Material spilled during the rescue of a worker last month at a Trempealeau County sand mine contained elevated levels of arsenic, mercury, lead and other metals.
The Wisconsin Department of Natural Resources released initial results late Wednesday afternoon of water samples taken after the May 21 spill at the Hi-Crush frac sand mine in Whitehall.
The tests show lead concentrations of more than 10 times allowable levels in water sampled near where the spill entered Pocker Creek, which runs into the Trempealeau River. Aluminum was measured at more than 1,000 times the limit.
There also were high levels of beryllium, cadmium, chromium, copper, magnesium, nickel and other contaminants; however, samples taken from the Trempealeau River show concentrations that meet surface water standards, said DNR spokesman Jim Dick.
The Trempealeau River was colored orange in the days after the spill as sediment from the mine made its way to the Mississippi River.
Dick said dissolved oxygen levels in both Pocker Coulee and the Trempealeau River were ”above the level needed to sustain aquatic life” and that the DNR is not aware of any fish kills resulting from the spill.
The tests were done on water samples taken within hours of the spill. Dick said additional samples have been taken since and the DNR will evaluate results as they come in to better understand the environmental impacts.
The DNR did not say if the contamination presents a threat to human health. On Monday the DNR said initial tests showed no signs of “immediate toxicity.”
Workers at the Hi-Crush mine in Whitehall drained a holding pond after a bulldozer slipped into the water. The driver escaped uninjured after about 2½ hours in the air-tight cab.
Hi-Crush officials said the pond contained mostly water, silt, clay and sand, though it could contain trace amounts of a polyacrylamide, which is used to remove silt from the water.