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Home My WebLink About; Thompson Property - 7066 Crystalline Drive; Final Report of Testing and Observation Services; 2007-04-16FINAL REPORT OF TESTING AND OBSERVATION SERVICES DURING SITE GRADING AND WALL CONSTRUCTION THOMPSON PROPERTY 7066 CRYSTALLINE DRIVE CARLSBAD, CALIFORNIA PREPARED FOR MRS. KAREN THOMPSON <=/o SEABOURNE DEVELOPMENT COMPANY CARLSBAD, CALIFORNIA APRIL 16, 2007 PROJECT NO. 06716-32-02 GEOCON INCORPORATED GEOTECHNICAL CONSULTANTS Project No. 06716-32-02 April 16, 2007 Mrs. Karen Thompson 7o Seaboume Development Company Post Office Box 4659 Carlsbad, Califomia 92018-4659 Attention: Mrs. Karen Thompson and Mr. Ken Cablay Subject: THOMPSON PROPERTY 7066 CRYSTALLINE DRIVE CARLSBAD, CALIFORNIA FINAL REPORT OF TESTING AND OBSERVATION SERVICES DURING SITE GRADING AND WALL CONSTRUCTION Dear Mrs. Thompson and Mr. Cablay: In accordance with your authorization, we have provided testing and observation services during grading of the subject site. We are also providing information relating to the construction of the mechanically stabilized earth (MSE) retaining wall on the site. The site is located at 7066 Crystalline Drive, Carlsbad, Califomia. The Standard Pacific Homes, Bay Collection development, surrounds the property to the north, south and west. An existing residential development is located to the east of the property. It is understood the grading is being performed to provide increased usable backyard area. The scope of our services included the following: Observing the grading operation, including the placement of compacted fill soil and removal and/or processing of loose topsoil, previously placed fill, colluvium and alluvium. Performing in-place density and moisture content tests in fill placed and compacted on the site. Observing and testing of the "Keystone" MSE retaining wall construction. Performing laboratory tests of the fill material, including maximum dry density and optimum moisture content, expansion index and water soluble sulfate content. Performing laboratory tests to verify the MSE retaining wall design parameters, including shear strength and gradation. Preparing the As-Graded Geologic Map. Preparing this final report of grading. 6960 Flanders Drive • San Diego, California 92121-2974 • Telephone (858) 558-6900 • Fax (858) 558-6159 GENERAL The grading contractor for the project was Astleford Construction Inc. The project grading plans were prepared by Buccola Engineering Inc., and are entitled Grading Plan for: 7066 Crystalline Drive, Thompson Residence, Carlsbad, California, print dated January 4, 2007. Recommendations for grading were provided in the Geotechnical Investigation, Thompson Property, Carlsbad, Califomia, prepared by Geocon Incorporated, dated January 28, 2001 (Project No. 06716-32-01). The "Keystone" MSB retaining wall plans were prepared by Red One Engineering, Inc., and are entitled Keystone Retaining Wall Plans For: 7066 Crystalline Drive, Lot 242, CT 98-14, Carlsbad, Califomia, print dated June 5, 2006. References to elevations and locations herein are based on surveyors' or grade-checkers' stakes in the field. Geocon Incorporated does not provide surveying services and; therefore, has no opinion regarding the accuracy of the as-graded elevations or surface geometry with respect to the approved grading plans or proper surface drainage. GRADING The grading for the site began with removing and exporting of brush and vegetation from the area to be graded. Compressible surficial deposits were then removed approximately I to 11 feet below existing grades to expose competent alluvium and/or formational materials. Following remedial grading excavations, the exposed ground surface was scarified, moisture