SITE INFORMATION AND CORRESPONDENCE_FILE 1

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California Pgional Water Quality Cont Board >"` ' Central Valley Region xe Karl E. Longley,SCD,P.E., Chair �"' Linda S.Adams Arnold Secretaryjor Sacramento Alain Office Arnold Environmental 11020 Sun Center Drive#200,Rancho Cordova,California 956706114 Governor Protection Phone(916)464-3291 •FAX(916)464-4645 http://ww,w.waterboards.ca.gov/centralvalley To: Mr. John Yanak FROM: Steven W. Meeks, P.E. California Manager of Manufacturing Water Resources Control Engineer J. R. Simplot Site Cleanup Section DATE: 1 August 2007 >` SIGNATURE: • `- EVALUATION MONITORING PROGRAM ADDENDUM— SOURCE AREA INVESTIGATION, POND DISCHARGE PUMP AREA AND PIPING INSPECTION REPORT AND SURFACE RELEASES, J. R. SIMPLOT, 16777 HOWLAND ROAD, LATHROP, SAN JOAQUIN COUNTY, CALIFORNIA Geomatrix on behalf of J.R. Simplot prepared the Evaluation Monitoring Program Addendum — Source Area Investigation (EMPA), which presents the findings of site assessment work performed around the three Class II surface impoundments at the J. R. Simplot, Lathrop facility. The three lined surface impoundments are referred to as the West Pond, the North Pond and the South Pond. The work around these ponds was part of the follow-up assessment work proposed in the Evaluation Monitoring Program — Interim Report (EMPIR) dated June 2006. The PDPA-PIR was prepared in-house by J.R. Simplot and presents the findings of a piping survey that was conducted around the lined surface impoundments at the Lathrop facility. Evaluation Monitoring Program Addendum — Source Area Investigation In response to the Regional Water Board staff's request to initiate a Corrective Action Plan (CAP) for known groundwater impacts in the vicinity of the three lined surface impoundments, J.R. Simplot, first, proposed an Evaluation Monitoring Program (EMP) to assess the nature and extent of the releases prior to completing the CAP. The surface impoundments are located on J.R. Simplot's Property on the east side of Howland Road and are currently regulated under Waste Discharge Requirements (WDRs) Order No. 97-229. Phase I and II work of the EMP was completed and reported by J.R. Simplot in the EMPIR dated 19 June 2006. The recently submitted EMPA contains results from the third phase (phase III) of soil and groundwater investigation work that was proposed in the EMPIR. This work consisted of advancing 16 soil borings around and downgradient (north-northwest) of the surface impoundments, mainly around the West Pond, in August 2006. In general, the findings presented in the EMPA indicate that soil and groundwater have been significantly impacted by inorganic chemicals (total dissolved solids, sulfate and ammonia as nitrogen) associated with the West pond. The data also indicates there may be smaller contributing source areas around the other surface impoundments (North and South Ponds). California Environmental Protection Agency Ca Recycled Paper