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Home My WebLink About30578 (Lot 36)TRIAD FOUNDATION ENGINEERING INC Foundation Engineering - Engineering Geology Material Testing i. Construction Inspection 17231 EAST RAILROAD STREET, CITY OF INDUSTRY, CA 91748 TELEPHONE (816) 9642313 PRELIMINARY SOILS AND GEOLOGIC INVESTIGATION PROPOSED SINGLE FAMILY DEVELOPMENT LOT— TRACT 30578 RIM FIRE LANE DIAMOND BAR, CALIFORNIA JOB NUMBER 88-495 SEPTEMBER 7, 1988 0: f hen w 14h h0 cross 0045 V REQUESTED BY: Sun—Ray 23441 Sand Ridge Diamond Bar, CA 91765 elV i falMr a!!i:i, !1 il• i(.__._.... i TRIAD FOUNDATION ENGINEERING INC Foundation Hngineering E g hiatcrial Testing Construction Inspcction 17231 EAST RAILROAD STREET, CITY OF INDUSTRY, CA 81748TELEpliONE (818) 984.2313 19 8 8September8, Job #88-494 I,.. information was obtained from the Final Subsurface and geologic iates dated Geolo is Report by Robert Stone and AssocAs -Graded g t'.r ;n I Sun—Ray 23441 Sand Ridge91765 r. Diamond Bar, ationinvestigation Soils and Geologic Subject: Preliminary le Family Development Proposed Sing Lot -36; Tract 30578 i Rim Fire LaneCalifornia Diamond Bar, r. Gentlemen: conclusions of a soils and This report p resents the findings -and The performed at the subject site. geologic investigation information on rr, this invest g ation was to obtainpurposeof formations for evaluation on which surface soils and geologicsub property. Our development of the to base recommendations for the inuseinthisreportareintendedforurecommendationsgiven the foundationarationofconstructionplansfor grading and prep of the proposed project. I,.. information was obtained from the Final Subsurface and geologic iates dated Geolo is Report by Robert Stone and AssocAs -Graded g t'.r ;n I fl i T1,1lovember 5, 1970 combined with information from the excavation of One test pit at the approximate location presented in the Appendix of this report. iTRODUCTTON grposed Development: It is understood that the site will be developed for a 2 -story single family residence with wood frame and stucco type construction. The proposed structure is expected to be constructed on shallow foundations and to have light loads. T;"The Grading Plan enclosed indicates moderate grading to form a r. • l _uAl pad area and cri.,ewar Cuts are proposed to be retained with walls and fill slopes will be constructed at 2:1 (horizontal to vertical) gradients. Site Description: The property investigated is located on the west end of Rim Fire Lane in "The Country" of Diamond Bar, ki California (Thomas Guide p.97, E-5). It is roughly triangular iin shape with depths of 403.5 and 408 feet on the south and east property lines, respectively. 1'•I X1-1. , ' Geographically, the site is situated along the crest and north 9 '`racing: flank of a, small ridge along the east side of Brea canyon I 1 I h 2 in the Eastern Puente Hills area. Locally, the lot descends from the street to the canyon bottom below with gradients of 29 to 35 degrees. Drainage appears to be good with sheet flow over the ground surface to the natural drainage course near the north property line, At the time of our investigation the site was vacant and its past; 1' use is unknown. vegetation consisted of many large clumps of Black Walnut trees and a sparse to thick ground cover of wild grasses and weeds. Recent disking on the upper portion of the has destroyed most of the previously existing ground cover. Subsurface Conditions: No man-made fills are known to exist on i'I '•the site. i1'.,,,.,Natural soils are clayey silt topsoils underlain by a siltstone edrock. The topsoils have a depth of approximately ?+!!'s•r p pproximatel 2 feet and X ,,are in a slightly moist and porous condition. Topsoils are expansive and not reliable for structural support without i! ;'xecompaction. edrock underlying the site is in a hard condition and will provide good foundation support. Soils on the site are moderately expansive with changes in sl 1,.' ' moisture content. 