COMPLIANCE INFO_PRE 2019 - Laserfiche WebLink

Home Browse Search

Preliminary Assessment Summary Diamond Walnut Growers, Inc. (DWG) April, 1993 Page 2 Underground Storage Tank Investigation - Phase I Soil Borings Slant borings and one monitoring well were installed in the areas of the vaults for the purpose of compliance with the Underground Storage Tank Law, Chapter 16, CCR. Soil samples were collected to ascertain whether the vaults had experienced leakage. The 1991 Weiss Associates report indicated the soil in areas of Vaults 1, 5, and 6 had detections of propylene glycol and ethylene glycol at depths of 27 feet and 45 feet below grade. The soil in the areas of Vaults 7 and 8 experienced detections of chromium, total sodium, total calcium, total sulfates, and total chlorides at depths between 10 feet and 55 feet below grade. Of concern are chromium detections noted at depths of 14 feet and 40 feet in the area of Vaults 7 and 8. It is unknown whether the constituents detected at these depths are detrimental to water quality at this time. Underground Storage Tank Investigation - Phase II, Monitoring Wells Groundwater samples have been collected from monitoring wells constructed adjacent to Vaults 1, 5, 6, 7 and 8 on a quarterly basis since June 27, 1991 at the direction of PHS/EHD. Phase II - Sampling Data from City of Stockton Municipal Supply Wells November 1989, November 1990, and October 1991 sampling results of the on- site City of Stockton (COS) municipal wells #WPI, #WP2, and #WP3 were provided by the COS and included with groundwater monitoring well data collected, in the April 2, 1992 report prepared by Resna Industries for Diamond Walnut Growers (DWG) . Phase II - Report of Investigation Detections of total chromium were reported in the COS municipal well #WPI, #WP2, and #WP3. COS municipal well #WP2 experienced levels of chromium at 54 parts per billion (ppb) which slightly exceeds the MCL of 50 ppb. The COS municipal well #WP2 serves as a back-up well for high water demand only (i.e. , firefighting) . It has been removed from usage due to turbidity problems. At this time, the COS municipal wells #WP1 and #WP3 detections have been below the State of California MCL's for total chromium and sodium, and below the EPA Secondary Standards for chlorides; no standard has been established to date for calcium. Phase III - Current Investigative Status Subsequent quarterly monitoring reports to date have detected constituents in the on-site monitoring wells with monitoring well #3 consistently exceeding State MCL's. B. Proiected Site Activity and Revenue Sources Quarterly monitoring, as required by Section 2652(d) , Health and Safety Code, CCR, is continuing in order that groundwater data be gathered and analyzed for possible remediation consistent with the contaminants identified. The off-site COS municipal wells #WP1, #WP2, and #WP3 will be included in the DWG annual monitoring report to provide summary data. DWG will maintain full financial responsibility for all phases of the clean-up.