DL wastewater woes
A lot of changes will be happening to the wastewater treatment plant in Detroit Lakes over the next nine years.
While that may sound like a long time, it won’t be for the changes that are to come.
When the city tried to renew its wastewater permit in early 2012, the Minnesota Pollution Control Agency tightened some restrictions, making the facility out of compliance.
A total maximum daily load study had been done to the impaired waters of Lake St. Clair, where treated wastewater is distributed in the wintertime, and the intake to the lake was drastically reduced. That means it may not be an option for Detroit Lakes’ treated wastewater anymore.
The wastewater treatment facility, located on Willow Street, has been added onto multiple times over the years, beginning in 1929 and again in 1942, 1975 and 1995.
Facilities are built with a 40-year life expectancy on average.
“We certainly got our life expectancy out of it,” said Utilities Supervisor Vernell Roberts.
After being run through multiple purifiers and holding ponds, treated wastewater from the facility is distributed in two different ways: During the summer months, the treated water is applied to the land as fertilizer. There are shallow ponds out by the city-county airport where the water is absorbed and used for spray irrigation.
During the winter, that wastewater makes its way to Lake St. Clair.
Most lakes can naturally absorb nutrients, but Lake St. Clair is very limited in that ability.
The phosphorus limits had been set at 1 milligram per liter, or 6,142 pounds, but that has now been reduced to mass annual loading of 196 kilograms a year, or 432 pounds.
That change means the Detroit Lakes treatment plant has to reduce phosphorus in its discharge stream by 93 percent.
“That is a big reduction,” Roberts said.
The spray irrigation isn’t a problem, but the discharge into Lake St. Clair is a big problem, in part because it contains ammonia or some similar substance.
“I’m 99.9 percent sure it’s ammonia,” Roberts said, but the other .1 percent has to be verified.
“If you’re looking at year-round discharge to St. Clair, it’s almost impossible,” said Wastewater Supervisor Scott Gilbertson.
He said the treatment of wastewater is still excellent, but the facility is also reaching its limits with the various ages of the facilities, the new restrictions and the continued growth of the city.
“We have some challenges,” he said.
So the city is going to be doing some major overhauling of the system — although the details are still in question.
“It’s a huge investment for the city,” Roberts said of doing work on the wastewater plant, whether it’s upgrades, adding on, or building a new facility.
What the upgrades or changes will be are up in the air at this point. On Tuesday, the Detroit Lakes City Council approved entering into an agreement with Short Elliot Hendrickson, Inc., a Twin Cities engineering firm, to determine what needs to be done to the Detroit Lakes facility to comply with the MPCA permits.
The firm will study and determine capacity, technology, water usage, lift stations, future service areas and more. The study will take about two years.
“I think they’ll do a good job,” Roberts said.
To put the study into action, though, will take several more years, making this about a nine-year process.
“It’s so important to do this right,” Roberts said. “We need to make it adequate for 40-50 years. We can’t have a misstep. A misstep could cost millions of dollars.”
To help pay for the project, the city is raising wastewater rates gradually over the next few years, a few percentage points at a time. Roberts said he recommended doing that because he’s seen cities toe the line for several years and then suddenly have a 30-40 percent hike at once.
“That’s so hard to absorb,” he said.
There will be other means to pay for the project including bonds — some debt service bonds will be paid off in 2016 so more bonds could be sold for the project — and grants.
“If we get 15-20 percent in grant money, we’ll be dancing in the streets,” Roberts said.
He said he plans to start a community committee to work on what is needed out of the plant, too.
“I want to maintain the quality of life in Detroit Lakes.”
The area is heavily dependent on the lake quality, he said, and that needs to stay on track for the sake of the city.
“We need to maintain the high quality of lakes and high quality of tourism,” he said.
Follow Pippi Mayfield on Twitter at @PippiMayfield.