05-22-2019 Council Packet - Laserfiche WebLink

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STAFF REPORT TO:Mayor Keis and Members of City Council FROM:Bill Dircks, Public Works Director Tina Carstens, Ramsey Washington Metro Watershed District DATE:May 16, 2019 RE:Twin Lake Water Level Tina Carstens from the Ramsey Washington Metro Watershed District and Brandon Barnes from Barr Engineering (consulting engineer for the Watershed District) will be presenting information regarding Twin Lake and the rise in the water level over the past three years. Following the presentation there will be time for questions but this is not a public hearing. Over the past several years, the water surface elevation of Twin Lake has continued to rise. Twin Lake is essentially a landlocked basin because it has no normal water level outlet. Groundwater and evaporation are the main ways the water can leave the lake. Water comes into the lake from the north and the south ends of the lake. When water levels are high enough, water can also leave the lake area from the south end, where the overflow of the whole system is located, into a MnDOT pond along Interstate 694. The City of Little Canada has requested the Ramsey-Washington Metro Watershed District (RWMWD) provide technical resources to evaluate the reason for the dramatic increase in the lake levels and identify how the drainage system works. RWMWD also evaluated the risk to homes on the lake due to surface flooding. The City first held a public meeting on October 8, 2018. Here’s a link to the presentation that was given at that meeting. RWMWD reviewed the elevation survey results of the storm water structures around the lake. The Watershed District also reviewed the precipitation records and regional groundwater information. At that meeting, the residents had a number of questions and concerns about the water levels. There were concerns about other potential sources of water that were contributing to the high water levels. The City and Watershed District agreed to follow up on those concerns with another public meeting. That meeting was held on March 12, 2019. Here is a link to that presentation. At the March meeting, additional information was given to show that there was not a significant overflow from East Vadnais Lake into Twin Lake and changes to the land cover on the parcel to the south and east of Twin Lake did not contribute to the fast rise in 2016. Modeling and rainfall record