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page 2, 205 N. Center St. Five monitoring wells, four vapor extraction wells and two recovery wells currently exist at the Weber Block site, which is the former location of a Shell service station. The shallowest of these wells are the vapor extraction wells (VEW), with screen intervals from 5 to 30-feet bsg. All four of these wells had MtBE above detectable levels at the July 26, 4999 monitoring event. MW-1, MW- 2 and MW-3 have screen intervals from 28-43 feet bsg. Each of these wells had MtBE above detectable levels at the same event. MW-4 is screened from 30-50 feet bsg, and MW-5 is screened from 29.5-49.5 bsg. MW-5 had 1,090 ppb MtBE at the same event. It is the opinion of PHSIEHD that soil borings GW-1 and GW-2 were too shallow to be used as indicators of the lateral extent of the subject sites contaminant plume. The Black &Veatch report expresses a similar opinion when it states "it is believed that the bottom of the two borings at locations GW-1 and GW-2 are at a slightly higher elevation than the monitoring wells at the Shell Station site. It appears likely that the probes were installed in a 'perched' zone of water that is a few feet above the zone of water being monitored by Shell". The work plan as submitted is not approved. Please prepare a work plan, as previously requested, to define the vertical and lateral extent of the petroleum hydrocarbon plume at this site and submit it to PHSIEHD by January 14, 2000. Detail in the work plan the methods that will be used to obtain discrete soil and groundwater samples for vertical definition. An on-site mobile lab is recommended for this next phase of work. Once the vertical extent of the contaminant plume is discretely defined in the source area, evaluation of the required minimum depth of the lateral investigation can be made. Groundwater contamination at this site is documented to 25-feet bsg. Historical low groundwater levels in the vicinity of the site are approximately 60-feet bsg. Therefore, discrete soil and groundwater samples must be collected to at least this depth. On . December 7, 1999 PHSIEHD discussed the work plan in a meeting with a representative from the Regional Water Quality Control Board, Central Valley Region (CVRWQCB). It was the recommendation of the Regional Board that a minimum of four soil borings would be necessary to further characterize the vertical and lateral extent of the contaminant plume. Lateral borings should be placed down-gradient and cross-gradient to on-site wells MW-4 and MW-3. In the PROPOSED SCOPE OF WORK section of the work plan, under subheading 'Permitting', reference is made to obtaining permits for well installation and for obtaining a City of Stockton encroachment permit for a well to be installed in Channel Ave. Please have your consultant explain what this refers to, as no well installations were proposed in the submitted work plan. In correspondence dated October 26, 1999 PHSIEHD requested that the signed tank tracking records and soil disposition receipts from the underground storage tank removal activities be forwarded to our office immediately. These items have yet to be received. Please send them. If you have any questions please call Lori Duncan at(209)468-0337. Donna Heran, RENS, Director Environmental Health Division CA P%VN Lori Duncan, Senior RENS Margaret Lagorio, REHS Site Mitigation Unit IV Supervisor, Unit IV cc: Marty Hartzell, CVRWQCB Rusty Benkosky, Secor Kitty Walker, City of Stockton Redevelopment Agency Bill Brown, Daley &. Heft