Lake Nokomis restoration begins

by Jennifer Harris

After years of planning and discussion, Lake Nokomis is finally getting its facelift. The Minneapolis Park Board and Public Works Department have been working over the winter to get ready before the lake officially opens for spring.
Among the improvements are: installing two underground grit chambers to treat storm water runoff; building storm water detention ponds, where water entering the lake will be naturally filtered before it gets pushed into the lake; installing a submerged, inflatable dam to keep polluted water from Minnehaha Creek from flowing into the lake during heavy rain; and harvesting carp, which are not native to the lake and which feed by cruising the bottom, kicking up phosphorus-laden fertilizer runoff and other pollutants.
Once all of these are finished and after some preliminary monitoring, the lake will be treated with alum, which binds safely with phosphorus and causes it to sink permanently to the bottom of the lake.
Phosphorus pollution, usually caused by lawn fertilizing, results in problems for lakes because it encourages algae growth in the water. This makes the water murky and smelly, and reduces the amount of oxygen required for many species of fish.
To further reduce phosphorus pollution in Lake Nokomis and in the rest of the Minnehaha Watershed, there are neighborhood education programs to encourage people to use other kinds of fertilizer in their yards. This includes all communities between Lake Minnetonka and the Mississippi River.
Regular street sweeping will reduce the amount of leaves and other debris washed into the lakes. Lake users will probably not see the full results this summer. The alum treatment, which will show instantaneous results, according to Jeff Lee, manager of environmental operations at the Minneapolis Park and Recreation Board, will not be done until fall at the earliest. The other treatments, most notably the ponds now being built, will gradually cause the lake to be cleaner as filtered water replaces the polluted water currently there.
Phase one of the construction schedule, including the excavation of the ponds, and a related rerouting of part of the pathway around the lake, is on schedule and will be done by spring. Phase two, which will include seeding and planting at the wetland ponds, as well as some tree relocation and removal, will begin soon. Shoreline restoration along the north and east shores of the lake are planned for this summer.
The three ponds are each going to be unique. Local residents were involved in the concept design of the ponds, as well as naming them. Nokomis Knoll Pond, at the northwest shore of the lagoon west of Cedar Avenue, will have the most formal landscaping, with native and prairie plants that grow to a maximum height of two feet. Amelia Pond, at the southwest edge of the lagoon, will be the wildest, with informal prairie plantings that grow as high as 6 feet. Gateway Pond, at the southwest corner of the lake, will have native prairie plants that grow under 2 feet high.
The plantings will start in the ponds with floating plants, then emergent plants in the shallowest parts, then wet prairie and finally wet mesic plants. They have been chosen to be in harmony with native birds and animals. One nice feature is that since Canada Geese don’t like lakeshores planted with prairie-style grasses etc., they should not be the problem they are at other area lakes. Prairie plants provide four seasons of interest, too, instead of grass which is brown and ugly in spring and fall.