REGIONAL— Disagreements between officials with two state agencies over how to handle waste rock from the planned Hwy. 169 upgrade in Eagles Nest Township has delayed a final decision on which route to select for the controversial project.

Last January, officials with the Minnesota Department of Transportation had promised their final route selection by February. But that deadline came and went, as officials from MnDOT and the Department of Natural Resources worked to resolve differences over how much additional investigation is needed to determine the amount of sulfur-bearing rock that highway construction crews can expect to encounter during construction. MnDOT officials now say they expect to have a final route decision by the end of May.

Sulfide rock at issue

MnDOT’s preliminary selection of Alternative 3A, which would relocate a significant section of the existing highway to the south, would entail blasting and removing an estimated 227,000 cubic yards of bedrock, making it one of the largest rock excavating projects MnDOT has undertaken in years.

Preliminary geological work completed in the area by the Natural Resources Research Institute (NRRI) revealed pockets of sulfide-bearing rock, which is known to produce sulfuric acid when exposed to air and water.

The debate over the extent of the risk, and how to handle the potentially hazardous rock, has swirled around the project for more than three years, contributing to the ongoing delays in the project’s timeline.

While an initial analysis by a MnDOT-hired consultant suggested the risk of acid rock drainage was moderate-to-high, the consultant, Rens Verburg, of Golder Associates, has since classified the project as low risk, based on chemical analysis of rock samples gathered by NRRI.

Yet DNR officials have questioned the change in classification. “DNR does not agree with MnDOT’s consultants that the proposed “low risk” project assignment is reasonable based upon the existing information,” stated Dennis Martin, a DNR geologist. Martin is a member of a technical panel established by MnDOT to make recommendations on the sulfide issue for the Hwy. 169 project. The DNR is recommending that MnDOT follow guidelines established by states such as Tennessee, Virginia, and Pennsylvania, where transportation officials have encountered similar issues in the recent past.

DNR officials have also argued that the sampling undertaken so far was limited to just two potential rock cuts, out of a total of 22 cuts planned. “Seventeen of the 22 total roadcut locations have no existing coincident samples. This biases the results,” stated Martin in a summary of a presentation he made to MnDOT’s technical committee on March 27.

DNR officials have argued for a more robust rock sampling effort, prior to construction, to better characterize the rock that construction crews can expect to encounter in the field. MnDOT officials had previously agreed to undertake a thorough drilling campaign in advance of construction, but have since modified those plans. MnDOT officials, citing the new conclusions of their consultant, have questioned the need for an investigation on the scale urged by the DNR and previously envisioned by MnDOT. Instead, the agency has pushed for a more limited effort, including pre-drilling or channel cutting in areas where high sulfide rock concentrations are known to exist. But Project Manager Michael Kalnbach said the eventual plan will probably be a combination of ideas from both agencies. “No formal plan has been agreed upon by both parties, but we’re getting closer,” he said.

MnDOT is looking to reach agreement on the plan soon, however, since they’ll need to complete rock characterization over the summer to stay on track with project design timelines. “We want a 60-percent design by August and we’ll want the rock characterization done by then,” said Kalnbach.

In general, the sulfide deposits in the area are believed to be relatively small and scattered, so the process of locating the deposits can be difficult. “It’s a pretty big area we’re trying to assess,” said Kalnbach.

MnDOT’s consultant now argues that the initial visual survey undertaken by NRRI overstated the amount of sulfur-bearing rock in the area. Subsequent chemical analysis of the rock found that the vast majority (88 percent) contained less than 0.15 percent sulfur, which is widely considered a safe cutoff level when it comes to the risks of acid rock drainage. Sixty-two percent of the samples included no detectable sulfur, according to the consultant.

DNR officials have raised questions about the accuracy of the chemical analysis undertaken on the rock samples by NRRI, pointing to potential processing irregularities noted in the NRRI report.

While the DNR encountered its own sulfide rock problems during reconstruction of the new Lake Vermilion State Park access road, and has expressed strong views on the subject as it pertains to the Hwy. 169 project, it is MnDOT that has the ultimate decision-making authority on the project.

Environmental review

Even as state officials debate the sulfide issue, MnDOT and the Federal Highway Administration are preparing responses to the nearly 200 comments they received from the public following the release of the draft environmental assessment last December. Once the responses are complete, the agencies can issue a final environmental assessment, which will include the route selection.