(A) General. The following activities must be authorized by permit, except for excavation for permitted structure, drives, sewer systems and parking areas:
(1) Grading and filling in the shore or bluff impact zone; and
(2) Any alterations of the natural topography when the slope of the land is toward a public water or watercourse involving the movement of more than ten cubic yards of material in a bluff or shore impact zone or more than 50 cubic yards of material anywhere else within a shoreland area.
(B) Conditions. The following conditions shall apply.
(1) The smallest amount of bare ground is exposed for as short a time as feasible.
(2) Four inches of topsoil is placed, temporary ground cover such as mulch is used and permanent ground cover such as sod is planted.
(3) Methods to prevent erosion and trap sediment are employed.
(4) Fill is stabilized to acceptable engineering standards and must not create an unstable slope.
(5) Plans to place fill or excavated material on steep slopes must be reviewed by a qualified professional for continued slope stability and must not create finished slopes of 30% or greater.
(6) Fill or excavated material must not be placed in bluff impact zones.
(7) Fill placed in a public water below the ordinary high water line requires a DNR waters permit and a Corps of Engineers permit.
(8) Excavation in the bed of public waters requires a DNR waters permit and a Corps of Engineers permit.
(9) Only clean fill consisting of sand, gravel or rock will be allowed where contact with water is anticipated. Mineral soil may be allowed elsewhere.
(10) Alterations to topography must only be allowed if they are accessory to permitted or conditional uses and do not adversely affect adjacent or nearby properties.
(C) Wetlands. Grading or filling in any protected wetland is prohibited unless authorized by federal, state, county and local permitting agencies.
(D) Public waters. Connections to public waters of boat slips, canals, lagoons, harbors and similar inland excavations are prohibited.
(E) Roads, driveways and parking areas. Public and private roads, driveways and parking areas must be designed to take advantage of natural vegetation and topography to achieve maximum screening from public waters.
(1) Roads, driveways and parking areas shall meet structure setbacks and shall not be placed within bluff and shore impact zone, when other reasonable and feasible placement alternative exist. If no alternatives exist, they may be placed within these areas, and shall be designed to minimize adverse impacts.
(2) Private watercraft access ramps, approach roads and access-related parking areas are prohibited on lakes with public access or more than one privately-owned but public access. On lakes with no public access, private watercraft access ramps, approach roads and access-related parking areas may be placed by permit within shore impact zones; provided, the vegetative screening and erosion control conditions of this section are met.
(F) Ice ridges.
(1) Annual ice ridges may be regraded to their original shoreline contour with a permit provided that the work is completed in the year in which the annual ice ridge occurred. Any such regrading shall meet the following standards:
(a) The ice ridge resulted from ice action within the last year.
(b) The total length of shoreline zone to be affected does not exceed 50 feet.
(c) All ice ridge material that is composed of muck, clay, or organic sediment is deposited and stabilized at an upland site above the ordinary high water level of any public water.
(d) All ice ridge material that is composed of sand or gravel is removed or graded to conform to the original cross-section and alignment of the lakebed, with a finished surface at or below the ordinary high water level.
(e) No additional excavation or placement of fill material occurs on the site.
(f) All exposed areas are immediately stabilized as needed to prevent erosion and sedimentation.
(g) Removal or grading of an ice ridge must not disturb emergent aquatic vegetation, unless authorized by an aquatic plant management permit from the Department of Natural Resources or the Army Corps of Engineers.
(2) Historic ice ridges. On those ice ridges with well-established vegetative cover, alterations for lake access shall require a permit and comply with the following standards:
(a) One alteration site is allowed per conforming residential lot, single nonconforming lot of record or per group of contiguous nonconforming lots in the same ownership.
(b) On residential lots, the bottom width shall not exceed 15 feet, with side slopes no steeper than 2:1 at each end.
(c) On waterfront commercial lots, the maximum bottom width shall be 25 feet with 2:1 side slopes at each end.
(d) Berms of no less than 12 inches above original grade level or one foot above the OHWL. whichever is higher, shall be left on all ice ridge alterations to prevent upland runoff entry.
(e) All disturbed material shall be removed from the site.
(f) Any alteration below the OHWL may require approval from the Department of Natural Resources and/or U.S. Army Corps of Engineers.
(G) Riprap. The city encourages the use of riprap only as a last resort to control shoreline erosion. Other methods should be used, including the planting of native, deep rooted vegetation. If riprap has been found to be the only tool available following consultation with the Department of Natural Resources, another appropriate state agency or the county at on on-site meeting attended by a city representative, riprap installation shall have the following standards.
(1) Gradation. A well-graded mixture of rock sizes should be used instead of one uniform size.
(2) Quality of stone. Riprap must be durable so that freeze/thaw cycles do not decompose it in a shore time; most igneous stones such as granite have suitable durability.
(3) Riprap depth. The thickness of riprap layers should be at least two times the maximum stone diameter.
(4) Vegetation.
(a) Existing vegetation on the shoreline and in the water should be maintained without disturbance.
(b) All bare soil on the slope above the riprap should be stabilized with seed and mulch or sod.
(c) Wooded, deep-rooted vegetation should be planted among the riprap to help stabilize and create wildlife habitat.
(5) Filter material. Filter material is usually required between riprap and the underlying soil surface to prevent soil from moving through the riprap; a filter cloth material or a layer of gravel is usually used for the filter.
(a) Leaching protection. Leaching can be controlled by installing a riprap gradation small enough to act as a filter against the channel base material, or a protective filter can be installed between the riprap and the base material.
(b) Riprap limits. The riprap should extend for a maximum flow depth, or to a point where vegetation will be satisfactory to control erosion.
(c) Curves. Riprap should extend to five times the bottom width upstream and downstream of the beginning and ending of the curve as well as the entire curved section.
(d) Riprap size. The size of riprap to be installed depends on site-specific conditions.
(e) Riprap prohibitions. Slopes on which riprap is used to stabilize shorelines shall be no steeper than 2:1.
(6) Maintenance. Inspections should be made of all sites immediately after the first rainfall following installation of riprap. This is particularly important in areas where riprap that is displaced during the storm would impact culverts. Thereafter, riprapped sites should be checked following large storms, especially those which are near or exceed the storm frequency used in the design. Displaced riprap should be removed from its downstream location and new riprap placed according to the specifications above.
(H) Retaining walls. A retaining wall may be installed with a permit in-between the OHWL and the structure setback provided the following standards are met:
(1) (a) The Zoning Administrator determines that there is no other alternative to control erosion.
(b) No tier of the retaining wall shall exceed four feet in height without a plan signed by a Minnesota licensed professional engineer.
(c) Construction complies with all impervious surface standards of the zoning district.
(d) The wall cannot be longer than half the lot width or 30 feet in length, whatever is more restrictive.
(e) All grading and filling standards of this chapter shall be followed.
(2) A retaining wall may be installed without a permit behind the structure setback provided that: Construction complies with all impervious surface standards of the zone.
(Ord. 906-2011, passed - -2011; Ord. 906, 1st Series, passed 5-9-2017) Penalty, see § 152.999
Editor’s note:
This section was amended by the city at a public hearing on 9-5-2012.