SITE INFORMATION AND CORRESPONDENCE_1987-1992

Home Browse Search

MEMORANDUMO CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 361-5600 Sacramento, CA 95827-3098 ATSS Phone: 8-495-5600 TO: Antonia Vorster FROM: Richard McHenry Senior Engineer Area Engineer DATE: 18 May 1990 SIGNATURE: u ti SUBJECT: PHASE II SAMPLING WORK PLAN FOR LINCOLN VILLAGE CENTER, SAN JOAQUIN COUNTY Leedshill-Herkenhoff, Inc. has submitted revisions tc the Phase II work plan for Lincoln Village Center. The revisions dated 11 April 1990 are the third attempt at developing an acceptable work plan. Our comment letters dated 21 December 1989 and 27 March 1990 should be reviewed for specific detail . My comments on the revised work plan are as follows: 1. We required that monthly water level contour maps be included in the sampling plan. Leedshill-Herkenhoff (LH) submitted three quarterly maps and a map for March 1990. The maps which were submitted are of poor reproduction quality and barely legible. LH had previously submitted their raw water level data which they conclude is sufficient to show a consistent northeast direction of ground water flow. Ground water gradient maps are required to predict migration of the pollution plume and determine if local events, such as the pumping of nearby wells change the gradient. Sampling data must be included as an appendage to reports and acceptable methodology for interpretation of the data must be presented in the body of the report. 2. All water samples shall be analyzed for EPA 601 compounds not just PCE. PCE is currently the main focus of the ground water and soil investigation, however, this could change as PCE degrades to its breakdown products. LH has proposed that only downgradient wells be sampled for 601 compounds; this is an unacceptable alternative. All soil samples shall be analyzed for EPA 8010 compounds not just PCE. 3. LH has proposed the installation of eight new monitoring wells: A. Two deep wells to address vertical migration and define the deeper geology. The LVMD wells which show levels of PCE are screened deeper than the proposed monitoring wells. The two deep wells are not likely to define the vertical extent of pollution at the site but provide intermediate sampling and a better picture of deeper migration. Screens will have to be placed based on lithology encountered during drilling. B. Three shallow wells along Pacific Avenue established that the pollution has not left the property on its eastern border. At this stage of the investigation there is no evidence that the plume has extended to this point, however, Lincoln Village wishes to establish a perimeter monitoring network. There is evidence that pollution is off-site to the west of the site near MW-4 with no current plans for investigation. This is unacceptable.