The following words, terms and phrases, when used in this article, shall have the meanings ascribed to them in this section, except where the context clearly indicates a different meaning:
2-year design storm.
A rainfall event as documented by actual measurement or by recognized design methods that has a 50 percent probability of being equaled or exceeded in any given year.
10-year design storm.
A rainfall event as documented by actual measurement or by recognized design methods that has a ten percent probability of being equaled or exceeded in any given year.
100-year design storm.
A rainfall event as documented by actual measurement or by recognized design methods that has a one percent probability of being equaled or exceeded in any given year.
Channel.
Any natural or artificial stream that conveys water.
Channel improvement.
The improvement of the flow characteristics of a channel by clearing, excavating, realigning, lining or other means in order to increase its capacity and effectiveness. The term “channel improvement” may also be used to refer to channel stabilization.
Common plan of development.
A construction activity that is completed or is planned to be completed in separate stages, separate phases, or in combination with other construction activities.
Construction activity.
Activities subject to TPDES construction permits. These include construction projects resulting in land disturbance of one acre or more. Such activities include but are not limited to clearing and grubbing, grading, excavating, and demolition.
Controlled release structure.
A facility constructed to regulate the volume or peak discharge that can be conveyed through the structure given certain depths of flow, velocity of approach, and structure geometry.
Detention facilities agreement.
A legal document in recordable form and substance satisfactory to the city to be executed by a developer and the city, which describes the duties and responsibilities of a developer to comply with this article and describes and establishes an easement area and access to the facilities involved.
Detention pond.
A basin or pond that is designed to be normally dry and which stores or detains stormwater runoff temporarily after a rainfall event and discharges all of that water over time at a reduced rate from that which would normally have occurred.
Developer.
A person or business entity that owns or intends to develop a tract of land and intends to improve the tract or tracts. Improvements may include, but are not necessarily limited to: clearing, grubbing, filling, mining, excavating, re-grading, constructing buildings, other structures, parking, drives, streets, and utilities and/or otherwise preparing the tract or tracts for division or development.
Final drainage study
refers to those final project plans, analyses, studies, and supporting documents as required to obtain city review and approval and to facilitate construction of improvements and facilities necessary to comply with the requirements of this article.
Final stabilization.
A construction site status where any of the following conditions are met:
(1) 
All soil disturbing activities at the site have been completed and a uniform (i.e., evenly distributed, without large bare areas) perennial vegetative cover with a density of at least 70 percent of the native background vegetative cover for the area has been established on all unpaved areas and areas not covered by permanent structures, or equivalent permanent stabilization measures (such as the use of riprap, gabions, or geotextiles) have been employed.
(2) 
For individual lots in a residential construction site by either:
a. 
The homebuilder completing final stabilization as specified in subsection (1) of this definition; or
b. 
The homebuilder establishing temporary stabilization for an individual lot prior to the time of transfer of the ownership of the home to the buyer and after informing the homeowner of the need for, and benefits of, final stabilization. If temporary stabilization is not feasible, then the homebuilder may fulfill this requirement by retaining perimeter controls or other best management practices, and informing the homeowner of the need for removal of temporary controls and the establishment of final stabilization.
(3) 
For construction activities on land used for agricultural purposes (e.g., pipelines across crop or range land), final stabilization may be accomplished by returning the disturbed land to its pre-construction agricultural use. Areas disturbed that were not previously used for agricultural activities, such as buffer strips immediately adjacent to surface water and areas that are not being returned to their pre-construction agricultural use must meet the final stabilization conditions of subsection (1) of this definition.
(4) 
In arid, semi-arid, and drought-stricken areas only, all soil disturbing activities at the site have been completed and both of the following criteria have been met:
a. 
Temporary erosion control measures (e.g., degradable rolled erosion control product) are selected, designed, and installed along with an appropriate seed base to provide erosion control for at least three years without active maintenance by the operator; and
b. 
The temporary erosion control measures are selected, designed, and installed to achieve 70 percent vegetative coverage within three years.
Finish floor elevation (“FFE”).
The elevation of the lowest enclosed floor area of a structure as further defined by the National Flood Insurance Program regulations promulgated by the Federal Emergency Management Agency (“FEMA”).
Fully developed watershed conditions.
Hat level of development anticipated when all of the land within a watershed is developed to the maximum extent allowable, typically determined by comparing existing development with projected uses of vacant land and nonconforming properties based upon the latest city’s zoning or land use plan, whichever is more intense.
Gross aggregate area.
The area of the development under consideration plus the area of any contiguous land, owned or controlled by the developing entity.
Hydrograph.
A graphical representation of the flow rate (or discharge) of water over time, consequently, the area under the hydrograph curve describes a volume of water. Several methods are available to construct hydrographs.
Maximum extent practicable or MEP.
What is available and capable of being done after taking into consideration cost, existing technology and logistics in light of overall project purposes (40 CFR 230.10(a)(2)).
Municipal separate storm sewer system or MS4.
A conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, manmade channels, or storm drains) that are:
(1) 
Owned or operated by the federal government, state, municipality, township, county, district, or other public body (created by or pursuant to state or federal law) including special districts under state law such as a sewer district, flood control district or drainage district, or similar entity, or a designated and approved management agency under section 208 of the act that discharges into surface waters of the state;
(2) 
Designed or used for collecting or conveying solely stormwater;
(3) 
Not a combined sewer; and
(4) 
Not a part of a publicly owned treatment works.
National Pollutant Discharge Elimination System (NPDES) stormwater discharge permit.
A permit issued by EPA (or by a state under authority delegated pursuant to 33 USC 1342(b)) that authorizes the discharge of pollutants to waters of the United States, whether the permit is applicable on an individual, group, or general area-wide basis.
Notice of change or NOC.
A written notification to the executive director from a discharger authorized under this permit, providing changes to information that was previously provided to the agency in a notice of intent form.
Notice of intent or NOI.
The notice of intent that is required by the NPDES stormwater multi-sector general permit, the EPA Region 6 NPDES stormwater construction general permit, or any similar general permit to discharge stormwater associated with industrial activity that is issued by the EPA or the TCEQ.
Notice of termination or NOT.
A written submission to the executive director from a discharger authorized under a general permit requesting termination of coverage.
On-site storage facility.
A stormwater storage facility that is designed for the storage of runoff on and for a particular site or development. An on-site storage facility may be a detention pond that is designed to be normally dry and which stores or detains stormwater runoff temporarily and discharges all of that water over time at a reduced rate from that which would normally have occurred, or a retention pond (a wet bottom pond) that is designed to retain a certain amount or level of water, a conservation pool, and a flood storage pool for storing stormwater runoff on a temporary basis for the purpose of reducing the peak discharge from the basin.
Positive and adequate outfall.
The drainage of an area in a manner that will adequately convey and ensure complete removal of all surface water after a rainfall event by means of natural gravity.
Preliminary drainage study.
A preliminary plan with supporting documentation which is prepared to demonstrate that a proposed development can, from a conceptual standpoint, properly address the requirements of this article. The preliminary study is presented to the city’s Department of Public Works engineering division for conditional approval prior to final design and preparation of construction plans.
Retention pond.
A normally wet bottom basin or pond that is designed to retain a certain amount or level of water in a conservation pool above which capacity for an additional flood storage pool is available for storing stormwater runoff and discharges the additional flood storage pool over time at a reduced rate from that which would normally have occurred.
Runoff.
That portion of the precipitation that makes its way toward channels or lakes as surface or subsurface flow. When the term “runoff” is used alone, surface runoff is usually implied.
Sheet flow.
Water, usually stormwater runoff, flowing in a thin layer over the ground surface. The term “sheet flow” is synonymous with overland flow.
Stormwater
refers to water (or runoff) which results from precipitation that is not absorbed by soil or plant material over a defined area.
Stormwater pollution prevention plan or SWP3.
A document which describes the best management practices (BMP) and activities to be implemented by a person or business to identify sources of pollution or contamination at a site and the actions to eliminate or reduce pollutant discharges to stormwater, stormwater conveyance systems, and/or receiving waters to the maximum extent practicable.
Texas Pollutant Discharge Elimination System or TPDES.
The program delegated to the State of Texas by the EPA pursuant to 33 USC 1342(b).
Topographically identifiable watercourse
refers to a watercourse or drainage way that is easily identified by a thin, light blue divided line on a USGS topographic map or that is designated as a conveyance of water on the most recent city topographic map.
TCEQ.
The Texas Commission on Environmental Quality or its successor agency.
Water surface elevation (“WSEL”).
The elevation of the water surface (or the height, in relation to the North American Vertical Datum of 1988) resulting from certain rainfall events and frequencies in a drainage facility.
(2001 Code, sec. 106-951; Ordinance 39-2011, sec. 1, adopted 8/2/11)
It is the purpose and intent of this article to establish policies to govern the planning, design, construction, operation and maintenance of stormwater and erosion control facilities and stormwater practices; to regulate the quantity and quality of stormwater discharges; and to protect public health, welfare and safety by seeking to minimize loss and damage related to stormwater runoff and flooding within the jurisdiction of the city. This article sets forth the minimum requirements necessary to provide and promote a safe, efficient and effective drainage system in keeping with appropriate engineering practices and regulatory requirements and to establish the various public and private responsibilities necessary to achieve that end.
(2001 Code, sec. 106-952; Ordinance 39-2011, sec. 1, adopted 8/2/11)
This article shall apply to all public drainage facilities; to any public or private commercial or multifamily residential development or redevelopment activity comprising a gross aggregate area of one acre or more; and to any single-family residential development comprising a gross aggregate area of two acres or more. The gross aggregate area shall include parcels of common ownership that would be connected were it not for separations by intervening public rights-of-way, alleys or easements. However, with respect to the federally mandated requirements for stormwater discharges from construction activities and post-construction runoff as described in section 106-962, this article shall be applicable to any site of one acre or more in size regardless of use.
