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HomeMy WebLinkAbout; Vispera Place Lot 136; Soils Report; 1983-11-02SAN MARCOS ENGINEERING Civil Engineers 380 Mlilberry Dr. Sure B SAN MARCOS. CALIFORNIA 92069 (619) 744-0111 November 2. 1983 Mr. Erza Jakubec 8606 Flanders Drive San. Diego, Ca. 92 126 Subject: Preliminary Soils Investigation Lot 136 Map 6800 Vispera Place, La Costa Dear Mr. Jakubec, As per your request we have performed a preliminary soils investigation of the site soils at the above subject address and the enclosed are our report and reco- mmendations. The existing soils at the said site is typically expansive silty clay with broken shale stone in the higher elevations. The shale is found to be trending to a more solid state as it gets deeper. No signs of unstable ground is found at site. We recommend the use of soil bearing footings for the foundation system, however, the recommendations shown in the attached report need to be observed in the design and construction of the proposed structure. If you have any question about this report and recommendations, please call. Very truly yours, SAN MARCOS ENGINEERING CWlL LNalHclll. SOI” * COUcID.~IOI) REPORT OF PRELIMINARY SOILS INVESTIGATION AND FOUNDATION RECOMMENDATIONS Project: Proposed Residence Structure Lot 136 Map 6800 Vispera Place, La Costa Carlsbad, California 1. General Information The site is located off .Vispera Place which is a cul-de-sac from Unicornio Way in La Costa Estates, Carlsbad. California. The lot is somewhat like a pie-shaped piece which has a trending slope of about 24 percent in a northeasterly direction downwards towards Vispera Place. According to the Plot Plan, the proposed structure will be located on a promontory along the slope where a cut and fill situation will be graded. Below is shown the general location of the site. ; h GMA~Rc;~s 28 ] %+--J-J---j SAN MARCOS ENGINEERING ClYlL LNa,NrT”s. SO,” a rOVND.IlON The lot is sorrounded by existing residential houses except on the northeasterly side which is vacant at this time. 2. Purpose of Soils Investigation The purpose of this preliminary soils investigation is to determine the physical characteristics of the existing site soils and to make foundations recommendations in connection with building a residential house at the site in accordance with the plot plan submitted. 3. The Soils Investigation The soils investigation consist of a field visual examination of on-site soils, rock outcrops if any, and a subsurface soils exploration. The subsurface explo- ration consisted of excavating four(4) test trenches dug by a backhoe at the loca- tions indicated in Plate 1 of this report. The depths of the trench excavations were in then order of 5 feet plus or minus. The soils encountered in the trenches were visually classified and logged accor- ding to the Unified Classification System as shown in Appendix E of this report. Soil samples were procured and brought to the laboratory for further classifica- tion analysis and maximum density tests and determination of moisture. content. The log of the soils encountered are shown in Plates 2 to 5, inclusive. 4. Findings and Comments Log of T-l which was taken at the lower elevation of the property show generally compact to very compact Silty Clay which is dry to moist. At about 4 feet below the existing ground surface, some black streaks of clay were observed. No water . -2- -^- ._... __--. -- ..- _ ~. _ SAN MARCOS ENGINEERING CWlL LNOINTSIIS. soou e COUltDAT1OI( was observed in the trench. Trench T-2 which was taken also at the lower eleva- tion but closer to the foot of the low promontory indicate about 3 feet of very com- pact, dry to moist light brown Silty Clay overlying very compact, light brown, dry to moist Silty Clay and degenerated Shalestone. No competent or solid bed- rock was observed in the trench excavated to about 5.5 feet below existing ground surface. No water was observed in the excavation. Trenches T-3 and T-4.were taken at the upper elevations. T-3 indicate very rocky which is cbmposed of broken, degenerate shalestone to about 3.5 feet. Below 3.5 feet the rock seem to be hard and not rippable. No water was observed in the trench. T-4 which was taken at a much higher elevation than T-3 indicate light brown, dry, very compact Silty Clay with traces of broken shale rock in the upper two feet layer of the stratification. This layer is underlain by Tan,dry to moist, very compact Clayey Silt, traces of broken rock. At about 3 feet below existing ground surface was observed a hard solid rock finger which extent could not be determined. It could be a part of a big boulder or bedrock. No water was observed in trench T-4. 5. Laboratory Test Results It is anticipated that the silty clay soils will be used for filling purposes. So a maximum density test was taken for use in the relative density compaction tests expected to be done during the grading operations. The result is shown in Plate 6 of this report. 