PITTSBURGH -- Coal has been king in Pennsylvania for more than a century, and it has left its mark on the state.

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According to Scott Horrell, a state Department of Environment mining manager, "Pennsylvania is the most intensely mined state in the nation. Pennsylvania has the most abandoned mine land features than any state in the nation."

That means there are now hundreds of thousands of homes in Pennsylvania that have been undermined, and now the state is trying to reuse a coal waste product to prevent mine subsidence.

Most of us can't imagine our lives without electricity, but that convenience comes at a price to our environment.

In 2002, over 74 million tons of coal was mined in Pennsylvania. 56 percent of electricity is generated by coal fired power plants in Pennsylvania, a by products of burning coal is fly ash, a fine soot like material.

With 23 coal fired power plants in the state, 13 of which are in Western Pennsylvania, a lot of ash is created. In fact, in 2003 alone, 21 million tons of coal ash was produced in Pennsylvania.

Fly ash can contain heavy metals such as arsenic, cadmium, lead, zinc and must be disposed of in state regulated land, but instead of putting it in landfills, some ash is now being re-used to shore up homes to prevent subsidence.

DEP spokeswoman Helen Humphries, said, "It's a win for industry. They are able to use a waste product and be rid of it at a lower cost and we're able to create a more stable surface below their home that has been undermined."

And mine subsidence is a huge problem in Pennsylvania. In Allegheny County alone there are at least 200,000 homes that have been undermined.

The state DEP is working on one such project now in Chartiers, about 50 miles from Pittsburgh.

DEP's Scott Horrell said, "They're mixing water, cement, fly ash, putting it into a pumper truck, putting it into a line down to voids under homes. It sets up as cement; it stops the subsidence under the homes."

Only about 25 percent of the ash meets the state's safety standards for beneficial use, but not everyone is sure those standards are strict enough.

Dr. Devra Davis, head of the Environmental Oncology Center at the University of Pittsburgh Cancer Institute said, "Some situations it certainly could work if you were mixing this to make a road, mixing it with heavy duty materials that make it truly inert, that's seems like a pretty good use. Other uses where it may be close to seams or ground water may be problematic."

While it sounds like a good solution to two problems, some environmentalists, such as Lisa Graves Marcucci, still worry heavy metals could leak out.

"Of course shoring up a house is an important thing, everyone needs an opportunity to do that. My concern is, has it been researched thoroughly enough to show that there isn't going to be a degradation of ground water."

Marcucci believes there may be a beneficial use for fly ash, but doesn't believe it's been found yet, "I don't see enough independent research saying health has been considered. My main concern is public health."

While public health is a real concern, homeowners who are on the verge of losing their home to mine subsidence may have a different take on the issue.

The DEP's Horrell says they have used the fly ash mixture to reinforce 1,500 homes. Only three of those projects have failed and the home subsided after the treatment.

Helen Humphries of the Pennsylvania Department of Environmental Protection said homeowners in Western Pennsylvania should check mine maps to see if their property located near an old mine.

Homeowners can protect themselves by buying mine subsidence insurance. It's a state program and very affordable. It's less than $1 for every $1,000 of coverage. Coverage for $150,000 would cost $128 a year.

Davis said this is a highly polarized situation, "This is a really tough issue and it's tough for everyone. It's tough for the DEP. It's tough for the people who have to live with this threat. I think if we could lower the volume and expand the information exchange, we'd all be better off."