conditioned, and compacted. Fill soils derived from on-site excavations were then placed and compacted in layers until the design elevations were attained. Fill Materials and Placement Procedures The on-site fill materials generally consisted of yellowish-brown to reddish-brown, silty and clayey, fine to medium sands. The imported fill materials generally consisted of yellowish-brown, olive- brown and reddish-brown, silty and clayey fine to medium sands. With respect to fill placement, the procedures performed during grading of the site conformed to the recommendations contained in the referenced project soils report. The compacted fill was placed in lifts no thicker than would allow for adequate bonding and compaction. The soil was moisture conditioned, as necessary, and mixed during placement. Field In-Place Density and Laboratory Testing During the grading operation, compaction procedures were observed and in-place density tests were performed to evaluate the relative compaction of the fill material. The in-place density tests were performed in general conformance with ASTM Test Method D 2922-05 (nuclear). Results of the field density tests and moisture content tests performed during rough grading have been summarized on Project No. 06716-32-02 - 2 - April 16, 2007 Table I and are presented on the As-Graded Geologic Map (Figure 1). The MSE wall backfill test locations are not shown on Figure 1. These test locations are identified by station number and elevation on Table II. In general, the in-place density test results indicate that the fill, at the locations tested has a relative compaction of at least 90 percent. Laboratory tests were performed on samples of materials used for fill to evaluate the optimum moisture content and maximum dry density (ASTM D 1557-02). The results of the laboratory tests are summarized in Table II. Laboratory tests were also performed to verify the design parameters used for the "Keystone" MSE retaining wall and consisted of shear strength (ASTM D 3080-04) and gradation (ASTM D 422-63). The test results are presented on Tables III through IV. Additionally, laboratory tests were performed on a sample exposed at finish grade to determine the expansion potential (ASTM D 4829-03) and the water-soluble sulfate content (Califomia Test Method No. 417). The results of these laboratory tests are summarized on Tables V through VI. Slopes The fill slope was constmcted at a design inclination of 2:1 (horizontahvertical) or flatter, with a maximum height of approximately 20 feet, measured from top of wall to finish surface. The fill slope was track-walked with a bulldozer during grading. A keyway was constmcted for the fill slope. All slopes should be planted, drained, and maintained to reduce erosion. Slope irrigation should be kept to a minimum to just support the vegetative cover. Surface drainage should not be allowed to flow over the top of the slope. Finish Grade Soil Conditions Observations and laboratory test results performed during the grading operations indicate that the prevailing soils within three feet of finish grade have an Bxpansion Index of less than 90 and are classified as having a "low" to "medium" expansion potential as defined by Uniform Building Code (UBC) 1997 Table 18-I-B. KEYSTONE MSE RETAINING WALLS We have provided observation and compaction testing services during constmction of the "Keystone" MSE retaining wall for the subject project. The scope of our services consisted of observing the placement of the reinforcing geogrid, location and tensioning. In addition, in-place density testing was performed on fill placed as backflll during wall constmction. Prior to placing fill, the base of the wall excavation was observed by a representative of Geocon Incorporated. Our observation indicated that the soil conditions exposed at the base of the excavation consisted of formational materials and/or dense compacted fill. These soil conditions are consistent ProjectNo. 