Many variables in wastewater projections

A series of variable factors is used in calculating how much wastewater can be processed by a treatment plant, while meeting provincial regulations. The numbers limit how many households could be serviced, and therefore how many new homes could be built.

Here are the main issues for a Town of Erin system, as outlined by Ainley staff at the June 22 Public Information Centre. They help explain why the potential urban population for Hillsburgh and Erin village has increased from 6,000 to 14,559 (over 20-30 years). Erin village could go from 3,225 to 8,565 residents, while Hillsburgh could go from 1,391 to 5,994.

Total Phosphorus

A treatment plant improves effluent quality by lowering concentrations of suspended solids, E.coli bacteria, ammonia and nitrates, and maintains desirable levels of acidity and oxygen. But a crucial constraining factor is Total Phosphorus.

When measured in the river, the existing concentration is .016 mg/L, well below the provincial limit of .03 mg/L. In what they call a “conservative approach”, Ainley proposes that the effluent be allowed to increase that concentration to .024 mg/L. If the target were even higher, it could mean less intensive treatment, or more homes being allowed on the system.

When measured in the effluent itself, the original strategy in the Servicing and Settlement Master Plan (SSMP) was to lower phosphorus by a moderate amount to meet the provincial standard. Total phosphorus in the effluent would have been .15 mg/L.

The new proposal is to use the best available technology to reduce phosphorus in the effluent to .046 mg/L, about one third of the previous level. This would translate to the target of .024 mg/L once the effluent was dispersed in the river. Ainley President Joe Mullan says this is the most significant factor in allowing for a higher population to be serviced.

The SSMP predicted a sewage flow of 2,610 cubic metres per day based on 6,000 urban residents. Ainley is now predicting 7,172 cubic metres per day for 14,559 residents.

River Flow

The Assimilative Capacity Study (ACS) in the SSMP came up with a river flow of 202 litres per second during low-flow periods. This measures the river’s ability to absorb effluent in the driest times, and is a major constraint.

A revised ACS done by Credit Valley Conservation, with updated river data, shows a low flow rate of 225 litres per second, 11 per cent higher than before. This could allow for less intensive treatment, or more new homes.

Water usage and infiltration

The SSMP used a water use projection of 435 litres per person, per day. (Water use equates closely to sewage generation.) This is considered very high.

Based on water use trends in the Town of Erin and a review of design standards in similar municipalities, Ainley is assuming a sewage flow averaging 290 litres per person per day. They’ve also included an additional allowance of 90 litres per person per day for possible “infiltration” – the water that often leaks into traditional gravity sewers, increasing the volume that a treatment plant must handle.

Lower water use per household, and possible reduction or elimination of infiltration, would both mean that more people could be on the system.

Not connecting some homes

Most residential properties in Hillsburgh and Erin village are too small for a normal, modern septic system, and so most neighbourhoods would be hooked up to a sewer system. But three areas with larger lots and newer septic systems could be exempt from having to hook up.

These are: the Upper Canada Drive subdivision in Hillsburgh, the Credit River Road – Pine Ridge Road area near the Tenth Line, and the Delarmbro Drive – Patrick Drive – Erinwood Drive area near Eighth Line and Country Road 124.

Not connecting these areas could free up sewage allocation for new subdivisions, though this might not be necessary since capacity is increasing due to other factors. In general, sewers cost less per household if the maximum number of residents are hooked up and paying a share.

Concerns about extra population growth with sewers

Concerns about major additional population growth in Hillsburgh and Erin village – above and beyond the 10,000 new residents already considered feasible in the next 20-30 years – were expressed at a public meeting last Thursday at Centre 2000.

It was a Public Information Centre hosted by the Town of Erin as part of the Wastewater Environmental Assessment, designed to update residents on current developments and provide an opportunity to ask questions.

 “Ensuring the community is both informed and engaged is an important component of this process,” said Mayor Allan Alls. “A sewage treatment plant will unquestionably move our community forward, allowing us to better address our tax imbalance, help our existing businesses, and bring new jobs to our community”. 

All of the information boards and slides presented last week are available in the Wastewater section of the Town’s website, erin.ca.

