(a) Purpose. The Minnesota River Bluff (hereafter "Bluff") in Bloomington is a unique natural resource that occurs at the transition from urban development on the upland, to the Minnesota Valley National Wildlife Refuge and Recreation area in the floodplain of the Minnesota River. The BP Overlay District is intended to preserve the environmental, historic, and scenic value of the Bluff by establishing regulations that protect the integrity and natural character of the Bluff and protect downstream water quality while permitting reasonable use of land along the Bluff. The following plans inventory the Bluff and present the rationale for the provisions of the overlay zoning district: the Bloomington Forward 2040 Comprehensive Plan (2019), The Bluff Report District Plan (1982), the Minnesota River Valley Strategic Plan (2016), the Minnesota River Valley Natural and Cultural Systems Plan (2018), and the Lower Minnesota River Watershed District's Watershed Management Plan (2018).
(b) Definitions. For the purpose of this § 21.208.02
, the following definitions apply unless the context clearly indicates or requires a different meaning.
AGRICULTURAL ACTIVITY. The use of land for the growing or production of agronomic, horticultural, or silvicultural crops, including nursery stock, sod, fruits, vegetables, flowers, cover crops, grains, Christmas trees, and grazing.
BEST MANAGEMENT PRACTICES. Structural or non-structural methods used to treat runoff, including such diverse measures as ponding, street sweeping, filtration through a rain garden, and infiltration to a gravel trench.
CONSTRUCTION. Disturbance to the land that results in a change in the topography, existing soil cover (both vegetative and non-vegetative), or existing soil topography that may result in accelerated stormwater runoff and the movement of sediment into surface waters or drainage systems.
DEVELOPMENT. The construction of any public or private improvement project, infrastructure, structure, street or road, or the subdivision or land.
ELEVATION. Has the meaning of height above mean sea level.
EXCAVATION. The artificial removal of soil or other earth material.
FILL. Any rock, soil, gravel, sand, debris, plant cuttings, or other material placed onto land or into water.
LAND DISTURBING ACTIVITY. Any change of the land surface to include removing vegetative cover, excavation, fill, grading, stockpiling soil, and the construction of any structure that may cause or contribute to erosion or the movement of sediment into water bodies. The use of land for new and continuing agricultural activities does not constitute a LAND DISTURBING ACTIVITY under these standards.
LOCAL WATER PLAN. A plan adopted by each municipality pursuant to M.S.§ 103B.235.
NATURAL VEGETATION. Any combination of ground cover, understory, and tree canopy that stabilizes soils, retains and filters runoff, provides habitat, and recharges groundwater regardless of whether altered by human activity.
OVER-THE-BLUFF STORM WATER DISCHARGE. Sheet surface drainage which flows on the surface of the Minnesota River Bluff, or Nine Mile Creek Bluff, but does not include storm sewers which do not discharge within the Bluff Protection Overlay District.
QUALIFIED PROFESSIONAL. A person, compensated for their service, possessing the education, training, experience, or credential to competently perform or deliver the service provided.
RUNOFF. Rainfall, snowmelt, or irrigation water flowing over the ground surface.
STEEP SLOPE. A natural topographic feature having average slopes of 18 percent or greater measured over a horizontal distance of 25 feet or more.
STORMWATER. Stormwater runoff, snow melt runoff, and surface runoff and drainage.
(c) Applicability. The Bluff Protection Overlay District applies to all land within the city along the Bluff between the Flood Hazard Overlay District and the 800-foot elevation, including the area of the Nine Mile Creek valley south of 106th Street, as well as natural topographic features with an average slope of 18 percent or greater measured over a horizontal distance of 25 feet or more as shown on the steep slopes overlay district map adopted by the Lower Minnesota River Watershed District (LMRWD).
(1) Exception. Properties separated from the applicable area by a street and where surface water runoff drains to the municipal storm sewer system are not subject to the requirements herein.
(d) Uses. All permitted principal, provisional, conditional, interim, limited and accessory uses allowed in the underlying Zoning District are permitted in the Bluff Protection Overlay District subject to the provisions of the primary zoning district.
(e) Standards. In addition to the provisions of the primary zoning district, the following provisions further regulate all development within the Bluff Protection Overlay District:
(1) Development Prohibited below 760-foot elevation.
(A) No structure may be placed in the Bluff Protection Overlay District that would have a floor elevation below 760-foot elevation except as listed below.
(i) Exceptions.
(aa) Public or public utility structures that meet the requirements in § 21.208.02(e)(9).
(bb) Basement floor elevations below the 760-foot elevation may be permitted provided that no portion of any floor area below the 760-foot elevation is within 50 feet of a steep slope.
(cc) Expansion of structures existing on December 27, 1982 that have a floor elevation at or below 760 feet may be permitted provided that the expansion must not exceed the lot coverage below the 760-foot elevation existing on December 27, 1982 by more than 20%. Any expansion is also subject to the standards for steep slope areas.
(2) Steep Slopes.
(A) No variances may be considered from the steep slopes standards.
(B) On natural topographic features with an average slope of 18% or greater measured over a horizontal distance of 25 feet or more, as shown on the LMRWD's steep slopes overlay district map:
(i) No stormwater ponds, swales, infiltration basins, or other soil saturation-type features may be constructed.
