It is the purpose this article to set forth the minimum requirements necessary to provide and maintain a safe, efficient, and effective stormwater management system within the City and to establish the various public and private responsibilities for the provision thereof with the least possible disruption of the natural drainage system and of the environment.
A. It shall be the responsibility of any applicant engaged in the activity of land subdivision, development, or improvement to:
1. Control and manage all drainage from the subdivision resulting from the development including the control and management of any determined, approved increase in runoff or runoff rate.
2. Prepare all drawings, plans specifications, statements, studies, justifications, and other data required by this article in form that permits an orderly and comprehensive review and approval to assure that all assigned responsibilities have, sufficiently and correctly incorporated.
3. Control and manage all stormwater runoff and drainage from points and surfaces within the subdivision.
4. Provide detention or retention facilities or storm sewer, or improved or natural channels, or a combination thereof to provide control and management of increased discharge.
5. Prevent soil dispersal, sedimentation, erosion, or other similar forms of pollution:
a. From any surface of the site into drainage channels provided or created within the development.
b. From the site into drainage channels adjacent to and remote from the site.
6. Prevent any and all drainage interferences, obstructions, or other adverse effects upon drainage into, through, or adjacent to the development from upstream or higher elevation source by the use of temporary or permanent by-pass channels, channel improvements, or other facilities as may be required.
7. Improve or modify all drainage systems and channels lying within or adjacent to the subdivision to a level that meets all requirements of this article.
8. Improve or modify drainage systems downstream from the subdivision to a level that will accommodate all allowable, significant increases in stormwater quantity or rate without adverse effect and in accordance with the requirements of this article.
9. Fully consider and provide natural drainage in the design of drainage systems and classifications applicable to the development.
10. Prepare and submit a professional evaluation of the impacts of proposed development.
11. Maintain all installed drainage facilities in a clean, fully functioning manner, from installation through final acceptance by the City.
12. Prevent any contribution to existing flooding, drainage, erosion, runoff, pollution. Or other stormwater management problems within an area already under a high level of development.
13. Prevent drainage, runoff, flooding, or problems associated with any adverse contribution to any such potential problems.
B. It shall be the responsibility of all owners of property, whether undeveloped, developed, or undergoing development, to:
1. Mow and provide minor maintenance of drainage channels and their slopes for that portion of the channel lying within their property line.
2. Keep clear all drainage channels within the boundaries of their properties in accordance with the requirements of this article.
3. Control all stormwater runoff and drainage from points and surfaces on the property.
4. Prevent any and all drainage interferences, obstructions, blockages, or any other adverse effects upon drainage, into, through, or out of the property.
C. It shall be the responsibility of the City to:
1. Repair and maintain drainage channels and their slopes when located within or upon rights-of-way dedicated to and accepted by the City.
2. Develop and implement standards and specifications required to clearly and accurately interpret the physical requirements of this article.
3. Make such necessary improvements of primary and secondary drainage channels that cannot or will not be improved through private development.
4. Improve and maintain floodway and flood fringe areas that are dedicated and accepted-public areas, rights-of-way, park lands, or public-owned buildings or developments.
5. Improve and maintain all public owned drainage channels or systems outside the flood fringe area.
D. It is the intent of this article that the following principles shall be used in the design of modifications to or the improvement of the stormwater management system.
1. Natural drainage channels and techniques shall be given priority consideration in preparation of drainage system designs and shall be designed or improved as an integral part of the landscape of the area and shall be kept in good repair.
a. The design of any development shall provide for the maximum use of open channels and natural streams for flows and detention or retention storage of volumes and flows in excess of those present prior to development.
b. Drainage channel improvement shall be developed and designed that preserve and protect large trees and other worthy botanical and geological features to the greatest possible extent.
c. Wherever channel improvements are required to accommodate calculated flows in a specified manner, the designs shall provide maximum utilization of turf, sodding, and other natural drainage techniques.
2. Closed, underground drainage conduits shall be employed only when there is no viable alternative to fit site or geographic conditions or to meet the requirements of this article and all specifications and performance standards pertaining thereto.
