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05/01/2008 14:19 FAX 209 8316439 CITY OF TRACY <br /> ' I 1 0 0 1A006/007 <br /> Geomatrix <br /> MemorandumP <br /> TO: Mike Infurna DATE: <br /> Apri130, 2008 <br /> San Joaquin County <br /> Environmental Health Dept. <br /> FROM: Mari Gilmore, Geomatrix PROJ. NO.: 7065.001 <br /> CC: PROJ. NAME: TAOC Tracy Pump Station <br /> SUBJECT: Destruction of 5 Monitoring Wells in Tracy, CA <br /> Geomatrix Consultants,on behalf of Chevron Environmental Management Company(Chevron)and <br /> Union Pacific Railroad(UPRR),plans to destroy five monitoring wells located at or associated with the <br /> TAOC Tracy Pump Station Property, 880 Beechnut Ave.,Tracy, CA, 95376, on May 28`h-29`h,2008 (see <br /> attached Figure). Two wells are located on the property(REW-2 and REW-3),which is co-owned by <br /> Chevron(65%)and UPRR(35%). Two wells are located north of the property(Well-E and Well-F), in <br /> the UPRR right-of-way. One well is located south of the property(REW-1), in the City of Tracy right-of- <br /> way. Well construction details are included in the attached Table 1, and historical groundwater analytical <br /> data is included in the attached Tables 5,6, and 7. Permission to destroy the monitoring wells was granted <br /> by the Regional Water Quality Control Board in a letter dated December 14, 2007(attached). Geomatrix <br /> will contract with RSI Drilling, a licensed driller(C-57#802334), to destroy the five monitoring wells. <br /> Prior to conducting field activities, Geomatrix will prepare a health and safety plan and JSAs,appropriate <br /> permits will be obtained,and Underground Service Alert(USA)will be contacted. In addition, a private <br /> utility locator will be contracted to clear the well locations of underground utilities. <br /> The well boxes will be removed and the wells will be destroyed by removing the 2-or 4-inch-diameter <br /> Schedule 40 PVC casing and screen and overdrilling the well borehole with hollow-stem augers to <br /> remove the annular material(filter pack,well seal)to the total well depth. The boreholes will be grouted <br /> from total depth to ground surface using a tremie pipe. Wells REW-1,Well-E, and Well-F will be <br /> overdrilled to approximately 17 feet below ground surface(bgs)with an 8.25-inch-diamter auger, and will <br /> require approximately 48 gallons of Portland Type UII cement grout each for destruction. Wells REW-2 <br /> and REW-3 will be overdrilled to approximately 18 feet bgs with an 8.25-inch-diameter auger, and will <br /> require approximately 50 gallons of Portland Type UII cement grout each for destruction. Boring <br /> 2101 Webster Street,12th Floor Tel 510.663.4100 <br /> Oakland,California 94612-3066 Fax 510.663.4141 www.geomatrix.com <br />