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CALIFORNIA GEOPHYSICAL GROUP, INC. <br /> �4 Box 578341 Modesto, CA 95357 Tel (209) 527-1247 <br /> February 14 , 19974��,�RONM Fax (209) 527-4810 <br /> P <br /> 0 eo web$��V 714 <br /> Public Health Services f hAro a saSan oos <br /> P.O. Boxuin 388County Copped Cq 8S /OiV <br /> Stockton, CA 95201 ��te -� tions 0 1001,0388 <br /> RE: Addendum to Work Plan of March 15 , 1995 <br /> ©arpetro Service Station by <br /> 749 E. Charter Way <br /> Stockton, CA <br /> Site #1060 <br /> In our work plan dated March 15, 1995, we proposed placing a <br /> sparging well near the center of the plume. This well would <br /> introduce oxygen into the water table aquifer, which would <br /> accelerate the aerobic microorganism activity and reduce the <br /> levels in the gasoline plume at this site. <br /> Recently, a new process has come about which introduces oxygen <br /> into the aquifer without sparging. The process has been <br /> developed by Regenesis Bioremediation Products. This company <br /> sells magnesium peroxide in filter socks which can be introduced <br /> . into 2 inch wells below the water table. The magnesium peroxide <br /> slowly releases oxygen into the aquifer and aerobic <br /> microorganisms use the oxygen to reduce the dissolved gasoline in <br /> the water to carbon dioxide. The process is passive and the <br /> dissolved oxygen moves along with the groundwater flow into the <br /> plume area. <br /> We propose to install these magnesium dioxide socks into wells <br /> BM-1 , 2 , 3 , 4 , 6, 7 and 9 and the sparging well VW--2 . These <br /> wells are on the upgradient side of the plume or within the core <br /> of the plume. Wells BM-8, 10 and 11 will be used to assess the <br /> results of this bioremediation activity. This process will take <br /> the place of the air sparging well proposed earlier. <br /> Into each well will be placed the magnesium peroxide socks below <br /> the water table. The socks will hang on a rope attached to the <br /> top of the well. The socks can be removed during quarterly <br /> monitoring to measure the depth to water and obtain water <br /> samples. The dissolved oxygen readings in these wells will <br /> indicate i$: the socks are working. The TPH-Gasoline and BTEX <br /> laboratory results will also indicate if the process is working. <br /> Attached is Figure 1 which is a plot of the well locations. We <br /> have indicated the expected area of coverage of the dissolved <br /> oxygen released from the socks in the wells over a year. This <br /> estimate is based upon the hydraulic gradient bearings during 1996 . <br /> According to Regenesis, the socks will continue to release oxygen <br />