What’s Going On at Grass Lake?
You may be seeing a lot activity around the Grass Lake and Vadnais-Snail Lake Regional Park area and wondering what is going on. The Ramsey-Washington Metro Watershed District (District) has contracted with Northern Dewatering to move forward with a project to help alleviate the flooding risk by lowering the higher than normal water levels in the adjacent wetlands. We will be pumping the water from the large Wetland A (see map below) back into Grass Lake where it came from. The District’s modeling suggests that this will help reduce groundwater levels around the neighborhood of concern. The Crestview Addition neighborhood has been coping with high groundwater levels, likely due to the long term high levels in those surrounding wetlands.
Northern Dewatering will be connecting over 2,000 feet of 12-inch diameter pipe and routing the pipe from the large Wetland A, through the tunnel in Gramsie Road and into Grass Lake. As of today, April 6, you will see the contractor in the area near Gramsie Road. They are first pumping the water out of that area to allow use of the pedestrian tunnel for the longer discharge pipe. The tunnel will not be open to pedestrians during the pumping effort. The berm along the north side of Grass Lake will also be improved to provide the storage needed to accept the water pumped from the Wetland A. After they pump the area around Gramsie Road and the 12” pipe is built and in place, a large (but quiet) pump will be placed in Wetland A and the pumping will begin.
To keep an eye on how the surface and groundwater levels are responding to the pumping, the District has installed two groundwater monitoring pipes in the area as well as six lake/wetland level gauges in the necessary water bodies. The District will be monitoring all the levels to assess the impact surface water pumping has on the groundwater levels as well as keeping an eye on the need to delay pumping due to weather conditions. It will ensure that there is not an increase flooding risk in and around Grass Lake.
|Water being pumped into Grass Lake|
From the Grass Lake area, the water drains to West Vadnais Lake and eventually south of I-694 through a pipe and into the District’s Gervais Creek system. From there you can follow the path of the water all the way from Gervais Lake to Lake Phalen and eventually the Mississippi River! Prior to today, a small culvert on the north side of Grass Lake was blocked to stop the flow of water from there to the north and into Wetland A. Also, the District’s maintenance contractor cleaned out a channel south of West Vadnais Lake in order to open up that flow path for better drainage efficiency. District staff will continue to monitor the flow path and all potential restrictions to that flow.
The District will be closely monitoring the system throughout the duration of this project. The modeling efforts the District has done to this point show that, in and of itself, the pumping of water from Wetland A back into Grass Lake does not negatively impact any other structures or infrastructure. That being said, we will be watching the forecasts and rain events closely. Rain events, depending on the intensity and timing, could yield further impacts to the park and roadways. Those would occur whether or not we pumped the water back into Grass Lake from the wetland, but will still need to be monitored closely. There may be times where we will need to shut the pumps off in order to not be pumping water that will find its way back into the wetland during a rain event. If all goes as planned, the pumping is expected to last 4-6 weeks.
The District is also proceeding with a large-scale modeling effort to search for potential long term solutions to the flood risk in this area, as well as looking more into the Snail Lake high water levels. More to come on that in the near future.
Please click here to see this update along with background information on this area.
Please email Tina Carstens, District Administrator, with any questions or call 651-792-7950.