(a)

Goal. It is the goal of this policy to attempt to hold stormwater runoff rates after development to their historic value as an aid in erosion control and to decrease the probability of downstream flooding.

(b)

Purpose.

(1)

The purpose of this drainage policy is to establish standard principles and practices for the design and construction of surface drainage systems within the city. The design factors, formula, graphs and procedures are intended for use as an engineering guide in the solution of drainage problems involving determination of the quantity, rate of flow, method of collection, storage, conveyance and disposal of stormwater.

(2)

Methods of design other than those indicated herein may be considered where experience clearly indicates they are preferable and they exceed the minimum requirements as listed herein. However, there should be no extensive variations from the practices established herein without the express approval of the city engineer. Runoff calculations must meet or exceed the maximum flow rates using the methods and procedures presented in this article.

(c)

Minimum surface drainage requirements.

(1)

General design criteria.

a.

Drainage facilities shall be designed to transport runoff from the following frequency storms:

1.

25-year storm. Streets, in residential districts.

2.

50-year storm. Streets, bridges and culverts, open improved drainage channels, flood protection works and other facilities in commercial, institutional and other high value districts.

b.

The drainage system shall be designed to carry and/or store the runoff from a 100-year frequency storm. The dedicated drainage easement shall encompass all land lying below the evaluation of the 100-year storm.

c.

Site improvement shall provide for the grading of all building pads to a minimum elevation of one foot above the base flood elevation. In single-family residential, duplex or manufactured home developments, surface water from each dwelling lot will flow directly to a storm sewer, channel sodded swale, or paved street without crossing more than four adjacent lots.

d.

Erosion and sedimentation control facilities with specifications detailing all erosion and sedimentation control measures, which are established and maintained during all periods of development and construction, shall be provided.

e.

No improvements shall be constructed which will increase the frequency of flooding or the depth of inundation of unprotected structures.

(2)

Existing drainage structures. Existing structures within and adjoining a proposed development shall be evaluated in terms of capacity and structural soundness. Those structures found to be inadequate shall be completely removed by the developer and replaced with approved pipe and pipe arch, or a culvert of closed box design. Provisions for carrying or storing the increased flow and protecting property as a result of this flow shall be provided for by the developer.

(3)

Utilities. All utilities located within the floodway shall be designed to prevent infiltration of floodwater and to protect against washouts. Location of the utilities shall not restrict flood flows.

(4)

EPA and state regulations. The owner and his consulting engineer shall provide evidence that the improvement is in compliance with all applicable EPA and state permits and regulations.

(5)

City standards. The current city standard details and requirements shall apply to all improvements.

(d)

Drainage plan preparation.

(1)

Preparations.

a.

Plan and profile shall be drawn on sheets 24 inches by 36 inches to a horizontal scale of one inch equals 20 feet or one inch equals 40 feet and vertical scale of one inch equals two feet or one inch equals four feet (except that scales may vary on special projects, such as culverts and channel cross sections).

b.

Stationing shall proceed upstream with the north arrow pointing to the top of the sheet, or to the left.

c.

Plans for the proposed drainage system shall include property lines, lot and block numbers, dimensions, right-of-way and easement lines, floodplains, street names, paved surfaces (existing or proposed), contract limits, location, size and type of inlets, manholes, culverts, pipes, channels and related structures, outfall details, miscellaneous riprap placement, two-foot contour lines, title block.

d.

Profiles shall indicate the proposed system (size and material) with elevations, flow lines, gradients, left and right bank channel profiles, station numbers, inlets, manholes, ground line and curbline elevations, typical sections, riprap construction, filling details, minimum permissible slab elevations adjacent to 100-year floodplains, open drainage features, pipe crossings, design flow capacities, and title block.

e.

When official floodplain designations and designations of floodways denoting limits of permissible flood flow restricting developments exist, then they shall be shown on all preliminary plans and copies of final plats submitted for approval wherever such plans and plats contain floodplains and/or floodway segments. In any case in which official floodplains are not delineated they shall be determined on the basis of standard corps of engineers HEC 1 and HEC 2 or other methods approved by an engineer, and shall be shown on all preliminary plans and final plats submitted for approval.

(2)

Submittals.

a.

