(1) Stormwater management. A permit incorporating an approved stormwater management plan shall be required for all proposed land development activity including public linear projects, unless otherwise exempted in this chapter, which meets any or all of the following:
(a) A development, redevelopment or reconstruction, except public linear projects, that creates or reconstructs 10,000 square feet or more of impervious surface, including smaller individual sites that are part of a common plan of development that may be constructed at different times.
(b) A subdivision of an area exceeding one acre. This includes subdivision for single-family residential, multi-unit residential, commercial, industrial, or institutional development.
(c) For public linear projects, a permit is required when one or more acres of impervious surface will be created or reconstructed through multiple phases or connected actions of a single project, as defined by the city.
(d) Any land-disturbing activity, regardless of size, that the city determines would otherwise cause an adverse impact to an environmentally sensitive area or other property including areas within floodplain and shoreland districts.
(2) Exceptions.
(a) A permit is not required for single-family residential construction on an individual lot of record, if the proposed impervious surface of the lot is less than 10,000 square feet, excluding the driveway. Stormwater management requirements do not apply to development of an individual lot within a residential subdivision if it conforms to an approved development plan.
(b) Stormwater management requirements do not apply to sidewalks and trails ten feet wide or less that are bordered down-gradient by vegetated open space or vegetated filter strip with a minimum width of five feet.
(c) Stormwater management requirements do not apply to bridge spans, mill, reclamation and overlay projects.
(d) Stormwater Management Requirements do not apply to single-family residential subdivisions creating seven or fewer lots that:
1. Establish no new public roadway; and
2. Includes no private roadway/driveway serving three or more lots.
(3) Stormwater management performance standards. A stormwater management plan shall be submitted with the permit application for a project equaling or exceeding the threshold of § 1011.011(1). The plan shall be designed to reduce the impacts of development by maintaining predevelopment hydrological conditions in the following ways:
(a) Use of natural topography. The applicant shall incorporate the use of natural topography and land cover such as natural swales and depressions as they exist before development to the degree that they can accommodate the additional flow of water without compromising the integrity or quality of the receiving waterbody.
(b) Minimize impact to natural features. The development shall minimize impact to significant natural features. Applicant shall review the site for natural features protected under city, state or federal requirements, including steep slopes, wetlands, wooded areas, endangered or threatened species or species of concern habitat, areas designated by the county biological survey, greenways, parks and open space, groundwater recharge areas, wellhead or surface water protection areas or regional stormwater pond locations.
(c) Conveyance system. Wherever possible untreated and treated stormwater runoff shall be conveyed in facilities open to the atmosphere (e.g. swales, vegetated buffer strips, energy-dissipating structures, and the like) rather than through enclosed pipes, so as to decrease runoff velocity, allow for natural infiltration, allow suspended sediment particles to settle, and to remove pollutants.
(d) Proposed development design shall:
1. Maintain or decrease runoff volume, where practicable as determined by the City Engineer;
2. Decrease erosion and sedimentation;
3. Maintain or decrease flow frequency, duration, and peak runoff rates;
4. Increase infiltration (groundwater recharge) or filtration;
5. Maintain existing flow patterns;
6. Reduce time to peak flows by increasing the time of concentration to and through storm sewers;
7. Provide storage of stormwater runoff on site;
8. Avoid channel erosion;
9. The proposed project must not adversely affect water level off the site during or after construction;
10. The proposed activity may not reduce hydraulic efficiency of the drainage ways at any point up-gradient of the applicant's parcel boundary; and
11. A combination of Stormwater BMP’s may be used to meet the requirements of divisions 6, 7, or 8.
(e) Landlocked basins. A landlocked basin may be provided an outlet only if it:
1. Retains a hydrologic regime that complies with the requirements of the local governmental unit (LGU) responsible for administration of the Wetland Conservation Act (WCA);
2. Provides sufficient dead storage volume to retain back to back 100-year, 24-hour rainfalls and runoff; and
3. Does not create adverse downstream flooding or water quality conditions as a result of increased discharge rate or volume, or other factors.
(f) All plans shall be consistent with National Pollutant Discharge Elimination permit (NPDES) requirements, the Lino Lakes engineering design standards, the Lino Lakes stormwater design standards, and the filing or approval requirements of Rice Creek Watershed District, Vadnais Lakes Watershed Management Organization, Anoka County, Minnesota Department of Natural Resources, Minnesota Department of Transportation, Minnesota Pollution Control Agency, U.S. Army Corps of Engineers, State of Minnesota Stormwater Manual or other regulatory agencies.
(4) Stormwater management plan modeling requirements. The city adopts by reference RCWD Rule C4, Modeling for Stormwater Management Plans, as amended.
(5) Water quality treatment. The city adopts by reference RCWD Rule C6, Water Quality Treatment as amended.
