Lewiston Mayor Carl Sheline speaks about water quality in Lake Auburn during a press conference Thursday afternoon in council chambers at Lewiston City Hall. Russ Dillingham/Sun Journal

LEWISTON — City leadership sent letters to Auburn water officials Thursday requesting a moratorium on any new development in the Lake Auburn watershed, a move that highlights a simmering rift between the cities over the future of its shared drinking water source.

During a press conference Thursday, Lewiston Mayor Carl Sheline said he’s concerned that recent efforts in Auburn to rezone land and update septic design standards will lead to further harm to a fragile water source.

The two cities have long discussed the threat of losing a filtration waiver, which allows the district to treat water without building a costly filtration plant.

Sheline said Lewiston is particularly concerned with Auburn’s recent rezoning of 148 acres lying between the Auburn Mall area and the lake, which features a large gravel pit. With more development comes more storm water runoff, he said, which typically brings more algae-producing phosphorus and other nutrients into the lake.

A view of the giant sandpit March 23 between Gracelawn Road and Lake Auburn. A recent change in the watershed boundary has paved the way for development at the site. Visit sunjournal.com to watch a closer view of the area. Russ Dillingham/Sun Journal

“These 148 acres not only lie within the watershed but are within the critical level 1 zone that is near the water intake for both cities,” he said. “This parcel of land sits uphill from the lake. We are deeply concerned about the increased runoff should development and site work occur.”

Auburn officials, with data from a recent study, have argued that the land is not part of the watershed, and that developing the site would be beneficial to storm water mitigation.

Auburn Mayor Jason Levesque was quick to respond to the Lewiston news conference Thursday, stating, “I wish Lewiston would stop being so jealous of Auburn and our success and actually focus on their issues. I have confidence that the Lewiston City Council will do that because the mayor isn’t.”

The initial press advisory from Lewiston said Sheline would be joined by the City Council, but no councilors were present during the press conference. When asked, Sheline said the council agreed unanimously earlier this week to send the letters to Auburn officials.

In a statement after the press conference, Levesque said Auburn “will rely on science, facts, and careful deliberation to support our decision-making,” and “will make those decisions within the walls of our council chambers, with input from the public and our elected officials. Not in front of a microphone.”

He also added, “We will remain focused on addressing Auburn’s challenges, such as attainable housing and aligning with regional and statewide priorities. We will do this while remaining deeply committed to protecting Auburn’s extraordinary natural resources, our quality of life, and our greatest assets. We will continue to support proactive policy and avoid repeating old and tired policies of the past. And we will not have our city’s future dictated to us by the mayor of another municipality.”

An aerial view Thursday afternoon of the Lake Auburn Pump Station off Turner Street in Auburn. Russ Dillingham/Sun Journal

In a letter to the Auburn Water District, Lewiston City Administrator Heather Hunter requested the district “exercise its authority” to “institute a moratorium to prohibit all development, including additional housing and other associated developments in the watershed until a full and comprehensive study of the effects of development in the watershed is completed and the Maine Department of Health and Human Services has determined, after a review of the study, that development will not have an adverse effect on the conditions for maintaining a waiver from the filtration requirements.”

During his remarks Thursday, Sheline said, “If we were to lose our filtration waiver, it would necessitate building a filtration plant costing tens of millions of dollars and requiring millions more per year to operate. The best and cheapest option is to maintain water quality in Lake Auburn.”

Hunter’s letter said cost estimates to “meet filtration requirements” are more than $20 million initially, with between $1.5 million and $2 million in annual operating costs.

The Auburn Water District trustees recently tabled a discussion over pursuing funds for a filtration plant design.

Hunter said the recently rezoned area in Auburn was part of the lake’s “intake restricted area,” which the Auburn Water District by-laws refer to as “the most critical area for protection since microbiological, chemical particulate, and other contaminants are most likely to reach the intake from this location.”

She said now, a portion of that area “does not have land use restrictions to ensure that particulate and other contaminants do not reach the lake water, which would imperil the drinking water supply for AWD customers and Lewiston residents.”

The letters from Hunter request a response from Auburn by mid-April. In response to questions from members of the media Thursday, Sheline said the requests were sent in an effort to avoid legal proceedings.

When asked, Sheline said he’s also concerned with Auburn’s efforts to update septic design standards in the watershed, a move that was recently supported by the AWD trustees and will be heading to a City Council vote in April.

Auburn staff has said the new septic design standard would make it easier for new, better-performing systems to be installed in the watershed, but would also allow a number of new homes to be built.

A recent study in Auburn found that the septic standard used in the Lake Auburn Watershed Overlay District limits development on a significant part of the watershed by “effectively prohibiting the use of innovative and alternative septic system and leach field designs.”

The Lake Auburn study, completed by FB Environmental, the Horsley Witten Group and the University of Maine, was commissioned by the city to analyze the rules governing the watershed.

A summary of the report said additional development in the watershed would provide “minimal net economic benefit across all affected stakeholders,” but also recommended a new septic design that could lead to more homes there.

A “build-out analysis” in the study determined that more than 100 additional new homes could be built in the watershed if the septic system requirement was revised.

In his remarks, Sheline referenced correspondence in February between Lewiston water officials and the Maine Center for Disease Control & Prevention’s Drinking Water Program, which came in response to questions over the proposed septic design update.

In the letter, Susan Breau, a state hydrogeologist, said there are only 50 drinking water sources nationwide that still maintain a waiver, and added, “the (Drinking Water Program) will always advocate for the most protective watershed practices attainable, particularly when a filtration waiver is in place.”

“In this case, modifying the current septic system requirements in the (watershed) could result in biological contamination to the lake if new septic systems are not installed and maintained properly,” she said. “(Lewiston Water Division) should be aware that these circumstances could threaten LWD’s filtration waiver for Lake Auburn if future sampling determines that standards have been exceeded.”