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0309-324 (SFD) Geotechnical Report
Earth Systems Southwest CITY OF LA WIN BUILDING & SAFETY OFF APPROVE' FOR CONSTRUCTIO DATE BY 7 - DGS S -r Consulting Engineers and Geologists PAUL GOLDEN CONSTRUCTION, INC. 73-710 FRED WARING DRIVE, SUITE 101 PALM, DESERT, CALIFORNIA 92260 GEOTECHNICAL ENGINEERING REPORT MIRAGLIA RESIDENCE 75-370 COYOTE CANYON COURT AT THE TRADITIONS LA QUINTA, CALIFORNIA December 19, 2003 © 2003 Earth Systems Southwest Unauthorized use orcopying of this document is'strictly prohibited without the express written consent of Earth Systems Southwest. File No.: 09462-01 03-12-772 Earth Systems Southwest 79-811B CountryClub Drive Bermuda Dunes, CA 92201 (760)345-1588 (8 00) 9247015 FAX (760) 345-7315 December 19, 2003 Paul. Golden Construction, Inc. 73-710 Fred- Waring Drive, Suite 101 Palm Desert, California 92260 . Attention: Mr. Paul. Golden Project: 78-370 Coyote Canyon Court Miraglia Residence at The Traditions La Quinta, California Subject: GEOTECHNICAL ENGINEERING REPORT Dear Mr. Golden: File No.: 09462-0.1 03-12-772 We take pleasure in presenting this Geotechnical Engineering Report prepared for the proposed residence to be located at 78-370 Coyote Canyon Court in the City of La Quinta, California. This report presents our findings and recommendations for site grading and foundation design, incorporating the information provided to our office. The site is suitable for the proposed development, provided the recommendations in this report are followed in design and construction. In general, the upper soils should be compacted to improve .bearing capacity and reduce settlement. The site is subject to strong ground motion from the San Andreas.Fault. This report should -stand as a whole and no .part, of the report should be excerpted or used to the exclusion of any other part. This report completes our scope of services in accordance with our agreement, dated December 1, 2003. Other services that may be required, such as plan review and grading observation, are. additional services and will be billed according to our Fee Schedule in effect at the time services are provided. Unless requested. in writing, the. client is responsible for distributing this report to the appropriate governing agency or other members of the, design team. We appreciate the opportunity to provide our professional services. Please contact our office if there are any questions or comments concerning this report or its recommendations. Respectfully su EARTH SY H� EST Q� � z Craig S. H CE 38 J EXP. 03M1 105 CE 38234 SER/csh/reh CM1. FOF CA1.�F0. Distribution: 6 onstruction, Inc. 2/RBF Engineering; Attn.: Mr. Joe Cicchini I/RC File 2BD File i TABLE OF CONTENTS Page EXECUTIVESUMMARY..........:...............................::.............:...:...................................ii Section 1 INTRODUCTION.................................................................................................1 1.1 Project Description................:....:..........:...:..................:...........................................1 1.2 Site 'Description ................................................ • ....... .......................1 1.3 Purpose and Scope of Work...................:..........................:...........,:.......:................2 Section 2 METHODS OF EXPLORATION AND TESTING...........................................3 2.1 Field Exploration ............... ........................................... :............ :............... . Section3 DISCUSSION.........................................................................................................4 3.1 Soil Conditions...................................................................:....................................4 12 Groundwater.......................:....::::....::....:.....:....:....:................................................. 4 3.3 Geologic Setting...................................................................................................:::4 3.4 Geologic Hazards.......................................:.:............................:..:...........................5. 3.4.1 Seismic Hazards..::......................................................................................5 3.4.2 Secondary Hazards 3.4.3 Site Acceleration and Seismic Coefficients...:..:..........................................7 Section 4 CONCLUSIONS...-..............................................................................................9 Section 5 RECOMMENDATIONS....................................................................................11 SITE DEVELOPMENT AND GRADING:.:......:...................:.:............:..............:....:......11 5.1 Site Development— Grading...............:.................................................................11 5 2 Excavations and Utility Trenches.....................................................................:.:..13 5,3 Slope Stability of Graded Slopes:.........::..................:..:..........................e..............13 STRUCTURES..:...............................................................................................................13 5.4 Foundations............................................................:......................:...............:........14 5.5 Slabs -on -Grade: ......... 6*"*-****"**""***'***'******.**"**""""*"*'*"'***'*"*""*"***'* ... *'*"** ......... 15 5.6 Retaining Walls.....................................................................................................16 5.7 Mitigation of Soil Corrosivity on Concrete..................:.......:...:........:................:..17 5.8 Seismic Design Criteria,.........................................................................................17 5.9 Pavements...,...:...................:.........................:....:..........:............................:...........18 Section 6 LIMITATIONS AND ADDITIONAL SERVICES..........................................19 6.1 Uniformity of Conditions and Limitations............:..:.........:..:.............:....::......:.....19 6.2 Additional Services................................................................................................20 REFERENCES................. .........................................................................................................21 APPENDIX A Site and Boring Location Map Table 1 — Fault Parameters 2001 California Building Code (CBC) Seismic' Parameters Logs of CPT Soundings EARTH SYSTEMS SOUTHWEST ii EXECUTIVE SUMMARY The site is located at 78-370 Coyote Canyon Courtin the City of La Quinta, California. The proposed development will consist of a single-family residence with a basement. We understand that the proposed structure will be wood -frame and stucco construction supported with perimeter wall foundations. and concrete slabs -on -grade. The basement will be constructed of masonry units or cast -in-place concrete. The proposed project may be constructed as planned, provided that the recommendations in this report are incorporated in the final design and construction. Site development will include clearing and grubbing of vegetation, site grading, building pad preparation, underground utility installation, and concrete driveway and sidewalks placement. Remedial site grading is recommended to provide, uniform support for the foundations. We consider the most significant geologic hazard to the project to be the potential for moderate to severe seismic shaking that is likely to occur during the design life of the proposed structures. The project site is located in the highly seismic southern California region within the influence of several fault systems that are considered to be active or potentially active. The site is located in Seismic Zone 4 of the 2001 California Building Code (CBC). Structures should be designed in accordance with the values and parameters given within the CBC. The seismic design parameters are presented in the following table and within the report. EARTH SYSTEMS SOUTHWEST 111 SUMMARY OF RECOMMENDATIONS Design.Item.:Recommended Parameter, Reference Seetian'No:t`= Foundations Allowable Bearing Pressure Continuous wall footings Pad Column footings 1,500 psf 5.4 2,000 psf Foundation Type Spread Footing 5.4 Materials Engineered fill -Bearing Allowable Passive Pressure 250 pcf 5.4 Active Pressure 30 pcf 5.6 At -rest -Pressure 45 pcf 5.6 Allowable Coefficient of Friction 0.35 5.4 Soil Expansion Potential Very low EI<20 .3.1 Hazards and Seismic -Geologic Potential Negligible 3.4.2 -Liquefaction Significant Fault and Magnitude San Andreas, M7.7 3.4.3; 5.8 Fault Type A 3.4.3; 5.8 Seismic Zone 4 3.4.3; 5.8 Soil Profile Type SD 3.4.3; 5.8 Near -Source Distance 12.7 km 3.4.3; 5.8 Seismic Coefficient, NA 1.00 3.4.3; 5.8 Seismic Coefficient, Nv 1.09 3.4.3; 5.8 Pavement TI equal to 4.5 (Light Traffic) 2.5" AC / 4.0" AB 5.9 TI equal to 5.0 (Heavy Traffic) 3.0" AC / 4.0" AB 5.9 Slabs Floor Slabs On engineered fill 5.5 -Building Modulus of Subgrade Reaction 200 pci 5.5 Site Conditions -Eidsting Fill N/A -Existing Soil Corrosivity Low sulfates Low chlorides 5.7 Groundwater Depth Presently >50 feet, Historic >50 feet 3.2 Estimated Cut (includes over -excavation) 23 feet - cut 1.1 The recommendations contained within this report are subject to the limitations presented in Section 6 of this report. We recommend that all individuals using this report read the limitations. EARTH SYSTEMS SOUTHWEST December 19, 2003 1 of '22 File No.: 09462-01 03-12-772 GEOTECHNICAL ENGINEERING REPORT MIRAGLIA RESIDENCE 78-370 COYOTE CANYON COURT AT THE TRADITIONS LA QUINTA, CALIFORNIA Section 1 INTRODUCTION' 1.1 Project Description This Geotechnical Engineering Report has been prepared for the proposed single-family residence to be located at 78-370 Coyote Canyon Court within the The Traditions Club, in the City of La Quinta, California. The proposed single-family residence will be a one-story above -grade structure, and the lower levels of the main house and guest suites will consist of a basement. The excavation for the basement. will require temporary cut slopes during construction to allow construction of basement retaining walls: We assume that the proposed residence will use a combination of construction types, including steel moment frames, masonry walls; and wood -frame; and will be supported by conventional shallow continuous or pad footings. Site development will include site grading, .building pad preparation, underground utility installation, and concrete driveway and sidewalk placement. 