(a) All subdivisions or other land development shall have a storm water management system that is adequately designed and constructed by the subdivider or developer to provide for the proper drainage of surface water of the subdivision or development and the drainage area of which it is a part. The storm water management system shall be adequate to prevent the undue or unplanned retention of storm water on the site and prevent undue or unplanned damage to adjacent property either upstream or downstream of the proposed subdivision or development.
(b) The design of the storm water management system shall be consistent with general and specific concerns and standards of the Comprehensive Development Plan, East Sidney Watershed Report and the drainage control programs of applicable public agencies. Designs shall be based on environmentally sound site planning and engineering techniques.
(c) To the maximum degree possible, drainage from subdivisions shall conform to natural contours of land and not disturb pre-existing drainageways.
(d) Adjacent properties or the drainage area of which the development is a part shall not be unduly burdened with surface water from the subdivision or other land development. Specifically:
(1) There may be no unreasonable impediment of water from higher adjacent properties across the subdivision or land development, causing damage to lower properties. No action shall unreasonably collect and channel storm water onto lower properties. The peak rate of post-development runoff based on the intensity of a ten year design storm shall not exceed the peak rate of pre-development runoff. The City reserves the right to include volumetric controls for runoff from a proposed development in instances where such controls are necessary. For example, if post-development runoff volume from a proposed development exceeds the capacity of a downstream detention cell, the City reserves the right to require the proposed development to reduce post-development runoff through implementation of retention cells or other acceptable storm water management practices, as determined necessary by the Public Services Director, and is to be managed in a manner consistent with State statutes and existing case law regarding such flows.
(e) Design shall use the best available technology to minimize off-site runoff, encourage natural filtration, simulate natural drainage, and minimize discharge of pollutants. Best available technology may include such items as detention cells, retention basins, swales, porous paving, terracing and other similar engineering solutions. Storm water may be detained on a per lot basis, per subdivision basis or in a regional facility that serves the drainage basin.
(f) All storm water management facilities shall be designed by a State licensed engineer. All storm water management plans submitted to the City shall be signed and stamped by the designing engineer.
(g) No surface water shall be channeled into a sanitary sewer system.
(h) Where possible, a subdivision's or land development's drainage system shall coordinate with that of surrounding properties or streets.
(i) All storm water designs shall be reviewed and approved by the Public Services Director. The plat submissions and or development submittals must include Public Works Plans including preliminary drainage computations and demonstrations that the proposed storm water management system meets the requirements of this section.
(j) The location of all storm water management facilities and associated easements shall be clearly labeled on the final plat.
(k) Final engineering design and drainage computations must be approved by the Public Services Director prior to the commencement of any type of development construction or the issuance of any building permits for any lot within the subdivision or other land development.
(l) The subdivider/developer shall provide adequate drainage facilities within the subdivision or other land development to provide for the adequate disposal of subsurface and surface water as determined to be necessary by the Public Services Director, including recommendations from the Planning Commission.
(1) Drainage facilities shall include underground pipe, inlets, catch basins, open drainage ditches, culverts and/or bridges, intersectional drains, drop inlets, headwalls, curb, gutter, bio-cells and similar or related installations.
(2) Storm water shall be conveyed to an approved storm drainage system if available and adequate to accept the runoff from the fully developed subdivision or other land development. "Available" shall mean a system approved by the Public Services Director to serve the proposed subdivision or other land development that is within 300 feet; the subdivider/developer shall construct a storm drainage system and connect with such storm drainage system.
(3) If an approved storm drainage system is available but not of adequate capacity, then provisions must be made for on-site detention to reduce the peak flow out of the subdivision to that which the approved system can accommodate.
(4) If such a storm drainage system is not available, natural drainage channels with easements of adequate width shall be provided, as determined by the Public Services Director, including recommendations from the Planning Commission.
(Ord. 1699. Passed 8-27-13.)