SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

✓ --0e C A M B R I A corresponding but lagging decrease in MTBE concentrations in wells MW-2 and MW-7 is anticipated as MTBE concentrations in the source area are depleted over time. Based on the information presented, continuous groundwater extraction is neither a cost-effective remedial alternative, nor is it warranted at this time. Additionally, implementation (design, permitting, and construction) of continuous groundwater extraction would take at least six months. A groundwater extraction event can be implemented within one month, and two or more groundwater extraction events can be conducted in the same six-month period. In the same regard, one or more groundwater extraction events could have been conducted in the four months © since Cambria submitted the Aquifer Pump Test Report, and Shell is eager to implement interim remediation as soon as possible. Cambria requests that SJCEHD reconsider our original recommendation to implement a temporary groundwater extraction program This program would initially consist of extracting groundwater from monitoring well MW-4 for one week, once per quarter. Cambria may adjust the extraction point, frequency and/or duration of extraction, or reconsider continuous groundwater extraction if the data warrants. This proposed additional testing would also provide the additional data necessary to design a permanent system, if one is deemed to be warranted. SJCEHD also stated in their March 2, 2003 letter that "Due to the high MTBE concentrations in the vadose zone, and the lack of a significant barrier against vertical migration of residual soil contamination to groundwater, EHD recommends that interim remediation in the vadose zone also be considered." Included within the work plan addendum, SJCEHD has requested a proposal for removing the residual MTBE mass in the soil. Cambria will evaluate existing site data and applicable remedial technologies to determine the feasibility and cost-effectiveness of each alternative for addressing residual soil contamination in the vadose zone. 8260 Peaks Report Cambria discussed the SJCEHD request to "conduct a full 8260B scan and report all peaks" at four of our sites(including the subject site) in our February 12, 2003 correspondence to Margaret Lagorio of SJCEHD. Here is an excerpt from that letter: "Cambria has discussed this request with Marty Hartzell (November 26, 2002) of the Central Valley Regional Water Quality Control Board (CVRWQCB). It is our understanding that the request to `report all peaks' originated from the CVRWQCB. In our conversation, Mr. Hartzell explained that he requests this at some sites he oversees when there are certain conditions at the site that warrant such analyses. Specifically, Mr. Hartzell requests these analyses at sites that 0955 3