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Home My WebLink AboutCT 79-21; UNICORNIO STREET CONDOMINIUM; REVIEW OF FINAL REPORT ON COMPACTED FILLED GROUND AND CLASSIFICATION OF SOIL CONDITIONS; 1979-08-16• GEDeON ENGINEERS AND GEOLOGISTS INCORPORATED File No. D-1953-JOI August 16, 1979 Mr. Randy Luce 4515 Spring Street La Mesa, California 9204J • CONSULTANTS IN THE APPLIJ;:O.EARTH SCIENCES Subject: Unicornio Street Condominiums Gentlemen: Lots 421 and 422, La Costa Meadows Unit No. 3 Unicornio Street . La Costa, California CONSUL T A TION In accordance with your request, we have reviewed t~e "Final Report on ,Compacted Filled Ground and Classification of Soil Conditions"(October 19, 1972) prepared by Benton Engineering, Incorporated for Lots 413 to 584 of La Costa Meadows Unit No.3, of which the two subject lots are a part .. The purpose of our review was to determine whether alternative pad preparation and foundation recommendations are possible. ' On August 9, 1979, our staff geologist performed a visual reconnaissance of the site. A disturbed bulk sample of the near-surface soils on which the proposed foundations will bear was taken from each of the subject lots. The maximum dry density and optimum moisture content cif each disturbed sample were determined in accordance with ASTM Test Method D1557- 70A. Portions of the samples were then remolded "into sample rings to 90 percent of m"aximum dry density at optimum moisture .content •. The re- molded into sample rings to 90 percent' of maximum dry density ~t optimum moisture content. The remolded samples 'were subjected to expansion tests. The results of our laboratory tests are presented on Tables I and U. The results of our laboratory tests indicate that the 'near-sur.face materials are .h~ghly expansive, as indicated in the referenced Benton Engineering repOrt. • 6645 CONVOY COURT • SAN DIEGO. CALIFORNIA 92111 • PHONE. (.714) .292-5100 I', I • I . !i r. I i I . I' I File No. 0-1953-JOI August 16, 1979 • The foundation excavations should be soaked with water Continuously for 48 hours prior to the pouring of concrete. The areas, to receive concrete foundations and slabs should be examined by a representative of our offiCe prior to the pouring of concrete to ascertain that the matet'i"al is two to four percent over optimum moisture content. Foundations for the proposed structures should be at least 12 inc;:hes wipe, and should extend at least 24 inches below lowest adjacent pad grade. We recommend minimum footing reinforcement to ,consist ,of four continuous No.4' steel reinforcing bars placed horizontally in all interior' and peripheral footings, two placed near the top of the footings and two placed near the bottom. Concrete slabs-on-grade, if used, should be at .least four inches thick and should be underlain by a visqueen moisture barrier and four inc,hes of crushed rock or clean sand. Slab reinforcement should consist of 6x6-6/6 welded wire mesh throughout. In addition, the slabs should ~e dowelled to the footings by means of No. 3 steel reinforcing bars placed at 18 inch centers extending 30 inches horizontally into the slab and vertically to the bottom of the footing. ' The lots should be fine-graded such that storm runoff and irrigation excesS flow away from structures and into controlled drainages.' Under no circum- stances should water be allowed to pond adjacent to footings. If you have any questions, or if we may be of any further service, please·. do not hesitate to contact our office. . Very truly yours, CO~J IN CORPORA TED It~d/~ es E. Likins E 17030 copies: (4) addressee GEOCON'" I H ,0 '0 I" p' 0 .• A T I: D I: -li Ii tIl ,Ii ·11 ii II H \ ',; '. I' i ~' J • I', " j ,r ~ ,.'1' .. . r ,,/' /' , File No. D-1953-JOl ,August 16, 1~79 Sample Number 1 . 2 . , . TABLE I Summary of Laboratory Compaction Test Results' A.S.t.M. 01557-70 Max. Dry Optimum Depth Density Mo'isture ft. Description pcf %di-ywt. 1 Light green Silty 114.8 15.9 CLAY 1 Yellow-brown, Silty '114.5 14.9 CLAY TABLE. II Summar! of Laboratory EXEansion Test Results, Moisture Content Expansion Before After or Test Test: Dry (+) S'amp1e Depth Density S~ttlement~-~ ,Surcharge No. Description ft. % % pcf % *1 Light green, 1 13.2(5.2) 25.1 105.8 +8.2 Silty CLAY *2 Yellow-brown; 1 11.7(4.3) 25.2 105.7 +8.6 Silty CLAY 2 Yellow-brown, 1 13.5 28.0 104.2 +9.3 Silty CLAY *Air-dry Swell; Air-dry moisture content in parenth~ses NOTE: Expansion tests were performed on samples remolded to approximately 90 percent of-ma~imum dry dens'ipy at optimum moisture content. . , Rsf 150 .150 150 GEOCON INCOllPO.Jl.