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///APEX <br /> n <br /> } 1 r' r <br /> 784 P(a on Avenue,Suite 106 • Fair Oaks,CA 95628 <br /> E N V I R 0 T E C H , IN ( . 1 800 242 5249 • Ph 916 535 0200 • Fax 916 535 0207 <br /> February S, 2000 <br /> Mr Jeffrey Wong <br /> San,Jnaqui# County Public Health Services <br /> Environmental,Health Division <br /> 304:6st Weber Avenue, Third Floor <br /> Stoitkton, Ealifordia 95202 <br /> subject Estimated Mass of Petroleum Hydrocarbon Constituents Remaining in <br /> Groundwater <br /> Colberg Boat Works <br /> '401 North Stockton Street, Stockton, California <br /> Apex Project No COL01 001 <br /> Dear Mr Wong <br /> Apex Envirotech, Inc (Apex), on behalf of Ms Lynn Swanson and Colberg Boat Works, is <br /> ' pleAsed to provide this report estimating the remaining mass of total petroleum hydrocarbons, as <br /> gasoline (TPHg), benzene, and methyl tertiary butyl ether (MTBE) remaining in the shallow <br /> groundwater'beneath Colberg Boat Works, located at 401 North Stockton Street, Stockton, <br /> California (Figures 1 and 2) <br /> This report is based, in part, on information obtained by Apex from Ms Swanson and Colberg <br /> Boat Works and is subject to modification as newly acquired information may warrant <br /> BACKGROUND <br /> Colberg Boat Works has been monitored quarterly for petroleum hydrocarbon constituents in the <br /> gr©tindwater since July,1997 On September 28, 1998, Apex prepai ed the Workplan For Pilot <br /> Test and Feasibility Analysis which proposed using magnesium peroxide socks placed in <br /> monitoring iVMW-3 Magnesium peroxide introduces dissolved oxygen into the groundwater <br /> to stimulatb.the removal of hydrocarbons On January 20, 1999, Apex submitted an Addendum <br /> to Workplan For Pilot Testing and Feasibility Analysis which modified the previous workplan <br /> ;and called for injection of magnesium peroxide utilizing direct push technology This method <br /> would allow greater amounts of magnesium peroxide to be used and would cover a wider area <br /> Mr Wong requested that prior to implementing the remediation plan, a mass balance calculation <br /> be conducted Tor the remi liting TPHg constituents present in soil and groundwater to determine <br /> if airy remediation was actually warranted On April 2, 1999, Apex submitted a report entitled <br />? Mass Balance for Remaining TPHg showing calculations to estimate the mass of TPHg <br /> constituents still present in soil and groundwater Upon review of this report, Mr Wong stated <br /> in a letter dated May 6, 1999 that "the extent of the contamination has not been defined east of <br /> the former UST". <br />