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baltimoresun.com

Dam silt needs to be addressed [Editorial]

2:32 PM EDT, May 8, 2014

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The silt that has built up in the slack water on the upriver side of the Conowingo Dam may well be, as an Army Corps of Engineers official reported at a U.S. Senate hearing on Monday, a lesser pollution threat to the Chesapeake Bay than runoff fouled with road crud and agricultural wastes, but that doesn't mean it's not a problem.

The federal government is in the midst of a once-every-few-decades process of reviewing the permits under which the owners of the dam are allowed to continue blocking the Susquehanna River for the purpose of generating electricity. The last time the permits were up for renewal, the dam's owners were obliged to make provisions to ensure migrating shad, eels and other fish be allowed access to parts of the river once open to them. Going back to the early 1800s, migrations of American shad made it as far up the Susquehanna as Binghamton, N.Y. The run of ocean fish was substantial enough in central Pennsylvania's Wyoming Valley that settlers from Connecticut moved to the area, resulting in a territorial dispute between the two then-colonies.

When the subject of requiring fish passage facilities at Conowingo and other upriver dams was being considered, questions were raised about the viability of a fish run restoration effort. Would the cost of requiring fish passage facilities at Conowingo be justified, given there were no guarantees the shad run could be restored? The decision was made to require the fish passage as a condition of the federal license renewal. Decades later, it remains to be seen if the restoration effort will be successful, but in the years since the large fish lift at Conowingo was built in 1991, one thing has changed: American shad are regularly making the journey up at least as far as York Haven, which is about two thirds of the way upriver between Conowingo and Harrisburg.

For the past several years, the subject of whether the owners of Conowingo Dam should be obliged to dredge the massive amount of collected silt from where it has collected upriver from the dam has been a matter of discussion relating to the current permit renewal process. The question boils down to: Should the area behind the dam be dredged as a condition for permit renewal?

Col. J. Richard Jordan III, commander of the Baltimore District of the Army Corps of Engineers, speaking at a hearing Monday held at the dam, said a recent study concluded the sediment washed into the Chesapeake during the 2011 Tropical Storm Lee included about 20 percent material that had collected behind the dam, with the balance coming from other runoff.

He went on to note, according to a Baltimore Sun report of the hearing, that requiring a dredging of the material behind the dam could cost from hundreds of millions to as much as $3 billion, even as he estimated the potential benefit could turn out to be minimal.

The colonel makes a strong point when he notes that the greater portion of pollution threatening the Chesapeake comes from farther upriver than the short section above Conowingo Dam. Absolutely, this pollution needs to be dealt with.

But the pollution coming from upriver from the Conowingo Pond, as it is sometimes called, is not what's being considered for permitting; the pollution resulting from material held back by the dam is. Furthermore, it is a rather huge amount of silt. While it constituted 20 percent of what was washed down by the major flooding caused by Lee, the area behind the dam constitutes maybe two dozen square miles of river bottom, while the Susquehanna basin is 27,510 square miles. That 20 percent of silt pollution from a major flood could come from such a tiny fraction of the river's drainage area is fairly significant.

As long as Conowingo Dam remains a viable part of the power grid for the region, there is good reason for it to be granted permits to continue operating; however, the costs associated with generating that power must be extended to include making provisions to mitigate environmental damage. In the case of the silt trapped behind the dam being washed into the Chesapeake Bay in massive slugs during major flooding, the damage done is substantial. Arguably, the fallout from the Lee storm could have been reduced by 20 percent had the silt been cleared out prior to 2011.

Given that the permit granted will be good for decades before another chance will arise to require silt dredging or some other kind of remediation, the federal government should require some sort of silt management regimen – or even a full scale dredging — as a condition of renewing the Conowingo permit, Col. Jordan's diagnosis of the situation notwithstanding.