A. Policy: It is the policy of the city to control stormwater at the source and minimize the potential for flooding downstream.
B. Requirements: The following requirements apply:
1. Storm Drainage: Storm drainage leaving a site or subdivision shall not exceed, as much as practicable, the predeveloped quantities and qualities at a maximum rate as follows:
a. Allowable Discharge: The allowable discharge rate from any nonregional basin shall:
(1) Prehard Surfacing Discharge: Not exceed the prehard surfacing discharge for the entire site for the 100-year storm event.
(2) Maximum Discharge Rate: Not exceed the maximum discharge rate set by the city engineer depending on the proposal, the facts and circumstances of the basin, and historical flow, and the drainage within the surrounding area. If no maximum discharge rate is established then the standard discharge rate of 0.1 cubic feet per second per total acre within the development draining to the basin shall be applied.
(3) Controlled Discharge: Controlled discharge may be established through an orifice or adjustable gate as approved by the city engineer.
(4) Flow Concentration: By nature of development, flows are concentrated to one or more locations where historically sheet flow in lower concentrations may have left the site. Attempts shall be made to minimize the runoff concentrated quantity to the flows stated above by use of detention basins, downstream piping to safe areas or other methods as deemed necessary by the city engineer.
2. Water Quality: Best management practices (BMPs) shall be used to the maximum extent practicable to ensure healthy water quality based upon national standards for the same. BMPs are included in the city's stormwater management plan and must be approved by the city engineer.
3. Irrigation Facilities: No stormwater discharge shall be permitted to irrigation ditches and canals, except where such ditch or canal has had historical use only for storm drainage or was an irrigation facility that has been wholly converted to only stormwater use. Irrigation facilities are vested rights under state law and protected against all encroachment, therefore, written permission is required in accordance with Utah Code Annotated section 73-1-15 from the owner or operator of any irrigation ditch or canal before any construction activity that affects an irrigation facility.
4. Parking Lots: No parking lot, including sidewalks and all other impervious surfaces, shall be used for stormwater storage of any kind, above or below surface.
5. Basin Overflows: Attention shall be given to overflow locations and pathways to safe locations downstream as discussed above. Easement shall be obtained and pipes or swales sized to handle the 100-year flow. (Ord. 20-05: Ord. 2012-05)