Untreated sewage in Lake Superior should become a thing of the past in the Duluth area, but not for another seven years.
The city and Western Lake Superior Sanitary District (WLSSD) have committed to end sewage overflows by the end of 2016, and to pay $400,000 in fines to state and federal pollution authorities for past violations.
The overflows typically are caused by backups during heavy rain.
The agreement, filed in U.S. District Court in Minneapolis on Tuesday, ends four years of negotiations between city and district officials on one side, and the Environmental Protection Agency and the Minnesota Pollution Control Agency on the other.
EPA officials estimate at least 47 million gallons of raw sewage spilled into the St. Louis River and Lake Superior during more than 250 overflows between 1999 and 2004. The federal Clean Water Act prohibits such pollution.
Sewer system is old, leaky
John Cruden, acting assistant attorney general for the Justice Department's Environment and Natural Resources Division, said that the settlement provides a plan to "protect water quality in the Duluth area without the need for expensive and time-consuming litigation."
He estimated the required sewer improvements will cost $130 million.
Marianne Bohren, executive director of WLSSD, said the district and Duluth have worked for several years on the problem and have already spent "tens of millions of dollars" on an overflow storage basin and other improvements.
"We would have done this anyway, but this [final agreement] formalizes what else needs to be done and when it needs to be done by," she said.
The main problem is that Duluth's sanitary sewer system is old and leaky, she said.
System gets overwhelmed
On a typical day the sewage treatment plant receives 40 million gallons, Bohren said, but on a rainy day it can peak at 130 million gallons, overwhelming the system and causing backups of untreated sewage that run into the lake.
The excess water comes from various places: leaky main-line sewage collection pipes that allow rainwater to infiltrate, smaller lateral pipes between homes and street lines that also have cracks, and foundation drains around thousands of older homes that lead directly to the sewage system.
Eric Shaffer, Duluth's chief engineer for utilities, said the agreement with pollution authorities requires the city to spend an extra $52 million for new pump stations and underground storage tanks that can hold excess sewage until it can be treated.
Another part of the solution requires about 1,400 leaking home and business sewer lines to be dug up and replaced during the next eight years, at an average cost of $7,000.
Another provision mandates that about 5,000 homes disconnect their foundation drains from the sewage system and install sump pumps, at an average cost of $1,800.
A large financial burden
Duluth has inspected sewage lines of about half of its 26,000 residential and commercial customers, said Shaffer, and is identifying which ones need to be fixed. "Overall we can get this done, time-wise," he said. "But it's a large financial burden for the city."
The city instituted a $5.57 monthly surcharge last year on customer sewer bills to pay for storage tanks, Shaffer said, and another $3.27 per month recently for a grant program to help homeowners afford improvements.
Duluth mayor Don Ness said it's appropriate to ask federal officials for help, since the city is facing a federal mandate.
Ness said that Duluth received more than $5 million in grants and loans from two federal programs so far, including stimulus dollars, and that it will seek additional funds.
"Certainly protecting Lake Superior is our city's most sacred responsibility," he said.
The city and WLSSD operate the system jointly, with the city handling 400 miles of smaller sewer lines, and WLSSD operating 75 miles of larger lines and the treatment plant.
Besides 90,000 people in Duluth, WLSSD serves about 40,000 residents in 17 neighboring communities. The agreement is subject to a 30-day public comment period and approval by the federal court.
Tom Meersman • 612-673-7388