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° :R1iX 1 n` r4y 11 110" •' flpj'• ' - c: 'v v st �,ts F h Y Chevron/South Center 12 Novr-ber 1989 not be advanced to a greater depth. In this case, the hole would be backfilled with bentonite to a level above the top of the aquitard layer and the borehole completed as a groundwater monitoring well, if possible. w.. Wells will be constructed of 4-inch-diameter, schedule 40 polyvinyl chloride (FVC) , blank casing and .020-inch slotted screen. Casing will extend at least 3-feet above and 20-feet below encountered groundwater. A filter pack comprised of clean �- No. 2 Monterey sand will be emplaced in the annular space of each borehole. The sand packs will extend at least 1-foot above the _ top of the well screen, and a bentonite seal comprised of a layer of hydrated bentonite pellets at least 1-foot-thick will be set above the sand pack. Finally, the wellhead will be encased in a locking steel monument casing to protect the wellhead and cement w; grout will be emplaced, fillinV the borehole from the top of the bentonite seal to grade level. After installation, well development will be accomplished using alternate surging and bailing and, if required, pumping of the wells. Development will continue until the water removed from the well. is essentially free of sand and silt. in addition, the wells will be professionally surveyed to establish well location and elevation. This will allow monitoring data r ::ollected from the wells to be used to determine groundwater depth .as well as gradient magnitude and flow direction. After well development, the wells will be monitored and Fled. Standard Operating Pracedures 8 describes GTI rnu..;-c'.toring techniques. Samples from all wells will be analyzed for the presence of BTEX and TPH-as-gasoline using modified EPA Methods 5030/8020/8415. Additionally, if a well is installed I �a GROUNIAV.ATER TECHNOLOGY,INC. Ma 1 r