A pipe burst Wednesday at the Clear Horizons biodigester near Waunakee, spewing tens of thousands of gallons of manure onto the ground for the third time since November, state officials said.

The spill happened less than 24 hours after Clear Horizons officials met Tuesday to negotiate a settlement with the state Department of Natural Resources over the two previous spills and other violations.

Dane County Executive Joe Parisi, who has been urging the company to install more safety equipment, now want Clear Horizons to contract with an experienced outside company to manage the facility until improvements are made and the situation is “stabilized,” said Parisi’s chief of staff, Josh Wescott.

Clear Horizons now operates the facility with its own employees. One of them noticed Wednesday’s spill and stopped it ?before manure could spread outside of the facility property, said DNR spokesman Bob Manwell

The cause of the pipe failure isn’t known, said David Mosher, a DNR wastewater specialist.

Agency officials aren’t yet releasing information on agreements reached with the company on Tuesday, ?Manwell said.

The DNR in January cited Clear Horizons for the spills and for failing to remove enough phosphorus from manure before it is spread on farm fields.

The $12 million plant was built in 2010 with government subsidies. It is designed to generate electricity from methane gas and removes some of the phosphorus from manure. Runoff of farm phosphorus is the major cause of smelly weeds and algae in Madison’s chain of lakes.

This spill will be investigated separately from the 380,000-gallon spill in November and the 22,000-gallon spill in January, Mosher said. The previous spills occurred when a bend in a pipe near the pump house burst.

A different type of pipe in another place failed Wednesday, Mosher said.