by Chris Trumbauer
If you travel up the Chesapeake Bay far enough, you will find the Conowingo Dam on the Susquehanna River, near the Maryland/Pennsylvania border. “Conowingo” is a Native American word that means “at the rapids” and the dam is located at the site of the first rapids one would encounter when heading up the river from the Bay. Completed in 1928, the dam is currently owned and operated by Exelon, and is one of the largest hydro-electric dams in the country, not owned by the federal government.
A lot of water flows over the dam – and by a lot I mean a daily average of nearly 42,000 cubic feet per second. The Susquehanna supplies about 50% of the freshwater input to the Chesapeake Bay. The West and Rhode Rivers are tidal, and their water quality is significantly influenced by the water in the Bay. So, as you might expect, there is a link between the Susquehanna River water coming through the Conowingo, and the health of the West and Rhode Rivers. Studies by the Smithsonian Environmental Research Center on the Rhode River demonstrate this, but you can also see it on satellite imagery after a major rainfall – when a visible sediment plume reaches our area from Conowingo.
Over the course of its life, the Conowingo Dam has trapped nearly 200 million tons of sediment behind it. This sediment consists of 85 years worth of upstream runoff, including everything from farm fields and construction sites to residential lands. The ability of the dam to store any more sediment is almost done – its just about full. What happens then?
When the dam can no longer store sediment, it (the sediment) will simply continue down the river and into the Bay. More importantly, during a tropical storm or other large rain event, the raging river flow through the dam‘s flood gates can scour the sediment stored behind the dam. This can, as in 1972 with Hurricane Agnes, deliver a catastrophic amount of sediment to the Bay – far more than there would be in a big storm if the dam was not there. When too much sediment enters the Bay, it clouds the water, and impacts natural resources like oysters and underwater grasses. The nutrient pollution that accompanies the sediment will cause algae blooms and dead zones.
How do we stop this from happening? There is no easy answer, but we must address this situation before its too late. One opportunity involves the once-in-a-generation relicensing of the Conowingo by the Federal Energy Regulatory Commission (FERC). The current license was issued in 1980 and is due to expire in 2014. Exelon has applied for a 46-year license to continue operating the dam.
Our partner, the Lower Susquehanna Riverkeeper, has been working on this issue since 2006 and participating in the relicensing process since 2009. They asked West/Rhode Riverkeeper to join them in this effort. As part of the Waterkeepers Chesapeake coalition, we have petitioned to be included in the relicensing proceedings. We believe that Exelon should share in the responsibility for cleaning up the millions of tons of sediment trapped behind their dam. The fact is that if the dam was not there, then the unnatural accumulation of sediment behind the dam would not exist. The State of Maryland has the authority to require certain conditions to grant a new FERC license, and we are urging them to use this opportunity to maximize our efforts to remove this sediment.
Some in Maryland are pointing to Conowingo as an excuse not to implement local measures to reduce stormwater pollution. Their reasoning goes something like this: “If the Susquehanna River is putting so much pollution into the Bay, whatever we do locally won’t make a difference.” That is simply untrue. While flow from the Susquehanna certainly is a major driver of water quality in the main stem of the Bay, just cleaning up the Susquehanna will not heal the Bay. Additionally, the local impacts are far more important to our rivers, creeks, and streams. Local stormwater runoff from developed areas and farm fields, and failing septic systems are what is responsible for our high bacteria levels and water contact advisories.
Let’s not use Conowingo as an excuse – let’s use it as an opportunity. Here is a chance to act that won’t come around again for 46 years. If we can require Exelon to remove at least some of the sediment from behind Conowingo, and reduce the threat of a catastrophic event, we can enhance and secure our local efforts to reduce pollution and improve water quality. Addressing all sources of pollution is the only way we can make true progress in our fight for clean water.