Test well BN-483, near the Better Brite Superfund Site, was drilled to a total depth of 169 feet below land surface. The Ordovician-age Sinnipee Group, which includes the Galena Dolomite, and the Decorah and Platteville Formations, was encountered from about 25 feet below land surface to a depth of about 160 feet. Analysis of core samples and single-well aquifer tests of the dolomites indicate low matrix porosity (1.8 to 7.7 percent) and low horizontal hydraulic conductivity (5.0 x 10-4 to 3.4 x 10-3 feet per day). Significant differences in hydraulic head between Sinnipee Group dolomites and the underlying Sandstone Aquifer (represented by the Glenwood Formation sandstones in test well BN-483) are the result of municipal pumping from the Sandstone Aquifer. The difference in hydraulic head, along with the low porosity and hydraulic conductivity of the Sinnipee Group dolomites, indicates limited hydraulic connection between the Sandstone Aquifer and the shallow aquifer within the glacial sediments. Because of the low hydraulic conductivity of the dolomites, sufficient water for analysis was recovered from only the uppermost interval of test well BN-483 at a depth of 35–52 feet. No inorganic contaminants of environmental concern were detected. Toluene was the only VOC identified, at an estimated concentration of about 2 micrograms/liter.
1U.S. Geological Survey, Middleton, Wisconsin.
2U.S. Environmental Protection Agency, Region 5, Chicago, Illinois.