Monahan Drain Constructed Wetlands

Former City of Kanata

Project Details

We were retained by the former City of Kanata to carry out final design and contract document preparation, field inspection, and contract administration of the Monahan Drain Constructed Wetland.

This artificial wetland complex was identified in earlier studies as the preferred method for treating urban stormwater discharges from both existing and future growth areas in the Bridlewood area.  It was also designed to provide a high degree of bacteria removal in an attempt to meet the stringent water quality objectives set for the Rideau River, where storm discharges must not exceed 100 E.Coli per 100 ml and 25 mg/l of total suspended solids (TSS) with an allowance of four or fewer exceedances between May 15th to September 15th.

This artificial wetland complex, with approximately 230,000 m3 of overall storage, consisted of three storage cells sized to provide both flooding and erosion control, a wetland cell, and five sedimentation forebays designed to meet the water quality objectives of the Rideau River.  The wetland complex was designed to offer diversified wetland plantings that are native to the Ottawa area.  Plantings consisted of numerous species for each of the five zones: deep aquatic, deep emergent, shallow emergent, riparian, and upland zone.  The intent was to direct storm flows through all zones to maximize the wetland’s ability to remove nutrients, TSS, and E.Coli.  Various complex engineering analyses were carried out to size the different elements of the facility: hydrological to simulate synthetic design storm events, long-term simulations to evaluate removal of bacteria and TSS, long-term simulations to assess erosion and investigate rain-on-snowmelt events, and steady-state and hydrodynamic hydraulic analyses.

The wetland is now an important community feature of Bridlewood, used for many passive recreational pursuits.