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• MEMORANDUM• <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD - CENTRAL VALLEY REGION <br /> 3443 Routier Road, Suite A Phone: (916) 361-5600 <br /> Sacramento, CA 95827-3098 ATSS Phone: 8-495-5600 <br /> TO: Antonia Vorster FROM: Richard McHenry <br /> Senior Engineer Area Engineer <br /> DATE: 8 March 1990 SIGNATURE: <br /> SUBJECT: LINCOLN VILLAGE PHASE II SAMPLING PLAN, STOCKTON SAN JOAQtIIN COONTY <br /> (CASE /3002) <br /> A revised Phase II work plan for site assessment at Lincoln Village Center dated <br /> 13 February 1990 was reviewed for conformance with our 21 December 1989 letter. My <br /> comments are as follows: <br /> 1. Monthly water level contour maps were not submitted. Ground water elevation data <br /> was submitted which appears to agree with a general ground water northeast <br /> direction of flow, however, contour maps should be developed. The placement and <br /> screening of the proposed monitoring wells should be supported by this data. <br /> 2. Laboratory data sheets and chain-of-custody forms should be submitted as an <br /> appendage to all reports. Water samples shall be analyzed for EPA 601 compounds. <br /> Page 6 of the work plan states that all samples will be analyzed for PCE only. <br /> 3. The rationale for placement and screening of the proposed monitoring wells, <br /> shallow and deep, were not submitted with the work plan. San Joaquin County has <br /> a standard requirement for a 50 foot sanitary seal on wells and a minimum distance <br /> requirements from sewer lines which could adversely effect proper site assessment. <br /> 4. The monitoring well installation technique appears adequate, 2 wells are hollow <br /> stem continuous core, 5 wells are hollow stem with split spoon sampling at 5 foot <br /> intervals. <br /> 5. Evaluation of LVMD Well Nos. 1 , 2 and 6 have not been fully addressed. Two deep <br /> (150 ft. ) wells are proposed to determine pollution levels in the deeper aquifer. <br /> It must be determined if the LVMD wells are a conduit for pollution to the deeper <br /> aquifer, also, these wells should be pumped to determine the relationship of the <br /> shallow and deeper aquifers. If the LVMD wells are the source of deeper aquifer <br /> pollution, either by inadequate well structure or pumping rates causing downward <br /> migration, remedial action must be taken. A schedule for regular monitoring of <br /> the LVMD wells for EPA 601 compounds should be developed unless it is shown that <br /> these wells are the cause of pollution within the deeper aquifer. <br /> FILE <br />