The project is now moving into Phase 3 of a 5-stage process that had its first public meeting in 2009. Town consultants The Ainley Group will now be exploring more detailed design alternatives, including options for sewage collection and treatment. The ideal location for discharge into the river, the treatment plant and pumping stations will also be analyzed. 

They intend to hold another Information Centre this November, and wrap up the entire EA in March next year.

Last week’s meeting focused on several environmental measurements and wastewater treatment factors, all of which affect how many homes could be serviced by a sewer system. (See article below for an overview.)

Actual decisions on population growth and approval of subdivisions will be made later as amendments to the Official Plan, but the capacity of the sewer system is a key element.

The current rural population of the Town is about 7,800 and expected to grow very slowly. The urban population is now about 4,500, and was previously expected to grow by only 1,500, to a total of 6,000. Recent changes to the proposed parameters have resulted in the growth projection over 20-30 years being revised to 10,000 new urban residents, for a total of 14,500.

This would allow for “full build-out” of lands inside the urban boundaries already designated for development, while still meeting provincial regulations for treated effluent entering the river.

Ainley Project Manager Joe Mullan said that BM Ross, the firm that conducted the Servicing and Settlement Master Plan, was “very conservative” in its proposed removal of phosphorus from sewage effluent. This was a factor in the 6,000 cap, which was vigorously defended by Credit Valley Conservation (CVC).

Mullan said that more aggressive treatment, accepted in the wastewater industry, could cut the total phosphorous by 70 per cent. This would be a major factor in allowing more population, but the strategy does not yet have provincial approval.

“It’s a very high quality effluent,” said Mullan. “This has been reviewed by CVC and the Ministry of the Environment and Climate Change, and I am quite confident that these numbers will be acceptable to those agencies.”

Jay Mowat, a member of the Public Liaison Committee and Transition Erin, noted that Ainley says it is still using “conservative” numbers. He asked how much population the sewage plant could actually handle, if the parameters were to change again.

“Could we be expecting 20,000 people, 25,000 people?” he said.

Mullan said even if there was a technical opportunity to handle more people, the treatment intensity could be cut back to conform to the current population projection.

If the County were to ask Erin to take 25,000 more people, Mullan said he didn’t think the proposed plant could handle it. But he could not give an actual maximum number, since the analysis has been focused on the current projection.

“We don’t want to get into the What If’s and What If’s,” he said. “This is a viable solution we are presenting to the Town that will allow you to make some serious decisions on your growth moving forward. We don’t want this to be your driver for growth. We want this to not be a constraint.”

Mayor Alls has been suggesting that rural residents of Erin should be expected to help pay for the cost of a sewage treatment plant, even though they would not get the direct benefit of sewer service and the higher property values that would result in urban zones.

In response to a question on this, Ainley Technical Team Lead Gary Scott said that Ontario’s Sustainable Water and Sewage Systems Act requires that the local cost of the sewer system and treatment plant (after any grants or developer contributions) to be paid by the residents who are actually hooked up to the system.

Rural residents will get some benefit, since the plant will be equipped to process septage – the waste pumped out of septic tanks. Currently, disposal firms charge to transport this waste to plants in distant locations such as Collingwood.

There is a risk that these plants could stop accepting the waste at any time, resulting in even higher disposal costs at more distant sites.

Hillsburgh sewage plant considered impractical

The possibility of building a sewage treatment plant in Hillsburgh has been rejected as impractical and too costly by the consultant conducting a Wastewater Environmental Assessment for the Town of Erin.

Joe Mullan, President of Ainley Group, presented a technical report to Town Council last week. He said there is insufficient data on the quality and quantity of the river flow near Hillsburgh to determine if treated sewage effluent could be safely discharged there.

Gathering the data for a new Assimilative Capacity Study could take 10 years and $500,000 – with no certainty that a Hillsburgh plant would eventually get provincial approval. Council requested the analysis last month, since the option had not be fully explored in the Servicing and Settlement Master Plan (SSMP).

Ainley is recommending that the Town stick with the original plan from the SSMP to have a single wastewater plant discharging downstream of Erin village. Council has made no final decision on this.

