Township consultants say building a new lagoon cell is the preferred option to address ongoing problems at the Drayton wastewater treatment plant.
Robert Mayberry, of R.J. Burnside and Associates Limited, said the goal is to solve the “chronic problem” with spring discharge of treated effluent into the Conestogo River.
A public information meeting was held at the township office on Aug. 5 to discuss the environmental assessment that is required as part of any improvements at the plant located off of Sideroad 15, southwest of Drayton.
Problems at the plant occur when the effluent does not meet quality requirements for the spring discharge, often because of elevated phosphorous and/or ammonia levels that develop over the winter.
In the past, those problems have led the Ministry of the Environment (MOE) to partially or completely suspend the spring discharge, which usually occurs from March 1 to April 13. When that happens, as it did in 2003, 2005, 2006, and 2008, there is not enough storage at the plant to accept sewage from Moorefield and Drayton users until the fall discharge period (Oct. 1 to Dec. 31).
The plant, which was designed to handle an average daily flow of 750 cubic metres per day from Moorefield and Drayton users, currently operates at an average of 550 cubic metres a day, Mayberry said.
And while that may be enough for the 2,000 households currently hooked into the system, it can severely restrict residential development in the the two villages.
The goal of the environmental assessment is to identify and evaluate options to ensure effluent is “consistently acceptable for discharge,” while also considering constraints such as land use, capital, and operating costs, future capacity, and any possible impact on “the natural, social, cultural, built and economic environments.”
The engineers presented six possible solutions:
– do nothing;
– reduce sewage flows and/or optimize plant operations;
– introduce a modified discharge schedule;
– construct a mechanical plant;
– expand the effluent storage; and
– replace or upgrade the current sand filtration system or “effluent polishing works.”
Considering the growing population of the township, Burnside ruled out doing nothing and reducing sewage flows.
A modified discharge rate is likely not going to be approved by the MOE or the Grand River Conservation?Authority, which does not want effluent discharge to take place while recreational use of Conestogo River and Lake is at its highest (May through September).
Mayberry said the effluent is “clean” water so Burnside and Mapleton Township have lobbied the ministry and the GRCA for extended discharge periods and/or increased discharge flows, but those requests have “fallen on deaf ears.”
According to Burnside, upgrading the effluent polishing works is costly, may restrict future development, and presents “technical challenges.” That leaves a new mechanical plant and expanded effluent storage as perhaps the two most likely solutions.
However, cost alone will likely be enough to rule out a new mechanical plant; Mayberry estimated one the size required for Drayton and Moorefield would cost $10- to $12-million.
“In this case, increasing the effluent storage is likely the best way to go,” Mayberry said.
He said the cost would be “significantly less” than a mechanical plant, but he refused to provide a cost estimate last week for adding a fourth lagoon cell that will likely be 8 to 9 hectares in size.
However, in a 2008 report, Mayberry estimated a lagoon cell with a capacity of about 115,000 cubic metres would cost about $1,338,000.
While expanding the effluent storage will require a land purchase and displace farmland, Mayberry said last week a lot can be said for the “low-tech” approach of a lagoon system.
He said a fourth cell would allow effluent to basically sit all summer before discharge, which would significantly lower ammonia levels. In his 2008 report he said the extra cell would also allow the township “to miss the spring discharge entirely, if effluent conditions dictate, and store the final effluent until the fall discharge period begins.”
Last, Mayberry stressed the quality of effluent from lagoon systems is as good as that coming from a mechanical plant. Besides, a mechanical plant would still require some on-site storage, Mayberry noted, because summer discharge is prohibited.
He estimated the environmental assessment will take four to six months to complete. If the final recommendation is approved by Mapleton council, there will then be a 30-day public commenting period.
