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M <br />WORKPLAN FOR THE INSTALLATION OF LYSIMETERS <br />VDH-18, LT -1 AND LT -2 <br />FORWARD LANDFILL, STOCKTON, CA <br />The Waste Discharge Requirements for the <br />Forward landfill call for a background <br />lysimeter to be placed on the southern portion <br />of the property and two surface lysimeters <br />under Waste Management Unit G. The following <br />workplan describes how and where these <br />lysimeters will be installed. <br />The background lysimeter, VDH-18, will be <br />placed approximately 30 feet north of the <br />existing ground water monitoring well MW -6 on <br />the south side of Little Johns Creek. The <br />ceramic cup of the lysimeter will be placed at <br />a depth of 35 feet and encased in a foot and <br />a half of silica sand. A two foot bentonite <br />seal will be placed above the silica flour and <br />the remaining annular space will be grouted <br />with a 3% bentonite cement. The lysimeter will <br />be protected at the surface by a 6 inch locking <br />box and vault set approximately 4 inches above <br />the ground surface. A surface manhole cover <br />will protect the vault at the surface. <br />Lysimeters LT -1 and LT -2 will be placed in WMU- <br />G to monitor possible leachate generated from <br />the contaminated soils. The exact location <br />will be determined in the field, however, the <br />tentative location is to place them within the <br />boundaries of the WMU and under the two largest <br />lots on the site. Both lysimeters will be <br />drilled at a 45 degree angle for a distance of <br />about 7.5 feet in order to place the ceramic <br />cup at a depth of 5 feet under the ground <br />surface. The cup will be seated in a foot and <br />a half of silica flour and a 2 foot bentonite <br />seal will be placed above the flour. The <br />remaining annular space above the seal will be <br />sealed with a bentonite sand dry mix, hydrated <br />to the surface. No cement grout will be used <br />to secure the lysimeters because it will be <br />desired to retrieve and move the lysimeters <br />when the waste management unit is moved. The <br />lysimeters will be protected at the surface <br />using a locking box and manhole cover. <br />The drilling is tentatively scheduled to take <br />place during the first week of January, 1989. <br />