(2001 Code, sec. 106-953; Ordinance 39-2011, sec. 1, adopted 8/2/11)
This article seeks to establish degrees of stormwater conveyance, discharge, erosion control, stormwater quality and flooding protection that are considered reasonable for regulatory purposes and that are based on scientific and engineering considerations. Unanticipated circumstances and unforeseen combinations of rainfall events and conditions can and will occur. Consequently, this article shall not be construed to imply that designs, construction, and controls approved and installed pursuant to this article will be free from or will prevent flood damage or loss. Use of or reliance upon this article and the stormwater design manual shall not create liability on the part of the city or the city’s officials, representatives or employees.
(2001 Code, sec. 106-954; Ordinance 39-2011, sec. 1, adopted 8/2/11)
The Department of Public Works, under the direction of the director of public works, shall be responsible for the administration of this article, including but not limited to enacting any procedures, programs, standards, guidelines and criteria necessary to achieve the intent of this article.
(2001 Code, sec. 106-955; Ordinance 39-2011, sec. 1, adopted 8/2/11)
In designing developments, the developer shall comply with the stormwater design manual”(known in this article as the “manual”), promulgated by the city’s Department of Public Works, which shall contain written policies, standards, technical design criteria, procedures, methodology, details and regulations related to determination, design, review, and approval of stormwater facilities as necessary to implement and comply with the provisions of this article. The manual shall be the governing document for all design activities related to compliance with this article. Although the intent of this manual is to establish uniform design practices, it neither replaces the need for sound engineering judgment nor precludes the use of information not presented. Other accepted engineering procedures may be used to conduct hydrologic and hydraulic studies with prior approval of the director of public works.
(2001 Code, sec. 106-956; Ordinance 39-2011, sec. 1, adopted 8/2/11)
It shall be the developer’s responsibility to secure all regulatory permits associated with stormwater runoff and the development of drainage improvements. Such permits shall include, but are not limited to: U.S. Army Corps of Engineers 404 permits, Texas Commission on Environmental Quality (“TCEQ”) section 401 permits; Federal Emergency Management Agency Floodplain Revision permits; U.S. Environmental Protection Agency National Pollutant Discharge Elimination System permits; TCEQ Texas Pollutant Discharge Elimination System permits, and any required city permits. The developer shall also be responsible to provide any necessary project documentation to the city as required to facilitate the city’s meeting its requirements under an existing maintenance agreement with the Corps of Engineers for all drainage work along or entering Holliday Creek. When the city is responsible for the design of a drainage project, the city shall be responsible for all required permits.
(2001 Code, sec. 106-957; Ordinance 39-2011, sec. 1, adopted 8/2/11)
Improvements and facilities constructed as required by and in accordance with this article shall be maintained as required to ensure that the improvements and facilities continue to properly function and perform as designed. All drainage facilities and improvements dedicated and constructed for public use and located within public ownership or easements shall, after acceptance, be maintained by the city. All improvements and facilities constructed on and/or constructed solely for the purpose of providing for compliance with this article for any non-residential, multifamily or single lot residential development activity shall be maintained by the property owner and this requirement for maintenance shall pass with the chain of title of the property. Such private construction and maintenance responsibilities shall be: defined in a written detention facilities agreement in a form satisfactory to the city; executed by the property owner/developer and the city; and recorded in the Wichita County real property records.
(2001 Code, sec. 106-958; Ordinance 39-2011, sec. 1, adopted 8/2/11)
(a) 
Drainage system criteria.
It is the purpose of this section to establish design criteria for various stormwater facilities for the purpose of promoting the health, safety and general welfare of the population by minimizing dangers of flooding to life and property. Storm drainage analysis and design for the city shall take into account fully developed watershed conditions unless another standard is specifically authorized elsewhere in this article. Areas within a designated floodplain shall meet the more stringent FFE requirements of city floodplain development regulations. The developer shall comply with the following drainage system criteria unless otherwise authorized by the director in writing:
Table 1 – Drainage System Criteria
Facility
10-Year Event
100-Year Event
Streets and alleys
Maximum water depth within the street or alley shall not exceed six inches above the lowest point of the pavement section
Maximum water depth shall not exceed the lesser of 18 inches above the lowest point of the pavement section or eight inches above the crown of the roadway. Flows must remain within city right-of-way OR the developer must provide site or lot grading plans demonstrating that a six-inch minimum freeboard is provided between the maximum WSEL and the FFE of adjacent buildings
Enclosed pipe systems
Sized to convey calculated flows from contributing drainage area(s) and/or to convey all flows resulting in excess depths of flow within streets and alleys
Sized to convey calculated flows from contributing drainage area(s) and/or convey all flows resulting in excess depths of flow within streets and alleys. A six-inch minimum freeboard shall be provided between the maximum WSEL and FFE of adjacent buildings
Channels and creek improvements
Convey calculated flows from contributing drainage area(s) and maintain velocity requirements per the stormwater design manual
Convey calculated flows from contributing drainage area(s) with maximum WSEL remaining within easement and maintain velocity requirements per the stormwater design manual. A six-inch minimum freeboard shall be provided between the maximum WSEL and FFE of adjacent buildings
Culverts
Upstream headwater not to exceed top of pavement or curb at the low point of the crossing
WSEL within easement; not to exceed 12 inches above the lowest point of the pavement section at the low point of the crossing; and complying with FEMA regulations. A six-inch minimum freeboard shall be provided between the maximum WSEL and FFE of adjacent buildings
Bridges
Refer to 100-year requirement
Bridges shall pass a 100-year event with a minimum 12-inch freeboard between the calculated 100-year WSEL and the lowest horizontal structural member
Detention or retention ponds
Refer to limitation of development runoff, section 106-960
Refer to limitation of development runoff, section 106-960
Dams and impoundments
Regardless of size and dam height, all dams must meet TCEQ requirements per 30 TAC 299
Regardless of size and dam height, all dams must meet TCEQ requirements per 30 TAC 299
(b) 
Lot-to-lot drainage.
