Monitoring of a Best Management Practice Wetland before and after Maintenance

Abstract

The U.S. Environmental Protection Agency’s (USEPA) Urban Watershed Management Branch monitored a best management practice (BMP) wetland in the Richmond Creek (RC) watershed. This BMP, designated Richmond Creek #5 (RC-5), is owned and operated by the New York City Department of Environmental Protection’s as part of the Bluebelt program. During monitoring performed in 2003 and 2004, RC-5 was monitored for several water quality parameters including suspended solids (SS), chemical oxygen demand (COD), and phosphorous. Calculated SS loads demonstrated a 61% removal which is in line with the anticipated removals of 55%–57%, however, COD was not being removed from RC-5. Due to visible accumulation of sediment in the forebay and leaves throughout the BMP, maintenance activity was performed in the spring of 2005, to remove the sediment and organic matter (leaves) by vactor truck and physical labor. About four truck loads of sediment and leaf litter, estimated at 35 m3 (46 cubic yards), was removed from the site. Monitoring during the fall of 2005 measured the effects of this maintenance activity. The effluent concentrations of COD were significantly less and less variable after maintenance, and calculated influent and effluent COD loading indicated removals. The reduction in COD effluent coincided with drops in effluent phosphorous levels. Effluent SS concentrations were not significantly altered, implying RC-5 still had capacity to remove sediments before maintenance occurred. Indications are that the maintenance activity significantly reduced the COD effluent and may help communities manage phosphorous loadings.