As the U.S. Environmental Protection Agency closes its books on the Craig Farm Drum Superfund Site, it’s a good time to consider lessons learned from the ordeal with an eye on prevention of future sins against the environment.

First, a brief review: A half-century ago, the Koppers Chemical plant in Petrolia paid brothers Herman and Paul Craig to bury its toxic waste in two strip mine pits on a farm a couple miles east of Petrolia in Armstrong County.

Today, the 117-acre Superfund site is owned and maintained by Kopper, now called Beazer East, under permanent EPA supervision.

After nearly 20 years of cleanup and monitoring at Beazer’s expense, EPA officials plan to remove the Craig Farm from its National Priorities List. EPA required Beazer to excavate and treat 8,200 tons of chemical waste in 55-gallon drums, along with 21,000 tons of contaminated soil, then seal all of it on-site in a two-acre landfill surrounded by test wells designed to detect any seepage, which is unlikely thanks to an impermeable double lining.

The fix wasn’t fast, easy or cheap, but Beazer accepted its responsibility and, EPA says, has met all its cleanup objectives. Ultimately, Beazer customers and stockholders bear the expense.

Perhaps the second-greatest lesson learned since the Superfund was established in 1980 is that industrial messes swept under the rug don’t stay there. Companies today commit millions of dollars in the research and development of greener products and processes, with fewer and less toxic side-products to get rid of.

The greatest lesson is that vigilance must be constant.

Look at oil and gas exploration, an industry under particular scrutiny because of new processes to reach and release natural gas deposits deep underground, in the Marcellus shale deposits beneath vast stretches of Pennsylvania and other states.

One of the processes known as hydraulic fracturing, or “fracking,” has stirred opposition from environmentalists who maintain the process hasn’t been proven safe. They say chemicals involved in fracking threaten groundwater, a claim the industry vehemently denies. The government hasn’t said fracking is safe, but it hasn’t documented enough evidence to say it’s unsafe, either.

Meanwhile, drilling continues across the region. The emerging industry promises new wealth and jobs for the region and a domestic supply of affordable, clean energy — potential benefits for everyone, including a nation overly dependent on foreign oil.

The risks associated with development of a regional gas market seem acceptable, given the level of ongoing vigilance. Monitoring could improve if some of the impact fees was committed to environmental research.

A clean environment is essential; so is a sane domestic energy policy. The promise of the Superfund is that we can enjoy both.