6.1. SR 03-20-2000 - Laserfiche WebLink

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4. Review Original contamination The city's major concern regarding the landfill was controlling the contamination generating from that original unlined cell prior to it leaving the boundaries of the site. Ground water in this area is estimated to be moving approximately 50 feet per year laterally and the contamination 5 to 25 feet. The first step in the effort to mitigate the contamination was to define the geo-hydrology of the area. The glacial deposits and associated stratification of the soils in the area made this a time consuming and difficult task. This effort has been pretty much complete and remedial actions (clean-up) has begun. The current attempt at remedial action is using active gas venting (sucking the gases from the waste) to remove the volatile organic compounds from the ground water also. The details of how this is to be accomplished, as well as a contingency plan if it does not work, are specified in the attached license and conditional use permit. Approval of cells 14 to 17 The landfill is divided into cells. Past city reviews included the approval of the cells through number 13. The Council typically approves the concept of the cells contingent on staff having the final approval of the construction details. Approval of cells 14 through 17, which are consistent with the long-range plan at the landfill, is part of this current request. These cells, as are all of those that were constructed after the original cell, are designed with a liner and leachate collection system to control the escape of contaminates. The stipulation that staff has final approval of the construction details is contained in the license and conditional use permit. Bio-reactor (leachate recirculation) The landfill is proposing something a little experimental with cells 14 through 17 called bio-reaction. Instead of the leachate being pumped out of the landfill and taken to a treatment facility, they are proposing to reintroduce it into the waste through a system of pipes. The benefits to the landfill are the waste will be more compressed, leaving them with more capacity, and they can avoid some of the cost for treating leachate. The benefit to the environment is a quicker decomposition, and consequently quicker stabilization, of the waste. There is a concern with the life expectancy of the liner under the waste. Speeding-up the decomposition process is a good thing. A number of bio-reactor pilot projects have been tried in Minnesota so that MPCA can analyze the results. Because of problems, all but three of these have been ordered to cease. MPCA appears to be on top of this issue. Staff feels comfortable with MPCA making the final decision regarding bio-reaction. It appears unlikely that MPCA will approve leachate recirculation.