-.TJ:D , 11 ! . I' ! , t; Ii j' l I; . , I' I !. \ -" " BENTON ENGINEERING. INC. A,.,.LIEO !JOIL MECHANICS ._-FOUND ... TlONS , 674' EL CAJO:<4 BOULEVARD tlAN OIE(oO. CA.LlFORNIA. 112115 f'HIlIP HENl(lfoIG eENTON r"£~U"&NT • (;'V'" 1. .. ",ltlr,AII.H OC,tober 19, 1972 La Costa Land Compcny., Costa Del Mar Road r.ancho La Costa, Califomj~ 92008 , . Subiect: Project No. 71-7-17D Grading Permit No. L-5930 Final Report on Compacted Filled Ground And Classification of Soil Conditions Lots 413 to 584, inclusive And Certain Street Areas La Costa lV\eadows Unit No.3 Carlsbad ... California ~ 1'1'7'\,.. AI c: ~, " ~=s ; .. 17'_.,. .... " ...., -~_ , .S,," Du;c;o 583·565,4 L.. ..,,,..... "15.,.65-'1 i ! I . ~ t , !I I I ;1 j, - I I I • I , Gentlemen: This is to report the results of tests and observations made in order to inspectfhe compaction of filled ground placed on certain areas of La Coste Meadows Unit No.3 :n Carlsbad, California, formerly a port of the County of San Diego. The fills were placed during the period between . July 15, 1971 and July 20, 1972. The approximate areas and dep~hs of filled ground placed under our inspecHon in accordance' with the approved specifications .are shown on the attached Drawing No.1, enti-tled II Location of Compacted Filled Ground.1I The grading plan used for' the placement of filled ground was prepared by Rick Engineering Company and approved March 15, 1971. ' The approximate locations at which the test's were token and the finol testresult3 are'presented on poges T -1 to T-26, inclusive, undar the "Table of Test Results. II The ,laboratory determina- tions of the maximum dry densities and optimum moisture content's of the moior fill ma'!eriels ara pres~nted on pOf:]8S T -27 and T -28, ',"der the" laboratory Telt Raslllt:." 'Sone ~f the maximum ury d;nsities shown in the IITcble of 'fest Results" were combinations of th~se. The tesl's were token during the weekly periods indicated below: Test Number· , .. 1 to 4, inclusive 5 to 21, inclusive 22 to 35, inclusive '36 to 6~, inclusive 64 to 113, inclusive 114 to ~tnclu;sive 154 tol ~ 1 ~,1 Iftcltmy, 219 to 275, 'nclustv", 276 to 318, inclusive 319 to 360, inclusiv8 . Week Ending July 17, 1971 July 24, 1971 August 7, 197} August 14, 1971 August 21, 1971 AU9ust 28, 1971 September 4, 1971 September 11, 1971 September 18, 1971 September 25, 1~71 I !' :i .' . ;; ., ~ :1 1 'J :\ 1 ' . :j , ~:-t. :t :.1 ", , A • i J 1 :·1 J :J :'1 i l " / . .". .'" ,. I .;,,:riOjtlct No. 71-7-170 -2-October 1.9, 1972 ,lila Costa Land Company e ' .. ' I I Tes~ Number 361 to 404, inclusive 405 to 456, inclusive 457 to 507, inclusive 508 to 538, inclusive 539 to 570, inclusive 571 to 621, inclusive 622 to 6t5; incJusive 676 to 701, inclusive 702 to 771, inclusive 772 to 835, inclusive e36 to 905, inclusive 906 to 924, inclusive 925 to 930, inclusive 9,31 to 935, inclusive Week Ending October 2, 1971 Oc-tober 9, 1971 October 16,. 1971 October 30, 1971 . November 6, 1971 November 13, 197.1 Novembet 20, 1971 .. NoveTl!ber 27, 1971 December 4, 1971 December 11, 1971 December '18, 1971 December 25, 1971 July 15, 1972 July 22, 1972 Th£> fif'ol rAsultz of tests and obs~rvations indicate that the compact~d filled ground hasbaen, ,..!ac:c:d or )1:; J.'-CI,',:.ar •. Of ';.£1 mC!1':rr • .Jrn dry densit!{ pr greater. It has been deh;mnined thClt the fill materials, compacted to 90 percent of the maximum dfY densIty, have cis~te bearing value" of 1930 pounds per square foot for ona foot wide continuous footings founded at a minimum depth and placed five feet or more insIde the top of compacted filled ground slopes.. If footings are placed closer to th~ exposed slopes than 5 feet inside the top of compact"d fiUed ground . slopes, these should be deepened one foot below a 1 1/2 horizontal to 1 vertical lineproiected outward an4 downward from a point 5 feet horizontally inside the top of compacted filled ground slopes. Tests indicate that the compacted filled ground is adeqvate to satisfactorily'; 5upport the proposed wood frome dwellings without detrimental 5et~tlements. Expansiva clay I sit ty clay, and sandy clay soils vlere placed in the upper three feet in 'certain compacted fill areas and also exist in the upper three fee~ below finished grada in certain cut arees. The final classifications of t.he soil condiMons existing on each lot are piesented as follows: TyPe A -Critically Expansive Soils lots ~;~ m7.;~S!'1~ .