§ 26-170. General provisions for a stormwater management system.

(a)

Generally. These criteria for the design of stormwater management systems are based on the Standard Specifications and Design Criteria, section 5600, "Storm Drainage Systems" (Kansas City Metropolitan Chapter, American Public Works Association, 2011) and the Urban Drainage Design Manual, "Hydraulic Engineering Circular No. 22" (HEC 22-FHWA-SA-96-078, U.S. Department of Transportation, Federal Highway Administration, 1996) as amended in this article.

(b)

Standards and criteria. This article establishes the standards and criteria, which form the regulatory context for the design and review of storm drainage systems in the city. The design for all such systems shall be accomplished under the direction of a registered professional engineer licensed in the state.

(1)

Purpose and objectives. This article is enacted for the general purpose of promoting the health, safety, and welfare of the citizens of the city by achieving an equitable balance between man's use of the land and the preservation of a safe and beneficial environment. The provisions of this article and its amendments are intended to reduce property damage and to minimize the impact of development on existing stormwater management facilities and affected adjacent properties.

(2)

Applicability. The provisions of this article shall extend to all land within the corporate limits of the city. Any persons, firm, corporation, business, or other government entity proposing to construct improvements or develop land within the city shall submit a drainage study and stormwater management plan to the community development director. The community development director will issue a drainage permit for the construction of the proposed improvements upon review and approval of the study and plan.

(3)

Relationship to other agencies and regulations. This article shall not abrogate the authority or jurisdiction of the city drainage board or any other agencies with legal standing to promulgate regulations pertaining to drainage systems within the city. Such standards shall be considered mutually complimentary to those delineated herein, but in the event of conflicts, the more rigorous criteria shall govern.

a.

Federal Emergency Management Administration; floodplain management. Drainage systems to be constructed within the boundaries of the regulatory 100-year floodplain as shown on the applicable Turkey Creek Flood Insurance Rate Maps (FIRM) shall be designed in accordance with the provisions of article II of this chapter. As provided for in this article, all development permit applications for the construction of improvements within the boundaries will be reviewed and approved by the local floodplain administrator.

b.

United States Army Corps of Engineers 404 permit, Kansas Department of Health and Environment - 401 (water quality) permit. Those seeking to place discharges of dredged or fill material including storm drainage system appurtenances into channels and wetlands, which may convey or contain waters of the United States as defined in section 404 of the Clean Water Act (33 USC 1344) and pertinent implementing regulations (33 CFR 320-330) shall seek a jurisdictional ruling from the United States Army Corps of Engineers, Kansas City District and will obtain any permits required accordingly.

c.

Division of Water Resources, Kansas Department of Agriculture; DWR permit. Permit applications for the construction of any drainage improvements within the city at or downstream of a point in a watershed draining 240 acres or more shall be submitted to the Division of Water Resources, Department of Agriculture in conformance with "Obstructions in Streams" ( 82a-301 — 82a-305a ), "Approval of Levee" ( 24-126 ), or the "Water Projects Environmental Coordination Act" ( 82a-325 — 82a-327 ).

d.

United States Environmental Protection Agency (EPA), Kansas Department of Health and Environment (KDHE); National Pollution Discharge Elimination System (NPDES) permit. A Notice of Intent (NOI) for stormwater discharge associated with construction activity must be submitted to KDHE for any drainage or other improvements associated with construction activities which will disturb one or more acres of land. If certain conditions are met, activities disturbing only one to five acres of land may qualify for a waiver from the NPDES permitting requirements.

(4)

Design methodology. In general the methods and procedures described in the Urban Drainage Design Manual, "Hydraulic Engineering Circular No. 22" and section 5600 of the APWA Standard Specifications and Design Criteria as modified or amended in this article, shall be used for storm drainage design in the city. However, any computational method or computer program based on fundamental hydrologic and hydraulic principles and currently accepted engineering practice may be used in design. Methods and procedures, which deviate from those of HEC 22 or those described in this article shall be reviewed and approved by the city prior to their use.

(5)

Disclaimer of liability.

a.

Performance standards and design criteria. The hydrological and hydraulics criteria set forth in this article are minimum design standards based on the current state of the art as propounded by local, regional and national engineering authorities and agencies. Their intention is not to eliminate the possibility of storm-related damage occurring, but rather to manage the risk associated with the probability of such damage occurring. Their implementation must be accomplished under the direction of a registered professional engineer using sound engineering judgment and practices, who will assume full professional responsibility for his work. The city, its officers, and employees offer no guarantee or warranty with respect to the design criteria and assume no liability for their implementation by others.

b.

Drainage permit. City review and approval of the drainage study and stormwater management plan are for conformance with these criteria only and are not intended as an endorsement or a quality assurance/control check of the design. The city, its officers and employees assume no liability with respect to the approval of the drainage study and stormwater management plan or any lawfully made related legislative or administrative decision.

(6)

Definitions. The following words, terms and phrases, when used in this section, shall have the meanings ascribed to them in this subsection, except where the context clearly indicates a different meaning:

Bank line means the line of intersection (above the design hydraulic grade line) of the side slope of an open channel and the adjacent ground.

