Coal Dump Karst: 'Active' or 'Inactive'?
Some say cracked limestone could funnel ash leachate to Lake Huron
February 9, 2010 | By Glenn Puit
Great Lakes Bulletin News Service
|Frank Krist says that over the past decade he’s spotted 30 new ice holes, from tiny to very large, in Presque Isle County’s Fletcher Pond, caused by gas escaping through one of the region’s many karst formations.|
The tricky water movement and sinkholes are caused by the “karst” formations that lace Presque Isle and neighboring Alpena Counties—swaths of fragile, cracked limestone, often filled with underground voids or caves and streams.
According to Mr. Krist, those sinkholes are particularly common in Rogers Township, which might soon host a proposed new power plant—and its toxic ash.
“Swallow holes and other karstic features were found in a large area within five sections of Rogers Township,” he wrote in a recent email, drawing on his health department service and occasional work with state environmental officials.
Those “karstic features” are now part of the public debate over one of Michigan’s most pressing economic and environmental issues: Wolverine Power Supply Cooperative’s proposed 600 MW coal-, petroleum coke-, and wood-fired power plant. The company wants to build it in the gigantic Calcite limestone quarry in Rogers, right next to Rogers City, along with a landfill that would take up to a half-million tons of its ash every year for at least 19 years.
At the state’s Jan. 27 hearing about the landfill, held in Rogers City, critics raised concerns about burying toxic ash in the midst of karst and within several thousand feet of Lake Huron. They said that if the landfill, parts of which would be temporarily uncovered, ever leaked, the escaping leachate might move quickly through the ground into nearby aquifers, streams, or, most likely, the big lake. They urged state officials to wait for pending coal ash storage rules from the U.S. Environmental Protection Agency before acting—rules that the coal industry fears will be much stricter than current, often lax, state-by-state standards.
At the hearing, however, Wolverine spokesman Ken Bradstreet pointed out that the proposed landfill would exceed Michigan’s current standard, which handles coal ash the same way it does tree stumps and clean demolition rubble.
Mr. Bradstreet and several of the firm’s consultants also told the hearing that the dump’s location is acceptable because it would be well away from what they repeatedly described as “active” karst. They said that rock borings the company commissioned demonstrate that the rock below the proposed landfill site is “inactive,” and that leachate from the landfill would not be able to move through it to water flowing directly beneath the site.
However, two experts contacted by the Great Lakes Bulletin News Service said that, in their experience, they had not heard karst described as “active” or “inactive.” One of those experts, like Mr. Krist, pointed to serious concerns about placing landfills of any sort in or near karst geology—no matter its level of activity—and that extreme caution should be used.
Signs of Stability
Yet Ty Black, a senior geologist for the Michigan Department of Natural Resources and the Environment, sees no problem with the landfill’s locale. Mr. Black told the news service that Wolverine’s extensive land borings at the proposed site convinced him that karst is not an issue. Mr. Black helped Wolverine in its search for karst, suggesting boring depths and specialized equipment for looking beneath the ground.
He said that he sees “no karst threat, period. Whatever karst used to be there, perhaps hundreds of thousands of years ago, is collapsed or plugged.”
“As far as a collapse occurring, I cannot see a way it would happen unless we had an almost an impossibility in the Michigan basin,” Mr. Black said. “We are looking at thousands of years of nothing occurring there.”
And while the state geologist stood by the terms “active” and “inactive” for describing the quarry’s karst, he told the news service that the earth directly below the proposed landfill site is more appropriately termed “paleokarst”—ancient fossilized or preserved karst features. Mr. Black also used the terms “relic” and “collapsed” karst to describe what’s beneath the limestone quarry floor.
“There are several signs you would look for,” Mr. Black said. “In the case of limestone quarries, the main fear in a karst area would be extra water flow, or potential catastrophic water flow...if there was a blast out of a quarry wall. This quarry has gone through a lot of years without any such events.”
He said Wolverine’s borings showed nothing indicating the connected channels or cave fragments common in karst.
“I did see one small window (underground), maybe about the size of your fist, in one borehole that suggested a karst surface, but it was definitely collapsed and it was fossil,” Mr. Black said.
He added that Wolverine’s water level measurements and camera work indicated a fairly stable water table.
