George C. Rosati, Mankato’s director of public works, noted the proposed ethanol plant is within the Blue Earth River watershed. Mankato relies heavily on the Blue Earth River for the majority of its drinking water supply.

“Nitrogen-nitrates levels in the Blue Earth River fluctuate greatly throughout the year and are of great concern to the City,” he wrote. He questioned whether the expected increase in corn production would increase the levels of nitrogen-nitrates in the Blue Earth River.

A similar comment by Bruce M. Olsen, supervisor of Mankato’s Source Water Protection Unit, focused on the potential impacts that increased corn production may have on water quality in the Blue Earth River.

“The Blue Earth is a source of drinking water for the city of Mankato and the city cannot treat for nitrate contamination,” Olsen stated in his letter.

An official from the Minnesota Department of Health also commented on the potential impacts on drinking water as the result of increased corn production needed to support the ethanol plant.

The Department of Health letter noted that “nitrate-nitrogen levels that exceed federal and state drinking water standards in Mankato’s source water is an ongoing drinking water management issue with Mankato water utilities staff.”

Bowles said that US BioEnergy does not believe their discharge water will increase the level of nitrate contamination in local drinking water, including Mankato’s, because it will not be necessary to produce more corn in the area.

“Based on USDA data, the current acreage of corn is more than adequate to supply the demand,” Bowles said.

Water supply

MCEA, the environmental group, wrote a lengthy letter regarding the proposed ethanol plant challenging the MPCA’s permitting process in general as well as issues specific to the Janesville site.

“Every single ethanol plant in Minnesota has significantly expanded from its initial size and MPCA has yet to order an EIS on any of them,” the environmental group stated.

“US BioEnergy represents the single largest proposed ethanol plant in Minnesota so far and is the largest by a significant degree. It is proposed in a troubled watershed and the figures given for water usage suggest its intent to be much larger than the 120 million gallons proposed for the initial phase,” the group stated.

MCEA noted the US BioEnergy proposal to manufacture 120 million gallons of ethanol per year (from 43 million bushel of corn) is just 5 million gallons of ethanol under the threshold for a mandatory EIS. The group noted that in its application US BioEnergy stated it would need 788 million gallons of water per year, which is almost 7 gallons of water for every gallon of ethanol made. Since the rule of thumb for water use by ethanol plants is about 4 gallons of water for every gallon of ethanol, based on other ethanol plants, the environmental group questioned the figures used by US BioEnergy.

“Such an enormous water need suggests to MCEA that US BioEnergy, like other ethanol plants, has every intention of expanding in the near future,” the letter signed by the group’s legal director stated.

“Our water consumption is based on the design of our plant and is what we need to operate,” Bowles said. Bowles said this is the maximum rate, worse case scenario, on the hottest summer day when all the cooling equipment is in operation. He estimates actual usage will be about 80 percent.