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EDC Meeting Notes June 18,2013 Page 4 decomposing garbage in the dump. The greatest risk posed by the migration of landfill gas outside of the dump is the potential for methane, in particular,to migrate into future buildings and concentrate within the buildings at explosive levels. However, at the present time there is no development(aside from DSI/Transoma) on the east side. Since October 2010, the City and Barr have conducted vapor monitoring and submitted reports to the agency on a routine basis. The majority of the monitoring has been favorable indicating the capped dump is restricting vapor migration, but several of the perimeter monitoring wells on Block E have consistently shown elevated levels of methane since 2010. That has triggered initial contingency actions under the plan and additional vapor wells were installed which indicate the vapor migration is limited primarily to the Block E area. According to Barr,there are currently no significant health risks because Block E is vacant and not yet developed (i.e., there are no buildings for methane to potentially accumulate in). As a side note, the MPCA has released DSI/Transoma from on-going vapor monitoring activities, because the monitoring by the City and the developer(Ryan Co.) indicated there were not vapor migration risks for that area. The timing and need for additional contingency actions at Block E have been under discussion for a while. Along the way, MPCA communications indicated, in an escalating fashion over time, a troubling change in their position regarding developments near dumps (see later section). The MPCA's new concerns have complicated the City's attempts to settle on additional vapor controls in the Block E area. The City, Barr and the MPCA have had several discussions about the possible explanation for the higher vapor readings in Block E beyond the dump cap, but have not identified a clear cause for the elevated readings, although MPCA states that it has experienced similar issues at other old dumps that they manage. Possible factors might include imperfect seal of the dump cap at its edge due to highly variable soil and groundwater conditions at this site or undetected damage to the cap when it was installed. The City has video inspected the horizontal piping system inside the dump cap and did not identify blockages in that part of the system. Emerging MPCA Development Concerns for Dumps The MPCA very recently expressed new concerns regarding developments on or near dumps, particularly when methane is elevated like at Miller dump. Although the agency has been very reluctant to discuss specifics,their concerns seem to stem from their focus on a few bad outcomes at other dump sites. It should be recognized that this is a significant change in position by MPCA compared to their approval of the 2008 RAP for this site and their views for other dump cleanup/development"success stories". Given the significance of this emerging position to future development at New Brighton Exchange,the City has been attempting to initiate further discussions and engagement with MPCA,but little progress has occurred and the MPCA has been reluctant to meet or discuss this issue in detail. Rather, MCPA is choosing to focus on additional demands for venting at Block E (see next section). Most recently,