A year-and-a-half after work began, the multi-million dollar reconstruction of the city’s east wastewater treatment plan is essentially complete.
Last week the city council approved a change order allowing for a short list of improvements from the original contract with Brockmiller Construction, general contractor for the sewer plant remodel and expansion. The changes totaled $73,563, bringing the complete cost of the work to $5,368,120. Even with two change orders during the process, it still constituted a savings of nearly $1 million from the original design engineer’s estimate of $6.2 million.
“There are just a few little items to be completed,” said Farmington Public Works Director Allen Welshon on Wednesday. “The majority of the changes were imposed by the city to make improvements from the original design.”
Welshon went on to say there was some additional work required because drawings from when the plan was built originally several decades ago were used as a basis for the expansion design. Once Brockmiller was well into the work they discovered that some of the hidden original design elements, such as some wiring, was left out during the original construction.
Even with a few details to still be wrapped up, the new equipment at the plan has been functioning for about two months now. The goal was to retool the plant to provide reliable service to a growing population on the east side of the community. The expansion increased the plant’s capacity from 1.3 million to 2 million gallons of wastewater per day.
The original plant was completed in 1989. Since that time the only oxidation ditch, the first major component in a sewage plant, had been full of sewage and running non-stop for the past 20 years. The recent improvements included adding a second oxidation ditch, this time with the latest technology available.
And aside from increased flow due to community growth, stormwater infiltration is a major concern for sewage treatment plants. In the perfect world, the only liquid to find its way to the sewage plant would be sewage. But in reality, many people and contractors have customarily routed downspouts and sump pump drains into sewage lines.
A third source of stormwater infiltration into sewer lines is through damaged or loose-fitting sewer mains. For the past few years the city has dedicated about $100,000 a year to video exploration and sealing of existing sewer mains in an effort to keep stormwater out.
While the oxidation ditches and other equipment is in place to handle the increase capacity, there’s still one element that must be added to meet federal guidelines. The city has until mid-2013 to add an “ultraviolet dissenfection” system to treat the already nearly potable water as it leaves the plant and enters the nearby creek. The decision was made to hold off on adding the ultraviolet system at this point due to budgetary concerns.
And even though the plant can now handle nearly twice the work load, Welshon said no additional manpower will be required for daily oversight. Part of this rebuild included eliminating an old control panel system for operator adjustments and implementing a new computer-based SCADA system similar to the one used in the city’s drinking water operations.
Sometime in the next few months the city will finish final grading around the plant and eventually install sod and grass seed when the weather is suitable for that work.
“The city is very happy with how the (expansion) work turned out,” Welshon said. “I give accolades to the designers and Brockmiller.”