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North-Central Section - 37th Annual Meeting (March 24–25, 2003)

Paper No. 2
Presentation Time: 8:15 AM

ADDRESSING ENVIRONMENTAL HAZARDS AND ENGINEERING CHALLENGES IN THE UPPER MISSISSIPPI VALLEY LEAD-ZINC DISTRICT, WISCONSIN


BROWN, B.A.1, MUDREY, M.G., Jr.1, CZECHANSKI, M.L.1, REID, Daniel D.2 and HUNT, T.C.3, (1)Wisconsin Geological and Natural History Survey, Univ of Wisconsin-Extension, 3817 Mineral Point Road, Madison, WI 53705, (2)Wisconsin Dept Transportation, 3502 Kinsman Blvd, Madison, WI 53704-2507, (3)Reclamation Program, Univ of Wisconsin-Platteville, 712 Pioneer Tower, University of Wisconsin-Platteville, Platteville, WI 53818, babrown1@facstaff.wisc.edu

The Upper Mississippi Valley Lead-Zinc District of Wisconsin, Illinois, Iowa and Minnesota produced nearly 10 million tons of lead-zinc ore from the 1820s until the last mine closed in 1978. Although considerable ore remains, the district is unlikely to be mined in the future. As rural residential development increases, the abandoned workings, particularly poorly sealed shafts, can be a hazard. Most low-sulfide waste rock has been recycled as aggregate, making it difficult to find any surface evidence of small, older mine sites that may cause problems.

Specific hazards and engineering problems include (1) locally degraded groundwater from lead-zinc sulfide mines, (2) leachate from roaster-pile waste, and (3) minor ore bodies and shallow abandoned mine working encountered during highway construction. Reclamation was undertaken by the Wisconsin Department of Natural Resources (1 and 2) and the Wisconsin Department of Transportation (3), with assistance from the Wisconsin Geological and Natural History Survey.

High sulfate in groundwater samples was noted in 1978 following closure and flooding in an area where large mines had operated for over 50 years and a drawdown cone had developed over a 20-square mile area. A well-replacement program near Shullsburg restored potable water supplies. Onsite reclamation consisted of establishing vegetation on the tailings and shipping the crushed waste rock for aggregate.

Leachate from zinc roaster waste piles produced over 100 years resulted in highly acidic and metal-rich surface water near Mineral Point. The roaster piles were successfully reclaimed by surface grading and contouring along with neutralization and fertilization to allow vegetation to establish. This was accomplished at a fraction of the cost of removal of the roaster waste piles. Previously undiscovered sulfide mineralization and associated rock alteration exposed during highway construction along US 151 near Mineral Point resulted in the need for engineering redesign, slope redesign, slope stabilization and vegetational planting. District mine maps of the Wisconsin Geological and Natural History Survey, reclamation experience in the area, and proactive engineering are now being used to anticipate problems in the design and construction for stable road beds and rock cuts by the Department of Transportation.

Session No. 14

Engineering and Environmental Geoscience
Tuesday, 25 March 2003: 8:00 AM-12:00 PM
Geological Society of America Abstracts with Programs. Vol. 35, No. 2, February 2003, p.46
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