3 37.3-827(q,L.,4 ) JISF=1+(MSF. —1)J 8.64ap1 4 I-1.325� ll, II MSF�=1.09+(g180) 5 2.2 d and aa,, at start of earthquake shabng geLya gelya 2jq'Lya gaLyuCRRx`-gyp113 +(1000) 140) +( 137) -2.80 g.Lvcr =q, Lv+Aq, Lv Aq.Lv = 11.9 + L L exp 1.63- .6) q.Lv = C,. P P. 9.7 15.7 ') FC+2-(FC+2) m=1.338-0249(q,L,.)"' with 0.2645 m<_0.782 FC=80(lc+CFC)-137 with 001.5FC5100% 1, = [(3.47 - log 2+ 122+log (F))2 5 Q = (q. - a`�)( P° J^ with 0.5 5 n 51.0 per Robertson & Wride (1998) P. )lC.' J F=lq, A a.I-100% d,. at time of CPT sounding CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software 26 Procedure for the evaluation of liquefaction -induced lateral spreading displacements Site investigation Design Ground with SPT or earthquake geometry SPT data with Moment magnitude Geometric parameters content of earthquake (MW) for each of different or CPT data and peak surface zones in level (or acceleration (a--) gently sloping) ground with (or without) a free face Liquefaction potential analysis to calculate FS, (Ni)60cs or (qciNks (using the NCEER SPT- CPT-based method (Youd et al. 2001)) Calculation of the lateral displacement index (using Figure 1 and Equation [3]) Zones with three major geometric parameters or less - free face height (H), the distance to a free face (L), or/and slope (S) L/H or/and S If Estimated lateral displacement, LD (Ni)6o. < 14 For gently sloping ground without a free face, or (q�lN). < 70 LD = (S + 0.20) • LDI (for 0.2% < S < 3.5%) evaluate For level ground with a free face, potential LD = 6 • (L/H) o.a LDI (for 5 < L/H < 40) of flow liquefaction Zones with more than three major geometric parameters Evaluation of lateral displacements based on other approaches and engineering judgment 1 Flowchart itIustratirig major steps in estimating liquefaction- induced lateral spreading displacements using the proposed approach 60 50 40 as 30 cc c> 20 E 3 E 10 01 - 0.0 0.5 1.0 1.5 2.0 Factor of safety, FS 1 Figure 1 zMax LDI= r'= JO 1 Equation [31 1 "Estimating liquefaction -induced ground settlerrentsfromCPrfor level ground", G. Zhang, P.K. Robertson, and RWI. Bradhrran CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software 27 Procedure for the estimation of seismic induced settlements in dry sands venage shear stress. T. = CSR 6v0= 0.65 - all" 6v0 tia 9 Fsrunate small shear sham modulus. Ge u p = 0.0188 . [10(ossI lba) I. (qt - a,) Estin ate shear stiam amplinide, f (based on Piadel (1998)) 1 + a ebR y = R 100 1+a R = s (Note t,, andG 0 same units) 0 Ij a=0.0389 +01A Pa b = 6400 cU (P& Estuliate volinnehic sti;im 111 11 k vt le,s l -2C 1)60ts r20 CN 0604, = Qsu: 8.3 - 1 - 1—` 4.6 Volumetiic sham in design earthqu.-&-e N 045 �vol = evo](15) 15 Nc=(M_4)2.17 Seismic settlement, s GWT s = 2 f Zvol dz Robertson, P.K. and Lisheng, S., 2010, "Estimation of seismic compression in dry soils using the CPT" FIFTH INTERNATIONAL CONFERENCE ON RECENT ADVANCES IN GEOTECHNICAL EARTHQUAKE ENGINEERING AND SOIL DYNAMICS, Symposium in honor of professor I. M. Idriss, San Diego, CA CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software 28 Liquefaction Potential Index (LPI) calculation procedure Calculation of the Liquefaction Potential Index (LPI) is used to interpret the liquefaction assessment calculations in terms of severity over depth. The calculation procedure is based on the methology developed by Iwasaki (1982) and is adopted by AFPS. To estimate the severity of liquefaction extent at a given site, LPI is calculated based on the following equation: 20 LPI = f (10 - 0,5Z) x F xd: where: FL = 1 - F.S. when F.S. less than 1 FL = 0 when F.S. greaterthan 1 z depth of measurment in meters Valuesof LPI range between zero (0) when no test point is characterized as liquefiable and 100 when all points are characterized as susceptible to liquefaction. Iwasaki proposed four (4) discrete categories based on the numeric value of LPI: • LPI = 0 : Liquefaction