06716-32-02 - 3 - April 16, 2007 with those described in the referenced geotechnical report. In addition, the bearing strata at the base of the excavations are considered acceptable for support of the retaining wall. Backfill was placed and compacted in layers to the design elevations for geogrid reinforcement shown on the referenced plans. The geogrid reinforcement consisted of Strata Grid SG200. In general, the geogrid was cut to the desired length shown on the plan and then installed by attaching over pins extending from the Keystone facing units. Slack was removed by pulling the grid tight and nailing the back of the grid to the ground. A wall drain consisting of 4-inch-diameter perforated PVC pipe surrounded by 3/4-inch gravel and wrapped with filter fabric was placed at the base of the wall. In addition, an approximately I-foot wide zone of '/4-inch gravel was placed behind the wall and the wall facing units were filled with gravel. The subdrain outlets through the base of the wall via a solid pipe into a rip-rap section in front of the wall. The wall drain was constmcted in substantial conformance with the referenced wall plans. In-place density testing on backfill soil was performed in substantial conformance with ASTM Test Procedures D 2922-05 (nuclear). The results of the in-place density tests are presented on the attached Table I. In general, the in-place density test results indicate that fill soil placed as backflll was compacted to at least 90 percent relative compaction at the locations tested. Laboratory testing was performed on representative samples of the material used for backfill to determine shear strength, gradation and compaction characteristics (maximum dry density and optimum moisture content). The tests were performed in substantial conformance with current ASTM test procedures. Results of the laboratory tests are presented on Tables II through IV. Material used in the reinforced zone of the Keystone wall met or exceeded the design parameters. SOIL AND GEOLOGIC CONDITIONS The soil and geologic conditions encountered during grading were found to be generally similar to those described in the project soils report referenced herein. Compacted fill soils were placed over competent fonnational or alluvial materials once the existing ground surface was scarified, moisture conditioned, and compacted. CONCLUSIONS AND RECOMMENDATIONS 1.0 General 1.1 Based on observations and test results, it is the opinion of Geocon Incorporated that the geotechnical engineering and engineering geologic aspects of the grading for the property is in compliance with the approved geotechnical report and the grading plans. Soil and ProjectNo. 06716-32-02 - 4 - April 16, 20O7 geologic conditions encountered during grading that differ fi'om those anticipated by the project soil report are not uncommon. Where such conditions required a significant modification to the recommendations of the project soil report, they have been described herein. 1.2 No soil or geologic conditions were observed during grading that would preclude the continued development of the property as planned. Based upon laboratory test resuhs and field observations, it is our opinion that the fill soils have generally been compacted to at least 90 percent relative compaction. 