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BRES2019-0143 Geotechnical ReportVIQES Za BUILDING DIVISION REVIEWED FOR CODE COMPLIANCE F-tV if GEOTECHNICAL. ENGINEERING PREPARED FOR STUART ENTERPRISES, LTD. RECEIVED J(JN 2 6 2019 CITY OF LA QUINTA DESIGN AND DEVELOPMENT DEPARTMENT THIS OOCUMENT WAS ISSUED PREVIOUSLY AND MAY NOT REFLECT CURRENT SITE CONDITIONS ANWOH STANDARDS OF GEOTECHNICAL PRArT10E. THE CONTENITS OF THE Dt]=,,-f-NT S -IOLI' 1) 10T BE USED OR RELIED UPOP-! WITHOUT A REVIRV BY QUALIFIED PROFESSIONALS. (Init.) 1 (Pale) Y .• P' 7$ EARTH SYSTEMS CONSULTANTS B7-1405-P1 NOVEMBER 2, 1989 Buena Engineers, Inc. item a �.'/ AN EA1" 5Y=-MS.24. COMPAW 79-811 B COUNTRY CLUB DRIVE • BERMUDA DUNES, CALIFORNIA 92201 • PHONE (619) 345-1588 • FAX (619) 345-7315 November 2, 1989 Stuart Enterprises, Ltd. 9525 Wilshire Boulevard - Suite 611 Beverly Hills, California 90212 Attention: Woody Stewart Project: Desert Lake La Quinta, California Subject: Geotechnical Engineering Report 87-14.05-P1 89-10-831 Presented herewith is our Geotechnical Engineering Report prepared for the proposed residential development to be located in La O.uinta, California. This report incorporates the tentative information supplied to our office and in accordance with the request, recommendations for general site development and foundation design are provided. This report was prepared to stand as a whole, and no part of the report should be excerpted or used to exclusion of any other part. This report completes our scope of services in accordance with our agreement. Other services which may be required, such as plan review and grading observation are additional services and will he billed according to the Fee Schedule in effect at the time services are provided. Please contact the undersigned if there are any questions concerning this report or the recommendations included herein. Respectfully submitted, BUENA ENGINEERS, INC. rL R. Layne Richins Staff Geologist Revi ewed and 10.4 rc. y� a. C 041210 _ sn m .3-7i-91 � Joseph R. ` � i CNL Civil Engine OF CA Brett L. Anderson Project Engineer RLR/BLA/JRV/rcl HD/SER/Copies: 6 -Stuart Enterprises, Ltd. BERMUDA DUNES BAKERSFIELD LANCASTER I - P.S.File 1- VTAFile SAN LUIS OBISPO VENTURA TABLE OF CONTENTS INTRODUCTION.... ............ --------••---------------•---.,.._.....__------- 1 PURPOSE AND SCOPE OF WORK .......................................... ----------- -- 1 SITE DESCRIPTION -------•---------------------- - ------------------------------- FIELD EXPLORATION ---------------------------------------------------••----- -=- LA60RATORY TESTING.---•----- - -- - -- - ------------------------- SOILCONDITIONS----------------- -- ..----•----------------------......_.------------ 4 GROUNDWATER......... --............... ---------•-------=---------._---.....----- 4 REGIONAL GEOLOGY------------------ -- - -.... ------•-----------... ------------,...._ 5 LOCAL GEOLOGY---- -----•--------------- - -- -- --------- ---- •---- - -•-- Descriptive Geology ............................. --------------------------------------------- 5 StructuralGeology---------------------------------------------•------------------------•--- 6 GEOLOGIC HAZARDS---------------- --- ------ ------------ - -------....---------....._ 6 Primary.............................. -------------------------------------------------------------- 6 Secondary---------.•------------------------------------------------------------------------------ 8 Non -Seismic------ -••- CONCLUSIONS AND DISCUSSIONs-------------------------------------------------------- 9 SITE DEVELOPMENT AND GRADING ------------ -......................................... 10 Site Development - Grading ............................. -........... -.................... 1 1 Site Development - Slope Stability .................... ..................................... 13 Site Development - General---------------------........................................ 13 Excavations-------------------------------------------------------------------------------------- 15 TrafficAreas ------------------------------------------------------------------------------------ 15 Utility Trenches --_-------------- ---------- --------------------------------------------------- 17 STRUCTURES-------------------------------------------------- ----------------------------------------- Fottndations--------------------------------------------------------------------------------------- 17 Slabs -on -Grade---------------- ----- .- ----.....-------------------_..---------------- 10 Settlement Considerations --------------------------------------------------------------- 19 Frictional and Lateral Coefficients -----------------••-------.._--------....-•--__--- 19 Expansion ------------------------------ ------------------------------------------------------ ------ 20 Additional Services ------------------------------------------------- ................... 20 LIMITATIONS AND UNIFORMITY OF CONDITIONS ------------------------- :...... 21 REFERENCES---------------------------------- -------------------------=-----------------__ _-------- 23 APPENDIX A Site and Vicinity Map Logs of Borings APPENDIX B Summary of Test Results Tattle 29-A APPENDIX C Standard Grading Specifications November 2, 1989 INTRODUCTION 87-1405-P 1 69-10-831 This Geotechnical Engineering Report has been prepared for the proposed residential development to be located in La Quinta, California. A. It is assumed the proposed residential structures will be of lightweight one (1) or two (2) story construction. It is also assumed that the buildings will be supported by normal continuous or pad footings. B. Structural considerations for residential column loads of up to 20 kips and a maximum wall loading of 2.0 kips per linear foot were used as a basis for recommendations related to the construction of the residential buildings. C. These are estimated values since foundation plans were not available at the time of production of this report. If design loading is to exceed these assumed values, it will be necessary to reevaluate the given recommendations. D. All loading is assumed to be dead plus reasonable live load. PURPOSE AND SCOPE OF WORK The purpose of our services was to evaluate the site soil conditions, and to provide conclusions and recommendations relative to the site and the proposed development. The scope of work includes the following: A. A geologic reconnaissance of the site. B. Shallow subsurface exploration by drilling. C.' ''Laboratory testing of - selected soil samples obtained from the expl oratory bori ngs dri 11 ed f or thi s project. D. Review of selected technical literature pertaining to the site. E. Evaluation of field and laboratory data relatiye to soil conditions. F. Engineering analysis of the data obtained from the exploration and testing programs. G. A summary of our findings and recommendations in written report. November 2, 1989 -2- 07-1405-P 1 09-10-831 Contained In This Report Are: A. Discussions on regional and local geologic and soil conditions. B. Graphic and/or tabulated results of laboratory tests and field studies. C. Discussions and recommendations relative to allowable foundation bearing capacity, recommendations for foundation design, estimated total and differential settlements, lateral earth pressures, site grading criteria, geologic and seismic hazards. Not Contained In This Report_ A. This report does not address the potential presence of hazardous materials in any manner. SITE DESCRIPTION The site of the proposed project is located on the west end of Avenue 50, south and west of Lake Cahuilla in La Quinta, California. A. The site of the proposed development is currently vacant with scattered desert brush, short grass, weeds, cactus and debris. 0. The property has an overall slope to the east. C. The base of the Santa Rosa Mountains form the south and west edge of the site. D. The existing Riverside County aggregate pit occupies the eastern edge of the site. FIELD EXPLORATION Exploratory borings were drilled for observing the soil profile and obtaining samples for further analysis. November 2, 1989 -3- 67-1405-P 1 89-10-031 A. ' Ten (10) borings were drilled for soil profiling and sampling to a maximum depth of twentg--six (26) feet below the existing ground surface. The borings were drilled on May 5, 1989, using an eight (a) inch diameter hollow -stem auger powered by a GME 45--B drilling rig. Alternately, eight (8) inch diameter continuous flight augers were used. The approximate boring locations as indicated on the attached plan in Appendix A, were determined by pacing and sighting from existing streets and topographic features, The boring locations should be considered accurate only to the degree implied by the method used. 8. Samples were secured within the borings with a two and one-half (2.5) inch diameter ring sampler (ASTM D 3550, shoe. similar to ASTM D 1586). The samples were obtained by driving the sampler with a one hundred forty (140) pound hammer; dropping thirty (30)_ inches. The number of blows required to drive the sampler one foot was recorded. Recovered soil samples were sealed in containers and returned to the laboratory