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Home My WebLink AboutCT 81-19; Mar y Montanas Lots 18,21,30,34; Soils Report; 1986-04-22- - - - - - - - GRADING AND CDNPACTION CONTROL (INTERIM REPORT) TRACT 81-19, LOTS 18, 21, 30 AND 34 CITY OF CARLSBAD. CALIFORNIA Project No. 12S4W33-01 April 22, 1986 Prepared for: L.C.J. Development 1667 Mission Road, Suite C Fallbrook, California 92028 Attn: Mr. Carl Lynton Prepared by: CALIFORNIA 6EO TEK, INCORPORATED 42030 Avenida Alvarado, Suite A Ranch0 California, California 92390 (714) 676-2782 - CALlFORNIAGEOTEK,INC. 42030 Avenida Alvarado, Suite A l Rancho California, CA 92390 l (714) 676-2782 April 22, 1987 Project No. 12S4W33-01 INTRODUCTION .- - 'We are providing you with an interim report for the work performed on the model home lots, as requested by Mr. Carl Lynton. The compacted fill on the subject lots has been tested for compliance with applicable City specifications. The work included: (1) inspecting the clearing and stripping, (2) inspecting and testing the overexcavation and backfill, (3) inspecting and testing the 'compacted fill, and (4) preparing this interim report presenting the findings, conclusions and recommendations. Plate 1 - Test Location Plan (30-scale) Appendix A - Maximum Density Curve Appendix R - Reference - - - - - 12S4W33-01 Page 2 FINDINGS Proposed Development We understand four model homes are proposed for construction on lots 18, 21, 30 and 34 of Tract 81-19. Site Conditions The site is located on the west s,ide of El Camino Real, north of Chestnut Avenue. The pads have been constructed on a westerly descending slope. The lots below the graded pads slope to the west at an approximate gradient of 10 percent. The slopes were covered with annual grasses. Grading The reference for grading was a grading plan prepared by Rick Engineering Company (San Marcos). The earthwork was performed by Frank Wright and Sons (Carlsbad) beginning in late 1986. Work on the subject lots was tested from April 10 through 14, 1987. The equipment used was a Caterpillar D8K dozer and a 3000 gallon water truck. The native grasses were removed to the lower portions of the lots and were not used in the fill materials. The fill materials were obtained from the cut areas of the pads. The soils are silty sand (terrace deposits) and were placed in lifts of 6 to 8 inches in uncompacted thickness, and compacted. The maximum fill depth is approximately 3 feet. Overexcavation was required for the transition pads (Lots 30 and 34). The limits of overexcavation are 3 feet below finish grade and extending 5 feet beyond the building perimeters, in plan view (Plate 1). Lots 18 and 21 are all cut pads excavated to the bedrock with the top 12 inches of earth materials ripped and recompacted. There are eucalyptus trees on Lots 30 and 34.~ The trees are located on the east side of Lot 34 in the fill slope, on the north side of Lot 30 in natural ground, the east side of Lot 30 in the cut slope, and on the south side of Lot 30 in natural ground. It is our understanding that there will be either retaining walls or manually compacted fill around the trees. This will be done before the final mass grading report is submitted. An Expansion Index was performed by San Diego Soils (Appendix B) on the topsoils (SC) and terrace deposits (SM) on October 24, 1986. The resulting expansion potentials were 0.6 or VERY LOW for the terrace deposits and 21.5 or LOW for the topsoil material (Appendix B). We feel the expansion potential of 0.6 for the terrace deposits is represented on the subject lots 18, 21, 30, and 34. -- - - - - - - - .- - -- - - -. - .