Panel Hopes Impervious Surface Cap Will Curtail Excess Storm Flooding

Matthew Hersh

As a means to address Princeton Township's increasing flood problems, a municipal review panel examined an ordinance Monday that would limit the square-footage of impervious surfacing a single-family homeowner would be able to build on a lot.

Increased impervious surfaces, as a result of increased development in general, have been blamed for the rising flood waters in the Township, particularly homes abutting Harry's Brook.

The recent string of rain-filled days has renewed resident concern as floodwaters creep closer to homes.

And while these latest measures, reviewed Monday by the Planning Board's Zoning Amendment Review Committee, do not promise to reduce the problem, the hope is that they will keep it from getting worse.

Right now, there is no standard for impervious surface coverage for single-family lots, according to Joe Skupien, a stormwater consultant contracted with the Township. Before now, he said, they were not needed, but as homeowners put additions on their homes, or expand driveways, a problem has been slowly growing.

"People are getting bigger: bigger house, bigger driveway," Mr. Skupien said, adding that placing a cap on impervious surfacing would effectively preclude additional flooding.

Not all properties in the Township were surveyed, but it was determined that once an additional 25 percent of impervious surfaces are added, it begins to be a problem for flooding and stream erosion. Those homes that are already above that cap, which is based on a sliding scale commensurate to lot size, would be "grandfathered," meaning those homes would not be required to reduce areas already categorized as impervious.

If the surface coverage caps are ultimately approved by the Township Committee, an applicant seeking to surpass the cap would have to seek a variance and mitigate the increase with dry wells, catch basins. or stone trenches.

Princeton has regulated its stormwater since the 1970s, Mr. Skupien said, except for this one component of existing single-family residences.

The proposed ordinance will likely be introduced at Township Committee's November 14 session.