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t Stantec Consulting Corporation 57 Lafayette Circle 2nd Floor Lafayette CA 64549 Tel:(925)299-9300 Fax:(925)299-9302 Stantec April 28, 2009 Project: 185701168. 200.0006 Robert Aragon Department of Toxic Substances Control 700 Heinz Avenue Berkeley, California 94710 Dear Mr. Aragon: Re: Response to DTSC Comments -Well Abandonment Work Plan Pacific Gas and Electric, Former Lodi Manufactured Gas Plant, Lodi, California On behalf of Pacific Gas and Electric Company (PG&E), Stantec Consulting Corporation (Stantec) is submitting this letter as a response to Jim Rohrer's March 23, 2009 letter reviewing the February 4, 2009 Well Abandonment Work Plan for the Former Lodi Manufactured Gas Plant located at 712 South Sacramento Street in Lodi, California (Site, Figure 1). PG&E is conducting an investigation at the site under Hazardous Substances Site Cleanup Agreement No. HSA-VCA 06/07 182 of the California Department of Toxic Substances Control (DTSC)Voluntary Cleanup Program. This response letter presents the DTSC comments and recommendations followed by PG&E's response in italics. MARCH 23, 2009 COMMENTS—Jim Rohrer SPECIFIC COMMENTS 1) Groundwater in the two former wells to be abandoned may be contaminated. It is also possible that if these wells are sufficiently deep that they acted as conduits for contamination to impact deeper groundwater zones. Recommendation: If groundwater is encountered in either of the two former water wells to be abandoned during the rotary drilling work, then collect groundwater sample(s)from the wells prior to abandoning the wells. If the wells are significantly deeper than first encountered groundwater, then consideration should be given to collecting groundwater samples from deeper depths. Packers could be utilized to help isolate deeper sampling depths during low-flow purging. Response: A water rotary rig is proposed for the cleaning out of the well casing so the presence of groundwater will not be easily ascertained during drilling operations. Based on the driller's experience with older wells, the option of using an air rotary rig in place of the water rotary rig it is not recommended. It is the driller's experience with abandoning older steel casing wells that the air rotary rig may put excessive pressure on the casing and it could blow out(destroy, break) the casing. PG&E conducted soil and groundwater sampling at the site in October 2008. The locations of the sample locations are shown on Figure 2. Depth to water encountered in the borings was greater than 60 feet(61 feet in GW-1 and 64 feet in GW-2), and groundwater analytical results showed minimal MGP impacts (groundwater analytical results are posted on Figure 2). This groundwater elevation data is consistent with