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r, <br /> PUBLIC HEALTH SERVICES �0 <br /> SAN JOAQUIN COUNTY =` z <br /> Q� <br /> JOG[KHANNA M.D.,M.P.H. <br /> Health Officer <br /> P.O. Box 2009 0 (1601 East Hazelton Avenue) 0 Stockton, California 95201 <br /> 4CIFp RH P <br /> (209)468-3400 <br /> JIM WAGNER JUN 2 7 1991 <br /> DIAMOND WALNUT GROWERS INC <br /> P O BOX 1727 <br /> STOCKTON CA 95201 <br /> RE: Diamond Walnut Growers, Inc. IN REPLY REFER TO SITE CODE: 1781 <br /> 1050 Diamond Street <br /> Stockton, CA 95205 <br /> We have completed our review of the Phase II Underground Storage Vault Investigation as prepared by Weiss <br /> Associates for the above referenced facility; our comments follow. <br /> Groundwater samples collected and analyzed from monitoring well #3,which was constructed by vaults 7 <br /> and 8, exceed the maximum contaminant levels (MCL) for soluble chromium compounds and soluble <br /> chromium +6. Sample analyses during the construction of monitoring well A!�) noted as B8 on table 2, <br /> indicate that the Total Threshold Limit Concentrations (TTLC) for chromium compounds were performed, <br /> however,Soluble Threshold Limit Concentrations (STLC) analyses (INET)were not performed on those total <br /> concentrations exceeding the STLCs. In other words, "the waste extraction test (WET) shall be carried out <br /> if the total concentration of the waste or other material of any substance listed in Section 66699 of Title 22, <br /> equals or exceeds the STLC value but does not exceed the TTLC value given for that substance." At this time <br /> because the soluble portion of the analysis was not performed,we are unable to determine what portion of <br /> the total chromium +6 and total chromium compounds are soluble in the soils between 14 and 40 feet <br /> below grade. In addition, please clarify whether the extraction method performed on total chromium <br /> indicated as deionized water dilution will satisfy the requirement for hexavalent chromium method 3060 <br /> as referenced in Section 66700 of Title 22. <br /> Based upon the data presented in the Phase II Investigation, it will be necessary for you to proceed with the <br /> Problem Assessment Report (PAR), as described in the Tri-Regional Guidelines, to define the lateral and <br /> vertical extent of the problem and propose mitigative or remedial action to clean up the site. It is imperative <br /> that you proceed with the PAR as quickly as possible. An Interim Work Plan may be submitted to include <br /> the recommendations for further work omitted from the Phase II report. The PAR shall be submitted to our <br /> office and Central Valley Regional Water Quality Control Board (CVRWQCB) no later than October 7, 1991. <br /> The PAR should adequately delineate the problem identified in monitoring well #3 by defining the extent <br /> of soil and groundwater contamination both laterally and vertically. Define the"zero line"on site maps and <br /> cross sections for both soil and groundwater. <br /> In addition, pursuant to Section 2652(d) of the Underground Storage Tank Regulations (California Code of <br /> Regulations, Title 23, Subchapter 16) a quarterly monitoring report shall be submitted to Public Health <br /> Services, Environmental Health Division and Central Valley Regional Water Quality Control Board <br /> (CVRWQCB) until the investigation and cleanup of the site is deemed adequate. The report is to show the: <br /> -status of investigation and cleanup activities including the results of all investigations <br /> completed to date; <br /> -proposed continuing or next phase of investigation; <br /> A Division of San Joaquin County Health(are Services �l <br />