3 GEOLOGY The bedrock underlying the site has been previously mapped as 1, interbedded sandstones and siltstones of the Puente Formation. Locally, the rock was well exposed in the test pit excavated on, the site and consisted of a shaly siltstone with a few interbeds of sandstone. The rock is generally in a dense, well bedded condition; however,, the top 12 to 18 inches is moderately disturbed from creep movement. The thickness of creep disturbed material is expected to vary depending on the variety of the underlying bedrock material. 11 Y:Bedding planes mapped on the site indicate a general northward li"'dip on the upper portion of the existing slope with dips of 6 to13 i, i,{.. i;°,r20 degrees. This condition has created an area of advanced creep I f1'4ond shallow slumping in the northeast portion of the property and 11 i""has been incorporated into a Restricted -Use -Area as designated in the Final As -Graded Geologic Report by Robert Stone & Associates dated November 5, 1970. The remainder of the property where the roposed development is to be located is not significantly i`,i'.,Affected by creep or shallow slumping and is in a grossly stable pondition. ZI CONCTAISTONS AND RECOMMRNDATTONS The information obtained during our investigation i. I•, I,'1lt. i;i,Udicates pqi. general: that the subject site is suited for the proposed i l,I r- rp ti s.contained in thisli;'dev6lopj4ent, provided the recommendation project report are incorporated into the design considerations, ans, and job specifications. The building site is safe against T azard from landslide, settlement, or slippage and the proposed tihave no effect on the geologic stability Ofti;: Will property outside the building site. M Bedding planes are daylighted on the natural slope as I shown on 1p,,O,4'fthe Section A -A'; however, the angle of dip is very low and slope tability analysis using low assumed shear strengths indicates a safety the analysis in excess of 1.5. one foot column was used in lysis with the highest depth and all other portions will have a higher safety factor. All grading should conform to the requirements of the 0!" County of Los Angeles and the standard grading specifications d in this report. p r e s e n t e to grading, all structures, vegetation, and debris should be removed from the site. Uncertified fills and loose soils Pbould be excavated to firm bedrock where structural fill is required. 5 s i and benched into bedrock inCompactedfillsshouldbekeyed accordance with the enclosed Figure 1. TYPICAL FILL OVER NATURAL SLOPE 1 P / ' TOE SHOWN ON i GYM OY 1 j ''' i.•`.•":'. r G l2AD I IIG P IJ i i . / 4 Typical 1 pi• i F ^ TUB' / 10, Typicaf' BEDROCK OR FIRM q t ii,l •.— -- FORMATION MATERIAL i',j' 2 154 Minimum t' Minimum i NOTEc WERE NATURAL SLOPE GRADIENT IS 511 OR LESS, BENCHING IS NOT idECESSRRy UNLESS STRIPPING DID NOT REMOVE ALL CODiPRESSIBLE MATERIAL- j FIGURE I 14 Areas to receive fills should be scarified 6 to 8, inches o is adjust the moisture content to near optimum conditions and t en compacted to minimum requirements. Fills should be placed in 6 o S inch loose lifts at near optimum moisture conditions and r compaGted to not less than 90 percent of the maximum dry densityt densities for the typical soils should be established in r4.., . 0,.:accordance with the standard ASTM D1557-78 method of test. I 6 On-site soils may be used for compacted fills, provided they are free from organic and deleterious material. If imported soils iare required, they should be approved by the Soils Engineer prior to acceptance at the site, to insure a similar quality to that, required by design. jjGrading operations should be conducted under the observation of the Soils Engineer to provide assurance of compliance with job j'`specificati' p ponsandaCertificationofCompactedFillupon completion of grading. h..:Foundation Design: Continuous or spread footings having a a++'ipinimum embedment of 18 inches into bedrock may be designed for C'.4n allowable bearing pressure of 2000 pounds per square foot. All footings should have a minimum width of 12 inches. Footings a? ^f fir, • : I I ,,pear descending slopes must have a minimum 5 -foot horizontal 1 distance from the side of the footing to the face of the bedrock t 101 1i*,s'lope. Total settlements with the assumed loads should not 1';l Ieneed 3/4 inch and differential settlements under similar loads r. should not exceed 1/4 inch. A 1/3 increase in -bearing pressure may be used in design whenx; torconsidering wind or seismic loads of short duration. 