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T <br /> ` • <br /> C142M WILL � <br /> �. 1111 Broadway <br /> ' ' ' Suite 1200 <br /> COakland, CA <br /> H2MHILL C FED I ? PM 12: 59 Oaklan4046 <br /> wrr► <br /> P.O. Box 12681 <br /> Oakland, CA <br /> 946042681 <br /> February 17, 2000 Tel 610.261.2426 <br /> 152232.01.01 Fax 610.893.6206 <br /> Proud Sponsor o/ <br /> Mr.Jeff Wong,REHS National Engineers Week 2000 <br /> San Joaquin County Public Health <br /> Environmental Health Division <br /> 304 East Weber Ave., 3'a Floor <br /> Stockton, CA 95202 <br /> Subject: Application and Work Plan for Well Construction <br /> Pacific Gas and Electric Company Maintenance Yard—Former MGP Site <br /> 535 South Center Street <br /> Stockton,California <br /> Dear Mr.Wong: <br /> CH2M HILL Constructors, Inc. (CCI) is submitting the attached application and fee ($178) for the <br /> construction of three monitoring wells at the Pacific Gas and Electric Company (PG&E) maintenance <br /> yard. These wells are replacements for monitoring wells destroyed to allow for remediation activities <br /> performed at the facility under the regulatory direction of the California Environmental Protection <br /> Agency, Department of Toxic Substances Control (DTSC). The well destructions were witnessed by <br /> San Joaquin County Public Health,Environmental Health Division(County)on June 2 and 3, 1999. <br /> The wells to be replaced are wells MW-6, MW-9, and MW-19 (the former well locations are shown <br /> on Figure 0. Spectrum Drilling of Stockton will install the wells using a hollow-stem auger rig. Well <br /> construction will be directed by a CH2M HILL geologist. <br /> Well MW-9R (the designation for the replacement for well MW-9) will be installed to a depth of <br /> approximately 60 feet below ground surface (bgs) using 8-inch diameter hollow-stem augers. Well <br /> casing will be 2-inch diameter polyvinyl chloride (PVC) casing with 0.010 inch slot placed from <br /> approximately 45 to 60 feet bgs. A filter pack of consisting of No. 3 Monterey sand will be placed to <br /> approximately one-foot above the screen interval. A minimum of one foot of bentonite pellets will <br /> be placed as a seal above the sand and the remaining annular space will be filled to the surface with a <br /> neat cement grout. For construction of replacement wells MW-6R and MW-19R, construction <br /> procedures will be the same except an 85's-inch diameter steel conductor casing will be set to <br /> approximately 60 feet below ground surface using 154nch diameter hollow-stem augers to as a <br /> precaution to prevent dragging potentially impacted soil to a deeper zone during well construction. <br /> The steel conductor casing will be grouted in-place and allowed to set a minimum of 24 hours prior to <br /> drilling through the conductor casing to approximately 125 feet bgs. The well installations are <br /> planned for mid-April of this year. <br /> CA6lccns!WkT0NV.E7766Su ONc 211.DOC <br />