Demonstrating Porous Pavement Performance in NYC Using Enhanced Modeling Methods

The New York City Department of Environmental Protection (DEP) Green Infrastructure Program was established to manage stormwater through low impact development technologies utilizing stormwater management source controls, or green infrastructure (GI), to reduce Combined Sewer Overflows (CSO) and improve water quality in New York Harbor. The Green Infrastructure Research and Development (GI-RD) Project supports this program through strategic experimentation, research, monitoring, and assessment of new and existing GI systems throughout the City. Porous pavement, including porous precast concrete panels, are being piloted and implemented as a GI technology in several locations along parking lanes. These GI practices capture stormwater at the surface from the tributary streets and sidewalks and convey the runoff to a subsurface storage layer allowing for infiltration and recharge through the underlying soil layer. The intent of this GI practice is to reduce the amount of stormwater volume entering the combined sewer system.
The performance of these porous pavement systems is impacted by several factors including hydraulic loading ratio, sediment loading, capture efficiency, underlying storage layers, soil infiltration capacity, and maintenance. While some of these values are well defined at the design stage, several are variable and may change throughout the life of the system. Understanding these variables, acceptable variations, and how they impact performance are key factors to confirming viability of these porous pavement GI systems.
This presentation explores two specific pilot areas, one in Queens, NY and one in Bronx, NY. Utilizing monitoring flow data collected pre- and post-construction of porous pavement systems, models were developed to compare performance results for each location over a one-year period after construction to their respective anticipated pre-construction values. The calibrated models also show performance of the porous pavements systems as compared to the design intent as well as impacts to performance due to system variable changes as described previously. The calibrated GI models were also utilized to evaluate projected system performance for various scenarios based on adjustments to maintenance parameters such as time to clog, cleaning frequency, and level of surface restoration. The selection of scenarios and system variable values were supported by actual system performance testing results conducted over several months, incorporating pre- and post-maintenance conditions where surface restoration activities were performed. The maintenance variable results were utilized together with a cost-benefit approach to establish the ideal maintenance protocols for porous pavement systems in NYC. These results help DEP further evaluate and improve the use of porous precast concrete as a viable GI solution in the right-of-way (ROW) to help achieve harbor water quality goals.