City well taken offline for treatment of bacteria, biofilm

The City of Rhinelander is operating with just two functioning wells after Well No. 4 was taken out of service in late June due to “increased bacteria and biofilm.” According to city officials, Well No. 4 was taken offline so that it can be rehabilitated, a process that is expected to last until the end of August.

Information on the status of Well No. 4 was included in the agenda and packet for the common council’s July 15 meeting, which was scheduled to take place after this edition went to press. The panel was scheduled to meet on Monday, July 8 but that meeting had to be rescheduled due to lack of a quorum. 

The agenda for the July 15 meeting included a resolution requesting that the alderpersons approve and accept a quote from CTW Wells and Pumps for the rehabilitation of Well No. 4 at a cost of $50,355. 

A July 9 memo from Curt Johnson, the city’s water/wastewater utility foreman, to city administrator Patrick Reagan further explained the situation.

“As we have discussed, I took Well 4 offline due to bacteria and biofilm,” Johnson wrote. “The Well needs a rehabilitation. Routine chemical rehabilitation has been the only way to maintain specific capacity. CTW Wells & Pumps will be contracted to do the rehabilitation, as they are very familiar with our wells and water system and have worked on all our wells. Well 4 has not been worked on since 2012.”

Well rehabilitation is common and should be done on a preventative basis, Johnson added.

While Well 4 is offline, the city will have to rely on Well 5 to pump to the city’s reservoir, he noted.

“This will add undo stress to Well 5 for the time being,” he wrote.

With No. 4 offline, the city has just two remaining wells in service — No. 5 and No. 6.

Wells No. 7 and 8, both located near the Rhinelander-Oneida County Airport, have been offline for approximately five years. The wells were taken out of service in the summer of 2019 after unsafe levels PFAS were detected. City officials have previously said the hope is the two wells will eventually be usable again, after they are treated to ensure safety, but there is no timeframe currently in place.

PFAS (per- and polyfluoroalkyl substances) are a group of man-made, fluorinated chemicals manufactured and used since the 1940s. Because they are designed to be stable and unreactive to water, grease, heat, and other elements, they don’t break down easily and are often referred to as “forever” compounds. 

Studies have shown a link between human exposure to PFAS and adverse health effects.

According to Reagan and Mayor Kris Hanus, there is no health danger to city residents or water customers as a result of the issues with Well No. 4.

“Wells 4 & 5 pump directly into the City’s reservoir, where the water is then treated prior entering the system,” Reagan explained. “Water entering the system has had no issues.”

Reagan also noted that the same rehabilitation procedure that will used for Well No. 4 was done late last year with Well No. 5 “and no problems were seen” during that procedure. “We do not foresee any with regard to this current rehabilitation procedure either,” he added.

Johnson’s memo includes an explanation as to the impact of bacteria and biofilm on wells.

“In water, bacteria are either free swimming (planktonic) or they are attached to a surface (sessile),” he wrote. “With regards to biofilms, we’re primarily interested in the latter, as it is through the extrusion of a slimy polysaccharide exopolymer bacteria produce when attaching themselves to surfaces that the building blocks of biofilm are formed. While this lifestyle may be enjoyed by the bacteria, it can become extremely problematic for well owners. As the growth of biofilm progresses and more bacteria join the party, the mass of the film expands and can become quite detrimental to water flow in a well as pathways become more and more restricted. Also, the same sticky characteristics of the slime that aids in surface attachment and nutrient capture is also an excellent source for the development of mineral scale within a well system. As bacteria exude this slime, a suburban community is formed where bacteria can propagate, capture needed nutrients, and gain protection by creating a barrier between themselves and external influences, such as disinfection efforts. Biofilms promote scale buildup by providing an excellent surface for adhesion of mineral-forming ions, further complicating well operation. Similarly, fine-grained sediments and debris, mobilized toward a well during operation, often become entrapped in biofilm, increasing the fouling potential. These surfaces can be screen or casing, pump components, gravel pack material, or the surfaces of the minerals which make up the aquifer formation.”

While the city has committed to digging a new well — to be designated as Well No. 9 — it will be a few years before that well is online, Johnson noted.

He also noted that there is a marked increase in water usage during the summer months.

“Summer months more water is pumped due to industrial use as cooling water, irrigation systems, car washes, future hotels and more tourism,” he wrote. “We are not in a great situation with Wells 7 & 8 offline and Well 9 will not be online for a couple years. The DNR is aware of our capacity issue and has given us lenience on hydrant flushing, as we did not flush for two years and tried last year but could not keep up with water demand. Same goes for when fire department pulls off hydrants for a fire, we struggle to keep up with demand. This could be a real issue if a fire suppression system ever went off in a building and fire departments were also pulling off hydrants, we would drain the water system real fast and not be able to supply enough water.”

When asked if last week’s Hodag Country Festival, which draws thousands to the Rhinelander community, might negatively impact the city’s water system, Reagan assured it would not.

“They are not on the City’s water system so we do not see an issue with this event taking place with regard to the City’s water supply,” he wrote, adding that city staff will continue to closely monitor the water supply as it does on a daily basis.

“For a typical use of water there is not much concern,” Hanus said. “If we were to have multiple water main breaks and or the need to use the water system only to fight a major fire, then the system would be strained. The odds of that are unlikely but we have plans in place for such events.”

Heather Schaefer may be reached at [email protected].