Laserfiche WebLink
steeper 2.5H:1V slope that flattens out in a lawn area between the slope and the lake (approximately 50 <br />feet), based on 2-foot LiDAR contour data provided by the Minnesota Geospatial Information Office. <br /> <br />Following purchase of the property and prior to installation of the retaining wall, the homeowner converted <br />much of the unmaintained area (natural vegetation/weeds) of the backyard to manicured lawn. This area <br />was located in the flatter portion of the backyard slope, leading up to the grade break where the slope <br />steepened. The steeper hillside area remained unmaintained with natural vegetation at that time. <br /> <br />The retaining wall, which was installed in 2021, provides multiple benefits related to slope stabilization, tree <br />protection, and erosion control. <br />▪ The retaining wall stabilizes the pre-existing 2.5H:1V slope, which is steeper than the maximum slope <br />typically recognized as a maintainable slope, 3H:1V. Steep slopes are more difficult to maintain and <br />are vulnerable to erosion. <br />▪ Installation of the retaining walls helps stabilize the existing slope around the three mature large oak <br />trees located near the north end of the walls. These trees, which range in size from 18 inches to 25 <br />inches DBH (Diameter at Breast Height), are important to help maintain the overall stability of the <br />slope due to their large root systems in comparison to grasses and weeds. <br />▪ The areas immediately upgradient from the top wall tier and between the two walls are now much <br />flatter than they were prior to the retaining wall installation. This has the effect of slowing down <br />stormwater runoff that helps to reduce erosion and increase infiltration, resulting in a reduced <br />volume of stormwater (and potential sediment and nutrients) from reaching Lake Minnetonka, <br />contributing to enhanced water quality. <br />▪ The location of the wall on the north side was intended to minimize the excavation impacts to the <br />three mature trees and the roots that help stabilize the slope near the trees. <br />The retaining walls eliminated a steeply sloped eroded area that was difficult to maintain and provides some <br />additional storm runoff retention with flatter planted areas they created. The walls were also located to <br />preserve mature trees. <br /> <br />Kenneth W. Horns, P.E. <br /> <br /> <br />140