Computations and plans to support all drainage designs shall be submitted to the city engineer for review. The computations and plans shall be in such form as to provide the basis for timely and consistent review and will be made a part of the permanent record for future evaluation. The computations and plans shall be accompanied by the certification of a registered professional engineer licensed to practice in the state. Before final approval, the submitting engineer shall provide an "as built" plan accompanied with a letter of certification stating that the submitted plan complies with all governing ordinances and adopted drainage standards of the city.

b.

Specified drainage parameters for historic, developed or proposed conditions that must be shown prior to approval are as follows:

1.

Drainage area.

2.

Time of concentration (in minutes).

3.

Intensity (in inches/hour) (for specified storm).

4.

Runoff coefficients (C values for rational method, if used).

5.

Design slope and length for all culverts.

6.

Roughness coefficient for all channels and culverts.

7.

Q flow rate (in cfs) for all channels and culverts.

8.

Velocity (in ft/s) corresponding with each calculated Q.

9.

Designation of material types for all channels and culverts.

10.

Specific materials and/or methods for erosion and sedimentation control.

11.

Detention pond volume calculations.

12.

Detention pond depth versus discharge curve.

13.

Detention pond location, elevations and dimensions.

14.

Detention storage calculations with inflow and outflow hydrographs.

(Code 1983, § 12-901; Ord. No. 436-03-04, 3-18-2004)

(a)

General.

(1)

Numerous methods of runoff computation are available on which the design of storm drainage and flood control systems may be based. The rational method will be accepted as adequate for drainage areas up to 500 acres. For larger areas, other methods may be used.

(2)

The methodology developed by the U.S. geological survey titled "Techniques for Estimating Flood Discharges for Oklahoma Streams" will be acceptable as adequate for drainage basins in excess of 500 acres. Other hydrographic models or methods suitable for this are also acceptable. Hydrographic techniques for determining the size of small detention facilities are included under section 44-716.

(3)

The rational method is based on the following assumptions:

a.

The peak rate of runoff at any point is a direct function of the average rainfall intensity during the time of concentration to that point.

b.

The frequency of the peak discharge is the same as the frequency of the average rainfall intensity.

c.

The time of concentration is the time required for the runoff to become established and flow from the most remote part of the drainage area to the point under design.

The latter assumption applies to the part most remote in time, not necessarily in distance. In the rational method, average intensities have no time sequence relation to the actual rainfall pattern during the storm. The intensity-duration curve is not a time sequence.

(b)

Rational method of runoff computation.

(1)

Runoff coefficient C.

a.

It should be noted that the runoff coefficient C is the variable of the rational method, which is least susceptible to precise determination. Its use in the formula implies a fixed ratio for any given drainage area, which in reality is not the case. A reasonable coefficient must be chosen to represent the integrated effects of infiltration, detention storage, evaporation, retention, flow routing, and interception. All of these affect the time distribution and peak rate of runoff.

b.

Recommended ranges for C values are as follows:

BASIN SLOPE

(2)

Rainfall intensity.

a.

Rainfall intensity is the average rainfall rate in inches per hour, which is considered for a particular drainage basin or subbasin and is selected based on design rainfall duration and design frequency of occurrence. The design duration is equal to the time of concentration for the drainage area under consideration. Intensity duration curves for this region are shown on page 8-A of "Techniques for Estimating Flood Discharges for Oklahoma Streams."

b.

The time of concentration used in the rational equation is the critical time of concentration for the point of interest. The critical time of concentration is the time associated with the peak runoff from the watershed to the point of interest. The time of concentration to any point in a storm drainage system is a combination of the "inlet time" and the "time of flow in the conduit." Street flow shall be considered as being in an open paved channel. Manning's equation is acceptable for determining open channel and free water surface flows. An acceptable formula for use in determining inlet time (sheet flow) is:

Time = K ^0.37 /S ^0.2 )

L = Length of flow in feet

S = Average slope in feet/foot

K = Constant for character of surface

Values of K:

An acceptable formula for determining channel flow time is:

Time = K (L ² /S ^0.385 )

Values of K:

The time of flow in a closed conduit is the quotient of the length of the conduit and velocity of low as computed using the hydraulic factors of the conduit. The time required to fill the conduit shall be neglected even though it may represent an appreciable percentage of total time of concentration.

