Hennepin County road workers ran into a costly surprise this fall while rebuilding a road along Elm Creek Park Reserve: a 100-year-old dump containing mercury and other contaminants.
The dump, found under the Goose Lake Road bed north of 109th Av. N., contains household, farm and automotive wastes that date to the early 1900s, project supervisor Don Hannan said. Excavating and removing the debris could cost $700,000 in addition to almost $2 million budgeted for the mile-long stretch of new road extending from 109th to Elm Creek Parkway, he said. The stretch of county road is on the border between Champlin and Dayton, which are sharing a small part of the road cost.
So far the dump has cost an additional $25,000 to drill test holes and haul six truckloads of dump material to an Iowa landfill, Hannan said. He said more test holes will be drilled this week to confirm how big the dump is and see whether contaminants have leached down a steep slope toward nearby Goose Lake in Elm Creek Park.
Workers have unearthed a half-dozen vehicle batteries and brake parts, glass bottles with stoppers, a piece of asbestos, roofing debris and other junk at the landfill, which has been covered with dirt until cleanup work resumes.
The mile-long road project is nearly done. Closed since May, it is to reopen this month with an 800-foot detour around the dump. It will close again for several months when work resumes in the spring, Hannan said.
Contaminants of concern
The debris is contaminated with four metals: mercury, lead, arsenic and selenium, said John Evans, senior environmentalist for the county's environmental services department. He said mercury is the primary concern because tests found levels considered unsafe, though not hazardous, by the state Pollution Control Agency. Debris with the mercury at that level is barred from Minnesota landfills, so it was sent to one in Lake Mills, Iowa, Evans said.
The other three metals are at levels not acceptable for property used for residential construction, he noted.