(6) Peak stormwater runoff control. The city adopts by reference RCWD Rule C7, Peak Stormwater Runoff Control as amended.
(7) Design criteria. Best Management Practices shall be designed in accordance with the following standards:
(a) Infiltration BMP’s. The city adopts by reference RCWD Rules C.9.(a) as amended.
(b) Water reuse. The city adopts by reference RCWD Rules C.9.(b) as amended.
(c) Biofiltration and filtration BMP’s. The city adopts by reference RCWD Rules C.9.(c) as amended.
(d) Stormwater ponds. The city adopts by reference RCWD Rules C.9.(d) as amended.
(e) Soil borings. The city adopts by reference RCWD Rules C.9.(e) as amended.
(f) Outfalls. The city adopts by reference RCWD Rules C.9.(f) as amended.
(g) Freeboard requirements. All new residential, commercial, industrial and other habitable or non-habitable structures, and all stormwater basins, must be constructed so that the lowest floor and lowest entry elevations of structures comply with Table 1.
Table 1. Low floor and low entry freeboard requirements | |||||||||
Regional Flood Elevatio ns | Local Detention Basins & Wetlands | Infiltration Basins | Rain Gardens | Groundwater1 | |||||
Elevation | 100 year | EOF | 100 year | EOF | Bottom | 100 year | EOF | EOF | Seasonal High Level |
Low Floor Freeboard | 2-ft | 1-ft | 0-ft | N/ A | 0-ft | N/A | N/ A | N/A | 4-ft |
Low Entry Freeboard | N/A | N/ A | 2-ft | 1-ft | N/A | 2-ft | 1-ft | 0.5-ft | N/A |
1 The seasonal high groundwater level shall be determined within 12 months of proposed construction of the structure by a soil scientist or geotechnical engineer registered in the State of Minnesota as indicated by redoximorphic features such as mottling within the soil or by direct groundwater observation. | |||||||||
(h) Within a landlocked basin, lowest floor elevations must be at least one foot above the surveyed basin overflow elevation. Where a structure is proposed below the runoff elevation of a land-locked basin, the low-floor elevation will be a minimum of two feet above the high water level as determined from an estimate of high water levels determined from the highest of either the 100-year, ten-day runoff event or back-to-back 100-year, 24-hour rainfalls. Aerial photos, vegetation, soils, and topography will be used to derive a "normal" water elevation for the basin for the purpose of computing the 100-year elevation.
(8) Drainage and utility easements.
(a) If a stormwater management plan involves direction of some or all runoff off of the site, it shall be the responsibility of the applicant to obtain from adjacent property owners any necessary easements or other property interests concerning flowage of water.
(b) Easements are required for all stormwater management facilities, stormwater conveyances and on-site floodplain and shall extend a minimum of ten feet beyond the basin's normal water level or the 100-year storm high water level elevation, whichever is greater.
(c) Easements are required for all outlet swales and ditches, and for overland overflow routes located downstream of basins located on site.
(d) If the storm sewer is to be installed less than ten feet deep within private property, the easement shall be a minimum of 20 feet wide. If the storm sewer is ten feet or greater, the easement shall be twice as wide as the depth.
(e) Easements necessary for maintenance vehicle access are required for all of the above where not directly available on a public road.
(9) Wetlands. Runoff shall not be routed directly to wetlands without first passing through an appropriate settling or approved pre-treatment basin. Said basins must meet standards for volume and flow directed to the basin.
(a) A protective buffer strip of natural vegetation shall surround all wetlands as follows:
1. Where RCWD is the Local Government Unit (LGU) for administration of the Minnesota Wetland Conservation Act (WCA) the city adopts RCWD Rule F.6.(e), as amended. Wetlands not subject to RCWD Rule F.6. (e) shall have a minimum buffer width of ten feet.
2. Where Vadnais Lakes Area Water Management Organization (VLAWMO) is the LGU for administration of WCA, the city adopts VLAWMO Water Quality Standards Section 11, as amended.
(b) Wetlands must not be drained, filled, or altered, wholly or partially, unless in compliance with and permitted under the most current rules adopted by the Minnesota Board of Water and Soil Resources in the Wetland Conservation Act (WCA). Wetland replacement must be guided by the following principles in descending order:
1. Avoidance.
2. Minimization.
3. Mitigation.
(c) Permits to work in wetlands must be obtained from the local water management organizations, acting as local governmental units (LGU), with respective jurisdiction with the City of Lino Lakes to administer the WCA.
(d) Permanent boundary markers, in the form of signage approved by the City of Lino Lakes, should be installed prior to final approval of the required clearing and grading plan.
