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A. Design Criteria: At minimum erosion control practices, sediment control practices, and waterway crossings shall meet the design criteria set forth below and shall be consistent with city of Rosemount general specifications and "Plan Requirements And Design Guidelines" manual.
1. Cut and fill slopes shall be no greater than four to one (4:1), except as approved by the city engineer.
2. Clearing, except that necessary to establish sediment control devices, shall not begin until all sediment control devices have been installed and have been stabilized.
3. Phasing may be required on all sites based on site specifics, with the size of each phase to be established at plan review and as approved by the city engineer/city of Rosemount.
4. Proposed erosion control measures may be approved by the city engineer as part of a grading plan review toward grading or building permit approval. Erosion control may be specified by the city engineer as part of a site survey for individual building permits. Erosion control may also be specified by the city engineer as needed and deemed appropriate during the construction and postconstruction periods separate from the process described below.
B. Specifications: At a minimum, applicants shall meet the specifications set forth below and observe the standards established in NPDES construction general permit requirements and the city's surface water management plan.
1. Soil Stabilization: Soil stabilization shall be completed in a time period as specified by the NPDES construction general permit and the city's general specifications and standards. The city of Rosemount may require the site to be reseeded or a nonvegetative option employed.
2. Seeding: Seeding shall be in accordance with seeding specifications. All seeded areas shall be fertilized, mulched, and disc anchored as necessary for seed retention.
3. Special Techniques: Special techniques that meet the design criteria outlined in "Plan Requirements And Design Guidelines" shall be in place on steep slopes or in drainageways and shall be used to ensure stabilization. Special techniques may include: temporary sediment basins, slope draining and terracing.
4. Soil Stockpiles: Soil stockpiles which shall be inactive for a period of seven (7) or more days must be stabilized or covered at the end of each workday. Stockpiles shall include perimeter sediment controls and must not be placed in natural buffers or surface waters, including stormwater conveyances.
5. Ninety Percent Coverage: The entire site must be stabilized at a ninety percent (90%) coverage, using a heavy mulch layer or another method that does not require germination to control erosion, at the close of the construction season.
6. Site Development Sediment Controls: Site development sediment controls practices shall include those identified in the city's general specifications including, but not limited to:
a. Settling basins, sediment traps, or tanks.
b. Protection for adjacent properties by the use of a vegetated buffer strip in combination with perimeter controls.
c. Perimeter control including machine sliced silt fence or other city approved BMP, which shall be in place before, during and after grading of the site. Fencing shall be removed only after seventy percent (70%) stabilization. (Ord. 2015-01, 2-17-2015; amd. Ord. 2015-05, 7-7-2015)
d. Designated as a concrete washout area. (Ord. 2015-05, 7-7-2015)
e. Designated as a temporary construction staging area.
7. Temporary Sediment Basins: For sites that have more than ten (10) acres of disturbed soil that drains to a common location (or 5 or more acres for special or impaired waters), one or more temporary sediment basins shall be constructed. Use of temporary basins is encouraged when construction projects will impact steep slopes or when highly erodible soils are present. The basin shall provide treatment to the runoff before it leaves the construction site or enters surface waters. The temporary sediment basins must be designed and constructed as follows:
a. Provide live storage for a calculated volume of runoff from a 2-year, 24-hour storm from each acre drained to the basin. All basins shall provide at least one thousand eight hundred (1,800) cubic feet of live storage from each acre drained or more.
b. For basins where the calculation in subsection B7a of this section has not been performed, a temporary sediment basin providing three thousand six hundred (3,600) cubic feet of live storage from each acre drained to the basin shall be provided for the entire drainage area of the temporary basin.
c. The outlet structure must be designed to withdraw water from the surface in order to minimize the discharge of pollutants.
d. The basin outlet shall be designed to prevent short circuiting and the discharge of floating debris.
e. Ensure the basin can be completely drawn down to conduct maintenance activities.
f. Include energy dissipation on the outlet of the basin and a stabilized emergency overflow to prevent failure of pond integrity.
g. Be located outside of surface waters or any buffer zone, and be designed to avoid draining water from wetlands unless appropriate approval from the U.S. army corps of engineers and the Minnesota department of natural resources is obtained.
h. If installation of a temporary sediment basin is not feasible, equivalent sediment controls such as smaller sediment basins, and/or sediment traps, silt fences, vegetative buffer strips, or any appropriate combination of measures are required for all down slope boundaries of the construction area and for side slope boundaries where appropriate. Determination of feasibility shall be documented in the erosion and sediment control plan.