risk is very low • 0 < LPI <= 5 : Liquefaction risk is low • 5 < LPI <= 15 : Liquefaction risk is high . LPI > 15 : Liquefaction risk is very high Ft 0.0 1.0 2.0 0 5 L 10 0 15 l0 0 KZ) 10 0 5 10 15 20 Graphical presentation of the LPI calculation procedure CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software 29 Shear -Induced Building Settlement (Ds) calculation procedure The shear -induced building settlement (Ds) due to liquefaction below the building can be estimated using the relationship developed by Bray and Macedo (2017): Ln(Ds) = el + c2 . LBS + 0.58 * Ln Tanh \ 6 HL I + 4.59*Lrz(Q)-0.42*Liz (Q)2-0.02*B+ 0.84 - Ln(CAVdp) + 0.41 • Lea (Sal) + F where Ds is in the units of mm, c1= -8.35 and c2= 0.072 for LBS <_ 16, and c1= -7.48 and c2= 0.014 otherwise. Q is the building contact pressure in units of kPa, HL is the cumulative thickness of the liquefiable layers in the units of m, B is the building width in the units of m, CAVdp is a standardized version of the cumulative absolute velocity in the units of g-s, Sal is 5%-damped pseudo -acceleration response spectral value at a period of 1 s in the units of g, and F_ is a normal random variable with zero mean and 0.50 standard deviation in Ln units. The liquefaction -induced building settlement index (LBS) is: LBS = [-1' . �% Z where z (m) is the depth measured from the grouna surrace > u, w is a rounaation-weighting factor wherein W = 0.0 for z less than Df, which is the embedment depth of the foundation, and W = 1.0 otherwise. The shear strain parameter (£_shear) is the liquefaction -induced free -Feld shear strain (in %) estimated using Zhang et al. (2004). It is calculated based on the estimated Dr of the liquefied soil layer and the calculated safety factor against liquefaction triggering (FSL). CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software 30 References • Lunne, T., Robertson, P.K., and Powell, J.J.M 1997. Cone penetration testing in geotechnical practice, E & FN Spon Routledge, 352 p, ISBN 0-7514-0393-8. • Boulanger, R.W. and Idriss, I. M., 2007. Evaluation of Cyclic Softening in Silts and Clays. ASCE Journal of Geotechnical and Geoenvironmental Engineering June, Vol. 133, No. 6 pp 641 -652 • Boulanger, R.W. and Idriss, I. M., 20 14. CPT AND SPT BASED LIQUEFACTION TRIGGERING PROCEDURES. DEPARTMENT OF CIVIL & ENVIRONMENTAL ENGINEERING COLLEGE OF ENGINEERING UNIVERSITY OF CALIFORNIA AT DAVIS • Robertson, P.K. and Cabal, K.L., 2007, Guide to Cone Penetration Testing for Geotechnical Engineering. Available at no cost at http://www.geologismiki.gr/ • Robertson, P.K. 1990. Soil classification using the cone penetration test. Canadian Geotechnical Journal, 27 (1), 151 -8. • Robertson, P.K. and Wride, C.E., 1998. Cyclic Liquefaction and its Evaluation based on the CPT Canadian Geotechnical Journal, 1998, Vol. 35, August. • Youd, T.L., Idriss, I.M., Andrus, R.D., Arango, I., Castro, G., Christian, J.T., Dobry, R., Finn, W.D.L., Harder, L.F., Hynes, M.E., Ishihara, K., Koester, J., Liao, S., Marcuson III, W.F., Martin, G.R., Mitchell, J.K., Moriwaki, Y., Power, M.S., Robertson, P.K., Seed, R., and Stokoe, K.H., Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF Workshop on Evaluation of Liquefaction Resistance of Soils, ASCE, Journal of Geotechnical & Geoenvironmental Engineering, Vol. 127, October, pp 817-833 • Zhang, G., Robertson. P.K., Brachman, R., 2002, Estimating Liquefaction Induced Ground Settlements from the CPT, Canadian Geotechnical Journal, 39: pp 1168 -1180 • Zhang, G., Robertson. P.K., Brachman, R., 2004, Estimating Liquefaction Induced Lateral Displacements using the SPT and CPT, ASCE, Journal of Geotechnical & Geoenvironmental Engineering, Vol. 130, No. 8, 861 -871 • Pradel, D., 1998, Procedure to Evaluate Earthquake -Induced Settlements in Dry Sandy Soils, ASCE, Journal of Geotechnical & Geoenvironmental Engineering, Vol. 124, No. 4, 364-368 • Iwasaki, T., 