'Based on existing site topography and ground conditions, site grading is expected to consist of cuts of about 23 feet. Deeper cuts may be required to allow for the over - excavation within the basement. We assumed a maximum column load of 30 kips and a maximum wall loading of 2.0 kips per linear foot as a basis for the foundation ,recommendations. All loading is assumed to be dead plus actual live load. If actual structural loading exceeds these assumed values, we. would need to reevaluate the given recommendations. 1.2 Site Description The proposed residence, is to be constructed on a relatively flat and vacant lot. The project site is presently covered by an irrigated lawn. The site location is shown on Figure 1 in Appendix A. The history of past use, and development of the property was not investigated as part of our scope of services. No evidence of past development was observed on the site during our reconnaissance. However, a review of selected aerial photographs suggests that the site is located in an area previously occupied by a date grove. The removal of these pre-existing features was performed under the observation and approval of Sladden Engineering. There may be underground utilities near and within the proposed building area. These utility lines may include, but are not limited to, domestic water, electric, sewer, telephone, gas, and irrigation lines. EARTH SYSTEMS SOUTHWEST December 19, 2003 2 of 22 File No.: 09462-01 03-12-772 1.3 Purpose and Scope of Work The purpose for our services was to evaluate the site .soil conditions and to provide professional opinions and recommendations regarding the proposed development of the site. The scope of work included the following:- ➢ A general reconnaissance of the site. ➢ Shallow subsurface exploration by advancing three cone penetrometer soundings to depths ranging from 15 to 30 feet. ➢ A review of selected published technical literature pertaining to ,the site. ➢ An engineering analysis and evaluation of the acquired data from the exploration and testing programs. ➢ A summary of our findings and recommendations provided in this written report. This report contains the following: ➢ Discussions on subsurface soil and groundwater conditions. ➢ Discussions on regional and local geologic conditions. ➢ Discussions on geologic and seismic hazards. ➢ Graphic and tabulated results of laboratory tests and field studies. ➢ Recommendations regarding: • Site development and grading criteria. • Excavation conditions and buried utility' installations. • Structure foundation type and design. • Allowable foundation bearing capacity and expected total and differential settlements. • Concrete slabs -on -grade. • Lateral earth pressures and coefficients. • Mitigation of the potential corrosivity of site soils. to concrete and steel reinforcement. • Seismic design parameters. • Preliminary pavement structural sections. Not Contained in This Report: Although available through Earth Systems Southwest, the current scope of our services does not include: ➢ A corrosive study to determine cathodic protection of concrete or buried pipes. ➢ An environmental assessment.. ➢ An investigation for the presence or absence of wetlands, hazardous or toxic materials in the soil, surface water, groundwater, or air on, below, or adjacent to the subject property. EARTH SYSTEMS SOUTHWEST December 1, 9., 2003 3 of 22 File No.: 09462-01 Section 2 METHODS OF EXPLORATION AND TESTING 2.1 Field Exploration Subsurface exploration was conducted on December 19, 2003, using Holguin, Fahan, &c Associates, Inc. of Orange, California to advance three electric cone penetrometer (CPT) soundings to approximate depths of 15 to 30 feet. CPT soundings providea, nearly continuous profile of the soil stratigraphy with readings every 5 cm (2 inches) in depth. The soundings were made at the approximate locations shown on the Site .Exploration Plan, Figure 2, attached to this report. Interpretive logs of the CPT soundings are also attached to this report. The CPT explorations were conducted by hydraulically advancing an instrument Hogentogler 10 cm2 conical probe into the ground at a ground rate of 2 cm per second, using a 21.5 -ton truck as a reaction mass. An electronic data acquisition system recorded a nearly continuous log of the resistance of the soil against the cone tip (Qc) and soil friction against the cone sleeve (Fs) as the probe was advanced. Empirical relationships (Robertson and Campanella, 1989) were applied to the data to give a nearly continuous profile of the soil stratigraphy. The final logs of the CPT soundings represent our interpretation of the contents of the field logs. The final logs are included in Appendix A of this report. The stratification lines represent the approximate boundaries, between soil types although the transitions may be gradational. EARTH SYSTEMS SOUTHWEST December 19, 2003 4 of 22 File No.: 09462-01 03-12-772 Section 3 DISCUSSION 3.1 Soil Conditions The field exploration indicates that near surface soils consist generally of sands and silty sands. The upper 12 feet of soils consist of fill that was placed and compacted during mass grading of the development. These fill soils appear to be dense and fine to medium grained. Soils below 12 feet consist of native clayey silt and silty clay soils and are generally very stiff to hard in nature. The CPT logs provided in Appendix A include more detailed descriptions of the soils encountered. The surficial soils are visually classified. to be in the very low expansion (EI < 20) category in accordance with Table 18A -I -B of the California Building Code. Deeper clay soils should be tested for expansion potential once the basement excavations have been completed.. In and climatic regions, granular soils may have a potential to collapse upon wetting. Collapse (hydroconsolidation) may occur when the soluble cements (carbonates) in the soil matrix dissolve, causing the soil to densify from its loose configuration from deposition. The hydroconsolidation. potential is commonly mitigated by recompaction of a zone beneath building pads. The site lies within a recognized blow sand hazard area. Fine particulate matter (PMjo) can create an air quality hazard if dust is blowing. Watering the surface, planting grass or landscaping, or hardscape normally mitigates this hazard. 3.2 Groundwater Free groundwater was not encountered in the borings during exploration. The depth to groundwater in the area is believed to be greater than 100 feet below existing grade. Historic groundwater levels are estimated to be between 50 and 100 feet. Groundwater levels may fluctuate with precipitation, irrigation, drainage, regional pumping from wells, and site grading. Groundwater should not be a factor in design or construction at this site. 3.3 Geologic Setting Regional Geology: The site lies within the Coachella Valley, a part of the Colorado Desert geomorphic province. A significant feature within the Colorado Desert geomorphic province is the Salton Trough. The Salton Trough is a large northwest -trending structural depression that extends approximately 180 miles from the San Gorgonio Pass to the Gulf of California. Much of this depression in the area of the Salton Sea is below sea level. The Coachella Valley forms the northerly part of the Salton Trough. The, Coachella Valley contains a thick sequence of sedimentary deposits that are Miocene to recent in age. Mountains surrounding the Coachella Valley include the Little San Bernardino Mountains on the northeast, foothills of the San Bernardino Mountains on the northwest, and the San Jacinto and Santa Rosa Mountains on the southwest. These mountains expose primarily Precambrian metamorphic and Mesozoic granitic rocks. The San Andreas Fault zone within the Coachella Valley consists of EARTH SYSTEMS SOUTHWEST December 19, 2003 5 of 22 File No. 09462-01 03-12-772 the Garnet Hill Fault, the Banning Fault, and the Mission Creek Fault that traverse along the northeast margin of the valley. Local GeoloQy: The project site is located within the La Quinta cove area in the southeast part of the Coachella Valley. The sediments within the valley consist of fine- to coarse-grained sands with interbedded clays, silts, gravels, and cobbles of alluvial (water -laid) origin several hundreds of feet thick. 