Existing drainage between developed lots shall be the responsibility of the adjoining property owners. New residential subdivision developments shall drain surface runoff from no more than three residential lots across an adjoining residential lot before conveying runoff into a public right-of-way, easement or drainage system. New commercial developments shall not drain surface runoff onto another adjoining lot unless a means of conveyance is provided within a dedicated drainage easement to reach a public right-of-way, easement, natural topographically identifiable watercourse, or manmade drainage system.
(c) 
Positive and adequate outfall.
For all developments, whether constructed in whole or in phases, drainage from all improvements shall be conveyed by means of a positive and adequate outfall to the nearest natural topographically identifiable watercourse or manmade drainage system. Drainage improvements required to achieve positive and adequate outfall shall be designed and included in the site development plans submitted for city engineering approval. On-site drainage easements shall be provided as required for these improvements. The developer and design engineer must consider the impact of drainage flows and discharges onto adjoining landowners. A downstream evaluation may be required to determine if downstream drainage improvements and drainage easements are required.
(d) 
Drainage easements.
The developer shall dedicate drainage easements for all stormwater conveyance systems and improvements constructed pursuant to this article including but not necessarily limited to all inlets, piping, ditches, swales, channels, and detention or retention ponds that are to be dedicated to and accepted by the city and that are not already located within existing city easements or rights-of-way. These easements may be dedicated on a plat of record or provided by separately recorded instrument.
(1) 
Drainage easements shall be a minimum of 15 feet in width and sufficient to include the entire stormwater facility width as designed pursuant to the stormwater design manual plus an additional ten feet on one side for access and maintenance activities. The additional ten feet may be omitted for lined or unlined channels that are easily and directly accessible by city crews with maintenance equipment or with side slopes of less than or equal to 4:1. The additional easement width may also be avoided by providing reinforced concrete access ramps to the channel bottom at 4:1 slopes with a six-foot minimum bottom width and sloped (flared) sidewalls from city rights-of-way at 500 feet maximum spacings along the length of the drainage facility.
(2) 
All drainage easements shall remain open and unobstructed. Prohibited obstructions include but are not limited to fences, buildings, shrubbery, or any other improvement that may be considered to impede the flow of stormwater or that would prevent city access for maintenance. However, drainage easements extending along the long axis between residential lots for small (< 24 inches) drainage pipe systems may be fenced.
(3) 
Without prior written approval of the director of public works, a utility franchisee shall not install utilities in a drainage easement except for essentially perpendicular crossings of underground or overhead utilities.
(e) 
Drainage studies.
Those studies as described in this subsection (e) are considered to be in addition to any specialized studies or applications that are required by FEMA or other governmental agency for a particular project.
(1) 
Generally.
The developer shall submit a drainage study for industrial, commercial, or multifamily residential developments comprising a gross aggregate area of one acre or more. Drainage studies shall be submitted for single-family residential developments comprising a gross aggregate area of two acres or more. If a drainage study was not completed on an area that was previously platted, a final drainage study will be provided before project plans are approved, unless that requirement is waived by the director of public works.
(2) 
Preliminary drainage study.
a. 
Timing.
The developer shall demonstrate to the satisfaction of the city that proper drainage pursuant to this article can be conceptually addressed for a development at the preliminary plat stage. A developer shall schedule a conference with the city engineering division prior to the submission of a preliminary plat and shall then submit a preliminary drainage study which includes a conceptual layout of the proposed storm drainage system, or master drainage plan for the proposed development concurrently with the submission of the preliminary plat. Department of Public Works approval of the preliminary plat shall be contingent upon its review and written acceptance of the preliminary drainage study.
b. 
Qualifications to perform the study.
The preliminary drainage study shall be prepared by a professional engineer licensed in the state with demonstrated knowledge of the study of drainage issues and proficiency with drainage analysis and modeling tools. The preliminary drainage study shall be signed, sealed and dated by the engineer responsible for the preparation of the study.
c. 
Requirements.
The requirements for a preliminary drainage study shall be as established in the stormwater design manual.
(3) 
Final drainage study.
a. 
Timing.
