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ti ENVIRO�ENTAL HEALTIfl)EPARTMENT SAN JOAQUIN COUNTY Unit Supervisors Donna K. Heran, R.E.H.S.Director 304 East Weber Avenue,Third Floor Carl Borgman,R.E.H.S. Al Olsen, R.E.H.S. Stockton,California 95202-2708 Mike Huggins,R.E.H.S.,R.D.I. Program Manager Telephone: (209)468-3420 Douglas W.Wilson,R.E.H.S. fiaR Laurie A. Cotulla, R.E.H.S. Margaret Lagorio,R.E.H.S. Fax: (209)464-0138 Robert McClellan, R.E.H.S. Program Manager Website: ww.s.jgov.org/ehd/ Jeff Carruesco,R.E.H.S. PETER LENZ NOV 0 8 2005 6465 PACIFIC AVE STOCKTON CA 95207 RE: Howard Lenz Property SITE CODE: 2182 1648 Shaw Road Stockton CA 95215 San Joaquin County Environmental Health Department (SJC/EHD) has reviewed Additional Monitoring Well Installation Work Plan (Work Plan)dated October 20, 2005 submitted on your behalf by Advanced GeoEnviron mental, Inc. (AGE) and has the following comments. The Work Plan proposes the installation of four shallow groundwater monitoring wells with. screen intervals set between 55 and 70 feet below surface grade (bsg). Due to declining groundwater elevations the current shallow monitoring wells near the former tank pit area,. MW-1 thru MW-3, which have screen intervals extending to 55 feet bsg, have been sampled at most four times each in the past four years. Concentrations of petroleum hydrocarbon constituents remain high in these wells. Peripheral wells MW-4 thru MW-7 were built with screen intervals extending to 60 feet bsg. These four wells have each been sampled between 6 and 10 times in the past four years; results from all have been non-detect or very low for constituents analyzed. The intent of the SJC/EHD directives of February, July, September and October 2005 was for you to install additional shallow groundwater monitoring wells to reestablish the network of wells, in response to' a lower groundwater elevation, that will provide consistently available data on the status of the plume. The wells could also be utilized to help determine if feasibility testing of groundwater remediation strategies should be considered. This is increasingly important as the site is preparing to initiate interim soil remediation. In contrast to the SJC/EHD concerns, AGE has considered the lateral extent of shallow groundwater plume at this site to be generally defined. This conclusion has been stated by AGE in every quarterly groundwater monitoring report submitted, except one, since the first quarter of 2001 when lateral wells MW-4 thru MW-7 were installed. in response to the SJC/EHD directives, AGE has proposed the four new wells, but did not provide technical justifications for the locations they proposed for the wells. SJC/EHD infers that one lateral well could be justified in the predominant downgradient direction, currently proposed to be located approximately 25 feet north of MW-3j to close a potential data gap between wells MW-6 and MW-7. The proposed location for a well in the former tank pit area, near MW-1 is approved, as is the proposed location up gradient to MW-1 to monitor groundwater in the source area and up gradient from the source. AS SJC/EHD cannot infer a technical justification for the proposed well location approximately 40 feet northeast of and cross gradient to MW-1, SJC/EHD does not approve the well location at this time.