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Home My WebLink AboutCT 72-20; La Costa Vale Unit 3; Soils Report; 1984-08-10SAN MARCOS ENGINEERING CiWL C*‘C.*L..*, SOli, . COLmD.I.Oll - Preliminary Soils Investigation & Report for Lot 8 223-060-11 Lot 474 La Costa Vale Unit No. 3 Carlsbad Tract 72-20 - ,- - ENGINEERING DEPT. LIBRARY City of Carlsbad 2075 Las Palmas Drive Carl&a& CA 92009459 - a*9 MC..Es.. D”lVS s. -=. I... *.*cos CA ,lDO., IelP. 7.1-0111 .- SAN MARCOS ENGINEERING Civil Engineorr 380 Mulberry Or. Sute B SAN MARCOS. CALIFORNIA 92069 (619) 744.0111 - - - - - August 10, 1984 - Mr. Bill Miholich 5701 El Camino Real Carlsbad, California 92008 - Re: Lot 414 Carl&ad Tract 72-20 La Costa Vale Unit No. 3 Cadencia Street, Carl&ad, Ca. Dear Mr. Miholich, As per your request, we have performed a preliminary soils investi- gation at the above referenced site and this report is presented as regards our opinion of the site soils engineering factors that may affect your project. DeSCriDtiOn Of Site. - - - - The project site is located off Cadencia Street in the La Costa Vale Unit No. 3 development as shown in Carl&ad Tract 72-20. The Vicinity Map in the next page indicate the site of the project. The lot is on a slope trending in a direction from Venado Street westerly towards Cadencia Street. The sl,ope is mild to steep. The lot is full of weeds and other wild vegetation with some rock outcrops. Proposed Pro iect The project proposed is for the construction of a single-family resi- _- - - - - .- - - ,- - SAN MARCOS ENGINEERING ClYlL ENcz,N‘c”*. SOILS e COUND.TION Page 2 Miholich Soils Report, Cont'd..... dence structure which is a framed type construction with tile roof and stucco walls. No heavy loadings at site is anticipated. The site will be graded to have a house pad at the higher elevations with an approach driveway from Cadencia Street. The vicinity map is shown belaW. Figure 1. Vicinity Map - - --^ . . ----.. --~.~- -. - -~ - - - - SAN MARCOS ENGINEERING Page 3 Miholich Soils Report, Cont'd....... Puroose of Soils Investiqation The purpose of the soils investigation is to determine the following: 1. The condition and characteristics of the site soils, 2. Presence of expansive soils, 3. Feasible foundation system, and to make appropriate foundation recommendations. Soils Condition Our investigation consisted of observation of the site surface soils and the observation and testing of the test pit soils excavated by~a backhoe on August 1, 1984. The location of the test pits are shown on Plate 1 found at the back cover of this report inside 'the pocket. The test pits excavated were under the supervision of a soils engineer who made a visual classification of the soils encountered in accor- dance,with the Unified Soils Classification System as shown in Appen- dix E. The log of the soils encountered are shown Plates 2, 3 61 4. Bulk samples were also.taken and brought to the laboratory for lab classification and maximum density tests. The existing soils at site can be generally described as fairly uni- form and consisted of about 2 to 2.5 feet of dry, compact to very compact, Brown to Reddish brown Silty to Sandy Clay overlying dry to moist Yellowish Brown Sandy Clay and Shale Rock. The upper stratifi- - - SAN MARCOS ENGINEERING ClYlL LIIOINEL”,. &L, a CO”IID.IIO” Page 4 - Miholich Soils Report, Cont'd.... - - - cation is also with boulders and shale rock fragments. The shale rock found appear to be rippable in the depths shallower than 5 feet. At depths greater than 5 feet , the rock shale seems to be hard and difficult to excavate with the backhoe. This condition appear to be uniform in the area as per our experience with the adjoining lots' investigation. - - - - - - - The extent of the existing shale rock cannot be determined at this time without going into an extensive and detailed boring program. Based on our experience in the area, the soils are expansive. The samples encountered can be classified as expansive. Laboratorv Soils Testing A maximum dry density test was performed on the brqwn silty to sandy Clay material taken from a depth of about 2 feet below existing sur- face. The result indicate the soils to have a maximum dry density of 114 pcf at an optimum moisture content of 14 percent. This value can be used in the determination of relative density of compacting the site soils during the grading operations. 