1986, Soil liquefaction studies in Japan: state -of-the-art, Soil Dynamics and Earthquake Engineering, Vol. 5, No. 1, 2-70 • Papathanassiou G., 2008, LPI-based approach for calibrating the severity of liquefaction -induced failures and for assessing the probability of liquefaction surface evidence, Eng. Geol. 96:94 —104 • P.K. Robertson, 2009, Interpretation of Cone Penetration Tests - a unified approach., Canadian Geotechnical Journal, Vol. 46, No. 11, pp 1337-1355 • P.K. Robertson, 2009. "Performance based earthquake design using the CPT", Keynote Lecture, International Conference on Performance -based Design in Earthquake Geotechnical Engineering - from case history to practice, IS -Tokyo, June 2009 • Robertson, P.K. and Lisheng, S., 2010, "Estimation of seismic compression in dry soils using the CPT" FIFTH INTERNATIONAL CONFERENCE ON RECENT ADVANCES IN GEOTECHNICAL EARTHQUAKE ENGINEERING AND SOIL DYNAMICS, Symposium in honor of professor L M. Idriss, SAN diego, CA • R. E. S. Moss, R. B. Seed, R. E. Kayen, J. P. Stewart, A. Der Kiureghian, K. 0. Cetin, CPT -Based Probabilistic and Deterministic Assessment of In Situ Seismic Soil Liquefaction Potential, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 132, No. 8, August 1, 2006 • I. M. Idriss and R. W. Boulanger, 2008. Soil liquefaction during earthquakes, Earthquake Engineering Research Institute MNO - 12 • Jonathan D. Bray & Jorge Macedo, Department of Civil & Environmental Engineering, Univ. of California, Berkeley, CA, USA, Simplified procedure for estimating liquefaction -induced building settlement, Proceedings of the 19th International Conference on Soil Mechanics and Geotechnical Engineering, Seoul 201 CLiq v.3.3.1.14 - CPT Liquefaction Assessment Software 31 APPENDIX D SEISMIC DESIGN PARAMETERS PETRASOLID AS A ROCK GEOSCIENCES- 3/27/2021 U.S. Seismic Design Maps SfA 21-176 Latitude, Longitude: 33.629228,-116.235050 ® IID AVE 58 Substation Go gle Date Design Code Reference Document Risk Category Site Class Vida Bella Dr Fiori del Des It IL Serenata Dr D 3/27/2021, 11:59:46 AM ASCE7-16 11 D - Default (See Section 11.4.3) OSHPD Type Value Description Ss 1.5 MCER ground motion. (for 0.2 second period) St 0.6 MCER ground motion. (for 1.0s period) SMS 1.8 Site -modified spectral acceleration value SMt null -See Section 11.4.8 Site -modified spectral acceleration value Sps 1.2 Numeric seismic design value at 0.2 second SA SW null -See Section 11.4.8 Numeric seismic design value at 1.0 second SA Type Value Description SDC null -See Section 11.4.8 Seismic design category Fa 1.2 Site amplification factor at 0.2 second Fv null -See Section 11.4.8 Site amplification factor at 1.0 second PGA 0.609 MCEG peak ground acceleration FPGA 1.2 Site amplification factor at PGA PGA, 0.731 Site modified peak ground acceleration TL 8 Long -period transition period in seconds SsRT 1.694 Probabilistic risk -targeted ground motion. (0.2 second) SsUH 1.862 Factored uniform -hazard (2% probability of exceedance in 50 years) spectral acceleration SsD 1.5 Factored deterministic acceleration value. (0.2 second) S1 RT 0.651 Probabilistic risk -targeted ground motion. (1.0 second) S1 UH 0.73 Factored uniform -hazard (2% probability of exceedance in 50 years) spectral acceleration. S1 D 0.6 Factored deterministic acceleration value. (1.0 second) PGAd 0.609 Factored deterministic acceleration value. (Peak Ground Acceleration) CRS 0.91 Mapped value of the risk coefficient at short periods CR1 0.892 Mapped value of the risk coefficient at a period of 1 s Map data ©2021 https://seismicmaps.org 1/2 3/27/2021 U.S. Seismic Design Maps DISCLAIMER While the information presented on this website is believed to be correct, S.E.A.O.Q. /OSHPD and its sponsors and contributors assume no responsibility or liability for its accuracy. The material presented in this web application should not be used or relied upon for any specific application