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HomeMy WebLinkAboutCT 80-39; Laguna Riviera; Soils Report; 1980-04-07AL 4~ .i. . ~CC J L L L I 1 SOIL INVESTIGATION ‘for L.$GUNA RIVIERA Carlsbad, California For i KAMAR CONSTRUCTION COMPANY, INC. - Carlsbad, California .- - BY GEOCON, INCORPORATED San Diego, California April, 1980 ENGINEERING DEPT. LIBRARY City of Carlsbad 2075 Las Palmas Drive CarfsbaQ CA9200~!J-4859 L i I i L i .i i .L L L L L L L L L L, aim ., .- GEOCON ENGINEERS AND GEOLOGISTS . CONSULTANTS IN THE APPLIED EARTH SCIENCES INCORPORATED File No. D&2192-JO1 April 1, 1980 Kamar Construction Company, Inc. 325 Elm Street Carlsbad, California 92008 Attention: Mr. Jerry Rombotis Subject: Laguna Riviera Carlsbad, California SOIL INVESTIGATION Gentlemen: In accordance with your request we have performed a soil in- vestigation for the subject project. The accompanying report presents the findings from our study and our conclusions and recommendations based on those findings. general, the site was found to be suitable 'for development DrODOSed. Drovided minor remedial measures recommended here- In as in &e*followed. If you have questions concerning this report, or if we may be of further service, please do not hesitate to contact our office, Respectfully submitted, MSC:JEL:lm copies: (4) addressee W 6645 CONVOY COURT . SAN DIEGO. CALIFORNIA 92111 . PHONE (714) 292-5100 i File No. D-2192401 April 7, 1980 : I ! .I SOIL INVESTIGATION I /- Purpose and Scope The purpose of our investigation was to evaluate the surface and subsurface soil conditions at the site and, based on con- - ~- ditions encountered, to provide reconxnendations for development of the site to receive the proposed one- or two-story, wood- frame residential- structures. - The investigation consisted of a site reconnaissance and the drilling of three exploratory borings. Laboratory tests were - performed on selected representative soil samples obtained at various depths in the test borings to evaluate pertinent phy- sical properties of the soil types encountered. The conclusions and recommendations that follow are based on an analysis of the data obtained from our field exploration and laboratory tests and on our experience with similar soil conditions. - Location and Description of Site and Project The irregular-shaped 3.85 acre site is located along the west side of Valencia Avenue and Hillside Drive between Park Drive and Neblina Drive in Carlsbad, Calif~ornia. - - - -l- L : ,’ File No. D-2192-JO1 April 7, 1980 The property has been partially graded in conjunction with testing and observation services provided by Woodward-Gizienski and Associates as documented in their report of April 5, 1972 titled "Laguna Riviera Unit 5, Offsite Fill Areas A and B, Carlsbad, California". L The previous grading consisted primarily of placement of excess material from adjacent units of the Laguna Riviera subdivision in the low-lying areas along the eastern portion of the subject property. i - - The western portion of the site is ungraded and in its natural state. Vegetation at the site consists of moderate growths of native weeds, grasses, and chaparral. - - Topographically, the site ranges in elevation from a high of approximately 120 feet above mean. sea level near its north end to a low of about 20 feet above mean sea level at the south end. It is proposed to complete the grading of the site to receive approximately 15 one- and two-story, wood-frame, single-family residences. -2- GEOCON -I ‘* File No. D-2192-JO1 April 7, 1980 - The locations and descriptions contained herein are based upon a site reconnaissance and~upon preliminary site and development plans provided to us by Kamar Construction Company, Inc. If project details vary significantly from those outlined, this firm should be notified for review and possible revision of recommendations presented herein prior to final design sub- mittal. Field Investigation The field investigation was performed on March 24, 1980 and consisted of~a site reconnaissance by our engineering geologist and the excavation of three exploratory borings at the approxi- mate locations shown on the attached Site Plan. - The borings were drilled to depths ranging from 15 to 16 feet below existing grade utilizing a Mobile B-50 trucK-mounted ro- tary drill rig equipped with six-inch diameter continuous flight auger. Relatively undisturbed samples were obtained by driving a three-inch O.D. split tube sampler into the undisturbed soil mass with blows from a 140 pound hammer failing 30 inches. The sampler was equipped with one-inch high 2-3/8-inch diameter brass rings to facilitate sample removal and testing. Dis- turbed bulk samples were also taken. -3- GEOCON _..