DUNDEE, Mich. — Two Republican lawmakers want Michigan’s Monroe County to be declared off limits for deep underground injection of brine waste products from conventional oil drilling, citing a potential for groundwater contamination because of that county’s highly porous Karst geology.

The outcome of bills introduced into their respective chambers recently by state Sen. Dale Zorn (R., Ida) and state Rep. Jason Sheppard (R., Temperance) could have broader implications across Michigan and Ohio because of their amount of Karst.

“A Karst formation is like an underground river,” Mr. Zorn said. “We know this Karst area does have water flowing through it. If anything in the ground gets in there, it’s going to contaminate water.”

Mr. Zorn and Mr. Sheppard said they are not against energy exploration, but said the sensitive geology of Monroe County is not conducive for waste products to be injected underground.

“Any slip-up or error could ruin a lot of wells and a lot of farm fields,” Mr. Sheppard said.

Karst, which includes limestone and other types of bedrock that can dissolve, is known for its porous, Swiss cheese-like formations.

The U.S. Geological Survey estimates about 20 percent of America is underlain by it.

Nearly all of Florida has it.

Only about 3 percent of Ohio has Karst geology near its surface, but much of that is in northwest and central Ohio, especially Delaware County. Portions of Seneca, Huron, Sandusky, Erie, and Ottawa counties, including the Marblehead Peninsula and the Lake Erie islands, also have Karst beneath them, according to the Ohio Department of Natural Resources.

The issue came to the attention of the two Michigan legislators when Trendwell Energy Corp. of Rockford, Mich., applied for a permit to drill an underground injection well for brine wastes in Monroe County’s Summerfield Township, which is in the western part of the county just south of Dundee, Mich.

Trendwell is a small energy firm with three wells producing oil in Monroe County, the first starting in 2012.

Each is expected to produce oil for five to seven years, Todd Mall, company president, said.

“We recognize there is some unique geology there. However, we believe it can be done safely,” Mr. Mall said of drilling and waste-injection.

In a letter to the Michigan Department of Environmental Quality — the agency reviewing the permit application, Trendwell committed itself to inject only brine wastes from its own conventional oil drilling down the Monroe County well if it is authorized. It will not inject waste fluids from a hydraulic fracturing, or “fracking,” operation, Mr. Mall said.

Adam Wygant, section supervisor for the Michigan DEQ’s oil, gas, and minerals unit, said the permit will be limited to Trendwell’s brine products from conventional oil drilling if approved.

Michigan has a lot of experience with injection wells: There are 1,300 of them across the state, 700 for disposal of waste fluids. The other 600 were drilled to help improve the performance of oil-producing wells, such as by enhancing pressure.

The state has 4,500 active oil wells and 11,000 natural gas wells, Mr. Wygant said.

He said more than 50 may have been drilled in known or suspect Karst areas — mostly in Antrim County, between Traverse City and Gaylord.

Monroe County’s Summerfield Township had an injection well about a mile from the site where Trendwell wants to drill. Located in Section 19, it was drilled by another operator in the 1980s and capped in 2004, Mr. Wygant said.

Trendwell wants to drill in Section 18. It operates 16 other injection wells in northern Michigan, Mr. Mall said.

The key, according to Mr. Wygant, is the type of buffer below the Karst. The Trendwell site has about 300 feet of largely impervious shale — vertically, the length of a football field — beneath its near-surface Karst, he said.

“We have to evaluate the thickness and characteristics of that,” Mr. Wygant said.

The Trendwell injection well would be 1,200 feet — nearly a quarter-mile — deep, he said.

The modern era of fracking has been a game-changer for the oil and gas industry globally. But waste has been injected underground in the state since the 1940s, he said.

Contact Tom Henry at: thenry@theblade.com, 419-724-6079, or via Twitter @ecowriterohio.

First Published June 13, 2015, 4:00 a.m.