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HomeMy WebLinkAboutCT 82-23; Mass Grading for CT 82-23; Final Testing; 1984-09-19.. .. - / !. I ' ', Wh %l-Z mzsw.w FINAL REPORT OF TESTING AND OBSERVATION SERVICES DURING MASS GRADING OPERATIONS FOR SDP 82-4 AND CT 82-23 CARLSBAD, CALIFORNIA I For MOM DEVELOPMENT CORPORATION Huntington Beach, California I BY GEOCON, INCORPORATED San Diego, California September, 1984 I INCORPORATED ENGINEERS AND GEOLOGISTS CONSULTANTS IN THE APPLIED EARTH SCIENCES File No. D-2904-502 September 19, 1984 Mola Development Corporation Huntington Beach, California 92648 808 Adams Avenue Attention: Mr. Chris Christie Subject: SDP 82-4 AND CT 82-23 CARLSBAD, CALIFORNIA FINAL REPORT OF TESTING AND OBSERVATION SERVICES DURING MASS GRADING OPERATIONS Gentlemen: In accordance with your request, we have provided testing and observation services during the mass grading of the subject projects. Our services were performed during the period of April September 26, 1983 through June 22, 1984. The scope of our services included the following: 0 Observing the grading operation. 0 Performing in-place density tests in the placed and compacted fill. 0 Performing laboratory tests on samples of the prevailing soil conditions used for fill. 0 Preparing an As-Graded Geologic Map. 0 Providing professional opinions as to the grading contrac- tor's general adherence to the geotechnical aspects of the plans and specifications. 0 Preparing this final report of grading. General The project plans were prepared by Sowards Engineering, Incorporated and are entitled "Grading Plans for S.D.P. 82-4 and C.T. 82-23" dated August 1, 1983 and "Improvement Plans for Private Driveways," dated May 24, 1984. n 9530 DOWDY DRIVE . SAN DIEGO. CALIFORNIA 92126 . PHONE (619) 695-2880 , ' -. I File No. D-2904-502 September 19, 1984 The project soils report is. entitled "Geotechnical Investigation for Tentative Planned Development, Map 82-23" prepared by Geocon, Incorporated dated May 25, 1983. An earlier "Report of Testing and Observation Services During Mass Grading Operations for Carlsbad Tract 82-23" has been previously prepared by our office and is dated May 21, 1984. References to elevations and locations herein were based on surveyor's or grade checker's stakes in the field and/or interpolation from the referenced Grading Plans. Grading Subsequent to our earlier report, grading operations contained in the central canyon area and in the eastern portion of the site. During the grading operation, compaction procedures were observed and in- compaction of the placed fill. Field observations and the results of the place density tests (ASTM D1556) were performed to evaluate the relative in-place density tests indicate that the fill has_generally been compacted_ to at least 90 percent relative com action T%e G&ts of the in-place density tests are summarized in Table I1 T e approximate locations of the for reference. in-place density tests have been recorded on a copy of the Grading Plans Laboratory tests were performed on samples of material used for fill to evaluate maximum dry density (ASRI Dl557-70, Method C), optimum moisture content, and expansion characteristics. The results of the laboratory tests are summarized in Tables I and 111. Slopes Both cut and fill slopes have inclinations of 2 to 1 (horizontal to vertical) with maximum heights on the order of 26 feet and 24 feet, respectively. The fill slopes were periodically backrolled with a sheeps- upon completion. All slopes should be planted, drained andmaintained to % foot compactor during construction and were track-walked with a bulldozer reduce erosion. Slope planting should consist of a drought-tolerant ~67 mixture of native plants and trees having a variable root depth. Iceplant *,; should not be used on slopes. Slope watering should be kept to a minimum to just support