3. The rate of runoff after development shall not exceed that rate experienced before development.
a. In no case shall the release rate of stormwater runoff from all developments in a drainage area, controlled or uncontrolled, exceed the "safe" storm drainage capacity of the downstream outlet channel(s) or storm drainage system as determined by the City Engineer or other designated representatives by the City Manager.
b. Within already developing or developed areas where "safe" storm drainage capacity of downstream outlet channel(s) or storm drainage system has been exceeded, the developer shall add no increased runoff unless the downstream outlet capacity has been increased to accommodate all flows.
c. Improvements may be required in channels or sewers flowing into, through, or from the subdivision or development, or in channels or sewers located upstream or downstream that are affected by the flow of water from the subdivision; development, or change thereto. The following types of improvements, among others not specifically listed, may be required.
(1) Enlargement or replacement of undersized structures.
(2) Removal of obstructions.
(3) Straightening, widening, and/or deepening of channels.
(4) Construction of erosion and sedimentation facilities.
(5) Construction of closed- or open-paved or natural drains for the purpose of closing gaps or maintaining the continuation of the overall stormwater drainage system.
(6) Detention or retention facilities.
(7) Improvements as otherwise required by this article to assure efficient and safe stormwater management.
d. When subdivision development or property improvements will result in an increased runoff beyond the boundaries of the development or improvement which cannot be accommodated through channel improvements without flooding or potential flooding upstream or downstream, the City through its duly designated representative and/or board shall require the construction of one (1) or more detention or retention facilities on the subdivision or property being improved and/or required detention or retention techniques to be used off site which will result in flows, during construction and thereafter, from the property at a rate and volume no greater than the discharge from the undeveloped site.
4. All those engaged, in land improvements or modifications shall prevent the erosion of soil and movement of sedimentation into, unto, or through streets, gutters, catch basins, culverts, or other drainage channels and shall prevent erosion as a result of flows from streets, gutters, culverts, or other drainage channels.
a. Where it can be demonstrated that there is no alternative to rapid runoff water because of identifiable restrictions, the developer shall be required to provide measures to prevent erosion, damage, flooding, or other adverse effects.
b. The City Engineer or the duly appointed City representative shall require the cleaning, straightening, and/or repair of any natural drainage channel or natural features of other drainage channels when necessary to provide for the free flow of water or to eliminate and/or prevent erosion upstream and downstream.
5. The City Engineer or the duly appointed City representative may approve stormwater runoff into a street or alley provided the developer fully and adequately demonstrates that the street or alley or an improvement thereof will provide drainage in full conformance with all other provisions of this article and which will prevent runoff or overflow onto adjacent or nearby residential property.
E. It is the further intent of this article that the following requirements be met to ensure the least possible disruption to the existing drainage system.
1. Detention and retention, separately, or in combination, shall be considered and incorporated, where possible, in all drainage systems design consistent with safety, convenience, and restrictions place upon stormwater runoff rates and velocities for the developments, property, and drainage channels through or therefrom.
2. The City may require improvements, provision of drainage easements; and for provision of improvements, agreements, and/or easements beyond the boundaries of the subdivision, development, or property improvement to facilitate flow of stormwater from or through the property, to avoid damage from changed runoff conditions, to provide continuous improvement of the overall storm drainage system, and to accommodate all drainage conditions or requirements, where stormwater runoff flows require the logical extension of any street and its associated drainage in order to prevent flooding, ponding, or uncontrolled runoff, the extension shall be provided by the developer.
3. Improvements provided by the developer shall be fully and properly maintained from initial approval of installation(s) through final acceptance of the development improvements by the City. The continuing maintenance of detention or retention facilities shall be assured by the developer in the manner described for other drainage facilities.
4. No action shall be taken in any land improvement by any developer, contractor, or lot owner that will alter or otherwise change designed and installed stormwater management control, nor shall any action be taken on existing property that shall adversely affect stormwater runoff in any manner contrary to the provisions of this article, whether temporary in nature to service, only the construction phase of development, or whether a combination of temporary and permanent serving a dual purpose, the first techniques to be employed in the development of a site shall be the management of stormwater and drainage in manner consistent with the requirements of this article.
F. If any determination based upon the provision of this subsection is felt to be unreasonable or inapplicable, a developer or lot owner may appeal that determination to the board of adjustment. Upon the written request for the appeal which shall include all justifications and reasons for that appeal, the question will be heard at the next available meeting of the board of adjustment. If not satisfied with the decision of the board of adjustment, a developer or, lot owner may appeal the decision of the board of adjustment to district court.
(Ord. No. 02-08, § 3, 5-6-2002)