(a) Roadway Culverts.
(1) General specifications. The size and shape of the culvert should be such that it will carry a predetermined design peak discharge without the depth of water at the entrance or the velocity at the outlet exceeding allowable limits.
(2) Design procedure. The culvert design procedure recommended for use is Hydraulic Design Series No. 5, U.S. Department of Transportation.
(3) Preferred construction. Single span culverts, including concrete box and slab top are preferred. Multiple cell pipe culverts, when they are the only structures that will meet the physical requirements introduced by rigid headwater controls, will be acceptable
(4) Material. The culvert material shall be concrete, at a minimum diameter of 12 inches. Corrugated steel or metal pipe material will not be allowed.
(5) Drainage area. The drainage area in acres, and the estimated runoff or design discharge in cubic feet per second, and the storm frequency in years shall be shown on the plan for each culvert.
(6) Inlet elevation. The flowline elevation at the culvert inlet should be set deep enough to provide an adequate outlet for future storm sewer improvements upstream.
(7) Design storm frequency (roadway culverts), shall be:
A. 10-year frequency 24-hour storm event for private drives, local and collector streets.
B. 25-year frequency 24-hour storm event for arterial streets.
(8) Design flow. For method of calculation, refer to Table E.
(9) Maximum allowable headwater. The maximum allowable headwater for the design storm shall not exceed or cause any of the following:
A. 18-inches below the top of curb;
B. 12-inches below the edge of pavement;
C. 1.2 times the diameter of culvert; or
D. Diameter or rise plus two feet, in deep ravines.
E. Property Damage – 100-year frequency headwater plus 1-foot, shall not exceed any existing or proposed building first floor elevation.
(10) Manning’s roughness coefficient (n). (See Table F at end of this chapter) Manning’s Roughness Coefficient (n) should be as given in Table F unless an alternate value is approved by the Engineer.
(11) Entrance loss coefficient (Ke). (See Table F) The Entrance Loss Coefficient (Ke) should be as given in Table F based upon the headwall configuration unless an alternative value is approved by the Engineer.
(12) Minimum cover to subgrade. Should be 30 inches from top of pipe to subgrade.
(13) Maximum allowable outlet velocity, shall be:
Turf Channel 5 f.p.s.
Rock Protection 18 f.p.s.
Notes:
A. When the outlet velocity exceeds 18 feet per second, a stilling basin or other such energy dissipation structure must be used.
B. The downstream channel must have the ability to handle the flow satisfactorily.
(14) Structural design criteria. The structural design criteria for culverts shall be the same as that required by the Ohio Department of Transportation (ODOT).
(15) Emergency flood routing. The manner in which flows greater than the design storm will route over or around the culvert, shall be demonstrated to not create a hazard or to cause potential for erosion or personal property damage. Additional scour protection may be required.
(16) End protection should be as follows:
A. 12-inch through 36-inch culverts – full-height headwall.
B. 42-inch through 84-inch culverts – full height headwall with flared wings.
C. Other special type headwalls must be approved before use.
(b) Storm Sewers. The criteria for designing storm sewer systems are listed:
(1) All storm sewer systems shall be designed using Manning's Equation:
Q = 1.49 R 2/3 S ½ A |
n |
and |
Q = AV |
where :
Q = Rate of discharge (c.f.s.)
A = Area of cross-section of flow (sq.ft.)
V = Mean velocity of flow (f.p.s.)
n = Manning’s roughness coefficient
R = A/wp = Hydraulic radius (ft.)
S = Slope of pipe or hydraulic grade line if
surcharged (ft./ft.)
wp = Wetted perimeter (ft.)
(2) Design Storm Frequency: shall be
A. 72" and under - flowing full for 2-year storm
B. Over 72" diameter - flowing full for 10-year storm
(3) Hydraulic Gradient requirement: shall be
A. Based on 5-year storm, shall not exceed window or grate elevation for an inlet or catch basin.
B. Grade line based on tailwater or 0.8 D at outlet (whichever is greater) or other critical points within the system.
(4) Design Flow:
A. Areas under 200 acres use Rational Method Q = CiA.
B. Areas between 200 and 300 acres transition between Rational Method and Technical Release 55.
C. Areas over 300 acres use Technical Release 55.
D. Minimum times of Concentration:
1. Curb inlet - 10 minutes
2. Catch basin - 10 minutes
(5) Runoff Coefficient: Based on Table F, with 0.4 as a minimum.
