Sewer plant expansion cost in millions
July 22, 2015
Estimates for the cost of work on the North Valley Wastewater Treatment Plant range from $3.13 million to $8.49 million.
But between $2 million in cash reserves, and the expected pay-off of some of the plant's debt, county officials hope to minimize the impact on ratepayers.
"We have sufficient cash flow due to future debt retirement that can fund a significant portion of the projected costs," Douglas County Public Works Director Carl Ruschmeyer said. "Overall, it is our goal to develop a financing plan that will fund the improvements with no impact on our ratepayers."
Douglas County commissioners heard a half-dozen options last week at a workshop on the plant.
The plant has a capacity of 300,000 gallons, and is treating 250,000 gallons per day, which is 83 percent of its capacity.
Under its license with the state, there must be a plan to expand the plant when it reaches 85 percent.
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The plant is expected to exceed its capacity in 2018.
Depending on rate of demand over the next 20 years, the plant could go from an upward capacity of 450,000 to 630,000 gallons per day.
The least expensive alternative is also the most expensive in cost per gallon, and only increases capacity by 50,000 gallons per day, well short of the plant's target of 630,000 per day.
That means the plant would reach 85 percent capacity in 2018-2020.
Of the options that increase the plant's capacity, converting it to a two-cell sequencing batch reactor has the second lowest capital and lowest per gallon cost. That process would cost roughly $6.9 million and carry the plant through 2030. Those estimates don't include life-cycle cost analysis, which could change depending on the maintenance demands, Ruschmeyer said.
"The final selection will be based on the life cycle costs which includes the capital cost and also considers other non-economic factors," Ruschmeyer said in an email on Tuesday.
County commissioners are expected to hear the final alternative analysis and funding options at an Aug. 6 workshop. An alternative is expected to be presented for county commissioners' approval on Sept. 3. Work could begin in October 2017, with plant start-up a year later in 2018.
Built in 1988 to serve the industrial areas around Minden-Tahoe Airport, the plant was originally designed to treat 125,000 gallons a day.
Sewer ponds and the plant were the subject of $1 million in work in 2007. Another $5 million in work was needed on the plant, but the Great Recession reduced demand and connection fees to expand it.
Most Valley residents are served by the Minden-Gardnerville Sanitation District, which declined to take over sewage treatment from the county, but might be willing to take a portion of the county's effluent for treatment.
The sanitation district provides treatment to more than 9,000 accounts between it and the Gardnerville Ranchos General Improvement District, which purchases sewer capacity.