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Home My WebLink AboutPR 2.7.4; ELLERY RESERVOIR PROPERTY; ADDITIONAL SOIL STUDIES; 1970-11-05FIR a.71 LA WOOD WARD - CLYDE & ASSOCIATES . . . ..•. CONSULTING SOIL AND FOUNDATION ENGINES AND GEOLOGISTS 3467 Kurtz Street November 5, 1970 San Diego ' Project No. 69-263' California 92110 , (714) 224-2911 . . Engineering. Science, Inc. . . ... . . 3260-1/2 Rosecrans Avenue . . .. .. San Diego, California 92110 . . . . Attention:. Mr. Richard R. Duesen ADDITIONAL SOIL STUDIES ELLERY.RESERVOIR SITE CITY OF CARLSBAD WATER SYSTEM IMPROVEMENTS . . . S .. CARLSBAD, CALIFORNIA •. . . . .. . . In accordance with your request and the recommendations in our soil investigation report dated November 12, 1969,.we ha.ve investigated the ' subsurface soil. condttions at the subject tank s.ite. . The 'purpose -of our investigation is to determine the general 'subsurface soil conditions with particular regard to 'whether variations' exist from those indicated ' .in our previous report. This site'was not drilled during our original soil ''investigation. . 0 ' " .Three-test borings were made at the tank. site at the' approximate loca- ' tionsshown'on the Site,Plan, Figure' 1. ' Drilling was done on Augu't 31 , 1970, with a 6-.inch diameter truck-mounted power auger under the - supervision of an engineering geologist from our firm.' F.ield.boring logs, were prepared' by the geologist on the' basis. of an examination of the -samples secured and the excavated material. The Logs of Test: Borings presented on Figures 2 through 4 are based on an inspection of the samples', laboratory test results and on the field boring logs.. The vertical pos-ition of'each sample.is shown on 'the Logs of Test Borings., The test boring's were located: in' the 'field with the aid' of' ã plan entitled, Water System Improvements, City of Carlsbad, Cal-if orni a, Ellery Reservoir, 5 mg-Site Plan" prepared by Engineering Science, Inc The soils encountered were visually classified in' the laborato'ry'and ' evaluated with respect to swelling'characteristics, dry density and ' moisture content. .The classification of,a representati-ve sample of a. clayey soil was substantiated'by grain'si'ze analyses and the'determination , ' of plasticity characteristics. Swelling characteristics of this same I ' soil were determined by a loaded swell test on an undisturbed sample The results of tests on undisturbed 'samples, except for the loaded', swell tests, are shown with the penetration resistance of the sampler at the .corresponding samplle locations on the Logs.of Test Borings.. ' The grain size distribution 'curves are shown and the plasticity. characteristi.cs . ' are indicated on Figure 5. and the results. of the loaded swell test are reported on Figure 6 Engineering Science, Inc. Project No. 69-263 , November 5, 1970 . . Page As indicated in our preliminary report,the tank will be located on the top of a north-south oriented beach ridge remnant between the approxi- mate elevations of 315 to 340 feet, plan datum. The surface of the site slbpes away gently on both sides. and is covered with dried grasses. :A grove of eucalyptus trees surrounds the site which is currently occupied by a 70-feet diameter water tank. It was anticipated thro.ugh. a visual inspection of the site that subsurface soil conditions would be similar to other tanks studied for our preliminary report. The subsurface soils as revealed, by the test borings in general, consist of 1/2 to 1-1/2 feet Of loose to medium dense porous silty sand and topsoil underlai.n by a clayey-sand material which grades downward at depths of 3-1/2 to 5-1/2, feet into very dense silty sandstone of'Pleis- tocene age. The latter material' extends. to.the depths explored, a maximum of approximately 28 feet. The results of laboratory tests indicate that the' clayey sand material is low in -potential expansiveness; however, at other tank sites it was revealed that this clayey sand grades laterally into potentially expansive sandy clay 1enss and pockets. The sandstone, at depth, is particularly competent and will withstand relatively high structural 'loads. An examination of the available plan indicates that the tank on the' northeast side will be located relatively close to the cut/fill line. Although none was indicated by'ou'r 'test borings, potentially expansive sandy ,clay may occur' in pockts along this daylight. line. It will he necessary to undercut these' pockets' and replace with properly, compacted sandstone or lean concrete mix The following conclusions and recommendations are essentially those, presented in our preliminary report and are reiterated here for your information. ('1) It is recommended that the footings for the tank' be founded entirely in natural sandstone Footings founded a minimum, depth of 12 'inches below rough grade in dense sandstone materials may' be des'igned. for' an allowable, soil' bearing pressure of 6000 pounds per square 'foot (total load)... 