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CaliforniaKegional Water Quality Co of Board <br /> Central Valley Region <br /> Katherine Hart, Chair <br /> p1l vp M <br /> 11020 Su e -32,Rancho Cordova,Califomia 95670-6114 <br /> Matthew Rodriquez 4-3291 •FAX(916)464-4645 Edmund G.Brown Jr. <br /> Secretaryfor tit[ <br /> P#200 <br /> .waterboards.ca.gov/centralvalley Governor <br /> Environmental Protection 1�11 <br /> 5EP <br /> ikL <br /> ►. <br /> ew- <br /> 1 1�1 IC <br /> 9 September 2011 <br /> W. Michael Carroll <br /> San Joaquin County Dept. of Public Works <br /> Solid Waste Division <br /> P.O. Box 1810 <br /> Stockton, CA 95201 <br /> REVIEW OF REVISION TO SAMPLING METHOD - EVALUATION MONITORING <br /> PROGRAM WORK PLAN, CORRAL HOLLOW LANDFILL, SAN JOAQUIN COUNTY <br /> Central Valley Water Board (Board) staff has reviewed Revision 1 of the Evaluation Monitoring <br /> Program (EMP) Work Plan, which provides a rational for changing the proposed initial <br /> borehole design and groundwater collection method to characterize the nature and extent of <br /> landfill impacts at the Corral Hollow Landfill. The 13267 Order requires the Discharger to <br /> install a minimum of three groundwater monitoring wells and other borings deemed necessary <br /> to define the nature and extent of contamination. <br /> The work plan dated 8 August 2011 initially proposed to install three temporary wells (MW-9 <br /> through MW-11) to meet the requirements of Task 1 of the 13267 Order. However, the <br /> Discharger has raised concerns about the integrity of the borehole and potential sloughing <br /> during the period of determination. Instead of drilling and installing three temporary wells, <br /> Revision 1 now proposes to drill small diameter boreholes to an approximate depth of 80 feet <br /> below ground surface using hollow stem auger. Once the target depth is reached a <br /> hydropunch sampling tool will be advanced beyond the bottom depth of the borehole into the <br /> saturated zone. The sampling tip and casing will remain in the borehole for the collection of <br /> grab groundwater samples and measurements of groundwater elevations. <br /> If the boring locations are deemed appropriate for permanent wells, the Discharger will <br /> construct wells at these locations in accordance with the EMP work plan dated 8 August 2011. <br /> If these boring locations are not appropriate for well installation, the Discharger will proceed <br /> with locating step-out borings to delineate the extent of groundwater contamination. These <br /> locations will be determined by groundwater flow direction measured in the hydropunch <br /> boreholes and concentrations of volatile organic compounds detected in the initial grab <br /> groundwater samples. Borings that will not be constructed as wells will be destroyed in <br /> accordance with San Joaquin County Department of Environmental Health guidelines. <br /> Other changes have not been proposed and staff understands Revision 1 changes the <br /> borehole design and groundwater collection method only and that all other scopes of work <br /> California Environmental Protection Agency <br /> 0a Recycled Paper <br />