The purpose of this section is to diminish threats to public health and safety caused by the runoff of excessive stormwater, reduce economic losses to individuals and the city as a whole and protect, conserve and promote the orderly development of land and water resources. The provisions of this article further regulate, guide and control:

(a)   The subdivision, layout, redevelopment and improvement of lands within the city limits;

(b)   The construction of buildings and drainage of the sites on which those structures are located, to include parking and other paved areas;

(c)   The design, construction, reconstruction and maintenance of stormwater drainage facilities and systems.

(Ord. 599, Sec. 1)

(a)   Each developer of land within the city has the responsibility to provide on the developer’s property all approved stormwater runoff management facilities to ensure the adequate drainage and control of stormwater on the developer’s property both during and after construction of such facilities.

(b)   Any person, firm or corporation proposing to construct any stormwater runoff management facility or improvement within the city shall apply to the city for approval of the location, dimensions, design and construction methods and materials of such facility. The application shall be in writing and shall contain such information including maps, plats, diagrams, design data, detailed drawings, specifications and calculations as herein required.

(c)   All stormwater runoff management or detention facilities or improvements constructed within the city shall be in accordance with the minimum design requirements contained in this article.

(d)   By separate resolution, the governing body shall designate an individual to coordinate the administration of the storm drainage management system.

(e)   All exceptions, management practices, maintenance procedures, stormwater management plans, performance standards, improvement guarantees and drainage permits proposed under this article will be reviewed by the planning commission. The planning commission shall recommend approval, approval with conditions, or denial to the governing body. Such recommendation of the planning commission shall be approved, approved with conditions, or denied by the governing body.

(f)   Exceptions to the applicability of the article shall be granted by the city in the following situations:

(1)   Additions to, improvements or repair of existing single-family and duplex dwelling structures.

(2)   New construction of anyone single-family or duplex dwelling unit on a residential lot of one-half acre or less and not part of a larger development.

(3)   On land used for agricultural purposes where no change in grade over that which has existed historically will take place.

(Ord. 599, Sec. 2; Code 2016)

For the purpose of this subsection, the words and terms as used herein are defined as set out in this section. Words used in the present tense include the future, wards in the singular number include the plural, and words in the plural number include the singular; the word building includes the word structure; the word shall or the word must is mandatory; and the term used for includes the meaning designated for or intended for.

(a)   Channel -- A watercourse of perceptible extent which periodically or continuously contains moving water or which forms a connecting link between two bodies of water.

(b)   Detention -- A stormwater management technique of which the primary function is to control the peak rate of surface water runoff by utilizing temporary or permanent storage for subsequent disposal by evapo-transpiration, percolation and/or surface release which may or may not be at a rate which is less than the rate of inflow. This may include, but not be limited to, the use of reservoirs, roof tops, parking areas, holding tanks, in-pipe and in-channel storage.

(c)   Detention Basin -- Any manmade area or structure which serves as a means of temporarily or permanently storing stormwater runoff.

(d)   Development -- Any manmade change to improved or unimproved real property including the construction or reconstruction of buildings or structures; paving, excavation, grading, filling or similar operations; or the filing and recording of a subdivision plat.

(e)   Differential Runoff -- The volume and rate of flow of stormwater runoff discharged from a parcel of land or drainage area during a specific rainfall event which is or will be greater than the volume or rate which pertained prior to the proposed development or redevelopment.

(f)   Drainage Area -- The geographical area contributing stormwater runoff to a point under consideration; e.g., a watershed, tributary area, or catchment area.

(g)   Dry-Bottom Storage --A natural or artificial stormwater storage area which is designed and maintained for temporary containment of stormwater runoff and contains no continuous body of water.

(h)   Hydrography – Flow rate distribution of a stormwater runoff with respect to time at the point under consideration, or of detention basis outflow for a specific rainfall event.

(i)    Stormwater Runoff -- Water resulting from precipitation which is not absorbed by the soil, evaporated into the atmosphere, or entrapped by ground surface depressions and vegetation and which flows over the surface.

(j)    Watercourse - Any stream, creek, brook, branch, depression, reservoir, lake, pond, or drainage way into which stormwater runoff flows.

(k)   Wet-Bottom Storage Basins - A stormwater storage area which is designed and maintained to contain water temporarily and to hold permanently an additional volume of water at a level below the discharge structure of the storage area.