8. Individual Construction Site Sediment Controls: Individual construction site sediment controls shall be installed as specified in the city's "Plan Requirements And Design Guidelines" and shall include:
a. Rock construction entrance (driveway);
b. Perimeter controls including silt fence in place before, during and after grading of the site. Fencing shall be removed only after proper turf establishment.
9. Waterway And Watercourse Protection: Waterway and watercourse protection requirements shall include stabilization of the watercourse channel before, during and after any in-channel work consistent with the city's general specifications.
a. A temporary stream crossing must be installed and approved by the local government unit and regulating agency if a wet watercourse will be crossed regularly during construction.
b. The watercourse channel shall be stabilized before, during, and within twenty four (24) hours after any in-channel work.
c. No in-water work shall be allowed in public waters during the MNDNR'S work exclusion dates.
d. Prior to placement of any equipment into any waters, all equipment must be free of aquatic plants and nonnative animals.
All on site stormwater conveyance channels shall be designed according to the criteria outlined in this document. Stabilization adequate to prevent erosion located at the outlets of all pipes and paved channels is required.
10. Site Dewatering: Site dewatering shall be conducted pursuant to the city's general specifications document. Water pumped from the site shall be treated by temporary sediment basins, grit chambers, sand filters, or other controls as appropriate to ensure adequate treatment is obtained and that nuisance conditions will not result from the discharge. Discharges from the site shall not be released in a manner that causes erosion, scour, sedimentation or flooding of the site, receiving channels or wetlands.
11. Waste And Material Disposal: All waste and unused building materials (including garbage, debris, cleaning wastes, wastewater, toxic materials or hazardous materials) shall be properly disposed of off site and not allowed to be carried by runoff into a receiving channel or storm sewer system.
a. Solid Waste: All unused building materials and waste (including, but not limited to: collected sediment, asphalt and concrete millings, floating debris, paper, plastic, fabric, etc.) must be disposed of accordingly and shall comply with disposal requirements set forth by the MPCA.
b. Hazardous/Toxic Waste: Paint, gasoline, oil and any hazardous materials must be properly stored, including secondary containment, to prevent spills, leaks or other discharges. Access to the storage areas must be restricted to prevent vandalism. Storage and disposal of hazardous or toxic substance must be in compliance with the requirements set forth by the MPCA.
c. Liquid Waste: All other nonstormwater discharges (including, but not limited to, concrete truck washout, vehicle washing or maintenance spills) produced during the construction activity shall not be discharged to any surface waters.
d. External Washing Of Equipment And Vehicles: All external washing activities shall be limited to a designated area of the site. All runoff must be contained and wastes from external washing activities must be disposed of properly. No engine degreasing shall be allowed on the site.
e. Wastes Generated By Concrete And Other Washout Operations: All liquid and solid wastes generated by any concrete or other washout operations must be contained in a leakproof facility or impermeable liner. Concrete waste must not come into contact with the ground. Concrete waste must be disposed of properly and in compliance with applicable MPCA regulations.
12. Drain Inlet Protection: All storm drain inlets shall be protected during construction until control measures are in place with a straw bale, silt fence or equivalent barrier meeting accepted design criteria, MPCA standards and specifications.
13. Energy Dissipation: Pipe outlets must have temporary or permanent energy dissipation within twenty four (24) hours of connection to a surface water.
14. Tracking: Vehicle tracking BMPs (including, but not limited to: rock pads, mud mats, slash mulch, concrete or steel wash racks, or similar systems) must be installed to minimize track out of sediment from the construction site. If vehicle tracking BMPs are not actively preventing sediment from being tracked into the street, the applicant must utilize street sweeping to contain sediment.
15. Final Stabilization: Final stabilization is not complete until the following criteria are met:
a. All land disturbing activities must be finished and all soils shall be stabilized by a uniform perennial vegetative cover with a density of seventy percent (70%) or greater of its expected final growth density over the entire pervious surface area, or other equivalent means necessary to prevent soil failure under erosive conditions.
b. The permanent stormwater management system is constructed, meets all of the required design parameters and is operating as designed.
c. All temporary synthetic and structural erosion prevention and sediment control BMPs (such as silt fence) have been removed. BMPs designed to decompose on site may be left in place.
d. For residential construction only, individual lots are considered finally stabilized if the structure(s) are finished and temporary erosion protection and down gradient perimeter control has been completed and the residence has been sold to the homeowner.
e. For construction projects on agricultural land the disturbed land has been returned to its preconstruction agricultural use.
1. Notification: The city engineer, chief building official or designated agent shall make inspections as hereinafter required and either shall approve that portion of the work completed or shall notify the permittee wherein the work fails to comply with the erosion and sediment control plan as approved.
