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Home My WebLink About; La Costa Canada Lots 1-14; Soils Report Final; 1972-03-24BENTON ENGINEERING. INC. APPLILD SOIL YEC”*N1CS -- FO”NDAIIQNS “I., LL CAION mO”LCY*~O **II DlrsO. cILIcoT1III* 02115 ,H,LlP HEtarING BENTO” C”z*,Ol*l. ClYlL IUGIMLI” March 24, 1972 - La Costa Land Company Costa Del Mar Road Ran&o La Costa, California 92088 I Subiect: Proiect No. 72-2-16D ,)\I4 D1100. ,(13-5634 LA ML,*: 469.585. . Grdding Permit No. L-6098 Final P&art on Compacted Filled Ground Lots 1 to 14, inclusive Q!dJa= La Costa Canada S&r Diego County, California Gentlemen: This is to report the results of tests and observations made in order to inspect the compaction of filled ground placed on certain areas of Lob 1 to 14, inclusive, and Lot 22 of La Costa Canada in San Dlego County, California. Compacted filled ground hadpreviously been placed on Lots 1 to 8, inclusive, and on a portion of Lot 22 during the gmding of Lo Costa South Unit No. 4 in January, 1970. The recently placed compacted fill soils were placed during the period between February 16, and February 25, 1972. The approximate areas and depths of filled ground placed under our inspection in accordance with the approved specifications are shown on the attached Drawing No. 1, entitled “Location of Compacted Filled Ground.” The grading plan used for the placement of filled ground was prepared by Rick Engineering Company and dated November 1, 1971. ,- The approximate locations at which the tesk were taken and the final test resulk are presented on pages T-l to T-4, inclusive, under the “Table of Test Results.” The laboratory determina- tions of the maximum dry densities and optimum moisture contents of the moior fill moteriols are presented on poge L-l, under the “Laboratory Test Results.” Some of the maximum dry densities shown in the “Table of Test Resufk” were combinations of these. The tests were taken during the weekly periods indicated below: Test Number Week Ending 1- i. Period Between January 13 and January 23, 1970 1 to 41, inclusive January 17, 1970 i”! 42 to 52, inclusive January 24, 1970 SlOlO - .21.22 c. 1 : -~ ‘0 I i- ..- -, I * :.4 .~ i- 1 /~- ,,- .& ; I I Project No. 72-2-16D La Costa Land Company w- 2 March 24, 1972 Test Number Week Ending Period Between February 16 and February 24, 1972 1 ta 12, inclusive February 19, 1972 13 ta 55, inclusive February 26, 1972 The final results of tesk and observations indicate that the compacted filled ground hos been placed at 90 percent of the maximum dty density or greater. It has been determined that the fill materials, compqcte~ to 90 percent of the moxlmum dry density, hove a safe bearing value of 2000 pounds per square foot for one foot wide continuous footings founded at a minimum depth and placed five feet or more inside the top of compacted filled ground slopes. If footings are placed closer to the expased slopes than 5 feet inside the top of compacted filled ground slopes, these should be deepened one foot below a 1 l/2 horizontal to 1 vertical line projected outward and downward from a point 5 feet horizontally inside the top of compacted filled ground slopes. Task indicate .that the compacted filled ground is adequate to satisfactorily support the propacad one or ~VJ story wood frome dwellings without detrimental settlemenk. Expansive soils were placed in the upper three feet of certain compacted fill areas ond also exist in the upper three feet below finished grade in certain cut areas. The final classification of the soil conditions existing on each lot together with recommendations for the special design of foot- ings and slabs placed OK expensive soils are presented as follows: TypeA - Critically Expansive Soils - Lot No. 22 1. 2. 3. 4. 5. Avoid the use of isolated interior piers. Use continuous interconnected reinforced footings throughout, and place these at a minimum depth of two feet below the lowest adjacent exterior final ground surface. Reinforce and interconnect continuously with steel bars all interior and exterior footings with one #5 bar at 3 inches above the bottom of the footings and one 85 bar placed 1 l/2 inches below the top of the stems of the footings. Exercise every effort to assure that the soil under the foundations and slabs has uniform moisture content, 1 percent to 3 percent greater than optimum through- out the top 3 feet beloti finished grade at tha time of placing foundations and slabs, Preferably use raised wooden floors that span between continuous footings, or if concrete slabs are used, then these should be reinforced with a minimum of 6 x.6 - lo/10 welded wire fabric and underlain by a minimum of 6 inches of crushed rode beneath all concrete slabs in order to minimize the effect of potential expansion. d moisture barrier should be provided over the crushed rock and then covered by 2 inches of sand immediately below the slobs under the living areas. Sepamte garage slabs from perimeter footings by a l/2 inch thickness of con- struction felt or equivalent, to allow independent movement of garage slabs relative to perimeter footlngs. &sure complete sepamtIon by extendlng the hit over the hrll depth of the front thickened edge of the gamge slab. Also, cut off the garage door stops at least l/2 inch above the slab. mN,ON LNOINILRINO. INC. 1 I i $3 j .~ ! t I~.- I I-~ I- 1 ‘- ! -, \ .i d .- ‘i i- I i f - I 1~ I .- ,~ !& I ’ I I Project No. 72-2-160 La Costa Land Company -3- Mclrch 24, 1972 6. Provide positive dminage away from all perimeter footings to a horizontal distance of at least 6 feet oukide the house walls. TypeB - Marginally Expansive - Lot Nos. 9 to 12, inclusive, and 14 ta 21, inclusive Recommendations for these lak are the same as those listed for the Type A lot with the two following exceptions: 1. The continuous footings may be placed at a minimum depth of 18 inches below the lowest adiocent exterior final ground surface rather thon the two feet recommended for the Type A lot. 2. Sfngle 84 bars placed as described above, in Item 2, of the previous section near tops and bottoms of all interior and exterior footings moy be substituted for the #5 bor recommended for the Type A lot. Recommendations 3 to 6, inclusive, as listed for the Type A lot, are also applicable to the Type Blots. Type C - Nonexpansive Soils - Lot Nos. 1 to 8, inclusive footings and slabs will not Le required on these lob. large undeveloped area within the boundary of this subdivision and therefore inspection soil conditions was not made on this lot. Respectfully submitted, BENTON ENGINEERING, INC. B~d?d%&va- R. C. Remer Reviewed by Distr: (1) (2) Addressee La Costa Land Company Attention: Mr. 8urtm L. Kmmer Rick Engineering Company, Carl&ad San Diego County Building Inspection, Vista Office lllNTON ENOINLERING. INC.