(Ord. 599, Sec. 3)

The following practices may be utilized upon approval of the city:

(a)   Storage. Runoff may be stored in temporary or permanent detention basins, or through rooftop or parking lot ponding, or percolation storage, or by other acceptable means.

(b)   Open Channels. Maximum feasible use shall be made of existing drainage ways, open channels, and drainage swales that are designed and coordinated with the design of building lots and streets.

(c)   Streets and Curbs. Streets, curbs, and gutters shall be an integral part of the stormwater runoff management system. To the maximum extent possible, drainage systems, street layout and grades, lotting patterns and the location of curbs, inlets and site drainage and overflow swales shall be concurrently designed in accordance with the standards set forth in this article.

(d)   Enclosed Conveyance System. Enclosed conveyance systems consisting of inlets, conduits, and manholes may be used to convey stormwater runoff.

(e)   Other. The stormwater runoff management practices enumerated herein shall not constitute an exclusive listing of available management practices. Other generally accepted practices and methods may be utilized where approved by the city,

(Ord. 599, Sec. 4)

(a)   The city shall be responsible for the maintenance of all drainage structures and improved watercourses which are within a public right-of way or are under public ownership. Any person who causes damage to or is responsible for damage to such drainage structures or improved watercourses shall be liable for the cost of repairs to that facility. The repairs shall be made by a private contractor or city employee at the option of the administrator. Recoverable expenses for repair shall be the responsibility of the person causing or responsible for the damage. If the person responsible for the damage refuses to pay the recoverable expenses for repair, such expenses shall be assessed against the real property belonging to the person responsible for the damage to such drainage structure or improved watercourse as provided in this article.

(b)   Stormwater runoff control facilities including open drainage swales, channels, enclosed systems and detention structures on or adjacent to and abutting privately owned property and which are not under public ownership shall be maintained by the owner, occupant or agent in charge of such property. Such maintenance shall include but not be limited to keeping the facilities free and clear of weeds, brush, vegetable growth, debris and any other waste material which might impede or hinder the facilities’ intended use.

(c)   The administrator of the storm drainage management system or the administrator’s assistants, employees, contracting agents or other representatives are hereby expressly authorized to enter upon private property for the purpose of determining whether the stormwater runoff control facilities are properly maintained.

(d)   It shall be unlawful for any person to interfere with or to attempt to prevent the administrator or the administrator’s authorized representatives from entering upon any such lot or piece of ground or from proceeding with proper maintenance of the storm drainage management system. Such interference shall be considered to be a violation of this article.

(e)   If the city determines that the owner, occupant or agent in charge of any lot, piece or parcel of land on which a drainage control structure exists or abuts has failed to properly maintain such facility as previously set forth, the city shall notify the owner, occupant and/or agent in charge of such property of the violation. The notice shall be served by restricted mail, postage prepaid, return receipt requested or by personal service and shall state the violation(s) of this article. The notice shall contain the following:

(1)   The owner, occupant or agent in charge of the property shall have 10 days from the date of the notice to abate the violation(s) of this article

(2)   The owner, occupant and/or agent in charge of the property may request a hearing before the governing body or its designated representative within five days of the receipt of notice;

(3)   If the owner, occupant, and/or the agent do not abate the violation(s) of this article, the city or its authorized agent will abate the violation(s) and assess the recoverable expenses of abatement against the owner, occupant and/or the agent in charge of the property;

(4)   The owner, occupant and/or the agent in charge of the property will be given an opportunity to pay the assessment, and if it is not paid, it will be added to the property tax as a special assessment. If the owner, occupant and/or the agent in charge of the property cannot be served in the above manner, service may be made by publishing one notice in the official city newspaper. If notice is made by publication, the owner, occupant and/or the agent in charge, of the property will be ordered to abate the violation(s) within 10 days from the date of publication.

(f)   Upon expiration of 10 days after receipt or publication or other service of notice, and in the event that the owner, occupant and/or agent in charge of the property shall neglect or fail to comply with the requirements of this article, the administrator or an authorized assistant shall cause the violation(s) of this article to be abated.

(1)   The administrator or an authorized assistant shall give notice to the owner, occupant and/or agent in charge of such property by restricted mail of the recoverable expenses of abatement of the violation(s). The notice shall state that payment of the cost is due and payable within 30 days following receipt of the notice.

(2)   The owner, occupant and/or agent in charge of the property may request a hearing before the governing body or its designated representative within five days of the receipt of notice of the assessment of costs.

