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Monitoring of a Best Management Practice Wetland Before and After Maintenance
OCONNOR, T. AND J. ROSSI. Monitoring of a Best Management Practice Wetland Before and After Maintenance. JOURNAL OF ENVIRONMENTAL ENGINEERING. American Society of Civil Engineers (ASCE), Reston, VA, 135(11):1145-1154, (2009).
Peer Reviewed Journal
The USEPA’s Urban Watershed Management Branch has monitored stormwater drainage and best management practices (BMP) as part of its overall research program. One such project monitored a retention pond with wetland plantings in the Richmond Creek (RC) watershed; one of several installations under the New York City Department of Environmental Protection’s Bluebelt program. As part of this effort, continuous monitoring equipment was deployed to measure both storm events and periods between storms in the BMP. After deployment, continuous monitoring equipment can often be subject to drift, i.e., deviate from initial calibrated values. The rate of this drift can be assessed as described in this paper. There were also readings for ammonium (NH4+) which exceeded expectations for drift or storm event response. Concentrations of ammonium (NH4+) exceeded 2 mg/l, with a maximum concentration of 8 mg/l recorded. These observations occurred between 12/5/03 and 12/11/03 after snow events. Increased conductivity was also measured at the influent to RC-5 contrary to typically low conductivity readings after precipitation. Deicers (sodium chloride) spread on the roadway most likely caused increased NH4+) readings, as sodium ions are a known interference. To back up this claim, controlled laboratory experiments were performed to test the responsiveness of the monitoring equipment. Two tests were performed where salt was dumped into a bucket containing a probe. A determination was also made as to whether decaying leaves may have contributed to these elevated NH4+ readings. Results of the dump tests indicated salt at low ammonia concentrations is a measurable interference. Decaying leaves did increase NH4+ concentrations as measured by the electrodes, indicating low inter-event background concentration may be valid, but that this could not be the cause for the extreme rates measured in the field.