7 Y7 ' Y r,:'. € -e. ;i+i '•!(" {c Aye a .:,'+i'$^fete }:I''.j.ti, t.4,%1 W` _lr;',';iYY. - `•:{%, :jr `: fir., i 1 {' continuous footings should have minimum reinforcement of one ljjWumber 4 bar placed near the top of the footing and one Number 4 b4.'near the bottom. jeiteral Resi.sta cer Resistance -to horizontal forces on foundations may be provided by the combined effect of passive 4pressures in bedrock and frictional resistance between concrete Fond firm soils, Lateral bedrock pressures of 300 pounds per j6quare foot per foot of depth may be used u to 2000I? p y p pounds per square foot. A coefficient of friction of 0.35 is recommended for the on-site soils. Moor Slabs: Concrete floor slabs may be supported by the statural or compacted fill soils. To provide uniform support, the fop 8 inches of soilshould be scarified and compacted at near optimum moisture conditions. Due to the moderate expansive j!patential of the on-site soils, it is recommended that the top 18 4nches have a moisture content of 120 percent of optimum stablished 24 hours prior to pouring the concrete. Slabs should i have a mininmum thickness of 4 inches and reinforcement of 6x6 - a W2.9 x W 2.9 (6x6 - 6/6) welded wire mesh, or equivalent, placed a a 1 at the center of the slab. moisture sensitive floors, a vapor barrier membrane covered with a minimum 2 inches of clean sand should be placed below the I slab, t ilk J 1' a 12 inches b 12 inches should be provided across thegradebeaminy arage entrances. The base of the grade beam should be at the same elevation as the adjoining footings. A similar transition gection (thickened slab) may be substituted as recommended by the Structural Engineer. sir ' Ret lls; Small unrestrained retaining walls with a level and 2:1 backfill should be designed to resist active soil pressures equivalent to a fluid pressure of 45 and 55 pounds per cubic foot, respectively, plus any additional surcharge expected f -from the surface. Weep holes consisting of open joints in block walls or 1 -inch diameter holes at 2 foot intervals should be placed at the base of the wall 6 to 12 inches above finished grade, or an adequate drainage system at the base of the wall should be provided to i prevent hydrostatic pressures. 1 walls should have a granular backfill compacted as fill soil. Jetting should not be permitted. I` SUMMARY 11his report was prepared to aid the project designers, reviewing li agencies, grading contractors, owners, and other concerned parties in completing their responsibilities for the successful completion of this project. The findings and recommendations nal rally accepted profess accordance with gene aced in accowereprep other warranty, es- We make no principles and practii'engineering t ''i, or implied. ressed n either exp on results of thearebased f indings and recommendations rii. he ':! X: investigation, combined with interpolation f Jeld and laboratory locati.on. it from the test Pit conditions i! of soil and geologic graor construction that ding are encountered during conditions this office should be 3appear to reported, different than those tbe notif Jed ed and approved by the should be inspect All footing excavations S lacing forms or t Geologist prior to p Soils Engineer Or commended minimum depths into the re to insure reinforcement, reinforc I" supporting material. n this project* work with You 0 p, 41 aciate the opportunity to stions We appr ence if you have any que contact us at your convenience i!'Plea5e regarding this report, submitted, Respectfully TRI. ENGINEERING, INC. AD FOUNDATION G. Uhl C.E.G.C. Stillman 502 Frank V. i:; G. E. 805 tio. 502 C E RT IF JF E 14 C, IE Addressee (4) ( 10 tea.. t.. t' PPTTTT"" {^^{// yjAe(4 LP M tains a description of methods andThefollowingAppendixcon r;,, aboratory test results which were used in the engineer ng NaValuations and