'Porous topsoils. and/or potentiailyexpansivé' soils may, be 'encountered near the daylight boundary during the grading. These soils should be removed to 'a depth of 2 feet below-rough grade and replaced with.a'lean.concr'ete mix.' As an alternate.-to placing concrete in the.undercut areas, compacted nonexpansive soil may replace the unsuitable soils. If this procedure is sel.ected,'it is further, recommended that the entire interior area be scarified .to a minimum depth of 12 inches and recompacted in. place. WOOD WARD CLYDE & ASSOCIATES ' Consulting Soil and Foundation Engineers and Geologists Engineering Science, Inc. S . Project No. 69-263 . . November 5, 1970. Page S (4) It is recommended that the upper 2 feet of all fill be composed of properly compacted nonexpansive soil. The clay soils may be spread in the deeper.parts of the 'fill. * (5) Proposed cut and fill slopes having maximum heights in the order of 25 and 20 feet, respectively, and maximum' slope inclinations' of 1-1/2 to 1 will, in our opinion, have adequate. factors of safety against deep-seated failure if constructed in accordance with plans and specifications. . (6) Concrete slabs-on-grade should be underlain by a , . . minimum 4 inches of clean wetted sand. . . . . (7) It is recommended that all .eart.hworking' be performed in accordance with the Specifications" for Contr011ed Fill attached to our preliminary report. The 'grading should be under th,e super-. vision of a'qualified soil -engineer. All compacted fill should be tested.. by a soil engineer.. It is further recommended that all footing excavations be inspected by'Woodward-Cl'yde &. Associates prior to placement'of steel and concrete. . . The conclusions and recommendations made in this report are based 'on the assumpti.on that the soil conditions do not deviate appreciably from those disclosed by .the test borings or those anticipated by the' previous. ' experience in the area of-the subject project. Variations may be'encountered and should be. anticipated. We 'should be notified. if variations do' occur,.. so we may make supplemental recommendations if this should be required Louis K79 RPW/LJL/jsk : : ' , . ' , ' : •' ' S , , , S Attachment 4 cc k . ' •.. ' S WOODWARD CLYDE & ASSOCIATES :. Consulting Soil and Foundation Engineers and Geologists ' 326-. 31,5 320 315 I . Proposed \ 2 . i - I -Tank \ hO 839 II . I •d . 77 . 3. -- — — .'-Property . i Line. 340 Existing-Tank to be di.smantled I 325 I . 330 . Approximately ) . / 35 - 900- feet to 30 Chestnut Avenue.. Indicates approximate location of test boring. . Indicates approximate existing ground surface. contour. Boringl .. I Medium-dense, damp, brown silty BC -.63* - 63 sand (SM) (Porous) • : 2 • Very dense, damp, red-brown clayey - BC = 67 ]- sand (SC) Cn - grades to very dense, damp, reddish- • BC = 90/6nJ _ brown silty sand (SM) 10 - (Poorly, indurated sandstone) CL - BC = I5/6 " 14 LEGEND WC = Water Content in percent of dry weight DD = Dry Density in pcf. BC = Number of blows by I '1.0 pound hammer fail ing 30 -inches to drive sampler 12 inches. . Sampler Data ID = 2 0", OD = 2 5" (SM) = Group classification symbol in accordance with the Unified Soil Classification System Sample Number LOG OF TEST BORING I • • '.. •; . CITY OF CARLSBAD WATER SYSTEM IN PROVEMENTS ELLERY SITE i.4JODWARD.CLYDE & ASSOCIATES . • • . . • • • CONSULTING SOIL ENGINEERS AND GEOLOGISTS SAN DIEGO. CALIFORNIA . LL-15 Boring3 0- BC = 22 }L .Ivdiumdense, damp, brown silty (SM) Very dense, damp, red-brown clayey BC = 34/6" II]2 sand (Sc) 5 -. .. 3 .1.1 4-I t becomes less clayey a) 0 Cu . 10 Cn CD 15. BC = 67 ]- ..' Very dense, damp, brown silty sand .. 20 - (SM) 25 - .. . .. .28— For Legend, see Figure 2 LOG OF TEST BORING 3 • . CITY OF CARLSBAD WATER SYSTEM IMPROVEMENTS: ELLERY SITE flOYJARD.CLYDE & ASSOCIATES CONSuLTINGSOIL ENGINEERS AND GEOLOGISTS • • • • • SAN DIE, CALIFORNIA • • • • DR. BY: ALS SCALE: I" = 5' • JPROJ. NO: 69-263 ICKID • BY: DATE: 10-1-70 ]FIGURE NO: • I RESULTS OF LOADED SWELL TESTS • &-i Ninter Initial • Final pressure Expansion Dry Density ter Content • Saturation Dry Dry Density ter Content • Saturation pcf % pcf • %• • psf • %of Initial Hight 2-2 112.6 9.7 55 I II 2 16.2 88 160 1.2