By Kathryn G. Menu
The Sag Harbor Village Board of Trustees was formally presented last Thursday with drainage solutions for four problem areas often flooded after heavy rains. The board fell short of endorsing any of the specific plans in the lengthy report, created by Dvirka and Bartilucci Consulting Engineers at their request, with Trustee Robby Stein stating he believes addressing flooding issues in Sag Harbor Village will be a task that falls not only on the shoulders of local government, but also on individual homeowners.
Steven Cabrera and Jason Tunney, both from D & B, gave a presentation to the board last Thursday, outlining potential—and often costly—solutions for flooding on Rogers Street between Latham and Henry streets, Hempstead Street near the intersection with Liberty Street, the intersection of Spring and Garden streets and in Redwood.
Eventually, said Mr. Cabrera, the goal of the report is to give the village a document with which to base final engineering plans to contend with drainage in Sag Harbor.
Mr. Tunney explained that when looking at each neighborhood, engineers analyzed the watershed, existing drainage structures and impervious surfaces. The report makes recommendations for creating a drainage system capable of handling water created in a 10-year storm.
A 10-year storm would bring five inches of water in a 24-hour period, according to the New York State Stormwater Design Manual. By contrast, a two-year storm event would bring about 3.5 inches or water during a 24-hour period and a 100-year storm would bring 7.5 inches of water over a 24-hour period. Last September, Sag Harbor was hit with a storm that brought approximately 6.25 inches of rain in just a few hours, falling just above the 25-year storm rainfall amount of 6 inches.
“Some of the pipe systems found here were insufficiently sized,” said Mr. Tunney, although he noted that alone would not cause flooding in a neighborhood.
When it comes to Rogers Street, said Mr. Tunney, the neighborhood has a watershed of 26.5-acres without much of a drainage system in place. Water flows into the neighborhood and into a catch basin that he noted is only equipped to handle about 28,000 cubic feet of water when 45,000 cubic feet of water is what would be expected to drain into the basin during a two-year storm. The basin, said Mr. Tunney, would have to be enlarged five times its current size to be able to handle the amount of water coming into Rogers Street. Without buying adjacent properties, he said, there is no way to expand the basin.
Mr. Tunney outlined several options for the board, including buying adjacent properties for expansion. Another option is spending $1 million on the installation of 100 drywells throughout the Rogers Street watershed. Yet another involves creating a pump station leading to a gravity fed pipe discharging into Sag Harbor Bay.
“These are not easy options,” said Mr. Tunney, noting there are not a lot of viable options available.
Mr. Tunney noted the Havens Beach tributary area, which affects flooding on Hempstead Street, is 133 acres. Tidal conditions and the beach itself also affect the potential for flooding in the drainage ditch at Havens Beach.
He suggested adding a new catch basin on Hempstead Street and increasing the size of the existing 18-inch storm drain with a 30-inch storm drain to the drainage ditch to ease flooding concerns. He added the village could also install an emergency overflow release for particularly heavy rainfalls. The total cost of those improvements would be $125,000.
Addressing drainage at Spring and Garden streets can be accomplished by replacing the existing system with larger pipes, said Mr. Tunney. That would cost $500,000. He said the pump capacity at a West Water Street pump station should also be increased to handle peak flows of water from the entire 39-acre watershed that feeds into Spring and Garden streets and over to West Water Street, which would require an additional pump station at a cost of $350,000.
In Redwood, Mr. Tunney recommends the construction of three catch basins—at $15,000 a piece—to address three trouble areas.
Mr. Stein noted that the D & B report did not look at water containment on individual properties, which could have a tremendous impact on stormwater runoff in the village.
“On our books we have laws about containment,” said Mr. Stein, noting projects are required to contain their own runoff.
“I am going to take an unpopular position here which is on new construction we have to enforce people to containing the runoff on their property,” he said, noting there are sections of Sag Harbor that are actually below sea level.
“Basically what you are saying is the residents themselves can do a lot to help,” said Mayor Brian Gilbride.
Yes, said Mr. Stein, adding the village could also look to create wetlands systems and other creative solutions outside of infrastructure to address drainage. Creating an educational wetland in an area like the Cilli Farm was one idea Trustee Stein supported.
“I just think we as a board need to have a comprehensive plan that includes enforcing what we already have on the books … and then look at some of the open areas we have for drainage, not just the bay,” he said.
“Those are valid points and should be considered,” said Mr. Tunney. “Every little drop will help.”
Noyac resident and former East Hampton Town Natural Resources director Larry Penny agreed a long-range plan was necessary, particularly with sea levels rising, he said.
Mayor Gilbride agreed, and said he believed if property owners helped contain runoff on their own properties and more catch basins were added in larger watersheds, it would be a good start.
Anton Hagen, the chairman of the village zoning board of appeals, wondered what impact swimming pools have on stormwater runoff. Mr. Tunney said there are conflicting schools of thought on the impact pools have on runoff, although he agreed the size and depth of the pool can impact groundwater.
ZBA member Brendan Skislock added it would be helpful for the village to require an analysis of drainage on any property coming before the ZBA for variances.
“To any of the boards, take a closer look and when any board is looking at plans the questions should come up about how do you address rainfall,” said Mr. Gilbride.