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Home My WebLink AboutCDP 04-50; RHODES RESIDENCE; LIMITED SITE INVESTIGATION; 2005-07-20).. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. 10925 HARTLEY ROAD, SUITE "I" SANTEE, CALIFORNIA. 92071 (619) 258-7901 . Mr. Glenn Rhodes 1200 Chinquapin Avenue Carlsbad, California 92008 Fax 258-7902 Subject: Limited Site Investigation July 20, 2005 Project No. 05-1106G6 Proposed Two-Story Single Family Residence 1200 Chinquapin Avenue City of Carlsbad, California Dear Mr. Rhodes: In accordance with your request, we have performed a limited investigation of the soil qonditions at the subject site to provide the soil engineering criteria for site grading and recommend an appropriate foundation system for the proposed residence . .Our investigation has found that the site is underlain by topsoil and colluvium to a maximum depth of approximately 3 feet below existing grade. The colluvium is underlain by medium dense to dense sandstone of the Terrace Deposits Formation to the explored depth of 5.0 feet. It is our opinion that the proposed development is feasible provided the recommendations herein are implemented in the design and construction. Respectfully submitted, Mamadou Saliou Diallo, P.E. RCE 5-4071 MSD/md --- j .. -RHODES PROJECT NO. 05-1106 • SITE DESCRIPTION AND PROPOSED CONSTRUCTIO~ The subject site is located on the north side of Chinqqapin Avenue, in the City of Carlsbad, California. The site is occupied by a single-story house along with a 12-foot deep abandoned seepage pit. The property slopes gently to the west. It is our understanding that the existing house will be demolished and .replaced with a two-story, wood-fratnec;l. single-family residence~- . The structure will be founded on continuous footings with a slab- on-grade floor. FIELD INVESTIGATION On July 8, 2005, three (3) exploratory borings were drilled to a mc).ximum depth of approximately 5. 0 feet with a hand auger. The approximate locations of the borings are shqwn on the attached Plate No. 1, entitled "Location of Exploratory Borings". A continuous log of the soils encounte·red was recorded at the time of drilling and is shown on Plate No. 2 entitled "Summary Sheet". The soils were visually and texturally classified according to the filed identification procedures set forth on the attached P~ate ~o .. 3 entitled "USCS Soil Classification" ... Following the field exploration, laboratory testing was performed to evaluate the pertinent engineering pr6perties of the foundation materials. The laboratory-testing ptogtam included moisture and density, maximum density and optimum moisture content, particle sizE; analysis and expansion index· tests. These tests were performed in general accordance with ASTM standards. Plate No. 2 and Page L-1 rrovide a summary of the laboratory test results. SUBGRADE CONDITIONS Topsoil and colluvium were encountered to a maximum depth of approximately 3 feet below existing g:i;-ade. '.I'hese soils were composed of sand and silt mixture with a loose to medium dense consistency and a low moisture content. Medium dense to dense sandstone of the Terrace Deposits· Formation was underlying the colluvium to the maximum explored depth o.f approximately 5 .. 0 feet. EXPANSIVE SOILS An expansion index test · was perforroed on a select sample of the colluvium to determine volumetric change characteristics with change in moisture content. An expansion index of 2 indicates a very low expansion potential for the foundation soils. 3 • -RHODES PROJECT NO. 05-1106G' . GRADING AND EARTHWORK Site grading should begin with clearing and grubbing, e.g.