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ERI 227903 WOl Former Unoca[Service Station 5098 Stockton California November 12 1998 <br /> well with a submerged well screen Existing well MW10 will continue to be utilized as a deeper <br /> (submerged) screen to continue to evaluate water quality <br /> Well MW 14A <br /> MW14A is proposed to be located near existing groundwater monitoring well MW14, is in an <br /> upgradient location (based on summer gradient information), and will be of single/shallow construction <br /> with the well screen above and below the water table as encountered at the time of drilling This will is <br /> intended to specifically respond to the request of the County for replacement of a well with a <br /> submerged well screen Existing well MW 14 will continue to be utilized as a deeper (submerged) <br /> screen to continue to evaluate water quality <br /> Well MW18 <br /> MW18 is proposed to be located at the southeast corner of the former Unocal property, in a <br /> downgradient location (based on winter gradient information), and will be of single casing/shallow <br /> construction with the well screen above and below the water table as encountered at the time of <br /> drilling This will is intended to provide additional information to verify the lateral extent of dissolved <br /> hydrocarbons in groundwater This well is not specifically requested by the County, however, it is <br /> being installed based on hydrogeologic information available for this site <br /> Wells MW19D and MW19S <br /> • Wells MW 19D and MW 19S are proposed to be located between existing wells MW 11 and MW 12 and <br /> will be constructed in a discrete deep zone (MW19D) as well as in the shallow portion of the water <br /> bearing zone (MW19S) MW19S is intended to specifically respond to the request of the County for <br /> replacement of a well with a submerged well screen MW19D is intended to provide additional <br /> information regarding the vertical extent of dissolved hydrocarbons in groundwater near the former <br /> Unocal site Since existing wells MW-11 and MW-12 are only approximately 30 feet apart, only a <br /> single dual-screen replacement well is proposed <br /> Wells MW20D and MW20S <br /> Wells MW20D and MW20S are proposed to be located in the center of Robinhood Drive (near the <br /> intersection of Robinhood Drive and Pacific Avenue) and will be constructed in a discrete deep zone <br /> (MW20D) as well as in the shallow portion of the water bearing zone (MW120S) These wells are not <br /> specifically requested by the County, however, are being installed based on existing hydrogeologic <br /> information available for this site to provide information regarding the lateral and vertical <br /> extent/migration of constituents in the groundwater <br /> Wells MW21D and MW21S <br /> Wells MW21D and MW21S will be located on the west side of Pacific Avenue,- and will be <br /> constructed in a discrete deep zone (MW21D) as well as in the shallow portion of the water bearing _ <br /> zone (MW21S) These wells are intended to replace MW 17, but are located farther south to be more <br /> downgradient of areas of known contamination, based on existing hydrogeologic information available <br /> for this site These wells will provide additional evaluation regarding the possibility of vertical <br /> migration of dissolved hydrocarbons in the groundwater potentially caused by the pumping of the Delta <br /> College well <br />