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Damming the bay's pollution

Here's the gist of the recent report by the U.S. Army Corps of Engineers on the Conowingo Dam: Don't confuse a red herring with a red tide. The notion that all the pollution woes of the Chesapeake Bay could be heaped on one 86-year-old hydroelectric facility on the Lower Susquehanna River was ludicrous from the start no matter how much sediment is trapped behind it.

That's not to suggest that all that sludge is a good thing, but what the corps found is that the adverse impact of those thousands of tons of material sitting behind the dam is minor compared to the excess nutrients that flow into the water upstream or from other bay tributaries on a daily basis. And it certainly wouldn't be worth the billions of dollars required to remove the trapped material. This is exactly what the scientists have been telling everyone for years — from sewage to runoff, lawn fertilizer to chicken manure, pollution comes from the increasing development and intensive use of all the land in the Chesapeake watershed.

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When it rains heavily, there is a so-called "scouring" effect, and a lot of those excess sediments flow over the dam. That can be a problem for the Upper Bay, the study acknowledges. But the loss of those materials also opens up room for more to be trapped, which can also be beneficial, at least temporarily. If the dam weren't there at all, sediments would flow into the Chesapeake Bay unimpeded, and that's not necessarily a big improvement.

Nevertheless, the notion that the Conowingo is chiefly at fault for the preponderance of the pollution in the Chesapeake Bay or for its related woes from the decline of the seafood industry to the growth of "dead zones" where the water lacks enough oxygen to sustain aquatic life was attractive to political candidates, particularly Republicans, in this last election. Governor-elect Larry Hogan was among its most vocal champions, and it's not hard to understand why — it allowed him to demand sacrifices from Exelon Corp., the dam's owner, rather than from people who actually vote.

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How much easier would be the cleanup of the nation's largest estuary if it meant the residents of this state could simply look to large corporations or other states in the watershed to do all the heavy lifting. And it fits nicely with Mr. Hogan's stated goal of overturning the "rain tax," the state-mandated fee Baltimore and nine other subdivisions in Maryland charge residents and businesses to reduce the flow of harmful sediment and other pollutants contained in the runoff from parking lots, roofs and other hard surfaces after a storm.

Mr. Hogan was correct about one thing in this regard. The cleanup efforts will need people living in surrounding states to do more. That's why it's so essential to support the U.S. Environmental Protection Agency and it's Total Maximum Daily Load "pollution diet" that requires everyone in the watershed to make improvements. But in this, Maryland must lead by example, not by dragging its feet when there's an opportunity to reduce pollution.

And while the Susquehanna River accounts for much of the bay's fresh water (the Chesapeake itself is an extension of the Susquehanna valley floor), it's simply not the only source. A big storm like Tropical Storm Lee may kick up trapped sediments behind the Conowingo, as it did three years ago (dropping nearly seven inches of rain in a 3-hour period at one point), but the impact of storm-related erosion and runoff upriver or elsewhere across the bay is four times worse, an important point made by the study's authors.

Exelon shouldn't be left off the hook, but no one who pollutes the Chesapeake Bay and its tributaries should either. It's disappointing that Mr. Hogan's initial reaction to the study is to doubt its accuracy while acknowledging he hadn't actually read it. The corps is no Greenpeace. Historically, it's an organization that has not exactly shied away from dredging. Bay restoration efforts ought to be guided by science, not by the politics of blame-shifting.

Mr. Hogan may not have campaigned for office as a pollution-fighting crusader, but he also said he shares his fellow Marylanders' desire for a cleaner Chesapeake Bay. Achieving that requires making tough choices that are often unpopular with one group or other. Whether the incoming governor understands that challenge is not altogether clear.

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