2. Procedure: To obtain inspections, the permittee shall notify the city of Rosemount at least two (2) working days before the following:
a. Start of construction.
b. Installation of sediment and erosion measures.
c. Completion of site clearing.
d. Completion of rough grading.
e. Completion of final grading.
f. Close of the construction season.
g. Completion of final landscaping.
h. Removal of erosion control measures.
i. Final project compliance and acceptance closeout.
3. Permittee Inspection: The applicant shall be responsible at all times for the maintenance and proper operation of all erosion prevention and sediment control practices.
a. Inspections: The permittee or his/her agent shall ensure that a trained person will regularly inspect the construction site at least once every seven (7) days until final stabilization, and within twenty four (24) hours of a rainfall event of one-half inch (1/2") or greater in a twenty four (24) hour period.
b. Recordkeeping: All inspection and maintenance activities conducted on the site during construction must be recorded in writing and retained with the erosion and sediment control plan. Records of each inspection and maintenance activity shall include the following:
(1) Date and time of inspection;
(2) Name(s) of persons conducting the inspection;
(3) Findings of inspections, including recommendations for corrective actions;
(4) Corrective actions taken, including the dates, times and the name of the party completing the corrective action;
(5) Date and the amount of rainfall events that are greater than one-half inch (1/2") in a twenty four (24) hour period; and
(6) Documentation of any changes made to the erosion and sediment control plan.
D. Site And BMP Maintenance:
1. Responsibilities: Prior to any construction in the plat, the developer shall provide the city engineer with a schedule for erosion and sediment control inspection and maintenance, including schedules for street cleaning, and street sweeping. All site and BMP maintenance activities must comply with the requirements of the NPDES construction general permit. The applicant shall investigate and comply with the following BMP maintenance requirements:
a. Silt Fence: All silt fences must be repaired, replaced or supplemented when they become nonfunctional or the sediment reaches one-half (1/2) of the height of the fence. Repairs shall be made by the end of the next business day after discovery or as soon as field conditions allow access.
b. Temporary Sediment Basins: Temporary sedimentation basins must be drained and the sediment must be removed when the depth of the sediment collected in the basin reaches one-half (1/2) the storage volume. Drainage and removal must be completed within seventy two (72) hours of discovery or as soon as field conditions allow access.
c. Surface Waters And Conveyance Systems: Surface water, including drainage ditches and conveyance systems, must be inspected for visible signs of sediment being deposited by erosion. The applicant must remove all sediment deposited in surface waters, including drainageways, catch basins, and other drainage systems and must restabilize the areas of exposed soil as a result of sediment removal. The removal and stabilization must take place within seven (7) days of discovery unless legal, regulatory or physical access constraints prevent remediation. In the event of an access constraint, the applicant shall use all reasonable efforts to obtain access. If access is precluded, removal and stabilization must take place within seven (7) calendar days of obtaining access. The applicant is responsible for contacting all local, regional, state and federal authorities and obtaining any required permits prior to conducting any work.
d. Streets And Paved Surfaces: Where vehicle traffic leaves any part of the site, the exit locations must be inspected for visible signs of off site sediment tracking onto paved surfaces. Tracked sediment must be removed from all off site paved surfaces as soon as possible or within twenty four (24) hours of discovery.
e. General Maintenance: The applicant shall be responsible for the operation and maintenance of temporary and permanent water quality management BMPs, as well as erosion prevention and sediment control BMPs for the duration of the construction work on the site. The applicant remains responsible until another party has assumed control over all areas of the site that have not established final stabilization and a notice of termination (NOT) has been submitted to the Minnesota pollution control agency.
f. Off Site Deposition: If sediment escapes the construction site, off site accumulations of sediment must be removed in a manner and at a frequency sufficient to minimize off site impacts.
g. Infiltration Areas: All infiltration areas must be inspected to ensure that no sediment from ongoing construction activities is reaching the infiltration area and these areas are protected from compaction caused by construction equipment driving across the infiltration area.
2. Lapse: If the site development permittee repeatedly fails to meet or maintain sediment and erosion control measures per the approved grading, sediment and erosion control plan, the city may, in its discretion, perform the work or contract to have the work completed and drawn down on the escrow deposit, letter of credit or bond to pay any costs.
a. The city will attempt to notify the developer in advance of any proposed action, but failure of the city to do so will not affect the developer's and city's rights or obligations hereunder.
b. If the developer does not reimburse the city for any cost the city incurred beyond that covered by the deposit, for such work within ten (10) days from the date notice of the amount owed to the city is mailed, the city may draw on the security to reimburse city for such costs. (Ord. 2015-01, 2-17-2015; amd. Ord. 2015-05, 7-7-2015)