for further classification and testing. G. Bulk disturbed samples of the soils were obtained from cuttings developed during excavation of the test borings. The bulk samples were secured for classification purposes and represent a mixture of soils within the noted depths. D. The final logs represent our interpretation of the contents of the field logs, and the results of the laboratory observations and tests of the field samples. The final logs are included in the appendix A of this report. The stratification lines represent the approximate boundaries between soil types although the transitions may be gradual. LABORATORY TESTING After a visual and tactile classification in the field, samples were returned to the laboratory, classifications were checked, and a testing program was established. A. Samples were reviewed along with field logs to determine which would be further analyzed, Those chosen were considered as representative of soil which Would be exposed and/or used in grading and those deemed within building influence. November 2, 1989 -4- 87-1405-P 1 89-10-831 B. In -situ moisture content and unit dry weights for the core samples were developed in accordance with ASTM D 2937. C. The relative strength characteristics of the subsurface soils were determined from the results of direct shear tests. Specimens were placed in contact with water at least twenty-four (24) hours before testing, and were then sheared under normal loads ranging from 0.5 to 2.0 KSF. D. Classification tests consisted of: Expansion Index (11OC Standard No. 29-2), Maximum Densitg-Optimum Moisture (ASTM D 1557), and Hydrometer Analysis (California Test Method 203), E.... Refer to Appendix B for tabular and graphic representation of the test results. SOIL CONDITIONS As determined by the borings, site soils were found to consist primarily of fine to coarse sands with gravel. The boring logs in Appendix A contain a more detailed description of the soils encountered. A. The soils were found to be fairly firm with relatively high blowcounts and the majority of the in -place densities indicating relative compaction near or above ninety (90) percent of maximum density. B. The soils were found to be very dry throughout. C. Cobbles and boulders were encountered throughout the site D. Clay and silt contents of the soils exhibit low plasticity. Expansion tests indicate soils to be in the "very low" to "low" expansion category in accordance with Table 29-A in Appendix D of this report. Refer to section F of the structures section for specific explanations and requirements dealing with expansive soil. E. Refer to Appendix 8 for tabular and graphic representation of the test. GROUNDWATER Free groundwater was not encountered in any of the borings. The depth to groundwater in the area is generally in excess of one hundred (100) feet. Fluctuations in groundwater levels may occur due to variations in rainfall, temperature and other factors. November 2, 1989 -S- 87-1405-P 1 89-10-831 REGIONAL GEOLOGY The project site is located in the western Coachella Valley near the base of the Santa Rosa Mountains. The Coachella Valley is part of the tectonically active Salton Basin. The basin is a closed, internally draining trough that has been filled with a complex series of continental clastic materials during Pleistocene and Holocene time (Van de Camp, 1973). The San Andreas rift zone dominates the geology of the Coachella Valley. The Banning and Mission Creek faults, which are parts of the San Andreas system are responsible for earthquakes recently felt in the Coachella Valley. Other regional faults that have produced events felt in the Coachella Valley are the San Jacinto, Imperial and Elsinore faults -(see figures 1 & 2). Fused upon the historical and prehistoric record, the Coachella Valley segment of the San Andreas fault system is likely to generate a magnitude seven (7.0) or greater earthquake within the next fifty (50) years. The potential for a magnitude seven (7.0) earthquake within the next fifty (50) years is estimated by Seil-, (1985) as `High- (50%-90%). The San Jacinto fault is considered the most active fault in Southern California. It has produced four (4) magnitude six (6.0) earthquakes in the past eighty-eight years. Therefore, we have selected the San Andreas and San Jacinto faults as the design faults for this particular project. LOCAL GEOLOGY Site development is proposed in the alluvial fan area and in and around the foothill area of the property. Lithologic units observed on -site consist of Mesozoic Granitic rocks, in the hill areas and Quaternary Alluvium throughout the site. A. Descriptive Geolo On -site Lithologic units are described as folllows: I. Mesozoic Granitics - r Orange brown to gray brown, coarse grained, ranging in composition from granite to diorite. Some areas exhibit a gneissic texture that has been intruded by thin (3-6") non-mafic dikes. Outcrops are highly weathered, with the gneissic texture striking generally in a northerly direction and dip slightly (less than 15°) to the northwest. Me H + 1� &otlr 04 P'r.e •�l 1��Ict Z + � y b IsclubcI CN'_Q L •era�a f Cam, ypRLpCiC i. 9OkVybtId S Tait iBaser 1 rHOChoP S + 35' R 1 r VC FIN to ax0"L� _ ti loops:rr ^ SaHTA YryE ��as=4 q 6-bar Sonia aarowc Verr,ra `rB`411rL Trrnl -`�M IIarns 5tn 6«r,o.ar,o 4 _ LA3t. r + Pp+gry {r� + 5c+la Rasa �. Santa Crv7 Is. R„wi-ik q 'r-r� P0s*+ 0 Desert L wri E 5rtftp -a •� D =r • Cm�r.•+o `r O Borrega ri t21• Iz6• San F `� t C��'Ytap + gra++tep 33• �C sminlC a El Celli. �} San D:ego Yars►,z �sii1:4 / i no ' i U9• { Emeroes , + .Iff wif F Gf of G So too ISO i n epee C Ila, U71 116' n5• Base nap of southern California region with major faults * fault Map of Southern California Figure 1 BUENA ENGINEERS, INC. * From, Nz leman et al (19 7 3) 1927 (6) , 4B sAOP • �.�4vne Pine ° Tulare ' 1 + 1946 (6.9) '* ` +t , ,China Lakes Bakers 1952(7.7.6.4,6.1,6.11 °Sonia /.!aria 19161 �..��1•i p r►;7 an -'.-Sonty rGaro - 1941(6.0} 92S {63) `• 1971 {6.4} 1 ° /rlojare 1947(62; r�•• • °Barslaw\ Palmdale •�� �•' _ Son G'e�ordino oLos.4,^yere 1949{6.5} e �s{ 192 3 W/4) CC r� I918 (6.8) f c �� flndio 1933 (6.3) A O 100 kldes O 100 ?DO Kms. Earth Quakes of magnitude 5.9 and greater in the Southern California Region, 1912 — 1972 (including the North Palm Springs Earthquake). From Hileman et al (1973) ° �f 1968 (6.4) 90rr go 1942(6.5} San pieyR 1915 (6 I/4 , 6'/4 ..... 19 �•• Idericoli 1934 {T.11i i9f5 {7.11 l 1 1935(6.0)A ti 11 �' vv 194 0(6.0) 3 6.01 j• 196fi{6.3.'II C IS - .Frawley Seismic Epicenter Map of Southern California Figure 2 BUENA ENGINEERS, INC. DATE: 10-3 '� � FILE NO43"7-14p6PI November 2, 1989 -5- B7-1405-P 1 .69-10-831 1.2 2. Quarternsry A)luviurn -- n Orange brown to gray -brown, unconsolidated sand, silt and gravels deposited by fluvial process. These deposits are, generally, slightly consolidated to loose, slightly silty fine to coarse sand with gravel and cobbles to twenty-four (24) inches. Structural GeoJogy The subject property is located at the base 'of the Santa Rosa Mountains. This portion of the mountains is the result of granitic intrusions that have undergone subsequent periods of deformation and metamorphism. Deformation of the granitic rocks found on -site has imparted a gneissic texture observed in some local outcrops. As stated previously, the gneissic texture strikes generally in a northern direction and dips gently to the northwest. Jointing is randomly oriented, dipping near vertical. No active or potentially active faults are mapped in or around the site. The San Andreas Fault Zone is the closest active fault to the project and is located approximately nine and nine -tenths (9.9) of a mile to the northeast. Figure 3 shows the project site in relation to local geologic features. GEOLOGIC HAZARDS Primary Seismic Hazards: Primary seismic geologic hazards that may affect any property in the seismically active southern California region include ground rupture and strong ground motion. 1. Fault Rupture: a. The project site is not located in any Alquist-Priolo Special Study Zones. Nor are any active faults mapped through or adjacent to the project area. At the time of drilling, no surface expression of faulting was observed. Tz W F#1 -!k­ .p4e- z, Oat J7 EC -AI N L lk A UL 02 I v pk v 01 C 4r- of k C_ L Jq 40" ?Jre ;,on Y4 'A. '0-,f z t -zN 'k T - mi Z_. 72.4m)nz P&�r 'rT ik --p .r3 7 k Ct p7" rt Zo n ti A L 7 .4 Apr- Ll k.7, V; t -s r �W t—j if? or., 0,Af k so 4p ic qrL- v:j 7 4� Z 7' W- 1�if u. I V.-\. - I k ) tz k M A P 0 F P R 0 J E C I S I T E S \% R E L A 11014 TO L 0 C AL GEOLOGY S A N T A A 14 A M A P S H C E T North F I G U R E 3 L% Scale 1 :250 .000 es.." BUENA ENGINEERS, INC. 4r A .Z C,;L. Aid DATE; io 3' FILE NO-3-1 140�5_Pl November 2, 1989 -7- 87-1405-P 1 89-10-831 b. Some features that could be interpreted as faults were observed in the rock outcrops on --site. However, these fault features are associated with the metamorphic deformation of the granitic rocks during Mesozoic Times. In other words, the features are too old to be considered as active faults and, thus, do not pose a hazard to development. c. Fault rupture would most likely occur along previously established traces. However, fault rupture may occur at other locations not previously mapped. 