Continuous Simulation of an Infiltration–Exfiltration System Loaded by Stormwater

Abstract

Roadway infrastructure is spatially extensive, linear, and by design restricts infiltration. Traffic impacts the coupled hydrology, chemistry, and loads transported by increased runoff and hydraulic stresses. Green infrastructure or low-impact development (LID) such as a partial exfiltration reactor (PER) can mitigate impacts by infiltrating and sequestering runoff and loads. This study modeled surface–subsurface hydrologic quantities for an infiltrating–exfiltrating linear PER as integrated infrastructure at a highway monitoring station with a database and calibrated modeling. The PER combined cementitious permeable pavement (CPP) as an infiltrating-filtration surface over an oxide-coated media (OCM) bed as a green infrastructure retrofit to conventional roadway underdrainage. Calibrated surface [Storm Water Management Model (SWMM)] and subsurface [Variably Saturated 2D Transport Interface (VS2DTI)] model components for the catchment and PER were implemented based on published studies. In contrast to previous design and historical storms, 1 year of hydrologic and dissolved Zn loads was simulated. The PER infiltrated 95% of catchment runoff, exfiltrated 27.1% to clayey glacial till soil, evaporated (potential) 3.9%, and discharged 63.9% to the underdrain. The CPP separated 80% of particulate matter (PM). With a simulated macropore in the oxide-coated sand media (OCS) bed, Zn was reduced by 99%, compared with 98% from event-based published data. Traffic turbulence increased evaporation from the catchment by 28.9%. A calibrated continuous simulation model is a viable tool to examine longer-term behavior of green infrastructure and LID systems for implementation, functionality, and sustainability in roadway and paved urban land uses.