Agenda - Council - 09/25/1990 - Laserfiche WebLink

Home

I I I I I I I I I I i I I I I I I shallow drift aquifer. This aquifer is the most vulnerable and has, in fact, already been impacted by the Oak Grove Landfill. The lower drift aquifer and the directly underlying bedrock aquifer are also susceptible to contamination due to the apparent connection of the upper and lower sand units. The glacial till that separates the upper and lower sand units, described in the EIS as "leaky", has been shown to have a downward vertical gradient and is comprised of interbedded layers of sand and gravel, thus limiting the ability to act as an aquitard. The lower drift buried outwasksand aquifer has also reportedly shown signs of contamination from the existing nearby Oak Grove landfill. The Ironton-Galesville bedrock aquifer is in direct contact and therefore directly hydraulically connected with the buried outwash aquifer due tot a bedrock valley existing near the south and southeast portions of Site D. This direct hydraulic connection greatly increases the potential for groundwater impacts. The groundwater monitoring at Site D is greatly complicated due to the existing contamination of surface water as well as the groundwater in both shallow and deep sand units. The ability to differentiate the source of any detected contaminants would be difficult at best. The intrinsic suitability of Sites D, P, and Q seems to be less than optimal. Conditions at Site P fail to satisfy three of the six primary criteria with Sites D and Q both exceeding one primary criteria, that of the presence of wetlands on-site. All three sites fail to satisfy the majority of the seven secondary criteria without heavily relying on engineering measures to attempt to correct the deficiencies. There appears to be an excessive level of engineering and construction requirements to be addressed to even begin to operate, much less to remediate any possible future contamination. MPCA Groundwater Contamination Susceptibili~ Report The 1989 Minnesota Pollution Control Agency report entitled Groundwater Contamination Susceptibility in Minnesota was designed to demonstrate a method of assessing relative groundwater contamination susceptibility. The parameters utilized in the evaluation included aquifer materials, recharge potential, soil materials, and vadose 22