Flood Mitigation Projects Planned

STONE HARBOR – Stone Harbor Borough Council discussed major projects June 16 that are a part of the big picture response to flooding and rising seas.
One effort involved the construction of a stormwater pump station at 93rd Street, which comes with an estimated price tag of $11 million. Another is a set of changes to the borough’s lot grading ordinance. If adopted, the ordinance changes would drive private property owners to meet specifications that would facilitate an eventual borough action to raise streets to 6 or 6.5 feet.
Both are part of what Councilmember Charles Krafczek called the “big picture” response to the increasing threat of higher sea levels, large rain events, and more frequent major storms. Krafczek added recent borough moves to his discussion to set top of block elevations for construction at 11 feet and the multi-year phase-in of a new bulkhead mandate of 8 feet. He said the efforts would put the borough ahead of the curve concerning long-range vulnerabilities.
Pump Station
The presentation on the 93rd Street stormwater pump station was made by Thomas Thornton, of Mott MacDonald. The engineering firm is leading a new drainage and pump station effort for neighboring Avalon.
Thornton said the design criteria for the Stone Harbor pump station project is that the borough would experience no flooding during a five-year storm and some intersection flooding, but no property damage from a 10-year storm. The drainage area for the pump station will be 88th Street to 99th Street and just about every location west of Second Avenue.
The design, now 60% complete, calls for three pumps at the station, two large and one small, capable of moving 80 million gallons of water per day. The station will include a screening chamber to separate solids from the stormwater before it makes its way down 93rd Street to an outfall through the bulkhead into the bay. Thornton indicated that another outfall may be needed near 96th Street and Third Avenue.
The project grew out of 2016 recommendations from the borough’s flood mitigation committee. The first engineering firm hired by the city was dismissed from the project. Mott MacDonald was hired to do a peer review of the work to-date and took over design of the project about a year ago.
The goal is to complete the design effort and bidding process in time to make an award by January 2021, with substantial completion of the project by September 2022. Thornton said Mott MacDonald was ready to begin the permit application process next month (July 2020).
The cost estimate is based on the 60% complete design and could change as the design is finalized. The borough will not be stuck with the full tab. A grant from the state Department of Environmental Protection is expected to cover $2.6 million. 
The county will be involved in the project, as well, given that Third Avenue is a county road. Thornton estimated the potential county contribution at $3.9 million. If all the estimates hold, the bill to the borough should be around $4.5 million.
Flows from First and Second avenues are not part of the design. The project from its initiation was focused on the most troublesome areas of flooding.
Lot Grading Ordinance
Many of the proposed changes to the lot grading ordinance also originated with the borough’s flood mitigation committee. Planning Board Engineer Paul Kates listed five areas of suggested changes to the existing ordinance. 
They included a 15% reduction in the amount of permitted impervious coverage, requiring grade plans as part of site plan approval submissions, and raising lot grade levels. There was also a discussion of possible limits on what materials could be used for retaining walls.
The concept of raising minimum grade elevations was discussed as directly related to a later effort by the borough to raise streets in low-lying areas. It was suggested that raising streets to 6 or 6.5 feet will probably be a “heavily recommended flood mitigation technique” in future master plan recommendations.
The picture created from the discussion was of a newly constructed home at higher elevations, with 8-foot bulkheads and increased grade for the entire lot that would leave 6- or 6.5-foot grade level at the street front of the property. Road elevations would follow.
Curb to Sidewalk Irrigation
A related issue in the discussion was the Planning Board’s proposal that would limit the type of irrigation allowed for vegetation between the curb and the sidewalk. Here, the Planning Board and the flood mitigation committee set aside their partnership on other issues. The flood mitigation committee, according to Council President Joselyn Rich, is pushing for the elimination of any vegetation in the area of a residential property.
Rich said the goal was to conserve water which is frequently wasted, as irrigation of these small areas tends to result in large amounts of water being pushed out into the street. The heavy use of water, in July and August, necessitates efforts to conserve, Rich said.
Krafczek countered that an acceptable compromise might be reached if the borough allowed drip irrigation systems from the curb to the sidewalk, reducing water waste and still allowing homeowners to engage in reasonable landscaping plans that included vegetation in that area of the property.
The discussion did not result in any consensus position at this time.
To contact Vince Conti, email vconti@cmcherald.com.