Call your town or city Conservation Commission.
If the work is happening on a weekend or at night, you could also try your city or town’s emergency line (which could be the police, the DPW, or another agency), and ask to have the message forwarded to your Conservation Commission Agent, the police department, or town administrator/Mayor’s Office.
Why? The Conservation Commission is responsible for approving construction within 100 feet of wetlands and within 200 feet of rivers and streams. The Conservation Commission should know if the work has been approved. If the work has not been approved, the Conservation Commission can issue fines or a stop work order. If the work was approved, there should be a DEP file number posted on a sign at the site. The Conservation Commission may have set limits on the work, required hay bales to control soil loss, and defined the work area.
Also, even though approved, the developer may not be complying with conditions. If you see erosion running into wetlands or streams, hay bales out of place, etc, you should report these conditions to the Commission.