^^_“^_ .--I L L - - - - A - - - - - - - . . File No. D-2132-30' Anril 7 1QRr-l LEGEND @LLOCATI~N of n3r BORING SITE PLAN AND LOCATION OF TEST BORINGS LAGUNA RIVIERA Carlsbad, California =lGlJRE 1 GEOCON, INCORPORATED I”“‘4 GEOCON .UCnlenP.,.ln File No. D-2192-JO1 April 7, 1980 L During the investigation, the soils encountered were continu- ously examined, visually classified, and logged. Logsof the test borings are presented on Figures 2 through 4 of Appendix A. The logs depict the depth and description of the various soil types encountered and include the depths at which samples - were taken. - Laboratory Tests Laboratory tests were performed in accordance with generally accepted test methods of the American Society for Testing and Materials (ASTM) and other suggested procedures. Selected relatively undisturbed drive samples of natural soils and ex- isting fill soils were tested for their in-place dry density, moisture content, shear strength, and expansive potential. The maximum'dry density and optimum moisture content of a disturbed bulk sample were determined in accordance with ASTM Test Method D1557-78. The results of our laboratory tests are summarized in tabular form in Appendix A. In-place moisture-density relationships are alas presented on the Logs of Test Borings. - - -5- File No. D-2192-JO1 April 7, 1980 Soil Conditions As mentioned earlier, the,eastern portion of the site was graded - / to its present configuration in the past. Results of in-place density tests recorded in the referenced Woodward-Gizienski re- port indicate that the existing fill material was compacted to at least 90 percent of maximum dry density. Our moisture-density tests of undisturbed drive samples indicate similar results. The western portion of the site is presently in its natural state. The existing fill material consists of intermixed and layered medium dense/medium hard, silty and clayey sands and sandy clays. A localised area of shallow uncompacted fill was encountered near the north end of the site. Fill depths of up to seven feet were encountered in our borings elsewhere on the site. Topsoils, colluvium and formational soils underlie the existing fill. The topsoils and colluvium consist of medium dense, humid to moist, silty and clayey sands. -6- GEOCON .I- . ’ ,- - .-. File No. D-2192-JO1 April 7, 1980 Formational soils underlying the topsoil are characterized by dense, silty and clayey sands with occasional clay layers. No groundwater was encountered during the course of our inves- tigation. - Geocon, Incorporated assumes no responsibility for the perform- ance of fill placed under testing and observation services pro- vided by others. . - - - - - -7- GEOCON File No. D-2192401 April 7, 1980 - - - .- - CONCLUSIONS AND RECOMMENDATIONS General 1. It is our opinion that the site is suitable for the pro- posed residential development provided the recommendations of this report are carefully followed. 2. A localized area of relatively loose fill is present near the north end of the site and will require recompaction as recormnended below. Additionally, we recommend that the ground surface of the existing compacted fill be scarified and recom- pacted to a depth of 12 inches prior to the placement of addi- tional fill. Grading -. .I - 3. All grading should be performed in accordance'with Chapter 70 of the Uniform Building Code and the "Recommended Grading Specifications" presented in Appendix B. Where the recommen- dations of Appendix B conflict with those of this section of the report, this section of the report taken precedence. - -8- GEOCON *NCQRPOR**BD 1,’ i . . - - - 2 - - File No. D-2192-JO1 April 7, 1980 4. The existing loose fill at the north end of the site should first be removed to a depth where natural