4.7. SR 04-20-1998 - Laserfiche WebLink

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downward instead of laterally. It may be that this is one slug of contamination moving through. Ground water monitoring in bedrock. The landfill feels confident by additional testing they have done that low levels of VOCs found in the bedrock at their site is not a contamination issue. Since this issue involves the aquifer that serves thousands of people, staff does not feel comfortable accepting the landfill's findings on face value. The landfill has agreed to continue ground water monitoring in the bedrock. Ground water monitoring northeast side of landfill. Wells 32 and 33 on the north side of the landfill are showing VOC contamination that may be due to landfill gas. The proposed demolition cell should help resolve this issue, if it is gas. If the proposed demolition cell is not approved, additional gas extraction wells will be installed to see if the contamination dissipates. Potential contamination in Rice Lake drainage. Very low levels of VOCs have been detected in Rice Lake, which is the swamp to the west of the landfill. Rice Lake drains to Tibbits Brook, which in turn empties into the Elk River and Lake Orono. There is no reason for alarm at this point. The type and levels of VOCs found could possibly be naturally occurring. Staff and the landfill will be further researching this issue. Lysimeter check. Liquid and VOC contamination has been detected in the secondary containment for the landfill's leachate collection tank. The landfill believes it is caused by landfill gas and moisture contained in the clay used for the secondary containment. Additional work will be done to verify this theory. The landfill is trying to convince MPCA to use volume to determine if there is a leak in the leachate collection system (e.g. 1,000 gallons put in the tank, a 1,000 gallons remain, no leak). Staff agrees with this approach. Testing at Old City Dump. The results of testing at the Old City Dump are consistent with past years. No trend up or down can be determined. These results are still below action limits where clean up is required and logical, however, staff is recommending we continue test to be safe.