A Public Information Centre on the wastewater situation will be held on Thursday, June 22, at Centre 2000. It runs from 6 p.m. to 9 p.m., with a presentation at 7 p.m. It will describe the scope of possible work, and present the results of studies done so far – including alternatives not covered in the SSMP.

“The industry trend is towards less and larger treatment plants in order to reduce operational and compliance costs,” said Mullan.

Having two plants would save the estimated $5.2 million cost of a forcemain to pump Hillsburgh’s sewage along the Elora Cataract Trailway to the Erin village plant. But building two plants (for the full projected population increase) would cost $98.3 million, compared to $60.7 million for just one plant.

In addition, operation and maintenance costs estimated over 50 years would be about $75 million for a single plant – 32 per cent cheaper than for two plants.

“Subject to development of a cost sharing plan with developers, the full build out cost allocation to the existing community could substantially reduce the per capita cost to existing residents,” the Ainley report says.

Previously, growth within the urban areas of Hillsburgh and Erin was to be limited to 1,500 new residents – based on providing sewer service to all existing residents. As reported last November, a new strategy could exclude several areas from getting sewers. This would help free up capacity for developers, and could allow about 10,000 new urban residents over 20-30 years.

This is referred to as “full build out”, allowing housing growth in areas identified in the Town’s Official Plan. Council has been delaying a decision on exactly where new subdivisions will be allowed.

Subsurface wastewater option rejected

Erin Town Councillors still want to explore alternative technologies for Erin’s future wastewater system, but discharging treated effluent into the ground instead of the river will not be one of them.

They received a detailed technical report last week by engineer Gary Scott of Ainley Associates that says a subsurface disposal system would be impractical, risky and more costly than surface disposal. The analysis is backed up by Credit Valley Conservation and the Ministry of the Environment and Climate Change.

“It’s not competitive with surface water disposal and doesn’t give any cost advantage,” said Scott. Council authorized the investigation last year.

“The Master Plan had mentioned it, but subsurface disposal hadn’t been looked at in detail, so we have plugged that hole.”

This will avoid the possibility that the overall study could be challenged and delayed for failing to have studied sufficient options.

The projections are based on the possibility of “full build-out”, meaning that homes could be built over a 20-30 year period on all of the lands within the urban areas of Hillsburgh and Erin village that are already designated for that use in the Official Plan.

Current homes in Erin village would generate wastewater of 2,244 cubic metres per day (m³/d), but that could more than double to 4,767 m³/d. The Hillsburgh flow could quadruple, from 600 to 2,400 m³/d.

For a subsurface discharge bed, Erin village would need 40 hectares (98 acres), set back at least 300 metres from any creek or wetland. Such lands do not exist near Erin village, even if they could be purchased.

“The MOECC would likely require a spare bed,” said Scott. “There is a history of failure for subsurface systems in North America and Europe. The ministry is cautious in approving them.”

Hillsburgh would require a 19.5 hectare (48 acre) lot, which Scott say may be possible. But he said the costs of building and maintaining subsurface disposal in Hillsburgh, plus traditional river disposal in Erin village, are 10-20 per cent higher than pumping Hillsburgh sewage to a single treatment plant in Erin village.

Preliminary estimates (at full build-out) show the cost of treating waste at two separate areas at $71 million, compared to $61.7 million at a single Erin village site. That does not include the huge separate cost of building the collection pipe system throughout the villages.

Previously, new growth was expected to be limited to 6,000 residents. But a strategy suggested last year (but not yet approved by council) could see well over 10,000 new residents. Some existing neighbourhoods could be exempt from having sewers, and intensive treatment of sewage could allow for more effluent being allowed in the river.

Full details of the strategy are to be presented at a Public Information Centre (PIC). This has been delayed, and is expected this spring. The current phase of the Environmental Assessment is intended to research various practical options for collection and treatment of wastewater. 

With fewer children, Erin is stuck in the middle ages

The number of children living in the Town of Erin is at its lowest point in more than 20 years, according to 2016 census data released last week by Statistics Canada.

Although the town’s population rose 6.2 per cent to 11,439 from 2011 to 2016, the proportion of children aged 0-14 continued a long-term decline.

Back in 1996, Erin had 2,558 children, making up 24 per cent of the population. Now, we’re down to 1,750 children, making up only 15.3 per cent of the population.

