Residents Grill Developer's Expert About Flooding
Retention and detention systems, elevations, and the impact of impervious surface area on flooding with the proposed development of the United Water property.
In addition to questioning the developer's expert on affordable housing, Thursday's special meeting of the zoning board also gave residents the opportunity to question the developer's engineering expert, Michael Dipple.
Dipple, an engineer and principal of L2A Land Design in Englewood, had previously testified about the water detention and infiltration systems that will be installed as part of the proposed development of the United Water property.
On the forefront of the mind of every resident in attendance was the impact that the impervious surface area of the proposed development would have on flooding. The plans call for a 70,500 sq. ft. supermarket, a 4300 sq. ft. bank, 221 residential townhouse units, a parking lot and a four-story parking garage.
Although Dipple said that he considered flooding to be a "minor" constraint, he testified that infiltration systems will be installed above and beneath the property to carry the water away from the property. Dipple also said that the backflow preventer will alleviate any water from pooling on the property. However, residents contested that the backflow would only force more water into the river.
New Milford resident John DeSantis said, "If we have a flood, there’s 13 acres of water going downstream," adding that it will further flood streets that are continually being flooded.
When asked by Marc Leibman, attorney retained by Councilman Austin Ashley to represent him against this proposed development, about the elevation of the area where the supermarket is proposed Dipple testified that the area will be elevated by adding fill (soil).
DeSantis, pressed Dipple on the elevations of the proposed development citing previous flooding along the property. Dipple responded that elevation 14 is the regulatory flood elevation for New Jersey, and said that the elevation of Madison Ave. is 15, elevation for the proposed supermarket floor is 16, the parking lot in front of the proposed supermarket is elevation 15 and the area near River Road is elevation 23.
DeSantis said that he believed Hurricane Floyd reached elevation 18, which the map showed to be almost the entire property.
Karl Schaffenberger, Chairman of the Zoning Board who recused himself from the hearings, said that at the southern end of the property the elevation is approximately seven. Schaffenberg told Dipple that the flood waters were in the high school cafeteria after Hurricane Irene.
Dipple reported that there will be two detention system basins installed on the property to the south. Detention systems are designed to hold stormwater runoff before allowing it to be discharged as controlled outflow. They are utilized on a site to reduce the quantity of stormwater runoff leaving a site by temporarily storing the runoff that exceeds a site’s allowable discharge rate, and releasing it slowly over time.
In conjunction with the detention systems, Dipple said there will also be infiltration systems. Infiltration systems allow stormwater to freely permeate into the porous surface of a collecting basin and into the ground below. According to Dipple, if the infiltration systems on the site work there will be no runoff on the site.
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Dipple informed the board during his April testimony that the developer plans to utilize berms around the property to reduce the rate of surface runoff--rainwater that flows through areas with impervious surfaces, taking along with it gasoline, debris, and other potentially harmful chemicals. Berms are flood protection barriers that serve to direct water to areas that are not susceptible to erosion, thereby reducing the adverse effects of running water on exposed topsoil.
Both Leibman and SOD member, Anna Leone, asked Dipple if he was aware of any updates to the 1980 DEP map that he used when making his calculations. Dipple said that he was unaware of any updates and complied with all of the regulations that were in place when he submitted his engineering plans to the developer.
"If the state requires me to use that [revised] map I will, but now I'm complying with regulations," Dipple said.
Andy DelVecchio, attorney for the developer, Hekemian, objected to the question saying that even if flood maps were updated, this project might be "grandfathered" in.
When questioned, Dipple admitted that he had not been to the proposed site.
Due to the late hour, the board called to adjourn the meeting until June 12.
DelVecchio said that although Dipple would return for further public questioning, due to potential scheduling conflicts he did not know the date of Dipple's return.
Further testimony will continue on Tuesday, June 12 beginning at 7:30pm. There will also be another special meeting of the Zoning Board devoted entirely to the continued hearing on the proposed development of the United Water property on June 21 beginning at 7pm.