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<br /> ------------------- ----------- <br /> . <br /> . Oak Grove Trust Members <br /> March 22. 1994 <br /> Page 7 <br /> potential for an explosive condition. Unfortunately. only Margaret Wells accepted this offer <br /> even though the Trust offered to pay for the cost of installation and the increased energy costs <br /> associated with the system. Two continuous gas monitor alarms have been installed in each <br /> basement The alarms are set to sound if 25% of the explosive concentration of methane is <br /> detected. All of the residences as well as the fire department have been provided with an <br /> evacuation plan. <br /> The Trust has spent a significant amount of time evaluating the gas migration. In <br /> essence. while it is clear that the gas is migrating north from the landfill. it is not clear what <br /> preferred pathway(s) the gas is taking. Landfill gas cannot be analyzed like groundwater: <br /> landfill gas can move up. down. or sideways depending on the path of least resistance. The <br /> path of least resistance is dependent upon factors such as soil density, composition of waste, <br /> moisture, frost depth. water levels, barometric pressure. and other factors. In evaluating <br /> alternatives to addressing the horizontal migration. it quickly became apparent that given the <br /> sandy nature of the soils surrounding the Site. the gas which is currently moving horizontally' <br /> will quickly escape to the aunosphere when the ground thaws in the next two to four weeks. <br /> Given scheduling realities and the amount of time it would likely take to pull the gas out 9"f <br /> the soils under the frost layer, if it could be done at all, it was apparent that the Trust could .. <br /> not remediate the gas migration problem prior to mother nature taking care of the problem by <br /> . thawing the ground. Therefore, the Trust plan. enclosed as Exhibit Q. is to develop as much <br /> valuable data as possible while the ground is still frozen in order to be in a position to make <br /> - the most sound judgment for remedying the problem so it will not occur again next winter. <br /> Both active and passive approaches to the problem are under consideration. EP A and MPCA <br /> have approved this plan. <br /> Horizontal migration of landfill gas is a potentially significant financial issue for the <br /> Trust. The Trust members have always been concerned about having to construct an active <br /> gas system due to emission limitation exceedences from the gas vents, whether measured at <br /> the vents or the fence line. While this concern has not yet materialized. unfortunately some <br /> of the alternatives for remediating horizontal migration are very similar to the remedies the <br /> members had feared in the event the Site exceeded emission limitations. The cost of <br /> responding to the gas migration will be significant Alleviating the explosion risk to the <br /> homes and collecting data on potential alternatives to remediating the problem will cost <br /> approximately $150.000. The least expensive alternative to remediating the problem will <br /> likely be in the range of $200.000. Other alternatives cost significantly more. The Trustees <br /> and Common Counsel are acutely aware of the potential impact of this issue on the budget. <br /> and are working to minimize the cost of analysis and to fmd a low cost remedial approach <br /> with a high probability of success. , <br /> . 350/22040059 3/22194 <br /> ---------- ----------------- <br />