Kudos to Robert Zullo with the Richmond Times-Dispatch for digging beneath the dueling press releases to shed light on the contamination risks that coal ash ponds pose to drinking water. Focusing on the carcinogenic chemical hexavalent chromium, which has been detected in well water near Dominion Virginia Power’s Possum Point Power Station, he broaches key questions: How much of the chemical is too much? What level should the state permit?

Other questions he touched upon in passing: If hexavalent chromium exists in well water, how did it get there? Did it come from the coal ash ponds, or does it occur naturally in minute quantities?

The Environmental Protection Agency (EPA) sets a drinking-water standard of 100 parts per billion for chromium, which Virginia’s Department of Environmental Quality (DEQ) has adopted as its own standard. However, hexavalent chromium is widely regarded as a more dangerous version of the metal. California has set a separate limit of 10 parts per billion for drinking water for that compound, Zullo reports, reflecting a balance between health risks and the cost to water utilities of meeting the level.

Dealing with its own coal ash problem, the state of North Carolina conducted tests last year of well water within 1,500 feet of coal ash basins, using a standard of 0.07 parts per billion, which it determined was associated with a “potential one-in-a-million cancer risk for an average person drinking this water over an average lifetime.” Tarheel regulators issued several hundred “do not drink” letters to private well owners last year. Critics contended that the 0.07 parts-per-billion level was so strict that even municipal water systems could not meet it, and the state reversed course, telling residents that their well water was “just as safe as the majority of public water supplies in the country.”

The issue surfaced in Virginia when DEQ tested seven private wells near Possum Point and found hexavalent chromium in one — 5 parts per billion, right at the state’s reporting limit. The Southern Environmental Law Center (SELC) commissioned other tests and found another house where the chemical was found at a 1.2 parts-per-billion level.

SELC argues that DEQ should use testing methods that identify the chemical at levels lower than its 5 parts-per-billion standard. Said Greg Buppert, an SELC attorney: “This is a human carcinogen and we should be looking at it at lower concentrations, because we know it’s a concern.”

Bacon’s bottom line: What we’re talking about here is measuring minutes quantities of hexavalent chromium and parsing minute risks. From my (admittedly primitive) understanding, there is no known level above which a given chemical in the drinking water is dangerous and below which it is “safe.” We’re dealing with a continuum in which the statistical risk diminishes with smaller concentrations of the chemical. North Carolina’s level of 0.07 poses a risk of one-in-a-million people getting cancer after a lifetime of drinking the water. That’s crazily low. Even if hundreds of households drank the well water for years, the odds are remote that a single person would get cancer from the chemical.

One must balance that against the cost of eliminating that risk, which in Dominion’s service territory could approach $3 billion. If Virginia rate payers kept that money, what would they do with the money? Presumably, they would spend it on other things. Sure, they might buy a bigger house or purchase more movie tickets. But they also might purchase safer cars, have more frequent medical check-ups, eat healthier food, or join a health club. When we take money from people, whether through taxes or regulation, we fail to take into account the fact that we deprive them of the means to mitigate every-day risks to their health and safety.

Life is full of risks but we as a society say we can live with them. The Virginian-Pilot reports today on a fluke accident in which a beach umbrella on Virginia Beach was blown loose from its moorings in the sand and struck a woman, killing her. Should we ban beach umbrellas to offset the risk of umbrella impalements?

On the other hand, Virginia’s legal limit for hexavalent chromium is more than 100 times North Carolina’s one-in-a-million level. Assuming a straight-line correlation between the hexavalent chromium level and the risk it poses, that implies a one-in-ten-thousand risk or greater for Virginians drinking contaminated well water. That sounds like enough risk to justify having a conversation.

Then there’s a subsidiary question: Do the traces of hexavalent chromium in well water come from the coal ash ponds or do they occur naturally in the environment? That’s not clear yet. DEQ’s consultant found that “natural hydrological processes do not allow for movement of shallow groundwater from the Possum Point Power Station towards the residences on Possum Point Road.” Is that, in fact, true? What are those hydrological processes? Can this statement be verified with reasonable certainty? If the consultant is correct, spending billions to truck the coal ash to landfills would accomplish nothing. If he’s wrong, then Dominion should take responsibility for the contamination.

These are the kinds of questions we should be asking. In “Once in Four Lifetimes,” I tried answering similar questions surrounding the discharge of coal ash wastewater into rivers and streams. Zullo has done a commendable job exploring the groundwater contamination issue. Let’s hope we see more reporting like this.