Since water levels of Crystal Lake hit a record high May 31, surrounding areas in Robbinsdale have been struck with flooded roads, backyards, and basements.
“The boat launch at the south end of Crystal Lake is virtually underwater right now,” said Richard McCoy, the city’s engineer and public work director. He added that three ponds connected to the lake have turned into “one big pond.”
McCoy led a special work session and fielded questions from affected residents June 4 to communicate what is being done and what might be done in the future to counteract what he described as an “upward trend” in the lake’s elevation levels.
Exhibiting a graph of Crystal Lake elevations since 1990, McCoy said that he had foregone drawing a trend line, but there was no mistaking that the numbers continued to rise year after year.
“From the start to the end is an increase,” he said.
McCoy said that today’s storms are “peakier” and drop a higher volume of water than usual, and infrastructure that pumps out water from Crystal Lake hasn’t been able to keep up with the volume.
Solutions, long and short term
Crystal Lake’s 851.2-foot record elevation is nearly 4 feet higher than the ordinary high water level (847.5 feet). According to the Minnesota Department of Natural Resources, ordinary high water levels are usually “the point where vegetation changes from predominantly aquatic to predominantly terrestrial.”
The levels have put sections of Chowen Avenue and other roads underwater and caused flooding in low-lying areas that have damaged or rendered parts of properties inaccessible. Stagnant water can create a foul odor after extended periods of time, kill trees and create an ideal breeding environment for mosquitoes. McCoy said the Metro Mosquito Control District, which serves Hennepin County, has been notified of the circumstances and will monitor the situation.
Some areas not close to the lake have also been affected due to the saturation of groundwater surrounding the lakes, causing back-ups to piped storm water and filling areas that are lower elevations than the lake.
Because the lake has no outlet, water will continue to rise if rain continues and no manual removal process is in place. Currently, two pumps are pumping water out. The first pushes water to directly to Minneapolis’ storm water system at a maximum rate of 1,150 gallons per minute, which City Manager Marcia Glick likened to approximately one-half inch a day assuming no additional rainfall occurs. During rain events, the pump is stopped to prevent overloading the Minneapolis system.
The second pump was approved by the DNR last week, was quickly installed and is pushing water to the Ryan and Twin Lake system until a larger emergency pump arrives. The Ryan-Twin lakes system hasn’t brushed record elevations like Crystal Lake, and has a natural outlet that leads out of the city. The DNR is watching closely to ensure that residents near the Twin and Ryan lakes system are not affected by the additional water.
Other strategies include the creation of more rain gardens, the installation of underground water holding chambers. There are plans to raise the elevation of Chowen Avenue during a reconstruction project this and next year as part of the five-year street improvement and reconstruction plan.
McCoy warned that pumping water to Ryan and Twin is a temporary fix.
“Right now, Crystal Lake is impaired of nutrients, Twin Lake and Ryan Lake are not,” he said. “Just taking impaired water and chucking it into a lake that is not impaired isn’t gonna fly.”
The first step to a long-term solution is an already underway study by the Shingle Creek Watershed. The watershed reported that the study will be complete in less than two months.
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