Community development director means the municipal official authorized by the city council to review and approve the drainage study and stormwater management plan, and to issue the drainage permit.

Controlled area means that part of the tributary area for which a detention facility is designed to control peak discharge rates.

Detention storage means the volume occupied by water above the level of the spillway crest or invert during operation of a stormwater detention facility.

Developer means any person, partnership, association, corporation, public agency, or governmental unit proposing to or engaged in development as defined below; except the widening, resurfacing, or other improvement to existing public streets, alleys, and sidewalks.

Development means any activity, including subdivisions, that alters the surface of the land to create additional impervious surfaces. Such activities include, but are not limited to, pavements, buildings, and structures; except:

(1)

Additions to, improvements, and repairs of existing single-family and duplex dwellings.

(2)

Construction of any buildings, structures, or appurtenant service roads, drives, and walks on a site having previously provided stormwater control as part of a larger unit of development.

(3)

Remodeling, repair, replacement, and improvements to any existing structure or facility and appurtenances that does not cause an increased area of impervious surface on the site in excess of ten percent of that previously existing.

(4)

Improvement on any site having a gross land area of one acre or less, regardless of land use.

(5)

Construction of any one new single-family or duplex dwelling unit, irrespective of the site area on which the same may be situated.

Drainage permit means a permit issued by the community development director authorizing the construction of storm drainage system facilities following the review and approval of a final drainage study and stormwater management plan.

Drainage permit fee means the fee paid in order to obtain a drainage permit authorizing the construction of storm drainage system facilities following review and approval of a drainage study and final stormwater management plan. The fee is a percentage of the total value of the construction work.

Dry detention facilities means stormwater detention facilities, which are normally dry except during wet weather and do not permanently impound water.

Emergency spillway means a device such as an orifice, weir, pipe, or other outlet structure, which supplements the principal spillway and discharges water from a detention facility during storms of lower frequency than its usual design event. Its purpose is to prevent damage to the detention facility, which might result in the sudden release of impounded water.

Floodplain means the Turkey Creek regulatory floodplain as shown in the most recent FEMA food study and flood insurance rate maps.

Freeboard means the difference in elevation between the top of a dam, channel bank, or other structure and the adjacent water surface. A stipulated design freeboard provides a margin of safety against overtopping or flooding.

General area detention facility means a publicly or privately owned detention facility satisfying the detention requirements of two or more developments or land available for future development.

Hydraulics means that branch of science and technology concerned with the mechanics of fluids.

Hydrology means the earth science concerned with the circulation of water through the environment.

Improved channel means any channel constructed by excavation or dredging, or a natural channel altered by grading or lining.

Multiple ownership detention facility means any detention facility designed and constructed to satisfy the detention requirements of two or more legal lots, the owners of which have or will have an equity interest in and obligation to operate and maintain the facility either individually or jointly as a legally constituted association.

Natural channel means a channel or drainage course that has not been physically altered by human activity.

Owner means the owner of record of real property.

Primary or minor system means all public and private drainage facilities designed to collect, convey and store a high to moderate frequency statutory design storm within defined structural boundaries without overflowing.

Principal spillway means a device such as an orifice, pipe, weir, or other outlet structure, which discharges water from a detention facility during its design and more frequent storms.

Return frequency means the statistical average recurrence interval (in years) between rainfalls of equal magnitude and duration.

Secondary or major system means the primary or minor system, its overflow elements and all public and private Turkey Creek tributaries and drainage structures not identified as part of the regulatory floodplain.

Sediment storage means the volume in a detention facility allocated to the storage of sediments.

Single ownership detention facility means any detention facility located on and satisfying the detention requirements of a single legal lot. Such a facility might include, but is not limited to:

(1)

Roofs of buildings or structures also used for other purposes.

(2)

Paved or surfaced areas also used for other purposes.

(3)

Enclosed underground pipes or structures on private property when the surface is used for other purposes.

(4)

Lakes and ponds.

Site means a tract or continuous tracts of land owned or controlled by a developer or owner. Platted subdivisions, industrial or office-commercial parks, and other planned unit developments shall be considered a single site.

Storm drainage system means all of the natural and manmade facilities and appurtenances such as drainage swales, open channels, street gutters, pipes, culverts, bridges, inlets, and detention facilities that collect, convey or store surface runoff.

Stormwater detention facilities means a reservoir or storage structure and its outlet devices the purpose of which is to reduce peak stormwater discharges by attenuating the runoff hydrograph. It functions by temporarily storing runoff and then releasing it at a controlled uniform outflow rate lower than that of the inflow rate.

Tributary area means all land draining to a point of interest, regardless of ownership (also: watershed, drainage basin, catchment, sub-basin, etc.).

Wet detention facility means stormwater detention facilities normally featuring a permanent pool, as well as temporary stormwater storage capacity.

(Code 1967, ch. 7, art. I, § 7-1; Ord. No. 1400, § 1, 3-26-2001; Ord. No. 1689, § 1(7-1), 7-9-2012; Ord. No. 1729, § 3, 1-12-2015 )