In Situ Partial Exfiltration of Rainfall Runoff. I: Quality and Quantity Attenuation

Abstract

Rainfall runoff impacted by anthropogenic activities transports significant quantities of particulate, aqueous, and complexed constituents. These diffuse, unsteady, and stochastic event-based loadings are unique challenges for water quality (concentration, mass) and quantity control (volume, peak flow). While many infiltration/exfiltration structural best management practices (BMPs) or low impact development practices are implemented, few in situ data sets are examined for actual events and temporal-based BMP behavior, in part due to costs of such examinations. Fewer studies provided a statistical and mechanistic interpretation for event-based BMP performance. The design, water quality, and quantity functions of a partial exfiltration reactor (PER) utilizing Fe-coated sand is examined specifically across three water quality type rainfall-runoff events over a 10-month period. Reduction of total concentrations for metals (Zn, Pb, Cu, and Cd), ranged from 24 to 93%, while total mass reductions ranged from 57 to 98% due to exfiltration. Reduction in total suspended solids concentrations ranged from 23 to 86% while reduction in total mass ranged from 69 to 96%. Chemical oxygen demand concentrations reductions ranged from 37 to 70%. Storm water volume reductions ranged from 55 to 70% through variably saturated exfiltration to surrounding clayey glacial till soils