By Lauren Dorsey, Staff Writer
At the Jan. 16 Woodstock Selectboard meeting, engineers from Hoyle Tanner gave an in-depth presentation on the proposed renovations to Woodstock’s wastewater treatment facility. “Things are falling apart,” Woodstock municipal manager Eric Duffy told the Standard. “This is obviously a very expensive project, and I think we all understand the burden put on Woodstock taxpayers and residents. [We want to] explain why we have to do it.” Duffy also announced at the meeting that, contrary to prior interpretations, the town’s lawyers determined that Woodstock’s 1986 sewer ordinance allows the selectboard to require residents who are not hooked into the wastewater system to help pay for the upgrades, although the town has not yet decided how to distribute the cost. The town is scheduled to vote on a bond for the estimated $20 to $25 million project in November.
According to the presentation on the wastewater treatment facility, the plant has four areas in critical need of renovation: the headworks, the aeration tank, the effluent tank, and the disinfection tank.
The headworks, last replaced in 2006, removes grit and particulates from water entering the plant. “A headworks is an extremely corrosive environment,” said Kirsten Worden, the Hoyle Tanner technical lead on Woodstock’s wastewater project, during the presentation. “Hydrogen sulfide gasses come in from the influence sewer, which corrode metal conduits, the electricals, and paint. Everything is essentially starting to fall apart.” According to Worden, Woodstock’s headworks have already lasted nearly double their typical lifespan of about a decade.
The aeration tank, a steel tank where the facility adds oxygen to incoming wastewater, also needs repairs. “This particular structure is in very bad shape right now,” said Worden. “It has holes in some of the interior walls and support beams to the point where the operator isn’t 100% certain he can take one side down for cleaning without a catastrophic failure.” In addition, Worden said all of the interior metal components are at the end of their useful life, and the structure’s foundation has significant concrete defects that need attention.
The treatment facility has just one effluent pump station, which helps boost flow at the facility during floods and ice jams. “Everything always fails during an Irene,” said Worden, “so we need to replace that with a new piece of equipment and provide redundancy.”
The disinfection building suffers from a different set of problems. The top of the building is below the 500-year flood elevation line, which Vermont no longer allows, and the building cannot effectively accommodate Woodstock’s peak flows.
Although stormwater is not intended to flow to the wastewater plant, the treatment plant’s peak flows, typically in May, happen when rain and melt water errantly enter the collection system. “As you have aging infrastructure, you get cracks in the [concrete] pipes,” Worden told the Standard. “You get root intrusion, you have separations in the pipes, you get all sorts of things that can affect its integrity.” As a result, excess water seeps into the system.
Over the years, other, more explicit connections to the system may have also developed. For example, residents may have attached their sump pumps to the town line, or there could be accidental connections between stormwater drains and the wastewater system. Worden says that it can be difficult, expensive, and time-consuming to find and close these connections, and in the meantime, the plant must have sufficient capacity to accommodate the increased inflow.
Hoyle Tanner recommended that Woodstock seize the opportunity to change their disinfection system from chlorine to ultraviolet (UV) light. “We have to rebuild that whole chlorine contact tank anyway because we have to raise the walls [above the 500-year flood line], and we have to make it bigger to meet [peak flow] standards,” Worden said. According to Worden, while chlorine is a reliable disinfectant, it’s a hazardous chemical that can have dangerous consequences if mismanaged, including chemical burns or chlorine pollution in rivers. Although a UV system uses more energy, Worden estimates that the overall cost of operations would stay roughly the same because of chlorine’s high price tag.
The renovations would also help Woodstock comply with a new phosphorus requirement that Worden predicts will come from the EPA in the next few years, and it will allow Woodstock to connect as many as 500 more housing units to the plant, according to Duffy.
Worden noted that Hoyle and Tanner’s presentation about the plant was the first in a long line of public outreach that the town plans to do before the November bond vote. “Doing nothing is not an option,” said Worden. “It’s a public health hazard. In a worst-case scenario, the town could get an administrative order slapped on them with a compliance schedule that says, ‘Thou shall do this project.’ That’s pretty drastic, but I have done projects for [towns] who have been under administrative orders because their communities refused to pass bond votes.”
Worden noted, however, that the plant’s failings are normal for a wastewater treatment facility of its age. “The typical life of a piece of equipment and a treatment plant is about 20 years. If a treatment plant can squeak more life out of it, it’s because they have a very robust maintenance program and maybe the plant operators are continually going through and swapping out valves, rebuilding valves, rebuilding pumps,” said Worden. “Woodstock is doing all the maintenance that they need to do to keep that plant operating, and it operates well; it’s just that some of this equipment is well beyond what would be standard now.”