“When they riled up water in well bores you would get a cloudiness,” Mr. Black said of the tests. “If you have a karst flow, you would see some clear water there. That cloudy water would flow away, like in a stream.”
But two experts contacted by the news service were puzzled by the use of “active” and “inactive” to describe karst. Each said that is not an accurate way to describe such geology.
Last November, in an earlier news service article on Rogers City’s karst controversy, environmental engineer Chris Grobbel, who operates his own consulting firm in Traverse City, told the news service that, when it comes to karst, caution is the rule.
“You need to be very careful placing waste in a limestone quarry with or without karst formations,” Mr. Grobbel said. “If karst cavity-forming occurred, it could be a direct vector of waste into Lake Huron.”
The news service contacted Mr. Grobbel again last week and asked him about “active” and “inactive” karst.
"I am not familiar with the term ‘inactive’ karst,” he responded by email, “and would suggest that it is not a scientific term at all. Karst geology, where it exists, is always karst and remains active for the duration."
He added that karst limestone formations are regional and "do not turn on and off."
The news service also contacted a geologist from coal country: Dr. Henry Rauch, of West Virginia University's Department of Geology and Geography. Dr. Rauch specializes in hydrogeology and aqueous geochemistry in coal mine terrains, and various tools for exploring ground water and natural gas.
Like Mr. Grobbel, Dr. Rauch said he had not heard of the terms used in Wolverine’s descriptions of karst.
"I have never heard the terms ‘active’ and ‘inactive’ with reference to karst,” he responded via email. “There are relative terms that refer to the degree of aquifer development (nature of ground water occurrence and flow) for karst; these are diffuse flow karst, epikarst, and conduit flow karst.
“Conduit flow karst is the least desirable karst terrain (most susceptible to water pollution) to locate and landfill in,” his message continued. “There are also surface karst and buried karst types of various sorts; surface karst is more vulnerable than buried karst.”
Opponents of Wolverine’s landfill plans say that, given the proximity of Lake Huron, possibly conflicting views about the ability of a landfill leak to spread rapidly through karst, and the fact that coal ash leachate contains heavy metals and other harmful substances, how and where Wolverine wants to build its ash dump deserve a fresh look.
Lee Sprague, coordinator of the Sierra Club Michigan Chapter Beyond Coal Campaign, is one of them.
“The phrase 'active' karst geology implies that there are triggers for karst geology to transition from inactive to active,” Mr. Sprague said. Referring to several statements Mr. Black has made during the controversy, he added: “Mr. Black says that carbon dioxide-infused water causes fracturing. SO2 and NO2 also react with limestone.
“Coal plants emit huge amounts of all three gasses,” Mr. Sprague continued. “Or perhaps the additional pressure of 10 million tons of ash will contribute to or amplify geologic activity. We need an independent analysis not paid for by Wolverine.”
And, while Mr. Black is confident that the test data provided to his office by Wolverine is sound, and that science will rule on the matter—and find no threat—some longtime residents, including Mr. Krist, still have questions about karst and coal ash.
“Extreme caution needs to be used when installing a possible source of contaminants over limestone formations in Presque Isle County,” he said.
While not speaking for or against the landfill, Mr. Krist did recount some of his experiences with karst. He recalled one time, several years ago, his department responded to an area resident who detected bacteria in his well water. The health department studied how underground water moved in that area, known for its karst geology, and suspected that nearby sinkholes and limestone formations were funneling contaminants into his well.
“We were concerned about the karst and possible openings on the surface connected to cracks in the limestone,” Mr. Krist said. “We decided to do some tests to see if there might be a connection.”
With Department of Environmental Quality assistance, officials ran tests at the site and were shocked at what they uncovered: In one case, septic tank effluent traveled about 400 feet underground in 18 hours, and was recovered the next day in a drinking well on a neighbor’s property.
Water moving that fast underground, Mr. Krist said, is very unusual, but not in karst; under normal circumstances, water may migrate only a few feet a month.
“Such quick movement through the stone crevices provided little if any filtration of the water,” Mr. Krist said. “Many of the swallow holes in the area had streams and ditches draining into them. Additional dye studies showed that water from the swallow holes was traveling about a 100 feet per day underground and entering near-by residential water wells.”
Glenn Puit is a policy specialist for the Michigan Land Use Institute. Reach him at email@example.com.