3.4 Geologic Hazards Geologic hazards that may affect the region include seismic hazards (groundshaking, surface fault rupture; soil liquefaction, and other secondary earthquake -related hazards), slope instability, flooding, ground subsidence, and erosion. A discussion follows on the specific hazards to this site. 3.4.1 Seismic Hazards Seismic Sources: Several active faults or seismic zones lie within 62 miles (1,00 kilometers) of the project site as shown on Table 1 in Appendix A. The primary seismic hazard to the site is strong groundshaking from earthquakes along the San Andreas and San Jacinto Faults. The Maximum Magnitude Earthquake (Mme) listed is from published geologic information available for each fault (Cao et. al, CGS, 2003). The M..x corresponds to the maximum earthquake believed to be tectonically possible. Surface Fault Rupture: The project site does not lie within a currently delineated State of California, Alquist-Priolo Earthquake Fault Zone (Hart, 1997). Well -delineated fault lines cross through this region as shown on California Geological Survey (CGS) maps (Jennings, 1994). Therefore, active fault rupture is unlikely to occur at the project site. While fault rupture would most likely occur along previously established fault traces, future fault rupture could occur at other locations. Historic Seismicity: Six historic seismic events (5.9 M or greater) have significantly affected the Coachella Valley in the last 100 years. They are as follows: • Desert Hot Springs Earthquake — On December 4, 1948, a magnitude 6.5 ML (6.OMW) earthquake occurred east of Desert Hot Springs. This event was strongly felt in the Palm Springs area. • Palm Springs Earthquake — A magnitude 5.9 ML (6.2MW) earthquake occurred on July 8, 1986 in the Painted Hills, causing minor surface creep of the Banning segment of the San Andreas Fault. This event was strongly felt in the Palm Springs area and caused structural damage, as well as injuries. • Joshua Tree Earthquake — On April 22, 1992, a magnitude 6.1 ML (6.1MW) earthquake occurred in the mountains 9 miles east of Desert Hot Springs. Structural damage and minor injuries occurred in the Palm Springs area as a result ofthis earthquake. • Landers and Big Bear Earthquakes — Early on June .28, 1992, a magnitude 7.5 Ms (7.3MW) earthquake occurred near Landers, the largest seismic event in Southern California for 40 years. Surface rupture occurred just south of the town of Yucca Valley and extended some EARTH SYSTEMS SOUTHWEST December 19, 2003 6 of 22 File No.: 09462-01 03-12-772 43 miles toward Barstow. About three hours later, a magnitude 6.6 Ms (6.4Mw) earthquake occurred near Big Bear Lake. No significant structural damage from these earthquakes was reported in the Palm Springs area. Hector Mine Earthquake On. October 16, 1999, a magnitude 7.1MW earthquake occurred on the Lavic Lake and Bullion Mountain Faults north of Twentynine Palms. While this event was widely felt; no significant structural damage has been reported in the Coachella Valley:. Seismic Risk: While accurate earthquake predictions are not possible, various agencies have conducted statistical risk analyses. In 2002, the California Geological Survey (CGS) and the United States Geological Survey (USGS) completed the latest generation of probabilistic seismic hazard maps. We have used these maps in our evaluation of the seismic risk at the site. The Working Group of California Earthquake Probabilities (WGCEP, 1995) estimated a 22% conditional probability that a magnitude 7 or greater earthquake may occur between 1994 and 2024 along, the Coachella segment. of the San Andreas Fault. The primary seismic risk at the site is a potential earthquake along the San Andreas Fault. Geologists believe that the San Andreas Fault has characteristic earthquakes that result from rupture of each fault segment. The estimated characteristic earthquake is magnitude 7.7 for the Southern Segment of the fault (USES, 2002): This segment has the longest elapsed time since rupture than any other part of the San Andreas Fault. The last rupture occurred about 1690 AD, based on dating by the USGS near Indio (WGCEP, 1995). This segment has also ruptured on about 1020, 1300, and 1450 AD, with an average recurrence interval of about 220 years. The San Andreas Fault may rupture in multiple segments, producing a higher magnitude earthquake. Recent paleoseismic studies suggest that both, the San Bernardino Mountain Segment to the north and the Coachella Segment may have ruptured together in 1450 and 1690 AD (WGCEP, 1995). 3.4.2 Secondary Hazards Secondary seismic hazards related to groundshaking include soil liquefaction, ground subsidence, tsunamis, and seiches: The site is far inland, so the hazard from tsunamis is non-existent. At the present time, no water storage reservoirs are located in the immediate vicinity of the site. Therefore, 'hazards from seiches are considered negligible at this time. Soil Liquefaction: Liquefaction is the loss of soil strength from sudden shock (usually earthquake shaking), causing the soil to become a fluid mass. In general, for the effects of liquefaction to be manifested at the surface, groundwater levels must be within 50 feet of the ground surface and the soils within the saturated zone must also be susceptible to liquefaction. The project site does lie within a moderate liquefaction hazard zone for shallow groundwater as designated by the Riverside County; however, the potential for liquefaction to occur at this site is considered negligible because the depth of groundwater beneath the site exceeds 50 feet. No free groundwater was encountered in our exploratory borings. Ground Subsidence: The potential for seismically induced ground subsidence is considered to be slight at the site. Dry sands tend to settle and densify when subjected to strong earthquake shaking. The amount of subsidence is dependent on relative density of the soil, ground motion, and earthquake duration. Uncompacted fill areas may be susceptible to seismically induced settlement. EARTH SYSTEMS SOUTHWEST December 19, 2003 7 of 22 File No.: 094'62-01 03-12-772 Slope Instability: The site is relatively flat. Therefore, potential. hazards from slope instability, landslides, or debris flows are considered negligible. Flooding: The project site does not lie within a designated FEMA 100 -year flood plain. The project site may be in an area where sheet' flooding and erosion could occur. If significant changes are proposed for the site, appropriate project design, construction, and maintenance can minimize the site sheet flooding potential. 3.4.3 Site Acceleration and Seismic Coefficients, Site Acceleration: The potential intensity of ground motion may be estimated by the horizontal peak ground, acceleration (PGA), measured in "g" forces. Included in Table l are deterministic estimates of site acceleration from possible earthquakes at nearby faults. Ground motions are dependent primarily on the earthquake magnitude and. distance to the seismogenie (rupture) zone. Accelerations are also dependent upon attenuation by rock and soil deposits, direction of rupture, and type of fault. For these reasons, ground motions may vary considerably in the same general area. This variability can be expressed statistically by a standard deviation about a mean relationship. The PGA alone is an inconsistent scaling factor to compare to the CBC Z factor and is generally a poor indicator of potential structural damage during an earthquake. Important factors influencing the structural performance are the duration and frequency of strong ground motion, local subsurface conditions, soil -structure interaction, and structural details. The following table provides the probabilistic estimate of the PGA taken from the 2002 CGS/USGS seismic hazard maps. Table 3.1 Estimate of PGA from 2002 CGS/USGS Probabilistic Seismic Hazard Maps Risk Equivalent. Return Period (years) PGA (g 10% exeeedance in 50 years 1 475 0.48 Notes: 1. Based on a. soft rock site, SB/o,, and soil amplification factor of 1.0 "for Soil Profile Type SD. 2. Spectral acceleration (SA) at period of 0.2 seconds divided by 2.5 for 5% damping, as defined by the International Building Code. 2001 CBC Seismic Coefficients: The California Building Code (CBC) seismic design. criteria are based on a Design Basis Earthquake (DBE) that has an earthquake ground motion with a 10% probability of occurrence in 50 years. The PGA estimates given above are provided for information on the seismic risk inherent in the CBC design. The seismic and site coefficients given in Chapter 16 of the 2001 California Building Code are provided below and in Section 5.8 of this report. EARTH SYSTEMS SOUTHWEST December 1.9, 2003 8 of 22 File No.: 09462-01 03-12-772 Table 3.2 2001 CBC Seismic Coefficients for Chapter 16 Seismic