(3)

Drainage area. The size and shape of the watershed must be determined. Drainage areas less than ten acres shall be determined through the use of planimetric topographic maps, supplemented by field surveys where topographic data has changed or where the contour interval is too great to distinguish the direction of flows. A drainage area shall be provided for each project. The drainage area contributing to the system being designed and drainage subarea contributing to each inlet point shall be identified. The outlines of the drainage divides must follow actual lines rather than artificial land divisions.

(Code 1983, § 12-902; Ord. No. 436-03-04, 3-18-2004)

(a)

General. The location of inlets and permissible flow of water in the streets should be rated to the extent and frequency of interference to traffic and the likelihood of flood damage to surrounding property. Interference to traffic is regulated by design limits of the spread of water into traffic lanes, especially in regard to collector streets and arterial.

(b)

Design criteria.

(1)

Flow in gutters on straight or parabolic crown pavements may be determined by using Manning's formula for channel flow.

(2)

Minimum gutter slope on residential streets shall not be less than 0.004 ft/ft (0.4 percent). Maximum gutter slope should not be more than 0.08 ft/ft (8.0 percent). In a gutter which has a radius of 100 feet or less, the design flow depth shall not exceed 70 percent of the curb height.

(3)

No lowering of the standard height of street crown or splitting of curb heights shall be allowed for the purpose of hydraulic design unless approved by the city engineer. In no case will it be allowed on collector streets or thoroughfares.

(4)

All street sections shall have a positive crown except alleys.

(5)

Residential streets: The flow depth at the gutters shall not exceed nine inches for a 100-year storm or six inches for the 25-year storm. The use of a cul-de-sac or dead end street as the terminal point of residential street flow shall not be allowed for drainage areas exceeding five acres. A minimum of 70 percent of the flow in a residential street shall be removed to a storm sewer or drainage system prior to reaching the point of curvature of a cul-de-sac or the end of the street for drainage areas exceeding five acres in size.

(6)

Flow in any street shall not exceed 20 acres.

(Code 1983, § 12-903; Ord. No. 436-03-04, 3-18-2004)

(a)

General.

(1)

All storm sewers shall be designed by the application of the Manning or Kutter's equations either directly or through appropriate charts or nomographs. In the preparation of hydraulic designs, investigations shall be made of all existing structures and their performance on the waterway in question. Sewer sizing based on storm frequency shall be as set forth in section 44-710(c).

(2)

In addition, runoff from storms exceeding the design storm up to the 100-year storm should be anticipated and disposed of with minimum damages to surrounding property and the sewer must be accessible for maintenance.

(3)

Drainage areas between lots shall be improved with pipes and paved swales. The pipe shall carry the 50-year flow and the paved swale above the pipe shall carry the difference between the 25- and 50-year flows.

(4)

The 100-year flow shall be confined to the easement.

(b)

Materials of construction.

(1)

Reinforced concrete pipe shall conform to the requirements of ASTM C76. Unless otherwise specified, all pipe shall be Class III for 24 inch and smaller and Class II for 27-inch and larger in accordance with ASTM C76, Wall B. If a closed box design is used in lieu of pipe, the design shall conform to the state department of transportation RCB standards in all improved areas or to be improved areas.

(2)

Plain corrugated metal pipe conforming to the requirements of federal specification WW-P-405 shall not be placed under paved public streets unless approved by the city engineer.

(c)

Design criteria.

(1)

Pipes which are a part of the storm sewer system shall have a minimum diameter of 18 inches.

(2)

Enclosed storm drains will be designed for open channel flow to satisfy as well as possible the requirements for unsteady and nonuniform flow. Sealed joints are required for any pipe that can operate under head.

(3)

The slope shall be such to maintain a minimum velocity of 2.5 fps flowing full.

(4)

Flows may be computed by either the Kutter or Manning equation. Remember the Kutter and Manning equations are used for pipes and conduits of all shapes flowing either full or partly full. The graphs commonly available for their solution usually are compiled for pressure conduit flow only. See subsection (c)(2) of this section.

(5)

Roughness coefficient n for storm sewers:

DESIGN COEFFICIENT

(6)

General rules to be observed:

a.

Pipe size and slope selected so that flow will not decrease at inlet, bends or other changes in geometry.

b.

Do not discharge a larger pipe into a smaller one.

c.

At change in pipe size match top of pipes.

d.

