CHARLESTON, W.Va. -- On the eve of a much-anticipated trial, more than 350 Boone County residents have reached a tentative deal with Alpha Natural Resources to resolve their lawsuit claiming coal-slurry pollution contaminated their drinking water.

Lawyers for Alpha and the residents came to terms in a last-ditch settlement conference that Boone Circuit Judge William Thompson had ordered just an hour before jury selection was to begin Tuesday morning in Madison.

Opening arguments were scheduled to start next week, and Thompson also had ordered the lawyers to conduct another mediation session over the weekend. The parties had not been able reach a settlement during a previous mediation.

Roger Decanio, a lawyer for the residents, confirmed that a tentative deal had been reached, as did Alpha media spokesman Ted Pile and a court spokesman.

All sides said terms of the agreement were meant to be confidential, so details were not made public.

The settlement is the second major coal-slurry pollution deal Alpha has made with Southern West Virginia residents involving lawsuits it inherited when it bought Massey Energy Co. in June 2011. A previous agreement resolved claims brought by the residents of the Rawl area of Mingo County.

Slurry is the wastewater created at preparation plants by the cleaning of raw coal before shipping the fuel to the market. For decades, coal operators dumped the material in large above-ground impoundments or injected it underground, often into old mine voids.

Residents of numerous coalfield communities say mining activities, including injection of coal slurry, are to blame for discolored, foul-smelling well water and a variety of health problems.

Generally, federal and state laws are meant to prohibit mining activities from damaging drinking water, and mine operators that do are required to provide replacement supplies. But in practice, regulators do not always strictly enforce those laws, and residents are forced to turn to the civil justice system.

West Virginia Department of Environmental Protection officials have said they have not found connections between slurry disposal and contaminated water, but a review by West Virginia University researchers said the DEP had required inadequate monitoring over the years to allow any real conclusions.

In the case that has just settled, about 350 residents were continuing to pursue claims against Alpha over the former Massey Energy operations for slurry pollution in the Prenter and Seth area. Residents previously settled claims against Patriot Coal's local operations.

The trial was to focus on personal injury and property damage claims of 14 individuals whose cases are representative of the rest of the community. The trial also would decide more broadly if all residents who sued are entitled to future medical monitoring costs to ensure early detection of any diseases linked to drinking water contaminated by the mining operations.

Residents are now served by public water lines and no longer rely on their wells for drinking water.

Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.