The developer shall demonstrate to the satisfaction of the city that drainage analysis and design pursuant to this article are properly addressed for a development at the final plat stage. The developer shall submit a final drainage study for the proposed development concurrently with the submission of the final plat. The final drainage study shall include all appropriate computation and analysis documentation as required by the stormwater design manual. Final drainage studies of all proposed improvements or land developments shall clearly identify the on-site and off-site drainage system improvements required to satisfy this article and demonstrate the upstream and downstream limits to which the improvements or development comply with the design criteria of this article and the stormwater design manual. The final drainage study shall identify intended phases of development and shall provide that drainage improvements for each phase are sufficient to meet the requirements of this article should any successive phase not be undertaken. Additionally, the final drainage study shall identify and define the stages within a phased development that mandate certain drainage improvements to be completed in order to continue the development sequence. If the developer did not submit a final drainage study for a proposed development or if development conditions have been modified, a final drainage study shall be provided prior to issuance of a construction permit for the development. The city’s Department of Public Works may condition its approval of the final plat or issuance of the construction permit on its review and acceptance of the final drainage study.
b. 
Qualifications to perform the study.
The final drainage study shall be prepared by a professional engineer licensed in the State of Texas with demonstrated knowledge of the study of drainage issues and proficiency with drainage analysis and modeling tools. The preliminary study shall be signed, sealed and dated by the engineer responsible for preparation of the study.
c. 
Requirements.
The requirements for a final drainage study shall be as established in the stormwater design manual.
(f) 
Drainage improvements required for development.
(1) 
Drainage improvements.
All developments shall provide for any new drainage facilities, the improvement of any existing drainage facilities, channel improvements or grading, driveway adjustments, culvert improvements or any other drainage improvement, drainage facility, or work that is necessary to provide for the stormwater drainage requirements specified in the stormwater design manual.
(2) 
Easements.
The developer shall dedicate drainage easements across the site that will accommodate fully developed watershed conditions.
(3) 
Construction required.
The developer shall construct drainage improvements that convey stormwater runoff through the proposed development to positive and adequate outfall locations in accordance with the design criteria in the ordinance from which this article derives and the stormwater design manual. The developer is only required to construct that portion of the drainage system across the site that will convey existing off-site flows and the flows from the proposed site development. Upsizing or phasing of the construction of the drainage systems to accommodate fully developed watershed conditions shall be coordinated with the city. Funding for increased sizing of these facilities may be funded by the city at its discretion subject to funding availability.
(2001 Code, sec. 106-959; Ordinance 39-2011, sec. 1, adopted 8/2/11)
(a) 
Generally.
This article shall establish policies necessary to limit and restrict the increase in runoff from development activities and/or to provide adequate downstream drainage facilities and conveyances to minimize the effects of runoff and downstream flooding from development. The intent of this section is to focus design attention on the stormwater impact of development on the entire watershed rather than on a single, discrete site. Further standards, technical design criteria, procedures, methodology, details and regulations to limit runoff from development are included in the stormwater design manual.
(b) 
Runoff release rate.
The controlled release rate of stormwater runoff from development or redevelopment activities shall not exceed predevelopment conditions unless downstream facilities can be demonstrated to be sufficient to convey fully developed 100-year design storm flows from the watershed as provided hereinafter. For the purposes of this article, predevelopment conditions are considered to be those site conditions and characteristics which existed prior to the 1988 adoption of the city’s initial detention ordinance and which can be clearly identified on the 1986 aerial photography archived by the city engineering division. In certain circumstances where downstream drainage facilities are insufficient to carry the concentrated point flows from a development’s on-site storage facilities, downstream channel improvements shall be required or special outflow structures to provide sheet flow release shall also be constructed to mitigate downstream impact.
(c) 
Options.
The following options are available to analyze, account for, and reduce the impact of runoff from development on the drainage systems of the city. Engineering analyses for the option chosen for a development shall be performed as required by this article and in accordance with the stormwater design manual.
(1) 
On-site storage with controlled release.
A developer may limit or reduce stormwater discharge rates from the proposed development to predevelopment conditions as defined herein by providing on-site storage facilities with an appropriately designed, controlled release structure. Design of such on-site facilities shall be designed and submitted in accordance with the stormwater design manual and shall provide for 100-year design storm storage plus a minimum freeboard of six inches above the maximum calculated water surface elevation and a controlled release structure that provides for proper storage and release rates at the two-year, ten-year and 100-year design storm predevelopment rates. An on-site storage and discharge reduction plan shall be prepared by a competent professional engineer licensed by the state and shall be submitted to the city engineering division for its review and approval. Construction and maintenance responsibilities for these facilities on single lot residential, multifamily residential or nonresidential developments shall be defined in a written detention facilities agreement form satisfactory to the city, executed by the property owner/developer and the city, and recorded in the county real property records. This agreement shall grant the city a non-exclusive easement on and access to the area containing the discharge reduction improvements. For multiple lot single-family residential developments, a deed to the city in a form satisfactory to the city shall be granted conveying the property on which the on-site storage facilities are located, and an acceptable easement shall be granted to the city as required to provide access to the area on which these facilities are constructed.
