Consultant: Bringing wastewater plant up to speed will be costly
May 3, 2016
Engineering consultant Jon Holland told the Sweet Home City Council last week that the city’s Wastewater Treatment Plant will require $20 million in upgrades.
With a phased approach, over the next 30 years, and counting inflation, those costs could reach $40 million.
Representing Brown and Caldwell Inc., Holland presented a new facility plan to the council during its regular meeting on April 24. He started with a little historical context.
For years, he told the council, the city has had its streets dug up, replacing sewer lines in four project phases in order to reduce inflow and infiltration during heavy rain storms.
Inflow and infiltration is storm water that enters the sewer system through deteriorating pipes and cross connections to storm drains. During heavy rain events, the storm water can overload the Wastewater Treatment Plant, forcing it to bypass the diluted but untreated overflow into the South Santiam River.
During storms, the plant has been subjected to flow rates of up to 22 million gallons per day, far beyond its capacity of 7 million gallons per day. The city usually produces around 1 million gallons of water per day.
The city has borrowed and spent $15 million on those projects over the past 16 years to replace sewer mains and lateral lines to residences, about a third of the system, significantly reducing the peak flows. That debt is a key component of the city’s sewer bills.
Today, the peak flow is about 12 million gallons per day, Holland told the council. “The number comes down a little bit at each phase.”
The best gains were during Phase I, with smaller gains in each of the three following phases, Holland said. Further sewer line replacement projects would not be cost effective in terms of I&I reduction compared to the cost – not when compared to upgrading the Wastewater Treatment Plant.
Holland said the city has three options: more sewer line replacement; a storage tank that impounds water for treatment following a storm; or upgrades to the treatment plant. Of the three, upgrading the plant is the most inexpensive. The first two options would cost about $28 million each.
Holland recommended a parallel treatment system that can handle flows above 7 million gallons per day, a maximum of 12 million to 13 million gallons per day, allowing some room for growth. The parallel system would kick in when needed to deal with extra flows from storms.
The project would include four phases that address other requirements and issues at the plant, Holland said.
The city could complete all of the upgrades early or it could phase them over the next three decades, Holland said. Doing it sooner would be the most inexpensive option because inflation will increase costs over time, but it would also drive sewer bills higher faster.
Holland will begin exploring financing options for the project and later return to the council with preliminary designs and then detailed design plans.
Going forward, he said, it’s important that the city continue to invest in its sewer collection system as well.
“You can’t stop forever working on your sewer system,” Holland said, adding that in a 100-year cycle, the city should probably spend about $250,000 per year on the sewer collection system.
Councilor Jeff Goodwin noted that the council will need to raise rates even higher to replace the system over time – and it’s not going to be politically popular.
“It don’t think we have a choice. It’s a bitter pill to swallow.”
The council voted 6-0 to submit the facility plan to the Oregon Department of Environmental Quality.
Present at the meeting were Mayor Jim Gourley and councilors James Goble, Jeff Goodwin, Bruce Hobbs, Dave Trask and Ryan Underwood. Greg Mahler was absent.