Provisions Seismic Hazard Zones: The site lies within a moderate liquefaction. hazard zone for shallow groundwater as established by the 2002 Riverside County General Plan. Riverside County has not been mapped by the California Seismic Hazard Mapping Act (Ca. PRC 2690 to 2699). EARTH SYSTEMS SOUTHWEST Reference Seismic Zone: 4 Figure 16-2 Seismic Zone Factor, Z: 0.4 Table 164 Soil Profile Type: SD Table 16-J Seismic Source Type: A Table 16-U Closest Distance to Known. Seismic ,Source: 12.7 km = 7.9 miles (San Andreas Fault) Near Source Factor, Na: 1.00 Table 16-S Near Source .Factor, Nv: 1.09 Table 16-T Seismic Coefficient, Ca: 0.44 = 0.44Na Table 16-Q Seismic Coefficient, Cv: 0.70 = 0.64Nv Table 16-R Seismic Hazard Zones: The site lies within a moderate liquefaction. hazard zone for shallow groundwater as established by the 2002 Riverside County General Plan. Riverside County has not been mapped by the California Seismic Hazard Mapping Act (Ca. PRC 2690 to 2699). EARTH SYSTEMS SOUTHWEST December 19, 2003 9 of 22 File No.: 09462-01 03-12-772 Section 4 CONCLUSIONS The following is a summary of our conclusions and professional opinions based on the data obtained from a review of selected technical literature and the site evaluation. General: ➢ From a geotechnical perspective; the site is suitable for the proposed development, provided the recommendations in this report are followed in the design and construction of this project. Geotechnical Constraints and Mitigation: ➢ The primary geologic hazard is severe groundshaking from earthquakes originating on nearby faults. A major earthquake above magnitude 7 originating on the local segment of the San Andreas Fault zone would be the critical seismic event that may affect the site within the design life of the proposed development. Engineered design and earthquake - resistant construction increase safety and allow development of seismic areas. ➢ The project site. is in seismic Zone 4, is of soil profile Type SD; and is about 12.7 km from a Type A seismic source as defined in the :California 'Building Code. A qualified professional should design any permanent structure constructed on the site. The minimum seismic design should comply with the 2001 edition of the California Building. Code. ➢ Ground subsidence from seismic events or hydroconsolidation is a potential hazard in the Coachella Valley area. Adherence to the grading and, structural recommendations in this report should reduce potential settlement problems from seismic forces, heavy rainfall or irrigation, flooding, and the weight of the intended structures. ➢ The soils are .susceptible to wind and water erosion. Preventative measures to reduce seasonal flooding and erosion should be incorporated into site grading plans. Dust control should also be implemented during, construction. Site grading should be in strict. compliance with the requirements of the South Coast Air Quality Management District (SCAQMD). ➢ Other geologic hazards, including fault rupture, liquefaction, seismically induced flooding, and landslides, are considered low or negligible on this site. ➢ Based on blow count resistance, the upper soils were found to be medium dense to dense silty sands and sands and should be suitable in their present condition to support structures, fill, and hardscape. Some remedial grading and up to 23 feet of cut will be performed to established the proposed grades. ➢ The soils within the building and structural areas will require moisture conditioning, over -excavation, and recompaction to improve bearing capacity and reduce settlement from static loading. Soils can be readily cut by normal ,grading equipment. EARTH SYSTEMS SOUTHWEST December 19, 2003 10 of 22 File No.: 09462-01 03-12-772 The proposed temporary 1:1 cut slopes for construction of retaining walls -may require surficial stabilization. Several method ofsurficial stabilization are possible, some of which include laying the slope back to 1.5:1 or flatter and application of a commercial - grade liquid stabilizer such as EK35®, ENVIROTAC IIT"", or equivalent. To aide in the performance of these methods, the contractor should be advised to protect the slope from surcharge loading ,and slope traffic or other disturbance. EARTH SYSTEMS SOUTHWEST December 19, 2003 11 of 22 File No.: 09462-01 03-12-772 Section 5 RECOMMENDATIONS SITE DEVELOPMENT AND GRADING 5.1 Site Development— Grading A representative of Earth Systems Southwest (ESSW) should observe site clearing, grading, and the bottoms of excavations .before placing fill. Local variations in soil conditions may warrant increasing the depth of.recompaction and over -excavation. Clearing and Grubbing: At the start of site grading, existing vegetation, trees, large roots, pavements, foundations, non -engineered fill, trash, and abandoned underground utilities should be removed from the proposed building, structural, and pavement areas. The surface should be stripped of organic growth and removed from the construction area. Areas disturbed during clearing should be properly backfilled and compacted as described below. Dust control should also be implemented during construction. Site grading should be in strict compliance with the. requirements of the South Coast Air Quality Management District (SCAQMD). Building Pad Preparation: Due to the construction of a basement, resulting in non-uniform conditions of the supporting soils between the basement and the remainder of the structure, we recommend over -excavation and reeompaction of soils in the basement area. The basement should be over -excavated to a depth of 2 feet below the proposed bottom of the footings. The resulting surface should be scarified, moisture conditioned, and compacted to a minimum of 90% relative compaction.. If remnants of the pre-existing date grove or other deleterious .material are encountered, additional. excavation will be required to expose clean native soil. Previously removed soils, once cleaned of deleterious material, may be placed in thin (6- to 8 -inch) lifts and compacted to at least 90% relative compaction. The surface soils within the remainder of the building pad and foundation areas should be trenched and the resulting footing bottoms tested for isolatedsoft areas. If soft areas are encountered, supplemental corimpactive effort will be required to provide at least 2 feet of compacted soil beneath the bottom of the footings. Soft Subgrade Condition: Depending upon the time of year that grading takes place and the effects of past irrigation schedules, moisture conditions may be sufficiently high to make compaction at the bottom of the basement over -excavation difficult or not feasible. If this condition exists at the time of grading, one of the following methods of treatment may be used once the recommended over -excavation has been made: • Soil may be scarified and aerated to reduce the moisture content to near the optimum moisture content so that the desired compaction can be achieved. • Soil may be blended with drier soil to reduce the in-situ moisture content sufficiently to allow compaction. EARTH SYSTEMS SOUTHWEST December 19, 2003 12 of 22 File No.: 09462-01 03-12-772 • The soils may be over-excavated an additional 6 to 8 inches. Gravel (1" to 3") may be placed in thin layers (3" to 4") and "track walked" or "punched" into the underlying soil. This process should be repeated until a stable surface has been achieved. • The soil may be over-excavated an additional 6 to 8 inches. A geotextile fabric may be placed to facilitate placement of the proposed fill. Specific recommendations for this alternative may be provided upon request. Actual design is a function of soil conditions at the time of grading. • Wet and unstable soils may be stabilized by air-drying or by utilizing an additive such as lime or cement. Actual design is a function of soil conditions at the time of grading. • Soils may be over_excavated an additional 12 to 18 inches and replaced with drier soil and compacted toa minimum of 90% of maximum dry density. Auxiliary Structures Subgrade Preparation: - Auxiliary structures such as garden or retaining walls should have the foundation subgrade prepared similar to the building pad recommendations given above. The lateral extent of the over-excavation needs to extend only 2 feet beyond the face of the footing. Subgrade Preparation: In areas to receive fill, pavements, or hardscape, the subgrade should be scarified, moisture conditioned, and compacted to at least 90% relative compaction (ASTM D 1557) for a depth of 1 foot, below finished subgrades. Compaction should be verified by testing. Engineered Fill Soils: The native soil is suitable for use as engineeredfill and utility trench backfill, provided it is free of significant organic or deleterious matter. The native soil should be placed in maximum 8-inch lifts (loose) and compacted to at least 90% relative compaction (ASTM D 1.557) near its optimum moisture content. Compaction should be verified by testing. Rocks larger than 6 inches in greatest dimension should be removed from fill or backfill material. Imported fill soils (if needed) should be non-expansive; granular soils meeting the USCS classifications of SM, SP-SM, or SW-SM with a maximum