the vegetative cover. " ". .. ". ~ p . i, " - . . - - .. . -2 - File No. D-2304-502 September 19, 1984 Finish Grade Soil Conditions During the grading operation, building pads which encountered clayey soils at grade were undercut at least 2.5 feet and capped with granular soils. were placed within at least the upper 3 feet of finish grade on fill lots. Similarly, our observations and test results indicate that granular soils The laboratory test results indicate that the prevailing soil conditions within 3 feet of finished grade on each building padhave an Expansion- Index of less than 20 and are classified as having a "very low" expansion summary of the indicated Expansion Index of the prevailing soil conditions potential as defined by UBC Standard Table 29-C. Table 111 presents a on the site. In addition to capping building pads as described above, the cut portion of those pads which contained a cut-fill transition within the building area was undercut at least 2.5 feet and replaced with compacted fill soil. Subdrains Subdrains were installed at the general locations shovn on the approved + Grading Plans. In addition, a blanket drain was installed in the seepage r-.- areas at the bottom of the canyon fill. The subdrains were "as-built" for a.3: location and elevation by the project Civil Engineer. C{HC - Soil and Geologic Conditions The soil and geologic conditions encountered during grading were found to be similar to those' described in the project geotechnical report. The geologic conditions observed. The approximate locations of subdrains and enclosed reductions of the approved Grading Plans depict the as-graded observed during the grading which, in our opinion, would preclude thF the blanket drain are also indicated. No soil or Reologic conditions were continued development of the property as planned. CONCLUSIONS AND RECOHNEMlATIONS Based upon laboratory test results and field observations, it is our L QLL :'x c.y 5" A,, opinion -that the prevailing soil conditions within 2.5 feet of finish pad grade consist . of "very low" expansive soils as classified by UBC Table 29C. We recommend the following foundation and slab design criteria for the proposed residential and commercial structures. -3- ' 0. I, - File No. D-2904-502 September 19, 1984 - Foundations 1. Conventional spread and/or continuous footings founded at least 12 inches beLoL12west adjacent grade in properly compacted or dense undisturbed "low" expansive soil may be designed for an allowable soil - - - - - - - -. - - bearing pressure of 2.000 psf (dead plus live loads). Footings should have a minimum width of 12 inches. This bearing pressure may be increased by up to one-third for transient loads such as wind or seismic forces. 2. All -s should be Ieinforced with at least two KO. 4 bottom. The above minimum reinforcement is based on soil characteristics reinforcing bars, one placed near the top of the footing and one near the and is not intended to be in lieu of reinforcement necessary for structural considerations. - - - 3. Concrete slahs-on-grade should have a nominal thickness of_4&&<5 and should be reinforced with 6x6-10/10 welded wire mesh. The slabs should be . underlain with 4 inches of clean sand and,moisture sensitive floor coverings are planned, a vlsqueen moisture barrier protected by a 2-inch sand cushion should be provided. Great care should be taken during the placement and curing of concrete flatwork to reduce the potential for shrinkage cracking. - - 4- Footings should not be placed within 8 feet of the top of slopes. Footings that must be located in this zone should be extended in depth such that the outer bottom edge of the footing is at least 8 feet horizontally from the face of the slope. 