6. Discussion and Recommendations a. A section drawn along the cent@ portion of the pad and running along the slope . -3- SAN MARCOS ENGINEERING Cl”,L LNOINI~“,. emu * CO”rnDAT1OII as shown in Plate 7 indicate that the foundation system will be about 4.5 feet below existing ground surface. It is recommended that the structure be founded on soil bearing footings. An allowable soil bearing pressure of 1500 psf be used in the determination of the width of footings. It is anticipated that the footings will be on shale rock in some areas and on silty clay soils in some areas. It is recommended that the silty clay material if encountered in the foundation area be removed to at least 24 inches below finish grade of pad and replaced with good granular material and.compacted to a minimum of 90 percent relative density. Footings should’bear on competent rock if rock is encountered in the foundation area. Al1 perimeter footings are recommended to be at least 18 inches in width, and the bottom of the footings to be at least 24 inches below finish grade. All perimeter footings should be continuously reinforced with 2-#4 bars placed 3,” above the bottom of the footing and 2-#4 bars placed 2 inches below top of footing. Isolated footings should have a minimum dimension of 24 inches both ways and reinforced with at least 4-#4 bars placed in both directions. b. The proposed retaining wall can be designed using the standard plans of the San Diego County Regional Standard Drawings since the wall is anticipated to be about 3 feet in height basing it from the section drawn as indicated in Plate 7. c. Basing it from the log of the soils encountered, it is recommended that the grading be limited to a maximum excavation of about 4.5 to 5 feet in depth other- wise blasting of rock may be necessary to attain the desired grade. d. It appears that the drainage swale along the easterly portion of the property -4- , ’ . SAN MARCOS ENGINEERING CWlL ENGIN‘SIS. eoks * IO”YDII1OW needs to be controlled positively considering that a considerable amount of sur- face runoff from the upper elevation is dumped into that area. This observation is based on the erosion caused by the runoff as observed. All surface runoff should be directed away from the foundation system. . . e. In the preparation of the ground for fill, a11 vegetation should be removed from the fill site. The specifications shown in Appendix A-Recommended Earth- work Specifications is part of our recommendations. f. If during the grading operations, soils other than the soils presented herein are encountered, this firm should be notified so that an evaluation could be made of the situation and appropriate recommendations be formulated. .- Prepared By: PLATE 1. plot plan & Grading PIa* , Location of Trench Test pits ~_--,-~~~+-i&i’l I.!, , *T- %- ‘a< ] i 1 II! i / 1 i ,t;----, I --- I I I --- - -, --- /h -- --- A’l-- ~- --- ,. ’ --- ------- J -- ---\ - -1 I I I i I’ I / I I h I/ h h 1.1 I . ‘\ -- -. ,A -- PLATE 2. Log of Soils SAN MARCOS ENGINEERING ClYlL CNOINCUS. *mu (L ~ouLIo.IIoII ,a0 MUL.~“I* DIII”~. wrrm . SAN UAIICO.. er .a-* Boring N0.Z.L Sheet N&I/of/ CONTRACT NO. twisl 6 Remarks PLATE 3. Log of soils SAN MARCOS ENGINEERING CIWL SNQIH~~“S. SO,” L ~OUc(D.TIOf4 3ao MUL.E”mv DIIYC SUIT. . sAr4 Y.“SO.. CA .a-* ce,o, 7.4~0181 Boring NO. Fa Sheet No.+,+- CONTRACT NO. PlJRPOSE Wtcwial .S Remarks . PLATE 4. Log of Soils SAN MARCOS ENGINEERING ClYlL EHO,IIr.~“S. se&s * CO”NDATIOr4 380 MUL.C”I* D”‘“l. SUIT.. **N YA”60.. c. *ao.* ldlSl74..01~, Boring No. FT Sheet No./Of- Material 6 Remarks I I I I I I n xzoffwn dL’7re*Lti Cd - . 2 I-- - PLATE 5. Log of soils SAN MARCOS ENGlNEERlNG CWlL LNOINIL”S. sea. L COUNDITIO” a*0 MUL.I”II*l D”WI. SUIT. . Boring No. F4 SAN Y**CO*, CA 920.. 16,9,74..01t, Sheet No./Otl/- /4y 4 / // c - . ?- 0-N n I/-- SAN MARCOS ENGINEERING CWlL LHOINln‘. ,e,Ls a ~OUNDATIO” PLATE 6. fAt;ieyrn Density vs. Moisture . . 120 ‘;; a ,.- 2 .t; $115 8 c !a Moisture Content, % Soil Type : Tan Silty Clay - . SANG MARCOS ENGINEERING CWlL LNOINSS”S. sol” L COVNoIrlOH PLATE 7. Section Taken Thru House Along Slope Horizontal Distance, Feet SAN MARCOS ENGINEERING CWlC CNOINIL".. S01" e COUNDITmCI APPENDIX A. REiCOMMENDED EARTHWRK SPECIFICATIONS : 1. General Description. The objective'is to obtain uniformity and adequate internal strength in'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 con- form 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 unsatis- factory conditions are observed to exist and shall have the authority to reject 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 (4 (b) (cl (d) All brush, vegetation and any biodegradable refuse shall be remov- ed, 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, soft, 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 is free ~from ruts, hunmocks, 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 than 90 percent of maximum density in accordance with.the A.S.T.M. 01557-70 method which uses 25 blows of a 10 pound ranuner falling 18 inches. oneach of 5 layers in a 4 inch diameter l/30 cubic foot cylin- drical meld. 