1. It is our opinion that the existing soils can safely support the proposed structure planned for the site provided the recommendations following are followed during the design and construction of the pro- SAN MARCOS ENGINEERING ClYlL LI(OIWSl”,. SOlI+ a POUIIO.TIOC( - Page 5 Miholich Soils Report, Cont'd..... posed project. - Z..The proposed structure can be founded with soil bearing footings with an allowable soil bearing pressure of 1800 psf. The bottom of the footing should be founded to at least 24 inches below the exis- ting ground surface or the adjacent finish grade. Perimeter wall footings should be at least 18 inches wide and continuously rein- forced with 2-#4 bars placed 3 inches above the bottom of the footing and 2-H bars placed 2 inches below the top of stem or floor level. Isolated footings should be at least 24 inches square and reinforced with 344 bars placed both ways. - 3. Slabs on grade should have a minimum thickness of 4 inches and reinforced with welded wire mesh placed at mid height of the slab. - The slab should be underlain by at least 4 inches of sand placed over a 6-mil vapor barrier which is underlain by at least an inch of sand placed over the prepared subgrade. 4. The subgrade should be wetted to about 3 percent above the opti- mum moist&e content of the subgrade soils prior to preparation of the foundation system. 5. The site soils should be prepared in accordance with the Earthwork Specifications shown in Appendix A of this report. 6. Footings placed in fill areas should be positioned such that the SAN MARCOS ENGINEERING ClllL m.0.WIK.S. ,011. . rO”*D.IIOI. Page 6 Miholich Soil,s Report, Cont'd..... - - - - - - - - - - .- - - - - edge of the footing is at lea.st 5 feet from the daylight measured horizontally from the slope face as shown below. Pad 7. It is possible that blasting may be necessary to achieve a graded pad for the proposed structure. 8. This firm should be contacted if soils different from what is presented in this report are found at site during the grading opera- tions. 9. A soils engineer should inspect the foundation trench soils prior to pouring of concrete for the foundation system to see to it that the recommendations presented herein are followed. 10. All surface water runoff should be directed away from the founaa- tion system positively. If you have any question about this report, please call. - - - - - - - - - - - - - SAN MARCOS ENGINEERING ClVlL LNmYsI”.. SOILS a ro”*o4~Doe4 Page 7 Miholich Soils Report, Cont'd........ Very truly yours, SAN WRCOS ENGINEERING By: Enclosures: .4s stated Distribution: (3) addressee SAN MARCOS ENGINEERING Civil Enginnm 380 Wbtrry Or. Sutt 9 SAN MARCOS. CPLiFORNIA 32069 (619) 7444111 - APPENDIX A RECOMMENDED EARTHWORK SPECIFICATIONS - 1. General Description. The objective is to obtain uniformity and adequate Internal strength III filled ground by proven engineering procedures and tests so that the proposed structures may be safely supported. The pro- cedures include the clearing and grubbing, removal of existing structures, preparation of land to be filled, processing the fill soils, filling of the land, and the spreading and compaction of the filled areas to conform with the lines, grades, and slopes as shown on the approved plans. The owner shall retain a Civil Engineer qualified in Soil Mechanics (herein referred to as Engineer) to inspect and test the filled ground as placed to verify the uniformity of compaction of filled ground to the specified 90 percent of maximum dry density. The Engineer shall advise the owner and grading contractor immediately if any unsatisfac- tory conditions are observed to exist and shall have the authority to re- ject the compacted filled ground until such that as 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. Clearing. Grubbing, and Preparing Areas to be Filled. (a) (b) (c) - All brush, vegetation. and any biodegradable refuse shall be re- moved, piled, and burned or otherwise disposed of so as to leave the areas to be filled free of vegetation and debris, Any uncompact- ed filled ground or loose compressible natural ground, shall be removed unless the report recommends otherwise. Any unstable, swampy, or otherwise unsuitable areas shall be corrected by draining or removal, or both. 