without competent examination and verification of its accuracy, suitability and applicability by engineers or other licensed professionals. SEAOC / OSHPD do not intend that the use of this information replace the sound judgment of such competent professionals, having experience and knowledge in the field of practice, nor to substitute for the standard of care required of such professionals in interpreting and applying the results of the seismic data provided by this website. Users of the information from this website assume all liability arising from such use. Use of the output of this website does not imply approval by the governing building code bodies responsible for building code approval and interpretation for the building site described by latitude/longitude location in the search results of this website. https:Hseismicmaps.org 2/2 APPENDIX E STANDARD GRADING SPECIFICATIONS PETRASOLID AS A ROCK GEOSCIENCES- STANDARD GRADING SPECIFICATIONS These specifications present the usual and minimum requirements for projects on which Petra Geosciences, Inc. (Petra) is the geotechnical consultant. No deviation from these specifications will be allowed, except where specifically superseded in the preliminary geology and soils report, or in other written communication signed by the Soils Engineer and Engineering Geologist of record (Geotechnical Consultant). I. GENERAL A. The Geotechnical Consultant is the Owner's or Builder's representative on the project. For the purpose of these specifications, participation by the Geotechnical Consultant includes that observation performed by any person or persons employed by, and responsible to, the licensed Soils Engineer and Engineering Geologist signing the soils report. B. The contractor should prepare and submit to the Owner and Geotechnical Consultant a work plan that indicates the sequence of earthwork grading, the number of "spreads" and the estimated quantities of daily earthwork to be performed prior to the commencement of grading. This work plan should be reviewed by the Geotechnical Consultant to schedule personnel to perform the appropriate level of observation, mapping, and compaction testing as necessary. C. All clearing, site preparation, or earthwork performed on the project shall be conducted by the Contractor in accordance with the recommendations presented in the geotechnical report and under the observation of the Geotechnical Consultant. D. It is the Contractor's responsibility to prepare the ground surface to receive the fills to the satisfaction of the Geotechnical Consultant and to place, spread, mix, water, and compact the fill in accordance with the specifications of the Geotechnical Consultant. The Contractor shall also remove all material considered unsatisfactory by the Geotechnical Consultant. E. It is the Contractor's responsibility to have suitable and sufficient compaction equipment on the job site to handle the amount of fill being placed. If necessary, excavation equipment will be shut down to permit completion of compaction to project specifications. Sufficient watering apparatus will also be provided by the Contractor, with due consideration for the fill material, rate of placement, and time of year. F. After completion of grading a report will be submitted by the Geotechnical Consultant. IL SITE PREPARATION A. Clearing and Grubbing 1. All vegetation such as trees, brush, grass, roots, and deleterious material shall be disposed of offsite. This removal shall be concluded prior to placing fill. 2. Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic tanks, wells, pipe lines, etc., are to be removed or treated in a manner prescribed by the Geotechnical Consultant. Page 1 STANDARD GRADING SPECIFICATIONS III. FILL AREA PREPARATION A. Remedial Removals/Overexcavations 1. Remedial removals, as well as overexcavation for remedial purposes, shall be evaluated by the Geotechnical Consultant. Remedial removal depths presented in the geotechnical report and shown on the geotechnical plans are estimates only. The actual extent of removal should be determined by the Geotechnical Consultant based on the conditions exposed during grading. All soft, loose, dry, saturated, spongy, organic -rich, highly fractured or otherwise unsuitable ground shall be overexcavated to competent ground as determined by the Geotechnical Consultant. 2. Soil, alluvium, or bedrock materials determined by the Soils Engineer as being unsuitable for placement in compacted fills shall be removed from the site. Any material incorporated as a part of a compacted fill must be approved by the Geotechnical Consultant. 3. Should potentially hazardous materials be encountered, the Contractor should stop work in the affected area. An environmental consultant specializing in hazardous materials should be notified immediately for evaluation and handling of these materials prior to continuing work in the affected area. B. Evaluation/Acceptance of Fill Areas All areas to receive fill, including removal and processed areas, key bottoms, and benches, shall be observed, mapped, elevations recorded, and/or tested prior to being accepted by the Geotechnical Consultant as suitable to receive fill. The contractor shall obtain a written acceptance from the Geotechnical Consultant prior to fill placement. A licensed surveyor shall provide sufficient survey control for determining locations and elevations of processed areas, keys, and benches. C. Processing After the ground surface to receive fill has been declared satisfactory for support of fill by the Geotechnical Consultant, it shall be scarified to a minimum depth of 6 inches and until the ground surface is uniform and free from ruts, hollows, hummocks, or other uneven features which may prevent uniform compaction. The scarified ground surface shall then be brought to optimum moisture, mixed as required, and compacted to a minimum relative compaction of 90 percent. D. Subdrains Subdrainage devices shall be constructed in compliance with the ordinances of the controlling governmental agency, and/or with the recommendations of the Geotechnical Consultant. (Typical Canyon Subdrain details are given on Plate SG-1). E. Cut/Fill & DeeD Fill/Shallow Fill Transitions In order to provide uniform bearing conditions in cut/fill and deep fill/shallow fill transition lots, the cut and shallow fill portions of the lot should be overexcavated to the depths and the horizontal limits discussed in the approved geotechnical report and replaced with compacted fill. (Typical details are given on Plate SG-7.) Page 2 STANDARD GRADING SPECIFICATIONS IV. COMPACTED FILL MATERIAL A. General Materials excavated on the property may be utilized in the fill, provided each material has been determined to be suitable by the Geotechnical Consultant. Material to be used for fill shall be essentially free of organic material and other deleterious substances. Roots, tree branches, and other matter missed during clearing shall be removed from the fill as recommended by the Geotechnical Consultant. Material that is spongy, subject to decay, or otherwise considered unsuitable shall not be used in the compacted fill. Soils of poor quality, such as those with unacceptable gradation, high expansion potential, or low strength shall be placed in areas acceptable to the Geotechnical Consultant or mixed with other soils to achieve satisfactory fill material. B. Oversize Materials Oversize material defined as rock, or other irreducible material with a maximum dimension greater than 12 inches in diameter, shall be taken offsite or placed in accordance with the recommendations of the Geotechnical Consultant in areas designated as suitable for rock disposal (Typical details for Rock Disposal are given on Plate SG-4). Rock fragments less than 12 inches in diameter may be utilized in the fill