2.0 Corrosive Soils 2.1 Laboratory tests were performed on a finish-grade sample of the site materials to determine the percentage of water-soluble sulfate. Results from the laboratory water-soluble sulfate test are presented on Table VI and indicate that on-site soils present a "moderate" sulfate exposure to concrete stmctures as defined by UBC Table 19-A-4. The concrete requirements set forth by UBC Table 19-A-4 are summarized on Table VII. 2.2 Geocon Incorporated does not practice in the field of corrosion engineering. If corrosion-sensitive improvements are planned, it is recommended that further evaluation by a corrosion engineer be performed to incorporate the necessary precautions to avoid premature corrosion concrete or buried metal in direct contact with the soils. 3.0 Site Drainage 3.1 Establishing proper drainage is imperative to reduce the potential for differential soil movement, erosion, and subsurface seepage. Positive measures should be taken to properly finish-grade the building pads after stmctures and other improvements are in place so that water draining from the building pads and adjacent properties is directed to streets and away from foundations and tops of slopes. Experience has shown that even with these provisions, a shallow groundwater or subsurface condition can and may develop in areas where no such condition existed prior to site development. This is particularly tme where a substantial increase in surface water inflltration results from an increase in landscape irrigation. ProjectNo. 06716-32-02 - 5 - April 16, 2007 LIMITATIONS The conclusions and recommendations contained herein apply only to our work with respect to grading and represent conditions at the date of our final observafion of April 6, 2007. Any subsequent grading should be done in conjunction with our observation and testing services. As used herein, the term "observation" implies only that we observed the progress of the work with which we agreed to be involved. Our services did not include the evaluation or idenfification of the potential presence of hazardous or corrosive materials. Our conclusions and opinions as to whether the work essentially complies with the job specifications are based on our observafions, experience and test results. Subsurface conditions, and the accuracy of tests used to measure such condhions, can vary greatly at any time. We make no warranty, expressed or implied, except that our services were performed in accordance with engineering principles generally accepted at this fime and locafion. 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. The fmdings and recommendations of this report may be invalidated wholly or partially by changes outside our control. Therefore, this report is subject to review and should not be relied upon after a period of three years. Should you have any quesfions regarding this report, or if we may be of fiirther service, please contact the undersigned at your convenience. Very tmly yours, GEOCON INCORPORATED Trevor E. Myers RCE 63773 TEM:DBE:dmc (6) Addressee David B. Evans CEG I860 ProjectNo. 06716-32-02 -6-April 16, 2007 TABLE I SUMMARY OF FIELD DENSITY TEST RESULTS Elev. Plus Field Field Field Req'd. or 3/4" Dty Moist. Rel. Rel. Depth Curve Rock Dens. Cont. Comp. Comp. Test No. Date Location (ft) No. (%) (pcO (%) (%) (%) 1 03/04/07 SE End of Property in front of wall 239 1 0 111.5 11.2 90 90 SZ 2 03/04/07 E Side of Property 250 1 0 112.5 13.4 9t 90 SZ 3 03/04/07 E Side of Property 244 1 0 111.0 11.8 90 90 sz 4 03/12/07 SE Side of Property 241 I 0 113.4 10.9 92 90 sz 5 03/12/07 E Side of Property 243 1 0 112.6 11.4 91 90 sz 6 03/12/07 SE Side of Property 246 1 0 114.3 10.3 93 90 sz 7 03/12/07 SE Side of Property 248 1 0 111.4 12.0 90 90 sz 8 03/12/07 E Side of Property 249 1 0 107.8 7.3 87 90 sz 8A 03/12/07 E Side of Property 249 1 0 115.9 12.2 94 90 9 03/12/07 Southem Pad Area 252 1 0 113.8 11.9 92 90 10 03/12/07 Middle Pad Area 249 1 0 111.9 12.6 91 90 11 03/12/07 Middle Pad Area 255 1 0 112.1 12.1 91 90 sz 12 