· the removal of v~getation, · topsoil and deleterious materials. All colluvium under the proposed structure should be overexcavated, moisture · con.di tioned within 2 perc~nt over the optimum moisture content and compacted to a minimum of 90 percent relative compaction (ASTM. D1557) . The overexcavation should extend to the dense sandstone of. the Terrace Deposits Formation and at least 5 feet beyond proposed perimeter footings. Proper keying and benching of the subgrade along the adj ac.ent slope to the east shquld be observed during the grading operation. To prevent any transition between cut and fill within the building pad, th~ cut portion of the pad should be overexca,vated to a minimum depth of three feet below finish pad grade, moisture conditioned ahd compacted as above. The actual depth and extent of removal should be eva.luated in the .field at the time of excavation by a representat'ive of this firm. Grading should be performed in accordance with the attached Appendix A. rn addition, the abando:r;ied seepage pit should be properly cleaned out and backfilled with compacted fill mater.ials or a concrete slurry mix. FOUNDATIONS AND SLABS a. Continuous footings are suitable for use and should e·xte.nd a minitnµrn of 18 inches for· the two-story · residence · into properly. compacted fill soils~ These footings should be at least 15 inches in width and reinforced with four #4 steel bars; two bars placed near t.he top of the footings and the other two bars placed near the bottom of the footings b. Interior concrete floor slabs sho.uld be a minimum of 4 inches thick. Reinforcement should consist of #3 bars placed at 16 inches on center each way within the .middle third of the slab by supporting the steel on chairs or concrete blocks "dobies". The slab should be underlain· by 2 inches of clean sand· over a lO~mil vis queen moisture barrier. The effect of concrete shrinkage will result in cracks in virtually all copcrete slabs. To reduce the extent of shrinkage, the concrete should be placed at a maximum of 4-inch slump. The minimum steel recommended is not intended to prevent shrinkage cracks. 5 e. e RHODES PROJECT NO. 05-.J 106G6 c. Where moisture sensitive floor coverings are anticipated over the slab, the 10-mil plastic moisture barrier sh6uld be underlain by a capillary break at least 2 inches thick, consisting of coarse sand, gravel or crushed rock not exceeding 3/4 inch in size with rio more than 5 percent passing the #20,0 s.ieve. d. An allowable soil bearing value of 1,725 pounds per square foot may be used for the design of the above footings founded into the properly compacted fill. This value may be increased by 300 psf for each additional foot of width or depth to a maximum value of 4,500 lb/ft2 as set forth in the 1.997 Edition of the Uniform Building Code, Table No. l&-I-~. e. Lateral resistance to horizontal movement may be provided by the soil passive pressure and the friction of concrete to soil. An allowable passive pressure of 250 pounds per square foot per foot of depth may be used. A coefficient of friction of 0.35 is recommended. The soils passive pressure as well as the bearing value may be increased by 1/3 for wind and seismic loading. RETAINING WALLS Cantilevered retaining walls should be designed for an "active" lateral earth pressure of 35 psf/ft (35 pcf EFP) for approved granular backfill and level backfill conditions. Where cantilevered walls support 2:1 (hor:vert) sloping backfill, the equivalent active fluid pressure should be increased to 45 pcf. Cant~lever walls subject to uniform surcharge loads should be designed for an additional uniform lateral pressure equal to· qne-third (1/3) the anticipated surcharge pressure. Restrained walls should be designed utilizing an "at-rest" earth pressure of 58 psf/ft (58 pcf EFP) fbr ~pproved granular and level backfill. Restrained walls subject to uniform surcharge loads should be designed for an additional uniform lateral pressure equal to one- half {1/2) the anticipated surcharge. Retaining wall footings should be embedded a minimum of 18 inches below the lowest adjacent grade. Retaining walls that are to be located near the top of slopes should be designed to allow a minimum daylight distance of 7 feet laterally from the outside edge of the footing to the slope face. Soil design