Hahn Engineering has designed and construction administered more than a dozen stormwater management practices approved by the NYSDEC, NYCDEP, and MS4s. The practices include infiltration, Micropool Extended Detention, channel stabilization, hydrodynamic separators, pocket ponds, proprietary practices, regenerative stormwater conveyance systems, and wetland practices. The combined practices total 64.1 kg/yr TP removal at a cost of $3.3M, for an average cost per kilogram per year of approximately $51,000.

Hahn Engineering worked on a similar project for the City of New York, Croton Watershed, East of Hudson study which was part of the project in the New York City Watershed (Croton-Kensico Watershed Intermunicipal Coalition-CKWIC). The initial work was a study of the East of Hudson Watershed municipalities in New York State, but Hahn Engineering was also selected to work on the final design and construction management of numerous treatment practices. In the study, we conducted 170 individual sites, assessments, and preliminary design and phosphorus reduction calculations that were ultimately approved by the NYCDEP.