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California Regional Water Quality Control Board >s <br /> Central-Valley Region <br /> Steven T.Butler,Chair <br /> Winston H. Hickox Gray Davis <br /> Secreragfor Sacramento Main Office Governor <br /> Environmental Internet Address: http://Nvanv.sivrcb.ca.gov/--rwgcb5 <br /> Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 <br /> Phone(916)255-3000•FAX(916)255-3015 <br /> 28 April 2000 <br /> Mr. James Mills <br /> Westrec Marinas <br /> 14900 West Highway 12 <br /> Lodi, California 95242 <br /> FOURTH QUARTER 1999 GROUNDWATER MONITORING REPORT AND 1999 ANNUAL. <br /> REVIEW, TOWER PARK MARINA, SAN JOAQUIN COUNTY <br /> I have reviewed the 28 January 2000 Fourth Quarter 1999 Groundwater Monitoring Report and 1999 <br /> Annual Review (report) submitted by SECOR International Inc. on behalf of Westrec Marinas for the <br /> Tower Park Marina, 14900 West Highway 12, Lodi. I have the following comments on this report: <br /> 1. SECOR recommended preparation of a Tier II Risk-Based Corrective Action (RBCA) Human Health <br /> Risk Screening Assessment. As I discussed with Susan Gahry of SECOR during our 19 April 2000 <br /> phone conversation, SECOR may prepare this report, if it wishes. However, Board staff will <br /> examine the risk assessment for applicability to groundwater resource protection and compare the <br /> risk assessment values with the water quality goals listed in A Compilation of Water Quality Goals <br /> (March 1998), the California Water Code, and other sources related to the protection of groundwater <br /> quality. The values most protective of the groundwater resource will be used to determine whether <br /> remedial strategies have been successful and whether"no further action" status can be granted. <br /> 2. The report states that the method of measuring free-phase product in wells is an interface probe. <br /> However, in the report's discussion of free-product monitoring and removal, the method of product <br /> measurement is stated as a disposable bailer. The actual method used for measurement of free- <br /> product needs to be clarified. Also, if a bailer was used, the report should state whether the product <br /> thickness was measured or visually estimated. <br /> 3. Discussions with Ms. Gahry suggest that Site wells are fairly poor producers. As a result, purging <br /> the wells using more traditional methods (i.e. disposable bailer) completely evacuates groundwater <br /> from the well. The report states that sampling occurs once groundwater has recovered to "80% of its <br /> original level"within the well. This method of purging typically causes turbulent flow through the <br /> well screen and filter pack, mixing of stagnant water and formation water within and adjacent to the <br /> screen, and disturbance of sediments residing in the bottom of the casing. This, in turn, could result <br /> in samples not representative of the formation due to chemical alteration of groundwater, aeration of <br /> groundwater, and entrainment of fines into groundwater entering the well. Tower Park should <br /> prepare an evaluation of alternate purging and sampling techniques (e.g., low-flow <br /> California Environmental Protection Agency <br /> �a Recycled Paper <br />