Grading, erosion control, and sediment control practices shall be adequate to prevent transportation of sediment from the site to the satisfaction of the City Engineer. Any construction activity disturbing one acre or more of land shall meet additional criteria outlined in chapter 7 of this title. The design shall conform to the most recent version of the Engineering Manual and as specified herein:
A. Clearing And Grading:
1. Clearing and grading of natural resources protection areas, including the Wild and Scenic Recreational River District, Shoreland Overlay District, wetlands or wetland buffers shall not be permitted, except when in compliance with all other provisions of this Code.
2. Clearing techniques that retain natural vegetation and retain natural drainage patterns shall be used to the satisfaction of the City Engineer.
3. Phasing shall be required on all sites disturbing greater than thirty (30) acres, with the size of each phase to be established at plan review and as approved by the City Engineer.
4. Clearing, except that necessary to establish sediment control devices, shall not begin until all sediment control devices have been installed and have been stabilized.
5. Cut and fill slopes shall be no greater than two to one (2:1), except as approved by the City Engineer to meet other community or environmental objectives.
B. Erosion Control:
1. Exposed soil (including stockpiles) must be stabilized according to the following schedule:
Slope | Time (Days Of Inactivity) |
Steeper than 3:1 | 7 |
3:1 to 10:1 | 14 |
Flatter than 10:1 | 21 |
2. If vegetative erosion control methods, such as seeding, have not become established within two (2) weeks, the City Engineer may require that the site be reseeded, or that a nonvegetative option be employed.
3. On steep slopes or in drainageways, special techniques that meet the design criteria outlined in the Engineering Manual shall be used to ensure stabilization.
4. At the close of the construction season, the entire site must be stabilized using a heavy mulch layer or another method that does not require germination to control erosion.
5. Best Management Practices shall be employed to prevent the blowing of dust or sediment from the site.
6. Best Management Practices that divert upland runoff past disturbed slopes shall be employed.
C. Sediment Controls:
1. Sediment controls shall be provided and maintained per the Engineering Manual. All control measures shall be installed prior to commencement of any upstream construction activities.
2. Where possible, detention basins shall be designed in a manner that allows adaptation to provide long term stormwater management. Detention basins must be cleaned after permanent erosion control measures are in place or final stabilization has been established. The design of the detention basins shall be per the Engineering Manual.
3. Adjacent properties shall be protected by the use of a vegetated buffer strip, in combination with perimeter controls.
4. Soil stockpiles must be stabilized or covered at the end of each workday unless a perimeter control is in place.
D. Waterways And Watercourses:
1. When a wet watercourse must be crossed regularly during construction, a temporary stream crossing shall be provided, and an approval obtained from Department of Natural Resources.
2. When in-channel work is conducted, the channel shall be stabilized before, during and after work.
3. All on site stormwater conveyance channels shall be designed according to the criteria outlined in the Engineering Manual.
4. Stabilization adequate to prevent erosion must be provided at the outlets of all pipes and paved channels.
E. Construction Site Access:
1. A temporary access road designed in compliance with the Engineering Manual shall be provided at all sites.
2. Other measures may be required at the discretion of the City Engineer in order to ensure that sediment is not tracked onto public streets by construction vehicles, or washed into storm drains. (Prior Code § 4-4-5)