As published in The Erin Advocate
The amount of phosphorus contamination in the
West Credit River is “a key parameter of concern” that will limit the future
population of Erin village and Hillsburgh to 6,000 people, according to a
presentation from SSMP Consultant BM Ross.
At a meeting of the Liaison Committee for the
Servicing and Settlement Master Plan on April 9, factors surrounding the
Assimilative Capacity Study (ACS) were discussed.
Early last year, BM Ross Project Manager Matt
Pearson was estimating that the ACS could result in an urban population cap of
more than 9,000, depending on treatment methods and comments from the Ministry
of the Environment (MOE) and Credit Valley Conservation (CVC).
Additional stream monitoring, plus a reduction
to account for climate change, has resulted in a more conservative cap of
6,000. Town Council recently endorsed the strategy of reserving sewage capacity
for the 4,500 existing residents of the villages, leaving 1,500 (33%) for
growth.
A detailed financial analysis of costs per
household will now be done, for both traditional gravity based sewers and the
alternative small bore collection method.
The final SSMP report will examine the implications
of three scenarios, including the status quo – no sewers. That could lead to a
rigorous inspection system and upgrading of septic systems. For those with
large enough properties to upgrade, the cost could be similar to a sewer
system.
Mayor Lou Maieron has speculated that the Town
might have to try to get special permission to allow new housing on septic
systems. A new housing development is being allowed in Cheltenham on medium
sized lots close to the river, but strict effluent criteria mean that each
septic system will cost about $40,000.
The scenario of a “big pipe” delivering waste
to another municipality would allow a much higher population in Erin, but BM
Ross says this option is very expensive, and may not be desirable or practical.
Building sewers for existing urban homes, plus
about 500 new homes, will be the prime scenario for discussion. Pearson says it
will only work if all the urban households are obliged to contribute to the
cost, though he said those with newer septic systems could be offered a grace
period to delay hook-up.
“There are going to be some people who are
going to have to take one for the team,” said Pearson, who has always contended
that substantial funding from senior governments would be essential to the
feasibility of a sewer project. “Communal servicing is cheaper in the long run,
if you get some help.”
Many river contaminants were analyzed as part
of the SSMP, but there was particular concern about phosphorous and nitrates,
nutrients that can come from fertilizers and other human activity. Certain
amounts exist naturally, but excessive levels can increase vegetation growth
such as algae and deplete dissolved oxygen, affecting fish and other aquatic
life.
Phosphorous levels are always changing.
Concentrations have been measured monthly over the last 35 years, with readings
tracked at their 75th percentile level according to MOE standards.
Levels drop
every April, August and November, but spike high in June, September and
December. Having 6,000 people on sewers would put those peaks at the MOE
maximum of 0.03 mg of phosphorus per litre of river water.
Nitrates are the next limiting factor, so the
treatment plant may need special de-nitrification technology to keep levels in
a safe range. There is also the possibility of storing fully-treated effluent
in lagoons during months when river contamination is already high, and
releasing it later when levels drop.
Any technology that reduces the impact on the
river could be used to argue in favour of more housing, but no dramatic changes
to the 6,000 limit are expected.
Even an aggressive water conservation system
(mandatory low-flow toilets, for example) could lower the amount of sewage and
create extra capacity.
Discharging effluent at the Tenth Line has been
discussed in the past, but river water quality is better at Winston Churchill
Blvd., making it a better discharge point. The sewage treatment plant does not
have to be the discharge point. It could be piped to another spot for discharge
– although John Kinkead of CVC warned against a pipe next to the West Credit,
since river flows can shift over time.