(6) Manning's “n” Value: All storm sewers shall be based on an “n” of 0.013.
(7) Off-site Area: The sewer must be deep enough to receive the flow from all its sources within the watershed.
(8) Size - The size of the sewer must be adequate for flowing full, based on the design storm (see subsection (b)(2), listed above) with the 5-year storm hydraulic grade line contained to the system
(9) Solids: The gradient of the sewer must be sufficient to avoid deposition of solids.
(10) Material: The storm sewer material for municipally maintained sewers shall be concrete, 12-inch minimum size. 8-inch through 15-inch PVC or polyethylene may be used on privately maintained storm sewers. Other material may be used for special design, only if approved for use by the Administrator. Corrugated metal or steel material will not be allowed.
(11) Manholes: The main conduit, if over 24-inches in diameter, will be required to be separated from all curb and gutter inlets unless a special design is approved by the Municipality’s Engineer. Furthermore, the main conduit will be required to be separated from all deep curb and gutter inlets, which have a depth greater than 6.5 feet from invert to the top-of-casting elevation.
(12) Flow Line: Unless otherwise approved by the Municipality’s Engineer, the flow line of pipes should be set such that the crown of pipes, at junctions, are at the same elevation; if the outlet elevation permits, the crown of the outlet pipe may be lower. The flowline elevations of sewers should be set to avoid using concrete encasement.
(13) Specifications: Methods of construction and trench backfill shall be as per the requirements of the Municipality and the City of Columbus “Construction and Materials Specifications”, latest edition, as approved for use by the Municipality’s Engineer.
(14) Submerged pipe outlets: The submergence of a permanent pool of water above the flowline invert elevation of a storm sewer at the outlet is discouraged and shall not be permitted to a depth greater than the ½ the pipe diameter or a depth of two-feet at the outlet, whichever is less. When submergence is allowed upon approval by the Municipality’s Engineer, special requirements shall include, but may not be limited to:
A. Submergence “zone” shall not extend beneath pavement.
B. Submergence “zone” shall not extend beyond the first manhole.
C. “O-ring” sealed gasketed pipe joints shall be installed along the storm sewer for the full length of the submergence zone.
D. Anti- seepage collars shall be installed in the submergence “zone”.
(15) End protection should be as follows:
A. 12-inch through 36-inch culverts – full-height headwall. If the outlet is not located within a channel bank or within the direct flow path of crossing floodwaters, half-headwalls at the outlet may be used if approved by the Municipality’s Engineer. In no instance will half-headwalls be allowed on non-concrete conduit.
B. 42-inch through 84-inch culverts – full height headwall with flared wings.
C. Other special type headwalls must be approved before use.
(16) Minimum Cover to Subgrade:
A. Desirable, under pavement and within influence of traffic load - 30 inches from top of pipe to subgrade.
B. Desirable, beyond influence of traffic loads (standard strength pipe) – 18-inches from top of pipe to ground surface.
(17) Maximum Cover over pipe:
A. The supporting strength of the conduit, as installed, divided by a suitable factor of safety must equal or exceed the loads imposed upon it by weight of earth plus any superimposed loads.
B. The design procedure recommended for use in structural design of storm sewers is outlined within the Design Manual Concrete Pipe, available from American Concrete Pipe Association, wide trench installation.
(18) Encasement: Class A concrete encasement shall be required within the limits of existing or proposed paved areas inside right of way, in areas influenced by traffic loading, or under paved driveway entrances adjacent to right of way as directed by the Municipality’s Engineer, where the minimum cover during construction or proposed cover over the outside top of the pipe to top of subgrade is 30 inches or less. In addition, all PVC and polyethylene pipe allowed to be installed in the right of way shall be concrete encased per CMS 910. Any concrete encasement of flexible pipe shall extend from structure to structure.
(19) Velocity in Sewer for Design Flow:
A. 3 fps Minimum
B. 15 fps Maximum
C. No minimum for outlets from ponding areas.
(20) Maximum Length Between Access Structures
A. Pipes under 60-inch – 350 feet
B. Pipes 60-inch and over 500 feet
(c) Curb Inlets.