03/13/06 SE End of Property 250 1 0 113.5 11.3 92 90 sz 13 03/13/06 E End of Property 252 1 0 111.5 10.9 90 90 sz 14 03/13/06 S End of Property 254 1 0 111.1 11.7 90 90 15 03/13/06 West Pad Area 257 1 0 111.9 12.2 91 90 16 03/13/06 North Pad Area 255 1 0 112.6 11.9 91 90 17 03/20/07 Top of Slope; Middle of Property 252 1 0 113.4 12.0 92 90 sz 18 03/20/07 S End of Pfoperty 256 0 115.4 14.5 90 90 19 03/22/07 Top ofSlope;SW End of Property 259 5 0 116.2 14.1 91 90 20 03/22/07 NW Pad Area 260 5 0 117.0 14.3 91 90 21 03/23/07 SW Pad Area 262 5 0 118.3 15.3 92 90 22 03/23/07 Top ofSlope;NE End of Property 258 5 0 118.6 14.8 93 90 23 03/27/07 North Pad Area 263 5 0 118.0 17.1 92 90 24 03/27/07 North Pad Area 265 5 0 116.4 10.3 91 90 25 03/27/07 SW Pad Area 265 5 0 115.7 11.6 90 90 26 03/27/07 SW End ofProperty; Front of Wall 245 5 0 115.9 10.0 91 90 27 03/27/07 E End ofProperty; Front of Wall 247 5 0 116.6 10.2 91 90 sz 28 03/28/07 SE End ofProperty 253 4 0 116.4 12.1 90 90 sz 29 03/28/07 SE End ofProperty 253 4 0 116.0 11.6 90 90 sz 30 03/28/07 S End ofProperty 253 4 0 118.4 11.8 92 90 sz 31 03/29/07 E End ofProperty 255 4 0 113.7 11.3 88 90 sz 31 A 03/29/07 E End ofProperty 255 4 0 118.6 11.8 92 90 32 03/29/07 Middle Pad Area 257 6 0 117.7 12.0 91 90 sz 33 03/29/07 Middle of Property 257 5 0 115.4 10.6 90 90 sz 34 03/30/07 SE End OfProperty 259 5 0 116.9 10.9 91 90 sz 35 03/30/07 S End OfProperty 261 7 0 115.9 11.3 90 90 sz 36 03/30/07 E End ofProperty 291 7 0 118.3 13.1 92 90 sz 37 04/02/07 E End ofProperty 265 4 0 116.0 10.9 90 90 38 04/02/07 Top of Slope; Middle of Property 265 4 0 116.8 10.2 91 90 39 04/02/07 Top of Slope; NE Portion ofProperty 265 4 0 115.9 10.2 90 90 40 04/03/07 Middle Pad Area 267 4 0 118.2 12.2 92 90 41 04/03/07 Middle Pad Area 267 4 0 117.7 11.7 91 90 42 04/03/07 N Pad Area 267 4 0 117.2 12.0 91 90 43 04/05/07 SW Pad Area 270 4 0 116.1 10.9 90 90 Project No. 06716-32-02 April 16, 2007 TABLE I SUMMARY OF FIELD DENSITY TEST RESULTS Elev. Plus Field Field Field Req'd. or 3/4" Dry Moist. Rel. Rel. Depth Curve Rock Dens. Cont. Comp. Comp. Test No. Date Location (ft) No. (%) (pcO (%) (%) (%) 44 04/05/07 Middle Pad Area 270 4 0 119.6 10.6 93 90 45 04/05/07 N Pad Area 270 4 0 116.8 11.3 91 90 46 04/06/07 SW Pad Area 273 4 0 116.3 10.6 90 90 47 04/06/07 NW Pad Area 273 4 0 118.4 11.7 92 90 ST 48 04/06/07 SE Eng of Fill 264 4 0 116.0 11.3 90 90 ST 49 04/06/07 E Portion ofProperty 266 4 0 116.4 10.1 90 90 FG 50 04/06/07 Middle Pad Area 274 5 0 116.9 10.9 91 90 Project No. 06716-32-02 April 16, 2007 TABLE I SUMMARY OF FIELD DENSITY TEST RESULTS Elev. Plus Field Field Field Req'd. or 3/4" Dry Moist. Rel. Rel. Depth Curve Rock Dens. Cont. Comp. Comp. Test No. Date Location (ft) No. (%) (pcf) (%) (%) (%) WB 1 03/02/07 Wall 1 2+26 245 1 0 IH.4 12.3 90 90 WB 2 03/02/07 Wall 12+18 247 1 0 111.0 13.4 90 90 WB 3 03/02/07 Wall 1 2+36 247 1 0 113.2 11.9 92 90 WB 4 03/02/07 Wall 1 2+10 249 I 0 lll.l 11.3 90 90 WB 5 03/02/07 Wall 1 2+44 249 I 0 112.6 12,5 91 90 WB 6 03/22/07 Wall 1 2+04 249 1 0 111.9 12.0 91 90 WB 7 03/22/07 Wall I 2+41 249 4 0 116.1 10.9 90 90 WB 8 03/22/07 Wall 1 2+50 251 4 0 117.9 11.7 92 90 WB 9 03/22/07 Wall 1 2+01 251 4 0 115.9 Ul 90 90 WB 10 03/22/07 Wall 1 2+22 252 4 0 117.7 12.8 91 90 WB 11 03/22/07 Wall 1 2+59 252 4 0 118.2 13.2 92 90 WB 12 03/22/07 Wall I 1+85 254 4 0 118.7 12.2 92 90 WB 13 03/22/07 Wall I 2+64 254 4 0 116.8 12.5 91 90 WB 14 03/23/07 Wall 1 1+71 257 4 0 117.5 11.2 91 90 WB 15 03/23/07 Wall 1 2+78 257 4 0 118.6 10.7 92 90 WB 16 03/23/07 Wall 1 2+68 260 4 0 116.3 11.0 90 90 WB 17 03/23/07 Wall 1 2+96 260 4 0 115.9 10.5 90 90 WB 18 03/23/07 Wall 1 1+58 262 4 0 113.6 11.7 88 90 WB ISA 03/23/07 Wall 1 1+58 262 4 0 117.0 11.3 91 90 WB 19 03/23/07 Wall 1 3+14 364 4 0 118.1 12.1 92 90 WB 20 03/26/07 Wall I 1+45 266 4 0 119.6 11.3 93 90 WB 21 03/26/07 Wall I 3+26 267 4 0 115.9 12.0 90 90 WB 22 03/26/07 Wall 1 1+28 269 4 0 116.3 12.6 90 90 WB 23 03/26/07 Wall 1 3+40 269 4 0 119.0 12.2 92 90 WB 24 03/26/07 Wall 1 3+07 263 4 0 116.8 11.5 91 90 WB 25' 03/26/07 Wall 1 3+22 270 4 0 117.2 11.0 91 90 WB 26 03/26/07 Wall 1 1+62 263 4 0 116.4 11.7 90 90 WB 27 03/26/07 Wall 1 1+36 268 4 0 117.9 11.2 92 90 WB 28 03/26/07 Wall 1 2+72 259 4 0 117.5 12.1 91 90 ProjectNo. 