Mount Airy officials are spending up to $23,500 for a study on nutrients released from the municipal wastewater treatment plant, in the hopes of avoiding a larger expenditure later.

“This is a complicated and potentially expensive issue for the city of Mount Airy,” according to Public Services Director Jeff Boyles, who oversees municipal water and sewer operations.

It relates to problems detected at High Rock Lake, which is considered impaired due to high chlorophyll levels that promote excess algae growth and can lead to fish, other animals and plants being killed.

This is requiring the N.C. Department of Environment and Natural Resources to establish limits on nitrogen and phosphorus, nutrients considered to be the most important factors for algae growth. Those limits will affect entities discharging treated wastewater into the Yadkin River basin upstream of High Rock Lake, which includes Mount Airy.

The resulting limits will exceed the city’s present treatment capability and affect its permit for discharges toward the end of this decade. That will require an extra expenditure for the more-extensive treatment measures involved.

Boyles added, “The cost to the city of Mount Airy for this enhanced treatment will be significant, and can vary greatly depending on the final limit for each of these nutrients.”

Scott Graham, a member of the city board of commissioners, said Thursday when the matter was discussed during a meeting of the board that he was concerned about when the municipality will be faced with the additional cost.

“There’s no way of knowing when exactly it will have to be spent,” said Steve Tedder, a consultant from King who gave a presentation on the nutrient requirements at Thursday’s meeting.

The new limits are still several years away, although the preparation should begin now, Tedder added.

He said regulatory plans have been developed for other watersheds in the state and High Rock Lake is the next in line. “There are several things related to nutrients that are on the board right now,” the consultant said.

After hearing Tedder’s presentation, the commissioners voted 5-0 to fund an initial review and planning project study for nutrient control at the Mount Airy Wastewater Treatment Plant.

This will mean paying CDM Smith Inc. — a consulting, engineering, construction and operations firm with offices in Raleigh and Charlotte — on a cost-reimbursement basis for various aspects of the study. The total fee will not exceed $23,500, according to city documents.

The study will include developing potential approaches and estimated costs for controlling the nitrogen and phosphorus output under various permitting scenarios. It also will serve as a foundation for a more in-depth optimization study to be required as early as 2014.

“Having valid numbers makes a big difference,” Tedder said.

Commissioner Jon Cawley said he hopes the eventual expense to the city might be lessened by the relatively long distance between Mount Airy and High Rock Lake, which has a water surface covering 15,180 acres. The lake is located in Davidson and Rowan counties about 60 miles away.

Tedder said there is a chance the nutrient levels attributable to Mount Airy could be diminished as a result.

Reach Tom Joyce at 719-1924 or tjoyce@heartlandpublications.com.