A one-foot freeboard shall be maintained below the proposed finish grade through the storm sewer system. The submittal of energy calculations shall be required on any reach of a system which exceeds 500 linear feet; on the total system that exceeds 1,500 linear feet; on a reach of a system which has an elevation change exceeding ten feet.

e.

Design capacity of the conduit shall not exceed the conduit capacity at critical slope. An acceptable critical slope formula is:

S = 111 n ² /D ¹ /3

S = critical slope C

n = Manning's n

D = circular pipe diameter feet

(7)

Manholes shall be located at intervals not to exceed 350 feet for pipe sizes 42 inches or less. Above 42-inch manholes shall be located as determined by the city engineer. Manholes shall be located at conduit junctions, changes of grade, and changes of alignment.

(8)

Manholes, junction boxes or inlets shall be used at all pipe connections and/or changes in pipe size.

(9)

Minor energy head losses at structures shall be disregarded. Major losses shall be taken into account if they significantly affect the sewer performance.

(10)

The use of one material to extend a sewer constructed of a different material shall not be allowed except at manholes, junction boxes or inlets.

(11)

Degree of curvature shall be as per manufacturer's recommendations.

(12)

All storm sewer outlets shall have erosion protection provided by headwalls, flared end sections, curtain walls, etc., as required by accepted engineering practices and approved by the city engineer.

(d)

Inlet system.

(1)

Inlet design and location in street sections must be compatible with the allowable spread of water on the street section as established is section 44-652. They shall be placed such that they will not interfere with potential driveways.

(2)

Inlet pipe design shall be designed for 25-year storm flow and 50 sump. An overflow flue shall be provided in sump.

(3)

Inlet location shall not interfere with vehicular or pedestrian traffic.

(4)

Whenever possible inlets will intercept water before it reaches a pedestrian crosswalk.

(5)

Inlets shall not be located in a curb radius. Where existing conditions exist that require an inlet in the radius, the radius shall not be less than 38 feet.

(6)

Inlets shall be sized to prevent water from minor streets spilling over and flooding major streets.

(7)

Where a curbed street crosses a bridge, gutter flow shall be intercepted and not allowed to flow into the bridge.

(8)

Inlet capacities on a grade. See city standard detail sheets for acceptable inlet capacities.

(9)

Any inlet grates over which a bicyclist can ride shall be of a design considered bicycle safe.

(Code 1983, § 12-904; Ord. No. 436-03-04, 3-18-2004)

(a)

Natural drainage flow.

(1)

Natural overland flows and open channel and/or swale routings are the preferred alignments of the components of residential drainage systems within the city. These drainage flow techniques assist in the control of stormwater runoff in that the time of concentration of runoff can be extended. Specific reduction in the amount of runoff contributed from each new development in the upper and middle reaches of a drainage basin can reduce the cumulative runoff impact of development thereby contributing to reduction of hazards and/or reduction in the need for costly supplemental systems in the downstream areas. Open channel flows are not necessarily natural systems, although they rely heavily on existing natural features and qualities of the development site.

(2)

Virtually all development increases the amount of stormwater that becomes runoff during and after an event because of the impervious surfaces used in development. Increases in runoff which change the equilibrium of natural areas in the system mandate specific engineering solutions to conserve these natural systems and the predevelopment characteristics of the area. The creation of swales, alteration of small channel capacity or direction, changing of ground cover and the lining of existing channels with other materials, natural or man produced, may be necessary in some parts of the system to achieve the desired objectives.

(b)

Open storm drainage requirements.

(1)

All land adjoining open natural or improved storm drainage channels having an elevation below the 100-year flood elevation of the channel shall be dedicated for the purpose of providing drainage, public park and/or utility easement.

(2)

Any channel improvements shall be approved by the city engineer prior to the commencement of any work thereon.

(3)

Whenever channel improvements are carried out, sodding, back sloping, cribbing and other bank protection shall be designed and constructed to control the situation and erosion for the anticipated conditions and flow resulting from a 50-year frequency rainfall. (See section 44-717.)

(4)

Any channel grading shall be such that water will not gather in pools.

(5)

Drainage easements of satisfactory width to provide working room for construction and access for channel maintenance shall be provided. An open drainage channel shall not be located in a street easement except under the following conditions: Where a paved street surface is least two lanes wide is provided on both sides of a channel so as to provide access; or where acreage or estate type development is proposed with a composite runoff coefficient not exceeding 0.50.