(3)   If the recoverable expenses remain unpaid after 30 days following receipt of notice, a record of the recoverable expenses shall be certified to the city clerk who shall cause such recoverable expenses to be assessed against the particular lot or piece of land on which the violation(s) of this article were abated. The city clerk shall certify the assessment to the county clerk at the time other special assessments are certified for spreading on the tax rolls of the county.

(g)   Recoverable expenses are all those expenses that are reasonable and necessary for abatement of violation(s) of this article and include, but are not limited to:

(1)   Disposable materials and supplies acquired, consumed and expended specifically for the purpose of the abatement of the violation(s);

(2)   Any additional compensation payment to employees, consultants and contractors for time and effort devoted to the abatement beyond the usual compensation of city employees normally then on duty;

(3)   Rental or leasing of equipment used specifically for the abatement;

(4)   Other special services specifically required for the abatement; and

(5)   Legal expenses that may be incurred as a result of the abatement.

(h)   When in the opinion of the administrator or an authorized representative any stormwater runoff management or detention facility is in such condition as to constitute an immediate hazard requiring immediate action to protect the public; the administrator or an authorized representative may take down, repair or otherwise make safe the facility without delay. Such action may be taken without prior notice to or hearing for the owner, occupant or agent in charge of the property. The recoverable expenses of any such action shall be assessed against the property as provided in this article.

(Ord. 599, Sec. 5)

No development shall increase the quantity and rates of stormwater emanating from the land areas except in accordance with an approved stormwater management plan as provided in this article. The stormwater management plan shall be prepared by a professional engineer licensed to practice in the State of Kansas. No building permit shall be’ issued prior to the approval of the stormwater management plan by the city.

(Ord. 599, Sec. 6)

A stormwater management plan shall accompany all applications for land development. This stormwater management plan shall contain, but not be limited to, the following information and data:

(a)   A site plan consistent with section 16-209(N) of the city code showing suitable scale and contour interval containing topographical information of the land to be developed and adjoining land whose topography may affect the proposed layout or drainage patterns for the development.

(b)   The location and flowline elevation of existing sanitary and storm sewers, and the location of any existing sewage treatment facilities, which fall within the project limits and within a distance of 500 feet beyond the exterior boundaries of the project.

(c)   Detailed determination of runoff anticipated for the entire project site following development, indicating design volumes and rates of proposed runoff for each portion of the watershed tributary to the storm drainage system, the calculations used to determine the runoff volumes and rates and review of the criteria which has been used by the design engineer.

(d)   A layout of the proposed stormwater management system including the location and size of all drainage structures, storm sewers, channels and channel sections, detention basins, and analyses regarding the effect the improvements will have upon the receiving channel and its 100-year flood elevation.

(e)   The slope, type, size, and flow calculations for all existing and proposed storm sewers and other waterways;

(f)   For detention basins, if any, plot or tabulation of storage volumes with corresponding water surface elevations and the basin outflow rates for those water surface elevations.

(g)   For detention basin, if utilized design hydrographs of inflow and outflow for the differential runoff from the site under proposed development conditions.

(h)   A grading and sediment and erosion control plan for the project site showing existing contours, property lines and nearest bench mark elevation and location, if required by the city.

(i)    A profile and one or more cross-sections of existing and proposed channels or other open drainage facilities, showing existing conditions and the proposed changes thereto, together with the 100-year flood elevations expected from stormwater runoff under the controlled conditions called for by these regulations and the relationship of structures, streets, and other utilities to such channels.

(Ord. 599, Sec. 7)

The stormwater management plan shall be reviewed by the city. If it is determined according to present engineering practice that the proposed development will provide control of stormwater runoff in accordance with the purposes, design criteria and performance standards of this article and will not be detrimental to the public health, safety, and general welfare, the city shall approve the plan or conditionally approve the plan, setting forth the conditions thereof. If approved, a drainage permit for the development shall be granted. If it is determined that the proposed development will not control stormwater runoff in accordance with this article, the city shall disapprove the stormwater management plan. If disapproved, the application and data shall be returned to the applicant for corrective action and resubmittal.

(Ord. 599, Sec. 8)

(a)   The plans and specifications for detention facilities and improvements will be calculated on the basis of:

(1)   The distance of the site from the receiving stream; and

(2)   Whether the additional runoff is likely to create a drainage problem by itself or in conjunction with other existing or expected development downstream.

