(A) Where acceptable natural vegetation exists in buffer strip areas, such vegetation shall be retained. A buffer strip has acceptable natural vegetation if it:
(1) Has a continuous, dense layer of perennial grasses that have been uncultivated or unbroken for at least five consecutive years;
(2) Has an overstory of trees or shrubs with at least 80% canopy closure that have been uncultivated or unbroken for at least five consecutive years; or
(3) Contains a mixture of the plant communities described in sections (1) and (2) above, that have been uncultivated or unbroken for at least five consecutive years.
(B) Notwithstanding the performance standards outlined in division (A) above, the city may determine existing buffer strip vegetation to be unacceptable if:
(1) It is composed of undesirable plant species (including but not limited to reed canary grass, common buckthorn, purple loosestrife, leafy spurge or noxious weeds);
(2) It is lacking a layer of organic thatch or duff;
(3) Has topography that tends to channelize the flow of surface runoff; or
(4) For some other reason it is unlikely to retain nutrients and sediment.
(C) Where buffer strip areas, or a portion thereof, are not vegetated or have been cultivated or otherwise disturbed within five years of the permit application, such areas shall be re-planted and maintained according to each of the following standards:
(1) The soil in wetland buffer strips shall be amended, as necessary, to ensure that the soil has an organic content of not less than 10% and not more than 35%.
(2) Buffer strips shall be planted with a Board of Water and Soil Resources (BWSR) approved seed mix containing 100% perennial native plant species, except for a one-time planting of an annual nurse or cover crop such as oats or rye.
(3) The annual nurse or cover crop shall be applied at a rate of 20 pounds per acre.
(4) Native shrubs may be substituted for forbs. Such shrubs may be bare root seedlings and shall be planted at a rate of 60 plants per acre. Shrubs shall be distributed to provide a natural appearance and shall not be planted in rows.
(5) Any ground cover or shrub plantings installed in buffer strip areas are independent of landscaping requirements set forth elsewhere in the city code and city policy.
(6) Native prairie grasses and forbs shall be planted by a qualified contractor.
(7) No fertilizer shall be used in establishing new buffer strips, except on highly disturbed sites when deemed necessary to establish acceptable buffer strip vegetation and then limited to amounts indicated by an accredited soil testing laboratory.
(8) All seeded areas shall have a two-inch thick application of compost (Mn/DOT Grade 2 Section 3890) or be mulched immediately with clean straw at a rate of one and one-half tons per acre. Mulch shall be anchored with a disk or tackifier.
(9) Buffer strips (both natural and created), shall be protected by silt fence during construction and the fence shall remain in place until the area crop is established.
(D) During the first five years after initial planting, the developer shall submit to the city an annual report documenting the progress for establishment of the buffer strip. The report shall include a map of the buffer strip location, a description of compliance with the performance standards, a description of activities completed within the past year, a description of activities planned for the upcoming year, a map of plant communities within the buffer strip boundary including square footage estimates of the areas of native plantings and invasive or non-native vegetation, and other information as may be requested by the city of Plymouth. Until such time as the buffer strip is accepted by the city, the developer shall be required to replant any buffer strip vegetation that does not survive. After the city has accepted the buffer strip, if the condition of the buffer strip area changes through natural processes not caused by the property owner, the owner shall not be required to re-establish the buffer strip area to meet the standards established in this subdivision.
(Ord. 290, passed 7-7-2020)