rock size of 3 inches and 5 to 35% passing the No. 200 sieve. The geotechnical engineer should evaluate the import fill soils before hauling to the site. However, because of the potential variations within the borrow source, import soil will not be, prequalified by ES.SW. The imported fill should, be placed in lifts no greater than 8 inches in loose thickness and compacted to at least 90% relative compaction (ASTM D 1557) near optimum moisture content. Shrinkage: The shrinkage factor for earthwork is expected to range from 15 to 20 percent for the lower soils located below the basement. The upper, previously compacted soils are anticipated to shrink less than 5 percent. This estimate is based on compactive effort to achieve an average relative compaction of about 92% and may vary with contractor methods. Subsidence is estimated to range from 0.1 to 0.2 feet. Losses from site clearing and removal of existing site improvements may affect earthwork quantity calculations and should be considered. EARTH SYSTEMS SOUTHWEST December 19, 2003 13 of 22 File No.: 09462-01 03-12-772 Site Drainage: Positive drainage should be maintained away from the structures (5% for 5 feet minimum) to prevent ponding and subsequent saturation of the foundation soils. Gutters and downspouts should be considered as a means to convey water away from foundations if adequate drainage, is not provided. Drainage should be maintained for paved areas. Water should not pond on or near paved areas. 5.2 Excavations and Utility Trenches Excavations should be made in accordance with CaIOSHA requirements. Our site exploration and knowledge of the general area indicates there is a potential for caving of site excavations (utilities, footings, etc.). Excavations within sandy soil should be kept moist, but not saturated, to reduce the potential of caving or sloughing. Where excavations over 4 feet deep are planned, lateral bracing or appropriate cut slopes of 1.5:.1 (horizontal:vertical) should be provided. No surcharge loads from stockpiled soils or construction materials should be allowed, within a horizontal distance equal to the depth of the excavation, measured from the top of the excavation slope. Utility Trenches: Backfill of utilities within roads or public right-of-ways should be placed in conformance with the requirements of the governing agency (water district, public works department, etc.). Utility trench backfill within private property should be placed in. conformance with the provisions of this report. In general, service lines extending inside of property may be backfilled with native soils compacted to a minimum of 90% relative compaction. Backfill operations should be observed and tested to monitor compliance with these recommendations. 5.3 Slope Stability of Graded Slopes The proposed temporary 1.:1 cut slopes for construction of retaining walls may require surficial stabilization. Several method of surficial stabilization are possible, some of which include laying the slope back to 1.5:1 or flatter and application of a commercial -grade liquid stabilizer such as EK35®, ENVIROTAC IITM' or equivalent. Thecontractor should be advised to protect the slope from surcharge loading and slope traffic or other disturbance to aide in the performance of these methods. Unprotected, permanent graded slopes should not be steeper than 3:1 (horizontal:vertical) to reduce wind and rain erosion. Protected slopes with ground cover may be as steep as 2:1. However,. maintenance with motorized equipment may not be possible at this inclination. Fill slopes should be overfilled and trimmed back to competent material. Slope stability calculations are not presented because of the expected minimal slope heights (less than. 5 feet). STRUCTURES In our professional opinion, structure foundations can be supported on shallow foundations bearing on a zone of properly prepared and compacted soils placed as recommended in Section 5.1. The recommendations that follow are based on very low expansion category soils. EARTH SYSTEMS SOUTHWEST December 19, 2003 14 of 22. File No.: 09462-01 03-12-772 5.4 Foundations Footing design of widths, depths, and reinforcing are the responsibility of the Structural Engineer, considering the structural loading and the geotechnical parameters given in this report. A minimum footing depth of 12 inches below lowest adjacent grade should be maintained. A representative of ESSW should observe foundation excavations before placement of reinforcing steel or concrete. Loose soil or construction debris should be removed from footing excavations before placement of concrete. Conventional Spread Foundations: Allowable soil bearing pressures are given below for foundations bearing on recompacted soils as described in Section 5.:1. Allowable bearing pressures are net (weight of footing and soil surcharge may be .neglected). ➢ Continuous wall foundations, 12 -inch minimum width and 12 inches below grade: 1500 psf for dead plus design live loads Allowable increases of 300 psf per each foot of additional footing width and 300 psf for each additional 0.5 foot of footing depth may be used up to a maximum value of 3000 psf. ➢ Isolated pad foundations, 2 x 2 foot minimum in plan and 1.8 inches below grade: 2000 psf for dead plus design live loads Allowable increases of 200 psf per each foot of additional footing width :and 400 psf for each additional 0.5 foot of footing depth may be used up to a maximum value of 3000 psf. A one-third (%3) increase in the bearing pressure may be used when calculating resistance to wind or seismic loads. The allowable bearing values indicated are based on the anticipated maximum loads stated in. Section 1.1 of this report. If the, anticipated loads exceed these values, the geotechnical engineer must reevaluate the allowable bearing values and the grading requirements. Minimum reinforcement for continuous wall footings should be two, No. 4 steel reinforcing bars,. one placed near the top and 'one placed near the bottom of the footing. This reinforcing is not intended to supersede any structural requirements provided by the structural engineer. Retaining Wall Foundations: A net allowable soil bearing pressure of 2000 psf may be used. No additional increases in bearing pressures are permitted for the retaining walls. Expected Settlement: Estimated total static settlement should be less than 1 inch, based on footings founded on firm soils as recommended. Differential settlement between exterior and interior bearing members should be less than % inch, expressed in a post,construction angular distortion ratio of 1:480 or less. Frictional and Lateral Coefficients: Lateral loads may be resisted by soil friction on the base of foundations and by passive resistance of the soils acting on foundation walls. An allowable coefficient of friction of 0.35 of dead load may be used. An allowable passive equivalent fluid pressure of 250 pcf may also be used. These values include a factor of safety of 1.5. Passive resistance and frictional resistance may be used in combination if the friction coefficient .is reduced by one-third. A one-third ('/3) increase in the passive pressure may be used when EARTH SYSTEMS SOUTHWEST December 19, 2003 15 of 22 File No.:. 09462-01 03-1.2-772 calculating resistance to wind or seismic loads. .Lateral passive resistance is based on the assumption that backfill next to foundations is properly compacted. 5.5 Slabs -on -Grade Subade; Concrete slabs -on -grade and flatwork should be supported by compacted soil placed in accordance with Section 5.1 of this report. Vapor Retarder: In areas of moisture sensitive floor coverings, an appropriate vapor retarder should be installed to reduce moisture transmission from the subgrade soil to the slab. For these areas, an impermeable membrane (1:0 -mil thickness) should underlie the floor slabs. The membrane should be covered with,2 inches of sand to help protect it during construction and to aid in concrete curing. The sand should be lightly moistened just prior to placing the concrete. Low -slump concrete should be used to help reduce the potential for concrete, shrinkage. The effectiveness of the membrane is dependent upon its quality, the method of overlapping, its protection during construction, and the successful sealing of the membrane around utility lines. The basement walls should be adequately waterproofed to prevent water and moisture vapor from entering into this subterranean habitable living space. This includes the underside of foundations and floor slabs. Care should be taken during the backfilling and compaction operation around the basement so as not to damage the water/moisture vapor protective coating. Slab Thickness and Reinforcement: Slab thickness and reinforcement. of slabs -on -grade are contingent on the recommendations of the structural engineer or architect and the expansion. index of the supporting soil. Based upon our findings, a modulus of subgrade reaction of approximately 200 pounds per cubic inch can be used in concrete slab design for the expected very low expansion subgrade. Concrete slabs and flatwork should be a minimum of 4 inches thick (actual, not nominal). We suggest that the concrete slabs be reinforced at slab mid -height