Last week when Herbert Sachs, Maryland's representative on the Susquehanna River Basin Commission, said the problem of silt build-up behind Conowingo Dam had been discussed for years, but nothing had been done about it, he was spot on.

The inaction over well in excess of a decade means the reality of a substantial ecological disaster is looming large. The kind of disaster risked by leaving the mess of sediment behind Conowingo Dam isn't the sort of thing that would cost human lives, but it is the kind of thing that is bound to change life along the Chesapeake Bay. It's also the kind of disaster we've experienced before. It's been nearly 40 years since Hurricane Agnes caused a massive Susquehanna River flood that scoured silt and sand from the river and dumped it on the Susquehanna Flats and upper Chesapeake Bay.

In the aftermath of that catastrophe, once massive flocks of canvasback ducks ceased to frequent the region. This is believed to have been a direct result of the storm's effect on the Flats.

Populations of other iconic wildlife in the upper bay region also bottomed out within a few years of the Agnes disaster on the Flats. Rockfish, for which the upper bay is a major spawning grounds for the entire Atlantic seaboard, were nearly wiped out. The Susquehanna run of American shad, once abundant to the point of being used as fertilizer, was nearly wiped out. Oysters, a mainstay of the Chesapeake fishing industry for generations, fell prey to parasites.

While rockfish have been managed into a state of recovery, shad remain strictly protected, and oysters, well there's a remnant population, but little more.

Though no direct link has been established between the demise of rockfish, shad and oysters to the Agnes storm and resulting silt surge, and other factors clearly were at play, the timing is more than a little curious.

What's happened at Conowingo Dam is the same thing that can be seen behind just about any smaller dam, be it Eden Mill, Atkisson Reservoir or any number of old impoundments across creeks and streams across the state and country. Silt and debris build up behind the dam, making the lake shallow.

If a dam breaks, or a major storm floods the creek, decades worth of silt is washed downstream, clogging the waterway.

The difference at Conowingo is size, and the threat is to Maryland's defining natural resource, the Chesapeake Bay.

So who is responsible for the mess? Typically, the person who made the mess is obliged to clean it up. In this case, the owners of Conowingo Dam — these days it's the property of energy giant Exelon — should be obliged to deal with the problem. Granted, when Conowingo Dam was built about 80 years ago, it's possible no one foresaw the silt problem. But ignorance is no excuse. Just as the owners of the dam, regardless of their corporate name over the decades, have had to clear the tons of flotsam that accumulates behind the dam after each spring flood, they also should be responsible for dealing with the tons of sediment held back by the dam.

While it's in the interest of the dam's owners to clear the flotsam each spring, or risk clogging generator intakes, failing to clear silt isn't necessarily an immediate threat to the generation of power.

Because it is, however, a threat to the Chesapeake and those who derive their livings and leisure from it, it will fall probably to the Federal Energy Regulatory Commission to hold Exelon responsible for dealing with the silt. FERC issued Exelon a license to operate the dam and that license comes up for renewal on Sept. 1, 2014. If action is to be taken to deal with the silt threat looming behind Conowingo Dam, now is the time.

Failure to act before the dam permit is renewed will effectively mean the silt will remain in place until it is washed into the Chesapeake by the next Agnes-strength storm.