(c)

Design considerations.

(1)

Grade. Channels should be as wide and shallow, and on as flat a grade as hydraulics, topography and economics will allow.

(2)

Hydraulic characteristics. Hydraulic characteristics of channels shall be determined by Kutter's or Manning's equation. The n value(s) used for channels shall be based on the design engineer's experience and judgment in regard to the individual channel characteristics. When submitting calculations, include the source. A composite Manning's n value is included below and may be used if desired.

(3)

Constructed channel geometry.

a.

Whenever a trapezoidal channel is constructed, the minimum bottom width shall be four feet with side slopes of not steeper than 4:1 for sodded sections and a minimum bottom width of three feet with side slopes of not steeper than 1:1 for paved or rock lined sections.

b.

If R is less than 3 × B, additional outside bank height is required and may be determined by the following:

H = Additional height on outside edge of channel (feet)

V = Velocity of flow in channel (fps)

T = Width of flow at water surface (feet)

B = Bottom width of channel (feet)

R = Centerline radius of turn (feet)

g = Acceleration of gravity (32.3 fps)

(4)

Flow velocities in channels. Velocities shall not exceed six fps for sections sodded in Bermuda grass and four fps in sections sodded with brome or blue grass. Velocities in concrete lined or paved sections shall not exceed 15 fps. Whenever improved conduits carrying water discharge into channels either natural or manmade scour protection shall be installed.

(5)

Trickle channels. All channels altered or improved from the natural state will require a paved trickle channel. The paved trickle channel shall be designed in a manner that will minimize erosion or undermining of the improvement. Sodding, soil stabilization, or other methods of erosion control shall be required adjacent to the paved channel.

(6)

Concrete flumes. Concrete flumes in lieu of enclosed pipe shall not be allowed except under the following conditions:

a.

Drainage area shall not exceed five acres.

b.

The structure shall extend to the rear of the adjacent lots and shall lie within the discharge into a park or common area maintained by the city or property owners' association.

c.

A curtain wall shall be provided at the discharge end.

d.

The entrance to the flume shall be as detailed as on city standard detail sheets and based on the Weir equation:

Q = CLH ^3/2

(7)

Exit provisions. Any paved channel more than three feet deep shall have recessed hand/toe pockets in the channel wall spaced vertically on 15 inch centers alternating on a 12-inch width. The pockets (steps) shall be located a minimum of 200 feet apart along the channel and alternate from side to side.

(8)

Water surface. The water surface in the flume shall never be higher than the top of the curb at the entrance to the flume under any flow condition.

(9)

Riprap outlet stabilization. Riprap outlet stabilization shall be constructed at the discharge end of the open drainage channel when the new channel discharges into an undeveloped channel or when the discharge velocities are erosive.

(10)

Fences. Fences shall not be erected below the shoulder of the sodded section, and in no case shall fences be closer than six feet (measured horizontally to the edge of the paved section).

(d)

Computation of composite roughness coefficient for excavated and natural channels.

n = n ₀ +n ₁ +n ₂ +n ₃ +n ₄ )M

Roughness coefficient for lined channels.

Concrete lined - n = 0.013

Rubble riprap - n = 0.033

(Code 1983, § 12-905; Ord. No. 436-03-04, 3-18-2004)

(a)

Materials and size.

(1)

Culverts under private drive approaches may be reinforced concrete pipe or corrugated metal pipe. Size shall be not less than 15 inches or 12-inch by 11-inch corrugated metal pipe arch.

(2)

Culverts under public streets should be reinforced concrete pipe, corrugated metal pipe or closed box design conforming to state department of transportation standards. On corrugated metal pipe, the pipe gauge shall be one grade heavier than shown on the above standard.

(b)

General design requirements.

(1)

Bridges and culverts shall be designed to pass the 50-year storm unless used as an outlet for a detention facility as outlined in section 44-716. Structures under residential streets shall be designed so that water overtopping the structure from a 100-year frequency storm shall not flood the street to a depth greater than 12 inches above the street crown. Structures crossing under arterial or collector streets shall be designed so that waters overtopping the structure from a 100-year frequency storm shall not flood the street to a depth greater than six inches above the street crown. Allowable spread of waters shall not exceed the adjacent floodway.

