9-4-1-10: STORM DRAINAGE; FLOOD CONTROLS 1 :

   A.   Adequate Storm Drainage System: An adequate storm drainage system to accommodate storm water runoff from the public rights of way shall be required in all subdivisions. The requirements for each particular subdivision shall be established by the Ada County highway district and/or the Idaho transportation department, and construction shall follow the specifications and procedures established by said Ada County highway district or Idaho transportation department.

   B.   Interceptor Ditches: Interceptor ditches shall be established above all cut/fill slopes, and the intercepted water conveyed to a stable channel or natural drainageway with adequate capacity.

   C.   Curb, Gutter And Pavement Design: Curb, gutter and pavement design shall be such that water on roadways is prevented from flowing off the roadway.

   D.   Natural Drainageway Treatment: Natural drainageways shall be riprapped or otherwise stabilized below drainage and culvert discharge points for a distance sufficient to convey the discharge without channel erosion.

   E.   Runoff From Impervious Cover: Runoff from areas of concentrated impervious cover (for example, roofs, driveways and roads) shall be collected and transported to a natural drainageway with sufficient capacity to accept the discharge without undue erosion.

   F.   Deposit Of Waste Material Prohibited: Waste material from construction, including soil and other solid materials, shall not be deposited within the 100-year floodplain.

   G.   Drainageways Or Hydraulic Structures In Major Waterways: Drainageways or hydraulic structures in major waterways (defined as draining a basin area of 10 acres or more) shall be designed for the 100-year flood or to accommodate the runoff projected in the soil conservation service hydrology guide for residential development of the Boise front, whichever is greater. In minor waterways (defined as draining a basin area of less than 10 acres), such structures shall be designed for the 50-year flood or to accommodate the runoff projected in the soil conservation service hydrology guide for residential development of the Boise front, whichever is greater.

   H.   Storm Drainage Retention Facilities: On site retention or partial on site retention of storm drainage from new developments is required in any case where, due to development activity, such drainage would be increased either in peak flow rate or in total quantity from that previously discharged from the land or property being developed. Complete retention is required in all cases except those where: 1) runoff flows directly, without crossing intervening property, into an existing drain ditch or other drainage facility that is operated and maintained by a drainage receiver, and 2) such drainage receiver agrees, as evidenced by valid and binding public document, to receive a certain definite quantity of storm drainage from the development. Retention on site of any drainage not so accepted by a drainage receiver or of any drainage in excess of the quantity accepted by a drainage receiver is a duty of the current property owner at any time.

Retention or partial retention facilities shall be provided as an essential part of such development. Design and construction of such retention facilities shall conform to standards, entitled "Design Standards For Storm Drainage Retention Facilities", adopted by resolution of the city council, and which standards may, from time to time, be amended by subsequent resolution of the council. All facilities shall be maintained on an ongoing basis in order to perform as designed. Should any of the provisions of the supplemental standards conflict with the standards set forth herein, the higher standard shall apply.

   I.   Sediment Catchment Ponds: Sediment catchment ponds shall be constructed and maintained downstream from each development, unless sediment retention facilities are otherwise provided. Any facility used shall provide for the removal of surface debris and contaminants, as well as sediment retention.

   J.   Completion And Operation Deadline: The overall drainage system shall be completed and made operational at the earliest possible time during construction.

   K.   Alterations Of Major Drainageways: Alterations of major drainageways shall be prohibited except for approved road crossings and drainage structures.

   L.   Natural Or Improved Open Channel Drainageways: Natural or improved open channel drainageways shall be preserved or provided for in major waterways; except, that at road crossings, conduits may be permitted. Minor waterways shall be permitted to be enclosed in conduits.

   M.   Reservation Of Right To Require: The city reserves the right to require installation of hydrologic measuring devices in drainageways within any development at public expense.

   N.   Drainage System Plans: Drainage system plans shall show how lots will be graded so that all runoff runs either over the curb, or to a drainage easement, and that no runoff shall cross any lot line onto another lot except within a drainage easement. (Ord. 566, 5-15-2007)

 

Notes

1	1. See also title 10 of this code.