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

The City of Annapolis collaborated with Princeton Hydro to achieve compliance with its National Pollutant Discharge Elimination System (NPDES) General Permit for Discharges from Small Municipal Separate Storm Sewer Systems (MS4).

The project began with mapping the storm sewer system, focusing on the subwatershed with the highest percentage of impervious surfaces. Using GPS equipment and GIS software, the team mapped the existing storm sewer infrastructure, inspected outfalls for potential illicit discharges, and traced any detected sources of contamination. During these inspections, the team identified and verified both mapped and previously undocumented storm sewer inlets, outlets, and manholes. The team also assessed the condition of each structure, collecting data on internal connections, including type, size, direction, and material.

All collected data was integrated into a GIS-based database, providing the City with a comprehensive and actionable map of its 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, continuing to inspect outfalls and identify Illicit Discharges, and developing new and innovative ways for the City to treat existing stormwater.