provided, they are not nested or placed in concentrated pockets; they are surrounded by compacted fine grained soil material and the distribution of rocks is approved by the Geotechnical Consultant. C. Laboratory Testing Representative samples of materials to be utilized as compacted fill shall be analyzed by the laboratory of the Geotechnical Consultant to determine their physical properties. If any material other than that previously tested is encountered during grading, the appropriate analysis of this material shall be conducted by the Geotechnical Consultant as soon as possible. D. Import If importing of fill material is required for grading, proposed import material should meet the requirements of the previous section. The import source shall be given to the Geotechnical Consultant at least 2 working days prior to importing so that appropriate tests can be performed and its suitability determined. V. FILL PLACEMENT AND COMPACTION A. Fill Lam Material used in the compacting process shall be evenly spread, watered, processed, and compacted in thin lifts not to exceed 6 inches in thickness to obtain a uniformly dense layer. The fill shall be placed and compacted on a horizontal plane, unless otherwise approved by the Geotechnical Consultant. Page 3 STANDARD GRADING SPECIFICATIONS B. Moisture Conditioning Fill soils shall be watered, dried back, blended, and/or mixed, as necessary to attain a relatively uniform moisture content at or slightly above optimum moisture content. C. Compaction Each layer shall be compacted to 90 percent of the maximum density in compliance with the testing method specified by the controlling governmental agency. (In general, ASTM D 1557- 02, will be used.) If compaction to a lesser percentage is authorized by the controlling governmental agency because of a specific land use or expansive soils condition, the area to received fill compacted to less than 90 percent shall either be delineated on the grading plan or appropriate reference made to the area in the soils report. D. Failing Areas If the moisture content or relative density varies from that required by the Geotechnical Consultant, the Contractor shall rework the fill until it is approved by the Geotechnical Consultant. E. Benching All fills shall be keyed and benched through all topsoil, colluvium, alluvium or creep material, into sound bedrock or firm material where the slope receiving fill exceeds a ratio of 5 horizontal to 1 vertical, in accordance with the recommendations of the Geotechnical Consultant. VI. SLOPES A. Fill Slopes The contractor will be required to obtain a minimum relative compaction of 90 percent out to the finish slope face of fill slopes, buttresses, and stabilization fills. This may be achieved by either overbuilding the slope and cutting back to the compacted core, or by direct compaction of the slope face with suitable equipment, or by any other procedure that produces the required compaction. B. Side Hill Fills The key for side hill fills shall be a minimum of 15 feet within bedrock or firm materials, unless otherwise specified in the soils report. (See detail on Plate SG-5.) C. Fill -Over -Cut Slopes Fill -over -cut slopes shall be properly keyed through topsoil, colluvium or creep material into rock or firm materials, and the transition shall be stripped of all soils prior to placing fill. (see detail on Plate SG-6). Page 4 STANDARD GRADING SPECIFICATIONS D. Landscapes All fill slopes should be planted or protected from erosion by other methods specified in the soils report. E. Cut Slopes 1. The Geotechnical Consultant should observe all cut slopes at vertical intervals not exceeding 10 feet. 2. If any conditions not anticipated in the preliminary report such as perched water, seepage, lenticular or confined strata of a potentially adverse nature, unfavorably inclined bedding, joints or fault planes are encountered during grading, these conditions shall be evaluated by the Geotechnical Consultant, and recommendations shall be made to treat these problems (Typical details for stabilization of a portion of a cut slope are given in Plates SG-2 and SG-3.). 