(1) General. The satisfactory removal of surface water from curbed pavement is as important as any other phase of stormwater control. The spread of water on the pavement for the design storm is considered as the best control for pavement drainage. The design procedure recommended for use is Hydraulic Engineering Circular No. 12, available from the Superintendent of Documents, U.S. Government Printing Office. On combined runs of over 600 feet contributing to a sag vertical curve, an additional inlet may be required near the low point, plus or minus two-tenths foot above the inlet at the sag.
(2) Design storm (curb inlets). The following shall be used:
A. Two-year storm frequency.
B. Rational method of calculation.
C. Ten minutes for minimum time of concentration.
D. 0.015 for roughness coefficient for composite roadway paved and gutter section.
E. Maximum width of spread of flow:
Street Width | Width of Spread |
< 26 ft. | 8 ft. |
> 26 ft. | 9 ft. |
(3) Underdrains: Four (4) inch curb drains connections shall be placed 30- inches below the top of the curb on the up-grade side of the inlet. It is desirable to have the storm sewers, draining to the inlets, set such that the elevation of the top of the sewer is not higher than the top of the 4-inch curb drain.
(d) Open Water Courses.
(1) General Requirement: The requirements in this section are applicable to newly constructed open watercourses that are intended to convey flow to stormwater inlets, stormwater control facilities, Tier I/ II streams, lakes, wetlands, or other water bodies during precipitation events. A constructed channel shall be shaped or graded to the required dimensions and established with a suitable lining as necessary to convey stormwater runoff without allowing channel erosion. The following guidance documents may be used for evaluation, planning, and design of constructed open watercourses to supplement the design criteria provided in the Manual:
A. NRCS Ohio Practice Standard 412, Grassed Waterways,
B. NRCS Engineering Field Handbook (EFH) Part 650, Chapter 7 - Grassed Waterways,
C. Agricultural Handbook 667, Stability Design of Grass-lined Open Channels, and
D. Federal Highway Administration, 1988, Design of Roadside Channels with Flexible Linings. Hydraulic Engineering Circular No. 15.
(2) Channel Hydrology Requirements. The hydrologic computation methods specified in Table E, 935.07(e), or as specified by the Municipality’s Engineer, shall be used to design open watercourses in the Municipality. In most cases, open watercourses shall be designed according to the same method used to design other onsite drainage facilities.
(3) Channel Hydraulic Requirements.
A. Design Storm Frequency: Constructed open watercourses shall be designed to convey the 10-year design storm without causing erosion, sedimentation, or overbank flooding within and along the channel. Criteria in 935.07 (c) shall be used if the channel will also serve as a flood routing channel for the 100-year design storm. Open watercourses may also be designed for stormwater quality control. ODOT’s L&D Manual, Drainage Design aids may be used for sizing open conveyances (at various side slopes). A ditch computation sheet shall be used to present open channel calculations.
B. Cross Section Shape: Parabolic and trapezoidal channel shapes (Figure 1) shall be used for open watercourses within development projects. Side slopes shall be 4(H) to 1(V) or milder, with a minimum 2-foot bottom width for trapezoidal channels, unless alternative dimensions are approved by the Municipality due to specific project conditions. Channel cross sections shall be designed such that erosion and sediment deposition is minimized.
C. Design Velocity: An open channel is categorized by its lining. There are three main types of channel linings: vegetated, flexible, and rigid. A vegetative lining, such as grass with mulch and sod and lapped sod, is required where site constraints and flow velocity conditions allow. Flexible linings include rock channel protection and cellular soil retaining mats and are typically less expensive than a rigid lining. The use of flexible linings, however, may require the installation of a filter fabric or other means to protect the underlying soil, prevent washout, and prevent soil piping through the rock when using channel protection. Rigid linings include concrete and rigid block and are usually used where high velocities are unavoidable.
Final design of constructed open channels should be consistent with velocity limitations for the selected channel lining. Maximum velocity values for selected vegetated and non- vegetated lining categories are presented in Table B. The Manning’s Equation shall be used to design an open channel that satisfies the maximum velocity criteria in the previous sections:
Figure 1
 |
V = (1.49/n) R2/3 S½ where: V = average channel velocity (ft/s) n = Manning’s roughness coefficient R = hydraulic radius (ft) = A/P A = cross-sectional area of the channel (ft2) P = wetted perimeter of the channel (ft)
S = slope of the energy grade line (ft/ft) |
Recommended Manning’s “n” values for open channels with vegetated and non-vegetated linings are provided in Table B.