~/ to 441, inclu!;ive 446 10"450, inclusive- 452 to 454, inclusive 459 to' 466, inclu$ive. 470 to 487, inclusive 489 to 510, inclusive 512 to 527, inclusive 8f:NTON £NGIN,"UtlHO. INC. Lots' 5.11 ~o :534, indusive 536 to 540, inclusive 543 to 552, inclusive 554, 556, 557, 558 563, 564, 570, 574 575, 576 578 to 581, inclusiva 584 ], 1 ?j:' , , . . . -3- TyPe B -Marginally Expansive Soils Lots 4-31 ano' 436 442 to 445, inclusive 451, 455 to 458" inclusive ' 467 to 469 , inclusive 488,5n lots 528, 529, 530, 535 542, 555, 560, 565 566, 568, 569, 571 572 and 573 Type C -Nonexpansive Soils Lots 541, 553, 559, 561, 562 567, 577, .582 f and 583 It is recommenued that the following special design and precautions Pe token for the houses to be constructed on the above lots in CiUel' fO mini.';ji~t.: I,ll,; f'o:;.siblc damcging effad~ dua to ~i ffcrcntial movements of the potentially expansive soils: Type A Lots 1. Avoid the use of isolated interior piers. Use continuous inter,connectod reinforced fo~tinD5 throughout, and place these at a minimum depth of two feet below the lowest adjacent exterior fin.at sround surface. 2. Reinforce and interconnect continuously with. steel, bars all 'interior cin4 exterior footinss with one 115 bar at 3 inches above the bottom of the footings and one 15 bar placed 1 1/2 inches below the fop of th~ stems of the footings. 3. Exercise every effort to assure that the moisture content offhe soils.in the upper 18 inches below finished grode is 1 percent to 3 percent 9rea~er than optimum at the time of plocing fqundations, and slabs. 4. Roised wo?d~n' floof!; d,,'Jt span bdtween 'continuous footings ore best ,or use' concrete slabs with ot least 6x6 -10/10 welded wi,re' rejnforcem~nt and a minimum of 4 In'ches of crushed rock,3/4 to 1 inch in size beneath all 5. "', concrete slobs. A moisture barrier should be provided over the crushecl' rod~ and this should be covered with 2 inches of sand below conqret.eslabs .. ' Separate goroge slabs from perimeter footings -by a 1/2 inch thickne$S' of comtruction felt or equivalont, to allow independent movement of garage slabs relative to perimete,r footings. Assvre comp~ete .~parction by' extending' the felt over the full depth of the front thickened edge of the garage s'ab. Also, cut off the garage door stops at least 1/.2 inch abov. the slab. t j 1 . I I i , \ I ,; I, i' t . , I I' ! I t ! I , i , t I r r t I I i ii I'] .'{ IJ , ' 1--I 1.1 [ . J' j., POOR· QUALITY ORIGINAL S .-~f:, '--~ -¥ ••• __ .......... _ ..... " .... .. ) '" .t:~~1§IIi~_ ------.: • .:.::.:---.~ • ., ... --........ --... ~ ..... ~ .. 'f ••• _ ...... _, ., .... ~" W ...... , .. w-''' . ;~:r:' ~~t No. '71-7-170 :I Costa La.nd Company e -4- I' O.ctober 19, 1972 :t ~iI ~ 6. e. Provide positive drainage away from all perimeter footin,9S with a vert i cal fall of at least 6 inches in 0 horizontcd distance of 5 to 6 feet outside the house walls. Type BLots Those lots listed as Type B lots should follow all the above-listed recommendations with the two following· exceptions: \ ". . . . 1 • The continuous footings may be pIeced at a minimum depth of 18 : ' inches below the lowest· adla~nt exterior final ground surfac4t rather 2. than the two feet recommended for Type A lofs. - Single 14 bar placed os directed (above) neat tops and bottoms of all interior and exterior footings may be substituted for the IS bars recommended for Type A lob • P-9commendations 3 to 6, inclusive, ~ listed for the Type A lots, are olso applicable, to the Type B tnts. . Only nonexpansive soil conditions were observed in the upper three feet on ,the Typ~ Clots cnd therefore specially designed footings ond slobs wi,1I not be required onthe.se Jots. !:cspectfully submitted, BENTON ENGINEERING, INC. BYR?!~ R. c. Remer j . 1£'~ieWedbY .Cf4'.~~ . Philip H~ Civil Engineer . - , . - ..' Jistr: (4) Addressee (1) (1 ) (2) (2) . (2) Rancho La Costa, ' Inc. Attention: Mr.. Burton L. Kromer Rick Engineering Company San Diego County Building Inspection, Vista Office Department of County Engineer (1) Attention: Mr. H. M. Taylor (1) Attention: Mr. Joe SovelJa City of Carlsbad Department of Building Inspection aENTON ItNG,~."I/IING., INC. RCfVPHB/ew