In a report to the Town of Erin, Ontario, Gary Scott of Ainley Group, Consulting Engineers and Planners, has found that an subsurface wastewater disposal system for the communities of Erin and Hillsburgh would not be expedient. Were the project brought to fruition, it would be the largest subsurface disposal system in the province.

The report delivered an overview of its findings based on Treatment and Disposal Regulations, Land Availability, Topography, and Cost. Ultimately, the report found that while it might be possible to establish the subsurface disposal system, meeting regulatory requirements would likely cost 10–20 per cent more than a comparable surface disposal system.

Further to that, the report found that due to the scale of a subsurface disposal system, which would have to treat an anticipated more than 7,000 m3 per day, raises concern for its potential effectiveness. The report notes that the most common subsurface disposal systems typically discharge an average of 10–80 m3 of treated effluent per day.

Sewage Flow Rates

Courtesy, Ainley Group, Town of Erin.

While cost and the likelihood of the system’s failure could be managed, the report sees the primary constraint for Erin in land availability. To find appropriate land, the town would have to acquire space subject to land owners’ willingness to sell their land, avoidance of Well Head Protection Areas, Highly Vulnerable Aquifers, and a 300 metre buffer from surface water features. Based on these constraints, the report finds it unlikely that there would be sufficient land near the community of Erin for a subsurface disposal system.

“It is clear from this overview, that potential locations for subsurface disposal within the Erin and Hillsburgh areas is severely limited mostly due to the extensive pattern of surface water drainage and topography but also due to the potential impact on drinking water supplies.”

Finally, the report concludes that, “It is suggested that subsurface disposal of treated wastewater effluent for Erin Village is not viable,” and that “it is suggested that subsurface disposal of treated wastewater effluent for the community of Hillsburgh offers no advantage over the preferred surface water discharge.” Ainley Group then recommends that the Town of Erin move ahead with Phase 3 Class EA based on a single plant discharging into the West Credit River, including the subsurface disposal report in the findings of their Phase 2 Class EA.

Water Canada previously reported on the Town of Erin’s approval of the feasibility study. The full report can be found on the Town of Erin’s website.


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