SITE INFORMATION AND CORRESPONDENCE 1991-1992

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, l Mr. Val Siebal -3- ey 31, 1990 Thus, we propose that such testing be performed as part of the supplemental remedial investigation at this site. o Well Survey and Abandoned Wells PG&E has performed a survey of wells located within one mile of the site as part of the preliminary remedial investigation (see Figure 1- 4, Page 8, Volume 1) . We are obtaining all available information concerning the abandoned on-site well and will forward that to you when available. If the well is shown to be improperly abandoned, we will take the necessary steps to correct that situation. o Well Construction We concur that excessively long screens create the possibility of vertical migration of contaminants, loss of depth-discrete data, and dilution of water quality samples. Wells completed below the free water table will have screens limited to 10 feet in length. Mud rotary equipment will be used to drill any future wells below the water table; such wells will be constructed using centralizers above and below the screened section and no more than 40 feet apart on the blank casing sections. Sieve analysis of water-bearing strata will be used to design filter packs for wells screened within that strata. o Target Constituents and Analytical Methods We will propose a list of target constituents, and the rationale for their selection, in the workplan for supplemental remedial investigation studies. Dilutions of samples will be performed according to accepted laboratory practices, and will be used in assessing the concentrations of only extremely elevated constituents. o Tentative Schedule for Supplemental Remedial Investigation The tentative schedule for the initial steps of the supplemental investigations is as follows: Activity ate • Issue Request-for-Proposal For August 10, 1990 Supplemental Remedial Investigation • Receive Proposals By September 3, 1990