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1 <br /> California Regional Water Quality Control Board <br /> [ <br /> Central Valley Region +� <br /> Karl E. Longley.Scl), P.E..Chair <br /> Linda S.Adarns Arnold <br /> Sec rerurr for 11020 Sun Center Drive 4200,Rancho Cordova,California 9-;670-6114 Schwarzenegger <br /> EnravnCntal Phone(916)464-3291 FAX(916)464-4645 Govemor <br /> Prorecnon http.//www.waterboards.ca.gov/central%,IRIECE /;E <br /> DD <br /> 19 February 2009 FEB 2 0 2009 <br /> ENVIRONMENT yEALTH <br /> Mr. James Diel PERMIT/SERVICES <br /> Manager, Site Remediation <br /> Union Pacific Railroad Company <br /> 9451 Atkinson Street, Suite 100 <br /> Roseville, CA 95747-5528 <br /> PHASE II LNAPL INVESTIGATION WORK PLAN, UNION PACIFIC RAILROAD COMPANY, <br /> FORMER MAINTENANCE FACILITY, 720 EAST 6' STREET, TRACY, SAN JOAQUIN <br /> COUNTY <br /> The California Regional Water Quality Control Board, Central Valley Region (Regional Water <br /> Board) staff has received and reviewed the Phase II LNAPL Investigation Work Plan (Work <br /> Plan) dated 6 January 2009, prepared by ARCADIS U.S., Inc. (ARCADIS) on behalf of Union <br /> Pacific Railroad Company (UPRR). <br /> The Work Plan explains the rationale and methods proposed to investigate vertical and <br /> horizontal extent of light non-aqueous phase liquids (LNAPL) across the site. The proposed <br /> investigation also seeks to address data gaps that remain from the corrective actions <br /> associated with the former Toxic Pits Cleanup Act (TPCA) waste pond excavation in the <br /> 1990s. <br /> Further clarification on elements of the Work Plan were provided by ARCADIS via email on 29 <br /> January 2009. Specifically: <br /> 1 . The Work Plan refers to the "source area" but does not identify its location in text or <br /> figures. It is not clear from the context whether "source area" is used to refer to the <br /> former pond, the treatment beds, or the LNAPL. According to ARCADIS' Lisa Teague, in <br /> this Work Plan, "source area" refers to "areas of the site where petroleum-impacted soils <br /> occur that are or may be a potential contributor to groundwater impacts." Please prepare <br /> an Addendum to the Work Plan that includes a map of the inferred source area. <br /> 2. 1 requested that ARCADIS clarify the criteria to be used to determine which Hydropunch <br /> soil borings, if any, are to be converted to permanent monitoring wells. ARCADIS' Lisa <br /> Teague responded that data from the proposed borings will be used to evaluate whether <br /> additional wells are needed. In addition, "Criteria for installation of monitoring wells <br /> include, but are not limited to, the apparent thickness. permeability, and lateral continuity <br /> of the water-bearing unit, contaminant concentrations; and correlation with data from <br /> California Environmental Protection Agency <br />