A Dane County biodigester that holds millions of gallons of animal waste was built without a containment berm encircling an above-ground pipe that burst last month and let loose one of the largest Wisconsin manure spills on record.
It was the second 300,000-gallon release this year at a manure storage facility with no berm to hold all the spillage, no employees on duty to notice the rupture and no automated shutoffs or alarms that worked.
Both spills happened at night, so manure spewed for hours until employees came to work in the morning, and the waste spread until it entered waterways that flow into Madison’s chain of lakes where farm runoff is already the major source of excessive, smelly weed and algae growth.
State regulations don’t specifically require berms or automated safeguards, but the two spills will prompt a reexamination of standards, said Pat Murphy, the U.S. Department of Agriculture’s resource conservationist for Wisconsin.
“We’ve kind of entered into a new phase, and this is just emerging as an issue,” Murphy said. “There’s a little bit of a learning curve going on.”
Great quantities of manure have become more concentrated geographically with the rise of larger dairy farms, Murphy said. Farmers spread it on fields as fertilizer, but it can’t be done year-round, so millions of gallons must be stored — pumped through pipes into lagoons or tanks, or sent for processing at biodigesters — creating new hazards when a system fails, he said.
“It creates a whole new category of opportunity and risk,” Murphy said. “The ultimate answer is cost. You must do things in the most cost-effective method for the businesses.”
While building berms could be costly, simple shutoff devices and alarms aren’t very expensive, said Rebecca Larson, a UW-Madison biosystems engineering professor.
“Much less than the cleanup cost, I’ll tell you that,” Larson said.
Still, when experts from the USDA, the university, the state Department of Natural Resources and others come together to discuss changes, they weigh benefits of any change against the cost, especially to small farmers, Larson said.
The DNR can require containment berms or monitoring of leaks or groundwater contamination in certain cases — even automated shutoff valves — but it relies heavily on the skill and integrity of private engineers who submit plans before a project is permitted, said Mark Cain, a wastewater engineer for the agency who helps write the rules, issue permits and oversee cleanups.
This year Cain was assigned to oversee cleanups of two of the four largest manure spills in the last 15 years — at the biodigester site near Waunakee last month and at UW-Madison’s Arlington Agricultural Research Station in February.
Cain said once the latest cleanup is complete, he and others at the agency will talk about possible changes in anti-spill measures.
Two of the biggest
Three 1.25-million-gallon digester tanks have generated electricity from methane released by farm manure since 2010 at the Clear Horizons facility north of Waunakee. A protective berm surrounds the digesters.
But the Nov. 24 spill occurred 200 feet outside the berm where a section of pipe emerges from a pump house and runs about three feet down through insulated housing and then into the ground, said Monte Lamer, assistant plant manager. The pipeline continues underground to the digester.
A pump usually pushes manure through the pipe to the digester tank, but after the short, above-ground pipe section ruptured around 11 p.m., the material washed back out of the tank, Lamer said.
For roughly six hours, until an employee arrived for work in the morning, the manure drained onto the ground. As much as half of it pooled in a low area designed to capture and filter stormwater, Lamer said, but the rest flowed off the site, finding a series of ditches that carried it more than a mile. Some ended up in Six Mile Creek in Waunakee.
The company is investigating why the pipe burst and why an alert system failed to notify off-duty workers through their cellphones, Lamer said.
At the university agriculture station about 20 miles north of Madison, at about 3 a.m. Feb. 5, a fitting failed on a pipeline that carries manure-laden water from a storage lagoon to a dairy barn, where it sluices more manure into another line back to the lagoon, said Richard Straub, a dean at the UW agriculture college.
By the time an employee appeared for work about three hours later, the waste had spread toward the Yahara River. Barriers were set up, but in the days that passed before the manure could be collected, rain and snowmelt washed an unknown amount into the river, Straub said.
The farm responded by building a berm that would channel any future spill into the lagoon and by installing a $3,000 automatic shutoff valve, Straub said.
No fish kills were reported with either spill.
On farms, manure is typically pumped by pipe to a storage tank or pit until the fields are dry and thawed enough to absorb it.
Manure digesters not only generate electricity, they also can reduce the volume and nutrient level of the material so that when farmers apply it as fertilizer it causes less harm if it runs off fields into lakes and streams.
Digesters are usually equipped with sophisticated sensors and controls and are managed more closely than typical storage structures on farms, said Larson, the UW-Madison agricultural engineer.
Steven Sell, an engineer at BIOferm Energy Systems in Madison, said three biodigesters the company has designed in Wisconsin are equipped with a variety of sensors, including some that send cellphone messages if something needs attention.
The measures are designed to prevent costly downtime, Sell said.
Many types of spill safeguards may be available, but costs may not be justified, said Stephen Dvorak, whose Chilton-based DVO Inc. has designed and built digesters in 16 states.
“Whether you can remove that risk 100 percent, that’s not easy to do,” Dvorak said.
Jim Ditter, CEO of PPC Partners, which owns the Clear Horizons biodigester near Waunakee, said the company won’t make any decisions about additional safeguards until it is sure about what went wrong last month.
After the spill, about 30 pounds of the nutrient phosphorus was detected by monitors in Six Mile Creek from Nov. 26 through Nov. 28. That’s more than the 12 pounds expected for a normal three-day period but far less than during heavy rain or snowmelts, said Josh Wescott, chief of staff to county executive Joe Parisi.
Wescott estimated that the digester has prevented 5,100 pounds of phosphorus from entering the lakes as it reduced the nutrient level in 80 million gallons of manure since it started operating.
Still, county officials want the facility to ensure systems are in place to control any future spills, he said.