For the second time in recent months, a manure digester facility just north of Waunakee, which serves three dairy farms, has experienced a leak.
This one, which happened Jan. 20, leaked only about 20,000 gallons, which was contained in a retention pond on the bio-digester site in Dane County's Town of Vienna.
It occurred when workers at the Clear Horizons facility were on site and able to quickly handle the problem with a broken pipe.
A manure leak Nov. 24 was not contained so quickly because it happened when no one was on duty at the facility. At that time 300,000 gallons of waste reached Six Mile Creek, which is part of the Lake Mendota watershed.
During that first spill, a pipe at the facility ruptured and allowed manure to run from 11 p.m. until the next morning when a worker arrived on the site. Managers said at the time that alarms that were intended to alert them to the problem, failed to work.
The digester is Dane County's first, highly touted "community digester" built in the middle of the three farms and owned and operated by a third party — Clear Horizons. It is intended to keep phosphorus out of the watershed while maintaining the ability of dairy farmers to continue to operate their farms.
The bio-digester was built to produce enough "green" electricity to power as many as 2,500 houses.
The Clean Lakes Alliance — a non-profit groups that bridges the interests of farmers with business and government regulators — said it is proud of the collaboration that has made possible the addition of manure digesters to the county's efforts to clean up the lakes.
"As such, it is disheartening to face the setback caused by the recent spills at the area digester, especially amid the progress made and the momentum generated by innovations in manure management," the non-profit group said in a statement.
But the group said it "reiterates its stance that digesters can provide an effective means to manage manure and reduce unhealthy phosphorus concentrations in our watershed; however, it is imperative we apply the lessons learned from these accidents."
"We have been assured that additional safeguards are in place at the new digester in Middleton, and we add our voice to the call for upgrades and fixes at the Waunakee facility. We encourage the Department of Natural Resources and Dane County to continue to investigate what went wrong, oversee the solution, and enforce as necessary.
"More alarms and safety valves, installation of secondary containment measures, such as earthen berms and storage lagoons, and the establishment of emergency preparedness plans and protocols are needed, and we urge Clear Horizons to move quickly. We cannot play Russian roulette with our lakes; the gamble is too great," the Clean Lakes Alliance added.
The first spill was met with quick action from the farmers and digester operator and effective remediation limited the phosphorus loading to the lake at only 30 pounds. The latest spill was contained completely on site and didn't reach waterways.
County Conservationist Kevin Connors said that during the three-day period after the spill a monitoring station picked up that 30-pound phosphorus load. But in a heavy rain event last March, the same station detected 4,400 pounds of phosphorus, he said.
By comparison, the spill was relatively minor in terms of phosphorus loading to the water body.
During the first spill, manure covered the facility's parking lot until the employee got to work that next morning and shut off a valve to halt the flow. The next step was to invoke the company's manure spill plan, which resulted in farmers spreading manure on area fields.
The large spill happened as the county was preparing to fire up its second digester in the Town of Springfield. The county board was also poised to approve a third bio-digester in the Town of Bristol, but sent the proposal back to a committee for more study.
That Springfield digester went on line — to minimal fanfare — less than a month after the large spill at the Waunakee digester.
The second digester, which will also process dairy manure from three area farms, is operated by a different party, Gundersen Envision, a division of Gundersen Health Systems, a health-care operation that has set its sights on producing green energy in a variety of ways.
Officials there said their system is different from those at the Clear Horizons facility and that there are redundant alarm systems in place to prevent such spills. The Gundersen company has partnered with U.S. Biogas to operate the plant.
The newer plant was also built with a containment berm to hold 110 percent of the capacity of the digester in case of a leak. A lagoon with capacity of 15 million gallons is also built into the design capacity.