CHARLESTON, W.Va. -- A Marshall County chemical plant has agreed to pay $450,000 for water quality violations that have continued even after West Virginia regulators entered into a pollution settlement with the operation nearly three years ago, state officials said this week.

The state Department of Environmental Protection said the former PPG Industries facility at Natrium already has paid $200,000 of the penalties and proposed a change in the July 2010 deal to include $250,000 more in fines, according to court records.

The DEP proposed the settlement just three months after the West Virginia Rivers Coalition threatened to sue the company, citing Clean Water Act violations that included excess discharges of pesticide contaminated groundwater, mercury, iron and several volatile organic compounds into the Ohio River.

In a court filing, DEP lawyers said the operation has "undertaken significant steps" to reduce its pollution, but "has experienced difficulty ensuring consistent compliance" with limits for certain toxic organic chloride chemicals.

Built in 1957, the former PPG plant is along the Ohio River just north of New Martinsville. Pittsburgh-based PPG sold the facility last year to Atlanta-based Georgia Gulf Corp., and it now operates under the name Eagle Natrium LLC.

For years, the facility has drawn strong criticism from environmental groups because it continues to use what those groups say is an outdated process to make chlorine by pumping salt water through vats of pure mercury. Most of the industry -- representing about 95 percent of U.S.-produced chlorine -- now uses a newer process that does not result in large mercury emissions into the air and nearby water supplies.

The new settlement focuses on groundwater contaminated by three forms of the chemical benzene hexachloride, BHC-alpha, BHC-beta, all constituents of the pesticide lindane. Federal regulators began phasing out lindane in the 1970s, and banned it altogether in 2002 because of concerns over its impacts on human health and the environment.

Lindane has not been manufactured at the Natrium facility since 1961, but groundwater at the site remains contaminated and the pollution is believed to be infiltrating sewer lines and causing water-discharge permit violations, court records show.

The DEP's proposed settlement document indicates the company has spent nearly $1.5 million since 2009 on efforts to deal with the problem, but that violations continued as recently as December 2012. The document says the company has hired the national consulting firm CH2M Hill to "evaluate the issues" and "develop recommendations" to end the violations. The proposal gives the facility until Dec. 31, 2015, to come into compliance.

The settlement is the latest in a long series of actions by state officials to help give PPG more time to end environmental violations, including four instances over the past two decades when state officials backed off tougher water pollution limits for mercury emissions from the Northern Panhandle plant, which employs about 500 workers.

State officials sued the plant in May 2009, only after the Rivers Coalition and another environmental group, Oceana, filed a formal notice of intent to sue PPG to try to force it to stop repeated mercury violations. PPG officials had suggested the DEP file suit, a move that helped the company head off any potentially stronger sanctions or deadlines the citizen groups might have sought in their own lawsuit.

In its deal with the DEP, PPG resolved the agency lawsuit by paying $1 million in fines and agreeing to spend $350,000 on a "supplemental environmental project" to collect household hazardous waste, such as electronics, from the community. That settlement did not include language specifying when PPG had to end its water quality violations.

Mercury is extremely toxic. Depending on the dose, human health effects from exposure can include subtle loss of sensory of cognitive ability, tremors, inability to walk and death. Of particular concern is the fact that mercury becomes more concentrated as it passes from a mother to her fetus. Children with exposure are at risk of having to struggle to keep up in school or needing remedial classes or special education.

After Maryland threatened to sue PPG in 2009 over mercury air pollution, the company agreed to cut those emissions by nearly 88 percent. PPG also agreed to install any "economically and technologically feasible method or equipment that will allow further reductions in mercury air emissions" after Dec. 31, 2013. At least three other PPG facilities, in Louisiana, Canada and Taiwan, have converted to newer technology that does not emit mercury into the environment, according to Oceana.

In October, the Ohio River Valley Water Sanitation Commission, or ORSCANO, gave the Natrium facility a water quality variance that allowed it to avoid having to more quickly make larger reductions in its mercury emissions to the river.

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