2003-08-14_AgendaPacket - Laserfiche WebLink

Home

Financing of any required improvements has not been considered. Negotiations with Ioc of government and. neighboring watershed organizations will be required. ~ units 7.0 SUIvZMARy AND ~Cp~~NDATIONS It is currently the policy of the SPWU to maintain Vadnais Lake levels below the outlet elevation, thus preventing outflow to Twin Lake. Assuming the future continuous operation of the water u ' ' and a contu2uance of present practices, it would appear that Twin Lake will not be called uponl to' accommodate overflow from Vadnais Lake. A culvert should be constructed through the existing dike upstream of I-694. The culvert should be at the same elevation as the 1-694 cuIyerts (about 872.3) and should have a flap gate to prevent back flow of I-694 runoff to Twin Lake, Construction of the culvert could be delayed until the need is demonstrated by lake levels at or above the action Ievels. Development reviews must preserve an outlet route between the Lake and the proposed culvert at the I-694 dike.. Provided that flow from Vadnais Lake does not occur, Twin Lake should be managed to allow 100-year frequency rainfall and snowmelt events without experiencing Lake levels above 875 feet 1VISL. The RED should install and monitor a lake elevation gage on Twin. Lake.. If pre-snowmelt or summer water levels exceed 870.5 feet, pumping to Vadnais Lake. or County Ditch I6 should be considered to preserve storage capacity for accommodating storm runoff below Elevation 875 until the culvert can be installed, If the projected 63 cfs outflow from the Vadnais chain of lakes needs to be accommodated, consideration should be given to routing this flow azound Twin Lake to preserve the quality of Twin Lake. This diversion may also be less costly than the 1..694 culvert upgrades that would be required to route the flow through Twin Lake. If overflow to Twin Lake were permitted, the increased outflow capacity of the lake would be expected to sacrifice the water quality advantages that Twin Lake currently enjoys. The RWMWD should evaluate and select an alternative overflow route so that future development reviews can consider implications with the selected route, should its use ever be required. 23\6212641T~VINLAKE.Kp7'1IOygI 12