criteria, such as bearing capacity, passive earth pressure and sliding resistance as recommended under the Foundation and Slab Recommendations section, may be incorporated into the retaining wall design. The design and location of retaining walls 6 J.:' -RHODES PROJECT NO. 05-1106, should be reviewed by our firm for conformance with our recommendations. Footings should be reinforced as recommended by the structural engineer and. appropriate back drainag~ provided to avoid excessive hydrostatic wall pressures. As a :minimum we recornmend a fabric- wrapped crushed rock and perforated pipe system. At least 2 cubic feet per linear foot of free-drainage crushed rock should be provided. The remaining wall backfill should consist of approved granular tnate+:ial. This fill material should be compactec:;i to a minimum relative compaction of 90 percent as determined by ASTM D-1557 test method. Flooding or jetting of backfill should not be permitted. Granular backfill should be capped with a minimum 18 inches of relatively impervious fill to seal the backfill and prevent saturation. It should be noted that the use of heavy compaction equipment in close proximity to retaining structures can result in wall pressures exceeding design values and corresponding wall movement greater than that associated with active or at-rest conditions. In tpis regard, the contractor should take appropriate precautions during the backfill placement . . SETTLEMENT Settlement of compacted fill soils is normal and should be anticipated. Because of the type and thickness of the fill soils under the proposed footings and the light building loads, total a~d differential settlement should be within acceptable limits. TRENCH EXCAVATION AND BACKFILL Excavations for foundation and on-site utility trenches may be +nade vertically for shallow depths and must be either shored or sloped at 1H: 1V for depths greater than 4 feet. Utilities should be bedded and backfilled with clean sand or approved granular soil to a depth of at least one foot over the pipe. This backfill should be uniformly watered and compacted to a firm condition for pipe support. The remainder of the backfill should be on-site soils or non-expansive imported soils, which should be placed in thin lifts, moisture-conditioned and compacted to at least 90% relative compaction (ASTM D1557). 7 " _, -RHODES PROJECT NO. 05-11061 DRAINAGE .Adequate measures should be undertaken to properly finish grade the site after the structure and other improvements are in place, such that the drainage water within the site and adjacent properties is directed away from the foundations, footings, floor slabs and the tops of slopes via surface swales and subsurface dtains towards the natural drainage for this area. A minimum gradient of 1 percent is recommended in hardscape areas. For earth areas, a minimum gradient of 5 percent away from all structures for a distance of at least 5 feet should be provided. Earth swales should have a minimum gradient of 2 percent. Drainage should be di~ected to approved drainage facilities. Proper surface and subsurface drainage will be required to minimize the potential of water seeking the level of the bearing soils under the foundationsi footings and floor slabs, which may otherwise result in undermining and differential settlement of the structure and other improvements. FOUNDATION EXCAVATION OBSERVATION Foundation excavations should be observed by our representative prior to the placement of forms, reinforcement or concrete for -conformance with the plans and specifications and the intent of the recommendations herein. LIMITS OF INVESTIGAT.ION Our investigation was performed using the s.kill and degree of care ordinarily exercised, under similar circumstance.s, by reputable soils engineers and geologists practicing in this or similar localities. No other warranty, expressed or implied, is made as to the conclusions and professional advice included in this report. This report is prepared