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I <br /> 4.0 CONCLUSIONS AND RECOMMENDATIONS <br /> r <br /> Groundwater levels have risen an average of 1.43 feet since groundwater levels were last <br /> measured on November 12, 1999. The groundwater gradient was calculated at 0.001 foot/foot in a <br /> �h. northeasterly direction. ! <br /> Concentrations of dissolved gasoline hydrocarbons in the groundwater samples collected this <br />+- quarter from MW-6, MW-7, VW-1 and VW-2 show a continued decline from previous sampling <br /> results. Concentrations of TBA and 1,2-DCA detected in VW-2 during the fourth quarter of 1999 <br /> sampling were confirmed in this quarter's samples. Xylenes were detected in the Irrigation Well#2 <br /> at a concentration of 1.5 ppb. <br /> The SVE system and air sparge pump operated consistently through the first part of quarter. Mass <br /> removal rates have declined to 7.68 pounds per day. Based on this decline, ENSR temporarily shut j <br /> down the system to conserve fuel. Between December 2, 1999 and January 6, 2000, a total of <br /> 281.4 pounds of hydrocarbons were removed b the system. Since startup on <br /> Y Y p June 2, 1999, a total <br /> of 8,159.6 pounds have been removed. <br /> Based on these conclusions, Ramage Environmental recommends the following course of l <br /> environmental corrective action: <br /> 1. Continue to monitor and sample groundwater from the four water table wells and Irrigation Well <br /> #2 on a quarterly basis. The next quarterly groundwater monitoring is scheduled for May 2000. <br /> - b <br /> 2. Drill a soil boring near the former UST to confirm the remediation of vadose zone soil and to <br /> evaluate the vertical extent of impacted soil and groundwater.. <br />. <br /> �f <br /> 4 <br /> I <br /> I <br /> I <br /> � II <br /> k _ 7 <br /> i. <br />