What is the capacity of Revelstoke's sewage treatment plant?
That question has been on people's minds as the city has grappled with odour issues, and as a proposal has come forward for a 1,200-unit development in Arrow Heights.
Is the development of Revelstoke Mountain Resort and the increase in tourists and ski bums taxing the wastewater treatment system? Can the treatment plant handle an influx of new development, and even more waste?
Mayor Mark McKee attempted to address those questions at the end of last Tuesday's council meeting.
"Our recollection of previous reports puts it around 9,000 users," he said. "We estimate we have 5,000 people using it now."
End of story. Or not.
It turns out the answer is a little more complicated than saying the sewer system is processing X, and can process up to Y.
To find out I called Mike Thomas, the city's director of engineering. He didn't have a straight answer for me, but did point me in the right direction. “There’s a whole box of sewer reports in my office and they’re on the list to go through,” he said.
He e-mailed me two of those reports — Stage One of the Liquid Waste Management Plan (LWMP), and a draft of Stage Two. They can both be found at the end of this article.
Unfortunately, there's no simple answer to the question of capacity. Nowhere in 362 pages of documents did I find a sentence saying, "The capacity of the Revelstoke wastewater treatment plant is X." That would have made my life much easier.
The city's sewage system (note: I used the terms sewage and wastewater interchangeably) goes back to 1905. That's what I found out by reading Stage One of the LWMP, which was prepared by the engineering firm Dayton & Knight. The 272-page document was completed in 2008 and marked the first step the city took to addressing the long-term needs of its sewage system. Stage Two has been sitting in draft form since 2012 and Stage Three, which is supposed to provide more detailed costs and an implementation schedule, hasn't even been contemplated.
According to Stage One, the first elements of Revelstoke wastewater collection system were constructed in 1905. For decades, the city pumped untreated waste directly into the Columbia River at various locations throughout the city. In 1973, all the disparate elements were connected and sent to the Downie pump station, and then discharged, without treatment, into the river. The treatment plant wasn't constructed until 1975, and has been upgraded several times since then.
In 2008, the plant was servicing about 6,400 people. Most of the city is connected to the system, though some 2,000 people in the Big Eddy and Arrow Heights are not. The LWMP says the plant can service a population of about 8,500 people. It was researched and written at a time when development of RMR was just underway and growth was expected to boom. The plan forecast a city service population of 9,666 people (including seasonal residents) by 2015, with another 3,851 people staying at RMR.
Stage One presented several options for upgrading and expanding the system, while the unfinished Stage Two provides more detailed steps for the preferred choice — upgrading the current system. The LWMP says the plant can be upgraded to handle the entire city, including the Big Eddy, Arrow Heights and RMR.
Of course, things haven't gone as planned. Permanent population has stagnated, or at best only grown slightly. The 2013 Integrated Community Sustainability Plan says Revelstoke's total population peaks at about 13,000 at the busiest time of year. That figure includes the regional district, tourists and seasonal residents. The actual number using the sewage system during a busy weekend is a few thousand less than that, but almost certainly more than the 5,000 Mayor McKee estimated.
We can get a rough idea of the number of users, but what about the plant's capacity to handle all those flushing toilets? Turns out, it's a little more complicated than just counting people. When I spoke to Mike Thomas, he said the plant's capacity is actually reflected in its ability to process all the waste.
"In terms of actual capacity, the data is we’re meeting the effluent requirements set by the Ministry of the Environment," he said. “That really determines the capacity of the plant — we need to work out at what point would we not be meeting those effluent requirements."
PHOTO: The sewage treatment plant features two open-air lagoons that use a bubble diffuser system to treat waste. ~ Revelstoke Review file photo.
Let's pause here for a second for a brief explanation of how the sewage system works. Essentially what happens is a network of pipes and pump stations brings wastewater from all over town to the treatment plant in the industrial park.
Once there, it is screened in the headworks building. It is then pumped to one of two lagoons, which use a bubble diffuser system to add oxygen to the waste. The solids then break down so they can be filtered. After the waste goes through the lagoons, the effluent is chlorinated, then de-chlorinated and pumped into the Illecillewaet River.
The Ministry of the Environment puts rules on the quality of the effluent. For example, it can have a maximum biochemical oxygen demand (BOD) of 45 milligrams per litre. BOD is one of those scientific terms that's really difficult to explain, but generally, the higher the BOD, the faster oxygen will deplete in a stream, which is bad for the environment. The ministry also regulated the level of total suspended solids (TSS). Thomas didn't have the current levels of TSS and BOD immediately available, but said they are reported monthly to the Ministry of the Enviroment, and that they don't exceed the maximum allowed.
The other limit the ministry sets is the daily discharge of effluent. Stage One of the LWMP says the city is allowed to discharge a maximum of 4,152 cubic-metres of effluent per day into the Illecillewaet River. It also shows that over seven years, from 2000 to 2006, inflow of wastewater to the plant averaged just under 3,000 cubic-metres every day, but peaked at more than 6,100 cubic-metres. This was at a time when the service population was about 6,400 people. Peaks are due to storm water infiltration into the system, which the city is spending $40,000 per year to address.
If the average inflow is lower than the maximum allowed outflow, the plant is doing OK. You can look for ways to maintain the quality of the effluent in order to meet regulations. The mixers that were installed last week might help with that, said Thomas.
“You look at the average flow in, the total volume of the plant, how much air you can put in, and you look for efficiencies in that," said Thomas.
PHOTO: City of Revelstoke public works' personnel unbox new mixers that were installed in the first lagoon on the weekend. ~ Photo by the City of Revelstoke
The purpose of the LWMP is to set out a path for the city to upgrade the wastewater system to handle forecast increases in population.
Stage Two of the plan presents the upgrades required to meet population growth. It was started in 2008 and a fifth draft was produced in 2012 before falling on the backburner. It calls for more than $25 million in capital spending to service a population of 13,500 people. On the collection side, that figure includes about $1 million to replace the Downie force main, and $6.7 million to connect RMR and Arrow Heights (the trunk main and lift stations to that part of town were completed in 2009).
On the treatment side, it calls for $8.6 million in upgrades to the sewage treatment plant. Many of the upgrades involve converting to a mechanical plant from the current aerated lagoon system. The current financial plan budgets $1.2 million for treatment plant upgrades in 2019.
The plan also gives two options for treating the effluent — one is pumping it to the Columbia River and the other is adding a filtration system to the current discharge pipe. The former is more expensive in the short term but cheaper in the long term.
During my conversation with Mike Thomas, one thing became clear — a lot of this is uncertain. The first work on the LWMP was conducted prior to Revelstoke Mountain Resort being developed. It was based on population forecasts that haven't materialized; the growth of the resort is dramatically less than expected.
A lot of questions I had for Thomas were ones he couldn't give a direct answer to. They were still questions he needed to answer himself.
"You don't want to be blind to something that might be an obvious problem. You’ve got to keep your mind open as to what might be the cause," he said. “Things we thought were problems are not problems, and other things we’ve still got questions on. I'm hopeful we'll have some good answers on this odour side here shortly, and definitely the capacity question.”
The population question is one the planning department will be looking at. They will also look at the amount of industrial and commercial use. What's the impact of the proposed Mackenzie Village development, Downie Timber going to three shifts and the Mount Begbie Brewery expansion? Those are questions Thomas wants to answer before moving forward with any developments. “This stuff fascinates me, it really does," he said. "This is that long-term infrastructure planning stuff I need to do way more often because too often I’m dealing with the operational stuff.
"An environmentally, socially and economically sustainable path forward for the city’s sewer treatment is a high priority for me," he added.