2. Ground Shaking: a. Strong ground motion is the seismic hazard most likely to affect the site during the life of the intended structures. Using methods developed by Seed and 1 dri ss (1982), the following table was compiled for anticipated accelerations which may be experienced during an earthquake at the project site. TABLE 1 Maximum Design* Acceleration Fault hrthquake in Rock San Andreas 7.5 .43g San Jacinto 6.5 .23g Richter Magnitude Deep Cohesionless Soils Esti rnated Maximum Repeatable Approximate Acceleration Ground Distance to in Soil** Acceleratinrrs Project Site .34g .22g 9.9 mi .20g .13g 13.0 mi b. Groundshaking characteristics will vary from low frequency with high amplitudes -in the alluvial soils to high frequency la•,y amplitudes in the rock areas of the site. Duration of shaking could be from fifteen (15) to thirty-five (35) seconds. The site is mapped in Riverside County Ground Shaking Zone IIIA, and IIIB. Both Ground Shaking Zones are based on distance from caustive faults and soil types. November 2, 1989 A C. SecondarL� Seismic Hatiard : ME B7-1405-p1 89-10- 631 Secondary seismic geologic hazards that may affect the project site area include subsidence, liquefaction, seismicly-induced slope failure and ground lurching. a. Subsidence, whether seismically related or not, is considered a potential hazard in this area. Historic records report significant episodes of subsidence in the La Quinto area due to seismic forces and/or heavy rain fall and flooding. b. Liquefaction is the loss of soil strength as a result of an increase in pore water pressure due to cyclic seismic loading. Conditions for liquefaction include relatively high water table (within 40' of surface), low relative densities of the saturated soils and susceptibility of the soil to liquefy based on grain size. Our research indicates water is at depths greater than one hundred (100) feet below the surface. Also, the project is not located in the Riverside County Liquefaction Study Zone. c. Due to the competency of the bedrock materials, the potential for deep seated slope failure is considered low. However, localized failure may result in areas of unsupported foliations and joints exposed by grading. d. The rock slopes around the project are littered with loose cobbles and boulders imbedded in thin surfici8l soils. Development adjacent to the rock slopes could be impacted by downslope movement of said rocks. In addition, grading may disturb or expose more cobbles and boulders, thus, increasing the potential hazard of downslope rock movement. e. Ground lurching is generally associated with fault rupture. Because of the sites distance from any known "active" faults, the possibility of ground lurching affecting the site is considered low. Non -Seismic Hazards: Other geologic hazards that could affect the project site include landslides, flooding and erosion. a. No evidence of past landsiiding was observed at the site nor are any known landslides mapped in or around the project site. The subject property is composed of moderately to steeply sloping rock slopes that lead to coalescing alluvial fans. November 2, 1909 QE B7-1405-P 1 09-10-831 b. Flooding and erosion are always a consideration in arid regions. On -site, the erosion rate is affected by the active uplift of regional faults, relatively soft rock units, sparse vegetation and seasonal rains. C. The Coachella Vallley averages four (4) inches of rain per year_ When large amounts of rain occur suddenly, the surface alluvium becomes saturated and prevents further infiltration of the rains. The result is surface runoff and sheet flow drainage on slopes toward gullies and washes. In addition, desert pavement (a process where a crust is formed on the alluvial surface) adds to the "sealing" off of the alluvium surface, thus -increasing runoff. d. Generally, erosion in the desert can be reduced by minimizing soil disturbances and diverting seasonal runoff from areas of high potential erosion. On -site erosion may be reduced by diverting runoff from the hill area and the large drainages to the north of the project. CONCLUSIONS AND DISCUSSIONS Based on a review of a selected technical literature and site investigations, it is our opinion that the site is suitable for the intended development provided it is designed around the noted geologic hazards. The following is a summary of our conclusions and professional opinions based on the data obtained. Recompaction of soil will be required to limit settlement and improve bearing capacity. A. The primary geologic hazard relative to site development is severe ground shaking from earthquakes originating on nearby faults. The site is located in Southern California which is an active seismic area. In our opinion, a major seismic event originating on either the San Andreas or San Jacinto fault zone would be the most likely cause of significant earthquake actvity at the site within the estimated design life of the proposed development. B. Settlement due to seismic factors or flooding is a potential hazard in the La Quinta area. Qnlg areas of alluvial soils will be affected. C. Downslope movement of rock materials is a potential hazard to development adjacent to native rock slopes and in hill areas subject to grading. November 1, 1909 -to- 87-1405--P 1 89-10-631 U. Areas of alluvial soils may be susceptible to erosion. Preventative measures to minimize seasonal flooding and erosion should be incorporated into site grading. E. Fluvial erosion may affect the site during construction. F. Other hazards including liquefaction, landslides and tsunamis are considered negligible. G. The potential transition nature of many lots along the south and west portions of the site is a major consideration in site grading. Because differential settlement between fill material and -cut soils or bedrock is inevitable, all footings should be founded entirely on either fill soils, cut soils or bedrock. H. It is our opinion that the upper native soil will not provide uniform support for the proposed structure without the recommended sitework. To decrease the potential for consolidation and to provide a more uniform and firm bearing support for the proposed structures, we recommend constructing recompacted soil mats beneath all foundations and slabs -on -grade. It is recommended that any permanent structure constructed on the site be designed to at least minimum requirements for Seismic Zone 4 based on the latest edition of the Uniform Building Code. J. Adherence. to the following grading recommendations is necessary to mitigate potential settlement problems due to seismic forces, heavy rainfall, flooding and the weight of the intended structure. SITE DEVELOPMENT AND GRADING Prior to any construction operations, areas to be graded should be cleaned of vegetation and other deleterious materials. Appendix C, "Standard Grading Specifications" contains specific suggestions for removal and disposal of deleterious substances and, as such, forms a part of these Site Development and Grading Recommendations. November 2, 1939 A. Site Develooment - Crading 87-1405-P1 09-10-831 Site grading should be visually checked by Buena Engineers, Inc., or their representative prior to placement of fill. Local variations in soil conditions may warrant increasing the depth of recompaction and/or overexcavati on. Prior to site grading any existing structures, stumps, roots, foundations, pavements, leachfields, uncompacted fill, trash piles and any abandoned underground utilities should be removed from the proposed building and paving areas. The top surface should be stripped of all organic growth and along with other debris be removed from the site. 2. Depressions resulting from these removals should have debris and loose soil removed and be filled with suitable fill soils adequately compacted. No compacted fill should be placed unless the underlying soil has been observed by Buena Engineers, Inc. 3. In order to help minimize potential settlement problems associated with structures supported on a non -uniform thickness of compacted fill, Buena Engineers, Inc. should be consulted for site grading recommendations relative to backfilling large and/or deep depressions resulting from removal under item one above. in general, all proposed constrUCtion should be supported by a uniform thickness of compacted soil. 4. The grading of transition lot; should be e;raluated for individual lots. The amount and depth of cuts and fills will determine whether it is more economical to overexcavate the cut portion of the lot or extend footings through the fill. Regardless footings should bear entirely compacted fill soils, compacted cut soil or bedrock. 5. Testing showed soils are fairly firm but dry. Soils of this type can be susceptible to consolidation when water is added at the in: - situ conditions. Also, to control differential settlement and to produce a more uniform bearing condition, foundations should bear entirely on compacted soils or bedrock. Therefore, recompaction of the bearing soils is recomrnended. Compaction is to be verified by testi ng_ November 2, 1989 -12- 67-1405-P 1 89-10-031 8. Due to the granular nature of the site soils, it is expected that compaction may be obtained to a depth of three (3) to four (4) feet by heavily watering and compacting from the surface. 