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 six inches (6”), and until the surface if free from ruts, hummocks, or other uneven features which would tend to prevent uniform compaction by the equipment to be used. After the natural ground has been prepared, it shall then be brought to the proper moisture content and compacted to not less then 90 percent of maximum density in accordance with the A. S. T. M. D1557-70 method which uses 25 blows of a 10 pound rammer falling 18 inches on each of 5 layers in a 4 inch diameter l/30 cubic Coot cylindrical mold. - - Page 2 RECOMMENDED EARTHWORK SPECIFICATIONS (CONT.) (d) Where fills are made on hillsides or exposed slope areas, with gradients greater than 10 percent, horizontal benches shall be cut into firm undisturbed natural ground in order to provide both lateral and vertical stability. This is to provide a horizontal base so that each layer is placed and compacted on a horizontal plane. The initial bench at the toe of the fill shall be at least 10 feet in width on firm undisturbed natural angle of repose or de- sign slope. The Engineer shall determine the width and frequency of all succeeding benches which will vary with the soil conditions and the steepness of slope. 3. Materials and Special Requirements. The fill soils shall consist of select materials free from vegetable matter, and other deleterious substances, and shall not contain rocks or lumps greater than 6 inches in diameter. This may be obtained from the excavation of banks, borrow pits or any other approved sources and by mixing soils from one or more sources. If excessive vegetation, rocks, or soils with inadequate strength or other unacceptable physical characteristics are encountered, these shall be disposed of in waste areas as shown on the plans or as directed by the Engineer. 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 soil reports not covered herein shall become an addendum to these specifications. The testing and specifications for the compaction of subgrade. subbase, and base materials for roads, streets. highways, or other public property or rights-of-way shall be in accordance with the standards of the governmental agency having jurisdiction. 4. Placing, Spreading, and Compacting Fill Materials. (a) (c) (d) When the moisture content of the fill material is below that spe- cified by the Engineer, water shall be added in the borrow pit until the moisture content is near optimum to assure uniform mix- ing and effective compaction. When the moisture content of the fill material is above that spe- cified by the Engineer, resulting in inadequate compaction or un- stable fill, the fill material shall be aerated by blading and scarifying or other satisfactory methods until the moisture con- tent is near optimum as specified. After processing, the suitable fill material shall be placed in layers which, when compacted, shall not exceed six inches (6”). Each layer shall be spread evenly and shall be throughly mixed during the spreading to insure uniformity of material and mois- ture in each layer. After each layer has been placed, mixed and spread evenly, it shall be throughly compacted to not less than the density set forth - Page 3 (e) (D - - - - RECOMMENDED EARTHWORK SPECIFICATIONS (CONT.) in paragraph 2 (c) above. Compaction shall be accomplished with sheepsfoot rollers, multiple-wheel pneumatic-tired rollers, or other approved types of compaction equipment, such as vib- ratory equipment that is specially designed for certain soil types. Rollers shall be of such design and maintained to such a level that they will be able to compact the fill material to the specified density. Tamping feet of sheepsfoot rollers