to resist cracking. Concrete floor slabs may either be monolithically placed with the foundations or doweled after footing placement. The thickness and reinforcing given are not intended to supersede any structural. requirements provided by the structural engineer. The project architect or geotechnical engineer should continually observe all reinforcing steel in slabs during placement of concrete to check for proper location within the slab. Control Joints: Control joints should be provided in all concrete slabs -on -grade at a maximum spacing of 36 times the slab thickness (12 feet maximum on -center, each way) as recommended by American Concrete Institute (ACI) guidelines. All joints should form approximately square patterns to reduce the potential for randomly oriented, contraction cracks. Contraction joints in the slabs should be, tooled at the time of the pour or saw cut ('/a of slab depth) within 8 hours of concrete placement. Construction (cold) joints should consist of thickened butt joints with one- half inch dowels at 18 -inches on center or a thickened keyed -joint to resist vertical. deflection at the joint. All construction joints in exterior flatwork should be sealed to reduce the potentialof moisture or foreign material intrusion. These procedures will reduce the potential for randomly, oriented cracks, but may not prevent them from occurring. EARTH SYSTEMS, SOUTHWEST December 19, 2003 16 of 22 File No.: 09462-01 03-12-772 Curing and Quality Control: The contractor should take precautions to reduce the potential of curling of slabs in this and desert region using proper batching, placement, and curing methods. Curing is highly affected by temperature, wind, and humidity. Quality control procedures may be used, including trial batch mix designs, batch plant inspection, and on-site special inspection and testing. Typically, for this type of construction and using 2500 -psi concrete, many of these quality control procedures are not required. 5.6 Retaining Walls The following table presents lateral earth pressures for use in retaining wall design. The values are given as equivalent fluid pressures without surcharge loads or hydrostatic pressure. Table 5.1 Lateral Pressures and Sliding Resistance t Granular Backfill Passive Pressure 350 pcf - level ound Active Pressure (cantilever walls) 30 pcf - level ground Use when wall is permitted to rotate,0.1% of wall height At -Rest Pressure (restrained walls) 45 pcf - level ground Dynamic Lateral Earth Pressure Acting at 0.5H, 18H psf Where H is height of backfill in feet Base Lateral Sliding Resistance 0.50 Dead load x Coefficient of Friction: Notes: 1. These values, are ultimate values. A factor of safety of 1.5 should be used in stability analysis except for dynamic earth pressure wherea factor of safety of 1.2 is acceptable. 2. Dynamic pressures are based on the Mononobe-Okabe 1929 method, additive to active earth pressure. Walls retaining less than 6 feet of soil and not.supporting inhabitable structures need not consider this increased pressure (reference: CBC Section 1630A. 1. 1.5). Upward sloping backfill or surcharge loads from nearby footings can create larger lateral pressures. Should any walls be considered for retaining sloped backfill or placed next to foundations, our office should be contacted for recommended design parameters. Surcharge loads should be considered if they exist within a zone between the face of the wall and a plane projected 45 degrees upward from the base of the wall. The increase in lateral earth pressure should be taken as 35% of the surcharge load within this zone. Retaining walls subjected to traffic loads should include a uniform surcharge load equivalent to at least 2 feet of native soil. Drainage: A backdrain or an equivalent system of backfill drainage should be incorporated into the retaining wall design. Our firm can provide construction details when the specific application is determined. Backfill immediately behind the ,retaining structure should be a free -draining granular material. Waterproofing should be according. to the designer's specifications. Water should not be allowed to pond near the top of the wall. To accomplish this, the final backfill grade should be such that all water is diverted away from the retaining wall. Backfill and Subgrade Compaction: Compaction on the retained side of °the wall within a horizontal distance equal to one wall height should be performed by hand -operated or other EARTH SYSTEMS SOUTHWEST December 19, 2003 17 of 22 File No.: 09462-01 03-12-772 lightweight compaction equipment. This is intended to reduce potential - locked -in lateral pressures caused by compaction with heavy grading equipment. Foundation subgrade preparation should be as specified in Section 5.1. 5.7 Mitigation of Soil Corrosivity on Concrete, Chemical analyses for corrosivity performed on soil samples at other sites in the vicinity of the subject. site suggest low sulfate ion concentration and .low chloride ion concentration. Sulfate ions can attack the cementitious material in concrete, causing weakening of the cement matrix and eventual deterioration by raveling. Chloride ions can cause corrosion of reinforcing steel. The California Building Code does not require any special provisions for concrete for low concentrations as tested. Normal concrete mixes may be used. A minimum concrete cover of three (3) inches should be provided around steel reinforcing or embedded components exposed to native soil or landscape water. Additionally, the concrete should be thoroughly vibrated during placement. Electrical resistivity testing of the soil suggests that the site soils may present a moderate to severe potential for metal loss from electrochemical corrosion processes. Corrosion protection of steel can be achieved by using epoxy corrosion inhibitors, asphalt coatings, cathodic protection, or encapsulating with densely consolidated concrete. Earth Systems does not practice corrosion engineering. We recommend that a qualified corrosion engineer evaluate the corrosion potential on metal construction materials and concrete at the site to provide mitigation. of corrosive effects. 5.8 Seismic Design Criteria This site is subject to strong groundshaking due to potential fault movements along the San Andreas and San Jacinto Faults. Engineered design and earthquake -resistant construction increase safety and allow development of seismic areas. The minimum seismic design should comply with the 2001 edition of the California Building Code using the seismic coefficients given in the table below. Table 5.2. 2001 CBC Seismic Coefficients for Chapter 16 Seismic Provisions Seismic Zone: 4 Seismic Zone Factor, Z: 0.4 Soil Profile Type: SD Seismic Source Type: A Closest Distance to Known Seismic Source: 12.7 km = 7.9 miles Near Source Factor, Na: 1.00 Near Source Factor, Nv: 1.09 Seismic Coefficient, Ca: 0.44 = 0.44Na Seismic Coefficient, Cv: 0.70 = 0.64Nv EARTH SYSTEMS SOUTHWEST R Pf-rPnrP. Figure 1.6-2 Table 16-I Table 16-J Table 16-U (San Andreas Fault) Table 16-S Table 16-T Table 16-Q Table 16-R December 19, 2003 18 of 22 File No.: 09462-01 03-12-772 The CBC seismic coefficients are based. on scientific knowledge, engineering judgment, and compromise. If further information on seismic design is needed, a site-specific probabilistic seismic analysis should be conducted. The intent of the CBG lateral force requirements is to provide a structural. design that will resist collapse to provide reasonable life safety from a major earthquake, but may experience some structural and nonstructural damage. A fundamental tenet of seismic design is that inelastic yielding is allowed to adapt to the, seismic demand on the structure. In other words, damage is allowed. The CBC lateral force .requirements should be considered a minimum design. The Owner and the designer should evaluate the level of risk and, performance that is acceptable. Performance based criteria could be set in the design. The design engineer should exercise special care so than all components of the design are all fully met with attention to providing a continuous load path. An adequate quality assurance and control program is urged during project construction to verify that the design plans and good construction practices are followed. This is especially important for sites lying close to the major seismic sources. 5.9 Pavements Since no traffic loading was provided by the design engineer or owner, we have assumed traffic loading for comparative evaluation. The design engineer or owner should decide the appropriate traffic conditions for the pavements. Maintenance of proper drainage is advised to prolong the service life of the pavements. Water should not pond on or near paved areas. The following table provides our preliminary recommendations for pavement sections. Final pavement sections recommendations should be based on design traffic indices and R -value tests conducted during_ grading after actual subgrade soils are exposed. Table 5.3 PRELIMINARY RECOMMENDED PAVEMENTS SECTIONS lc- value auvgraae Sobs - 30 tassumea Design nnemoa — CAL IRAN b 1995 Flexible Pavements Rigid Pavements Traffic Asphaltic Aggregate Portland Aggregate Index Pavement Use Concrete Base Cement Base (Assumed) Thickness Thickness Concrete Thickness (Inches) (Inches) (Inches) (Inches) 4.5 Auto Parking Areas 2.5 4.0 4.0 4.0 5.0 J Residential Streets 3.0 4.0 5.0 4.0 Notes: 1. Asphaltic concrete should be Caltrans, Type 13, '/rin. or -%-in. maximum -medium grading and compacted to a minimum of 95% of the 75 -blow Marshall density (ASTM D 1.559) or equivalent. 