3. Cut slopes that face in the same direction as the prevailing drainage shall be protected from slope wash by a non -erodible interceptor swale placed at the top of the slope. 4. Unless otherwise specified in the soils and geological report, no cut slopes shall be excavated higher or steeper than that allowed by the ordinances of controlling governmental agencies. 5. Drainage terraces shall be constructed in compliance with the ordinances of controlling governmental agencies, or with the recommendations of the Geotechnical Consultant. VII. GRADING OBSERVATION A. General All cleanouts, processed ground to receive fill, key excavations, subdrains, and rock disposals must be observed and approved by the Geotechnical Consultant prior to placing any fill. It shall be the Contractor's responsibility to notify the Geotechnical Consultant when such areas are ready. B. Compaction Testing Observation of the fill placement shall be provided by the Geotechnical Consultant during the progress of grading. Location and frequency of tests shall be at the Consultants discretion based on field conditions encountered. Compaction test locations will not necessarily be selected on a random basis. Test locations may be selected to verify adequacy of compaction levels in areas that are judged to be susceptible to inadequate compaction. C. Frequency of Compaction Testing In general, density tests should be made at intervals not exceeding 2 feet of fill height or every 1000 cubic yards of fill placed. This criteria will vary depending on soil conditions and the size of the job. In any event, an adequate number of field density tests shall be made to verify that the required compaction is being achieved. Page 5 STANDARD GRADING SPECIFICATIONS VIII. CONSTRUCTION CONSIDERATIONS A. Erosion control measures, when necessary, shall be provided by the Contractor during grading and prior to the completion and construction of permanent drainage controls. B. Upon completion of grading and termination of observations by the Geotechnical Consultant, no further filling or excavating, including that necessary for footings, foundations, large tree wells, retaining walls, or other features shall be performed without the approval of the Geotechnical Consultant. C. Care shall be taken by the Contractor during final grading to preserve any berms, drainage terraces, interceptor swales, or other devices of permanent nature on or adjacent to the property. S:\!BOILERS-WORK\REPORT INSERTS\STANDARD GRADING SPECS Page 6 NATURAL GROUND — — — — ----------------�— PROPOSED GRADE ----------_. -- PROPOSED COMPACTED FILL REMOVE UNSUITABLE MATERIAL :'TOPSOIL, ALLUVIUM, COLLUVIUM-, TYPICAL BENCHING',, \ .1N� J /•� COMPETENT NATIVE SOIL" OR SEDROCKMATERIALS . See Detail Below AS DETERMINED BY THE ... GE OTECHNICAL', ,, CONSULTANT ; -.SUBARAIN.SYSTEM - 'r X :_".9 CUBIC FEET PER LINEAL FOOT '.OF OPEN -GRADED GRAVEL -t > �' .ENCASED IN FILTER FABRIC. 1 \ SEE PLATE SG-3 FOR OPEN- .5 MIN.GRADED GRAVEL SPECIFICATIONS. (2'TYPICAL) rt r ^� (•r 7r�}� r , �' r :r v' "FILTER FABRIC SHALL CONSIST DEPTH AND BEDDING MAY VARY WITH PIPE AND LOAD OF MIRAFI 140N OR APPROVED- c� i c �, _ a CHARACTERISTICS. " EQUIVALENT. FILTER FABRIC a TYPICAL ` ' ` I_�'r" �� ` t SHOULD BE LAPPED A MINIMUM OF 12 INCHES. ALTERNATE SU13DRAIN SYSTEM - " f 1 ra MINIMUM OF 9 CUBIC FEET PER LINEAL FOOT OF CLASS 2 FILTER MATERIAL. SEE PLATE SG-3 FOR CLASS 2 FILTER MATERIAL s MIN.,' r ��, < ' SPECIFICATIONS. CLASS f n , MATERIAL DOES NOT NEED TO BE ENCASED IN -FILTER -FABRIC. 