How to Defuse a Water Quality Time Bomb?

Tropical Storm Lee stirred up about four million tons of sediment that had been trapped behind the Conowingo Dam and in the lower Susquehanna River and flushed this pollution into Chesapeake Bay, according to the Maryland Department of the Environment.

The result of the storm was a huge brown stain on the Bay that could be seen in NASA satellite photos running nearly the length of Maryland.

As startling as that figure of four million tons may sound, it could get worse in the future, the state agency warns. The Susquehanna River is the largest source of fresh water to the Bay. And the massive Conowingo hydroelectric dam in northeastern Maryland has been trapping about two thirds of the dirt, sand, and fine particles (sediment) mixed with other pollutants (including nitrogen and phosphorus) that flows down the river from Pennsylvania and New York toward the Bay.

However, the reservoir behind the dam is filling up with this muck, and dam’s capacity to store more sediment will be exceeded in 15 to 20 years, according to the Maryland Department of the Environment. After that, storms could stir up huge increases in sediment gushing into the Bay.

That makes the Conowingo a time bomb for water quality.

“Tropical Storm Lee provided a vivid demonstration of the need to take steps to head off what could be a catastrophic event causing immediate and enormous damage to our (Bay) restoration processes,” Governor Martin O’Malley said in a press release.

To figure out a way to solve this problem, O’Malley and the Army Corps of Engineers this week announced the launch of a three-year study to examine potential strategies for defusing the time bomb.

Teaming up in the study will be experts from Maryland’s environmental and natural resources departments, the Army Corps of Engineers, the Susquehanna River Basin Commission, and the Nature Conservancy.

“The sediment behind that dam is waiting to be released in a big punch by the next big rain storm, and we have to find a way to deal with it,” said Mark Bryer, Director of The Nature Conservancy’s Chesapeake Bay Program.

In a blog article yesterday, Bryer, who is part of the sediment study team, described the importance of the issue for efforts to impose a pollution “diet” on the Bay.  The Bay pollution “diet,” or Total Maximum Daily Load (TMDL), is a set of pollution limits created by EPA in December with a goal of reducing the amount of pollution entering into the Bay by about 25 percent by 2025.

The "diet" calls for no more than one million tons of sediment a year flowing from the Susquehanna River into the Chesapeake bay. But this limit was exceeded in a few days by a single rainstorm, Tropical Storm Lee.

“Just as this ‘diet’ is being adopted, the remnants of Lee may end up being a trip to the all-you-can-eat buffet for the Chesapeake Bay,” Bryer wrote on the blog. “This massive flow of water is not only carrying trash and debris with it, but also pollution in huge quantities.”

The issue, however, is not as simple as it may sound. Not all sediment is bad for the Susquehanna River or Chesapeake Bay, Bryer noted.  Some species of fish require pebbles and sand to lay their eggs successfully.  But this heavier sediment is being trapped behind the Conowingo and other dams on the Susquehanna River, depriving fish downstream habitat they need to reproduce, Bryer said.

Meanwhile, lighter sediment (made up of fine particles) is being washed downstream, which muddies the water, blocking light, killing aquatic vegetation, and smothering oyster beds.

So part of a solution for managing the Susquehanna River might involve allowing some heavier sediment to pass through the Conowingo and other dams at appropriate times of the year to encourage the reproduction of fish, Bryer said.

It will be a complex and difficult management task, but one that is critical for the health of the Bay and its largest tributary.

By Tom Pelton

Chesapeake Bay Foundation

(Photo at top by U.S. Geological Survey)

 

Comments

[Waddell Robey]

Sediment filtering would be a very constructive effort for the Bsy's good health, but it is vitally important that whatever process is developed that it also finds ways to decrease flooding impact by the Susquehanna along its entire watershed. We gain little if we solve one problem and create more serious problems along the way.

Actually the entire Bay watershed system needs to be carefully examined with respect to severe storms such as TS Lee. We will have others in the future. Greater cooperation by metro areas along all the watersheds will be critical for both the TMDL target and sedimentation pollution. Right now that cooperation is an uncontrolled variable. I live in Harrisburg, and I know the city government is not proactive on controlling what gets dumped or flows into the river. I think this is not unique and represents the general reaction throughout the Bay watershed.

I summarized much of this in my latest blog article: A Lady In Distress: Technology To The Rescue. http://tinyurl.com/3eqzcz3

[Tom Pelton]

A brilliant blog article, Waddell! You are a fine writer.

To everyone out there, I recommend his blog
"My Chessie Affair: An Eternal Love Story," which you can find at:

http://baylines.wordpress.com/

[Mike Lurz]

Any measure that will help with this issue will be a tremendous undertaking. A good start though would e uniform and binding measures that apply to all, regardless of who your political friends are, how much you are willing to pay or any other consideration. Pollution doesn't know or care who you are, therefore any measure designed to combat it must be equally applicable, across the board

[קידום אתרי אינטרנט]

The Susquehanna River is the main source of freshwater in the bay and the massive Conowingo hydroelectric dam in northern Maryland was trapping about two-thirds of dirt.