IDENTIFYING PATHWAYS FOR SANITARY SEWER PATHOGENS TO REACH DEEP WATER SUPPLY WELLS IN MADISON, WISCONSIN

GELLASCH, Christopher A., Department of Geoscience, University of Wisconsin, 1215 W. Dayton St, Madison, WI 53706, BRADBURY, Kenneth R., Wisconsin Geological and Natural History Survey, University of Wisconsin-Extension, Madison, WI 53705, BAHR, Jean M., Department of Geoscience, University of Wisconsin-Madison, 1215 W. Dayton St, Madison, WI 53706, BORCHARDT, Mark A., USDA-Agricultural Research Service, 2615 Yellowstone Drive, Marshfield, WI 54449 and ALEXANDER Jr., E. Calvin, Department of Earth Sciences, University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455, gellasch@wisc.edu

Previous work conducted by the Wisconsin Geological and Natural History Survey indicated that human enteric viruses from leaking sewers are present in several municipal wells in Madison, WI. These wells are the drinking water source for the City of Madison, are typically 700 to 900 feet deep, and penetrate a regional aquitard. Unlike other constituents used in wastewater identification that are ubiquitous in urban settings, human enteric viruses have only one source: human waste. This makes human enteric viruses an ideal indicator of sewer exfiltration in a groundwater system.

The goal of this study is to examine potential pathways from the sewers to the deep aquifer, and the approach used is detailed monitoring adjacent to a municipal well that had previous virus detects. The municipal well is cased and grouted through the regional aquitard and draws water from a Cambrian age sandstone confined aquifer. The most likely source of human enteric virus contamination is leakage from the local sanitary sewer which consists primarily of 70 year old clay pipes. The site chosen is hydrogeologically appropriate for contributing water to a nearby deep municipal well, and two monitoring wells of varying depth were installed in the upper aquifer at the site. Pressure transducers in the monitoring wells were used to detect any response in the upper aquifer due to pumping in the municipal well. Suction lysimeters were installed in the unsaturated zone between the sewer and the municipal well.

From May to July 2010 sampling was conducted bi-weekly at the municipal well, monitoring wells, lysimeters, and sanitary sewer. Viruses were collected from groundwater on glass wool filters and from sewers as 24 hour composite samples. All virus samples were analyzed using polymerase chain reaction techniques to detect norovirus genogroups I and II, hepatitis A virus, rotavirus, adenovirus, and enterovirus. Both viruses and chloride/bromide ratios were utilized as temporal tracers to establish the length of time required for sewer exfiltration to reach various parts of the aquifer system.

Session No. 152

T3. The Hydrogeological Effects of Urbanization II

Tuesday, 2 November 2010: 8:00 AM-12:00 PM

Room 402 (Colorado Convention Center)

Geological Society of America Abstracts with Programs. Vol. 42, No. 5, p.378

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