The federal agency responsible for licensing the Conowingo Dam stated that major new investments are needed at the facility to help fish get up the Susquehanna River, but expressed skepticism that dam owners should be required to dredge sediments that have built up behind the 100-foot structure.

The Federal Energy Regulatory Commission issued a draft Environmental Impact Statement July 30 that summarizes key environmental issues stemming from the dam’s operation and how FERC staff believes those problems should be addressed in a new license for the facility.

FERC is taking comments on the draft EIS until Sept. 29. The EIS also addresses relicensing at the upstream York Haven Dam and the Muddy Run Pumped Storage project.

But the most controversial issues rest with the Conowingo Dam, the largest dam on the lower Susquehanna, which is located just 10 miles upstream from the Bay.

Its current 30-year operating license was to have expired Sept. 1, but FERC was widely expected to issue a one-year extension to Exelon, which owns the dam, while final issues are resolved for the new license, which could be for as long as 46 years.

The most controversial issue involved in the relicensing is what to do about sediment that has been accumulating behind the dam since it was completed in 1928. Studies show that the 14-mile reservoir behind the dam is reaching its capacity to hold sediment coming down the Susquehanna. As it nears capacity, more sediment and phosphorus could be transported to the Bay.

FERC staff generally endorsed Exelon’s sediment plan, which primarily calls for managing only sediment that affects dam operation and to conduct detailed surveys every five years to monitor sediment accumulations behind the dam.

But, FERC staff said recommendations in its final EIS could be influenced by an ongoing study of lower Susquehanna River sediment management options being undertaken by the Army Corps of Engineers, a draft of which is expected by early fall.

FERC’s recommendations fell short of the request of several organizations that it require a large-scale dredging of sediment from behind the dam. Commission staff said such an operation would be “challenging and complicated” and that it was “premature” to conclude that dredging would be an environmentally acceptable solution. Exelon has said dredging could cost $50 million a year just to keep pace with the rate of new deposition in the reservoir.

FERC said other proposals for structural or operational changes at the dam to manage sediment were not viable solutions at this time.

Resolving the sediment storage issue, FERC said, would likely require actions that address sources of sediment beyond the dam. “…the ultimate resolution of this issue would require more than singular actions at [Conowingo Dam], and instead would require a basinwide approach involving many governmental jurisdictions and other entities.”

On the issue of fish passage, FERC staff recommended that Exelon make greater investments in fish passages than it had proposed — but less than requested by resource agencies.
Construction of the dam closed the Susquehanna, the largest East Coast spawning grounds for shad and river herring, to upstream fish migration.

A fish elevator was opened at Conowingo in 1991 to lift American shad and river herring over the dam, but it was never as effective as biologists had hoped. Migration is further hampered by three upstream dams; few fish make it past all of them in a typical year. Only eight American shad made it past all four this year.

Citing those problems, FERC calls for reviving a program to capture American shad below Conowingo and trucking them around all four hydroelectric dams on the lower Susquehanna. Such a program was in place before fish passages were built on the dams — and actually was more successful in getting fish upstream than the passages.

But it also recommends a series of upgrades aimed at improving the effectiveness of the fish passage at Conowingo, including expanding the capacity of the fish lift at the dam and altering the flow of water near the lift to better attract migrating fish.

It did not seek changes as extensive as those requested by state and federal resource agencies, though. Nor did it include the recommendation of those agencies that the fish lift have an operational goal of passing 85 percent of the shad at the dam — FERC staff said they could find no scientific basis for that goal.

On another fish passage issue, FERC endorsed a plan to capture American eels at the dam and truck them beyond upstream dams for release. That operation would continue at least through 2030, when eel passages are to be completed at the dam, though FERC said the option should be left open to continue the truck-and-transport program beyond that date.

It also said that Exelon should monitor the survival rate for eels migrating downstream past the dam. If 85 percent of eels do not survive movement past the dam turbines, it said a program should be established to capture and truck eels downstream as well.

On other issues, the draft EIS suggested tweaks to the minimum downstream water flows that are required at the dam to maintain downstream habitats.

It also recommends actions be taken to protect habitat for rare map turtles, which nest downstream, and that a new bald eagle management plan be implemented that includes buffers around eagle foraging and nesting areas. It also calls for Exelon to develop and implement a plan to protect waterfowl nesting in the vicinity of the dam.

FERC also endorsed a number of upgrades to recreational facilities that were proposed by Exelon, and also called for dredging to maintain three upstream boating access sites.

Commission staff also suggested reopening the catwalk immediately below the dam to anglers, at least on a limited basis. The catwalk was a popular fishing site, but was closed by Exelon in October 2001, which cited security concerns. FERC suggested the catwalk could be reopened on a limited basis, with stepped-up security at minimal cost and that it would provide “exceptional angling opportunities.”

The full draft Environmental Impact Statement, which is nearly 600 pages, can be found here

FERC is taking public comments on the draft EIS through Sept. 29. In addition, it has scheduled three public meetings to solicit comments:

  • 10 a.m. Sept. 16, Darlington Fire Station, 2600 Castleton Road, Darlington, MD
  • 6 p.m. Sept. 16, Darlington Fire Station, 2600 Castleton Road, Darlington, MD
  • 6 p.m. Sept. 17, Holiday Inn Harrisburg East 4751 Lindle Road, Harrisburg, PA

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