7. Building areas to receive more than one (1) foot of fill should be moistened to above optimum moisture to a depth of three (3) feet below original grade or the bottom of footings, whichever is greater. The exposed surface should be compacted so that at least ninety (90) percent of maximum density is obtained to a depth of two (2) feet below original grade or the bottom of footings, whichever is greater. Fill material should then be placed in eight (8) inch layers in a loose condition at or near optimum moisture and compacted to a minimum of ninety (90) percent of maximum densi ty. 8. Building areas to receive less than one (1) foot of fill and building areas that are in cut areas, should be moistened to at or above optimum moisture to a depth of three (3) feet below the bottom of the footings. The exposed surface should be compacted so that a minimum of ninety (90) percent of maximum density is obtained to a depth of two (2) feet below the bottom of the footings. The intent is to have at least two (2) feet of sail compacted to a minimum of ninety (90) percent of maximum density compose the building pad beneath the footings and to have an additional foot of moisture penetration. Compaction is to be confirmed by testing_ 9. These grading requirements apply to building areas and at least five (5) feet beyond building limits. 10. auxiliary structures including freestanding or retaining walls shall have the existing soils beneath the structure processed as per items seven (7), eight (8) and nine (9) above. The grading requirements apply to three (3) feet beyond the face of the walls. If plans for auxiliary structures and walls are provided for our review, these recommendations may be revised. November 2, 1969 -13- 07-1405-P 1 89--10-631 r± A 1 I. It is anticipated that during grading a loss of approximately one tenth (.1) of a foot due to stripping, and a shrinkage factor of approximately ten (10) to fifteen (15) percent for the upper three (3) feet of soil, may be used for quantity calculations. This is based on compactive effort needed to produce an average degree of compaction of approximately ninety-three (93) to ninety-four (94) percent and may vary depending on contractor methods. Subsidence is estimated between two -tenths (2) to three -tenths (3) of a foot. Site Development - Sloe Stobi l i t Cut slopes in the rock areas should be stable if constructed to a one and one-half to one 0 112:1), horizontal to vertical, maximum slope angle and cut less than twenty (20) feet in vertical height. However, to ease maintenance of the slopes, a more shallow dipping slope may be desirable. If a steeper or higher slope is needed, a geologic review of the specific location is necessary before construction. 2. Fill slopes should be stable if built to a two to one (2:1), horizontal to vertical, minimum slope angle and built no higher than twenty (20) feet. Fill slopes can either be overfilled and trimmed back or compacted mechanicaly from the surface. 3. Drainage across fill or cut slopes should be limited to prevent erosion. Rock cut slopes are susceptible to erosion because of their weathered condition. Drainage should be diverted from slopes to appropriate drainage collection devices that empty into the site storm drainage system. 4. Downslope movement of rocks on native slopes adjacent to development is a potential hazard. The hazard can be mitigated by removal of the rocks, deflection fences or brow ditches. Site Development - General The following general requirements listed in this section are super -ceded by the recommendations in the -Grading` section A above. November 2, 1989 -14- B7-1405-P 1 69-10-831 2. Previously removed soils, once cleaned of rocks larger than eight (6) inches in greatest dimension, and other deleterious material, may be placed in thin, layers and mechanically compacted back to f i ni sh grade. 3. Import soil used to raise site grades should be equal to or better than on -site soil in strength, expansion, and compressibility characteristics. Import soil may be prequalified by Buena Engineers, Inc. Comments on the characteristics of import will be given after the material is on the project, either in -place or in stockpiles of adequate quantity to complete the project. 4. Fill and backfill should be compacted to the minimum of ninety (90) percent of maximum dry density obtained bg the ASTN U 1557 test method. 5. Areas around the structures should be graded so that drainage is positive and away from the structures. Gutters and down spouts should be considered as a way to convey water out of the foundation area. dater should not be allowed to pond on or near pavement sections. 6. Added moisture within previously compacted fill could result in a number of reactions at the surface depending upon the amount of moisture increase, the in -place density of the soil, in -situ moisture content and soil type. Although the soil could in reality be expanding, collapsing, moving laterally due to the phenomenon "creep", the result is usually movement and will most likely manifest itself visually in structural slabs and street areas as cracks, (horizontal, lateral or vertical displacement). 7. The apparent cure to the problem is to not introduce excess moisture into fill material once in place. To help minimize increased moisture into the fill material, site drainage and landscape is critical. Site drainage should be in the form of roof gutter, concrete brow ditcher, ribbon gutters and gutters, storm drain and other drainage devices. Landscaping should be such that water is not alloyed to pond. Additionally, care should be taken so as not to over water landscaped areas. November 2, 1989 -18- 87--1408-P 1 09--10-831 A E 8. Failure to control increase in moisture content to compacted fill could result in settlement which could compound the problem bg rupturing water lines or other services and/or utilities, thus introducing additional moisture into the underlying soil. 9. The Recommended Grading Specifications included in Appendix C are general guidelines only and should not be included directly into project specifications without first incorporating the site specific recommendations contained in the Site Development - Grading section of this report. Chapter 70 of the Uniform Building Code contains specific considerations for grading and is considered a part of these General Guidelines. 10. It is recommended that Buena Engineers, Inc., be retained to provide soil engineering services during construction of the grading, excavation, and foundation phases of the work. This is to observe compliance with the design concepts, specifications or recommendations and to allow design changes in the event that subsurface conditions differ from those anticipated prior to start of construction. Excavations 1. All excavations should be made in accordance with applicable regulations. From our site exploration and knowledge of general area, we feel there is a potential for construction problems involving caving of relatively deep site excavations (i.e. utilities, etc.). Where such situations are encountered, lateral bracing or appropriate cut slopes should be provided. 2. No surcharge loads should be allowed within a horizontal distance measured from the top of the excavation slope, equal to the depth of the excavation. Traffic Areas The surface soil from the referenced project has been sampled in the location and tested for R--Value per California Test Method 301. The testing resulted in an R-Values of 71 and 72. The paving designs listed below are based on a design R-Value of 70. November 2, 1989 -16- 87-1405-13 1 69-10-031 Traffic Index = 6.0 use 4.0" of asphalt concrete on compacted subgrade or use 3.0" of asphalt concrete on 4.0" Class II Base Traffic Index = 6.5 use 4.0" of asphalt concrete on compacted subgrade or use 3,0" of asphalt concrete on 4.0" Class II Base Traffic Index = 7.0 use 4.0" of asphalt concrete on compacted subgrade or use 3.0" of asphalt concrete on 5.0" Class II Base Traffic Index = 7.5 use 4.5" of asphalt concrete on compacted subgrade or use 2.5" of asphalt concrete on 4.0" Class II Base or Traffic Index = 8.0 use 4.5" of asphalt concrete on 4.0" Class II Base or Traffic Index = 0.5 use 5.0" of asphalt concrete on 4.0" Class II Base or 2. These design sections are based on the paved areas being confined on two (2) sides. If the minimum requirements of the City of La Quinta exceed the design sections listed above, the City requirements may become the basis for design. 3. If paving directly on subgrade, subgrade should be compacted to ninety-five (95) percent of maximum density. When paving on Class II Base placed over subgrade, subgrade should also be compacted to ninety (90) percent and Class 11 Base to .ninety-five (95) percent of maximum density. During subgrade preparation, areas should be visually observed by a representative of Buena Engineers, Inc. in addition to the required compaction, the subgrade should be firm and unyielding when proof rooted with a fully loaded water truck. November 2, 1969 -17- 137-1405-P 1 89-10-831 F. Uti 1 ity Trenches Backfill of utilities within road right-of-way should be placed in strict conformance with the requirements of the governing agency (dater District, Road Department, etc.). 