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HomeMy WebLinkAboutCT 02-25; NORTH PARK AT LA COSTA; REPORT OF GEOTECHNICAL OBSERVATION AND TESTING; 2004-09-03(-) 'UI.. _-' Geotechnical • Coastal • Geologic Environmental 5741 Palmer Way • Carlsbad. California 92008 (760) 438-3155 FAX (760) 931-0915 September 3, 2004 W.O. 3975-F-SC Hallmark Communities 10675 Sorrento Valley Road San Diego, California 92130 Attention: Mr. Bruce Douthit Subject: Report of Geotechnical Observation and Testing, Retaining Walls, TraditiOns at La Costa, Carlsbad, San Diego County, California.. References: 1. "Final Compaction Report. of Grading, Traditions at La Costa, Lots 1 through 14, Carlsbad, San Diego County, California" W.O. 3975-6-SC, dated July 30, 2004, by GeoSoils, Inc. 2. "Preliñinary Geotechnical Investigation, Proposed Northpark at La Costa, Tentative Map CT 02-25, Carlsbad, San Diego County, California," W.O. 3975-A-SC, dated August 5, 2003, by GeoSofis, Inc. Dear Mr. Douthit: In accordance with your request and authorization, this report presents a summary of the observation, as well as the soil engineering and inspection and testing services, provided by GeoSoils, Inc. (GSI) of the subject retaining walls at Traditions at La Costa, in Carlsbad, San Diego County, California. GEOTECHNICAL OBSERVATION AND COMPACTION TESTING SUMMARY Observation services provided by GSI included footing (foundation zone subgrade) observations, and/or backdrain pipe placement, and/or backfill observation and testing for the subject retaining walls Observation and testing services were provided on a part-time basis by GSI personnel, as determined solely by Hallmark Communities. Select backfill (gravel), capped with onsite soils, were utilized as backfill materials for the retaining walls. Compaction was achieved by mechanical means utilizing hand tampers and other various compactive equipment. The minimum compaction recommended for the capped portion of the retaining walls Was 90 percent of the laboratory maximum dry density. Based on our observations and testing, wall construction appears to be in general accordance with GSI recommendations (see the References). The geologic conditions exposed during the retaining wall construction were periodically observed by a representative from our firm, when requested by the Client. The geologic conditions encountered generally were generally as anticipated and presented in our referenced reports (seethe References). GROUNDWATER Subsurface water was not encountered during construction. Groundwater is not expected to affect the development provided that the recommendations contained in this, and the referenced reports, are incorporated into final design and construction. However, perched groundwater conditions at the contact between compacted fill and the underlying bedrock may develop in the future as a result of excess irrigation, poor surface drainage, damaged utilities, and the permeability contrasts of bedrock and compacted fill This condition should be anticipated and disclosed to all interested parties. Should perched water conditions develop; this office could assess the affected area(s) and provide the appropriate recommendations to mitigate the observed groundwater conditions. GEOTECHNICAL ENGINEERING Preparation of Existing Ground Deleterious materials, such as concentrated organic matter. and miscellaneous debris, were stripped from the surface and disposed of offsite, prior to placing any fill. Fill Placement 1 Fill materials, consisting of onsite soils, were placed in 4- to 8-inch lifts, watered, mixed to achieve at least optimum moisture conditions, and compacted using compaction equipment 2 The approximate maximum thickness of fill at the subject site, placed under purview of this report, is approximately up to ± 4 feet in height and up to ±3 feet horizontally behind the walls. 3. All fills placed within the retaining walls, up to ±4fëet in height and up t0±3 feet horizontally behind the wall were observed and selectively tested by a field representative from this firm, as determined by the Client Hallmark Communities W.0. 3975 -F -SC Traditions. at La Costa Carisbad September 3 2004 File:e:\wp9\3900\3975f.rog Page 2 GeoSoils, Inc. SIL 1?(PE 'DESt"RIPTk kiUE1 PçF)' PT iURE ., •,• mCONyENT(%) B . Light Brown, SANDY.CLAY 116.0 . • 14.0 C . Brown, SILTY SAND • • • 130.0 . 