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Chloride Released from Three Permeable Pavement Surfaces after Winter Salt Application - journal
Borst, Mike AND R. Brown. Chloride Released from Three Permeable Pavement Surfaces after Winter Salt Application - journal. JOURNAL OF AMERICAN WATER RESOURCES ASSOCIATION. American Water Resources Association, Middleburg, VA, 50(1):29-41, (2014).
This paper describes the chloride concentration in the exfiltrate from three permeable surfaces at a parking lot installed at the Edion Environmental Center
EPA does not classify chloride as a priority pollutant. It is often unregulated in stormwater runoff but has been a target stressor for Total Maximum Daily Load (TMDL) allotments developed for multiple waterbodies. Previous research has shown that road salt applications increased chloride concentrations in surface water. Few studies exist on how infiltration-based stormwater control measures react to salt applications. Those that do exist have small datasets showing a trend of high concentrations during winter months, with rapidly declining concentrations that remain detectable during the remainder of the year. In 2009, EPA constructed a 0.4-ha parking lot surfaced with three types of permeable pavement (interlocking concrete pavers [ICP], porous concrete [PC], and porous asphalt [PA]) to measure hydrologic and water quality effects of the different permeable surfaces. Each permeable surface has four equally-sized, lined sections that direct infiltrate to collection tanks that enable composite sampling for water quality analysis. Samples were collected during two winter salting seasons and for the remainder of each year. The chloride concentrations measured in the permeable surface infiltrate samples exceeded the EPA acute criterion for aquatic life (860 mg/L) in the winter months because of salt application. Concentrations in the infiltrate remained measureable year round, but they did not exceed the EPA chronic threshold of 230 mg/L in samples collected after April. The chloride concentration decreased with cumulative rainfall depth since previous snow event, which was described well by a power regression. Based on the power regression, PC had the largest initial concentration in the infiltrate from the rainfall event immediately after a snow event, while PA was the lowest. The chloride concentration deceased most rapidly in the infiltrate from the PC and most slowly in the infiltrate from the PA. The mean infiltrate concentrations from the PC and ICP were not significantly different from each other. The infiltrate concentrations from each surface were notably different from impervious hot mix asphalt runoff concentrations. The salt applied to the hot mix asphalt is flushed rapidly from the surface by the subsequent events and was often (>77%) undetected in samples, including in the winter months (undetected in three of six events).