By Andrew Tellijohn
When 2013 water quality tests on Northwood Lake revealed phosphorous levels four times higher than state standards allow, New Hope city officials teamed up with the Bassett Creek Watershed Management Commission to fix the situation.
Their response was a $1.9 million solution that included an underground water reuse system and stormwater treatment structure along the northeast corner of Northwood Park, and a water treatment pond along Jordan Avenue.
Together, the projects are expected to remove 22 pounds of pollutants from the water each year while the underground tank will provide irrigation for nearby ballfields, saving $10,000 worth of treated city water. New Hope received the 2017 Sustainable City Award for this initiative from the League of Minnesota Cities and Minnesota GreenStep Cities.
City officials said the timing of the project worked out well. “There were all these grant opportunities, so the funding was there,” says Jeff Alger, community development coordinator/management analyst. “New Hope is always looking to do its part to be sustainable and solve problems.”
The city completed the project in 2016, but it did not come together without some challenges. The treatment pond by Jordan Avenue was non-controversial, but the underwater tank was significantly more expensive than a competing proposal that would have constructed a water treatment pond at the expense of a significant portion of the city’s popular Northwood Park.
Northwood Lake, bordered by New Hope and Plymouth, has had water quality challenges for years. It was dredged decades ago out of a wetland by a developer who thought it would be nice to build homes around a small lake. It receives a lot of urban runoff from multiple directions, and that doesn’t help its water quality.
It has been high in nutrients for some time, having gone through some less invasive treatment strategies in the past, says Laura Jester, administrator of the Bassett Creek Watershed Management Commission.
“The City of New Hope and the Bassett Creek Watershed Management Commission have been working to improve the water quality there for a long time,” she adds.
The city and the commission held two meetings during the summer of 2014 to get feedback from the community. Initial concepts were discussed at the first meeting. Potential improvements with updated concepts based on feedback were discussed at the second. The city also worked with the Friends of Northwood Lake Association to determine the best course of action.
The less expensive pretreatment pond had been in some old plans for potentially treating the problem, says Chris Long, city engineer. But residents and members of the association took umbrage at the idea of losing a park while adding another potential breeding ground for green algae.
“It was quite the process,” Long says. “This was controversial. They wanted to save that valuable park space. It started with the residents and staff saying, ‘This park space is important; we’d rather not have another pretreatment pond in a park space.’”
The Bassett Creek Watershed Management Commission often fully funds projects like this out of a capital projects budget. But this was not their typical project.
“Usually, when we have a feasibility study, we’re looking at options or alternatives that are relatively similar in dollar figures and the amount of pollution that it would take care of,” says Jester. “The alternatives that were developed for this situation were vastly different.”
Community stakeholders lobbied loudly in favor of maintaining the valuable parkland located in the heart of the city. The commission reviewed pros and cons from various angles and ultimately scored the underground tank project higher.
“That made commissioners feel a lot more comfortable with choosing this more extensive project,” Jester says. “It was not confrontational or adversarial. It was really trying to work through the pros and cons and figure out if it was worth the huge price tag.”
State funding sources helped. Ultimately, the commission received grants totaling $700,000 from the Minnesota Pollution Control Agency and the Minnesota Board of Water and Soil Resources. The Bassett Creek commission kicked in $750,000 and the City of New Hope spent about $450,000. The project was completed in 2016.
With the new system, workers redirected a 100-acre-plus drainage area away from Northwood Lake and into a new pipe that directs it to the 160,000-gallon underground tank, Long says. Before it gets to the tank, it goes through pretreatment structures that collect leaves and remove sediment.
Once the tank fills up, water can overflow into rain gardens for more treatment before it goes into the lake. New Hope Public Works staff clean out the tanks twice a year or so, Long says.
The stormwater system ships water from the tank under the street over to irrigate the ballfields, Alger adds. Previously, treated city water was being used for those purposes, a projected savings of $10,000 annually.
“That’s a significant number. We can definitely say we are saving money as a result of these improvements,” Alger says.
While city water remains the backup plan if irrigating the fields drains the underground tank, Long says that has not happened since the project was completed.
“The tank holds enough water where we could have a dry period for two weeks and we could irrigate the city ballfields on the east side of Boone Avenue for two weeks or so,” he says. “So far we haven’t had to use the city water.”
The project, Alger says, was in keeping with the city’s efforts to be sustainable and environmentally friendly. New Hope joined Minnesota GreenStep Cities in 2015. The city has reached Step 3, having completed 18 of 29 best practices and 76 of 175 best practice actions.
The city factors in the program’s recommendations when considering policy, development, and purchasing, and the stormwater project aligned with that commitment.
“We’re proud of that,” Alger says. “We’ve made a huge dent in terms of implementing these best practice actions.”
While all appears to be on track so far, it’s going to be a while before the city and watershed commission have concrete evidence of the underground tank’s impact on Northwood Lake. The work in New Hope only solved a portion of the lake’s water quality issues; additional stormwater treatment features are planned for the other side of the lake as part of the redevelopment of the old Four Seasons Mall in Plymouth, Jester says.
The shallow lake captures run-off from almost 1,300 acres of urban area, which is a lot for a small body of water, Jester says, adding that it has led to considerable buildup of phosphorous over time.
“It will take a lot of time to see the results on the water quality,” she says. “This project is a great start, but there is so much phosphorous built up in the lake that even if we turn off all the phosphorus entering the lake now, it may take years to see significant changes in water quality due to internal phosphorus sources.”
Aside from its use with the lake, the underground tank is providing some educational value, Jester adds. It’s an unusual system, one that has gotten the attention from student groups as well as environmentalists wondering if this might be an option in other places.
“Water reuse tanks are getting more and more popular because they solve two problems,” Jester says. “They capture the stormwater, and they reduce the need for pumping groundwater for irrigating ballfields. But there are more expenses and there is more maintenance. It was a new kind of project for us, but it seems to be working great.”
Andrew Tellijohn is a freelance writer based in Richfield, Minnesota.
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