Unfortunately it is a holiday weekend, which is why you are unable to get an answer at the township. Some land in the township is wet with water after rains, yet not classified as "wetlands" and is fully buildable. While others may truly be protected, below is some information I hope you find helpful.
The NJ Wetlands Act of 1970 regulates all dredging, filling, removing or otherwise altering coastal and tidal wetlands unless an application is filed for a permit with the NJ DEP. You also should be concerned with the Freshwater Wetlands Protection Act of 1987. Freshwater wetlands serve a variety of important ecological functions, including the natural purification of surface and ground waters; protection from flood and storm damage; and a habitat for wildlife and migratory birds. The Act defines a wetland as "an area that is inundated or saturated by surface water or ground water at a frequency and duration sufficient to support, and that under normal circumstances does support, a prevalence of vegetation typically adapted for life in saturated soil conditions, technically known as hydrophytic vegetation." The Act also requires that wetlands be designated according to guidelines established in the Wetland Identification and Delineation Manual developed by the U.S. Environmental Protection Agency. Copies of the USEPA delineation manual can be obtained by calling 609 530-5790. It is your safest bet to address your questions to the appropriate authorities. I'm sure the township office will be open on Tuesday, you can contact them at 732 329 4000.
There are quite a few lots available in the township, let me know if I can assist further and if you'd like me to show you others. April Leavy, Re/Max Greater Princeton 732 266 2079, http://www.homesbyapril.net, email@example.com