(2)

Scour protection shall be provided to control downstream erosion.

(3)

Flared end sections with curtain walls may be used in lieu of headwalls. Concrete flared end sections discharging water shall be tied back a minimum of three pipe lengths.

(Code 1983, § 12-906; Ord. No. 436-03-04, 3-18-2004)

(a)

General.

(1)

Retention and detention are two generalized types of storm runoff storage that can be used to control flooding. The term "retention storage" refers to storm runoff collected and stored for a significant period and released or used after the storm runoff has ended. The term "detention storage" consists of reducing the rate of runoff for a short period of time to reduce peak flows by controlling the discharge through an outlet structure and by extending the period of runoff. The purpose of storage of stormwater is to prevent excess runoff from attaining flow rates that exceed the capacities of downstream drainage systems. Unless every available location for stormwater storage is utilized, the management of stormwater runoff by means of storage will not be successful. The ideal design begins the storing of runoff as close as possible to the ridgelines that divide and subdivide the watershed. To extend the time of concentration, runoff storage may be accomplished by the storage of water in reservoirs, parks, side channels, detention ponds either on or off site. Detention facilities shall be provided prior to general earthwork on the site or construction of buildings and parking lots.

(2)

Stormwater detention ponds shall be required where proposed development will be increasing the quantity of stormwater runoff. However, in the event a complete hydrology study by a licensed professional engineer indicates that less flooding damage will occur without stormwater detention and the floodwater elevations do not increase, the detention requirement may be waived. Possible areas where this waiver may apply are at lower areas of drainage basins or areas where the confluence of other streams are creating a rise in water elevation and the timing of an earlier release may be less detrimental to a flooding problem.

(b)

Rainfall storage.

(1)

Rooftop storage will not be permitted.

(2)

Parking lot storage, if used, may employ ponding areas with throttled drains or gravel filled pits with French drains.

(3)

Property line swale ponding and small on site ponds, if used, shall be examined for possible adverse effects on building foundations due to saturation of the subsoil.

(c)

Design considerations for rainfall and runoff storage.

(1)

Sizing of detention facilities shall be by approved methods such as APWA unit hydrograph, SCS method, etc.

(2)

The storage facility shall be permitted to pass the historic runoff less any bypass and shall control the increased runoff due to the development under consideration.

(3)

Release rates shall be based on head over the drain and shall not exceed the historic Q for all frequency storms.

(4)

When a combination of storage facilities is used to control runoff, the system as a whole shall be designed with the capacity to detain the 100-year storm with discharge rates in accordance with subsection (c)(2) of this section.

(5)

All facilities shall be provided with an emergency spillway with scour protection. Earth embankments shall have side slopes not steeper than 3:1. Proper materials are to be specified with the corresponding optimum compaction to provide stability and minimum seepage.

(6)

The storage volume of a detention facility shall be oversized ten percent to allow for sedimentation.

(7)

All detention ponds shall be provided with a paved trickle channel from the inlet to the outlet structure to transmit low flows, except where it is not required by the design as approved by the city engineer.

(8)

Erosion control for storage and/or detention facilities shall be in accordance with section 44-717.

(9)

A paved access road shall be provided to all detention areas for maintenance purposes. For those owned and maintained by the city the access road shall be dedicated as part of the detention area.

(10)

Earth dams and other earth embankments shall be designed by a licensed professional engineer in accordance with the accepted engineering practices to ensure that dam failures will not occur. Design criteria used by the soil conservation service in the selection of materials and construction procedures will be accepted.

(Code 1983, § 12-907; Ord. No. 436-03-04, 3-18-2004)

(a)

Purpose. The purpose of this section is to provide effective management for the control of erosion and sedimentation and to protect water quality and the general health, safety and welfare of the residents of the city.

(b)

General requirements.

(1)

Construction activity on individual tracts or lots shall be conducted if appropriate erosion and sedimentation facilities are installed and maintained throughout the construction period.

(2)

All erosion and sediment control methods necessary for land treatment measures which will effectively minimize and control erosion and sedimentation during and following any proposed construction activity shall be indicated on the final construction and/or building permit plans and be in place prior to building, parking or general earthwork.