(10) Comprehensive Stormwater Management Plan. The City of Lino Lakes may develop a comprehensive stormwater management plan (CSMP) as an alternative way to meet the stormwater requirements of the local watershed agencies for development within a defined area and a common resource of concern (ROC). The CSMP will be submitted to the applicable watershed district for review and must comply with the requirements of the watershed district. The following Comprehensive Stormwater Management Plans are adopted and in effect:
(a) Legacy at Woods Edge Development (LWED) CSMP (August 2016). The LWED is defined as that area within the City of Lino Lakes bounded by I-35W to the north, Town Center Parkway to the south, and Lake Drive to the west. The following LWED CSMP policies and regulations supersede portions of § 1011.011 within the LWED as follows:
1. Subpart (5) Water Quality Treatment and Subpart (6) Peak Stormwater Runoff Control. Private development shall not exceed the impervious areas listed in Appendix E of the LWED CSMP. If developers choose to exceed the impervious limits, they will be required to address any additional stormwater requirements within that parcel at their own expense and demonstrate how the additional runoff will be treated to meet the applicable Rice Creek Watershed District rules. Any such best management practices (BMP’s) will be considered private and be maintained by the owner/developer of the parcel.
(b) Northeast Lino Lakes Drainage Area (NEDA) CSMP (September 2018). The NEDA is defined as that area within the City of Lino Lakes bounded by Main Street to the south, the City of Hugo to the east, Lake Peltier to the west and Rehbein Street to the north. The following NEDA CSMP policies and regulations supersede portions of § 1011.011 with the NEDA as follows:
1. Subpart (5). Water Quality Treatment. Water quality treatment requirements shall be met through a variety of measures as is feasible on a regional or development-by-development basis. On-site infiltration is not feasible for most of the NEDA due to poor soils, high groundwater and the presence of wetlands. As development proceeds within the NEDA, developers shall be required to demonstrate that infiltration is not feasible on-site before utilizing any regional basins or other BMP alternatives.
2. Subpart (6). Peak Stormwater Runoff Control. Private development shall be restricted to an allowable flow rate of 0.1 cubic feet per second (cfs) per acre for the 100-year, 24-hour peak discharge rate. This will result in a maximum peak discharge rate from the NEDA into Peltier Lake of no more than 135 cfs. This restriction may be met through a combination of rate control practices on a regional or development-by-development basis.
(11) Stormwater management plan required exhibits. The stormwater management plan shall be prepared and signed by a duly licensed engineer in the State of Minnesota. The following exhibits must accompany the permit application: two plan sets, full size (22 inches by 34 inches); and one electronic copy in a .pdf format. All plan sets shall also be submitted electronically in a .dwg format or as otherwise determined by the City Engineer.
(a) A grading, erosion and sediment control plan and, for projects that require a NPDES permit, a stormwater pollution prevention plan (SWPPP).
(b) Stormwater management plan including existing and proposed hydrologic calculations for total runoff volume and peak discharge rates as described in this chapter, including:
1. A narrative including a project description, discussion of BMP selection, incorporation of infiltration BMPs, and revegetation plan for the project site;
2. Delineation of all drainage areas, including contributing runoff from off-site areas, proposed and existing subwatersheds on-site, emergency overflows, and drainage ways;
3. Existing, proposed, and total amount of impervious surfaces created by the project;
4. Existing and proposed runoff curve numbers;
5. Time of concentration used in calculations; and
6. Existing and proposed total runoff volume and peak discharge rates for the two-, ten-, and 100-year critical events utilizing NOAA Atlas 14.
(c) Property of lines and delineation of lands under ownership of the applicant.
(d) Locations of all stormwater management practices, infiltration areas, and areas not to be disturbed during construction.
(e) Location of all drain tiles on the project site shall be identified.
(f) Location and engineered designs for structural stormwater management practices including stormwater treatment devices that remove oil and floatable material (e.g., basin outlets with submerged inlets).
(g) Normal water level, high water level, and emergency overflow elevations for the site and all ponding systems related to NAVD88.
(h) Identification of existing and proposed one-foot contour elevations within the project site related to NAVD88.
(i) Geotechnical analysis including soil borings at all proposed stormwater management facility locations ASTM D5921 and D2488.
(j) Provisions for groundwater management (dewatering), including subsurface drains, disposals, ponding and flood controls.
(k) Completed Rice Creek Watershed District worksheet explaining better site design techniques that were evaluated during project design, the results of the evaluation of each and for any techniques deemed infeasible.
(l) A long-term maintenance plan and schedule for all permanent stormwater practices, along with the identity of the party responsible for the maintenance of the project. The maintenance responsibility must be memorialized in a document executed by the property owner in a form acceptable to the city and filed for record on the deed.
(m) Before work is deemed complete, as-built plans must be submitted demonstrating that at the time of final stabilization, stormwater facilities conform to design specifications.
(n) Other project site-specific submittal requirements as may be required by the city.
(Ord. 09-15, passed 10-26-2015; Am. Ord. 10-22, passed 1-9-2023)