Purpose: The regulations of this section are intended to improve water quality and provide a natural, effective form of flood and water pollution control through the integration of vegetated, well designed stormwater filtration swales and other green stormwater facilities into required landscape areas, where topography and hydrologic features allow.
Applicability: The standards for stormwater integration shall apply to all subdivisions, site improvements and ACHD stormwater facilities. ACHD stormwater policy shall supersede city requirements for stormwater facilities, except that facilities counting toward open space requirements must also meet or exceed city requirements.
Stormwater swales incorporated into required landscape areas shall be vegetated with grass or other appropriate plant materials. Such swales shall also be designed to accommodate the required number of trees as per section 11-3B-7 of this article if located in a street buffer or other required landscape area.
A rock sump may be incorporated into a vegetated swale to facilitate drainage. The rock sump inlet may not exceed more than five feet (5') in any horizontal dimension.
Gravel, rock, sand, or cobble stormwater facilities are not permitted on the surface of required landscape areas, unless designed as a dry creek bed or other design feature.
Plant materials shall be a species that are able to withstand the anticipated changes in soil wetness and moisture levels.
Organic mulch shall not be used against drainage catch basins because of potential sediment clogging.
Slopes shall be less than or equal to three to one (3:1) (horizontal:vertical) for accessibility and maintenance.
The stormwater facility shall be designed free draining with no standing water within forty eight (48) hours of the completion of a storm event. (Ord. 16-1717, 1-3-2017)
Excerpt from Stormwater Management Plan
4.6 Post Construction Stormwater Management for New Development and Redevelopment Projects
This section describes activities ACHD conducts or will implement to fulfill Permit requirements for a construction site stormwater runoff control program.
The post construction stormwater management for new development and redevelopment permit requirements are:
Within four years of the effective date of this permit, the permittee must update as necessary and enforce their requirements addressing post construction storm water runoff from new development and redevelopment projects that disturb greater than or equal to one acre (including projects less than one acre that are part of a larger common plan of development or sale) and discharge into the MS4 within the permit area. The program must ensure that controls are enacted that prevent or minimize water quality impacts from newly developed or redeveloped areas.
Within four years from the effective date of this permit, the permittee must implement a regulatory mechanism to the extent allowable under State or local law to address postconstruction runoff from new development and redevelopment projects. If such requirements do not currently exist, development and adoption of a mechanism must be part of the program. The permittee may evaluate existing procedures, policies, and authorities pertaining to activities occurring on its property that may be used to assist in the development of the required regulatory mechanism.
No later than the expiration date of this permit, the permittee must maintain proper long term operation and maintenance of all permanent storm water management controls for newly developed project areas greater than or equal to one acre discharging to its MS4 located within the permit area.
No later than the expiration date of this permit, the permittee must develop and implement a process for pre-construction plan review of permanent storm water management BMPs. The permittee must implement an inspection program to require proper installation and monitor compliance of long term operation and maintenance requirements of such controls.
ACHD intends to meet the post construction stormwater management (PCSM) for new development and redevelopment permit requirements by implementing the flowing activities and associated actions, some of which are currently being implemented.
Ada County Highway District Phase I Stormwater Managment Plan
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