ground is exposed (see Figure 1). The project soil engineer or his representative should observe the overexcavation operations to ascertain that all of the loose fill has been removed. The exposed natural ground should then be scarified to a depth of 12 inches, moisture con- titioned, and recompacted to at least 90 percent of maximum dry density. Any areas of excessively wet near-surface material should be removed or aerated prior to the placement of addi- tional fill. ~5. The remainder of the site to receive fill should, likewise, be scarified to a depth of 12 inches, moisture conditioned, and recompacted. If additional fill is to be placed on the existing fill, it may then be placed and compacted in layers until final elevations are reached. Layers of fill should be'no thicker than will allow for adequate bonding and compaction. A thick- ness of six to eight inches may be assumed to be satisfactory for this project. All fill should be compacted to at least 90 percent of maximum dry density. -9- - - - GEOCON . ..^^__^_ .,.m.. 1’. , File No. D-2192-JO1 April 7, 1980 - - .I 6. If material is to be imported to the site, it should be approved for use by the project soils engineer prior to delivery. Foundations 7. The site is suitable for the use of isolated spread footings or continuous strip footings if graded as recommended above. Such footings should be at least 12 inches in width and should extend at least 12 inches below lowest adjacent pad grade. If expansive materials are present within 30 inches of finish grade, footing depths should be increased to 24 inches. 8. It is recommended that minimum footing reinforcement consist of two continuous No. 4 steel reinforcing bars placed horizon- tally in the footings, one near the top of the footing and one near the bottom. The above minimum reinforcement is based on .- soil characteristics and is not intended to be inalieu of rein- forcement necessary for structural considerations. i i 9. An allowable bearing capacity of 1800 psf may be used for foundations constructed as recosunended above. The allowable bearing capacity is for dead plus live loads and may be in- creased by one-third for transient loads due to wind or seismic forces. - -lO- GEOCON IUCOIPOIATEr, File No. D-2192-301 April 7, 1980 Concrete Slabs-on-Grade 10. Concrete slabs-on-grade should have a nominal thickness 2 of four inches and be underlain by at least four inches of clean sand. Reinforcement should consist of 6x6-10/10 welded wire mesh throughout. Where moisture sensitive floor coverings are,planned, the slab should be underlain by a visqueen mois- ture barrier. A two-inch-thick layer of sand or gravel should be provided above the visqueen to allow proper concrete curing. Slopes 11. Cut and fill slopes constructed of onsite materials should be stable against deep-seated failure if graded at inclinations of 2.0 horizontal to 1.0 vertical or flatter. - Site Drainage and Moisture Protection - - - - - 12. Adequate drainage provisions are imperative.' Under no circumstances should water be allowed to pond adjacent to foot- ings. The site should be graded such that storm waters and irrigation excess drain away from structures and into swales or other controlled drainage facilities. -ll- GEOCOJV File No. D-2192-JO1 April 7, 1980 13. Roof downdrains should empty into splashblocks and the water should be directed away from the structures into con- trolled drainages. - - -- - -12- GEOCON *NEOrtPOR*TI* File No. D-2192-JO1 April 7, 1980 LIMITATIONS AND UNIFORXITY OF CONDITIONS ,.- 1. The recouunendations of this report pertain only to the site investigated and are based upon the assumption that the soil conditions do not deviate from those dis- closed in the borings. If any variations or undesirable conditions are encountered during construction, or if the proposed construction will differ from that planned at the present time, Geocon, Incorporated should be no- tified so that supplemental recommendations can be given. - - 2. This--report is issued with the understanding that it is the responsibility of the owner, or of his representa- tive, to ensure that the information and recommendations contained herein are brought to the attention of the arch- itect and engineer for the project and incorporated into the plans, and that the necessary steps are taken to see that the contractor and subcontractors carry out such recommendations in the field. 