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HomeMy WebLinkAboutPE 2.87.41; POINSETTIA VILLAGE; UPDATE GEOTECHNICAL INVESTIGATION; 1986-06-233467 Kurtz Street San Diego, California 92110 (619) 224-2911 0 CT si -Ob lb Woodward-Clyde Consultants June 23, 1986 Project No. 541681-PROl Poinsettia Associates 839 West Harbor Drive, Suite 1 San Diego, California 92101 Attention: Mr. Fred Delaney UPDATE GEOTECHNICAL INVESTIGATION FOR THE PROPOSED POINSETTIA VILLAGE CARLSBAD, CALIFORNIA Gentlemen: This report presents the results of our update soil investigation at the subject site. The site (also designated Carlsbad Tract 81-6(B)) is located south of Poinsettia Lane between Avenida Encinas and Interstate 5 in Carlsbad, California. To assist us In our study, we have discussed the project with you and with Coombs-Mesquita Architects and have been provided a copy of a preliminary plan dated December 23, 1985, prepared by Brian Smith Engi- neers., Inc. In addition, we have reviewed our records of work done previously on*the site. Our previous reports are entitled "Final Report of Engineering Observation of Grading and Testing of Compacted Fill, Lots 1 through 12, Carlsbad Tract 81-6, Carlsbad, California," dated February 7, 1985, and "Recommended Pavement Sections, Avenida Encinas and Loganberry Avenue, Carlsbad Tract No. 81-6, Carlsbad, California," dated January 23, 1985. We have also reviewed "Preliminary Soils and Geologic Investigation, Proposed 22.89 Acre Site for Industrial Commercial Develop- ment, Carlsbad, California," prepared by Medall, Aragon, Worswick & Associates,* Inc., dated August 31, 1981. We understand that the project will include minor regrading of the site (1-2 foot cuts and fills with a 4 foot cut in the area at the northwest corner of the site) and construction of a one- and two-story shopping center complex. We further understand that eight building sites will be rough graded only for future sale or development by others, and are not a part of this investigation. Figure 1, the Site Plan, shows the building sites planned for development by Poinsettia Associates, and the building sites planned for development by others. Consulting Engineers. Geologists and Environmental Scientists JffA_ Offices in Other Principal Cit!eS qV Poinsettia Associate Project No. 541681-th June 23, 1986 Page 2 0 Woodward-Clyde Consultants PURPOSE OF INVESTIGATION The purpose of our investigation will be to provide information to assist you and your consultants In evaluating the property and for project de- sign. In particular, our investigation is designed to address: General surface and subsurface soil conditions; Presence and effect of expansive soils; Grading and earthwork;' Types and depths of foundations and allowable soil bearing pressure; and Pavement design. Field and Laboratory Investigation Our field investigation included making a visual geologic reconnaissance of the existing surface conditions, making 4 test pits on May 29, 1986 and obtaining representative soil samples. The pits were advanced to a depth of approximately 6 feet, at the approximate locations shown on Figure 1. A Key to Logs is presented in Appendix A as Figure A-1. Final logs of the test pits are presented in Appendix A as Figures A-2 and A-3. The description of the logs are based on field logs, sample inspection, and laboratory tests. The results of laboratory tests are shown in Appendix B. The field investigation and laboratory testing programs are discussed in Appendices A and B. Review of Existing Final Report The February 7, 1985 WCC report indicates that the site is a cut-fill site. The cut area, toward the southeast along the freeway has been cut to a maximum of approximately 15 feet. The north and westerly part of the site has been filled to a maximum of approximately 5 feet. Loose natural surface soils in the central part of the site, were removed prior to placement of fill. Non-expansive granular fill was placed within 3 feet of rough grade in the fill portions of the site. Soils exposed in the cut areas are also non-expansive. General Surface and Subsurface Soil Conditions The site is essentially constructed in 1984, consisting of 12 level lot pads and a central paved access road. A subdrain system has been installed with lateral pipes aligned under the lot boundaries and a central collector line under the access road, which drains to the south into the existing storm drain under Avenida