City of Annapolis Stormwater Mapping, Inventory, and Assessment for MS4 Compliance

Princeton Hydro is currently a subcontractor to GreenVest, LLC who is under contract with the City of Annapolis to help bring the city into compliance with its National Pollutant Discharge Elimination System (NPDES) General Permit for Discharges from Small Municipal Separate Storm Sewer Systems (MS4). The City is currently under a consent decree for not meeting the permit conditions.

Starting in 2020, Princeton Hydro, under GreenVest’s direction, focused on mapping the storm sewer system within the subwatershed with the most impervious surfaces. Princeton Hydro used GPS equipment and GIS software to map the existing storm sewer system, inspect storm outfalls for potential illicit discharges, and track the illicit discharges to their source. During inspections, Princeton Hydro identified and confirmed the presence of mapped and unmapped storm sewer inlets, outlets, and manholes. During inventory, Princeton Hydro collected data on the condition of the structure and internal connections (e.g., type, size, direction, material). Within GIS, Princeton Hydro created a database to map the storm sewer network.

Princeton Hydro has also prepared the Standard Operating Procedures manual for this work and helped to prepare the City’s Good Housekeeping and Pollution Prevention Plans for City-owned facilities that discharge stormwater. Future work for the City will include completing an inventory and map of the remaining subwatersheds, continue to inspect outfalls, continue to identify Illicit Discharges, and develop new and innovative ways for the City to treat existing stormwater.