9.0 • • r 4 Field Testing t. I Field density tests were ,'performed using nuclear densometer ASTM Teat, Methods D-2922 and D-3017 and sand cone ASTM Test Method D-.1 556. The test results are presented in the attached Table 1 Field density tests were taken atperiodic intervalsánd random, locations to check; the corn pactive effort proiided by the contractor. Field density testing was performed t0a maximum of 4 feet in height and 3 feet horizontally behind the retaining walls Where test results indicated a less than the required minimum compaction or less than optimum moisture, the contractor was notified and the area Was reworked until the required minimum relative compaction was achieved for the -: area. Based upon the operations observed, the test results presented herein are considered representative of the compacted fill 3 Visual classification of the soils in the field was the basis for determining which maximum density value to use for a given density test Retaining Walls .4 . GSI performed the following services during the construction of the retaining walls Hf • 1 Periodic observation of the retaining wall foundation excavation 2 Periodic observation of the retaining wall backdrain 3 Periodic observation and compaction testing on retaining wall backfill material Based on our observations, the retaining walls appearto have been constructed in general accordance with our recommendations • LABORATORY TESTING : •, The laboratory maximum drydensity and optimum moisture content for the major soil type , utilized was determined according to test method ASTMD-1557 and/or County test. methods The following table presents the results LIMITATIONS Observed site conditions may vary due to seasonal changes or other factors not obvious at the time of site grading or the construction of the retaining walls. Inasmuch as this letter is based upon our observations, and/ compaction test data obtained, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty is expressed or implied Standards of practice are subject to change with time GSI assumes no responsibility or liability for work or testing performed by others, or their inaction, or work performed when GSI is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent by the user to all the limitations outlined above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities The opportunity to be of. service is sincerely appreciated. If you should have any , questions, please do not hesitate to contact our office. Respectfully submitted, GeoSoils, Inc. Pr ject Geologist FR4,1 U 47057 NO. 1340 Engineering John P14 Civil David W. Skelly cE47(Lb' BEV/J PF/D WS/j h/jk Enclosure: Table 1 - Field Density Test Results Distribution: (2) Addressee (2) Hallmark Construction Trailer, Attention: Mr. Jerry Welsh Hallmark Communities W.0. 3975 F SC Traditions at La Costa, Carlsbad September 3, 2004 Fi1e:é:\wp9\3900\3975f.rog • • Page 4 GeoSoils, Inc. Table 1 FIELD DENSITY TEST RESULTS TES1.. NO UI IfT TYPE DAEE No OR OEPTh (ft' CONTENT (%) DENSITY (pcf) :::REL::: COMP (%) METHOD SC'iI TYPE - 1 RW 6/10/04 Lot Traditions 291.0 15.8 106.0 91.3 ND B 2 RW 6/10/04 Lot 5 Traditions 294.0 14.6 108.0 93.1 ND B. 3 RW 6/11/04 Lot 6 Traditions 294.0 16.2 105.3 90.7 SC B 4 RW 6/11/04 Lot Traditions 294.0 15.4 107.1 92.3 ND B 5 RW 6/14/04 Lot 14 Traditions 290.0 16.3 105.9 91.2 ND B 6 RW 6/14/04 Lot 14 Traditions 290.0 15.0 107.8 92.9 ND B 7 RW 6/16/04 NW @ Lot 1 Traditions 287.0 8.2 115.6 92.4 ND C 8 RW 6/16/04 NW @ Lot 1 Traditions 287.0 9.1 113.9 91.1 sc C 9 RW 6/17/04 SW@ Lot 12 Traditions 286.0 8.1 116.0 92.8 ND C 10 RW 6/17/04 SW Lot 12 Traditions 285.0 10.0 113.8 91.0 ND C 11 RW 6/18/04 W @ Lot 1 Traditions 290.0 16.4 104.9 90.4 ND B 12 RW 6/18/04 W@ Lot 1 Traditions 290.0 15.1 106.3 91.6 ND B 13 RW 6/21/04 SW @ Lot 12 Traditions 287.0 15.3 106.8 92.0 ND B 14 RW 6/21/04 SW @ Lot 12 Traditions 288.0 16.2 105.1 90.6 ND B 15 RW 6/22/04 SE @ Lot 12 Traditions 282.0 14.2 108.2 93.2 SC B 16 RW 6/22/04 SE @ Lot 11 Traditions 285.0 16.1 106.3 91.6 ND B 17 RW 6/22/04 SE @ Lot 10 Traditions 287.0 16.0 105.1 90.6 ND B 18 RW 6/28/04 SE @ Lot 12 Traditions 285.0 15.9 105.3 90.7 SC B 19 RW 6/28/04 SE @ Lot 11 Traditions 287.0 15.3 106.8 92.0 ND B 20 RW 7/2/04 SE @ Lot 12 Traditions 282.0 15.8 107.4 92.5 SC B 21 RW 7/2/04 SE @ Lot 10 Traditions 288.0 15.6 107.1 92.3 ND B 22 RW 7/6/04 SE @ Lot 11 Traditions 285.0 16.8 104.8 90.3 ND B 23 RW 7/6/04 SE @ Lot 10 Traditions 288.0 15.4 106.2 91.5 ND B 24 RW 7/16/04 NW @ LOT 7 Traditions 293.0 9.8 113.8 90.3 ND C 25 RW 7/20/04 Lot 10 Traditions 287.0 14.4 106.2 91.5 ND B 26 RW 7/20/04 Lot 11 Traditions 285.0 16.8 104.9 90.4 ND B 27 RW 7/20/04 Lot 12 Traditions 285.0 15.6 105.4 1 90.8 ND B LEGEND: ND = Nuclear Densometer NW = Northwest RW Retaining Wall SC = Sand Cone SE = Southeast SW = Southwest W = West Hallmark Communities . W.O. 3975-F-SC Traditions at La Costa, Carlsbad September 2004 Fi1e:e:\wp9\3900\3975f.rog - Page 1 GeoSotis, Inc.