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• Environmental Assessment Worksheet Nature's Refuge Conservation Development Lino Lakes, Anoka County, Minnesota Draft Document — September 25, 2006 Page 12 General project approaches have been utilized to meet these objectives and include: • Develop understanding of local water table system, collecting data regarding existing water table elevations, soil properties, and surficial hydrology. • Develop a hydrologic model to evaluate existing and proposed conditions. • Control the source of pollutants and develop facilities that will treat the surface runoff prior to entering sensitive areas. • Distribute (as opposed to centralizing) runoff and providing storage and treatment near the source. Among the design elements considered will be micro - grading lots, retention of buffers, maximizing overland flow routes, minimizing grading limits, construction of treatment systems, examination of lot sizes and locations. Specific project design elements include: • A revised roadway section that eliminates conventional curbing and allows sheet flow into an open swale that will provide infiltration and treatment of stormwater • Small sedimentation basins to provide additional treatment prior to discharge to constructed "rain gardens" • Infiltration basins and stormwater ponds within the property limits • Construction staging and control to minimize impact to local infiltration capacities especially at areas of identified treatment facilities. The new roadway crossing at the outlet of the large wetland complex will be constructed to allow adaptive management options such as potential drawdown to accommodate burning activity and/or mimic drought conditions or react to changes in the hydrologic regime. The peak discharge rates to downstream will be consistent with RCWD requirements. Placement of the control structure and subsequent adjustments to water level will follow all permitting requirements of the Rice Creek Watershed District and other authorities. An element of the process for reviewing the wetland mitigation plan for the project will include determining the public agency that will have responsibility for management of the control structure and water level. late ,use. Will 1 xy pubic water e project involve installation pply or appropriation of any section to or changes in including dewatering)? X yes No f yes, as applicable, give location and purpose of any new wells; public supply affected, changes to and water quantities to be used; the source, duration, quan tity and purpose of any appropriations; and unique well numbers and DNR', appropriation permit numbers, if known. Identify any existing and new wells on the site ap. If there are no wells known on site, explain methodology used to determine, There are no known project wells on the site. Any wells discovered during construction will be sealed by a licensed well contractor in accordance with Minnesota Rules Chapter 4725. If required for construction, dewatering will be performed in accordance with a permit obtained from the Minnesota DNR. A temporary water appropriations permit will likely be needed for the excavation of material for the development of ponding areas and as a local borrow site. Eleven (11) piezometers have been installed on the site in April 2006. A data logger has been installed on one piezometer and on the ditch outlet to measure water level fluctuations. The other wells have been read periodically and show a general gradient to the south. Local groundwater has fluctuated over a foot to date in some of the piezometers. These piezometers can be potentially maintained as practicable to monitor the impact of dewatering activities as part of the Mn/DNR Appropriations Permit process. The project will connect to previously constructed municipal watermains, so the 278 expected new homes, would draw water from the City water supply. Thus, assuming usage of 275 gallons per residential unit per day, the project will ultimately require an estimated 76,450 gallons of water per day when all the planned homes are constructed and occupied.