3. The findings of this report are valid as of the pres- ent date. However, changes in the conditions of a property - - -13- GEOCON L File No. D-2192-JO1 April 7, 1980 - .- L I L - I i I i - can occur with the passage of time, whether they be due to natural processes or the works of man on this or adjacent properties. In addition, changes in applicable or appro- priate standards may occur, whether they result from leg- islation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or par- tially by changes outside our control. Therefore, this report is subject to review and should not be relied upon after a period of three years. ..- -14- GEOCON *NCORPOR*TErJ APPENDIX A 1 ‘. -- - .- i - -1 i - - .- - - File No. D-2192-JO1 April 7, 1980 TABLE I Summary of In-Place Moisture-Density and Direct Shear Test Results Sample Depth No. ft. Dry Density pcf Moisture Content % l-l 5 111.2 13.2 1-3 10 107.1 14.9 2-l 2 115.1 6.8 2-2 5 114.6 12.5 2-3 10 113.8 7.6 3-2 5 112.9 9.2 3-3 10 114.3 10.8 3-4 15 122.1 8.9 Unit Cohesion psf A-l 223 -- 257 -- -- -- -- Angle of Shear Resistance degrees 41 -- 34 -- -- -- -- -- GEOCON ,NCORPORATED - - -- . . .- .~ _. - .,.. I ~. -. .- -~ -... File No. D-2192-JO1 April 7, 1980 TABLE II Summary of Laboratory Compaction Test Results A.S.T.M. D1557-70 Sample Number 3- Max. Dry Optimum Depth Density Moisture ft. Description pcf % dry wt. 1-4 Dark brown, Clayey 129.7 9.7 SAND TABLE III Summary of Laboratory Expansion Test Results Moisture Content - Expansion (I-) Before After or Test Test Dry Settlement(-) Sample Depth Density Surcharge No. Description ft. % % pcf % psf, 3-2 Dark brown, 5 *9.2(1.9) 16.9 112:9 +1.7 150 Clayey SAND *Air-dry moisture content in parentheses A-2 GEOCON *rdCORPOI*TLrJ I - -~ - ,.- - _ .A - - - - - - - - - Fil e No. D-2192-501 Apr - l"RE afxa - -1 -2 -3 z : 0: .i/ k: ‘,, 1;f.l i flj 1;;. . . ., ;/; r .: . . ‘. 1, 2.‘;‘: _‘_ C’J ‘., ;I-:‘: I .’ .. .;! .r. ‘. ? 1 IA ‘W 4 8, c i .; .i I: ‘,’ ‘. 1 ,:: ;( ‘, ;‘: /. ‘.. / I.’ : i- 1981 - I*bS2 - -- 12 -- $9 BORING NO. 1 rnT r E LLL Medium loose, very moist, light gray-brown, Clayey, medium to coarse SAND with asphalt E FORMATIONAL SOILS. Medium loose, very moist, orange- brown, Clayey medium SAND L- becomes medium dense, Silty L-------- Dense. very moist. orange-brown, Clayey! medium to-very Eoarse SAND with occasional layers of Sandy CLAY BORING TERMINATED AT 15.0 FEET ast Boring 1 A-3 111.2 BULK 107.1 13.2 i2sMPL 14.9 GEOCON i - File No. D-2192-JO1 Anvil 7 19811 ..i I- a I -1 -1 .I -1 L F MSCRlPllON Medium dense, very moist, gray- brown, ~Clayey, medium to very coarse SAND mixed with medium dense, humid, brown, Silty medium SAND edium dense, humid, dark brown, ilty medium SAND Dense, moist, light yellow-brown, slightly Clayey, Silty, medium tom BORING TERKIMATED AT 15.0 FEET -2 -..-- 3 T -- -c -t--L n--z-- ? ‘L,guLe J, IAJ,~ “L LezSL DLJLLq, L A-4 GEOCON _..^ ^__^ - .--- - - - - - - _i - - I’ 4 , -’ .; - File No. D-2192-~01 April 7, 1980 ,’ .; ;“‘. : . : 2.’ t BORING NO. 3 ,_ .___.-.I FILL Medium dense/medium h:Iral, w,ry moist, dark brown, Cl;tyv ::AfllJ/ Sandy CLAY (mixed) ~OPSOILlCOLLUVI~! Medium dense, moist, bl.~ck-~hrrJwn Ckw, coarse to very il)i~f"~ SAND BORIN(; TER‘!I:;,jTz3 ,fT 11. !i i’!::ET Figure 4, LO% ,,I 'I'~*:I( 4. 3 10.8 BULK S&IPL APPENDIX B File No. D-2192-JO1 April 7, 1980 RECOMMENDED GRADING SPECIFICATIONS for LAGUNA RIVIERA Carlsbad, California - - - I - 1.1 1.11 1.12 1.13 2.1 2.11 General Description These specifications have been prepared for grading and site development of the Laguna Riviera located along the west side of Valencia Avenue and Hillside Drive between Park Drive and Neblina Drive in Carls- bad, California. Geocon, Incorporated, hereinafter described as the soil engineer, should be consulted prior to any site work connected with site develop- ment to ensure compliance with these specifcations. These specifications shall only be used in conjunc- tion with the soil report of which they are a part. This item shall consist of all clearing and grubbing, preparation of land to be