Laserfiche WebLink
Mr. Mike Lecision - 3 - 12 April 2002 <br /> waste as hazardous in order to determine how the waste is managed and disposed. The <br /> Soluble Threshold Limit Concentration(STLC) is also used to classify hazardous waste and <br /> for hexavalent chromium,that concentration is 5 mg/l in the extract. The Waste Extraction <br /> Test(WET) is used to determine soluble concentrations of constituents in a waste, expressed <br /> in milligrams per liter(mg/1) of extract. So, if the soil excavated from the plant contained <br /> hexavalent chromium in excess of either 500 mg/kg or 5 mg/1 of extract, then you would be <br /> required to dispose of it in Class I waste management facility. The TTLC and STLC are not <br /> cleanup standards. <br /> 8. DWG recommends that the extent of groundwater polluted with hexavalent chromium can be <br /> defined by installing two monitoring wells. Presently, the groundwater pollution is defined <br /> by MW-3, which is near the source area, and MW-2, which is sidegradient of MW73 by about <br /> 800 feet. Two additional wells will not be sufficient to define the extent of the groundwater <br /> pollution. DWG must install a monitoring well network that defines the lateral and vertical <br /> extent of the pollutant plume, including upgradient, sidegradient and downgradient. In <br /> addition, at least one well pair shall be installed to sample deeper groundwater and determine <br /> vertical gradient. <br /> 9. Existing data and information about the site shows the presence of various pollutants <br /> emanating from the property and resulting from the Discharger's current or past operation. A <br /> Monitoring and Reporting Program (MRP),which is issued pursuant to Section 13267 of the <br /> California Water Code is necessary to delineate groundwater pollutant plumes and determine <br /> whether remediation efforts are effective. Thus,we have enclosed a draft MRP for your <br /> review and comment. <br /> By 30 May 2002,please submit a response to the comments in this letter, including your <br /> comments on the draft MRP, and a work plan and schedule to install additional monitoring wells <br /> that will fully define the lateral and vertical extent of the pollutant plume. The work plan must be <br /> prepared in general accordance with the attached,Items to be Included in a Site Assessment Work <br /> Plan. <br /> If you have any questions,you may contact me at(916) 255-3082. <br /> Y ERRA <br /> Private Sites Cleanup Unit <br /> Enclosures <br /> cc w encl.: Ms. Margaret Lagorio, San Joaquin County Environmental Health Department, <br /> Stockton <br /> Ms. Jeanne Homsey, ATC Associates,Modesto <br />