(2) 
Downstream impact assessment.
A downstream impact assessment as described in the stormwater design manual may be performed to document that existing downstream drainage facilities to which the proposed development is to be connected are already sufficient to transport the fully developed 100-year design storm flows, to protect downstream properties from increased flooding, to protect downstream channels from increased erosion potential due to upstream development, and to protect public health and safety. The downstream assessment shall extend from each outfall of the proposed development to a stormwater facility identified by existing plans, FEMA modeling, or other computer models previously prepared and acceptable to the city as having fully-developed flow capacity and shall follow the guidelines of the stormwater design manual as approved on a site-by-site basis by the director of public works. Runoff computations shall be based upon fully developed watershed conditions in accordance with the city’s latest land use projections and may include areas outside of the city limits and ETJ. The assessment shall be performed and submitted in accordance with the stormwater design manual. The results of the downstream assessment may indicate that the developer has several options as follows to address compliance with this article. If none of these options are available or acceptable to the developer, then on-site storage with controlled release shall be required.
a. 
No impact.
In those instances where the downstream impact assessment demonstrates to the satisfaction of the director of public works that the proposed development causes no downstream increases in discharge or base flood elevations due to the timing of the hydrographs or that the existing downstream drainage system can convey the fully developed flows from the project without exceeding the requirements of this article or the stormwater design manual, then no drainage improvements or on-site storage facilities will be required.
b. 
Downstream improvements.
When a downstream impact assessment indicates that downstream facilities do not meet the requirements of this article and the stormwater design manual, the developer may provide for the proper design and construction of downstream drainage improvements rather than construct on-site storage facilities to properly mitigate the effects of additional runoff. Alternatively, where a downstream drainage improvement project has already been identified and analyzed by the city, with the permission of the director of public works, a developer may participate in the project cost of such downstream improvements to satisfy the requirements of this section. Financial participation may include a portion or all of the city drainage project cost and/or the cost of drainage easement acquisition for the city’s benefit. The amount of financial participation by the developer shall be determined using an acceptable engineer’s opinion of the probable construction cost necessary to meet the ordinance requirements for on-site storage and release, plus engineering design fees, and cost of payment, performance and maintenance bonds.
c. 
Participation in regional detention.
The developer may identify or participate in a regional storage facility designed for the fully developed watershed conditions for an area of common development. Such a facility shall be designed pursuant to the stormwater design manual and shall be subject to a predetermined facilities agreement in form and substance satisfactory to the city.
(2001 Code, sec. 106-960; Ordinance 39-2011, sec. 1, adopted 8/2/11)
(a) 
Variance.
A person or entity (an “applicant”) may request a deviation or variance from the provisions of this article; however, there is no guarantee that such requests will be granted. Requests shall be made in writing to the director of public works, shall include all accompanying data, calculations and documentation necessary for city engineering staff to properly analyze the request, and will not be permitted unless the following criteria are addressed to the satisfaction of the director of public works:
(1) 
The requested variance will not adversely affect conditions either upstream or downstream of the subject property;
(2) 
The requested variance will not conflict with any other projects or plans adopted by the city, state, or federal agencies or cause increased flood heights, threats to public safety, additional expenditures of public funds, impairment of the public interest, or conflict with existing local, state or federal laws or regulations;
(3) 
The requested variance would not confer upon the applicant any special privilege not available to others subject to the ordinance; and
(4) 
Not granting the variance would result in exceptional hardship because of circumstances unique to the particular property, the cost of ordinance compliance not being considered a hardship.
(b) 
Waiver for de minimis stormwater discharge impact.
Certain development projects may be subject to this article as a result of their gross aggregate area; however, the proposed site improvements will result in negligible or very minimal stormwater discharge. In these circumstances, the developer shall have two options to request a waiver of the requirements of this article:
(1) 
The developer may request that a stormwater discharge reduction waiver request be prepared and submitted in writing to the city engineering division by a professional engineer licensed in the state. Such a waiver request shall include specific project and site information along with actual engineering calculations to document the request; or
(2) 
The developer may schedule, in advance, an appointment with an individual designated by the director of public works within the city engineering division to apply for a waiver of this article in person. The applicant shall provide a site plan to scale which indicates the location and size of existing and proposed improvements and major property features along with a copy of the final plat or survey delineating the property boundaries for the proposed development.
For either of the options set forth in subsection (b)(1) and (2) of this section, the city engineering division will take the request presented under advisement and will notify the developer or his consultant in writing as to the city’s decision concerning the waiver request. If the waiver request is denied, the developer must address the requirements of this article by use of another option as provided herein.
(2001 Code, sec. 106-961; Ordinance 39-2011, sec. 1, adopted 8/2/11)
This section applies to all construction sites located within the city limits or otherwise subject to the regulatory authority of the City of Wichita Falls that have discharges from construction site activities disturbing one acre or more, or which are part of a plan of common development that will disturb one acre or more.
(1) 
Submittal of NOI, small construction site notice, and SWP3.
