A. Purpose And Intent: The purposes and intent of this section are to ensure stormwater runoff is sufficiently managed to avoid dangerous conditions, flooding or property damage and to further minimize erosion from wind and water.
B. Applicability: All developments, not exempted in subsection C, "Exemptions", of this section, proposing to disturb a cumulative total of more than twenty thousand (20,000) square feet of contiguous impervious coverage shall comply with the standards of this section, and meet Montana Department of Environmental Quality Regulations.
C. Exemptions: Development in the Central Business Zoning District (B-3) shall be exempt from this section.
D. Stormwater Runoff And Erosion Control Plan: Any application for a development permit, including a building permit if no other development application is required, not exempted in subsection C, "Exemptions", of this section, shall include a stormwater runoff and erosion control plan. The plan shall contain plans, calculations and techniques that demonstrate compliance with the standards of this section and shall be prepared by a professional engineer licensed in the State of Montana.
E. Standards:
1. Pre-Development Discharge: The post-development runoff rate from the site shall not exceed the pre-development runoff rate. Stormwater retention areas may be required to comply with this standard.
2. Velocities Minimized: Runoff velocities shall be minimized and the receiving drainage ways shall be designed and constructed to accommodate the runoff.
3. Stormwater Detention: On site stormwater facilities shall be designed and constructed to detain a 2-year storm event that is one hour in duration, while meeting subsection E1, "Pre- Development Discharge", of this section.
4. Maintenance: Stormwater facilities shall be continually maintained to ensure on-going compliance with this section.
5. Retention Of Vegetation: Existing natural vegetation shall be maintained as much as practical and disturbed areas that do not receive structures or impervious surfaces shall be revegetated.
6. Disturbed Areas Minimized: The amount of ground area disturbed at any one time shall be minimized as much as practical.
7. Silt Fencing: Silt fencing, hay bales or comparable techniques shall be used to prevent sediment from leaving the site due to erosion during construction and until the site is fully vegetated.
8. Water Quality: Water quality of nearby streams, wetlands or other riparian areas shall be protected by the use of vegetative buffer or other techniques as identified in the Sidney Growth Policy or master plan for a subdivision. (Ord. 567, 3-20-2017)