The possibility of cutting back the capacity of Erin’s proposed
wastewater system, with a savings of $8.8 million, was rejected unanimously by
town council at a special meeting Jan. 26.
The possibility of scaling down the system was discussed previously,
and council had asked Environmental Assessment consultant Ainley Group for a
report. They wanted to deal with the issue before this week’s Public
Information Centre – on Friday, Feb. 2 at Centre 2000, 6-9 p.m.
A treatment system with capacity beyond what is needed even for
current population projections will give Erin flexibility for several future
revisions of the Official Plan, said Ainley President Joe Mullan.
“The trunk sewer system and the treatment plant infrastructure will
service the community for many decades,” he said, noting that some components
could operate for 100 years.
“It was the prudent course of
action, ensuring capacity for commercial and industrial expansion,” said Coun.
Jeff Duncan, who had pushed for the analysis.
Had council ordered a lowering of the sewage flow rate, Ainley would
have charged $40,000 to revise five of its technical reports.
A key factor in designing a wastewater system is the maximum amount
of liquid that a treatment plant could handle. This is based partly on average
water consumption in the community, which from 2013 to 2015 was 195 litres per person,
per day (L/p/d).
A factor of 2.8 persons per home is used in the projections, which
is currently set for an urban population growing from the current 4,500 to
about 14,600 over 20-30 years.
Ainley has added a “safety factor” of about 50 per cent to the water
flow allowance, resulting in a rating of 290 L/p/d. Then, as required by the
Ministry of the Environment and Climate Change (MOECC), they added an extra 90
L/d/p for infiltration (water that typically leaks into sewer pipes, increasing
flow to the plant).
This has resulted in a proposed flow rate of 380 L/p/d. This was
criticized as too high at a public meeting last June, even though it is lower
than the flow rate of used by consultant B.M. Ross when they completed the
Servicing and Settlement Master Plan in 2014.
It would mean a sewage treatment plant large enough to handle an
average flow of 7,172 cubic metres of liquid, or 7.2 megalitres per day (MLD).
No estimate has been provided of how large an urban population this could
support, but it is beyond 14,600.
These numbers were used for the cost estimate of $118 million for
full build-out of the whole system, including a treatment plant costing $61.1
million.
Ainley analyzed the possibility of cutting the safety factor down to
15 per cent, effectively reducing the total flow rate to 315 L/p/d, or 6.23
MLD.
That would reduce the cost of the plant to $54.3 million. There
would be additional savings on pumping stations and sewer mains of about $2
million, for a total savings of $8.8 million. A portion of the savings would go
to developers helping to pay for the system.
Mullan noted in his report that both the flow rate recommended for
Erin, and the allowance for water infiltration are both lower than the levels
used in the City of Guelph and the Regions of Peel and Waterloo including their
member municipalities.
Other factors cited for building extra capacity include the fact
that current water usage may be at a “conserved” low level, and could increase
once residents are not concerned about septic systems in their yards.
The development of secondary suites on existing properties is
expected to increase wastewater flows.