for the sole use of our client afid may not be assigned to others without the written consent of the client and ECSCE, Inc. The samples collected and used for testing, and the observations made, are · believed representative of site conditions; however, soil and geologic conditions can vary significantly between borings and surface exposures. As in most major projects, ~onditions revealed by construction ~xcavations may vary with preliminary findings. If this occurs, the changed conditions must be evaluated by a representative of ECSCE and designs adjusted as required or alternate desi.gns recommended. 8 --RHODES PROJSCT NO. 05-110606 This report is issued with the understanding that it is the responsibility of the owner, or of his representative to ensure that the information and recommendations contained herein are brought to the attention of the project archi.tect and engineer. Appropriate recommendations s.hould be incorporated into the structural plans. The necessary steps should be taken to see that the contractor and subcontractors carry out such recommendations in the field. The findings of this report are valid as . of this present date. However, changes in the conditions of a property can occur with the passage of time, whether they are due to natural processes or the works ·of man on this or adjacent properties. In addition, changes in applicable or appropriate standards may occur from legislation or the broadening of knowledge. Accorctingly, the findings of this report may be invalidated wholly or partially by changes outside of our control. Therefore, this report is subject to review and should be updated after a period of two years. Plates No. 1 through 3, Page L-1, References and Appendix A are parts of this report. Respectfully submitted, Diallo, P.E. 9 EAST COUNTY SOIL CONSULTATION & ENGINEERING, INC. 10925 HARTLEY RD .• SUITE I. SAN,cE, CA 9207 I (619.) 258-7901 F:ix (6 I 9) 258-7902 --~ ,, .. ' '-1--' .,f.... ~1'rf.· C/21/N~v'.-:Pl,V At/£. ----'---f DEPTH Surface OS 3.0' 5.0' DEPTH Surface 0.5' LO' · 2.0' 3.0' DEPTH. · Surface 0.5' 1.5' 3.0' -RHODES PROJECT NO. 05-1106,,. PLATEN0.2 SUMMARY SHEET BORINGN0.1 SOIL DESCRIPTION TOPSOIL brown, dry, loose, silty, fine sand with rootlets COLLUVIUM (Qal) brown, damp, loose to medium dense sand with silt TERRACE DEPOSITS FORMATION (Qt)· tan, damp, medium dense to dense, silty, fine sand bottom of boring, no caving, no groundwater boring·backfilled 7/8/05 BORINGN0.2 SOIL DESCRIPTION TOPSOIL brown, dry, loose, silty, fine sand with rootlets COLLUVIUM (Qal) brown, damp, loose to medium dense sand with silt " " " " " TERRACE DEPOSITS FORMATION (Qt) . tan, damp, medium dense to dense, silty, fine sand bottom of boring, no caving, no groundwater boring backfilled 7/8/05 BORINGN0.·3 SOIL DESCRIPTION TOPSOIL brown, dry, loose, silty, fine sand with rootlets COLLUVIUM (Qal) brown, damp, loose to medium dense sand with silt TERRACE DEPOSITS FORMATION (Qt) · tan, damp, medium dense to dense, silty, fine sand bottom of boring, no caving, ho groundwater boring backfilled 7 /8/05 y M 112.3 4.6 y M 105.6 3.3 y M 4.1 . ---------.-----------------------------------.--- 10 .-·. lYIAJOR DIV.ONS ·SYMBOL -1:scR:lPTION GW WELL GRADED GRAVELS OR GRA V~L-SAND . . MIXTURES. LITTLE 0R NO F.INES GRAVELS GP POORLY GRADED GRAVELS OR GRAVEL-SAND (MORETHAN½ . MIXTURES. LITTLE OR NO FINES OF COARSE FRACTION GM SIL TY GRAVELS, GRAVEL-SAND-SILT MIXTURES >N0.4SIEVE SIZE) COARSE GC CLAYEY GRAVELS, GRAVEL-SAND-CLAY MIXTURES GRAINED SOILS (MORE THAN ½ OF SOIL> . SW NO. 200 SIEVE SIZE) WELL GRADED SANDS OR GRAVELLY SANDS, LITTLE OR NO FINES SANDS SP POORLY GRADED SANDS OR GRA YELL Y SANDS, (MORETHAN½ OF COARSE LITTLE OR NO FINES FRACTION S:M SILT{ SANDS, SILT-SAi"lD MIXTURES <N0.4SIEVE SIZE) SC CLAYEY SANDS, SAND-CLAY MIXTURES ML INORGANIC SILTS Ai'IP VERY FINE SAi"lDS, ROCK SILTS & FLOUR, SIL TY OR CLAYEY FINE SANDS OR CLAYEY SiLTS WITH SLIGHTPLASTICITY CLAYS CL INORGAi"lIC CLAYS OF. LOW TO MEDIUM