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 . ,a0 r4VL.I”“” DIWI. ,“lTrn . .AN YIICOS. c. *IO.* t*ne, ,4..01,‘ .: ‘, . Page 2 '1-~ RECOMMENDED EARTHWORK SPECIFICATIONS~(CONT.) stabil'ity. 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 ground at the elevation of the toe stake placed at the natural angle of repose or design 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 matenals 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 recom- mended 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 inaccordance with the standards of the governmental agency having jurisdiction. j 4. Placing, Spreading, and Compacting Fill Materials. (a) b) (cl (d) When the moisture conient of the fill material'is below that specified by the Engineer, water shall be added inthe borrow pit until the moisture content is near optimum to assure uniform mixing and effectjve compaction. When the moisture content of the fill material is above that specified by the Engineer, resulting in inadequate compaction or unstable-fill,, the fill material shall be aerated by blading and scarifying or other satisfactory methods until the moisture content is near'optimum as specified. After processing, the suitable fill material shall be placeb.in layers which, when compacted, shall not exceed six inches (6"). Each layer shall be spread evenly and shall be thoroughly mixed durjng the spreading to insure uniformity of material and moisture in each layer. 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 sheeps- foot rollers, multiple-wheel pneumatir-tired rollers, or other approved types of compaction equipment, such as vibratory equipment that is specially designed for certain soil types. Rollers shall be , . 7’ Page 3 5.’ 6. 7. ,) ‘8 . ..-, (e) (f) (9) RECOlYMENDEO EARTHWORK SPECIFICATIONS (CONT.) 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 accomp- lished 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 tripsto 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 sheeps- foot 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. Compacting 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 ele- vation gain after compaction, but not to exceed two feet in vertical height between tests. Fleld 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 cover- age 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 of compaction. 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. +=%P Sufficient inspection by the Engineer shall be maintained during t e 1 lng and compacting operations so that he can verify that the fill was constructed in accordance with the accepted specifications. 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 ope.rations shall not be resumed until field tests by the soils engineer i,ndicate that the moisture content and density of fill are as previously specified. Limiting Values of Nonexpansive Soils. Those soils that expand 3.0 percent or less from air dry to saturation under a unit load of 150 pounds per square foot are considered to be nonexpansive. All recommendations presented in the attached report are a part of these .-. . specitlcations. SAN MARCOS ENGINEERING CiYlL ENGINEEIS. SOIL* a FO”ND.TION 580 MULBIRI” q IIVE. SYITK m s*N M*FICOs. c* *,ose cs,as 744.Ott1 i MAJOR DI”lE.lGNS I21 I APPENOIX . E NIFIED SOIL CLASSIFICATION’ I FIELD IDENTIPICATION PROCEDURES TYPICAL NAMES iExcluding parlicIt iarger than 3 inches and baring tractions 00 errimated v.eigtml I GW Wellgaded gw.nh, gravelund mixtur2s. Wida range in grain si*n and Iubltantial lit,,* or “0 tines. amo”ncI 0‘ .I, intcrmediars mnicle 1121. GP I Poorl”.Jradsd gravclr. gravrlund nlixtum, Predominantly on* size or 8 ranga of I~ZDI with ,im* or no fines. Mm* intermediate IiZcI mising. SW I Wellgrad*d rama. !pavelly ra”dS. little 0, Wide range in grain size and rubrtanrial amoums “0 fine,. of .I, inrermediare mrtic,e rim. SP I POOIlygraded un.3. grau*w Id”&, Imlc or Prcdaminanrb on* size or 3 range of sizes no tine% wirh fOr7m inrermediate .iz*, mirang. SM I- Silty randr. randsilt mixtures. NOnLdal*ic fine or finer With IOW piarwiry IfW idenriticarion proced”r?r see ML beburl. SC $ ML CL . Claw” randr. land-da” rniXl”,“. Plastic fines vor idenrificatio” procedura IH CL below,. IDENTIFICATION PROCEDURES on Ptaction Sm*ll” than NO. 40 Si.“, Sizr Dry Strength Oilatrncv Toughnea ICO”SiSta”CV !Reacrio” ,CrudGng near PL, to making, ChW~Cf~~iftiCS ,norganic silt, an* Yery tin* ra”dS. rock flour, Slltv or clayey on* unds 0, None (0 slight Quick IO IlOW None Cl8”W lilts Wkh IlighT planici~. Inorganic clay, a‘ IOW IO medium plaliicic”. gravelly CIWI, sand” Davy. Iilty claw. Medium to high None to “WY I,ow Medium lean Cl.“.. OL 1 organic fill, an* organic *i,ty clays 0‘ IOU Slight to plarricit”. medium SlDW Slight I I 1 I M” Inorganic lilts, rnicaCBO”I or distomyaceous Slight to SWl to fine sand” or liltv soils. e!arfiC 111m. medwm Slow IO none medium Pt Peat and char highly or!qanic rail% Readily ,denlified b” COIOI. c&Jr. ipangy fee, and freqYs”U” b” ‘ibro”s rexI”,*.