2. Utility trench backfill within private property should be placed in strict provisions of this report relating to minimum compaction standards. In general, service lines extending inside of property may be baekfilled with native soils compacted to a minimum of ninety (90) percent of maximum density. 3. Backfill operations should be observed and tested by Buena Engineers, Inc., to monitor compliance with these recommendations. STRUCTURES Based upon the results of this evaluation, it is our opinion that the structure foundation can be supported by compacted soils placed as recommended above. The recomendations that follow are based on "'Very low" expansion category soils. A. Foundations It is anticipated that foundations will be placed on firm compacted soils as recommended elsewhere in this report. The recommendations that follow are based on "very low" expansion category soils. 1. Table 29-A gives specific recommendations for width, depth and reinforcing. Other structural consideration may be more stringent and would govern in any case. A minimum footing depth of twelve (12) inches below lowest adjacent finish grade for one (1) story structures and eighteen (18) inches for two (2) story structures should be maintained. 2. Conventional Foundations: Estimated bearing values are given below for foundations on recompacted soils, assuming fill import (if required) to be equal to or better than site soils: a. Continuous foundations of one (1) foot wide and twelve (12) inches below grade: November 2, 1989 -18- 87-1405-P 1 89-10-631 i. 1000 psf for dead plus reasonable live loads. ii. 2400 psf for wind and seismic considerations. b., Isolated pad foundations 2' x 2' and bottomed twelve (12) inches below grade: i. 2000 psf for dead plus reasonable live loads. ii. 2650 psf for wind and seismic considerations. 3. Allowable increases of 200 psf per one (1) foot of additional footing width and 300 psf for each additional six (6) inches of footing depth may be used. The maximum allowable bearing will be 2500 pcf. 4. Although footing reinforcement may not be required per Table 29- A; one (1) number four (*4) rebar at top and bottom of footings should be considered in order to span surface imperfections. Other requirements that are more stringent due to structural loads will govern. 5. Soils beneath footings end slabs should be premoistened prior to placing concrete. 6. Lateral loads may be resisted by soil friction on floor slabs and foundations and by passive resistance of the soils acting on foundation stern walls. Lateral capacity is based partially on the assumption that any required backfill adjacent to foundations and grade beams is properly compacted. 7. Foundation excavations should be visually observed by the soil engineer during excavation and prior to placement of reinforcing steel or concrete. Local variations in conditions may warrant deepening of footings. S. Allowable bearing values are surcharge may be neglected) reasonable live loads. B. Slabs -on -Grade net (weight of footing and soil and are applicable for dead plus Concrete slabs -on -grade should be supported by compacted structural fill placed in accordance with applicable sections of this report. November 2, 1969 -19- 67-1405-P 1 89-10-831 C A 2. In areas of moisture sensitive floor coverings, an appropriate vapor barrier should be installed in order to minimize vapor transmission from the subgrade soil to the slab. The membrane should be covered with two (2) inches of sand to help protect it during construction. The sand should be lightly moistened just prior to placing the concrete. 3. Reinforcement of slab -on -grade is contingent upon the structural engineers recommendations and the expansion index of the supporting soil. Since the mixing of fill soil with native soil could change the expansion index, additional tests should be conducted during rough grading to determine the expansion index of the subgrade soil. Also, due to the high temperature differential endemic to desert areas, large- concrete- slabs on grade are susceptible to tension cracks. As a minimum, we recommend that all interior slabs -on -grade be reinforced with 6" x 6" / 010 x *10 welded wire fabric. Additional reinforcement due to the expansion index of the site soil should be provided as recommended in section F below. Additional reinforcement may also be required by the structural engineer. 4. It is recommended that the proposed perimeter slabs (sidewalks, patios, etc.) be designed relatively independent of foundation stems (free-floating) to help mitigate cracking due to foundation settlement and/or expansion. Settlement Considerations 1. Maximum estimated settlement, based on footings founded on firm soils as recommended, should be less than one (1) inch. Differential settlement between exterior and interior bearing members should be less than one --half (1/2) inch. 2. The majority of settlement should occur during construction. Frictional and Lateral Coefficients Resistance to lateral loading may be provided by friction acting 'on the base of foundations, a coefficient of friction of .50 may be used for dead load forces. 2. Passive resistance: acting on the sides of foundation sterns (300 pcf, equivalent fluid weight), may be included for resistance to 1 ateral 1 oad. November 2, 1989 -20- 07--1405-P 1 89-10-831 F G 3. A one-third (1/3) increase in the quoted passive value may be used for wind or seismic loads. 4. Passive resistance of soils against grade beams and the frictional resistance between the floor slabs and the supporting soils may be combined in determining the total lateral resistance, however the friction factor should be reduced to .33 of dead load forces. 5. For retaining walls backfilled with compacted native soil, it is recommended that an equivalent fluid pressure of thirty-five (35) pcf be used for well drained level backfill conditions. Expansion The design of foundations should be based on the weighted expansion index (UBC Standard No. 29-2) of the soil. As stated in the soil Properties section, the expansion index of the on -site soil is in the very low (0-20) classification. However, during site preparation, if the soil is throughly mixed and additional fill is added, the expansion index may change. Therefore, the expansion index should be evaluated after the site preparation has been completed, and the final foundation design adjusted accordingly. Additional Services This report is teased 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. i-laintaining Buena Engineers, Inc., as the soil engineering firm from beginning to end of the project will help assure continuity of services. These test would be additional services provided by our firm. The costs of these services are not included in our present fee arrangements. The recommended tests and observations include, but are not necessarily limited to the following: 1. Consultation during the final design stages of the project. 2. Review of the building plans to observe that recommendations of our report have been properly implemented into the design_ 3. Observation and testing during site preparation, grading and placement of engineered fill_ 4. Consultation as required during construction. November 2, 1909 -21- 87-1405-P 1 89-10-631 LIMITATIONS AND UNIFORMITY OF CONDITIONS The analysis and recommendations submitted in this report are based in part upon the data obtained from the ten (10) borings performed on the site. The nature and extent of variations between the borings may not become evident until construction_ If variations then appear evident, it will be necessary to reevaluate the recommendations of this report. Findings of this report are valid as of this date. However, changes in conditions of a property can occur with passage of time whether they be due to natural processes or works of man on this or adjacent properties. In addition, changes in applicable or appropriate 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 (t) year. In the event that any changes in the nature, design or location of the building are planned, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and conclusions of this report modified or verified in writing. This report is issued with the understanding that it is the responsibility of the owner, or of his representative, to insure that the information and recommendations contained herein are celled to the attention of the architect and engineers for the project and are incorporated into the plans and specifications for the project. It is also the owners responsibility, or his representative, to insure that the necessary steps are taken to see that the general contractor and all subcontractors carry out such recommendations in the field. It is further understood that the owner or his: representative is responsible for submittal of this report to the appropriate governing agencies_ Buena Engineers, Inc., has prepared this report for the exclusive use of the client and authorized agents. This report has been prepared in accordance with generally accepted soil and foundation engineering practices. No other warranties, either expressed or implied, are made as the professional advice provided under the terms of this agreement, and included in the report. November 2, 1989 -22- B7-1405-P 1 89-10-831 It is recommended that Buena Engineers, Inc., 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 Buena Engineers, Inc., is not accorded the privilege of making this recommended review, we can assume no responsibility for misinterpretation of our recommendations. END OF TEXT Appendices November 2, 1989 -23- 87-1405-P 1 89-10-831 REFERENCES 1. Envicom, Riverside County, 1976, Seismic Safety Element. 