2. Aggregate base should be Caltrans Class 2 (% in. maximum) and compacted to a minimum of 95% of ASTM D1557 maximum dry, density near its optimum moisture. 3. All pavements should be.placed on 12 inches of moisture -conditioned subgrade, compacted to a minimum. of 90% of ASTM D 1557 maximum dry density near its optimum moisture. 4. Portland cement concrete should have a minimum of 3250 psi compressive strength at 28 days. 5. Equivalent. Standard Specifications for Public Works Construction (Greenbook) maybe used instead of Caltrans specifications for asphaltic concrete and aggregate base. EARTH SYSTEMS SOUTHWEST December 19, 2003 19 of 22 File No.: 09462-01 03-12-772 Section 6 LIMITATIONS AND ADDITIONAL SERVICES 6.1 Uniformity of Conditions and Limitations Our findings and .recommendations in this report are based on selected points of field exploration, laboratory testing, and our understanding of the proposed project. Furthermore, our findings and recommendations are based on the assumption that soil conditions do not vary significantly from those found at specific exploratory locations. Variations in soil or groundwater conditions could exist between and beyond the exploration points. The nature and extent of these variations may not become evident until construction. Variations in soil or groundwater may require additional studies, consultation, and possible revisions to 'our recommendations. Findings of this report are valid as of the issued date of the report. However, changes in conditions of a property can occur with passage of time, whether they are from natural processes or works of man, on this or adjoining properties. In addition, changes in applicable standards occur, whether they result from legislation or broadening of knowledge. Accordingly, findings of this report may be invalidated wholly or partially by changes outside our control. Therefore, this report is subject to review and should not be relied upon after a period of one year. In the event that any changes in the nature, design, or location of structures are planned, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and the conclusions of this report are modified or verified in writing. This report is issued with the understanding that the owner or the owner's representative has the responsibility to bring the information and recommendations contained herein to the attention of the architect and engineers for the project so, that they are incorporated into the plans and specifications for the project. The owner or the owner's representative also has the responsibility to verify that the general contractor and all subcontractors follow such recommendations. It is further understood that the owner or the owner's representative is responsible for submittal of this report to the appropriate governing agencies. As the Geotechnical. Engineer of Record for this project, Earth Systems Southwest (ESSW) has striven to provide our services in accordance with generally accepted geotechnical engineering practices in this locality at this time. No warranty or guarantee is express or implied. This report was prepared for the exclusive use of the Client and the Client's authorized agents. ESSW should be provided the opportunity for a general review of final design and specifications in order that earthwork and foundation recommendations may be properly interpreted and implemented in the design and specifications. If ESSW is not accorded the privilege of making this recommended review, we can assume no responsibility for misinterpretation of our recommendations. Although available through ESSW, the current scope of our services does not. include an environmental assessment or an investigation for the presence or absence of wetlands, hazardous EARTH SYSTEMS, SOUTHWEST December 19, 2003 20 of 22 File No.: 09462-01 03-12-772 or toxic materials in the soil, surface water, groundwater, or air on, below, or adjacent to the subject property. 6.2 Additional Services. This report is based on the assumption that an adequate: program of client consultation, construction monitoring, and testing will be performed during the final design and construction phases to check compliance with these recommendations. Maintaining ESSW as the geotechnical consultant from beginning to end of the project will provide continuity of services. The geotechnical engineering firm providing tests and observations shall assume the. responsibility of Geotechnical Engineer of Record. Construction monitoring and testing would be additional services provided by our firm. The costs of these services are not included in our present fee arrangements, but can be obtained from our office. 'The recommended review, tests, and observations include, but are not necessarily limited to the following: • Consultation during the final design stages of the project. • Review of the building and grading plans to observe that recommendations of our report have been properly implemented into the design. • Observation and testing during site preparation, grading, and placement of engineered fill as required by CBC Sections 1701 and 3317 or local grading ordinances. • Consultation as needed during construction. e Appendices as cited are attached and complete this report. EARTH SYSTEMS SOUTHWEST December 19, 2003 21 of 22 File No.: 09462-01 03-12-772 REFERENCES Abrahamson, N., and Shedlock, K., editors, 1997, .Ground motion attenuation relationships: Seismological Research.Letters, v. 68, no. 1, January, 1997 special issue, 256 p. American Concrete Institute (ACI), 1996, ACI Manual of Concrete: Practice, Parts 1 through 5. Blake, T.F., 2000, FRISKSP v. 4.00, A Computer Program for the Probabilistic Estimation of Peak Acceleration and Uniform Hazard Spectra Using 3-D Faults as Earthquake Sources, Users Manual. California Geologic Survey (CGS), 1997, Guidelines for Evaluating and Mitigating Seismic Hazards in California, Special Publication 117. Cao, T, Bryant, W.A., Rowhandel, B., Branum. D., and Wills, C., 2003, The Revised 2002 California Probabilistic Seismic Hazard Maps, California Geologic Survey (CGS), June 2003. California Department of Water Resources, 1964, Coachella Valley Investigation, Bulletin No. 108, 146 pp. Envicom Corporation and the County of Riverside Planning Department, 1976, Seismic Safety and Safety General Plan Elements Technical Report, County of Riverside. Frankel, A.D.., et. al, 2002, Documentation for the 2002 Update of the National Seismic Hazard Maps, USGS Open -File Report 02-420. Hart, E.W., 1997, Fault -Rupture Hazard Zones in California: California Division of Mines and Geology Special Publication 42. International Code Council (ICC), 2002, California Building Code, 2,001 Edition. International, Code Council (ICC), 2003, International Building Code, 2003 Edition. Jennings, C.W, 1994, Fault Activity Map of California and Adjacent Areas: California Division of Mines and Geology, Geological Data Map No. 6, scale 1:750,000. Petersen, M.D., Bryant, W.A., Cramer, C.H., Cao, T., Reichle, M.S.,, Frankel, A.D., Leinkaemper, J.J., McCrory, P.A.., and Schwarz, D.P.,,1996, Probabilistic Seismic Hazard Assessment for the State of California: California Division of Mines and Geology Open -File Report 96-08. Proctor, R. J., 1968, Geology of the Desert Hot Springs - Upper Coachella Valley Area, California Division of Mines and Geology, DMG Special Report 94. Reichard, E.G. and Mead, J.K., 1991,.Evaluation of a Groundwater Flow and Transport Model of the Upper Coachella Valley, California, U.S.G.S. Open -File Report 91-4142. EARTH SYSTEMS SOUTHWEST December 19, 2003 22 of 22 File No.: 09462-01 03-12-772 Riverside County Planning Department, 2002, Geotechnical Element of the Riverside County General Plan — Hearing Draft. Rogers, T.H., 1966, Geologic Map of California - Santa Ana Sheet, California Division of Mines and Geology Regional Map Series, scale 1:250,000. Structural Engineers Association of California (SEAOC), 1996, Recommended Lateral Force Requirements and Commentary. Tokimatsu, K, and Seed, H.B., 1987, Evaluation of Settlements in Sands Due To Earthquake Shaking, ASCE, Journal of Geotechnical Engineering, Vol. 113, No. 8, August 1987. Working Group on California Earthquake Probabilities, 1995, Seismic Hazards in Southern California: Probable Earthquakes, 1994-2024: Bulletin of the Seismological Society of America, Vol. 85, No. 2, pp. 379-439. Wallace, R. E., 1990, The San Andreas Fault System, California: U.S.: Geological Survey Professional Paper 1515, 283 p. EARTH SYSTEMS SOUTHWEST APPENDIX A Site and Boring Location Map Table 1 — Fault Parameters 2001 California Building Code (CBC) Seismic Parameters Logs of CPT Soundings EARTH SYSTEMS SOUTHWEST venue 52 MW H 4: y s J �O->or.T CPT t , .000 r.. CPT -2' CPT -3, y 60"ote Canyon ourt. .. Mai .,." ., a Ak o} . . @ 200 (31 o bei : I w -m r , Ai rPh