Ravine, stream and prairie projects underway: Watershed district starts work on several projects
The South Washington Watershed District staff has their work cut out for them.
The watershed district has several large projects on the table, including stabilizing Cottage Grove Ravine Regional Park as part of phases three and four of their central draw overflow project; erosion control, prairie restoration, stream restoration at Afton Alps and what are known as "living streets" and "living fences."
Funding for watershed projects come in bulk from watershed district taxes, through stormwater utility fees.
Central Draw Overflow
The origin of the central draw storage facility and overflow project dates back to the late-1980s, when the effects of flooding raised concerns in Cottage Grove and Woodbury.
The central draw overflow storage facility is located near Bailey Lake and can handle runoff from up to 6.3 inches in 24 hours.
The central draw overflow is being put in place to handle any rain events that exceed the storage facility's capabilities.
As of now, phases one and two of the five-stage overflow buildout process are complete, and the the watershed district is hoping the entire overflow will be complete by 2020. The first two phases added a pipe connection under Keats Avenue and a stabilization between Ravine Lake and the Mississippi River, where the stormwater discharges.
The watershed district will undertake phases three and four this summer, in Cottage Grove Ravine Regional Park. The work will concentrate on outlet structure and stabilization, Moore said.
The bulk of the work will be constructing a channel for the main ravine — running along the center of the park and to the north end of the river — to contain water flow in the park. There will also be a new outlet for the lake, and runoff in the park can travel along a central path to the Mississippi River, south of the park, Moore said.
He said the outlet will also help to "alleviate the park road entrance road being flooded."
"The existing park entrance road will be removed and new outlet constructed, will allow for better lake levels," he said.
Vegetation management will also be a part of the park restoration, and trees will be cut in March.
As the county constructs new paved roads and trails in the park, the watershed district will work with them to realign the trails and channel crossings.
Afton Alps stream restoration
To improve trout habitat and vegetation, the watershed district is also working on a project to restore Trout Brook on the northern edge of Afton Alps in Denmark Township.
Likely to be constructed next year, the bulk of the work includes directing the stream to the other side of Afton Alps' north parking lot.
"We will take the stream up against the bottom of the ski slope," Moore said. "It creates more of a cold water stream."
John Loomis, water resources program manager for the Trout Brook restoration, said the straightened stream along the alps is "essentially a ditch section" now. After they build a channel and divert the water south of the parking lot, he said the meander loop will be complete with pools and ripples. The new alignment should support the restoration of the trout population through the area, as well as native vegetation.
"The DNR does a fish survey, and every time they've found at least one or two (trout)," Loomis said. "They're likely migrating from the Wisconsin side during big floods ... the stream will likely be populated by fish migrating, and then hopefully they'll stay there."
The restoration is much more focused on habitat and wildlife than the other current watershed district projects and perhaps will help restore opportunities for trout fishing along the brook.
The straightening of the stream over time has augmented flooding issues, so the restoration process will include a 100-year floodplain.
Trout Brook currently runs along Afton Alps, through Afton State Park and into the St. Croix River. The restoration will not alter that path, only add a meander.
Loomis said Afton Alps has been cooperative and "fully supportive" through the process.
Loomis said funding is all in place for the anticipated restoration in summer 2018.
Water and prairie
Watershed district staff continue to work on the nearly 100-acre prairie restoration next to Woodbury Drive south of Dale Road. Andy Schilling, watershed restoration specialist, said 60 acres have already been restored since the conversion from farmland started in 2010. There are at least 40 more acres that could be restored.
Schilling said the restoration has dual function — as prairie land that can also be used as emergency overflow area for Woodbury stormwater.
The land is being looked into for research on several restoration and conservation topics, including the benefits and effects of haying in reducing nitrogen from the land's time as farm field; pollination research through the Xerxes Society; and grazing by cattle.
At some point, they could also partner with the county to extend trails through the prairie to provide more public access and to act as connecting land for a county-long trail system spanning from Cottage Grove Ravine Regional Park all the way to Lake Elmo.
"It's at a really interesting location since it spans the cities of Cottage Grove and Woodbury," Schilling said. "It creates an interesting nexus, and we feel it can fill a good niche."
Moore said they are also looking into working on a program with the Dodge Nature Center "which is something we're pretty excited about."
The nature center could provide the grazers, as well as "trying to build an educational narrative" between them and the watershed district, Schilling said.
Schilling is also working on urban vegetation projects called living streets and living fences.
There are no streets planned to get the living treatment this summer, but they are working on developing the pilot for it.
"It's looking at streets more holistically," Schilling said. "It's multi-modal and on-site stormwater management ... revisioning streets to potentially capture rather than capturing it by pipe and sending it downstream." By using additional right-of-way and widening boulevards, sidewalks, trees and vegetation can be added to city streets. The idea is that the vegetation systems will help "clean it or infiltrate it into the ground so it stays closer to where it lands," Schilling said, as well as reducing the amount of infrastructure in terms of pipes and manholes for water systems.
Living fences follow a similar structure by placing trees, landscaping and grasses as a stormwater filter in residential backyards.
"There are multiple benefits, and also functions as buffer or barrier that's much more aesthetically appealing (than a fence)," Schilling said.
The watershed district is working with a developer on the Twenty-One Oaks neighborhood to implement living fences. "We are looking to see if this goes well, tweak it and roll out to other development," Schilling said.
Erosion control inspections have also become a mainstay operation at the watershed district, doing them for free for most of the cities in the district.
"Inspect construction sites and make sure all the erosion control is in place ... and then the contractors will take action as needed," Moore said.
Moore said they inspect active residential and commercial sites twice during the construction season, checking for sediment runoff, mud on the road and silt fence functionality.
"We'll get a call ... and we'll go down and take a look at it," he said.