5. No special subgrade presaturation is deemed necessary prior to placing concrete, however, the exposed foundation and slab subnrade soils should be sprinkled as necessary to maintain a moist condition as would be expected in any such concrete placement. Lateral Loads 6. The pressure exerted by an equivalent fluid veight of 300 pcf should be used to provide resistance to design lateral loads. This design value - assumes that footings or shear ke;s are poured neat against properly compacted granilar fill soils or undisturbed formational soils and that the - Oil mass extends at least 5 feet..hJrizonfallx from the face of the footing whichever is greater. The upper 12 inches of material not protected by or three times the height of the surface generating passive pressure, resistance. floor slabs or pavement should not be included in design for passive 7- If friction is to be used to resist lateral loads, a coefficient of friction between soil and concrete of 0.40 may be utilized. -L - - , *. ,I. I ! .. . 1. !- * I, - File No. D-2904-502 September 19, 1984 Retaining Walls - 8. Unrestrained retaining walls should be designed to resist the pressure granular onsite material will be used for backfill, that the backfill exerted by an equivalent fluid weight of 30 pcf. This value assumes that wall. For walls with backfill surfaces inclined at no steeper than 2.0 to 1.0, an active pressure exerted by an equivalent fluid weight of 45 pcf should be used. 9. For walls restrained from movement at the top, such as basement walls, an additional uniform horizontal pressure of (7H) psf (H equals the height pressures given above. - surface will be level, and that no surcharge loads will be acting on the - - of the wall in feet) should be applied in addition to the active lateral c 10. All retainiq walls should be provided with a backfill drainage system adequate to prevent Lb,e-b.uildup of hydrostatic forces. Drainage 11. Adequate drainage provisions are imperative. Under no circumstances should water be allowed to pond adjacent to footings. The lots and improvements are in place so that drainage water is directed away from foundations, concrete slabs and slope tops to controlled drainage devices. - - building pads should be properly finish graded after buildings and other LIMITATIONS Any additional grading performed at the site should be done under our observation and testing. All trench backfill material in excess of 12 inches in depth should be compacted to at least 90 percent relative compac- tion. This office should be notified at least 48 hours prior to commencing additional grading or backfill testing. The conclusions and recommendations contained herein apply only to our work with respect to grading, and represent conditions at the date of our final inspection, June 22, 1984. Any subsequent grading should be done under our observation and testing. As used herein, the term "observation" implies only that we observed the progress of the work with which we agreed to be complies with the job specifications are based on our observations, involved. Our conclusions and opinions as to whether the work essentially experience and testing. Subsurface conditions, and the accuracy of tests used to measure such Conditions, can vary greatly at any time. IJe make no warranty, expressed or implied, except that our services were performed in accordance with engineering principles generally accepted at this time and location. -5 - File No. D-2904-302 September 19, 1984 We will accept no responsibility for any subsequent changes made to the site by others, by the uncontrolled action of water, or by the failure of others to properly repair damages caused by the uncontrolled action of water. further service, please contact the undersigned. If there are any questions regarding our recommendations or if we may be of Very truly yours, GEOCM, INCORPORATED ~~ Ja s E. Likins Michael W. Hart Rdd 17030 CEG 706 RRG: JEL: lm (5) addressee -6- &P4& Raul R. Garcia Staff Engineer GEOCON File