(ii) Land disturbing activities that involve the disturbance of 50 cubic yards or more of earth or impact 5,000 square feet or more of surface area or vegetation are subject to the professional certification requirement in § 21.208.02(e)(2)(C).
(iii) Activities that require a permit for development that result in a net increase in impervious surface or stormwater runoff including, but not limited to, grading, building, foundation, or parking lot permits are subject to the professional certification requirement in § 21.208.02(e)(2)(C).
(C) Professional Certification Requirement. A qualified professional or a professional engineer registered in the State of Minnesota must certify the suitability of the area for the proposed activities, structures, or uses and certify the following measures will be taken:
(i) Site stabilization and slope restoration measures, including erosion and sediment control best management practices, as necessary, to ensure the proposed activity will not result in:
(aa) Adverse impacts to adjacent and downstream properties and water bodies;
(bb) Unstable slopes conditions; and
(cc) Degradation of water quality due to erosion, sedimentation, flooding, and other damage.
(ii) Preservation of existing hydrology and drainage patterns. Land disturbing activities must not result in any new water discharge points on steep slopes or along the bluff.
(D) Exemptions from the Steep Slope Standards.
(i) Projects requiring a city issued grading, building, parking lot, or foundation permit that results in a net increase in impervious surface or stormwater runoff, but impacts less than 50 cubic yards and/or less than 5,000 square feet may be issued an exception to the standard for steep slopes. The exception, if issued, must be documented as described in a Memorandum of Agreement between the LMRWD and the city;
(ii) New impervious areas associated with driveway widenings that drain to the street where water runoff is managed by the city's storm sewer system;
(iii) Maintenance, repair, or replacement of existing structures, public roads, utilities, and drainage systems resulting in no net increase of impervious surface;
(iv) Disturbances that are part of an approved local water plan to repair, grade, or re-slope existing steep slopes that are eroding or unstable in order to establish stable slopes and vegetation;
(v) Native plantings that enhance natural vegetation of steep slopes;
(vi) Selective removal of noxious, exotic, or invasive vegetation using locally recognized methods to control and/or minimize their spread;
(vii) Pruning of trees or vegetation that are dead, diseased, pose a public hazard, or removal of vegetation in emergency situations from steep slopes;
(viii) Maintenance of existing lawns, landscaping, and gardens; and
(ix) Agricultural and forestry activities.
(3) Grading. No excavation, fill, or other movement of earth material may take place without issuance of a permit or approval by the issuing authority, with the exception of gardening, fence and deck footings, and selective vegetation removal.
(A) Preceding any construction within the BP Overlay District, erosion control measures must be employed. Following construction, soil stabilization must occur at the earliest possible time. Sodding, ground covers, shrubs and trees may be required by the issuing authority to fulfill this objective.
(4) Tree Removal. No trees greater than 12 inches in diameter measured four feet above ground level may be cut or removed without approval by the City Forester or as approved by the issuing authority.
(5) Water Discharge. Development or land alterations must not result in any concentration of water discharge directly over steep slopes without implementation of best management practices that disperse, filter, and slow the rate of stormwater runoff.
(7) Single-Family Zoning Districts. The following additional standards apply to sites that are zoned R-1, RS-1 or R-1A:
(A) Impervious surface area within the Bluff Protection Overlay District must not exceed 20% of the lot area within the Bluff Protection Overlay District. This standard applies in conjunction with the impervious surface regulations of the underlying zoning district defined in § 21.301.01 and any applicable impervious surface regulations in § 19.57.01.
(B) At 800-foot elevation and lower, structure height must not exceed the 830-foot elevation.
(8) Zoning Districts other than Single-Family Residential (R-1, RS-1 and R-1A). The following additional standards apply to new development in all zoning districts except R-1, RS-1 or R-1A:
(A) The post-development over-the-bluff stormwater discharge rate must be no greater than the pre-development over-the-bluff stormwater discharge rate.
(B) Landscaping requirements, including amount of material, species, and density, must be consistent with the recommendations of the Minnesota River Valley Natural and Cultural Systems Plan and approved by the City Forester.
(9) Public and public utility structures. The following additional standards apply to public and public utility structures:
(A) The placement of public and public utility structures must not negatively impact the visual character or integrity of the Bluff.
(B) Public and public utility structures are limited to 1,500 square feet in floor area.
(C) Retaining walls may not exceed four feet in height and may not be terraced.
(D) Public and public utility structure design and color must be compatible with the surrounding areas and structures.
(E) Public and public utility structures must be screened by landscaping, screen fences or other materials when required by the City Council.
(f) Best management practices. The following best management practices are encouraged to filter, slow, and disperse surface water runoff:
(1) Minimize stormwater runoff over the Bluff.
(2) Limit or reduce impervious surfaces.
(3) Direct runoff from impervious surfaces into a storm sewer system or well vegetated area.
(4) Manage soil erosion.
(5) Plant bare areas with native seedlings or seeds of native species and mulch.
(6) Cover bare soils with biodegradable erosion control blankets and/or logs while vegetation becomes established.
(7) Maintain a healthy, native Bluff environment.
(8) Maintain an unmowed strip, 10 to 20 feet, of vegetation native to the Minnesota River Valley between areas of steep slopes and mowed lawns or paved surfaces.