Western Sugar Cooperative has paid a $20,000 fine for water quality violations stemming from a 15-million gallon holding pond breach that flooded south Billings in 2011.

State Department of Environmental Quality officials declared the fine paid Monday. The agency said Western was taking steps to better handle water from its Billings sugar refinery.

Farmer-owned Western refines sugar from beets, which are mostly water. For decades, the extracted water was discarded without incident into above ground holding ponds at the State Avenue refinery. But a portion of the holding pond wall collapsed Jan. 2, 2011, flooding neighboring properties and sending millions of gallons of beet water into a ditch feeding the Yellowstone River.

The wastewater was inert, but coated neighboring properties in a gray foul-smelling sludge. A months-long cleanup followed.

"It's very unfortunate this happened. We didn't anticipate it," said Kent Wimmer, Western spokesman. "In all sincerity, we're looking at all the options. We want to stay in compliance. We want to be good environmental stewards."