06716-32-02 April 16, 2007 TABLE I EXPLANATION OF CODED TERMS - TEST SUFFDC A, B, C,...: Retest of previous density test failure, following moisture conditioning and/or recompaction. - STRIKE-OUT Fill in area of density test failure was removed and replaced with properly compacted fill soil. - PREFIX CODE DESIGNATION FOR TEST NUMBERS FG - FINISH GRADE ST - SLOPE TEST SZ - SLOPE ZONE WB - WALL BACKFILL - CURVE NO. Corresponds to curve numbers listed in the summary of laboratory maximum dry density and optimum moisture content test results table for selected fill soil samples encountered during testing and observafion. - ROCK CORRECTION For density tests with rock percentage greater than zero, laboratory maximum dry density and optimum moisture content were adjusted for rock content. For tests with rock content equal to zero, laboratory maximum dry density and optimum moisture content values are unadjusted. - TYPE OF TEST SC: Sand Cone Test (ASTM Dl 556) NU: Nuclear Density Test (ASTM D2922) OT: Other - ELEVATION/DEPTH Test elevations/depths have been rounded to the nearest whole foot. ProjectNo. 06716-32-02 April 16,2007 TABLE II SUMMARY OF LABORATORY MAXIMUM DRY DENSITY AND OPTIMUM MOISTURE CONTENT TEST RESULTS ASTMD 1557-02 Proctor Curve No. Source and Descnption Maximum Dry Density (pcf) Optimum Moisture Content (%) 1 Silty, fine to medium SAND with Clay 123.4 10.4 2 Dark yellowish-brown, Silty, fine to medium SAND with Clay 126.8 9.9 3 Dark olive-brown. Clayey fine SAND with Silt 123.1 10.9 4 IMPORT #1: Reddish-brown, Clayey, fine to medium SAND 128.8 10.4 5 IMPORT #2: Dark yellowish-brown. Clayey, fine to medium SAND 128.0 10.1 6 IMPORT #3: Dark yellowish-brown. Clayey, fine to medium SAND with Sih 128.8 9.2 7 IMPORT #4: Light olive-brown. Clayey, fine to medium SAND 128.8 8.7 8 IMPORT #5: Yellowish-brown, Silty, fine to medium SAND with Clay 129.8 10.0 TABLE III SUMMARY OF DIRECT SHEAR TEST RESULTS ASTM D 3080-04 Sample Dry Density Moisture Content Unit Cohesion Angle of Shear No.* (pcf) (%) (psf) Resistance (degrees) 1 112.5 11.2 350 30 4 115.2 10.8 480 30 5 115.0 10.0 340 30 'Samples remolded to approximately 90 percent of the maximum dry density at near optimum moisture content. ProjectNo. 06716-32-02 April 16, 2007 TABLE IV SUMMARY OF LABORATORY GRADATION TEST RESULTS ASTM D 422-63 Sample No. Sieve Analysis ASTM D 422-63 (Sieve Size) Test Results (% passing) 1 No. 200 22 4 No. 200 26 5 No. 200 36 TABLE V SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS ASTM D 4829-03 Sample No. Moisture Content Dry Density (pel) Expansion Index Expansion Potential Sample No. Before Test (%) After Test (%) Dry Density (pel) Expansion Index Expansion Potential EI-1 12.4 23.9 104.5 58 Medium TABLE VI SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS CALIFORNIA TEST NO. 417 Sample No. Water-Soluble Sulfate (%) Sulfate Exposure El-1 0.152 Moderate TABLE Vll REQUIREMENTS FOR CONCRETE EXPOSED TO SULFATE-CONTAINING SOLUTIONS Sulfate Exposure Water-Soluble Sulfate Percent by Weight Cement Type Maximum Water-to-Cement Ratio by Weight Minimum Compressive Strength (psi) Negligible 0.00-0.10 — — Moderate 0.10-0.20 II 0.50 4,000 Severe 0.20 - 2.00 V 0.45 4,500 Very Severe >2.00 V 0.45 4,500 ProjectNo. 06716-32-02 April 16,2007