- - 12S4W33-01 Page 3 Comoaction Testinq The tests were performed in accordance with ASTM D1556-82 and ASTM D2937-83 with the maximum densities determined in accordance with ASTM 01557-78. The test locations are shown on Plate 1 and the results are summarized below: Test Lot No. No. 5321 30 5431 30 55 30 5k2/ 34 5731 34 583/ 34 5941 21 603/ 34 613/ 34 624/ 18 De&II/ 3.0 BFG 2.5 BFG 0.5 BFG 3.0 BFG 2.0 BFG 0.5 BFG 0.5 BFG 2.0 BFG 0.5 BFG 0.5 BFG Drv Densitv. ocf Moisture, % Field Max m tm 116.5 123.0 115.0 123.0 110.6 123.0 121.0 123.0 115.7 123.0 116.8 123.0 119.5 123.0 118.8 123.0 119.8 123.0 116.1 123.0 10.0 11.0 8.8 11.0 12.5 11.0 12.0 11.0 9.9 11.0 10.9 11.0 11.3 11.0 12.2 11.0 10.2 11.0 10.3 11.0 l/ BFG - Below finish grade to cent'er of test, feet 2/ Bottom of Overexcavation 3/ Overexcavation backfill 4/ Recompacted surface of cut pad Relative Comoaction, % 95 93 90 98 94 95 97 97 97 94 - - - - .~ .- - - - - - - - -. - 12S4W33-01 Page 4 CONCLUSIONS AND RECOMMENDATIONS Conclusions 1. 2. 3. 4. 5. 6. 7. 8. 9. The site was properly stripped prior to the precompaction and fill placement. The vegetation was removed from the fill area and was not used in the fill. The overexcavated backfill has been compacted to a minimum relative compaction of 90 percent based on ASTM D1557-78 (unweighted average = 95.3 percent). The bottom of overexcavation has been compacted to a minimum relative compaction of 90 percent based on ASTM D1557-78 (unweighted .average = 96.5 percent). The recompacted surface of the cut pads has been compacted to a minimum relative compaction of 90 percent based on ASTM D1557-78 (unweighted average = 95.8 percent). The maximum fill thickness is approximately 3 feet in vertical dimension. Lots 30 and 34 are transition pads and were overexcavated to a depth of 3 feet below finish grade and extended 5 feet outside the building areas in plan view. Lots 18 and 21 are all cut pads and were ripped to a depth of 12 inches to bedrock and recompacted. The expansion potential for the silty sand terrace deposits on the subject lots 18, 21, 30 and 34, is (VERY LOW). The earth materials consist of silty sand terrace deposits representing the VERY LOW expansion potential. 10. There are trees located on Lots 30 and 34. The fill around the trees on the east side of Lot 34 will have to be manually compacted or a retaining wall will have to be constructed around the trees. - - - - - - - - 12S4W33-01 Page 5 Recommendations 1. 2. 3. 4. All footings for single story construction shall be a minimum of 12 inches x 12 inches, with the depth measured below the lowest adjacent firm grade. Footings for two story construction shall be a minimum of 15 inches x 18 inches, with the depth measured below the lowest adjacent firm grade. All footings shall incorporate one No. 4 bar running continuously through the footings. The bar shall be lapped a minimum of 20 bar diameters and shall be placed approximately 3 inches from the bottom. Slab-on-grade concrete construction should be 4 inches nominal thickness and should incorporate 6 x 6 No. lo/No. 10 WWF or No. 3 rebar placed 30 inches on center. All steel shall be properly tied and placed-on 1 l/2 inch blocks. "Pulling" of the mesh during placement of the concrete shall not be permitted. Where moisture sensitive floor coverings are proposed, a moisture barrier, such as 6 mil Visqueen should be used. This .membrane should be protected with a minimum of one inch of sand placed above and below. BRL/tb Distribution: Addressee (4) Respectfully submitted, Bruce R."Lee RCE 23396 - APPENDIX A I35 .- -. 130 .- 12X.0 PCC & 11.0% MOISTWE - IZf _- 15C - ; ; II5 F z J 3 z IlC -5 ,~ ICS - ZERO AIR VOIPS CUR\‘ES - 10: - -. 95 90 P.M. 1’2S4 w 33 -01 12S4W33-01 APPENDIX B - References San Diego Soils Engineering, Incorporated, Preliminary Geotechnical Investigation, Mar y Montanas, Carlsbad Tract 81-19, November 1982 _- -~ - - - - Bi