Encinas. Poinsettia Associate# Project No. 541681-PROl June 23, 1986 WbodWard-CWe Consukants Page 3 The cut slope along the southeast site boundary (approximately 15 feet high and 2:1 slope inclination) and the fill slopes along the west site boundary (approximately 5 feet high and 2:1 slope inclination) both appear to be only very slightly eroded, and there were no piles of dumped trash or fill on the site at the time of our investigation. - Our test excavations indicate that both the compacted fill soils and the natural formational soils are non-expansive granular silty and clayey sands. CONCLUSIONS AND RECOMMENDATIONS The conclusions and recommendations presented below are based on the results of our field investigation, review of our files and available plans, laboratory tests results, engineering analysis, and professional judgement. Grading We recommend that the proposed grading be performed in accordance with the attached Guide Specifications for Site Grading. We recommend that backfill placed in utility trenches located within 5 feet of a building and deeper than 12 inches, or backfill placed in any trench located 5 feet or more from a building and deeper than 5 feet, be placed in accordance with the above specifications. We also recommend that all grading be performed under the observation and testing services of our firm. Drainage We recommend that positive measures be taken to properly finish grade building pads after structures and other improvements are completed so that all drainage waters from the building pad and adjacent properties are directed off the site and away from foundations and floor slabs. Even when these measures have been taken, experience has shown that a shallow ground water or surface water condition can and may develop in areas where no such water condition existed prior to site development; this is particularly true where a substantial increase water infiltration results from landscaping irrigation. To further reduce the possibility of moisture related problems, we recom- mend that all landscaping and irrigation be kept as far away from the building perimeter as possible. Irrigation water, especially close to the building, should be kept to the minimum required level. We recommend that the ground surface in all areas be graded to slope away from the building foundations and floor slabs and that all runoff water be directed to proper drainage areas and not be allowed to pond., Foundations We recommend that conventional spread or continuous footings be designed for an allowable soil bearing pressure of 3,000 psf (total dead plus live Poinsettia Associate* Project No. 541681-PROl June 23, 1986 WoodMmrd-Clyde Consuftarft Page 4 load) at a depth below lowest adjacent rough grade of 18 inches. This is assuming that foundations are placed in properly compacted low expansion fill or undisturbed native soil. All footings should have a minimum width of 12 inches. The bearing pressure may be Increased by one third for loads that include wind or seismic forces. We recommend that all continu- ous footings be reinforced top and bottom with at least one No. 4 rebar. Pavement Design An R value test was performed on a sample of the probable pavement subgrade soils. Results of this test are presented in Appendix B. Based on the results of this test it is our opinion that the existing fill soils and formational soils are suitable for use as pavement subgrade soils. Where pavements are placed on fill, soils, we recommend that the top 12 inches of subgrade be scarified and compacted to at least 95 percent of the maximum dry density. Where pavements are placed on undisturbed formational soils, we recommend that the top 6 inches of subgrade be scarifled and compacted to 95 percent relative compaction. For design purposes we have used an R value of 50 for probable subgrade soils, which, in our opinion, is representative of the average subgrade conditions on the site. If import soils are used for subgrade under paved areas, an R test value should be performed on a sample and new pavement section used if necessary. Based on the above assumption we recommend the following pavement sections. Area Light vehicle parking Access Roads A.C. over Crushed Aggregate Base Full Depth A. C. P.C.C.