filled, filling of the land, spreading, compaction and control of the fill, and all subsidiary work necessary to complete the grading of the filled areas to confrom with the lines, grades and slopes as shown on the accepted plans. The soil engineer shall test and observe all grading operations. In the event that any unusual conditions not covered by the special provisions are encountered during the grading operations, the soil engineer shall be contacted for further information. Tests The standard test used to define maximum density of all compaction work shall be the ASTM Test Procedure D1557-78. All densities shall be expressed as a relative compaction in terms of the maximum density obtained in the laboratory by the foregoing standard procedure. B-l GEOCON - - File No. D-2192-JO1 April 7, 1980 - - .- 3.1 3.11 3.12 3.13 3.14 3.15 3.16 Clearing, Grubbing, and Preparing Areas to be Filled Any trees not utilised in landscaping! structures, weeds, and other rubbish shall be removed, plled, or otherwise disposed of so as to leave the areas that have been dis- turbed with a neat and finished appearance, free from unsightly debris. Any septic tanks, if encountered, and debris must be removed from the site prior to any building, grading or fill operations. Septic tanks, including al.1 connecting drain fields and other lines, must be totally removed and the resulting depressions properly reconstructed and filled to the complete satisfaction of the sup,er- vising soil engineer. All water wells on the site shall be capped according to the requirements of the San Diego County Health De- partment. The strength of the cap shal.1 be at least equal to the adjacent soil. The final elevation of the top of the well casing must be a minimum of 36 inches~ below any adjacent grade prior to any grading of fill . operations. All buried tanks, if encountered, must be totally removed and the resulting depressions properly recon- strutted and filled to the complete satisfaction of the supervising soil engineer. All vegetable matter and soil designated as unsuitable by the soil engineer shall be removed under the direc- tion of the soil engineer. The then exposed surface shall then be plowed or scarified to a depth of at least eight inches and until the surface is free from ruts, hunmocks, or other uneven features which would tend to prevent uniform compaction by the equipment to be used. The original ground upon which the fill is to be placed shall be plowed or scarified deeply, and where the slope ratio of the original ground is steeper than 6.0 hori- zontal to 1.0 vertical, the bank shall be stepped or benched. At the toes of the major fills and on the side- slope fills, the base key shall be, as described else- where in this report, at least 10 feet in width, cut at B-2 GECOCON s*rnaena.*rn - - - I - - File No. D-2192-JO1 April 7, 1980 3.17 4.1 4.11 4.12 5.1 5.11 5.12 least three feet into the undisturbed or native soil, and sloped back into the hillside at a gradient of not less than two percent. Subsequent keys should be cut into the hillside as the fill is brought up the slope. The construction of subsequent keying operations shall be determined by the soil engineer during grading oper- ations. Ground slopes which are flatter than 6 to 1 shall be benched when considered necessary by the soil. engineer. After the foundation for the fill has been cleared, plowed, or scarified, it shall be disced or bladed un- til it is uniform and free from large clods; brought to the proper moisture content by adding water or aer- ating; and compacted to relative density of not less than 90 percent. Materials Native soil, free of organic material and undesirable deleterious material, may be used as fill. Native soil which is expansive shall not be placed on the top two feet of building pads without the approval of the soil engineer. The materials for fill shall be approved by the soil engineer before commencement of grading operations. Any imported material must.,be approved for use before being brought to the site. The materials used shall be free from vegetable matter and other deleterious material! and be nonexpansive. Expansive soil is defined as solI which expands more than 3.0 percent when saturated at 90 percent relative compaction and optimum moisture content under a surcharge of 150 psf. Placing, Spreading, and Compacting Fill Material The selected fill material shall be placed in layers which when compacted shall allow adequate bonding and compaction. Each layer shall be spread evenly and shall be thoroughly blade mixed during the spreading to ensure uniformity of material in each layer. Uhen the moisture content of the fill material is be- low that specified by the soil engineer, water shall B-3 .