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CALIFORNIA REGIOP., WATER QUALITY CONTROL BOARD,.,,,, Cal/EPA CENTRAL VALLEY R�tIION $ 3443 Routier Road, Suite A Sacramento, CA 95827-3098 Phone(916)255-3000 FAX(916)255-3015 r i - �;_� I: ' Pete Wilson,Governor 11 September 1997 Mr. Brian Walker American Savings Bank 17875 Von Karman, Third Floor Irvine, CA 92714 ADDITIONAL PHASE H ENVIRONMENTAL ASSESSMENT, AMERICAN SAVINGS BANK, STOCKTON, SAN JOAQUIN COUNTY I have reviewed your 15 July 1997 letter and the 30 June 1997 Additional Phase II Environmental Assessment, Groundwater Investigation, Closure Report for your property at 222 North El Dorado Street in Stockton. The investigation was conducted to determine the lateral and vertical extent of hydrocarbon contamination at the site and included soil and groundwater sampling and analyses. Your letter requests closure based on full characterization of the site as presented in the report. My comments on your letter and the report are presented below. Appendix B (copy enclosed) of the Tri Regional Board Staff Recommendations for Preliminary Evaluation and Investigation of Underground Tank Sites states that, "Total cleanup of a site, although generally possible, is not always feasible or warranted. Therefore, no further action at a site may be unconditional if the site has been remediated successfully, or with the condition that `no further action is required at this time' if total cleanup cannot be achieved." Appendix B provides the criteria for both low risk vadose zone and low risk groundwater cases and also specifies the information which must be included in a no further action request. Since soil contamination at your Stockton site has gone below the first groundwater, it cannot qualify as a low risk vadose zone site and must be evaluated using the criteria for low risk groundwater. These criteria include: 1) Contaminants remaining in the vadose zone must not reverse or threaten to reverse the mass reduction rate of groundwater pollutants discussed in#4 below; 2) Separate phase product has been removed to the extent possible; 3)No existing water supply wells, deeper aquifers, surface waters, or other receptors are threatened by pollutants remaining in the aquifer; and 4) The total pollutant mass remaining in the groundwater is decreasing at predicted rates and neither creates, nor threatens to create, a risk to human health and safety or future beneficial uses of the aquifer. The report shows that separate product is not present and no surface water is threatened by total petroleum hydrocarbons as gasoline (TPHg) remaining in the aquifer. However, the report does not show whether or not the remaining soil and groundwater contamination threatens deeper aquifers, existing water supply wells or other receptors, such as the basement of the building, subsurface utilities, Recycled Paper Our mission is to preserve and enhance the quality of California's water resources,and ensure their proper allocation and efficient use for the benefit of present and future generations.