Thursday, January 19, 2006

Porous Pavement and Infiltration Basins

The flooding is now so extensive water is flowing into the woodlands to the south. You can actually see the currents flowing. We can only expect it will get worse as winter progesses.

Porous Pavement and Infiltration Basins

TC South Brunswick, Inc. proposing 3 warehouses on some 118 acres of land in the aquifer recharge area east of the
NJ Turnpike from the Pigeon Swamp Park and the VanDyke Farm.

To the developer's credit, they are using best practices to control stormwater runoff from their site. Thanks to the new DEP regulations, there is strict control over runoff, so new techniques management are needed. TCSB is working on two ideas.

The first is the most controversial. In their car parking areas, TCSB proposes using porous pavement. Designed to let water filter through, rather than run off, these special paving materials are new to builders and engineers. This leads to definite uncertainty as to how strong they are and how long they will last under traffic. TCSB seems willing to take the risk of this innovation. The Township is more skeptical but we hope something can be worked out. If TCSB's gamble pays off and the paving material proves an excellent solution to decreasing impervious surfaces so more water can be absorbed into the ground where it belongs, all of us will be winners. However, if the paving material does not stand the test of time and traffic, South Brunswick could be left "holding the bag" on essential repairs. It might be a good idea to test out some porous sidewalks in the area first, but either way the concept is worth a second look.

The second technique is the building of infiltration basins and swales instead of more conventional detention or retention basins. These ponds are designed to hold water and, with porous sand bottoms, allow the water to percolate back into the soil. Well designed and well maintained, such basins can substatially reduce stormwater runoff. This is another positive development, provided the warehouses maintain the basins to maximum efficiency. That is always a concern as the best laid plans oft go the way as time passes and people forget the issues surrounding them.

Worrisome is the fact that the builder also must widen Davidson Mill Road in order to complete his construction requirements. This will increase runoff into the already overburdened downstream system in the State Park since that is where that new water will drain. Before any such move is made, a complete study of the impact of this water must be made. More later on this, but the EVA will try to make this a condition of approval.

TCSB's traffic engineer did not yet testify. EVA has taken a strong position on traffic issues in the area and will do so at the next meeting on February 1. All EVA members are encouraged to attend, even if they are only able to stay for part of the meeting.

The pictures with this blog show how the flooding has continued this winter. This last photo is taken from interior woodlands where the water is now flowing freely flooding out more old growth trees. Trust me, it's a real mess out there.


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