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HomeMy WebLinkAboutSUP 06-11; Robertson Ranch Planning Area 12; Geotechnical Report; 2008-03-05Geotechnical • Coastal • Geologic • Environmental SUP 04,-if REPORT OF REMOVAL AND PLACEMENT OF PESTICIDE AFFECTED SOIL DURING ROUGH GRADING ROBERTSON RANCH WEST, PLANNING AREA 12 PROPOSED PARK SITE, CITY OF CARLSBAD SAN DIEGO COUNTY, CALIFORNIA 92010 APN 208-010-36, DEH FILE NO. H39700-001 FOR COUNTY OF SAN DIEGO DEPARTMENT OF ENVIRONMENTAL HEALTH LAND AND WATER QUALITY DIVISION SITE ASSESSMENT AND MITIGATION PROGRAM P.O. BOX 12961 SAN DIEGO, CALIFORNIA 92112-9261 W.O. E5247.1-SC MARCH 5, 2008 Geotechnical • Geologic • Coastal • Environmental 5741 Palmer Way • Carlsbad, California 92010 • (760)438-3155 • FAX (760) 931-0915 March 5, 2008 W.O. E5247.1-SC County of San Diego Department of Environmental Health Land and Water Quality Division Site Assessment and Mitigation Program P.O. BOX129261 San Diego, California 92112-9261 Attention: Mr. Danny Martinez Subject: Report of Removal and Placement of Pesticide Affected Soil During Rough Grading, Robertson Ranch West, Planning Area 12, Proposed Park Site, City of Carlsbad, San Diego County, California 92010, APN 208-010-36, DEHFileNo. H39700-001 Dear Mr. Martinez: As required by the County of San Diego, Department of Environmental Health (DEH), Voluntary Assistance Program (VAP), GeoSoils, Inc. (GSI) has prepared this summary report of field observations during the removal and placement of pesticide affected soil during rough grading at the subject site, per the approved DEH requirements for mitigation. The scope of our services has included a review of the referenced documents (see the Appendix), preparation of a health and safety plan, field observations during removal of pesticide affected soil and placement as compacted fill during rough grading, analysis of data, and preparation of this report. Background Summary Based upon our review of our update environmental site assessment (GSI, 2006b), the subject site appears to have been utilized for agriculture from at least 1928 until possibly 2005. The type of agriculture around the Robertson family ranch house included beans, squash, strawberries, etc. To evaluate the potential for restricted agricultural chemical residues, surficial soil samples were collected at depths of 0.5 foot, 1 foot, 2 feet, and 4 feet within the subject property. Sampling of earth materials within the subject property, consisted of a total of 28 soil samples collected from 12 random locations during this survey and our previous survey (GSI, 2006b), based upon soil type and agricultural activity. Soil samples collected were analyzed for Chlorinated Pesticides (EPA test method 8081 A). The California Code of Regulations (CCR), Title 22, Division 4.5, establishes a Total Threshold Limit Concentration (TTLC) for toxaphene residues at 5.0 mg/kg and for ODD DDE, and DDT at 1.0 mg/kg each. Concentrations for toxaphene and ODD, DDE, and DDT greater than the TTLC limits are designated as hazardous. There were no concentrations reported for toxaphene, ODD, DDE, nor DDT that were at or above the TTLCs. GSI utilized existing regulatory data as a screening tool for the detected concentrations of toxaphene and ODD, DDE, and DDT. Preliminary Remedial Goals (PRGs), which combine existing USEPA and CALEPA toxicity values with generally accepted exposure factors to estimate concentrations in residential and industrial soil that do not represent a cancer risk to humans greater than one-in-one million, are 0.44 mg/kg (residential) and 1.6 mg/kg (industrial) for toxaphene. PRGs for ODD are 2.4 mg/kg for residential soil and 10.0 mg/kg for industrial soil; for DDE, 1.7 mg/kg for residential and 7.0 for industrial; and for DDT, 1.7 mg/kg for residential and 7.0 mg/kg for industrial. Reported concentrations were found to be less than the criteria established as a potential risk to human health (Smucker, 2002), with the exception of one sample from our previous survey (GSI, 2006b), which was reported with a concentration of 0.46 mg/kg of toxaphene, slightly higher than the PRG for toxaphene. This soil sample was collected on the proposed park site property. The toxaphene was encountered within the upper 1 foot of soil. Based upon proposed future development of the site as a park site, our pesticide survey reports