Conger Marsh Water Pollution Control Plant

In order to protect the local environment from failing septic systems in the community of MacTier, east of Georgian Bay in Ontario, the District Municipality of Muskoka decided to build a wastewater treatment plant that would serve the population projected for 20 years.

The wastewater from the collection system is pumped from a new sewage pumping station to the new treatment plant located on the community’s west side, at Conger Marsh.

The goal was to develop a wastewater treatment plant that would, in a socially responsible way, protect the aquatic and terrestrial environment in which the plant is situated. Careful initial study led to locating the plant where it would minimize its impacts on the habitat of endangered species in Conger Marsh. Also, the plant itself was designed with a treatment process that produces a high quality effluent.

Totten Sims Hubicki Associates was retained in 2002 as the consulting engineer for the forcemain, wastewater treatment plant and outfall sewer.

Watching for snakes

Great care was taken throughout the project development, design and construction stages to maintain the existing habitat at Conger Marsh. Water quality was monitored at six sites, and plants, birds and reptiles were extensively assessed and inventoried.

The plant site is a known habitat for the endangered Eastern Massasauga Rattler and Hognose snakes. The Massasauga Rattler is the only venomous snake still found in Ontario, but due to its small size it is a minor risk to humans.

During the initial siting of the facility, a survey of snakes was undertaken to identify the areas they frequent and to ensure that the sewage treatment plant would not destroy their habitat. Snakes were captured, tagged and tracked for a period of two years to determine their movements and habitat in the area.

The alignment of the access road and the siting of the treatment plant and outfall, were designed to mitigate the impact on the snakes, and to minimize interactions between them and the plant operational staff. The access road to the plant was constructed with a series of culverts to allow the snakes to cross the road safely.

An individual from the Ministry of Natural Resources’ reptile awareness program provided training sessions for the construction staff, and whenever blasting had to be done adjacent to critical habitat areas, a biologist made pre-blast inspections, including seismic monitoring. To ensure the effectiveness of these measures, an extensive monitoring program is continuing for one year past the plant’s completion date in December 2006.

Producing high quality effluent

As the plant discharges to a very sensitive wetland area, a treatment process was chosen to provide an extremely high quality treated effluent. Designed to a capacity of 700 m3/day, the plant uses a sequencing batch reactor, tertiary filtration and ultraviolet filtration. Effluent disinfection through ultraviolet (UV) technology (instead of chlorination) prevents the formation of toxic chloride compounds.

The treatment plant process was designed to exceed the Ontario Ministry of the Environment’s criteria for effluent. One criteria not regulated by the Ministry, but voluntarily regulated by the design team, included nitrates and nitrites. Amphibians are sensitive to nitrates, depending upon the pH of a water body. The plant was therefore designed to provide denitrification as well as pH adjustment.

Energy use in the plant facility was minimized through the use of LEED (Leadership in Environmental and Energy Design) concepts, as well as extremely efficient HVAC controls. In the biological treatment process, for example, dissolved oxygen control was provided with the aeration system for energy savings. Light fixtures were selected to minimize light pollution in the surrounding environment and noise controls were included.

In order to reduce operating costs, the treatment plant process was designed to operate effectively unattended through the use of a sophisticated instrumentation and Supervisory Control and Data Acquisition (SCADA) system that monitors and controls the treatment plant process. The facility was also designed with remote alarming as well as redundant equipment and smart controls to mitigate the effects of equipment failures. CCE

Name of project: Conger Marsh Wastewater Treatment Plant, MacTier, Ont.

Award-winning firm/prime consultant: Totten Sims Hubicki Associates, Whitby and Bracebridge, Ont. (Robert B. Baker, P.Eng., Fred Clayton, P.Eng., Michael Gundry, P.Eng., Joe Peristy, P.Eng., Lew Pollard, P.Eng., Antony Aruldoss, P.Eng., Laurence Cudlip, OAA, Mark Benedet, P.Eng., Ross Gillespie, P.Eng., Peter Mitchell, CET)

Natural environment impact analysis: Michalski Nielson and Associates, Gartner Lee

Aquatic environment impact analysis: Senes Consultants

Sanitary sewer collection system design brief: C.C. Tatham & Associates

General contractor: Peak Engineering & Construction