tc,U -S.H. � .. xt 78-370 Coyote Canyon Court 09462-01 Table 1 Fault Parameters & Deterministic Estimates of Mean Peak Ground Acceleration (PGA) Fault Name or Seismic Zone Distance from Site (mi) (km) Fault Type Maximum Magnitude Mmax (Mw Avg. slip Rate (mm/yr) Avg Return Period (Yrs). Fault Length (km) Mean Site PGA (g) Reference Notes: 1 2 3 4 2 2 2 5 San Andreas - Southern 7.9 12.7 SS A 7.7 24 220 199 0.38 San.Andreas- Mission Crk. Branch 8.3 13.4 SS A 7.2 25 220 95 0.30 San Andreas -Banning Branch 8.3 13.4 SS A 7.2 10 220 98 0.30 San.Jacinto (Hot Spgs - Buck Ridge) 14.6 23.5 SS C 6:5 2 354 70 0.14 Blue Cut 16.6 26.6 SS C 6.8 1 760 30 0.14 San Jacinto -Anna 18.9 30.5 SS A 7.2 12 250 91 0.15 San Jacinto -Coyote Creek 19.4 31.2 SS B 6.8 4 175 41 0.12 Burnt Mtn. 19.4 31.2 SS B 6:5 0.6 5000 21 0.10 Eureka Peak 20.5 33.0 SS B 6.4 0.6 5000 19 0.09 Morongo 30.2 48.6 SS C 6.5 0.6 1170 23 0.07 Pinto Mountain 31.9 51.3 SS B 7.2 2.5 499 74 0.09 San Jacinto - Borrego 33.1 53.3 SS B 6.6 4 175 29 0.06 Emerson So.. - Copper Mtn. 34.1 55.0 SS B 7.0 0.6 5000 54 0.08 Landers 34.6 55:7 SS B 7.3 0.6 5000 83 0.09 San Jacinto -San Jacinto Valley 35.9 57.8 SS B 6.9 12 83 43 0.07 Pisgah -Bullion Mtn: -Mesquite Lk 36.2 58.3 SS B 7.3 0.6 5000 89 0.09 Earthquake Valley 37.6 60.5 SS B 6.5 2 351, 20 0.05 North Frontal Fault.Zone (East) 40.4 65.0 DS B 6.7 0.5 1727 27 0.07 Brawley Seismic Zone 40.7 65.5 SS B 6.4 25 24 42 0.05 Elsinore -Julian 41.7 67.1 SS A 7.1 5 340 76 0.07 Johnson Valley (Northern) 45.4 73.1, SS B &7 0.6 5000 35 0.05 Elsinore -Temecula 46.0 74.0 SS B 6.8 5 240 43 0.05 Calico - Hidalgo 47.4 76.3 SS B 7.3 0.6 5000 95 0.07 Elmore Ranch 48.7 78.3 SS B 6.6 1 225 29 0.04 Elsinore -Coyote Mountain 49.0 78.8 SS B 6.8 4 625 39 0.05 Lenwood-Lockhart-Old Woman Sprgs 50.9 81:9 SS B 7.5 0.6 5000 145 0.07 North Frontal Fault Zone (West) 51.0 82.1 DS B 7.2 1 1314 50. 0.07 Superstition Mtn. (San Jacinto) 51.6 83.1 SS B 6.6 5 .5.0.0 24 0.04 Superstition Hills (San Jacinto) 52.6 84.7 SS B 6.6 4 250 23 0.04 Helendale - S. Lockhardt 58.3 93.9 SS B 7.3 0.6 . 5000 97 0.05 San Jacinto -San Bernardino 58.9 94.8 SS B 6.7 12 100 36 0.64 Elsinore -Glen Ivy 60.4 97:3 SS B 6.8 S 340 36 0.04 Notes: 1. Jennings (1994) and California Geologic Survey (CGS):(2003) 2. CGS (2003), S&= Strike -Slip, DS = Dip Slip, BT = Blind Thrust 3. 2001 CBC, where Type A faults: Mmax > 7 &.slip rate >5 mm/yr & Type C faults: !Mmax <6.5 & slip rate < 2 mmlyr 4. CGS (2003) 5. The estimates of the mean Site PGA are based on the.following attenuation relationships: Average oft (1) 1997 Boore, Joyner & Fumal;,(2) 1.99.7 Sadigh et al; (3) 1997 Campbell, (4) 1997 Abrahamson,& Silva (mean plus sigma values are about 1.5 to 1.6 times higher) Based on Site Coordinates:.33.672 N Latitude, 116.297 W Longtude and Site Soil Type, EARTH SYSTEMS SOUTHWEST Project Name:. 78-370 Coyote Canyon Court File No.: " 09462-01. 2001 CALIFORNIA BUILDING CODE (1997 UBC) SEISMIC PARAMETERS Reference Seismic Zone: 4 Figure 16-2 Seismic.Zone, Factor: Z 0.4 Table 16-1 Soil Profile Type: S u Table 16-J Seismic Source Type:, A Table 16-0 Closest Distance to Known Seismic Source: 12.7 km = 7.9 miles Near Source Factor: Na 1.00 Table 16-S Near Source Factor: Nv 1.09 Table 1.6-T Seismic Coefficient: Ca 0.44 = 0.44Na Table 16-Q Seismic Coefficient:: Cv 0.70 = 0.64Nv Table 16-R Closest Signficant Seismic Fault Source: San Andreas - Southern To: 0. 13 sec Ts: 0.64 sec EARTH SYSTEMS SOUTHWEST Period Sa CBC (1997 UBC) Equivalent Static Response Spectrum 2001 T sec 0.00 0.44 i 12 I 0.05 0.70 i I I i i ' 0.13 1.10 1.0 I I I 0.64 1.10 0.70 1.00 0.80 0.87 co 0:8 I I i I 0.90 0.78 o 1.00 0.70 c` j i 1.20 0.58 I I i I I j i 0.6 1.40 0.50 I i I 1.60 0.44 1.80 0.39 0.4 i i 2.00 0:35 ami I i I i I i I 2.20 0.32 co 2.40 029 ! 0.2 I 2.60 0.27 I I i 2.80 0.?5 I ' El i 3.00 0.23 0.0 3.20 0.22. 0.0 0.5 1.0 1.5 2.0 3.40 0:21 Period (sec) EARTH SYSTEMS SOUTHWEST ' v z CPT o: CPT -1 CPT Vendor: HFA Project Name: 78-370 Coyote Canyon Court Truck Mounted Electric Project No.: 09462-04 Cone with 23 -ton reaction Location: See Site Exploration Plan Date: 12/19/2003 a w Friction Ratio (9'0) Tip Reslatanc%.Qc (tsq Graphic.Log (SBT) Interpreted Soil Stratigraphy 8 6 4 2 0 ' 40 80 120 160 200 240 0 12 Robertson &,Campanella ('89) Density/Consistency Sandy Silt to'Clayey Silt medium dense Sand to Silty Sand very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Sand to Clayey Sand very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Sandy Silt to Clayey Silt dense Clayey Silt to Silty Clay hard Silty Clay to Clay very stiff Silty Clay to Clay hard Clayey Silt to Silty Clay hard Sandy Silt to Clayey Silt medium dense Clayey Silt to Silty Clay hard Clayey Silt to. Silty Clay hard Clayey Silt to Silty Clay hard Clayey Silt to. Silty Clay hard Clayey Silt to SiltyClay hard Clayey Silt to Silty Clay hard Clayey Silt to Silty Clay hard Silty Clay to Clay hard Clay hard Clay very stiff Clay very stiff Clay very stiff End of Sounding c@ 30:2 feet I I 11 i 1 I 1 1 1 1 1 1 1 1111111 1 1 1 1 1 1 1 1 1 1 1 1 II I I I I I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1111111 I I I I I I I I I I I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 IIIII. 1 1 1 1 1 1 1 1 1 1 1 I I I I I I I I I 1 1 11111111111 1 I I I I 1 1 1 1 1 1 111111,I,III 1111111111 �. ,1111'111111 11111111111 11111111111 1111111'1111 1111111 bI PI '1111 I'I IIIII 11 I I I I I I I I Y 1111111111 I I I I I I I I I 1 1 1111111111,1 I I I I I I I I I I I I I I I I I I I I I I I1 ILIIIIII 111111 11111 I I II I I I I 'I 1 1 111111'1 I'I 11 IIIIIIII'I I'1 I I I I I I I 1 1 1 1 I I I I I I I I I I I IIIIIII1111 IIIIIIII111 5 10 20 251 30 35 40 . 45 50 Earth -- LU' LL z CPT No: CPT -2 CPT Vendor: HFA Project Name: 78-370 Coyote Canyon Court Truck Mounted Electric Project No.: 09462-01 Cone with 23 -ton reaction Location: See Site Exploration Plan Date: 12/19/2003 d G Friction Ratio (%) Tip Resistance, Qc (tst) Graphic Log (SBT) Interpreted Soil Stratigraphy g 6 4 2 0 40 80 120 160 200 240 0. 12 Robertson & Campanella ('89) Density/Consistency Sand oI an verydense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very, dense Silty Sand to Sandy Silt very, dense Sandy Silt to Clayey Silt very dense Sand to Clayey Sand verydense Sandy Silt to Clayey Silt very -dense Clayey Silt to Silty Clay hard Clayey Silt to Silty Clay hard Silty Clay to Clay very stiff Silty Clay to, Clay very.stiff Silty Clay to Clay very stiff Clayey Silt to Silty Clay hard Sandy Silt to Clayey Silt medium dense Clayey Silt to Silty Clay hard End of Sounding @ 20.0 feet ;III -! 1 1 1 1 1 1 I l t l l l 11 1111 11i 1111 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ( I I I I I I I I I I I l l l l l l t l l l ( I I I I I I I I I I I I I I I I I I I 11' ( I I I I I I I I I I ( I I I I I I I I I I 1 1 1 1 1 1 1 1 1 1 1 I11111iI�1I' II I I I I I I I I I I JillI 1 1 1 I 1 1 1 11 1 1 1 1 1 1 I I I I I I I I 1 1 1 1 1 1 ( I I II I I I I I I Ii1111I111I I I I I I I �I I I I I 1111I��I I'II I, I I; 1; 1 1 I 1 I 1 1 1 1l 1 1 1.I I I I I I11111IIIII I I I I I I I I I I I I I I I I I I I I 1 1 1 1 1 1 1 1 1 1 1 I I I I I I I I I I I I I I 1 1 1 1 1 1 1 ( I I I I I I I I I I IIII111IIII I l t l l l l l l l l 1 1 1 1 1 1 1 1 1 1 1 ( I I I I I I I I I I 1 1 1 1 1 1 1 1 1 1 1 I I I I I I I I I 1 1 ( I I I I I I I I I I 1 1 1 1 1 1 1 1 1 1 1 I l l l t l l l 1 I I 1111111111 1 1 1 1 1 1 1 1 1 1 1 1.1111111I'II 1 1 1 1 1 II 11 I I 1 I l l l t l l l l l l ( I I I I I I I I I I IIIIIIIIII I. 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 111.1111111 I I I 1 1 1 1 1 1 1 1 111 I'I 1:11111 11111111111 11111111111 11111111111' I I I I I I I I I I 5 10 15 :IT Z0 L _25 30 35 40 45 50 W' U z CPT No: CPT -3 CPT Vendor: HFA Project Name: 78-370 Coyote Canyon Court Truck. Mounted Electric Project No.: 09462-01 Cone with 23 -ton reaction Location:_ See Site Exploration Pian Date: 12/19/2003 4. WG Friction Ratio (%) Tip Resistance, Qc (tst) Graphic Log (SBT) Interpreted Soil Stratigraphy 8 6 4 2 0 40 80 120 160 .200 240 0 12 Robertson .& Campanella ('89) Density/Consistency Siltyan o any Silt, medium dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Silty Sand to Sandy Silt very dense Sand to Clayey Sand very dense Sand to Clayey Sand very dense Sandy -Silt to Clayey Silt dense Clayey Silt to Silty Clay hard Clayey Silt to Silty Clay hard Clayey Silt to Silty Clay hard End of Sounding @ 15.3 feet I I I I I 1 1 1 1 1 1 I l t l l l 1 1 1 1 1 1 1 1 1 1 1 1 1 1 4 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 11 111111 I,I I'I1 I 11111 II III 1 1 1 1 1 1 I I I I I IY IIII I.IIII II IIII I,IIII IIiI�I 111111 IIII'I 111111 Illllflllll 111111 I I I ISI I�1 I I' 11 I I I I I 1 1 1 1 1 1 II IIIIIIIII I �I'IIIIIII.1i 1.1III 11111'1 I I I I I I I I i l l 1 1 1 1 1 1 1 1 1 1 1 III b.1111111 I I I I I I I I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1111111 I l t l I I I I I I I I I I I I I I I I I I I1'I111111 I.I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I II 1 1 1 1 1 1 1 1 1 1 1 I I I 1 1 1 1 1 1 1 I 1 1 1 1 1 1 1 1 1 1 1 I I I I I I I I 1 1 1 �I11111. I I.I� II111111111 I I I I I�I I I I I I �I11 I, �I IIII�I 1 II I I I I I I I I I I I 1 1 1 1 1 1 1 1 - 5 - -00 10 15 • 20 25 30 35 40 45 50