2. Greensfelder, Roger W., 1974, Maximum Credible Rock Accelerations from Earthquakes in California, CDMG Map Sheet 23. 3. Ploessel, N. R. and Slosson, J. E., "Repeatable High Ground Accelerations from Earthquakes", 1974 California Geology, Val. 27, No. 9, Pgs. 195- 199. 4. Seed,-H. B. and Idriss, 1. M., 1982, Ground Motions and Sail Liquefaction During Earthquakes. 5_ Seih, Kerry, 1985, "Earthquake Potentials Along The San Andreas Fault`, Minutes of The National Earthquake Prediction Evaluation Council, March 29-30, 1985, USGS Open File Report 85-507. APPENDIX A Site and Vicinity Map Lays of Borings to - SRASS Cd D d c r r. 1 1 ;� �1r yY ,• ,, eD I s To.v_ J► x D�s�2-T ' LAKE •9r�rvcc� .sue BUENA ENGINEERS, INC. DATE- //, Z -- gc? JOB NOR7-IYOS-195�, LOG OF BORING Job No. B7-1405-P1 for Report No. Desert Lake DATE May 5, 1989 BORING NO. 1 LOCATION Per Plan LOG OF BORING for Job No. B7-1405-P1 Report No. DATE May 5, 1989 Desert Lake BORING NO. 2 LOCATION Per Plan .. L a a� O o .a E cn a o 4-4L 3 O tr] DESCRIPTION �,w c L u Cl n- �, U o a :AS o. ~ 0 C O v U *" a. ro E aU 0,�3 U Q" REMARKS AND ANALYSIS 0 ►i +' i; 30 35 36 37 31 46 Al: Brown gravelly fine to coarse sand 115.1 101.4 108.9 107.8 118.8 1.6 1.5 2-0 2.1 2.1 SP 95 84 90 89 98 Large gravel 71- 9' 5 10 15 20 �5 Relatively undisturbed ring sample No recovery Total Depth = 26, No freewater No bedrock I LOG OF BORING for Job No. B7-1405-P1 Report No. DATE May 5, 1989 Desert Lake BORING NO. 3 LOCATION Per Plan .-. Q N Ca 0 o � V) �? o -� co DESCRIPTION .� -- C 4�. U a im Q N v. � cn C O w ro °• b v D 6j p: U CL REMARKS AND ANALYSIS' =� e: I, •.' 16 21 40 5011 Al: Brown gravelly fine to coarse sand SP Cobbles 5 10 15 No recovery Total Depth = 16' No freewater No bedrock LOG OF BORING for Job- No. 67-1405—P1 Report No. DATE May 5, 1989 Desert Lake BORING NO. 4 LOCATION Per Plan �. Zi a CJ o ;+ C7 4--I h 3 DESCRIPTION *' �� C L U L C 1 o �_ o di 12. c o _ G.1 .0 4� > a� _b E L GJ O 41 REMARKS AND ANALYSIS .t ; . is Al: Brown gravelly fine to coarse sand Sp Cobbles throughout 5 15 Cobble refusal @ 12.5' No freewater No bedrock LOG OF BORING for Job No. B7-1405--Pl Report No. DATE May 5, 1989 Desert Lake BORING NO. 5 LOCATION Per Plan s 0 0 E o N U o DESCRIPTION cti }' +� ,w .. _ a W� O v CL >, ! G C a_ 4J 4-1+' > m c ro E O REMARKS AND ANALYSIS 5 ' Al: Brown gravelly fine to coarse sand SP Cobbles Cobbles 10 Total Depth = 15' No freewater No bedrock DATE Kay 5, 1989 LOG OF BORING for Desert take BORING NO, b Job No. B7-1405—P1 Report No. LOCATION Per Plan c a, 0 o E 3 DESCRIPTION 4 � �, L 4 c o u*' > b L REMARKS AND ANALYSIS ., f :�: Al: Brown gravelly fine to coarse sand SP - Cobbles throughout 5'— 15' 5- 10 15 20 Total Depth = 20' No freewater No bedrock LOG OF BORING Job No. s7.-1405—P1 for Report No. Desert Lake DATE May 5, 1989 BORING NO. B LOCATION Per Plan LOG OF BORING Job No. 87-1405--P1 for Report No. Desert We DATE May 5, 1989 BORING NO, 7 LOCATION Per Plan LOG OF BORING Job ,No. B7-1405-P1 for Report No. Desert Lake DATE May 5, 1989 BORING NO. 9 LOCATION Per Plan ^ 0 -c ° `' ei ' cci REMARKS AND ANALYSIS C6 L 3 DESCRIPTION u Q v'i J u c �. Q o0 p C} .. ... V) 0 0 V L'' ( ) Cobbles ��• Al: Brown gravelly fine to SP Cobbles 5 ':: coarse sand 10 0'. Cobbles 15 Total Depth = 15' No freevater No bedrock LOG OF BORING Job No. B7-1405-PI for Report No. Desert Lake DATE MaY 5, 1989 BORING NO, 10 LOCATION Per Plan c 0 *� c -43 ? rj; REMARKS AND ANALYSIS E o DESCRIPTION �wri (n -, m cu oa .., �C] �C14 u0a �UCL —CL v0 0 Cobbles throughout 3'— 10' Al: Brown gravelly fine to gp coarse sand 10 t•, Total Depth = 15' No freevater No bedrock APPENDIX B Summary of Test Results Table 29-A November 2, 1989 6-1 B7-1405-P 1 89-10-031 TEST RESULTS BORING/DEPTH 1 @ 0-5' 5 @ 0--5' USCS SP SP SOIL DESIGNATION Al A 1 check pt. MAXIMUM DENSITY (pcf) 121.3 123.3 OPTIMUM MOISTURE W 12.3 10.9 ANGLE OF INT. FRIC. 41.60 43.20 COHESION (psf) 60 100 EXPANSION INDEX 0 0 GRAIN SIZE DISTRIBUTION M GRAVEL 39.0 43.6 SAND 54.1 49.7 SILT 1.7 2.1 CLAY 5.2 4.6 SOIL DESCRIPTIONS: Al: Brown gravelly fine to coarse sand (SP) November 2, 1989 8--2 87-1622-P 1 89-10-831 IN -PLACE DENSITIES RELATIVE BORING & DEPTH DRY DENSITY X MOISTURE COMPACTION i @ 4.0 113.9 0.8 94% 10.0 110.0 0.8 91 1 2 @ 2.0 115.1 1.6 95 % 5.0 101.4 1.5 84 % 15.0 108.9 2.0 90 % 20.0 107.8 2.1 89 % 25.0 118.6 2.1 98 % 87-1405-P1 MOISTURE CONTENT IN PERCENT OF DRY WEIGHT H O O LL V m U W a c� 0 z M O IL z } F z W O } cc 0 METHOD OF COMPACTION ASTM D-1557-78, METHOD A or C SOIL TYPE Al Boring 1 @ 0-5' 122 120 118 MAXIMUM DENSITY OPTIMUM MOISTURE 121.3 pef 12.3% MAXIMUM DENSITY — OPTIMUM MOISTURE CURVES B7--1405--P1 MOISTURE CONTENT IN PERCENT OF DRY WEIGHT H O O LL U [0 U M W a 0 Z O a z F— z W 0 cc 0 8 10 12 METHOD OF COMPACTION ASTM D-1557-78, METHOD A or C 124 122 120 SOIL TYPE MAXIMUM DENSITY OPTIMUM MOISTURE Al Check Baring 5 @ 0-51 123.3 pcf 10.9% MAXIMUM DENSITY - OPTIMUM MOISTURE CURVES B7-14D5-P1 4 .-. a 3.5 F- O O0 3.0 U) n, 2.5 Y W Cl) r r^2.0 vJ W F'^ /v! - 1.5 V Z 1.0 0E Q = 0.5 CD NORMAL LOAD (KIPS / FOOT 2 ) DIRECT SHEAR DATA Soil type: Al Boring and depth: 1 Angle of internal friction: Cohesion: 80 psf 41.60 N Samples remolded to 90% of maximum density 13 Samples relatively undisturbed e7-1405—P1 4. r N 3. I- O OLL 3 a 2• Y U) 2.1 w F-- 1 N 0 z 1A Q = 0.! u] .0 ds 5H 7.: iF- imr. i�- 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 NORMAL LOAD (KIPS / FOOT 2 ) DIRECT SHEAR DATA Soil type: Al Check Boring and depth: 5 0 0-51 Angle of internal. friction: 43•2° Cohesion: 100 Psf 0 Samples remolded to 90% of maximum density 13 Samples relatively undisturbed cN F Z u u o; s W Z O z 7) 0. Pip IM: N v W u m a o o a� o a•in a fo iv C: _ _, CO to wCO p � � b L.�. Lri w`oo� VL..o c vo vo a. a, .. o a. ° .:, o +' a H CQ IA N w a w N ►- 3 `C3 'j E j N Q7 ►+ C N r to O L U C 44 C" +- =1 0 .E r L .a ' �,°•o�a °A° u c °-c°�s 3 aa� O a.� C 3 ov n.u� �� h o .. C L n M a o O �« L a o * C1 a� ~ o .o L O O .-. W .,., O 5 O C t .� i-� .h p 0 rf` U •O • O lSS O c� -. o O fII +' O C .v `� a.uoa �""B_ -•EoN'00 a o E*2 o a'O a �E.rnoi- v1 h U •b _ C G (d N ~ ++.• u h v) E - �,, -- . Sx u^ w 3 c 3 c u o~' 3 p� 3 N oo p O (� C�E x d X 0 .a%.Da �o woo xp C � .... •C C v a E E E L O p N CAS a �'• 4O L'' O ''O C Q p" � L. 4O O O• a p r+ .� � a •C � Z: � u C Cd -a � O u.. C, a O— O u am „ a C �- + rJ C a u E O O L1v W H a •--. L 0 H� O O P fd L O NoOC NWti N CIO NW a •t. '•-s I- i O C O --+ --+ N -• -:• N " —, N C a1 H •g o C •J O C 0 u u .-. C[- N O p 4n >, w wr QJ v C C i u7 .to W IA pLC _ `° _ -4N —(14 N N N N (N N Z NwVQ� ❑� L>nla. O O E L. ri LL. pej u- 0. V) Ssau>pryl ur2oog .c r. 00 .0 00 w .a W 00 a y1prM$urlooj n'�oo N�D6 NNv1 NNh C� ssau 3r wa �{1 }S woaC) .a00� w 00 0 w - SaT30}5 10 'ON N (V n CD FOUTNOTFS TO TABLE 29---A 1_ Premoistening is required where specified in Table 29-A in order to achieve maximum and uniform expansion of sails prior to construction and thus li` hit structural distress caused by uneven expansion end shrinkage. Other systems which do not include premoistening may be approved by the Building Dfficial when such eltemstives are shown to provide equivalent safeguards against ad4erse effects of expensive sails. 2. Underfloor access crawl holes shell be provided with curbs extending not less than six (6) inches above adjacent grade to prevent surface water from entering the foundation area. 3. Reinforcement for continuous foundations shall be placed not less then three (3) inches above the bottom of the footings and not less then three (3) inches below the top of the stem. -t. Reinforcement shall be placed at mid -depth of slab. 5. After premoistening, the specified moisture content of soils shell be maintained until concrete is placed. Required rnoiture content shell be verified by an approved testing leboratarg not more than twenty-four (24) hours prior to placement of concrete. 6. Crawl space°: under raised floors need not be premoistened except under interior footings. Interior footings which are not enclosed by a continuous perimeter foundation system or equivalent concrete or masonry moisture barrier complying with UBC Section 2907 (b) shall be designed and constructed as specified for perimeter footings in Table 29-A. 7. A grede beern not less then twelve (12) inches bg twelve (12) inches in cross section, reinforced as specified for continuous foundations in Table 29-A shell be provided at garage door openings. B. Foundation stem wells which exceed a height of three (z) times the stem thickness above lowest adjacent grade shell he reinforced in eccordanee with Sections 2418 and 2614 in the UBC or as required by engineering design, whi chever i s more restrictive. 