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PgU1N. <br />THOMAS R. FLINN <br />C ;P <br />DIRECTOR <br />4�IFORti <br />THOMAS M. GAU <br />CHIEF DEPUTY DIRECTOR <br />MICHAEL SELLING <br />DEPUTY DIRECTOR <br />STEVEN WINKLER <br />DEPUTY DIRECTOR <br />ROGERJANES <br />BUSINESS ADMINISTRATOR <br />April 12, 2010 <br />0 <br />P. O. BOX 1810 - 1810 E. HAZELTON AVENUE <br />STOCKTON, CALIFORNIA 95201 <br />(209) 468-3000 FAX (209) 468-2999 <br />www.sjgov.org/pubworks <br />fficLWED <br />kji 1 3 2010 <br />Mr. Robert McClellon, REHS ENVIRONMENT HEALTH <br />PERMIT/OERVICES <br />Environmental Health Department <br />600 East Main Street <br />Stockton, California 95202 <br />SUBJECT: ADDITIONAL SHALLOW PERIMETER LFG MIGRATION MONITORING WELLS AT THE <br />NORTH COUNTY RECYCLING CENTER AND SANITARY LANDFILL <br />Dear Mr. McClellon 1 A <br />Based on site investigations last week, we believe that the difficulty in taking a measurement at the shallow <br />probe of perimeter migration monitoring well SG -16 is due to saturated soils in the shallow probe's sampling <br />interval (to a depth of 10 feet). This saturation is apparently caused by the seasonal water flow in the creek <br />immediately south of that well (Workplan Figure 1). Although soil saturation prevents offsite migration, our <br />investigation indicates that this condition may be local, and that soil north and south of the creek may not be <br />saturated. <br />The intermediate and deep probes (monitoring to a depth of 80 feet) appear to function properly. Data from <br />these probes and from the other 19 migration monitoring wells indicate that our monitoring perimeter is free <br />of combustible gas. Land use within several thousand feet of our property boundary is agricultural. <br />Although the condition at this probe may occur only seasonally, Section 20925 of the California Code of <br />Regulations (CCR) Title 27 requires that we be able to monitor the top ten feet of the soil at a maximum <br />spacing of 1000 feet. To ensure that we meet these conditions for the shallow stratum at all times, we <br />propose to install two shallow single -probe wells in unsaturated soil away from the creek. The location of <br />these new wells will provide separation of less than 1000 feet in conformance to Title 27. <br />Attached, please find the Workplan for the installation of these subsurface LFG migration monitoring wells. It <br />would be useful to install the migration monitoring wells in the same drilling event as the groundwater well for <br />which a workplan was previously submitted. <br />If you have any questions, please contact me at 468-8504 or Joyesh Chandra, Engineer II at 468-3066. <br />Sinceerreelly, <br />W. MICHAEL CARROLL, PE <br />Senior Civil Engineer <br />JC:kb <br />N:\2PerimLFGwells 09\EHD\RMcClellon07-SG16-ShallowWater.doc <br />Attachment <br />LA 10631 (w/Workplan), LA 63108 (w/o Workplan) <br />