SAXTONS RIVER — A process that uses ultraviolet (UV) light instead of chlorine chemicals to treat wastewater before it enters the Saxtons River is being considered as the least expensive option for the village's treatment plant upgrade.
About 250 Saxtons River households, plus Vermont Academy, use the wastewater treatment system, which has been online since the early 1970s.
Experts say the facility needs to be either upgraded or replaced. An evaluation of the plant in 2007 found the plant to be nearing the end of its useful life.
Currently, according to the handout from the Trustees at the meeting, the plant is now in poor condition and needs to be upgraded to ensure waste water is adequately treated.
Several options were compared, but it was the UV alternative that made the most sense, Trustee Ben Wallace told village residents at a meeting last Saturday.
Now, the trustees wanted to know which of the alternatives the public liked.
The trustees paid $11,500 to the Bellows Falls engineering firm Marquise & Morano to prepare estimates and then to present the alternatives to the public. The village received a loan from the state to cover the plan, which will be repaid by village sewer fees.
The plan outlines three minimum upgrades to the current plant.
The first uses the current treatment process with an upgrade that would cost $3,057,210, with an annual operating cost of $96,297.
The second, the one that the trustees recommended, would install a new treatment process using sequencing batch reactors (SBR), at a capital cost of $2,439,382, and an annual operating cost of $89,989.
The third option would be a conversion of the treatment plant to a pump station, an idea the trustees had considered but abandoned, mostly because of cost.
The capital cost for the pump station option would be $3,317,032, with an annual operating cost of $134,181.
As the potential engineering contractor who would oversee the project, Gary A. Leach, P.E., of Tata & Howard of St. Johnsbury, presented the SBR alternative as the most viable fix for the village.
Higher fees
Current user fees average about $1 a day per household, at $385 a year. Under the scenario recommended by the trustees, those fees would almost double to $722 a year.
While no one objected to the higher costs for residents at the meeting, Wallace responded to requests for staggering the billing of property taxes and waste water user fees so they did not clump together, saying he did not see why that could not be arranged.
One of the main features of the recommended alternative is the use of ultraviolet light as a disinfectant, rather than chlorine, which is used currently. UV disinfectant eliminates any chance of chemicals entering the stream through the outlet line.
Disinfection is considered to be the primary mechanism for the destruction of pathogenic organisms to prevent the spread of waterborne diseases to downstream users and the environment.
In 1999, the EPA described advantages of UV as disinfection of most viruses, spores, and cysts.
The process eliminates the need to generate, handle, transport, or store toxic, hazardous, or corrosive chemicals. It has no residual effect that can be harmful to humans or aquatic life, and it is also user-friendly for operators.
UV disinfection has a shorter contact time when compared with other disinfectants (approximately 20 to 30 seconds with low-pressure lamps), and UV disinfection equipment requires less space than other methods. Because of the shortened processing time, the new facility could handle nearly 100,000 gallons a day.
The lower elevation of the plant, according to Leach, would only improve the site line to the river.
Conversion to the SBR facility would not require any shut down time of the current facility, and “flipping a switch” when the time comes is all it would take to bring it online, Leach said.
Leach explained the existing oxidation ditch would be filled in, the control building and sludge holding tank would be slightly expanded.
A generator would be added for continuous operation during a power outage and sit above the tanks and the current ditch, and the 20 foot deep concrete tanks would rise some 15 feet above the 500 year flood mark, having been sunk 7 to 8 feet into the ground.
The facility was offline and under about 5 feet of water during Tropical Storm Irene in 2011.
Some residents expressed concerns about oversight of quality control of the concrete from which the plant would be built, as that would greatly determine the estimated 50-year lifespan of the proposed plant.
Wallace and Leach told residents that the facility would be completed in three steps, in which “the state has already been included” to this point.
An engineering study needs to be submitted to and approved by the state, which will consider whether the design is sound and whether this option would represent the lowest cost for the village.
The second phase would be to get a final design approved, and the third phase would build the facility.
Leach recommended that voters approve 10 percent more than the cost estimate to ensure adequate funding, noting that costs could come in under the estimate as well, and the money would not need to be spent.
He noted that cost estimates would be refined throughout the process.
Village Trustee Louise Luring told residents any approval of grants from the U.S. Department of Food and Agriculture to cut the bond costs was contingent on census surveys of village user incomes.
At present, the census data show that the village is too wealthy to qualify for the program.
Luring and Wallace said they would be getting a new survey done, as they questioned that outcome. But according to a Vermont Academy attendee, their surveys showed an income level jump in the last year.
The trustees said they planned to put the bond vote before the voters at the April 4 village meeting.