REGIONAL— Just north of the Laurentian Divide, at the headwaters of the Lake Vermilion watershed, sits a lake that has become the focal point of an ongoing political and scientific battle over …
REGIONAL— Just north of the Laurentian Divide, at the headwaters of the Lake Vermilion watershed, sits a lake that has become the focal point of an ongoing political and scientific battle over sulfate discharges from the mining industry.
Sandy Lake, located about five miles north of Virginia, was once known for its abundant beds of wild rice. But today, this natural aquatic grain has all but disappeared from Sandy Lake, and tribal officials and scientists alike believe it is the discharge of sulfate-laden water from U.S. Steel’s nearby Minntac tailings basin that is responsible for the change.
Sandy Lake has become “the poster child for the tribe’s concern about sulfate and wild rice,” said Dr. John Pastor, a University of Minnesota-Duluth professor who has studied the impact of sulfate levels on this native grain. “Sandy Lake used to have abundant wild rice and now it has none,” he said.
Water quality testing undertaken by the U.S. Geological Survey between 1958 and 1961, found that sulfate levels in the Sand River, just downstream from Sandy Lake averaged 8.5 milligrams per liter (mg/l), which is fairly typical for lakes and rivers in northeastern Minnesota that don’t receive industrial discharges. At the time, the lake and the upper reaches of the river were home to significant beds of wild rice.
Water quality testing done by the Minnesota Pollution Control Agency between 2012 and 2013, found sulfate levels in the lake averaged far higher than was found 50 years ago— about 95 mg/liter, although most test locations exceeded 120 mg/l.
MPCA officials acknowledge it’s the discharge from the Minntac tailings basin that has increased the sulfate levels in Sandy Lake and the Sand River, and that’s why the state regulatory agency has pushed to tighten those discharges as it works to finalize a new discharge permit for the roughly 8,000-acre basin that receives tailings from Minntac’s ore-crushing operations. Currently, sulfate levels in surface water that seeps from the basin averages around 1,000 mg/l, while test wells show groundwater seepage from the basin ranging from 300-1,000 mg/l.
The company has argued that the cost of treating the contaminated water in its massive tailings basin is too high, and they’ve found political backing for that argument from Iron Range legislators, who have pressured state regulators to loosen a state rule, enacted in the 1970s, that limits sulfate discharge to 10mg/l. It’s the strictest such standard in the country, enacted specifically to protect wild rice, an extraordinarily healthful grain that grows naturally in few other places in the world, other than Minnesota.
But while Minnesota may have the strictest sulfate standard in the country, it hadn’t been enforced for decades. Indeed, the long-expired wastewater discharge permit under which Minntac continues to operate its tailings basin, includes no sulfate limit at all.
It wasn’t until tribal leaders and environmental groups starting making waves a few years ago, that the MPCA, under pressure from federal regulators as well, began including the rule when issuing some new permits.
But even as the MPCA moved towards enforcement of the so-called “wild rice standard” for sulfates, pro-business groups like the Minnesota Chamber of Commerce were challenging the science behind the 10 mg/l pollution limit— and Iron Range politicians have been quick to latch onto the chamber’s research to argue for significant weakening of the rule. In late March, after reviewing three years of research and peer review, the MPCA announced a new proposal for a “flexible” standard that would consider several factors (including the amount of iron in the water and organic material in lake and river sediments) in determining how much sulfate can be discharged into a particular lake or river, without negatively affecting wild rice.
Research by Pastor and others has demonstrated that the sulfate level, by itself, in a body of water does not appear to impact wild rice, even at high levels. Yet in the environment, bacteria in lake and river sediments convert the sulfate into sulfide, which Pastor’s research has shown is toxic at quite low levels to wild rice and other aquatic organisms. Research, at the same time, has suggested that the amount of iron in the water and the amount of organic material in sediments, can significantly impact how much sulfate is converted to sulfide. That’s why MPCA officials believe they can now tailor a sulfate discharge standard for just about any body of water using a formula that takes such variables into account.
Sandy Lake a test case?
Sandy Lake could well be one of the first such water bodies subject to the new flexible rule. While MPCA officials had planned to issue a draft of a new discharge permit for Minntac’s tailings basin in March, the agency—under intense political pressure— never released the draft publicly. And, according to Katrina Kessler, MPCA’s Water Assessment Section Manager, no new release has been set.
While the earlier draft permit was expected to seek eventual compliance from Minntac with the existing 10 mg/l standard, the requirements of any new draft aren’t yet known, according to Kessler.
And data gathered by the MPCA suggests developing any new standard, based on the new flexible formula, is certain to be complicated, and likely to be controversial.
