Laserfiche WebLink
Andrew Smith • - 2 - . 19 December 2006 <br /> July 2006 to non-detect (less than 0.5 ug/L) in August 2006 and rose to 15 ug/L in September <br /> 2006. Benzene has not been detected in the monthly influent samples since January 2006. <br /> Acute and chronic bioassay testing of system effluent samples resulted in 100 percent survival <br /> of the test species. Advanced recommends that groundwater extraction be discontinued while <br /> rebound conditions are evaluated for two months. <br /> REGIONAL WATER BOARD REVIEW COMMENTS <br /> Regional Water Board staff concurs with the recommendation to cease remedial system <br /> operation and evaluate rebound conditions for two months based on low to non-detect <br /> chemical concentrations in the system influent. An evaluation of rebound conditions may <br /> show whether petroleum hydrocarbons in the vicinity of well MW-4 will migrate to the area of <br /> extraction well EW-1 over time. <br /> Advanced states that installation of an extraction well near well MW-4 to reduce groundwater <br /> chemical concentrations in this area would indicate a release occurred from the USTs <br /> because MW-4 is located downgradient of the USTs and upgradient of the ASTs. While this <br /> statement is plausible, it cannot be made with certainty. Leakage from fuel piping leading from <br /> the ASTs to the dispensers at the dock or an AST release with dispersion of the resulting <br /> groundwater plume could account for pollutants found in groundwater at well MW-4. <br /> The next monitoring and remediation status report for the fourth quarter 2006 combined with <br /> the 2006 annual report is due to this office by 1 February 2007. <br /> If you have any questions regarding this letter, you may contact me at (916) 464-4719 or by <br /> email at mclardy@waterboards.ca.gov. <br /> A4d_ W C61 �2e�zl <br /> Mark W. Clardy, P.G. <br /> Engineering Geologist <br /> Private Sites Cleanup Unit <br /> cc: Ms. Margaret Lagorio, San Joaquin Environmental Health Department, Stockton <br /> Mr. Arthur Deicke, Advanced GeoEnvironmental, Inc., Stockton <br /> MWC/W: slic dodWustinStaftWark\Herman&Helens Marina-Stockton\10-31-06 H&H Marina qmr.doc <br />