SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

San Joaquin County DIRECTOR Donna Heran,REHS Environmental Health Department°p,°.��IN � 1" ASSISTANT DIRECTOR 600 East Main Street Laurie Cotulla,REHS wil'g Stockton, California 95202-3029 PROGRAM COORDINATORS 11tSYli• c7 Carl Borgman,REHS Mike Huggins,REHS,RDI Website: www.sjgov.org/ehd Margaret Lagorio,REHS F o a Phone: (209)468-3420 Robert McClellon,REHS Fax: (209) 464-0138 Jeff Carruesco,REHS,RDI Kasey Foley,REHS APR 0 9 2008 Craig Ogata Director of Facilities Management 222 East Weber Avenue Room 678 Stockton CA 95202 Subject: Human Services Administration SITE CODE: 1257 145 South Sutter Street Stockton CA 95202 San Joaquin County Environmental Health Department (EHD) has reviewed Data Gap Investigation Work Plan (Work Plan) dated March 2008, submitted on your behalf by Weston Solutions, Inc. (Weston) and has the following comments. In the Work Plan Weston proposes the installation of one additional groundwater monitoring well and one soil boring to investigate the vertical extent of the petroleum hydrocarbon contamination in both soil and groundwater, and the destruction of three shallow groundwater monitoring wells by pressure grouting. Monitoring well MW-8 has not been sampled for several years. When it was last sampled it had reported detections of petroleum hydrocarbon contamination. The San Joaquin County Well Standards (Standards) requires that wells that have detections of contamination be destroyed by completely over-drilling the original borehole, removing all contents and backfilling the boring with neat cement grout applied from the bottom up. The other wells may be pressure grouted, but the Standards require that wells destroyed by pressure grouting be completed with a mushroom cap in the following manner: After the well casing is filled with grout and pressurized, an excavation 12 inches in diameter larger than the original borehole must be opened around the top of the well to a depth of three feet below surface grade (bsg). The well casing is then cut 6 inches above the bottom of the excavation, grout applied again to cover the top of the cut casing and fill the excavation to a depth of 2 feet bsg. The top two feet may be filled with native soil and covered with cement or asphalt. Target depth of the proposed soil boring is 100 feet bsg. One groundwater sample for analysis will be collected at total depth. Target depth of the proposed deep groundwater monitoring well is approximately 120 feet bsg. Weston proposes to collect up to 5 grab groundwater samples during the drilling of the borehole for the well from discrete water bearing units they locate between the depths of 50 and 110 feet bsg. The EHD recommends continuous coring of the boring across the target screen depths to ensure placement of the screen interval across the anticipated water bearing unit. The EHD also recommends a maximum screen interval of 10 feet in length for this depth discrete well.