Fairfax County Flood Mitigation, Monitoring, & Dam Safety Program

True Environmental has been supporting Fairfax County’s Stormwater Planning Division (SPD) and MSMD under a five-year contract, delivering capital project program support, hydrologic and hydraulic (H&H) modeling, floodplain management, dam safety engineering, and related professional services. Over the first four years, True has completed 36 task orders valued at more than $4 million. Key projects include lake infrastructure repairs such as toe drain replacements and forebay dredging, multiple residential flood mitigation efforts, and comprehensive flood risk reduction studies aimed at addressing climate change impacts.

Technical highlights of True’s work include advanced 1D and 2D PCSWMM modeling, development of an Overland Flow Relief Method for runoff analysis, model calibration using the 2019 pluvial event, and detailed design plans with cost estimates. In addition, True has provided dam safety support through emergency action planning, structural inspections, and annual drills for state-regulated dams, as well as construction inspection and materials testing. These efforts strengthen Fairfax County’s stormwater resilience, improve regulatory compliance, and enhance public safety.