Avoiding wastewater woes
Big Sky’s water and sewer district looks into treatment plant upgrade options
In what turned out to be a five-plus hour discussion, the Big Sky County Water & Sewer District board of directors, led by consultant Scott Buecker, held a community meeting on Nov. 27 to discuss the brass tacks of the recently-completed wastewater treatment plant upgrade study.
The district’s current plant, a 14-year-old, sequencing batch reactor with zero liquid discharge, may not have reached its shelf-life as far as age goes—plants of that type last about 20 years—but as population and visitation continue to rise, the plant has seen recent water levels pouring in that bring it to its maximum functioning capacity.
In addition, the three ponds that store the treated wastewater coming from the plant also have been maxed out. Earlier this year the W&S department watched with bated breath as the storage ponds inched towards spillover by the spring of 2018. High visitation and precipitation were likely to blame.
But thanks to creative irrigation usage, which consisted of pumping 70 million gallons up to the Yellowstone Club, as well as more water later on to a previously unwatered area near the Big Sky Golf Course, that spillage scenario was averted. By the fall of 2018 the ponds had finally dropped to more manageable levels.
In fact it’s irrigation, namely of Big Sky’s golf courses, that keeps the wastewater retention pond system afloat, so to speak. And it’s not an easy task. It was noted at the Nov. 27 special meeting that in 2018, nearly 200 million gallons of treated wastewater was pumped 2,000 feet uphill to Big Sky’s private club courses—some of it via a 7.2 mile pipeline, charged at 450 PSI.
It was these max levels of input and output that motivated the W&S department along with its board to see what could be done differently, from treatment to discharge. AE2S Engineering of Bozeman was commissioned to perform the much-discussed study, which was released to the public in September.
Early in the public meeting, BSW&SD Board President Packy Cronin described the “why” of the study.
“We are at our capacity,” he said, noting the age of the current plant. “I imagine this effort is going to take a few years, which puts us up pretty close to that 20-year life cycle. I think the responsible thing to do is to stay ahead of the curve, and fine tune this now especially given the places we found ourselves in last spring, so improve our capacity and ability to treat wastewater.”
The chosen plant and its wastewater options
Buecker’s report looked at several types of wastewater treatment plants, as well as potential upgrades to the current system, but ultimately recommended pursuing a new system known as a membrane bioreactor, or MBR. As Buecker explained, this system was seen as the winner since it would double the capacity of the current plant, as well as fit within the restrictive location where the current system sits.
The MBR would also treat wastewater at a higher level, discharging treated water to the retaining ponds with nitrogen and phosphorus levels that would qualify the liquid for the EPA standard known as Class A-1. Big Sky’s current treated water qualifies as Class A, which means it can only be reused for irrigation, under the assumption the plants being watered would digest the unwanted nutrients in the water.
But a Class A-1 designation would open up a whole new world of treated wastewater reuse options—including the much debated direct discharge into the Gallatin River. That also includes the less-controversial option of snowmaking with the wastewater, as well as several other venues.
The board, Buecker and meeting attendees spent plenty of time discussing the reuse and discharge alternatives that come with the higher level of treated water the MBR would create, but as the meeting reached the four-hour mark Cronin and fellow board member Mike DuCuennois made it clear the first step, Phase 1, would be to simply get the MBR plant, with its Class A-1 wastewater in place, before the decision of what would be done with the water (Phase 2) would come to a decision.
“People need to understand this this is not a black and white, there is not going to be one disposal method chosen above all,” said DuCuennois, vice president of the Yellowstone Club. “We are going to keep irrigating our golf courses. I’m going for a snowmaking permit now. We are doing things as a district to treat water to make any or all of these options available. This is not a one-decision thing.”
The cost of the MBR is loosely estimated to be about $21.7 million for Phase 1. Just how that bill would be footed was addressed towards the end of the meeting by BSW&SD General Manager Ron Edwards. The district has already spent nearly $30 million on various wastewater treatment and drinking water upgrades using low-cost federal loans pegged specifically for water treatment infrastructure. These 20-year loans currently have a 2.5 percent interest rate.
Once the loan is secured via the Department of Natural Resources & Conservation and the DEQ, the BSW&SD will likely go to its users requesting a general obligation bond, as it has done in the past, but only if the voters approve the bond. This money would be collected through a mill rate increase. With users paying off of a 52.06 mill rate, the $21.7 million loan to cover the new plant would up that by 58.02 mills, effectively doubling the water and sewer tax rate.
Operating costs also come into play with the MBR plant—estimated at an uptick of nearly $1 million per year above current costs. That boils down to a hike in BSW&SD customers’ quarterly bills, with the sewer base rate potentially rising 60 to 70 percent.
However, that increase in taxes to pay for the plant would only be effective through 2023, at which time the BSW&SD’s two other loans will be paid in full. Even with that price drop on the horizon, the board wondered if its users would vote to approve these initial cost increases, however long they’d be around.
“There is a cost that goes with this. It’s very real, and it’s a big part of what needs to be looked at, and what the community is willing and not willing to do,” said Edwards, recalling success in past years with other similar efforts.
The aforementioned costs are assuming that the BSW&SD or some other source, like the Big Sky Resort Area Tax District, did not foot some of the $21.7 million bill.
“Everything we build is bigger than what’s needed for our resident population,” said Edwards. “And it’s because of that mountain… we have to build to take care of the demand that the mountain puts on it. So is it fair to have the residents subsidize that… knowing that the visitor impact is significant?”
With Edward’s point in mind, BSW&SD Vice President Tom Reeves continued the discussion.
“That’s the whole logic of resort tax,” said Reeves. “The logic is that you have an infrastructure base to support a much bigger population than the resident community.”
The lengthy, informational meeting was just that—informational only, and the board did not make any decisions as to how to proceed. Community input on the plan is still being accepted, and could help the board decide what they’ll ultimately pursue. To view the plan, visit www.bigskywatersewer.com and click on Helpful Links.