* 311 3ft 411 611 411 511 Loading Docks 611 *Portland Cement Concrete These sections are based on a design life of 20 years with normal mainte- nance. We recommend that asphalt concrete, base, and concrete paving be provid- ed and placed in accordance with the latest edition of "Standard Specifica- tions for Public Works Construction". We recommend that mix designs for the. asphalt concrete and the PCC be made by engineering companies specializing in these types of work, and that the paving operations be inspected by a qualified testing laboratory. Poinsettia Asso~ciate* Project No. 541681-PROl June 23, 1986 Page 5 Woodvmrd-Clyde Consukarft We recommend that adequate surface drainage be provided to reduce pond- ing and infiltration of water into the subgrade materials. We suggest that paved areas have a minimum, gradient of 1 percent. It is important to provide adequate drainage to reduce possible future ponding and distress of the pavement section. UNCERTAINTY AND LIMITATIONS We have observed only a very small portion of the pertinent soil and groundwater conditions. The recommendations made herein are based on the assumption that soil conditions do not deviate appreciably from those found during our field investigation. We recommend that Woodward-Clyde Consultants review the foundation and grading plans to verify that the intent of the recommendations presented herein has been properly inter- preted and incorporated into the contract documents. We further recom- mend that Woodward-Clyde Consultants observe the site grading, subgrade preparation under concrete slabs and paved areas, and foundation exca- vations to verify that site conditions are as anticipated or to provide revised recommendations if necessary. If the plans for site development are changed, or if variations or undesirable geotechnical conditions are encountered during construction, we should be consulted for further recommendations. This report is intended for design purposes only and may not be sufficient to prepare an accurate bid. California, including San Diego, is an area of high seismic risk. It is generally considered economically unfeasible to build a totally earth- quake-resistant project; it is therefore possible that a large or nearby earthquake could cause damage at the site. Geotechnical engineering and the geologic sciences are characterized by uncertainty. Professional judgements presented herein are based partly on our understanding of the proposed construction, and partly on our general experience. Our engineering work and judgements rendered meet current professional standards; we do not guarantee the performance of the project in any respect. Inspection services allow the testing of only a small percentage of the fill placed at the site. Contractual arrangements with the grading contractor should contain the provision that he is responsible for excavating, placing, and compacting fill in accordance with project specifications. Inspection by the geotechnical engineer during grading should not relieve the grading contractor of his primary responsibility to perform all work in accordance with the specifications. This firm does not practice or consult in the field of safety engineering. We do not direct the contractor's operations, and we can not be respon- sible for the safety of personnel other than our own on the site; the safety of others is the responsibility of the contractor. The contractor Poinsettia Associate* Project No. 541681-PROl June 23, 1986 Page 6 Woodward-Clyde Consultants should notify the owner if he considers any of the recommended actions presented herein to be unsafe. If you have any questions, please give us a call. Very truly yours, WOODWARD-CLYDE CONSUL ANTS Joseph G. Kocherhans R.E. 23060 JGK/BRS/cyh OF ESS/ -in No.23060 Ax -Ji - J4 clo, OF C, 0 Q~ (D 4T 0 4) m to u W6 W c 4- 0 to co a co m ix t ul 4CC m 44 .. 0 c U) ul t C 0 Lu C -C 'o Im CL oo w 4), qj Ln E E CL r- ui I- f 0 0 (D — LU CL > > (4 -0 Z 0 AC z u 4- 40- 40- z ui 0 -0 -0 C 0 0 0 C C C C .2 m '& 06 0 AU AU M . to ta C C '0 -0 .0 J2 to A M -0 E c . c z LU u Lu 1 0 16i w w z INI Project No. 541681-101 0 Woodward-Clyde Consultants APPENDIX A Four exploratory test pits were advanced at the approximate locations shown on the Site Plan (Figure 1). The pits were dug on May 29, 1986 with a 24-Inch bucket backhoe under the direction of a geologist from our firm. Samples of the soils encountered were obtained from the test pits in sacks, and transported to the laboratory for examination and testing. -1- Location Boring Number Elevation DEPTH IN TEST DAT!