Trustees Hear Update on Three Flood Mitigation Projects

The results are in! The hydraulic modeling analysis to determine if Cayuga Pond modifications are needed to the opening of the pond (to improve storm water drainage) is complete and has returned positive results.

This and other Sheldrake River Basin project updates were detailed by Vice President Robert DeGiorgio of Dvirka and Bartilucci Engineers (D&B) to the Scarsdale Village Trustees during the December 4 Scarsdale Village Municipal Services Committee Meeting.

In addition, D&B determined that:

• The combination of refining the Cayuga Pond outlets and adding overflow drainage pipes to balance flows does provide improved flood mitigation up to and including 100 year flood events.
• There has been a reduction in flood elevations in the P-designated (critical) areas varying from 7 to 5 inches of rain.
• There has been successful removal of accumulated silt and debris from the pond, creating additional storage in the pond, which allows for the collection of three million gallons of water.

D&B is working to convert Cayuga Pond from a recreational pond into a storm water detention basin to allow the pond to retain water during heavy downfalls and release it slowly over time. In addition they are improving the culverts (drain pipes that allow water to flow under roads) on Cayuga and Canterbury Roads. This will allow for better water flow and balance through the piping systems.

The Village first retained D&B in 2004 following a Storm Water Drainage Condition Survey. They were asked to address storm water issues in the Sheldrake River Basin, which extends from Cushman and Sheldrake Roads to the Fenway Golf Course flowing down to the Scarsdale Middle School, onto the Scarsdale Medical Center and into New Rochelle.

In order to mitigate flooding upstream, D&B formulated the 2009 Comprehensive Storm Water Management Plan, which proposed certain modifications to the current drainage structure. The modifications primarily focused on improving the Sheldrake River Drainage Basin and reducing excessive water runoffs during heavy storms that have caused devastating flooding for Scarsdale residents who live in the area.

Earlier this year, the Village Board formed a working group including Board members, residents, Village staff and the Village's consulting engineer from Dvirka and Bartilucci (D&B). Based on discussions amongst this working group at a May 14 meeting, D&B revised the project scope to include six major tasks:

1. Hydraulic analysis of modified Cayuga Pond outlet structure to determine if modifications are needed to be made to the existing orifice opening.
2. Clean the culvert under Oneida Road
3. Construction of new culvert crossings at Cayuga Road and Canterbury Road that will eliminate the road infrastructure and provide open gratings to allow for additional flow capacity.
4. Construction of a connector pipe to open the channel on the south side of Canterbury Road to help balance the current flow and allow it to continue downstream.
5. Removal of accumulated silt throughout the open watercourse that abuts the properties of 6 Cayuga Road and 14 and 18 Canterbury Road.
6. Perform hydraulic modeling of these improvements to determine if they would result in any negative impacts downstream.

Subsequently, the Board appropriated $600,000 from the General Fund for D&B to design the Sheldrake River Drainage Basin Modified project at its August 13 meeting based on D&B's estimated project cost of $400,000 - $650,000.

Several residents were in attendance at the meeting and were visibly upset. They reiterated their concern that their properties continue to flood during harsh storms. One resident asked why D&B wasn't "talking about digging down further in the Pond to clear water faster from the neighborhoods," to which DeGiorgio answered that digging deeper won't help because it's "dead storage." Another concerned resident wanted to know if they could break up the concrete and do more plantings to absorb more water near the middle school. This is also not a possibility because the area is owned by the Scarsdale Schools and the water table in that area cannot accommodate additional water.

Next Steps for D&B:
• Meet with NYSDEC
• Determine dam permit needs
• Develop design

Project Schedule:
• Secure design/permits: 6/13 – 12/13
• Bidding/permits: 1/14 – 3/14
• Construction: 5/14 – 12/14

Update on South Fox Meadow Storm Water Improvement Project

The detention basins at George Field Park and Cooper Green have mitigated flooding along the South Fox Meadow Brook. Additionally, the 2,900 square foot rain garden at Cooper Green and the rehabilitated wetland at George Field Park have worked to filter and clean storm water runoff.

Construction on the final segment of this project, Harcourt Woods, started on Monday, December 2. The project has been revised to address concerns that were expressed at the Village Board's Municipal Services Committee meeting on June 5. Namely, the scope of work has been modified regarding the removal, protection and planting of trees, reduction of the size and location of the maintenance path and alternatives to drainage diversion along Brewster Road. The Village has written a Change Order that addresses these modifications and enhances the project by including additional "green" features, such as the construction of a vegetated swale along Brewster Road in front of the gravel parking lot. The Change Order also resulted in a saving of $37,224 to Scarsdale, as the project cost was reduced from $760,900 to $723,676. Most of the work in the Harcourt Woods Project is scheduled for completion in September of 2014.

Scarsdale Public Library Rain Garden Project Update

The Village developed a grant proposal for a storm water runoff reduction and water quality treatment project at the Scarsdale Public Library for an estimated cost of $247,091. The project involves the construction of a 1,800 square foot rain garden at the Library allowing for 90% of the storm water run-off from the library's roof (approximately 450,000 gallons) to infiltrate into the ground. The Village was awarded a grant for $188,091.50 by the National Fish and Wildlife Foundation with the $59,000 balance being funded through a Village match via $26,100 in cash and $32,900 of in-kind services. The Village Board authorized a professional services agreement with D&B for a total cost of $24,600 for design, engineering and construction management services at its August 13, 2013 meeting.

Tracie Kurland works as a Marketing Communications Specialist and Professional Outreach Coordinator in Scarsdale and resides in Irvington, NY. She is a passionate writer and often twilights as a freelance reporter. Follow her Politically Purple Blog here.