By Jess LevensonDecember 22, 2019
The Mount Morris Dam, situated deep in the Genesee River gorge near the northern end of Letchworth State Park in Livingston County, NY, has been very effective at reducing the risk of flooding for downstream communities since it was built in 1952. In fact, to date, the dam has prevented over $3 billion worth of flood damages. The U.S. Army Corps of Engineers Buffalo District is responsible for maintaining the dam so that it continues to perform this valuable flood risk reduction mission.
One significant annual maintenance effort includes the removal of debris and sediment that accumulates on the upstream side of the dam in order to prevent conduits (tunnels where water is passed through the dam) from becoming clogged. While necessary, this annual debris removal process uses up precious maintenance dollars, and USACE is continuously looking for ways to operate more efficiently.
Paul Cocca, Buffalo District Hydraulics and Hydrology Engineering Team Lead, observed the annual debris removal process in the spring of 2017 and wondered if there was some way to reduce the sediment removal effort while still maintaining continuous operability through some structural or operational measure.
At Cocca's recommendation, a team was set up to further investigate opportunities to reduce the amount of sediment removed during Mount Morris Dam's annual debris removal effort. Joshua Feldmann, Chief, Operations Branch, and Adam Hamm, Chief, NY-PA Operations and Maintenance, supported and funded the investigation effort. Cocca and Tom Arcuri, Hydraulic Engineer, proposed a series of potential options to the operations team members who oversee debris removal efforts. Operations team members that provided feedback on the numerous options included Steve Winslow, Mount Morris Dam Manager, and Hamm.
After evaluating several possibilities, the team decided to try out a plan that facilitated more natural scouring by raising and lowering sluice gates at specific times in order to leverage natural flow-rates of the river.
The plan involved much less sediment removal, and actually resulted in greater sediment deposition close to the dam, but still allowed for a "natural" channel to be sustained along the front of the dam. The idea was that this smaller open channel would allow for continued operability of sluice gates throughout the year. The team coordinated with Keith Koralewski, Chief, Hydraulics and Hydrology and Water Management Section, to make sure that new gate settings for sediment management during low pool conditions did not interfere with flood risk management operations, and that any changes to gate settings would be done in coordination with Water Management.
Operations team members Dave Mastriano, Civil Engineer, and Brian Dockstader, Engineer, figured out how to implement the solution under an existing contract, resulting in reduced sediment removal along the face of the dam as well as modified gate operations during periods of naturally low river flow to encourage more effective channel scouring.
The plan has been implemented for two years, and has been considered successful thus far in terms of reduced quantity of sediment removed (e.g. cost savings) with no detrimental impact to dam functionality.
Although the amount of sediment deposition that occurs at the face of the dam fluctuates each year depending on a number of variables, USACE was previously removing around 5,000 to 8,000 cubic yards of sediment each summer. In Fiscal Year 2019, USACE removed only 500 cubic yards of sediment.
The Buffalo District Operations Branch plans to continue to implement a reduced sediment removal plan in FY20 and beyond, acknowledging that during some years, additional mechanical sediment removal may be required in order to access floating debris lodged in the scour channel. Ultimately, fewer federal dollars will be spent removing sediment at Mount Morris Dam thanks to some innovative thinking, good teamwork, and willingness to try a new strategy.