Agenda - Planning Commission - 02/02/2017

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subd. 5 (2015). While the statute does not name specific tributaries, the DNR, with input from local governments and interest groups, identified the Crow, Minnesota, Rum and Vermillion rivers as the key tributaries with confluences with the Mississippi River within the MRCCA. These four watercourses are the only major rivers with a confluence with the Mississippi River within the MRCCA. Because not all communities have enacted shoreland protection as required by statute for those tributary rivers, it is important to provide comparable protection for those portions of these tributaries that lie within the boundaries of the MRCCA. The proposed setbacks for these tributaries are consistent with the state shoreland and scenic river standards, and with setbacks currently in place in local zoning ordinances. The setbacks for these tributaries are controlled by the MRCCA district in which they lie. The 150-foot setback in the "rural and open space" district (CA-ROS) is consistent with the Wild and Scenic River setback for scenic rivers. See Minn. R. 6105.0110, subp. 3.B. (2015). The 75-foot setback in the "river neighborhood" (CA -RN), "river towns and crossings" (CA -RTC), and "separated from river" (CA - SR) districts is consistent with the state shoreland rules setbacks for unsewered general development and sewered recreational development river segments. Minn. R. 6120.3300, subp. 3 (2015). Bluff setbacks and the bluff impact zone. The MRCCA contains major geological bluff features that are prone to erosion and natural instability. Bluff failure and erosion are significant concerns in the MRCCA, as evidenced by slope failures in recent years in Mendota Heights, Mendota, Lilydale, and Minneapolis. Bluff setback requirements are necessary to protect steep, unstable slopes, to limit the visual impact of structures on scenic resources, to protect property investments, and for the health, safety and welfare of the public. Setbacks can prevent severe environmental consequences such as slope failures and ongoing problems such as erosion. The prohibition of structures within a certain distance from the top edge of a bluff (the bluffline) promotes bluff stability by minimizing disturbance, maintaining natural vegetation, and preventing excessive runoff. Setbacks are commonly used to address runoff from the top of a bluff and land alteration that can exacerbate instability, while protecting structures from dangers of slope failure. This rule also assures uniform bluff setback requirements across the MRCCA corridor, a concern raised by local units of government. Subpart 3 establishes both a bluff impact zone and a bluff setback within the MRCCA corridor. The bluff impact zone includes the bluff and an area within 20 feet of all sides of the bluff as defined in proposed Minn. R. 6106.0050, subp. 9. The construction or expansion of structures within this highly sensitive area is prohibited. The bluff setback area extends back from the bluffline. Development between the bluff impact zone and the bluff setback line is restricted but is not necessarily prohibited (see Exemptions below). Bluff setbacks by district. The width of the bluff setback varies across the districts: • CA-ROS: The greatest bluff setback, 100 feet, is proposed in the" rural and open space" district, an area characterized by public parklands and rural residential development. This standard is derived from the standards for the rural open space district in the Interim Development Regulations in Executive Order 79-19, and is also consistent with setback standards in many local ordinances in these areas. 49