OFR08-07, Washington County Landfill Logging Project: Borehole Geophysical Tests for Presence of Fracture Flow at a Perfluorochemical Contamination Site

Abstract

The Washington County Landfill located near Lake Elmo, Minnesota is a source of perfluorochemicals that have contaminated groundwater in the area. A project completed in 2007 by the Minnesota Geological Survey (Runkel and others, 2007) determined that flow through fractures is an important part of the bedrock hydrogeologic system in an area of Lake Elmo one to two miles southwest of the landfill. The objective of this project, sponsored by the Minnesota Pollution Control Agency (MPCA) was to collect borehole geophysical data from three bedrock monitor wells within a few hundred yards of the landfill (Fig. 1) in an effort to identify bedrock fractures and characterize their hydraulic properties in the open-hole intervals of these wells. This information will allow the MPCA to determine if there are preferential groundwater flow paths in the bedrock at the Washington County Landfill, an important consideration for devising remediation and monitoring strategies at the site.