for the site, a review of grading plans prepared by O'Day Consultants for Robertson Ranch, dated February 23, 2007, and discussions with Mr. Danny Martinez of the DEH, GSI (2007a) provided the following mitigation criteria for those soils with respect to future human contact, as well as potential impacts to surface water and groundwater: Removal of toxaphene affected soil with concentrations of toxaphene greater than the PRG for residential soil (>0.44 mg/kg) to depths of 1 foot below ground surface (bgs). Based upon these grading plans, GSI recommended placing the toxaphene affected soil located at Soil Sample S-1, plus an area of 40 feet x 40 feet x 1 foot deep surrounding S-1, on the proposed park site at an elevation of 48 feet Mean Sea Level (MSL), after the recommended 2-foot removal depth is performed, as recommended in GSI (2007b), in the approximate location provided on Plate 1 (following the report), and as indicated on Figure 1. • Placement of the toxaphene affected soil as compacted fill within the proposed park site at an approximate elevation of 48 MSL. This location will provide a compacted fill cap of approximately 6 feet over the affected soil. The affected soil will thus be located greater than 20 feet above groundwater (groundwater elevation is 27 feet MSL), and 8 feet above any potential flooding, more than 900 feet west of Calavera Creek, and more than 800 feet north of the proposed 100-year flood zone after completion of grading. County of San Diego W.O. E5271.1 -SC DEH Case #H39700-001, Carlsbad March 5, 2008 File:e:\wp9\env\e5200\e5347.1 .rfr Page 2 GeoSoils, Inc. x_pCD"o"o2.o'£.CDD[(D T3TJco(DO"O2-o"(Q(DO 9(D*-#•>(D3O(DQ.(DT3OCOTVCO OCOf^(DcoCOc Elevation (feet MSL)mDmo§ 5To Sp in I X m o-o oI ooO o rn0 s-1 2. 82. (Q J fa I O X In a letter dated June 13, 2007, the DEH indicated that they also concurred with the mitigation, and approved the criteria for mitigation of the toxaphene affected soil. Field Activities During Removals and Placement of Toxaphene Affected Soil Prior to the start of removal of toxaphene affected soil, GSI provided employees of the grading contractor (Astleford Construction) and GSI employees working on the project site, with a copy of a site specific Safety and Health Plan (SHP), outlining the health and safety procedures to be used while performing the environmental remediation services, including the potential chemical and safety hazards and potential routes of exposure for each chemical hazard. On February 9, 2008, GSI observed removals of toxaphene affected soil within Planning Area 12, proposed park site. Approximately 118 cubic yards of soil were removed utilizing an excavator, then placed in a scraper and hauled onsite to the approved location presented on Plate 1 and Figure 1. The soil was placed under the observation and testing (field density testing) of GSI. The soil was removed and placed as compacted fill according to GSI's approved mitigation criteria (GSI, 2007a). The approximate final location of the toxaphene affected soil is presented on Plate 1. The horizontal limits of the toxaphene affected soil are presented on Plate 1, and vertical limits of the toxaphene affected soil are presented on Figure 1. Surveyed location and elevations of the toxaphene affected soil were provided by O'Day Consultants. CONCLUSIONS It is GSI's opinion that the toxaphene soil has been mitigated to significantly reduce the potential for future human contact, as well as potential impacts to surface water and groundwater, based upon the following: • The pesticide affected soil is well below the TTLC levels for the pesticides with reported concentrations within Planning Area 12 of Robertson Ranch West. Approximately 118 cubic yards of soil with reported concentrations above the PRG level for residential soil (>0.44 mg/kg toxaphene) have been removed and placed as compacted fill (minimum 90 percent relative compaction) within Planning Area 12 of Robertson Ranch West. The soil was removed and placed as compacted fill according to GSI's approved mitigation criteria (GSI, 2007a). A 1 foot layer of affected soil was placed at an approximate elevation of 48 feet MSL, approximately 22 feet above groundwater, with approximately 8 feet of compacted fill as a cap. • Based on the adherence to approved DEH criteria, GSI anticipates that the DEH will issue approval, concurrence, and