__JOTHER I TESTS] SAMPLE SOIL DESCRIPTION I I 'MC I 'DD I iR8C FEET NUMBER 12 110 65 Very dense, moist, b rown silty sand (SM) d 6 WATER LEVEL At time of drilling or as indicated. SOIL CLASSIFICATION Soil Classifications are based on the Unified Soil Classification System and include color, moisture and consistency. Field descriptions have been modified to,refi,ect results of laboratory analyses where appropriate. DISTURBED SAMPLE LOCATION Obtained by collecting the augler cuttings in a plastic or cloth bag. DRIVE SAMPLE LOCATION MODIFIED CALIFORNIA SAMPLER Sample with recorded blows per,foot was obtained with a Modified California drive sampler (7' inside diameter, 2.5" outside diameter) lined with sample tubes. The sampler was driven into the soil at the bottom of the hole with a 140 pound hammer failing 30 inches. STANDARD PENETRATION SAMPLER Sample with recorded blows per foot was obtained using standard split spoon sampler (IV Inside.diameteri 2- utside diameter). The sampler was driven Into the soil at the bottom of the hole with a 140 pound hammer falling 30 Inches and the sample placed In a plastic bag. INDICATES SAMPLE TESTED FOR OTHER PROPERTIES GS — Grain Size Distribution , CT — Consolidation Test LC— Laboratory Compaction UCS— Unconfined Compression Test Test SDS -Slow Direct Shear Test PI — Atterberg Limits Test DS — Direct Shear Test ST — Loaded Swell Test TX— Triaxial Compression Test CC — Confined Compression 'R'— R—Value Test NOTE: In this column the results of these tests may be recorded where applicable. BLOW COUNT Number of blows needed to advance sampler one foot or as indicated. DRY DENSITY See Note 2. Pounds per Cubic Foot MOISTURE CONTENT Percent of Dry Weight NOTES ON FIELD INVESTIGATION 1. REFUSAL indicates the inabilitV to extend excavation, practically. with equipment being used in the investigation. KEY TO LOGS POINSETTIA VILLAGE _T_ DRAWN BY: ch CHECKED 111Y:,~')It [ PROJECT mo: 541681-PROl DATE. 6-19-86 FIGURE NO:. A WOOOWARO-CLYOE CONSULTANTS 0 0 Test Pit 1 ADnroximate El. 68' DEPTH IN TEST DATA 100THER I SAMPLE S OIL DE'SCRIPTION - I *BC I FEET TESTS NUMBER Moist, light red brown, medium grained GS 1-1 sand FILL GS 1-2 Moist, light brown, fine to medium sand FILL 5 GS,PI 1-3 Dense, moist, reddish brown, clayey sand with silt (SC-SM) SANTIAGO FORMATION Dense, moist, brown and gray brown mottled, clayey sand with gray clay seams (SC) 101 Bottom of Hole SANTIAGO FORMATION 15 Test Pit 2 Approximate El. 661 DEPTH IN FEET TEST DATA *OTHER TESTS SAMPLE NUMBER I SOIL DESCRIPTION I I -MC I -DDT".SC moist, reddish brown, silty sand FILL 2-1 Dense, moist, deep brown and gray brown, 5- GS,PI 2-2 clayey sand with gray clay seams (SC) SANTIAGO FOP14ATION Bottom of Hole 10 15 *For description of symbols, see Figure A-1 LOG OF TEST PITS 1 AND 2 POINSETTIA VILLAGE I FIGURE NO: A DRAWNIBY: ch I CHECKED BY:,,~~Lj PROJECTNO: 541681—PROI I DATE- 6-19-86 —2 WOOO,WARO-CLYOE CONSULTANTS 9 Test Pit 3 Approximate El. 661 Moist, reddish brown, silty sand FILL Dense, moist, brown and gray brown, clayey sand with gray clay seams (SC) SANTIAGO FORMATION SOIL DESCRIPTION DEPTH IN FEET TEST DATA *OTHER TESTS I 13AMPLE NUMBER I I -MC I -DD I -BC I 5 I , Bottom of Hole 10 15 Test Pit 4 Approximate El. 681 DEPTH IN TEST DATA *OTHER IIIAWLE I I IL SOIL DESCR PT'ION I --- [7*MC D~. I - BC -I FEET TEMM NUMBER 5 GS,NPI L4-1 Moist, brown, silty sand FILL Dense, moist, light brown, silty sand (SM) SANTIAGO FORMATION Bottom of Hole 10 15 -1 1 1 1 1 *For description of symbols, see Figure A-1 LOG OF TEST PITS 3 AND 4 POINSETTIA VILLAGE ZI - ---T- - DRAWNjBY: ch I CHECKED BY: ~11(rPROJECT NO: 541681-PROl DATE: 6-19-86 FIGURE Z. A-3 WOODWARD-CLYDE CONSULTANTS Project No. 541681-al Woodward-Clyde Consultants APPENDIX B LABORATORY TESTS The materials observed in the borings were visually classified and evalu- ated with respect to strength, swelling, and compressibility characteris- tics; dry density; and moisture content. The classifications were substan- tiated by performing grain size analyses on representative samples of the soils. "R"-value tests were performed on selected samples as an aid in the design of pavement sections. The results of the grain size and plasticity analyses are shown in FIgure B-1. The results of the "RII-value tests are also presented in Appendix B. -2- mm~lm lm~lm lm~lm lm~lm lm~lm no Immollm lm~lm lm~lm lm~mm lm~mm lm~mm lm~mm lm~lm lm~lm lm~lm mm~mm vm~mm ~Mmm~ ~Mmm~ ~Mmm~ ~Mmm~ ~Mmm~ ~Mmm~ ==mom ~Mmm~ ~Mmm~ ~Mmm~