No. D-2904-502 September 19, 1984 TABLE I Summary of Laboratory Compaction Test Results ASRI D1557-70 Sample No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Description Brown-tan, fine to medium slightly Clayey SAND Brown, Clayey, Silty, fine SAND Green-tan, Silty, Sandy. CLAY Brown. fine to medium, Silty Clayey SAND Tan, fine to medium, Silty SAND Brown, very fine to fine, Silty SAND Tan, very fine to fine, Silty SAND Reddish-brown, very fine to fine, Silty SAND White to gray, very fine to fine, Silty SAND Red-brown, very fine to fine SAND Tan, medium-grained, Clayey SAND Dark brown, fine SAND Light green, Silty Sandy CLAY Golden light brown, very fine to fine SAND Yellow to tan, fine to medium SAND Naximum Dry Density PC f 123.1 120.2 111.1 122.1 117.4 119.2 118.0 117.8 112.9 127.2 125.2 124.9 124.0 120.6 119.0 Optimum Eloisture % Dry Wt. 11.1 12.5 16.6 11.6 12.9 11.8 12.8 12.1 15.0 10.1 10.6 10.7 11.5 11.3 12.2 Y 3 Y) Y) W 3 e: Y Y) W h 0 m m odmrnma~ mmmmmod 0 0000000 l4 ddddddd . . . . . . , r. m 0 d m 0 4 U U rl U U d * r. 4 nm uu 44 0 l4 m W m m W Id m .c m u 0 l4 n n m u n: W u n: W W 4 0 .- z m .. P W -4 0 VI z d . W 0 Is V :- n: U VI U a W a rl u VI u W W n: Y r( E: 3 -. a% OE ErJ 40 c) !%N vu OmrlY)aumuOdrldl.hr-mN000 mwmmmmmmmmmmcommmmmmm rlwmw~amw~~m~mumu~m~m rlhm~rnmOmm~0mam~m~0~0 rl drlrldrldrl-Irl4 drlrlrld .................... .................... auaum~m-~)r"h~)-~~mmrna drlrldrlrlrldrlrlddddrlrl4rlrl-I 0000d40~0000000rl~000 vov WUW m d Pd N n W N omoz W. d or( LoaLou d Mrl U d ad w Lo -44 W nw PO -m - Z<Ird U N 0 z u m W Y W a U 0 z u u m W d W m W %d m .. dN dd -Id m . U . -8. :: .. . I 1 '. :, ._. .. UUNNNNNNNNUUU mndmdN4OmmNdd mmmmmmmmmmmmm Ud4UU-fU ~oomw-in mmmmmmm 4 + L1 cr V 4 W d ... . a . h . m H H \ N 4 N 4 , .c. ' I C r( 0 u m V 0 4 E r 0 x C v m .a G&ON B I GEOCON ax EO ~ENOmrlrlmdN-40Q.iNrlNnnNNrl 40 01 e *\* wmmmmmmmmmmmmmmmmmmmm mmm~rnm~~rn~rlonrlrnorlnurl . . . . . . . . ~rn~rnrlnd~mmnm~rl~~~oo~ rlorlorlrlrlrloorlodrl-4-4drlrlrl rldd-4rl.i-4rldrlrlrldrlrldrlrlrld ............ C 0 A C 4 V 'e 0 __L 4 Y cl 0 h -0 m 2 .d c Y c 0 U v H H W cl 3 cx En U OE~~.~NO~NNN~O~~ON~N~NO 40 a .v m ~mmmmmmmmmmmmmmmmmmmm d Y ro U cl 0 .. u ro z > U GEOCON _.. M. - 4 aaaaaaaaaaaaaaaaaaaa NmNONNdOmdOdOOOddOOU mmmmmmmmmmmmmmmmmmmm a c- a u3 ul UY UY ulu U * U ul a U U -Y U ul a ul N . Ln .-I yr . d N N . h -4 m m i m m m mm m m a 0 .. aa 0 a U U U a \ 4 N . N . CI -. 1,. ,':I h U W C 3 .r( C 0 U u v H H W cl h 2 a I U '..) uw m m a W 00 m W m ww m m W 03 W d 4 'u d 0 C C x U m 0 x c .- e V m J$ ,.: . -. . .- ... i I C r P P r U . - U 4NrlNdUNN4N.+dmNmdNOON mmmmmmmmmmmmmmmmmmmm ~amuommau-aamnmu~o~u OOUNW~NN~ .................... 47irlrlrlrl4.+"* nNzoNN--mN- ""* " oono mhwm ON -I444 "++? 00 mu ++ na AH U N &OCON . ! ... umm+.+ 4.4 NN~N.+ hmmmm C 4 0 u m 0 3" 4 4 Ir C 0 x u C m 4 C 2" u In v) TI d 0 a . 0 . U n n. * u. ir u" 21 I .. .. '1 .. . . .. d . . N m VI . VI m .u . m GEOCON N~m-t+~-~wr.~mmamm--~cn mmmmmmmmmmmmmmmcnmmmm ~rn~~rnmom~mo~-ahom~ocn ~~~~~mo~oomr"omoam- .................... ""4 44" 4" ""S .. GEDCON oommoomm-~~o~mmm~~m ~VQQO~O~\D~QY)~~-~O\DNN- .......... " 4.4 "4 . . . . . . . . . . . . 4 44 zm ~mm~~o~~)\~~~ornv)oummh~- -N-v)OU~-Y)OuhOuOONNnnO """""""""0" ..................... ~"""-""""-,~"- C $4 W 4 N 1 N Y) \ N. v) n 1 N v)' 0 N \ Y) GEOCON 3 J 3 -3 4 U 4 U 4 v) 4 U 4 U d J 3 -3 4 J d e 4 v) 4 v) 4 v) 4 v) 4 v) GEOCON ~auulhun~ulam~nnua~\~-rn- mmmmmmmmmmmmmmmmmmmmm 0 a N D4 m aPa 0 &&!ad mar0 '0 0 0 000 x 0 > -l W 5 n W ua m 0 C a u W C u 5 3 v) 0 File NO. D-2904-302 September 19, 1984 TABLE I11 Summary of Expansion Index Test Results Unit Nos. 1, 2, 3 7, a, 9, 10 Commercial Site Expansion Index 14 7 14 GEOCON ICON . .. . .. . _- ,' I i gl.: J.f. ti li I I I 1 ,I ; ,- t . .. ., .- . ., i ., . .. - .. -. ,. . .. .. .. . .. .. I. .c ,- i ,' /. ., J. I i .' I ' .'..A' i i. .. . ..