recommendations contained in the report. Included are the following Maps and Plates, Geologic Map ates Plate A----- Geologic Cross Section Plate B ----- Test Pit Log Plate C ----- Direct Shear Summary Site Exo orati on On August 24, 1988, field explorations were made by excavating thegone;gone test pit at the approximate location"indicated on Ir"enclosed Geologic,Map. A backhoe equipped -with a 24 -inch bucket Was used to advance the test pit to a depth of 6 feet below the existing grade, r, Relatively undisturbed samples of soils were obtained in the f'Jfield using a barrel drive sampler with a tapered cutting shoe. 1 -inchiThesoilsampleswereretainedin2.5 -inch diameter by rings within the sampler and secured in moisture resistant bags 1 os soon as taken to minimize the loss of field moisture while being transferred to our laboratory for testing. 3r yicontinuous observations of the materials encountered in the test p t were recorded'in the field. The soils were classified in the r field by visual and textural examination, and these classifications were supplemented by obtaining bulk soil samples for future examination or testing in the laboratory to assure d classifications in accordance with the Unified Soil 3' classification System. Descriptions of the visual observations of color and soil i condition, depth of undisturbed cores or bag samples, field density, and field moisture content are presented on the Test Pit Log, Plate B. ti.l. JI Laboratory Tests and Resultlus Direct Shear Tests; Direct shear tests were conducted on undisturbed samples of the investigated soils to determine the angle•of internal friction and cohesion. Samples were inundated for a minimum of 24,hours under normal load before, testing and PPshearloadswereapplied quickly in accordance with the standard.'; i., procedure for consolidated undrained shear tests. Horizontal forces were applied to pass the peak shear and determine the residual shear strength of the soil specimen. The results and c: residual shear strengths under increased moisture conditions are shown on Plate C K, Expansion: Expansion tests were performed on typical soils to determine their expansion potential. The tests were made in accordance'With the UBC Standard 429-2. The following table presents the expansion index data; Soil Type;* SILTSTONE Location; Test Pit #1 E 3.01 Initial Moisture Content: 21.2 Final Moisture Content-. 41.6 Initial Dry Density: 79.1 pcf Expansion Index 59 Expansion Classification Medium III d Foundation Engineering JOB k: 88-494 DATE: 9-1-88 DIII.ECT SHEAR SUMMARY 2.51' RING 420 400 380 360 3-10 320 300 280 20-0 240 220 200 ISO 160 140 120 100 80 60 10 20 0 0 -12 A6 18 0 STRAIN - INCHES 1000 2000 3000 -1000 NORML STRESS - P.S.F. SAMPLE LOCATION: Test Pit #1 @ 2.0' SOIL CLASSIFICATION: BEDROCK — SILTSTONE SAMPLE TYPE Undisturbed 0: 29° C: 300 p s . f PLATE 0 LOG Location see ge-01 )SJS,_M&1 88-4.94 Drill Date 8-24-88 man— actRim Fire Lane -Diamond Bar Test Pit NO-- Logged By JLK Driving Weight 14011 No.> 1 BEDBOCY-8 etc.); 0 4j Q) I UNIT (FILL, NATURAL, L/I 0 cu 4J CLAY, etc-) C r4 0 k to r. AND, SILT, C; Ln 44 44 W 4JMATERIAL (S tc.) Z U V, density, e 0moisture, DescriptiOn (cOlO-vj mo Ln P _4 CL 0) C14 0 . 9 Q) 24) ATTITUDE ME ASUREMOIITS; U M F - Faillt 0 B- bedding 4 W IQ joint C - contact U A4 ith Sand - dark -browns ILL0TOPSOIL: Clayey SILT w to very porous slightly moist, firm, moderately COLLUVIUM: Clayey SILT with rock fragments Slightly Moist, very firm C 68.9 18.57 BEDROCK: Shaly SILTSTONE - light brown, dense, 30 top 12-18" well bedded with distinct surfaces, 3 B N68E 714W (m -P)' of rock is moderately disturber_ B TOPSOIL: from creep - rock below is hart irregular ) surface & unaffected 4- B, NOW IONE-m some fine grained Sandstone beds White t diatomaceous Shale B N78E 91N - M-9 7 8 10 11 12 13 15 PLATE BLAInc.RIAD FOUNDATION ENGINEERING, In V I fr1^ - 1 U D i— 1 . t r r rl , , I ;, > I •I II Ir I 11.} i I r tI : I i,tl;' ' ,1. t'+4 v tial , . ' ,Z •;tr {f, • I`t ;p;F ' I l:l I y ''{' li I ; ; It I i rl TX* ut': 34 En ; k tiba m tx — — Co t q I r tr t o Q lam` t LU w tx — — Co t q I r