An assessment of long-term monitoring data for constructed wetlands for urban highway runoff control

Abstract

Constructed wetlands have gained acceptance as a means of treating stormwater runoff from urban developments. Much of the available data regarding the performance of these facilities is based upon monitoring conducted over the course of less than two years, and as such inherently assumes that the period of analysis represents the "typical" or "design" conditions under which these facilities are intended to operate. While this information has provided guidance regarding the mechanisms by which wetlands provide quality treatment of urban runoff, it does not fully reflect the variability of conditions under which the facilities operate over the fullness of time, which is of particular concern to designers and operators. The construction of the Dartnall Road Interchange, as part of Hamilton's Lincoln Alexander Parkway, required a monitoring program-which included five years of water quality sampling-as a condition of approval by the Department of Fisheries and Oceans. This paper reports on the quantitative and qualitative wetland water quality monitoring data (sediment, nutrients, metals) obtained over the course of a total seven-year program, and provides information regarding the operating conditions and estimates on contaminant removal efficiencies from the facilities.