Runoff was the main topic of discussion as attorney Jeffrey Brookner spent Tuesday’s planning board meeting discussing whether a proposed development on the will cause future flooding for nearby residents.
The application is for the building of 18 single-family homes on 36 acres of woodlands on Twin Oaks and Foothill roads, formerly owned by the late John Wemple, and currently owned by Steve Lang.
Wemple, who willed the property to his nieces and nephews after his death in 2002, had maintained to his neighbors that he never wanted to see the land developed, and made that a part of his will, which was overturned by the Superior Court of New Jersey in 2005.
Brookner is representing , an organization made up of more than 60 residents who oppose the application.
Tuesday’s meeting involved mostly Brookner’s questioning of James Mantz, engineer for the applicant, who completed his initial testimony at the .
For much of his questioning, Brookner focused on concerns about flooding in the areas of Berrywood Lane, Foothill Road and Twin Oaks Road.
First, Brookner questioned the steepness of a specific driveway near the edge of the property.
“Are you suggesting that whatever the consequences of the flooding is, it doesn’t matter because others across the way are the same steepness?” he asked. “The only thing you can say about the steepness of the driveway is that it’s like the others.”
Mantz said a driveway at the edge of the Wemple property is similar to others across the way on Berrywood Lane.
“The township ordinance allows the slope up to a certain amount of feet,” he said. “I believe I said we would comply with the recommendations of [the township].”
In addition, Brookner questioned whether the applicant has considered the natural spring on the property in designing the properties.
“Given the proximity of the natural spring, is there a risk that it could be cutting into the water table?” he asked.
Brookner also questioned whether there has been any consideration for the effect of storms on the proposed development and the properties that are already nearby.
Mantz said he performed a soil conservation method to test it, looking at daily storms, for example, in which it begins raining in the morning, gets heavier in the afternoon and lessens later.
“As the moisture in the ground accumulates, you get more runoff,” he said.
The ranges of rainfall in certain kinds of storms, Mantz said, ranges from 2.7 inches to 8.2 inches.
But, Brookner said, he wondered if the applicant had considered the effects of a flash flooding situation in the area.
“Would you agree that intense storms like that are a problem for hillside development?” he asked. “In an intensely heavy rainfall that lasts only 20 minutes, did you look at how the drainage system might be affected?”
Mantz said he does not know if he necessarily agrees with that statement, or if checking is necessary.
“The soil conservation study tends to overestimate the amount of runoff,” he said. “I have never seen any studies that compare with flash flood-type rainfall.”
As for reducing runoff, Mantz said, the applicant is working to model the new draining after existing patterns off Foothill Road.
“We are taking water from up above our sites and putting it through detention basins, and reducing the rates of runoff,” he said.
But Brookner cited a concern that more impervious coverage on the site will increase runoff on many different properties, despite the drainage changes and the detention basins.
And township planner Scarlett Doyle said she does have a concern about additional impervious coverage. She said that over the last few decades, people have come to the township saying that in previous years there were never rain puddles in yards and water-filled basements, but things have changed.
“The last few years, people have been getting more and more water,” she said.
So, Doyle said, she was wondering if the applicant had taken into account the amount of additional runoff based on about 8,000 square feet of impervious coverage for each proposed lot.
Mantz said he has.
“If every lot is built out to maximum capacity, you have handled that in the drainage calculations?” Doyle asked.
Mantz said the calculations have been done that way.
“The ordinance required me to calculate by various methods the runoff that comes off the site,” he said. “We looked at drainage patterns, and thought three separate drainage basins would be appropriate.”
“If there are 50 cubic feet per second running down the side of the mountain, we are only allowed to release 80 percent of that so that the peak rates of runoff are compliant with those 10-year and 100-year storms,” he added.
In addition, in terms of detention basins, Brookner suggested that perhaps there could be additional landscaping at the southwest corner of Twin Oaks and Foothill roads where there will be a detention basin. He said there are currently roughly a dozen trees in front of the drainage reservoir, and once the basin is created, the applicant is only planning to put in three.
“The area as you drive down Twin Oaks Road and turn left on Foothill Road is pretty wooded,” he said. “Wouldn't having the open space drainage with three trees be pretty out of character?”
Mantz said drivers wouldn’t necessarily see the workings of the basin, but that more trees could be put in. Still, he said, he does not believe there would be any problem in the neighborhood.
“On the south side of Foothill, I don’t believe you get a wooded appearance, so I don’t think it would change the character of the neighborhood,” he said.
The applicant also addressed a request from the board concerning implementing new sewers instead of requiring pumps for some of the proposed lots, as the applicant had previously outlined. But, the attorney for the applicant said doing so would require purchasing easements from some residents living near the property.
Brookner said he would check with those residents to determine if they would be willing to sell those easements.
Questioning of Mantz was completed by the end of Tuesday’s meeting, and testimony will continue with the applicant’s environmental expert July 23 at 7 p.m. at the municipal complex.