Beneath Athens County’s surface lie 285 recently mapped, abandoned underground mines, which can poison drinking water and damage buildings and roads, Ohio Department of Natural Resources officials said.

Some of these mines date back to the 1800s when there were no laws requiring miners to follow environmental standards or to document the extent of their digging, said Chris Gordon, a geologist with the Ohio Division of Geological Survey. Before mining laws established in the 1970s, many mines were left undocumented.

“We’re estimating that there’s thousands more in the state that we don’t know about,” Gordon said.

The map, which was released this month by the Ohio Department of Natural Resources to increase awareness about previously undocumented mines, includes the 285 mines that the Geological Survey has discovered and an additional 64 locations where the boundaries of the mine are unknown.

Thirteen hundred miles of stream in Ohio are polluted as a direct result of the 600,000 acres of underground, abandoned mines in the state, said Terry Van Offeren, the department’s deputy chief of the abandoned mine land program.

Today, water protection groups have to remove coal mine residue from water sources to reduce harmful chemicals such as iron, sulfuric acid and arsenic.

Streams with such chemicals are unsafe to drink and swim in. Animals and microorganisms cannot survive these conditions and will die off completely in parts of streams, said Raccoon Creek Watershed Coordinator Ben McCament.The Raccoon Creek Partnership is a water protection group that has worked for the past decade to reduce harmful chemicals in the water related to coal mine residue.

“We have a really scenic part of the state but at the same time, because of our history, we’ve reduced the quality of life,” McCament said.

To fix the problem, watershed groups add limestone or other materials to the water to neutralize acidity and reclaim the land surrounding the mine by planting vegetation and returning it to its pre-mined state, he said.

The crew has worked on ten different sites, spent $6.7 million in grants and reduced 800 tons of acid — but the job will never end because mines will seep harmful agents indefinitely, he said.

“At some point they will stop, but it could be thousands of years,” McCament said.

Underground mines also pose threats to homeowners. A resident could wake one morning to find the foundation of his or her home cracked because of the roof of an underground mine collapsed into the open mine rooms below, Van Offeren said.

“This is a significant public health and safety issue,” Van Offeren said, adding that pits or cracks even can occur under major roads, and in the 1990s a large collapse occurred under I-70.

In Athens County alone, Mineral Resource Management has spent almost $594,000 to correct mine subsidence since the early 1980s, according to the Abandoned Mine Land Inventory.

While such damage occurs rarely, a crack or pit can form suddenly, and the state provides insurance to homeowners in high-risk areas, Van Offeren said.

The state requires Athens County residents to pay a dollar a year to receive coverage from the Ohio Mine Subsidence Insurance, which covers such damage, but no resident’s claim has exceeded the $100,000 insurance limit, said T.A. Brininger, who works in the subsidence insurance claim department.

The agency responds to about five major subsidence cases a year, but he recalls a case that destroyed a house in a matter of four to five hours 10 years ago, he said.

“Often times people purchase property, and they might not be familiar with the history,” Van Offeren said.