A copy of the notice of intent (NOI) and/or the small construction site notice, and stormwater pollution prevention plan (SWP3) shall be submitted to the Department of Public Works for review in accordance with NPDES or TPDES permit requirements and this article at least ten business days prior to the anticipated start of construction activities. Should the SWP3 review process exceed ten business days, construction activities may commence under the submitted SWP3. Once the plan review is complete, any necessary changes will be made to the SWP3 at the project site. If relevant information provided in the NOI or SWP3 changes, the operator must submit a notice of change (NOC) in accordance with the requirements of the TPDES construction general permit and update the SWP3. A copy of the NOC shall be provided to the Department of Public Works within 14 days of change.
(2) 
Review and modification of the SWP3.
a. 
The Department of Public Works retains the authority to request for review any document or plans, including but not limited to a SWP3, spill prevention control plans, hazardous material plans, and waste management documentation from a regulated construction site that the director of public works or designee reasonably believes may affect stormwater discharges to the MS4.
b. 
The director of public works or designee may require an operator of a regulated facility or construction site to modify its SWP3 if the SWP3 does not comply with the requirements of NPDES or TPDES permit to discharge stormwater associated with the construction activity.
c. 
The deficiencies in a SWP3 will be communicated in writing and will provide to the operator a reasonable amount of time, not to exceed 30 days, to make necessary changes in the SWP3.
(3) 
Review and modifications of best management practices (BMP).
a. 
Any person engaged in activities or operation, or owning facilities or property, which will or may result in pollutants entering the MS4 shall implement BMP’s to the maximum extent practicable to prevent and reduce such pollutants. The owner or operator of a regulated facility or construction site shall provide reasonable protections from accidental discharge of prohibited materials or other wastes into the MS4. Practices implemented to prevent accidental discharge of prohibited materials or other wastes shall be provided and maintained at the owner or operator’s expense.
b. 
The city will maintain a list of approved BMP’s as part of the city engineering standards which are accessible on the city’s website. The Department of Public Works may request a demonstration of the effectiveness of implemented BMP’s.
c. 
The Department of Public Works may require an operator of a regulated facility or construction site to modify its BMP’s if the BMP’s do not provide effective protection from accidental discharge of prohibited materials or other wastes from entering into the MS4.
d. 
The deficiencies in facilities or construction site’s BMP’s will be communicated in writing and the operator will be provided a reasonable amount of time, not to exceed 60 days, to make the necessary changes in the BMP’s.
(4) 
Access to construction sites.
a. 
The intent of the facility or construction site inspections shall be to determine compliance with the conditions of the city’s MS4 TPDES permit, any applicable NPDES or TPDES general permits and this article. The facility and construction site owners and operators shall allow the Department of Public Works ready access to applicable sections of public and private premises for the sole purpose of inspections, surveillance, and monitoring for the presence of illegal discharges to the municipal stormwater drainage system, illicit connections to the municipal stormwater drainage system, and assessment of any portions of a regulated construction site influenced by stormwater runoff that may adversely affect the municipal stormwater drainage system.
b. 
An owner or operator of a facility or construction site shall authorize the director of public works and/or his designee to enter such site at reasonable times during normal business hours to ensure compliance with the provisions of this article. If the director of public works determines that an imminent and substantial danger exists to public health or infrastructure, then the director or his designees may enter the site without notice to the operator. If the owner or operator refuses entry after a request to enter and inspect has been made, the city is hereby empowered to seek assistance from any court of competent jurisdiction in obtaining such entry.
(5) 
Compliance with permit.
a. 
A construction site shall comply with the requirements of the NPDES and TPDES permits to discharge stormwater associated with the construction site activity.
b. 
A person commits an offense if the person operates a construction site in violation of the requirements of the NPDES and/or TPDES permit discharge stormwater associated with the construction site activity.
c. 
Prior to the submittal of a notice of termination (NOT), the operator of the construction site shall first notify the Department of Public Works to request an inspection of the construction site for approval of final stabilization. After final inspection approval, the operator of the construction site shall submit to TCEQ and the Department of Public Works a NOT that includes the information required by the TPDES construction general permit.
d. 
The operator shall retain copies of any SWP3 and all reports required by this article or by the TPDES permit for the site and records of all data used to complete the NOI for a period of at least three years from the date that the site meets the definition of final stabilization.
(6) 
Post-construction stormwater control.
a. 
The purpose of post-construction controls is to protect, maintain and enhance the public health, safety, environment and general welfare by establishing minimum requirements and procedures to control the adverse effects of increased post-construction stormwater runoff and non-point source pollution associated with new development and redevelopment.
1. 
Establishing design and review criteria for the construction, function, and use of structural stormwater Best Management Practices (BMP’s) that may be used to meet the minimum post-development stormwater management standards;
2. 
Encouraging the use of better management and low impact site development practices, such as the use of vegetated conveyances for stormwater and preservation of green space, buffers and other conservation areas to the maximum extent practicable; and
3. 
