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�� SECOR www secor.coiTi <br /> INTERNATIONAL 3017 Kilgore Road.Suite 100 <br /> INCORPORATED Rancho Cordova,CA 95670 <br /> 916-861-0400 TEL <br /> 916-861-0430 FAX <br /> March 14, 2008 <br /> Mr. Roberto Cervantes <br /> California Regional Water Quality Control Board <br /> Central Valley Region <br /> 11020 Sun Center Drive, #200 <br /> Sacramento, CA 95670-6144 <br /> RE: Response to the California Regional Water Quality Control Board Letter Dated <br /> January 17, 2008 <br /> Parcel 2A <br /> 666 West Weber Avenue <br /> Stockton, California <br /> SECOR Project No.: 77TW.26397.44 <br /> Dear Mr. Cervantes: <br /> SECOR International Incorporated (SECOR), on behalf of ConocoPhillips Company and Chevron <br /> Environmental Management Company(collectively the"L&M Group"), submits this letter in response to the <br /> California Regional Water Quality Control Board (CRWQCB) letter dated January 17, 2008. SECOR has <br /> addressed the CRWQCB's comments (presented in italics), which are discussed below. <br /> Response to General Comments: <br /> • Figure 17(CID Zone Chemical Concentration Map)illustrates MW-54 and MW-55 as being the only <br /> wells monitoring these deeper groundwaterzones. The wells both show that the deeperzones are <br /> polluted with petroleum hydrocarbons (MW-54: TPHd=2.1 mg/L, TPHg=0.75 mg/L and MW-55: <br /> TPHd=1.6 mg/L, TPHg=0.76 mg/L). Hydrocarbon pollution in C and D zones require further <br /> characterization. A work plan for additional characterization of C and D zones is required to be <br /> submitted by 14 March 2008. <br /> While the source of the low level dissolved hydrocarbon concentrations reported in wells MW-54 and MW-55 <br /> is unknown, we agree that further investigation is appropriate. A work plan is included as Attachment A. <br /> • Figure 2 (Shallow A Zone Groundwater Contour Map) depicts a gradient of 0.005 ft/ft in the <br /> easterly direction. The isoconcentration maps(for example,see Attachment 1)show an undefined <br /> groundwater plume migrating in that direction. There are an insufficient number of wells along the <br /> east side of Parcel 2A and west sides of Parcels 3 and 4 to define the contamination plume. A <br /> work plan is required by 14 March 2008 to investigate these areas. <br /> We concur with the need for further assessment work east of the L&M Operable Unit(OU),which includes the <br /> Unocal OU. Historical data from the Unocal OU shows that petroleum impacts to soil and groundwater exist at <br /> that site. The City of Stockton Redevelopment Agency(RDA) is responsible for assessing and remediating <br />