LIQUID LIMIT PLASTICITY, GRAVELLY CLAYS, SAi"lDY CLAYS, <50 SILTY CLAYS. LEAN CLAYS FINE GRAINED OL ORGAi"lIC SILTS Ai"lD ORGAi"lIC SILTY CLAYS OF SOILS LOW PLASTICITY (MORE THAI"-! ½ OF SOIL< l\'IlI NO. 200 SIEVE SIZE) iNORGAi"lIC'~ILTS, MICACEOUS OR DIATOMACEOUS SILTS & FINE SANDY OR SIL TY SOILS. ELASTIC SIL TS CLAYS CH INORGANIC CLAYS OF HIGH PLASTICITY, FAT LIQUID LIMIT >50 CLAYS OH I ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGAi"lIC SIL TY CLAYS. ORGAi"lIC SIL TS HIGHLY ORGAJ.'11:C SOILS Pt I PEAT A,"lD OTHER HIGH!. Y ORGAi"lIC SOILS CLASSIFICATION CHART (UNIFIED SOIL CLASSIFICATION SYSTEM) ' CLASSIFICATION RANGE OF GRAIN SIZES t;.S. STANDA,RD GRAIN SIZE IN .SIEVE SIZE MILLIMETERS BOULDERS I Above 12 Inches I Above305 COBBLES I .12 Inches To 3 Inches 305 To 76.2 GR,AVEL I 3 Inches to No. 4 I 76.2 to 4.76 Coarse 3 Inches to ¾ Inch 76.2 to 19.1 Fine l/4 Inch to No. 4 19.1 to 4.76 SAND No. 4 to No. 200 4.76 to 0.074 Coarse No. 4 to No. 10 4.76 to 2.00 Medium No. 10 to No. 40 2.00 to 0.420 Ftile No. 40 to No. 200 0.420 to 0.074 SILT AND CLAY I Below No. 200 ~ Below 0.074 GRAIN SIZE CHART EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. 10925 HARTLEY ROAD, SUITE "I" SANTEE, CALIFORNIA 920il U.S.C.S. SOIL CLASSIFICATION 70 10 I· ·1 .. I' I -e ~ ~ I I ,. s 44 I I = ~ 30 la! ·I I ;; £ :0 r I ~H.t'H 10 UQUIO UJrial r (t.:..~. ": PLASTICITY CHART RHODES PROJECT NO. 05~1106G6 PLATE NO. 3 JUL:Y 20, 2005 -RH0DESPROJ$CTNO. 05-11061 PAGEL-1 LABORATORY TEST RESULTS MAXIMUM DRY DENSITY AND OPTIMUM MOISTURE CONTENT (ASTM D1557) The maximum dry densities and optimum moisture contents of the fill materials as determined by ASTM Dl557-91, Procedures A and B which use 25 blows of a 10 pound slide hammer falling from a height of 18 inches on each of 5 equal layers in a 4 inch diameter 1/30 cubic foot compaction cylinder and Procedure C which uses 56 blows of a 10 pound slide hammer falling from a height of 18 inches on each of 5 equal layers in a 6 inch diameter 1/13.3 cubic foot compaction cylinder are presented as follows: OPTIMUM MAXIMUM MOISTURE SOILTYJ>E/ DRY DENSITY CONTENT PROCEDURE DESCRIPTION (PCF) (%) 1/A TAN SILTY FINE SAND 127.0 7.8 INITIAL MOISTURE CONTENT{%) 8.2 l" 1/2" 3/8" #4 #8 #16 #30 #40 #60 #100 #200 uses EXP ANSI ON iNDEX TEST (ASTM D4829) SATURATED MOISTURE CONTENT(%) 15.7 INITIAL DRY DENSITY EXPANSION (PCF) INDEX. 116.7 0 PARTICLE SIZE ANALYSIS (ASTM D422) 100 99 88 71 37 18 10 SP-SM 11 100 99 98 97 90 77 46 30 22 ·sM LOCATION B-1@ 1.5' LOCATION B-1@ 1.5' • RHODES PROJECT NO .. 05~1106,, REFERENCES 1. "1997 Unifonn Building Code, Volume 2, Structural Engineering Design Provisions", Published by International Conference of Building Officials. 2. "Maps of Known Active Fault Near-Source Zones in California and Adjacent Portions of Nevada", Published by International Conference of Building Officials. 3. "Geologic Maps of the Northwestern Part of San Diego County, California, Plate No. 1, Geologic Map of the Oceanside, San Luis Rey, and San Marcos 7.5' Quadrangles, San Diego County,. California", by Siang S. Tan and Michael P. Kennedy, 1996. 12 •• EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. 10925 HARTLEY ROAD, SUITE I SANTEE, CALIFORNIA 92071 (619) 258-7901 APPENDIX A RECOMMENDED EARTHWORK SPECIFICATIONS 1. General Description The intent of these specifications is to obtain uniformity and adequate strength in filled ground so that the proposed structures may be safely supported. The procedures include the clearing and . preparation of the land to be filled, processing the fill soils, the spreading, and compaction of the filled areas to conform with the lines and grades as shown on the approved plans. The owner shall retain a Civil Engineer qualified in sqil mechanics (herein referred to as engineer) to inspect and test earthwork in accordance with these specifications. The engineer shall advise the owner and grading contractor immediately if any unsatisfactory conditions are observed to exist and shall have the authority to reject the compacted filled ground until such time that corrective measures are taken, necessary to comply with the specifications. It shall be the sole responsibility of the grading contractor to achieve the specified degree of compaction. 