West Windsor residents will recall that Princeton Hydro and SWM Consulting issued two detailed stormwater reports last May. These dealt with the flooding that occurs in the Washington and Alexander road areas after heavy rainstorms, such as in 2011 after the Irene/Lee event and again at the end of April, 2014. Possible strategies for managing stormwater in the InterCap site were also discussed.
These reports along with their supporting data are on the town’s website. The township was supposed to hold a public meeting to discuss both reports, but no such meeting has been scheduled. In the meantime, internal meetings are in progress to discuss follow-up.
My own interest started with a letter about Little Bear Brook (The News, June 13, 2014) followed by a full article on July 11. This article covered the PowerPoint presentation given by the above two companies on June 30 of that year.
The current (“Phase I”) SWM report suggests that inadequate storm sewerage in the Washington Road area is likely the main issue there. I asked our engineering department several years ago whether any maps of the town’s storm sewer system were available, but there weren’t any. Lacking these and information as to the pipe sizes and where they discharge, we are not yet in a position to make hypotheses about the adequacy of the present system. However, all Penns Neck-area stormwater that doesn’t soak into the ground or evaporate must discharge into Little Bear Brook via surface runoff and/or storm sewers, as there are no other available watercourses.
Installing larger storm sewers may not be practical along this heavily traveled county road, and in any case such pipes aren’t really intended to serve as temporary reservoirs. In heavy rain events they would likely fill up quickly and once again cause Little Bear Brook to overflow. It just might take slightly longer than before.
There is also the question of where the water has to go even if you temporarily detain some of it. The SWM study showed that Carnegie Lake, which takes the flow from the Millstone River, Stony Brook, and their respective tributaries including Little Bear Brook, is not the real problem. The issue is that the lake cannot discharge water rapidly enough due to its own downstream limitations. In effect, it is like the Little Bear Brook/Millstone River system but on a much larger scale. There is not enough gradient and capacity between the lake and its ultimate discharge point (the Raritan River) to allow the water to flow away quickly enough to avoid backwater coming into West Windsor and farther upstream — let alone the extensive flooding that takes place in other communities downstream of the lake.
As resident Andy Bromberg suggested after the June, 2014, presentation, what would help would be computer modeling of the whole drainage and downstream area including the rate of water input as a function of variables such as rainfall intensity, locations, and durations. Then you could vary these inputs over wide ranges and predict what might happen if you changed such things as storm sewer sizes, their locations, the sizes and location of detention basins, downstream effects, and so on.
We have many aspiring young engineers, scientists, and computer experts in our local student population. I propose that we set these resourceful minds at work on this problem for possible extra classroom and college application credit.
It could be a perfect summertime project. Background research and fieldwork would be followed by setting up a model and then numerically solving systems of differential equations involving fluid dynamics. Sophisticated mathematical tools are now available and I have every confidence that we’d get some interesting results.
This could be done in parallel to the proposed Phase II study by outside consultants. The resulting competition would be stimulating for everyone concerned, and the students would learn a lot in the process. (Plus, they work for free!)
The Princeton Hydro report investigated possible locations of detention facilities at the Intercap site. Only two places seemed feasible — one on privately owned land and another in an isolated, wooded area that would conflict with the proposed (but unfunded) Vaughn Drive connector.
The administration’s viewpoint is that any approach should be regional, i.e. involving several areas. However, as pointed out at the end of the report, getting the required approvals for a regional project could be very difficult because many separate agencies would have to sign off. As the authors say, “It is recommended that each project within the redevelopment area provide for individual on-site measures to satisfy the stormwater quality requirements of that specific project. This is a simpler, more measurable goal than attempting to address water quality requirements on a regional level.”
We look forward to a presentation where these issues can be discussed at more length and the public would be invited to comment.
John A. Church
West Windsor
