Lake Auburn consultant to evaluate where phosphorus increase is coming from

AUBURN — The Lake Auburn Watershed Protection Commission has hired a consultant to identify sources of increased phosphorus in Lake Auburn.

The nutrients, often entering the lake from stormwater runoff — and combined with shorter winters — have increased the likelihood of algae blooms in recent years. When discussing the proposal recently with the commission board, Auburn Water District Superintendent Mike Broadbent said the past year has been a “rough water quality year,” with very warm temperatures followed by extreme rain events.

Because of the amount of phosphorus entering the lake prior to “ice over” this past winter, officials said they’re concerned for possible taste and odor issues caused by algae — something that happened in 2018.

“I’m concerned with where we’re at, and want to be prepared in the event we have to treat the lake,” Broadbent said.

The Water District last treated the lake with aluminum sulfate in 2019. The “alum” is used to bind with phosphorus in the water column, sinking it to the bottom of the lake. Kevin Gagne, superintendent of Lewiston Sewer and Water, said the previous treatment wasn’t a high dose, with officials hoping to get three to five years out of it.

He told the board he’s concerned “we’re near the end of our effective alum treatment from last time.”

The board approved hiring Ken Wagner of Water Resource Services to conduct the $47,000 analysis, and officials said they will formulate a treatment plan based on its recommendations. That could include another alum treatment as soon as May or June.

Water officials believe the phosphorus is mostly coming from “external” sources, meaning nutrients entering the lake from tributaries like Townsend Brook. A large storm around Christmas caused a culvert failure on Lake Shore Drive, he said, and has led to a higher turbidity level.

Gagne said the district needs to gain a better understanding of the phosphorus inputs to the lake, and which ones to focus on. He said the analysis will look at tributary areas, drainage, current conditions, land use and new water quality data.

Depending on what the consultant finds, the district could do alum treatments in specific areas, which Gagne referred to as “dosing stations.”

Camille Parish, a commission board member, said based on recent data, a major source of phosphorus seems to be coming from Townsend Brook, which runs parallel to Route 4.

“We need to identify sources and address them,” she said, adding that simply treating the end of a tributary isn’t finding the source of the problem.

“We could be doing that for 100 years,” she said.

During the meeting, one board commissioner said another alum treatment would essentially be “a band-aid that buys us time to address what’s further up.”

The concerns over water quality come at a time when the cities are at odds over proposed changes to watershed rules, including updated septic design standards.

As Auburn has considered the changes, an analysis of the watershed by FB Environmental has said that even with the proposed changes in Auburn, changes must also be made in upper watershed towns such as Turner, Minot and Buckfield.