9. Sent reinforcing bars between exterior footing and slab shall be omitted when floor is designed as an independent, "floating' slab. 10. Fireplace footings shall be reinforced with a horizanal grid located three (3) inches above the bottom of the footing and consisting of not less then number four (*4) bars at twelve (12) inches on center each way. Vertical chimney reinforcing bars shell be hooked under the grid. APPENDIX C Standard Grading Specifications C_ I STANDARD GRADING SPECIFICATIONS PROJECT: DESERT LAKE CLIENT: STUART ENTERPRISES, LTD. 1. These Standard Grading Specifications -have been prepared for the exclusive use of our client for specific application to referenced project in accordance with generally accepted soil and foundation engineering practices. No other warranty, expressed or implied, is made. 2. These specifications shall be integrated with the Engineering Report of, which they are a part. Should conflicting statements be found between these standard specifications and the itemized recommendations contained in the mein body of the engineering report, the latter shall govern_ 3. Buena Engineers, Inc., referred to as the soil engineer, should be retained to provide continuous soil engineering services during construction of the grading, excavation and foundation phases of the work. This is to observe compliance with the design concepts, specifications or recommendations and to allow design changes in the event that subsurface conditions differ from that anticipated prior to start of construction. 4. The presence of our field representative will be for the purpose of providing observation and field testing. Our work does not include supervision or direction of the actual work of the contractor, his employees or agents. The contractor for this project should be so advised. The contractor should also be informed that neither the presence of our field representative nor the observation and testing by our firm shall excuse him in any way from defects discovered in his work. It is understood that our firm will not be responsible for job or site safety on this project. Job and site safety will be the sole responsibility of the contractor. C-2 5. if the contractor encounters subsurface conditions at the site that (a) .are materially different from those indicated in the contract plans or in specifications, or (b) could not have been reasonably anticipated as inherent in the work of the character provided in the contract, the contractor shall immediately notify the owner verbally and in* writing within 24 hours. This notification shall be a condition precedent before any negotiations for "changed or differing site conditions" can proceed. If the owner determines that conditions do materially so differ and cause an increase or decrease in the contractor's cost of, or the time required for, performance of any part of the work under this contract, then negotiations shall commence between owner and contractor to provide equitable adjustment to owner or contractor resulting therefrom. 6. Whenever the words "supervision", "inspection", or "control" appear they shall mean periodic observation of the work and the taking of soil tests as deemed necessary by the soil engineer for substantial compliance with plans, specifications and design concepts. 7. These specifications shall consist of clearing and grubbing, preparation of land to be filled, filling of the land, spreading, compaction and control of the fill, and subsidiary work necessary to complete the grading of the filled areas to conform with the lines, grades and slopes as shown on the accepted plans. u. The standard test used to define minimLlm densities of compaction work shall be the ASTM Test Procedure D 1557. Densities shall be expressed as a relative compaction in terms of the maximum density obtained in the laboratory by the foregoing standard procedure. S. Field density tests will be performed by the soil engineer during grading operations. At least one (1) test shall be made for each five hundred (500) cubic yards or fraction thereof placed with a minimum of two (2) tests per layer in isolated areas. Where sheepsfoot rollers are used, the soil may be disturbed to a depth of several inches. Density tests shall be taken in compacted material below the disturbed surface. When these tests indicate that the density of any lager of fill or portion thereof is below the required density, the particular layer or portion shall be reworked until the required density has been obtained. C-3 10. Earth -moving and working operations shall be controlled to prevent water from running into excavated areas. Excess water shall be promptly removed and the site kept dry. Fill material shall not be placed, spread or rolled during unfavorable weather conditions. When the work is interrupted by heavy rain, fill operations shall not be resumed until field tests by the soil engineer indicate that the moisture content and density of the fill are as previously specified. 1 1. Compaction shall be by sheepsfoot rollers, vibrating sheepsfoot rollers, multiple --wheel pneurnatic-tired rollers or other types of acceptable compacting rollers. Rollers shall be of such design that they will be able to compact the fill to the specified density. Rolling shall be accomplished while the fill material is within the specified moisture content range. Rolling of each layer shall be continuous over its entire area and the roller shall make sufficient trips to insure that the required density has been obtained. 12. Existing structures, foundations, trash, debris, loose fill, trees (not included in landscaping), roots, tree remains and other rubbish shall be removed, piled or burned or otherwise disposed of so as to leave the areas that have been disturbed with a neat and finished appearance free from debris. No burning shall be permitted in the area to be filled. 13. When fill material includes rock, large rocks will not be allowed to nest and voids must be carefully filled with small stones or earth and properly compacted. Rock larger than eight (0) inches in diameter gill not be permitted in the compacted fill without review as to location by the soil engineer. 14. Organic matter shall be removed from the surface upon which the fill, foundations or pavement sections are to be placed. The surface shall then be plowed or scarified to a depth of at least eight (5) inches and until the surface is free from ruts, hummocks or other uneven features which would tend to prevent uniform compaction by the equipment to be used. Specific recommendations pertaining to stripping and minimum depth of recompaction of native soils are presented in the main body of the soil report. 15. Native soil free from organic material and other deleterious material may be used as compacted fill; however, during grading operations the soil engineer will re-examine the native soils for organic content. C-4 16. Imported material should be tested and reviewed by Buena Engineers, inc., before being brought to the site. The materials used shall be free from organic matter and other deleterious material. 17. Where fills are made on hillsides or exposed slope areas, greater than ten (10) percent, horizontal benches shall be cut into firm undisturbed natural ground to provide a horizontal base so that each lager is placed and compacted on a horizontal plane. The initial bench at the toe of the fill shall be at least ten (10) feet in width on firm, undisturbed natural ground at the elevation of the toe stake placed at the natural angle of repose or design slope. The width and frequency of succeeding benches will vary with the soil conditions and the steepness of slope. 10. The selected fill material shall be placed in layers which,. when compacted, shall not exceed six (6) inches in thickness. Layers shall be spread evenly and shall be thoroughly blade -mixed during spreading. After each layer has been placed, mixed and spread evenly, it shall be thoroughly compacted to a relative compaction of not less than ninety (40) percent. The fill operation shall be continued in six (6) inch compacted layers, as specified above, until the fill has been brought to the finished slopes and graded as shoyin on the accepted plans. 19. When the moisture content of the fill material is not sufficient to achieve required compaction, water shall be added until the soils attain a moisture content so that thorough bonding is achieved during the compacting process. When the moisture content of the fill material is exce.sive, the fill material shall be aerated by blading or other satisfactory methods until the moisture content is reduced to an acceptable content to achieve proper compaction. 