(3)

All earth slopes and earth berms new or existing subject to erosion, such as, adjacent to trickle channels, inlet structures, and outlet structures, within any area designated for detention or drainage shall be slab sodded with Bermuda sod or have permanent established growth of vegetation. All vegetation areas shall be fertilized, watered, and in an established growing condition prior to completion or acceptance of any drainage facility.

(4)

Erosion and sediment control on urban areas established by the county conservation district shall be used to determine best practices, define terms and provide basic methodology.

(c)

Design considerations.

(1)

General design principles. Practical combinations of the following principles shall be utilized, as a minimum, in planning measures to be installed for any land disturbing activity:

a.

The land disturbing activity shall conform to existing topography and soil type so as to create the lowest practicable erosion potential.

b.

The disturbed area and the duration of exposure to erosive elements shall be kept to a practicable minimum through construction scheduling and management.

c.

Cut and fill operations should be kept to a minimum.

d.

Disturbed soil shall be stabilized as quickly as practicable.

e.

Natural vegetation shall be retained, protected, and supplemented whenever feasible.

f.

Temporary vegetation or mulching shall be employed to protect exposed critical areas during development.

g.

Permanent vegetation and structural erosion control measures shall be installed as soon as practicable.

(2)

General practice. Soil and water conservation measures include, but are not necessarily restricted to, vegetation, sediment basins, dikes, grade stabilization structures, sediment traps, land grading, diversions, waterways or outlets, and riprap. Vegetative practices shall be applied to control erosion. The practice can be either temporary and/or permanent depending on the site specific needs.

(d)

Erosion and sediment control criteria.

(1)

Long term permanent seeding, sprigging, or planting producing vegetative cover: Bermuda grass, Kentucky 31 tall fescue and weeping lovegrass are some of the types of permanent vegetation that shall be used to control erosion.

(2)

Short term seeding, producing temporary vegetative cover. Small grains like oats, rye and wheat, and sudans and sorghums are the most feasible temporary vegetation and shall be used to control erosion. This practice is effective for areas where soil is left exposed for a period of six to 12 months. The time may be shorter during periods of erosive rainfall.

(3)

Sodding. Covering areas with a turf of perennial sod forming grass.

(4)

Dikes and swales. The design drainage areas for dikes and swales shall not exceed five acres. The minimum dimensions shall be in accordance with the EPA guidelines.

a.

Diversion dike.

b.

Interceptor dike or swale.

c.

Perimeter dike or swale.

(5)

A stabilized construction entrance shall be built in accordance with the adopted standards to reduced or eliminate the tracking or flowing of sediment onto public right-of-way.

(6)

A concrete or stone outlet structure shall be constructed in areas where the entire drainage area to the structure is not stabilized or where there is a need to dispose of runoff at a protected outlet or where concentrated flow for the duration of the period of construction needs to be diffused.

(7)

A grade stabilization structure in the form of a paved chute or flume shall be constructed to prevent erosion, where concentrated flow of surface runoffs is to be conveyed down a slope, in accordance with the adopted standards. The maximum allowable drainage area upstream of such a structure shall not exceed 36 acres.

(8)

A grade stabilization structure in the form of a pipe slope drain shall be constructed to prevent erosion, where concentrated flow of surface runoff is to be conveyed down a slope, in accordance with the adopted standards. The maximum allowable drainage area upstream of such a structure shall not exceed five acres.

(9)

Stormwater detention facilities may be used temporarily as sediment basins. A temporary outlet structure for the stormwater detention facility to work as a sediment pond shall be constructed. At the end of the construction activity, the developer shall make sure that the outlet structure shall meet the design requirements of a stormwater detention facility.

(10)

Hay and sod mulching, as a temporary measure, may be used for embankment stabilization in areas where surface runoff is to be directed down a slope.

(11)

Erosion matting may be used for embankment and slope stabilization where appropriate. The specified use must be recommended by the manufacturer for the proposed material.

(12)

Silt fencing may be used for slope stabilization where appropriate. The specified use must be recommended by the manufacturer for the proposed material.

(Code 1983, § 12-908; Ord. No. 436-03-04, 3-18-2004; Ord. No. Ord. No. 2022-08-18B , § 1, 8-18-2022)

Any person violating the provisions of chapter 44 shall be guilty of an offense punishable by a fine pursuant to the provisions of section 1-8 of this Code.

(Ord. No. 2022-01-21 , § 1, 1-20-2022)