New Brighton opts for park pond project

Work on Hansen Pond will replace the current city-built dam with a new, taller structure. RCWD said water levels would have to rise more than 4 feet to crest the new dam. (Mike Munzenrider/Bulletin)
Work on Hansen Pond will replace the current city-built dam with a new, taller structure. RCWD said water levels would have to rise more than 4 feet to crest the new dam. (Mike Munzenrider/Bulletin)

$4.8 million plan goes for water quality and flood mitigation

Plans to drain and dredge the Hansen Park Pond in New Brighton are moving forward, the results of which will create the city's newest island, through improved area water quality and flood mitigation is the aim.

New Brighton approved an agreement with the Rice Creek Watershed District at the city's March 24 council meeting. The agreement will set up the final stages of RCWD's planning of the Hansen Pond project. Hansen Park is located just south of Interstate 694 and a few blocks east of Silver Lake Road.

The $4.8 million project's goal is improving the water quality downstream in Long Lake and reducing the probability of flooding if the pond level rises.

RCWD received a $3 million Minnesota Board of Water and Soil Resources grant in 2014, half of which will go toward the work on Hansen Pond. The rest of the funding will be raised through smaller grants and the watershed district's tax base, which covers four counties and 186 square miles.

Temporarily drained

Kyle Axtell, a water resource specialist at RCWD, explained at the New Brighton meeting that the pond will be dredged in order to remove polluted sediments, keeping them from ending up downstream.

In all, he said, the plan is to remove about 60,000 cubic yards of material from the pond. This excavation accounts for around half of the project's overall estimated cost, about $2.4 million.

Excavation work will begin in late 2016, Axtell said, and will last about a year. Throughout the winter of 2016-2017, the pond will be completely drained to aid the removal of sediment.

"We're going to de-water that pond," Axtell said.

A result of the pond renovation will be an island that splits the pond from south to north, as water flows around it. Axtell said the island will slow the water flow and block sediment from moving through the pond, preventing it from making it downstream to Pike Lake and Long Lake.

Phosphorus is the main pollutant of concern, because it can cause algae blooms, which are unsightly and can kill off fish. In addition to the dredging and island making, RCWD will install an iron-enhanced sand filter in the park, which is designed to attract and hold phosphorus.

Axtell said the filter is essentially a sandbox with small amounts of iron mixed in. Park-goers can safely walk on it and the only maintenance it requires is occasional raking, and sometimes the replacement of the iron.

"It's iron and sand; there's nothing harmful there," Axtell said, noting that a similar iron-enhanced sand filter is located near the Costco in Maplewood.

The water quality improvement aspect of the Hansen Pond project is linked to two other water quality initiatives RCWD currently has in the works.

One is returning Rice Creek to its natural, curvy, meandering path, in order to better capture sediment on the creek's turns. The other is invasive carp management in Long Lake; the carp are bottom feeders who turn up settled sediments on the bottom of the lake, potentially releasing pollutants such as phosphorus.
 

Flood mitigation

Hansen Pond was created in 1979 when New Brighton built the dam that is at the pond's north end.

What's referred to as the "super storm" during the summer of 2011, which dropped 7 inches of rain in four hours, flooded the pond and areas around, prompting the city to seek flood mitigation help from RCWD.

Axtell said dredging the pond will lower its water level while making it deeper overall.

"In effect, what this all will do is lower the normal water level in the pond by approximately 2.3 feet from the current level, while also adding, in total, 0.7 feet to the depth of the pond," he said.

That difference in depth, Axtell said, should give the pond the capacity to handle about 2 inches more rainfall during a 100-year flood, a significant number, he said, because of the size of the pond and its drainage area.

The Hansen Pond project will also replace the more than 30-year-old dam, creating a taller structure that also has a bypass pipe to control discharge.

New Brighton resident Ed Davies, who told the meeting that he lives on the east side of the park, applauded the flood mitigation efforts.

He said that houses in areas with known flood risks are difficult to sell and that homeowners are burdened by having to buy flood insurance. Davies said the flood mitigation might help in negating the Federal Emergency Management Agency requirement that he and other homeowners in the area buy the insurance, saving thousands of dollars.

"It's a big deal to us," he said, drawing out the word "big" for emphasis.

Bridge to somewhere

The agreement between New Brighton and RCWD, which was approved unanimously by the city council, lasts 25 years. Axtell said the watershed district, possibly within two decades, could decide to dredge the pond again.

The city is not responsible for any direct costs associated with the Hansen Pond project, though it's possible it could elect to improve trails in the park.

The pond will be transformed by the project, Axtell said, as its shape and size will be altered and the surrounding cattails will be removed, making it more accessible and attractive for activities like kayaking.

Council member Mary Burg said of the project, "It's pretty cool that we're doing it and we all agree that we were lucky to get this grant."

Axtell said the idea of a boardwalk to the yet-to-be-created island had been floated in RCWD plans, though he said it's neither essential to the project nor currently budgeted for.

"We like the idea at staff level," he said, "But we don't know if it will get past the board."

Council member Brian Strub mentioned how well-used the boardwalk to the island in Silver Lake Park is, and urged Axtell and RCWD to remain open-minded.

"If you're in the concept phase, let's continue to have concepts," Strub said.

RCWD will hold a public meeting on the Hansen Pond project this summer.

Mike Munzenrider can be reached at mmunzenrider@lillienews.com or 651-748-7824. Follow him on Twitter @mmunzenrider.

 

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