Agenda - Council - 10/22/1985 - Laserfiche WebLink

Home

Mr. Daniel A. Comeau Page len lhe laboratory data for the August 28-30 Sampling event is expected to be available in late September. The data will be analyzed as part of the on-going internal evaluation process and will be shared with MPCA staff. If the need for additional new monitoring activities is apparent, then a proposal will likely be submitted to MPCA in October. If approval is granted, then a driller will be retained and the field program initiated as soon as possible. The "areal and verticle (sic) variations in lithologies" and the need for subsequent monitoring wells are being evaluated as data become available. Useful information includes water level data, water quality data, and drilling logs. The area of water quality impact downgradient of the landfill will be evaluated both horizontally and vertically. The horizontal extent of water quality impacts will be evaluated with laboratory data from at least 2 rounds of samples from the in-place groundwater monitoring wells. Additional wells, which may become necessary, will be installed within and/or adjacent to the existing monitoring well network. At the time of this writing, the results from the second round of sampling are not yet available. The vertical extent of groundwater impacts downgradient of the landfill will be bracketed by a series of well nests. The well nests contain screens at different vertical locations throughout the thickness of the aquifers. Four wells have recently been installed to better define vertical water quality characteristics. Laboratory analysis of samples from the new wells is not yet available. It is anticipated that addqtional groundwater monitoring wells will be installed to determine the significance, if any, of water quality results reported for MW-4B. It is likely that a proposal to install additional groundwater monitoring wells, if necessary, will be submitted to MPCA in October. During drilling operations in February and March, attempts were made to collect undisturbed samples of the clay till unit for laboratory permeability testing. No undisturbed samples were collected which were suitable for laboratory testing because of the stony nature of the clay till unit. Grain size analyses have been conducted at the screen intervals. Coarse grained materials are sampled at five-foot intervals during drilling. Fine-grained materials (clay) are sampled continuously during drilling. The porosity of the drift material can be estimated from charts and standard hydrogeological textbooks and/or by Hazen's approximation. A more meaningful hydrogeological property is formation permeability. In situ permeability tests have not been conducted at this time. It is