18 MIN. (& TYPICAL) MINIMUM 6-INCH DIAMETER PVC SCHEDULE 40, OR ABS SDR-35 WITH A MINIMUM OF EIGHT 114-INCH DIAMETER PERFORATIONS PER LINEAL FOOT IN BOTTOM HALF OF PIPE. PIPE TO BE LAID WITH PERFORATIONS FACING DOWN. NOTES: T. FOR CONTINUOUS RUNS IN EXCESS OF 500 FEET USE 8-INCH DIAMETER PIPE. 2. FINAL 20 FEET OF PIPE AT OUTLET SHALL BE NON -PERFORATED AND BACKFILLED WITH FINE-GRAINED MATERIAL. 'CANYONSURDRAMDETAIL OVEREXCAVATE PAD AS RECOMMENDED BY GEOTECHNICAL CONSULTANT PROPOSED GRADE 1V MINIMUM TO TOP OF BACKCUT NOTES: 1*. 30'MAXIMUM VERTICAL SPACING BETWEEN SUBDRAIN SYSTEMS. 2. tOO'MAXIMUM HORIZONTAL DISTANCE BETWEEN NON -PERFORATED OUTLET PIPES. (See Below) 3. MINIMUM GRADIENT OF 2% FOR ALL PERFORATED AND NON -PERFORATED PIPE. 19117-1V] W&U.*1419 I ik 100r max OUTLET PIPE (TYPICAL) !OUTLET PIPE (TYPICAL) -PERFORATED PIPE (TYPICAL) BUTTRESS OR STABILIZATION FILL DETAIL APPROVED FILTER MATERIAL GRADED GRAVEL WRAPPED IN FILTER FABRIC ORCLASS 2FILTER MATERN4. 5CUBIC FEET OFCLASS 2FILTER K&4T[R|AL.VV[THOUTFILTER FABRIC. 'oR' 3CUBIC FEET OFOPEN-GRADED GRAVEL PER LINEAR FOOT WITH FILTER FABRIC. FILTER FABRIC SHOULD CONSIST OF ` NURAF|14ON0REQUIVALENT, AND SHOULD BELAPPED AMINIMUM OF 12 INCHES MINIMUM 2% GRADE TO OUTLET. 4-INCHPERFORATED PIPE WITH PERFORATIONS DOWN. MINIMUM 2% GRADE TO OUTLET PIPE. APPROVED ON -SITE MATERIAL PER SOILS ENGINEER 10 min. COMPACTED TO A MINIMUM OF 90% MAXIMUM DENSITY. 4-INCH NON -PERFORATED PIPE PIPE SPECIFICATIONS: 1.4-INCH MINIMUM DIAMETER, PVC SCHEDULE 4uORABS SDR-3s 2. FOR PERFORATED PIPE, MINIMUM 8 PERFORATIONS PER FOOT ON BOTTOM HALF OF PIPE. FILTER MATERIALIFABRIC SPECIFICATIONS: OPEN -GRADED GRAVEL ENCASED |NFILTER FABRIC. (MIRAR|4ONOREQUIVALENT) CLASS uPERMEABLE FILTER MATERIAL PER CALTRAm8 STANDARD SPECIFICATION 68-1.025. OPEN -GRADED SIEVE SIZE I1/24NCH GRAVEL PERCENT PASSING 88-1V0 CLASS 2 FILTER SIEVE SIZE 1-INCH MATERIAL PERCENT PASSING 100 1'UoCM 5'40 3/4-INCH 90-100 3/4-INCH 0-17 3/8-INCH 40'100 3/8-INCH 0-7 No4 25'48 No. 200 0'8 No 8 18-33 mu.{0 5'15 Nu-50 o'7 BUTTRESS OR STABILIZATIOV FILL SUBDRAIN PLATE SG-3 FINISHED GRADE SLOPE FACE 10, CLEAR AREA FOR FOUNDATIONS, UTILITIES AND SWIMMING POOLS 7 5' cti MIN. WINDROW COMPACTED FILL TYPICAL WINDROW DETAIL (END VIM GRANULAR SOIL JETTED OR FLOODED TO FILL VOIDS COMPACTED FILL PLACED IN '6-T08-INCH-THICK--'--"--"--'-: HORIZONTAL LIFTS. 15'MIN. IOU MAX. STREET 5'OR MIN. OF Z BELOW DEPTH OF DEEPEST UTILITY TRENCH, WHICHEVER IS GREATER OR FLOODED GRANULAR SOIL NOTE OVERSIZE ROCK IS DEFINED AS CLASTS HAVING A MAXIMUM DIMENSION OF 12" OR LARGER PETRA I TYPICAL ROCK DISPOSAL DETAIL I PLATE SG-4• NOTES: 1. WHERE NATURAL SLOPE GRADIENT IS 5:1 OR LESS, BENCHING IS NOT NECESSARY; HOWEVER, FILL IS NOT TO BE PLACED ON COMPRESSIBLE OR UNSUITABLE MATERIAL. 2. SOILS ENGINEER TO DETERMINE IF SUBDRAIN IS REQUIRED. FILL SLOPE ABOVE NATURAL SLOPE PROPOSED CUT / FILL CONTACT .gHowN nm ('PAnimr. PI AN GRADE COMPACTED FILL P E T R A FILL SLOPE ABOVE CUT SLOPE SIT -L-OT UNSUITABLE MATERIAL EXPOSED IN PORTION OF CUT PAD ORIGINAL GROUND SURFACE PROPOSED GRADE REMOVE ROCK UNSUITABLE D gED MATERIAL WEpi.HERE ,/ ` (D) or I CO��UViUM. A or ORIGINAL GROUND SURFACE I /� PROPOSED GRADE REMOVE ( �(D) or UNSUITABLE 5, / I 6 MATERIAL 1� MIN.,, C 74;- PILL (F) AjNFy •� �•"yE�„ E• wUV`U� � '��, e• n COL ALLUVIUM OVEREXCAVATE AND RECQMPACT i SOIL TOP COMPETENT BEDROCK OR SOIL MATERIALS AS DETERMINED BY THE GEOTECHNICAL CONSULTANT TYPICAL BENCHING; MAXIMUM : i _ ;l DEPTH OF OVEREXCAVATION• FOOTINGDEPTH TO 3 FEET ......... EQUAL DEPTH 3 TO 6 FEET ...................... 3 FEET GREATER THAN 6 FEET ............. 112 THE THICKNESS OF DEEPEST FILL PLACED WITHIN THE "FILL" PORTION (F) TO 15 FEET MAXIMUM ' CUT LOTS AND CUT -FILL PLATE SG-7 TRANSITION LOTS PROPOSED 2:1 FILL SLOPE EXISTING GROUND SURFACE DESIRED REMOVAL LI D= RECOMMENDED DEPTH DFREMOVAL PER 6EDTEDHN0nLREPORT PETRA TYPICAL REMOVALS BEYOND TOE OF PROPOSED FILL SLOPE PROPOSED CUT LOT NOTE: 1. "D" SHALL BE 10 FEET MINIMUM OR AS DETERMINED BY SOILS ENGINEER. I i, t �V PETRA SHEAR KEY ON DAYLIGHT CUT LOTS I PLATE SG-9