MPCA officials gathered data on lake sediments and iron content in Sandy Lake back in 2013. They’ve since plugged those numbers into their new formula, and the results are raising concerns from researchers like Pastor.
According to the MPCA’s calculations, which were recently obtained by the Timberjay, the level of iron and organic sediment found in portions of Sandy Lake should be providing protection for wild rice even with sulfate levels in the water as high as 96.6 mg/l. Lakewide, the new formula suggests wild rice would be protected with an average sulfate level as high as 64.6 mg/l.
Pastor says such results point to major problems with the MPCA’s formula, since it’s clear that wild rice has virtually vanished from Sandy Lake even though average sulfate levels currently aren’t much higher than levels that the MPCA’s new formula suggests should protect wild rice.
“I have no idea how they can justify this,” said Pastor. “If their model predicts that sulfate levels can reach 70-90 mg/l in a lake where wild rice is going extinct, then the [MPCA’s] model is even worse than I think.”
Pastor said the sulfide readings measured by the MPCA are also quite high in most of the tested locations in Sandy Lake. While the agency’s new formula suggests that iron in water can provide some level of protection, by chemically binding up the sulfide, Pastor said his latest research suggests iron doesn’t have the protective ability that initial research suggested.
“I suspect two things may be happening,” he said. “The iron sulfide is precipitating on the roots and inhibiting nutrient uptake and therefore seed production,” which is something that Pastor said he’s already seen in his experiments. In addition, he said, “the sulfate is flowing in from the mine and being reduced to sulfide faster than the iron can precipitate it. This excess unprecipitated sulfide is toxic to seedlings, as our experiments have also shown.”
MPCA officials are quick to point out that the results of their calculations don’t necessarily translate directly into a potential standard. Part of the problem may be the significant variability of sediment levels and iron concentrations, even within a relatively small water body, like Sandy Lake. For example, the concentration of organic material in sediments varies substantially within the lake, from as high as 33 percent to as low as eight percent.
And iron concentrations vary as well, by more than a factor of two. Pastor said such variability presents real challenges for regulators.
“There is at least a twofold range in iron and a fourfold range in organic matter,” he said. “These are the variables they use to predict sulfide and acceptable sulfate concentrations. How do they propose to sample a lake to obtain reasonably accurate estimates of sediment iron and organic matter with that range?”
Indeed, the effects of such variability is apparent in the MPCA’s own calculations of protective sulfate levels. MPCA has calculated a protection level for sulfate for each of the ten monitoring sites on the lake, and they range from as high as 96.6 mg/l to as low as 28.1 mg/l.
So which number does the MPCA select when setting a new standard? The average, the median, or the 95th percentile? MPCA’s Kessler said the agency is still weighing such questions. “We continue to evaluate the best way to calculate one protective sulfate value for a given waterbody for considering multiple discrete iron and total organic carbon samples,” said Kessler.
At this point, said Kessler, agency officials don’t know whether the standard they ultimately establish for Minntac’s tailings basin will be higher or lower than the current 10 mg/l standard.
Yet even if agency officials can determine a safe sulfate level for Sandy Lake, it’s not clear what steps Minntac would need to take to meet a new standard. The permit that MPCA ultimately issues sets sulfate levels for downstream waters, like Sandy Lake, not for the tailings basin water itself. Because the tailings basin discharge comprises only a fraction of the water entering downstream lakes and rivers, the sulfate levels in the tailings basin could continue to remain much higher, while still allowing for reduced sulfate levels downstream. For example, while sulfate levels in the basin average about 1,000 mg/l, sulfate levels at Sandy Lake average about 95 mg/l. Dilution continues to remain a significant mitigating factor for pollution discharge, according to MPCA officials.
Minntac has already reduced its downstream impact by installing a pumping facility at its Sand River discharge point that returns the water to the tailings basin. That pushes more of the basin’s water out other discharge points, such as to the Dark River, where no wild rice was historically present.
Groundwater seepage is still a factor, however, which means Minntac would either need to find a way to reduce sulfate levels in its tailings basin in general, or reduce its discharge of sulfates through groundwater. Kessler suggests that the final answer will be a combination of the two. Minntac is already subject to a 2011 schedule of compliance to reduce sulfate levels in its tailings basin— and it’s made some progress towards doing so. The company recently switched to a source of incoming water that’s lower in sulfates. In addition, the company is supposed to replace its existing (emissions) wet scrubbers with dry scrubbers that don’t contribute to increased sulfate levels in discharge water.
Whether those actions are sufficient remains to be seen. If not, Kessler notes other methods have been successful in limiting groundwater discharge from hazardous waste sites. Those methods include installing physical barriers, such as sheet piling, or using pumped wells that intercept the flow and could either return the water to the basin or to a treatment facility.