shall be maintained such that the soil will be compacted rather than sheared by the roller. Rolling shall be accomplished while the fill material is at the specified moisture content. Rolling of each layer shall be continuous over its entire area and the roller shall make sufficient trips to insure that the specified density has been obtained. Rolling shall be accomplished in a planned procedure such that the entire areas to be filled shall receive uniform compactive effort. The surfaces 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 there is no appreciable amount of loose soil on the slopes. Com- pacting of the slopes shall be accomplished by backrolling the slopes in increments of 3 to 5 feet in elevation gain or by other methods producing satisfactory results. Field density tests shall be taken for approximately each foot in elevation gain after compaction. but not to exceed two feet in vertical height between tests. Field density tests may be taken at intervals of 6 inches in elevation gain if required by the Engineer. The location of the tests in plan shall be so spaced to give the best possible coverage and shall be taken no farther apart than 100 feet. Tests shall be taken on corner and terrace lots for each two feet in elevation gain. The Engineer may take additional tests as considered necessary to check on the uniformity ofcompaction. Where sheepsfoot rollers are used, the tests shall be taken in the compacted material below the disturbed surface. No additional layers of fill shall be spread until the field density tests indicate that the specified density has been obtained. The fill operation shall be continued in six inch (6”) compacted layers as specified above, until the fill has been brought to the finished slopes and grades as shown on the accepted plans. 5* a--hi Ins ection. Sufficient inspection by the Engineer shall be maintained urmg t e filling and compacting operations so that he 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 is Interrupted by rain, fill operations shall not be resumed until field tests by the soils engineer indicate that the moisture content and density of fill are as previously specified. - .-. Page 4 RECOMMENDED EARTHWORK SPECIFICATIONS (CONT. ) 7. LimitingValties of Nonexpansive Soils, Those soils that expand 3.0 percent or less from air dry to saturafion under a unit load of 150 pounds per square foot are considered to be nonexpansive. a. All recommendations presented in the attached report are a part of these specifications. - - - - - - - - - - SAN MARCOS ENGlNEERlNa CWlL Cnow.‘L”,. S0,L. & ~O”r..o.l~O~ - - - - -- - - - Natural Ground Surface Stripping Depth: Remove All Topsoil Slope H Ratio= - Notes: 1. Width We should be at least 10’ . 2. The outside edge of bottom key shall be below topsoil or loose surface material. 3. Keys are required where the natural slope is steeper than 10 percent gradient or 10 horizontal to 1 vertical. TYPICAL KEY BENCHING FOR SLOPES No Scale - - - __^ . . ..____ --~.~- - SAN MARCOS ENGINEERING C,VlL LM(TlNe.l”,. SOILS . co”t4o.lio* 3ao UUL.I”“” D.Wl SL -. . 9-w “.“COS. 5. ,a-.. ,e,9, 7.1.0111 - -. - - - - - - - - - - ! Y .; ,; ; ; : : I : ‘ Y 5 5 ! 4 : i a ; MAJOR OIVISIONS APPENDIX. E UNIFIED SOIL CLASSIFII i TYPICAL N&Mea Ill I 121 131 I.1 , wwqadPd qIl.wl*. prar* ulld m~.Nr.. lilt,. ol “O K”“. 0ar.v pranlr. Jr,nl&dclav “.i.tum.. W.4l~rsd.d and,. grw.ll” “4,. !iltll Q no fin”. Pw,I” 9ad.d Ynd. gr,.dl” Y”d.. liltI. 0, no rinn. Sal,-, und,. wnd,ilt m~itur~,. C!WW ““da. undclw mnrtw”. . s 3; ML OL ri !E ‘Z : i =z I ” 3 I r : ,f ; 5 . h‘,r,a”ic 1dU md <WY ?i”. unb. *OS, hlr. ‘&It-i ae CII”P.# tin. ““b Q C1WW Sills *10! Ilighr Pi*,tici(*. morpm4c Cl.“, 9, !OW to ned0.m ~~IIIiCII”. srw.U~ CIPVS, wd” C’WI. wlr* cIav,. I..” CIW,. 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IOCNtTICICATION PROCEDUREJ an Crndon sm*IC ,keiT Na. .o Siam s;” or* Str*“g* oarmcl rou*nw Sl.ght to Slow :o “0”. r 51 gnt ,a mrd\um “.Mlum - *mgk :o ..q w- NO”, I *,* P.P. wd xkw h:$hl” qa”sc md.. , I ! RLad~l” dmh‘:ed b” CJIOI, z.,or, roc”qv !“I and “eq(.mtly by Mamu, 1,.1ui.. MlGHLI ORGANICSOlLf Pt -