Plans advance for new and improved wastewater treatment plant for Worthington
WORTHINGTON — The Worthington Public Utilities Water & Light Commission conducted its first public hearing via Zoom video Monday afternoon, though no one from the public took part in the virtual meeting to weigh in on plans to replace the city’s wastewater treatment facility.
The commission, which received a detailed report on the plans in April, is now moving forward in the process, with the hope of having the Minnesota Pollution Control Agency provide preliminary approval of the facility plan by the end of June. Construction on the estimated $20.5 million facility is slated to begin in the spring or summer of 2021, and will take two years to complete.
Kris Swanson, principal engineer with Bolton and Menk, said the city’s wastewater treatment plant, located south of the municipal airport, has aging infrastructure. Originally constructed in 1962, it has gone through three renovation projects — in 1983, 1989 and 2000, with the 1989 improvements being the last major upgrade.
Swanson explained that two options were considered by his firm — rehabilitating the existing structures with construction of a new biological treatment facility, or constructing a new suspended growth biological treatment system. With the current concrete silos already at the end of their useful life, and with future permit regulations likely to result in future upgrades that come sooner rather than later, he and WPU General Manager Scott Hain recommend new construction.
The project includes a new treatment for wastewater that will remove phosphorus and other harmful nutrients from wastewater before it is discharged.
“The process you use is not great at removing or controlling nutrients,” Swanson told commission members Monday, adding that with biological treatment, ammonia, nitrogen and phosphorus will be better controlled.
While costs for building new are about 20% higher than rehabilitating the existing plant, Swanson said it will be much cheaper over the lifetime of the facility. He also noted that the MPCA wants to make sure it is funding quality projects that won’t need to be changed or redone in the near future.
Based on the $20.5 million price tag, Swanson said the average monthly rate for homeowners ($31) would increase by roughly $20 per month. Hain, however, said that cost is with the assumption that WPU won’t use any of its reserve funds or receive grant funding for the project.
The intention is to apply for a Point Source Implementation Grant, which based on lower phosphorus limits could qualify the city for up to 80% coverage of eligible costs, up to a maximum of $7 million. Another option is to obtain a low interest loan (1% to 1.5%) from the state’s Clean Water Revolving Fund.
“The $52 (per month average) scenario I would consider to be worst-case scenario,” Hain said. “We do have a significant reserve built up.”
At this time, it hasn’t been decided if the new facility will be built north or east of the existing plant. Both parcels are city-owned, and building to the north would allow for less piping, Swanson said, and thereby reduced costs. The new construction isn’t feasible on the existing site because the wastewater treatment plant needs to continue to function during the construction process. The plan is to demolish some of the existing elements of the plant when the new construction is completed.
In other business, the commission:
Received conceptual designs for renovation of the Worthington Public Utilities shop, located north of the former liquor store on Diagonal Road. Hain is working with an architect from SEH Engineering on a design concept.
Most critical is replacement of the building’s roof, Hain reported, noting there was a lot of water running into the building during the weekend’s rains. He hopes the new roof can be completed before winter, while the remainder of the mostly indoor work to take place during the winter months.
An initial estimate of the renovations is $1,917,854, Hain reported, saying $250,000 of that is for the roof alone. Additional work will include replacing windows, doors and siding, as well as installing a brick accent wall on the front of the building, facing Diagonal Road.
Inside, there will be a mezzanine area with offices, renovations to existing restrooms, a new centralized lunchroom, water meter shop and utility room. Heating and air conditioning will serve the front portion of the building, and a $72,000 sprinkler system will need to be installed to bring the building up to code requirements.
“We’ve gone through a number of different concepts and whittled it down,” Hain said of the renovations. “It’s an old shop and needs some improvement.”
He told commission members the goal is to have final design and preparation for bid documents ready for an August bid letting. He’s hopeful the bids will come in “a whole lot less” than the estimate.
“We envision this as the long-term home of electric, water and in-town wastewater departments,” Hain shared.
Commission member Randy Thompson said the proposed improvements to the building will complement what was done with the former liquor store building.
Learned of the possibility that the city’s move toward biological filtration following the success of pilot and feasibility studies may be implemented sooner than expected.
Hain reported that dissolved oxygen levels are really encouraging, and the request has been made to convert to biological filtration before the final economic feasibility study is completed. That request has been sent to the Minnesota Department of Health for feedback. If MDH grants the go-ahead, Hain said WPU could convert to biological filtration within a month.
WPU Water Superintendent Eric Roos said it will take about eight weeks for the biology to take hold on the filters.
Will not take independent action on the proposed Dugdale housing project, as the plat approval will be considered by the city’s planning commission, as well as city council, and the city’s housing committee is also involved in the process. Water & Light Since commission members Chad Nixon and Thompson also serve on the housing commission, and Mike Harmon is a city councilman, they will be well represented in discussions at those levels.
The Water & Light Commission has already committed $1.5 million to the project. The construction timeline includes bid awarding in mid-August for assessable public improvements and developer-installed improvements, with site grading, utility and drainage construction to begin in September. Street construction is slated to begin in the spring of 2021.
As a result of COVID-19, Hain said he has not had a lot of time to work on a position description or consider advertising for an assistant manager/utility coordinator for WPU. The commission had previously budgeted for the position to begin July 1. Hain said the hiring will likely be pushed back a month or two.