- File No. D-2192-JO1 April 7, 1980 - - - - - - - - 5.13 5.14 5.15 5.16 5.17 5.18 be added until the moisture content is as specified to assure thorough bonding during the compaction process. When the moisture content of the fill material is above that specified by the soil engineer, the fill material shall be aerated by blading or other satisfactory methods until the moisture content is as specified. After each layer has been placed, mixed, and spread evenly, it shall be thoroughly compacted to a relative compaction of not less than 90 percent. When fill material includes rock, no rocks will be allowed to nest, and all voids must be carefully filled with small stones or earth and properly compacted. MO rocks larger than six inches in diameter will. be permitted in the fill. Compaction shall be by sheepsfoot rollers, multiple- wheel pneumatic-tired rollers, or other types of acceptable compacting rollers. Rollers shall be of such design that they will be able to compact the fill to the specified moisture content range. Rolling of each layer shall'be continuous over its entire area and until the required density has been obtained. Field density tests shall be made by the soil engineer. Where sheepsfoot rollers are used, the soil may be disturbed to a depth of several inches. Density tests shall be taken in compacted material below the disturbed surface. When these tests indicate that the density of any layer of fill or portion thereof is below the required 90 percent density, the particular layer or portion shall be reworked until the r.equired density has been obtai.ned. The fill operation shall be continued in compacted layers, as specified above, until the fill has been brought to the finished slopes and graded as shown on the accepted plans. Fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment. Compaction opera- tions shall be continued until the slopes are stable. - B-4 GEDCON INCORIORATPD - File No. D-2192-JO1 April 7, 1980 - - 6.12 - - - - - 5.19 6.1 6.11 6.13 6.14 7.1 7.11 8.1 8.11 All earthmoving and working operations shall be con- trolled to prevent water from running into excavated areas. All water shall be promptly removed and the site kept dry. Disposal of Oversize Rock Oversize rock shall be either exported from the site, used for landscaping purposes, or placed in designated nonstructural fill areas. Prior to grading, the soil engineer shall be consulted to approve any proposed nonstructural fill areas. In general, nonstructural fill areas will be acceptable if located outside of the "zone of influence" of proposed structures; e.g. rear yard fills at least 15 feet from structures and beneath street areas (deeper than pro- posed utility lines). Oversize rock shall not exceed'four feet in greatest dimension, shall be placed in lifts not exceeding four, and shall be placed in a manner that will not produce "nesting" of the,rock. The voids between the rocks shall be completely filled with fine granular material. No oversize rock shall be placed within four feet of finish lot grade nor within the anticipated depth of utility lines, whichever is deeper. Engineering Observation Field observations by the soil engineer shall be made during the fill. and compaction operations so that he can express his opinion regarding the conformance of the grading with the accepted specifications. Seasonal Limits No fill material shall be placed, spread, or rolled while it is at an unsuitable high moisture content, nor during unfavorable weather conditions. When the work is interrupted by heavy rain, fill operations shall not be resumed until field tests,by the soil engineer indicate that the moisture content and den- sity of fill are as previously specified. B-5 GEOCON *?JCORPOR*T*D