Molder points to the primary digester cover that needs replacing
At a work session Tuesday evening, the Gillette City Council decided to move forward with plans to procure funding to bring the city’s Wastewater Treatment Plant (WWTP) into compliance with federal and state clean water treatment guidelines with an estimated price tag of $20 million. They have roughly five years to complete the updates before some of the plant’s major machinery suffers irreparable damage.
“The life expectancy for new treatment equipment is about 15 years. Most of the equipment that is out there is around 30 years old,” City of Gillette Utilities Director Mike Cole said. “It’s definitely showing its age.”
Currently, the council is exploring the possibility of securing either a Clean Water State Revolving Fund (SRF) loan through the federal-state program or a Wyoming Capital Construction loan to pay for the project, with municipal bonds as the next option.
Recent attempts by the city to gain state grant funding and forgiveness loans were both unsuccessful, Cole said.
The council rejected the ideas of using Optional 1% Sales Tax funds, putting a project-specific capital facilities tax up for vote, or immediately raising sewer rates to generate the needed revenue. However, council does anticipated needing to raise utility rates in the near future to accommodate improvements down the road.
The wastewater plant’s conditions were not a shock to council. In 2018, the city had hired HRD, an engineering and design firm, to perform a condition assessment, and those findings were presented to the council in May of this year. They’d also recently toured the plant on Garner Lake Road to view the primary problem areas, including the headworks, ultraviolet (UV) disinfection, centrifuge, digester and energy buildings, and general site improvements.
According to city Wastewater Services Manager Bob Molder, the headworks area is the number one priority as the system, which processes approximately 3.2 million gallons of waste each day, has already failed. Only one of the two mechanical rake machines is currently operational and must rely on parts from the other to process the incoming flow. He was forced to have custom parts made for the rake system, but it can take up to 16 weeks for delivery.
He used to be able to find parts from online resellers, yet now many of the machines are obsolete, he said, noting that one company even laughed when he called to order specific parts.
“We’re doing everything we can to make it last and operate efficiently,” he said.
The primary clarifiers, also part of headworks, slow down and allow for the separation of the materials coming into the plant, and are also aging as the original gear boxes date back to the mid- to late-80s, according to Molder.
The domes over the two clarifiers, which were added in 2006 as part of an unfinished expansion plan, are now trapping too much gas, damaging the equipment, he added, and need to go.
These repairs alone are estimated at $8.1 million.
Another problem area is the UV disinfection unit that has an estimated two to three years of life left, Molder told the council. Water passes over the bright green UV lights of the unit and sterilizes any live organisms in the water, so they cannot produce diseases, he explained. He hopes to add a redundant unit within the next two years before decommissioning and replacing the one currently in place.
The cost to replace equipment in the UV disinfection area is estimated at $2 million.
Another high priority is updating the centrifuge, or dewatering unit, that processes 100 gallons a minute of sludge, which is a sewage by-product. This unit is due to hit its 20,000-hour use mark in a year or two, Molder said. When it goes down, it can disrupt the entire plant, and that’s something that he and others don’t want to see happen.
The cost to decommission and replace the centrifuge unit and add an additional unit is around $1.5 million.
The digester and energy buildings also require updating.
The current 30-year-old sludge thickener, which processes 100,000 gallons a day, needs to be replaced and a backup system is needed.
Last summer, an unplanned repair came as a shock, Molder noted, when it was discovered that the primary digester cover needed replaced at a cost of over $1 million due to gases deteriorating the metal from the inside, leaving hand-sized holes.
Molder gives the unit around two years, but he said it becomes an emergency situation if it fails since the gas must be cleared out and the area kept both safe and clean. He noted, there’s a secondary unit that’s currently fully operational.
The waste gas burner, boiler, plant piping insulation, and several valves and pumps, along with the HVAC system, also need replacing.
“All of the HVACs have been replaced once in the 30 years that I have been here, and it needs it again,” Molder said.
The cost of replacements to the digester and energy buildings will run about $2.4 million with another $3.6 million needed for general site improvements, including the installation of a scale house, paved access road, concrete aprons for compost and other miscellaneous projects.
A tarp with tape currently covers the plant’s main power unit, which also needs about $2.4 in improvements, including replacing the underground electrical, switchgear, transformers, underground piping, and other equipment as well as purchasing emergency back-up generators.
“It’s getting to the point where we have some unsafe conditions,” Molder said, adding that the crew is currently being instructed to stay out of this area as electricians have to work in special suits when opening the panels that contain these 30-year-old components.
Funding for the wastewater improvements will be discussed at the Jan. 28 council work session on enterprise funds for wastewater, water, electrical, and solid waste, which is held annually, according to City of Gillette Communications Manager Geno Palazzari. He added that this is where any potential utility increases are likely to be determined.
The council mentioned that once funding for the priority needs have been secured, a long-term wastewater reserve fund might be something worth looking at in the future to assist in upcoming improvements that may arise.