2)u. Existing septic tanks and other underground storage tanks must be removed from the site prior to commencement of building, grading or fill operations. Underground tanks, including connecting drain fields and other lines, must be totally removed and the resulting depressions properly reconstructed and filled. Depressions left from tree removal shall also be properly filled and compacted. C-5 21. The methods for removal of subsurface irrigation and utility lines will depend on the depth and location of the line. One of the following methods may be used: 1) Remove the pipe and compact the soil in the trench according to the applicable portions of these grading recommendations, 2) The pipe shall be crushed in the trench. The trench shall then be filled and compacted according to the applicable portions of these grading specifications, 3) Cap the ends of the line with concrete to mitigate entrance of water. The length of the cap shall not be less than five (5) feet. The concrete mix shall have a minimum shrinkage. 22. Abandoned water wells on the site shall be capped according to the requirements of the appropriate regulatory agency. The strength of the cap shall be at least equal to the adjacent soils. The final elevation of the top of the well casing must be a minimum of thirty-six (36) inches below adjacent grade prior to grading or fill operations. Structure foundations should not be placed over the capped well. Sladden Engineering 45090 Golf Center Parkway, Suite F, Indio, CA 92201 (760) 863-0713 Fax (760) 863-0847 6782 Stanton Avenue, Suite C, Buena Park, CA 90621 (714) 523-0952 Fax (714) 523-1369 450 Egan Avenue, Beaumont, CA 92223 (951) 845-7743 Fax (951) 845-8863 800 E. Florida Ayenue, Hemcl CA. 92543 (951) 7 6-8777 Fax (951) 766-8778 February 14, 2019 CITY 0 1­ L.A U U I I1 A Project No. 544-19048 BUILDING DIVISION 19-02-070 Modern Structures, LLC REVIEWED FOR 0FFie,, CODE: P.O. Box 1573 COMPLIANCE Rancho Mirage, California DATF Subject: Geotechnical 7F Ilt EIVED JUN 2 6 2019 Project: Proposed Custom Home CITY OF LA QUINTA 79540 Tom Fazio Lane North DESIGN AND DEVELOPMENT DEPARTMENT Tract 28189 - Lot 6 & Portion of Lot 5 The Quarry La Quinta, California Ref: Geotechnical Engineering Report prepared by Buena Engineers, Inc. dated November 2,1989; Project No. B7-1405-P2, Report No, 89-10-831 In accordance with your request, we have reviewed the above referenced Geotechnical Engineering Report as it relates to the design and construction of the proposed custom residence. The project site is located at 79540 Tom Fazio Lane North within the Quarry development in the City of La Quinta, California. It is our understanding that the proposed residential structure will be of relatively lightweight wood -frame construction and will be supported by conventional shallow spread footings and concrete slabs on grade. The referenced report includes recommendations pertaining to the construction of residential structure foundations. Based upon our review of the referenced report and our understanding of the proposed construction, it is our opinion that the structural values included in this report remain applicable for the design and construction of the proposed residential structure foundations. The lot was previously graded during the initial rough grading of the Quarry project site. The rough grading included recompaction of the native surface soil along with the placement of engineered fill material to construct the building pads. Because the lot has been previously rough graded, the remedial grading required at this time should be minimal except where the grades need to be adjusted for the lot expansion. The building areas should be cleared of surface vegetation, scarified and moisture conditioned prior to precise grading. The exposed surface should be compacted to a minimum of 90 percent relative compaction prior to fill placement. Any fill material required to attain the design grades should be placed in thin lifts at near optimum moisture content and compacted to at least 90 percent relative compaction. February 14, 2019 -2- Project No. 544-19048 19-02-070 In our opinion the allowable bearing pressures recommended in the referenced Geotechnical Engineering Report remain applicable. Conventional shallow spread footings should be bottomed into properly compacted fill material a minimum of 12 inches below lowest adjacent grade. Continuous footings should be at least 12 inches wide and isolated pad footings should be at least 2 feet wide. Continuous footings and isolated pad footings should be designed utilizing allowable bearing pressures of 1500 psf and 2000 psf, respectively. Allowable increases of 300 psf for each additional 1 foot of width and 300 psf for each additional 6 inches of depth may be utilized, if desired. The maximum allowable bearing pressure should be 3000 psf. The recommended allowable bearing pressures may be increased by one-third for wind and seismic loading. Lateral forces may be resisted by friction along the base of the foundations and passive resistance along the sides of the footings. A friction coefficient of 0.48 times the normal dead load forces is recommended for use in design. Passive resistance may be estimated using an equivalent fluid weight of 300 pcf. If used in combination with the passive resistance, the frictional resistance should be reduced by one third to 0.33 times the normal dead load forces. Retaining walls may be necessary to accomplish the proposed construction. Lateral pressures for use in retaining wall design can be estimated using an equivalent fluid weight of 35 pcf for level free -draining native backfill conditions. For walls that are to be restrained at the top, the equivalent fluid weight should be increased to 55 pcf for level free -draining native backfill conditions. Back drains should be provided for the full height of the walls. Seismic pressures should be incorporated into any retaining walls greater than 6 feet in height. Seismic deign pressures may be provided once specific wall heights and locations are known design pressures can be provided. The bearing soil is non -expansive and falls within the "very low" expansion category in accordance with 2016 California Building Code (CBC) classification criteria. SIab thickness and reinforcement should be determined by the structural engineer, we recommend a minimum floor slab thickness of 4.0 inches and minimal reinforcement of #3 base at 24 inches on center in each direction. All slab reinforcement should be supported on concrete chairs to ensure that reinforcement is placed at slab mid -height. Sladden has reviewed the 2016 California Building Code (CBC) and summarized the current seismic design parameters for the proposed residential structure. The seismic design category for a structure may be determined in accordance with Section 1613 of the 2016 CBC or ASCE7. According to the 2016 CBC, Site Class D may be used to estimate design seismic loading for the proposed structure. The 2016 CBC Seismic Design Parameters are summarized on the following page. Sladden Engineering February 14, 2019 -3- Project No. 544-19048 19-02-070 Risk Category (Table 1.5-1): II Site Class (Table 1613.3.2): D Ss (Figure 1613.3.1):1.500g S1 (Figure 1613.3.1): 0.600g Fa (Table 1613.3.3(1)):1.0 Fv (Table 1613.5.3(2)):1.5 Sms (Equation 16-37 (Fa X Ss)):1.500g Sm1 (Equation 16-38 (Fv X Sij): 0.900g SDS (Equation 16-39 (2/3 X Sms]):1.000g SDI (Equation 16-40 (2/3 X Sm1)): 0.600g Seismic Design Category: D We appreciate the opportunity to provide service to you on this project. if you have any questions regarding this letter or the referenced report, please contact the undersigned. Respectfully submitted, SLADDEN ENGINEERING Brett L. Anderson - Principal Engineer SER/ra Copies: 4/Addressee BRETT L ANDERSON -A10. C45389 CIVIL ENGINEERING SXadden Engineering 31-(,( - [ OGW Please verify that soils reports contain all of the above information. In addition, to assure continuity between th© Investigation/reporting stage and the execution stage, please use the following checklist to verify that the concluslons and recommendations in the report cover all the required elements. Only then can we be assured that the construction documents address all of the site soli conditions. La Quints Geotechnical Report Checklist Does the "Conclusions and Recommendations"section of the report address each of the following criteria? "Address" means; ; (a) the criterion Is considered significant and mitigation measure(s) noted, or; (b) the criterion is considered inslghiftcant and explicitly so stated. Y No 11 Criterion ❑ Foundation criteria based upon bearing capacity of natural or compacted soil. © Foundation criteria to mitigate the effects of expansive soils. ❑ Foundation criteria based upon bearing capacity. of natural or compacted soil. ❑ Foundation criteria to mittgate.the effects of liquefaction. ❑ Foundation criteria to mitigate the effects of seismically. Induced differential settlement. ❑ Foundation criteria to mitigate the effects of long -tern differential settlemenL INC ❑ Foundation criteria to mitigate the effects of varying soil strength. 'C ❑ Foundation criteria to mitigate e*ected total and differential settlement, Any "No" answers to the above checklist should be noted as specific required Cbt'i'�CfIOnS. - -