By comparison, the national average for the proportion of children 0-14 is 16.6 per cent, while in nearby Georgetown, the proportion is 19.4 per cent.

The total number of children in Erin is down 6 per cent in the last five years, but it’s not as drastic as in the previous 5 years (2006-2011) when the decline was 15 per cent.

Within the 0-14 age group, Statistics Canada reports 450 Erin kids aged 0-4, 595 aged 5 to 9 years and 705 aged 10-14. If these numbers were to stay consistent, it would mean a substantially lower number of elementary school age children, since fewer young children would be entering the school system.

Among adults, Erin’s lowest population groups are ages 25-29 (490 people) and ages 30-34 (450 people). In contrast, the age 50-54 group has 1,275 people and the 55-59 group has 1,105 people.

The population is heavily weighted in the middle groups, with the number aged 35-64 totalling 5,475, almost half the total population.

The number of people in Erin aged 65 and older is 1,725, or 15.1 per cent of the population, which is also lower than the national average of 19.9 per cent.

Population growth in the urban areas of Erin village and Hillburgh is lower than the Town average of 6.2 per cent, meaning that most growth has been in the rural areas.

Erin village up is up 4.9 per cent to 2,647 people, in 1,011 private dwellings (845 being single detached homes). Hillsburgh is up 5.5 per cent to 1,124 people, in 430 private dwellings (365 being single detached homes).

Overall the Town of Erin including rural areas has some 4,100 dwellings, with 3,770 as single-detached homes, 80 attached homes, 150 apartments and 100 moveable homes.

The average household size is 2.8 persons. The breakdown is 635 dwellings with one person, 1,525 with two people, 725 with three people, 795 with four people, and 415 with five or more.

While the census has Erin’s 2016 population at 11,439, the actual number of people living in the Town is probably higher. Some people are normally missed in the census. For the 2011 census, Statistics Canada estimated the “undercount” at 4.1 per cent.

Erin population up

Erin’s population has rebounded after a drop reported five years ago, growing by 6.2 per cent to 11,439, according to figures released last week by Statistics Canada.

The growth rate is higher than the provincial average of 4.6 per cent and the national average of 5 per cent. The 2016 census counted 13.5 million people in Ontario and 35.2 million in Canada.

Initial figures show there were 4,108 private dwellings occupied in Erin, an increase of 9.8% from 2011.

When the 2011 census reported Erin with 10,770 residents, a decline of 378 (-3.4%) since 2006, it was the first population drop for village and township since the Great Depression.

More detailed statistics have not been released yet, but the trend in Erin has been a low number of seniors and families with young children, partly due to high real estate prices and relatively few new homes being constructed.

While the census has Erin’s 2016 population at 11,439, the actual number of people living in the Town is probably higher. Recently the County’s estimate for Erin’s population has been 12,365.

Some people are normally missed in the census. Statistics Canada has not yet published an estimate of the “undercount” for 2016, but for the 2011 census it was 4.1 per cent.

Wellington County is responsible for population forecasts, as part of the Province’s Growth Plan for the Greater Golden Horseshoe area. After adding the undercount, the County and Province use a Census Adjusted Population for their forecasts.

Since census statistics only come out every five years, the County tries to keep a more accurate estimate of the number of residents. In addition to the undercount, they have an in-house tracking system that includes building permit data to estimate the number of occupied dwellings.

 “A census release does not typically result in changes to an existing forecast,” said Mark Paoli, Manager of Policy Planning for Wellington County. “It is used as an input to the next forecast update, once all the information is released and our economists Watson Associates have reviewed and analysed all of the new data.”

The newly-published census population for all of Wellington County is 90,932, up 6.9%, while the County’s recent estimate of its own population is 95,805.

As part of the StatsCan website, the Focus on Geography feature compares Erin’s population growth to that of other municipalities.

Caledon’s published population has grown by 11.8% to 66,502. Orangeville is up 3.3% to 28,900, East Garafraxa down .6% to 2,579, Guelph/Eramosa up 3.8% to 12,854, Centre Wellington up 5.6% to 28,191, Halton Hills up 3.6% to 61,161 and Shelburne up 39% to 8,126.