closure upon receipt and review of this report. County of San Diego W.O. E5271.1 -SC DEH Case #H39700-001, Carlsbad March 5, 2008 File:e:\wp9\env\e5200\e5347.1 .rfr Page 4 GeoSoils, Inc. LIMITATIONS GSI has performed the services for this project in accordance with the terms of a contract between GSI and Client and in accordance with current professional standards for investigations of this type. The conclusions presented in this report are based on the information collected during the study, the present understanding of the site conditions, and professional judgment. Please note, subsurface and hazardous waste/toxic substance conditions may vary from those provided in historical documents reviewed by GSI. The interpretations and recommendations of GSI are based solely on such information and/or information supplied by Client. Findings of this assessment based on data provided by others carries no warranty, expressed or implied, as a result of the usage of such data. It is possible that future assessments may reveal additional data or variations of the current data which may require the current conclusions and recommendations to be reevaluated. As a result, GSI makes no warranty, either express or implied, as to its findings, opinions, recommendations, specifications, or professional advice except that they were promulgated after being prepared in accordance with generally accepted standards of care and diligence normally practiced by recognized consulting firms performing services of a similar nature. The information in this report is relevant to the date of the site work and should not be relied on to represent conditions at any later date. Facts, conditions, and acceptable risk factors change with time, accordingly, this report should be viewed within this context. County of San Diego W.O. E5271.1-SC DEH Case #H39700-001, Carlsbad March 5, 2008 File:e:\wp9\env\e5200\e5347.1.rfr Page 5 GeoSoils, Inc. The opportunity to be of services is appreciated. If you should have any questions, please do not hesitate to contact the undersigned at (760) 438-3155. Respectfully submitted, GeoSoils, Inc. A Reviewed by: Donna Gooley Director of Environmental REA-1 6400, CEG 2336 ohn P. Franklin Engineering Geolog REA-1 1675, CEG 1340 DG/JPF/jh Attachments: Distribution: Appendix - References Plate 1 - Affected Soil Placement Map (1) Addressee, unbound (2) Seabourne Investments Corp., Attention: Mr. Ken Cablay County of San Diego DEH Case #H39700-001, Carlsbad File:e:\wp9\env\e5200\e5347.1 .rfr W.O. E5271.1-SC March 5, 2008 Page6 GeoSoils, Inc. APPENDIX REFERENCES APPENDIX REFERENCES GeoSoils, Inc., 2007a, Revised detailed agricultural chemical residue survey, APN 208-010-36, Planning Area 12-13.44 acres and Planning Area 13 - 6.92 acres, Robertson Ranch West, Carlsbad, San Diego County California 92010, voluntary assistance case H39700-001, revised date June 7. , 2007b, Preliminary geotechnical evaluation, Planning Area 12 (13.44 acres), and Planning Area 13 (6.92 acres), Robertson Ranch West, Carlsbad, San Diego County, California 92010, City of Carlsbad Planning Department Application No. SUP 06-12/HDP 06-04, W.O. 5247-A-SC, dated January 21. , 2006a, Revised work plan for detailed agricultural chemical residues in soil, APN 208-010-36, Planning Area 12-13.44 acres, and Planning Area 13 - 6.92 acres, Robertson Ranch West, Carlsbad, San Diego County, California 92010, Voluntary Assistance Case H39700-001, W.O. E5247.1-SC, dated December 27. , 2006b, Update Phase I environmental site assessment and limited agricultural residue survey, Planning Area 12 -13.44 acres, and Planning Area 13 - 6.92 acres, Robertson Ranch West, Carlsbad, San Diego County, California 92010, W.O. E5247-SC, dated August 15. , 2003, Report for removal and placement of pesticide affected soil during construction of a segment of College Boulevard, Robertson Ranch, parcel 1, City of Carlsbad, San Diego County, California 92008, APN 168-050-47, DEH File No. H02725, W.O. E4019-SC, dated November 5. , 2001, Phase 1 environmental site assessment, Robertson Ranch - Parcel 2, City of Carlsbad, San Diego County, California 92008, W.O. E3098-SC, revised date September 13. Smucker, Stanford J., United States Environmental Protection Agency (USEPA), 2002, Region IX, Region 9 Preliminary Remediation Goals (PRGs) Table, Update dated October 1. GeoSoils, Inc.