Establishing provisions for the long-term responsibility for and maintenance of structural and nonstructural stormwater BMP’s to ensure that they continue to function as designed, are maintained appropriately, and pose minimum risk to public safety.
b. 
Regulated post-construction storm-water control.
The requirements of this section shall apply to all developments of the city and redevelopments within the corporate limits or in the extraterritorial jurisdiction that are equal to or greater than one acre, unless one of the exceptions applies to the development or redevelopment as of the effective date of this article.
c. 
Exceptions.
1. 
Redevelopment or expansion that results in no net increase in impervious area.
2. 
Development and redevelopment that decreases predevelopment runoff volumes as defined in section 106-960.
3. 
Any new development or redevelopment project that has or will have permit coverage under the Texas Pollutant Discharge Elimination System Industrial Stormwater Permit issued by the Texas Commission on Environmental Quality (TCEQ).
d. 
Standards for post-construction stormwater control.
All stormwater control measures and stormwater treatment practices (BMP’s) required under this article shall be evaluated by the director according to the policies, criteria, and information, including technical specifications, standards and the specific design criteria for required development or redevelopment. All plans shall be submitted in conjunction with the drainage criteria review process. The director shall determine whether these measures will be adequate to meet the requirements of this article.
(7) 
Administrative enforcement.
a. 
Violations.
It shall be an offense for an owner or operator of a construction site or a third party performing work on a construction site to violate any of the requirements of this article, including, but not limited to, the following:
1. 
Conducting any land disturbing or construction activity equal to or greater than one acre without an approved NOI or small construction site notice and an SWP3 for the location where the violation occurred.
2. 
Failing to implement the SWP3 to include, but not limited to, installing erosion control devices or maintaining erosion control devices throughout the duration of land disturbing activities, in compliance with the approved SWP3 and BMP’s for the location where the violation occurred.
3. 
Failing to remove off-site sedimentation that is a direct result of land disturbing activities where such off-site sedimentation results from the failure to implement or maintain erosion control devices as specified in an approved SWP3 for the location where the violation occurred.
4. 
Allowing sediment-laden water to flow from a site without being treated through an erosion control device.
5. 
Failing to repair damage to existing erosion control devices, including replacement of existing grass or sod or established final stabilization.
b. 
Notice of violation.
Written notice of violation (NOV) shall be given to the responsible party or site operator/owner as identified in the SWP3 for a site. The NOV shall identify the nature of the alleged violation, the action required to obtain compliance with the approved SWP3, and the time to comply.
c. 
Stop work order.
If the director of public works, or designee, determines that compliance subsequent to the NOV is not being attained, that a construction site is operating in a dangerous or unsafe manner, or that conditions exist at a construction site that may lead to an illicit discharge, upon written notice of an issuance of a stop work order, such work or conditions shall be immediately terminated or remedied. Written notice shall be provided to the owner, operator, and responsible party of the construction site and shall state the conditions under which work may be resumed. However, where an emergency exists which may result in discharge of hazardous materials or other discharges which pose an immediate injury and harm to property, natural resources, wildlife, or habitat written notice shall be delivered as soon as practical.
d. 
If the violation has not been corrected within seven days after the notice of violation or, in the event of a valid appeal, within seven days of the decision of the director upholding the decision of the Department of Public Works, then representatives of the Department of Public Works may enter upon the subject private property and are authorized to take any and all measures necessary to abate the violation and/or restore the property. It shall be unlawful for any person, owner, agent or person in possession of any premises to refuse to allow the government agency or designated contractor to enter upon the premises for the purposes set forth above.
(8) 
Nuisance, abatement, and lien.
a. 
Failure of a property owner or facility operator to comply with a notice of violation issued pursuant to this article is deemed to be furtherance of:
1. 
An unwholesome situation;
2. 
A condition that may produce disease;
3. 
The presence of impure or unwholesome matter;
4. 
Objectionable, unsightly, and unsanitary matter; and
5. 
A public nuisance.
b. 
If the owner of property in the municipality does not comply with a municipal ordinance or requirement under this article within seven days of notice of a violation, the Department of Public Works may:
1. 
Do the work or make the improvements required; and
2. 
Pay for the work done or improvements made and charge the expenses to the owner of the property.
c. 
In performing or contracting for the aforementioned work or improvements, the department must comply with the procedures established in Texas Health and Safety Code sec. 342.006, as amended. After following such procedures, the department may assess the expenses of such work against the real estate on which the work is done or improvements are made in accordance with Texas Health and Safety Code sec. 342.007, as amended.
(9) 
Penalty and injunction.
a. 
Violation of a provision of this article is declared to be a violation of an ordinance involving health and safety. Accordingly, it shall be punishable by a fine in an amount not to exceed $2,000.00 per violation and as provided by section 1-14.
b. 
If a person has violated or continues to violate the provisions of this article, the city attorney may petition for a preliminary or permanent injunction restraining the person from activities which would create further violations of this article or compelling the person to perform abatement or remediation of the violation.
(2001 Code, sec. 106-962; Ordinance 39-2011, sec. 1, adopted 8/2/11)