(b)   Where developments form only a portion of the drainage area, the requirements of providing storage shall be upon the proportion of the area being developed.

(c)   It shall be the developer’s responsibility to detain the difference between the runoff from the site in the developed state using the appropriate runoff coefficient listed in this article and the runoff from the site using a runoff coefficient of 0.20.

(d)   The required volume for stormwater detention shall be calculated on the basis of the stormwater runoff from a 10-year storm frequency rainfall having a duration of 15 minutes. This equates to an intensity of 6.08 inches per hour taken from Douglas County rainfall data.

(e)   The release from the detention facility shall be limited to the rate of runoff from the site using a runoff coefficient of 0.20.

(f)   The rational method as described in this article shall be used as a design criterion.

(g)   The methods of stormwater detention shall be at the discretion of the applicant, subject to final approval by the city. Detention may be underground or on the surface. Methods which are normally acceptable include the following: dry bottom storage basin, wet bottom storage basin, paved area storage and rooftop storage. The ability to retain and maximize the ground water recharge capacity of the area being developed is encouraged. Design of the stormwater runoff control system shall give consideration to providing ground water recharge to compensate for the reduction in the percolation that occurs when the ground surface is paved and roofed. The use of natural gravel deposits for the lower portions of stormwater runoff storage areas, the flattening of drainage slopes and the retention of existing topography are examples of possible recharge methods.

(h)   The construction of the stormwater control system shall be accomplished as part of land development. If the amount of storage capacity can be increased to provide benefit to the city, negotiations for public participation in the cost of development may be feasible.

(i)    Final engineering plans shall show complete details for all items covered in this article and shall be submitted to the city for review and approval prior to the issuance of a building permit.

(j)    Rational Method. The basic formula Q = CIA is the rational method for estimating rainfall runoff when

Q = CIA where:

Q = Rate of runoff in cfs

I = Average rainfall intensity

C = Runoff coefficient

A = Drainage area in acres

(k)   Runoff Coefficients. The following runoff coefficients are guides to determine the runoff from the site. The applicant will be responsible for justifying the runoff coefficient used.

(l)    Composite Runoff Coefficients. If it is desirable to use composite runoff coefficients, the following will be used.

(m)  Alternative methods to calculate rate of runoff, establish runoff coefficients and predict rainfall frequency-duration-intensity relationships may be used if approved by the city as equivalent or superior to the methods used herein.

(Ord. 599, Sec. 9)

(a)   Performance Guarantees. Upon approval of the stormwater management plan, but before the issuance of a drainage permit, the city shall require the applicant to post a performance bond, irrevocable letter of credit, cash escrow, certified check, or other acceptable form of performance security for the amount of the work to be done pursuant to the approved stormwater management plan.

(b)   Maintenance Bonds. A two-year maintenance bond against defects in workmanship will be required by the city for any portion of the stormwater management improvements dedicated to the public.

(Ord. 599, Sec. 10)

Upon approval of the stormwater management plan and acceptance of the applicant’s assurances of performance and maintenance as provided in these regulations, the city shall issue a drainage permit. The permit shall set forth the terms and conditions of the approved stormwater management plan.

(Ord. 599, Sec. 11)

Any person who shall violate any of the provisions of this article or who shall build in violation of any specifications of plans submitted and approved, or any permit issued thereunder, shall, for each and every violation and noncompliance respectively be deemed guilty of a misdemeanor, and upon conviction therefor shall be fined an amount to be set by resolution of the governing body from time to time. Each and every day a violation is permitted to exist shall be deemed a separate offense.

(Ord. 599, Sec. 12; Code 2016)

The performance standards and design criteria set forth herein establish minimum requirements which must be implemented with good engineering practice and workmanship. Use of the requirements contained herein shall not constitute a representation, guarantee or warranty of any kind by the city, or its officers and employees, of the adequacy or safety of any stormwater management structure or use of land. Nor shall the approval of a stormwater management plan and the issuance of a drainage permit imply that land uses permitted will be free from damages caused by stormwater runoff. The degree of protection required by these regulations is considered reasonable for regulatory purposes and is based on historical records, engineering and scientific method of study larger storms may occur or stormwater runoff heights may be increased by manmade or natural causes. These regulations therefore shall not create liability on the part of the city or any office with respect to any legislative or administrative decision lawfully made hereunder.

(Ord. 599, Sec. 13)