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07-10-2019 Workshop & Council Packet
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07-10-2019 Workshop & Council Packet
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At the last meeting, mention was made of the 1993 and 2007 studies of Twin Lake that Barr <br />Engineering had conducted for the Ramsey-Washington Regional Watershed. The 1993 study states <br />that pumping or the installation of a pipe should take place if the lake were to reach an action level of <br />870.5 for Twin Lake. This was based on an old methodology with the lake level starting at 870.7 and a <br />100-year 30-day snowmelt event. It was projected that Twin Lake would rise to 875.1 under this <br />model. <br />Since that time, the Watershed District has made improvements to its stormwater modeling to better <br />characterize the drainage patterns and available floodplain storage within the Twin Lake watershed. <br />For example, in the spring of 2019, the Watershed District used current stormwater models along with <br />estimates of snowpack prior to the spring melt, and rainfall measurements to simulate lake levels. This <br />analysis indicated that without the additional inflow from West Vadnais, the water level in Twin Lake <br />would have remained below the flood level that was indicated in the 1993 report. <br />The information from both the 1993 and 2007 Twin Lake Hydrologic Studies have been utilized over <br />the past twenty-five years and several improvements have been made. As new information becomes <br />available, the findings and modeling are updated to reflect the current conditions. Staff reviewed many <br />of the previous findings with Barr Engineering and the Watershed District and feels confident that this <br />information has been taken into considerations as we deal with the current conditions around Twin <br />Lake. <br />Recommended Action: <br />Staff recommends that the City Council approve a Motion directing staff to request an amendment to <br />the permits from the DNR and MnDOT to allow pumping to the 872 level.
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