2. Preparing Areas to be Filled (a) All brush, vegetation and any biodegradable refuse shall be removed or otherwise disposed of so as to leave the areas to be filled free of vegetation and debris. Any uncompacted filled ground or loose compressible natural ground shall be removed unless the report recommends otherwise. Any buried tanks or other structures shall be removed and the depression backfilled to the satisfaction of the engineer. (b) The natural ground which is determined to be satisfactory for the support of the filled ground shall then be plowed or scarified to a depth of at least 12 inches (12"). (c) · After the natural ground has been prepared, it shall then be brought to the proper moisture content and compacted to not less than 90 percent of maximum dry dep.sity in accordance with ASTM D1557-91. ( d) Where fills are made on slopes greater than 20 percent, horizontal benches shall be cut into the firm natural ground. The initial bench at the toe of the fill sha:11 be at least 15 feet in width on firm undisturbed natural ground. The width of all succeeding benches shall be at least 6 feet. ... APPENDIXA. • 2 3. Fill Materials All material shall be approved by the engineer and shall consist of materials free from vegetable matter, and other lumps greater than 6 inches in diameter. If, during grading operations, soils are found which were not encountered and tested in the preliminary investigation, tests on· these soils shall be performed to determine their physical characteristics. Any special treatment recommended in the preliminary or subsequent soils reports not covered herein shall become an addendum to these specifications. 4. Placing and Compacting Fill Materials ( a) When the moisture content of the fill material is below that specified, water shall be added until the moisture content is near optimum to assure unifon:p. mixing and effective compaction. _ (b) When the moisture content of the fill materials is above that specified, the fill material shall be aerated by blading and scarifying or other satisfactory methods until the moisture content is near optimum as speci~ed. (c) After processing, the suitable fill materials shall be placed in layers which, when compacted, shall not exceed six inches ( 6"). Each layer shall be spread evenly and shall be thoroughly mixed during the .spreading ·insure uniformity of materials and moisture in each layer. ( d) After each layer has been placed, mixed and spread evenly, it shall be thoroughly compacted to not less than the density set forth in paragraph 2 ( c) above. Compaction shall be -accomplished with approval types of compaction equipment. Rolling shall be accomplished while the fill material is at the specified moisture content. In place density tests shall be performed in accord~ce with A.STM D1556-90. ( e) The ~urfaces of the fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment. Compacting operations shall be continued until the slopes are stable and until the~e i.s no appreciable amount ofloose soil on the slopes. 5. Inspection Bufficient inspection by our firm or the Soil's Engineer of record and/or his/her representative shall be maintained during the filling and compacting operations so that he/she can verify that the fill was constructed in accordance with the accepted specifications. 6. Seasonal Limits No fill material shall be placed, spread, or rolled if weather conditions increase the moisture content above permissible limits. When the work i~ interrupted by rain, fill operations shall not be resumed until the moisture content and dens.ity of fill are as previously specified. All recommendations presented in the attached report are a part of these specifications. 2