D. Critical Flow: Open channels shall be designed to flow under subcritical flow conditions at all times. A subcritical flow regime is characterized by a Froude Number less than 1:
Table B
Manning’s Roughness Coefficients (n) for Vegetative and Artificial Channels
Channel Lining Category | Roughness Coefficient |
Vegetated Lining: | |
Seeded | 0.03 (for velocity determination only without erosion control matting on all channels) 0.04 (for depth determination along roadside channels only) 0.06 (for depth determination, except along roadside channels) |
Sod | 0.04 (for velocity determination on all channels) 0.04 (for depth determination along roadside channels only) 0.06 (for depth determination, except along roadside channels) |
Flexible Lining: | |
Slope Erosion Protection | 0.04 |
Erosion Control Matting | 0.04 |
Grouted riprap | 0.02 |
Rock channel protection (Typical for Type C/D*) Small channels/ditches Large channels | 0.06 0.04 |
Rigid Lining: | |
Concrete | 0.015 |
Bituminous | 0.015 |
Concrete block mat (tied) | 0.021 |
• Note: Increase roughness coefficient by 15% for Type B RCP.
F = V/(gD)0.5 < 1
where:
F = Froude Number
D = hydraulic depth (ft)
=A/T
A = cross-sectional area of flow (ft2)
T = top width of water surface (ft)
V = flow velocity (ft/sec)
g = acceleration due to gravity = 32.2feet/sec2)
The Stormwater Management Report shall demonstrate that the calculated Froude Number is less than 1 over the anticipated range of flow conditions within the channel.
E. Rock Channel Protection Shear Stress Analysis: Type B, C or D rock channel protection shall be provided in accordance with City of Columbus CMSC Section 601.08. Type B, C or D rock channel protection shall only be placed outside of guardrails, barriers or other unobstructed areas provided outside of the traveled way for vehicles to stop safely or regain control. The actual shear stress (rac) must be less than or equal to the allowable sheer stress (ra) listed in Table C for the rock channel protection type used. The actual shear stress shall be determined for the channel slope and the depth of flow during a 10-year design storm. The following equation is valid for discharges less than 50 cfs and with slopes less than 10%:
Table C
Allowable Shear Stress for
Rock Channel Protection
Type of Rock Channel Protection | rac (lbs/feet2) |
B | 6 |
C | 4 |
D | 2 |
rac = 62.4 * D * S
where:
D = depth of flow (feet)
S = channel slope (feet/feet)
rac = actual shear stress (lbs/feet2)
In extreme site conditions, Type B or C rock channel protection shall be utilized for lining channels with steep grades (slopes 10%- 25%) that carry flow from the end of a cut section down to the lowest elevation on the bottom of the channel. FHWA’s HEC-15 procedures for steep gradient channels shall be used with a safety factor of 1.5. The Division of Sewerage and Drainage shall be consulted if rock channel protection is proposed in instances where the peak flow during the 10-year design storm is greater than or equal to 50 cfs.
F. Outlets: All constructed open watercourses shall have a structurally sound and stable outlet with adequate capacity to prevent ponding or flooding damage. Portions of open water courses affected by back water from Tier I or Tier II streams during dry weather flow conditions shall be provided with a stable outlet.
(Ord. 08-021. Passed 4-14-08.)
(Ord. 08-021. Passed 4-14-08.)
(e) Stream Corridor Protection Zone:
(1) Purpose: The City has determined that establishing a Stream Corridor Protection Zone along streams is necessary to protect structures from damage caused by natural erosion. Unless otherwise exempt, all development and redevelopment projects that include a portion of a Stream Corridor Protection Zone must minimize alterations of the stream, keep new structures out of the Stream Corridor Protection Zone, and maintain a riparian corridor along the stream to minimize streambank erosion and to protect stream habitat.
(2) Requirements: With the exception of roadside ditches (that carry only immediate right-of-way drainage) and approved roadway crossings, no open channels (natural or man-made) will be enclosed within a storm sewer when an area is developed. This policy will apply even when the open watercourse is located on a property line.
A. Exceptions may be granted by the Administrator for streams when the total tributary drainage area is less than 100 acres, however, this shall not absolve the developer from complying with all applicable state and federal regulations.
B. If exceptions are granted on any project, it will be with the requirement that any enclosure will convey flow from the entire tributary drainage area up to the 10-year recurrence interval. A flood routing flow path must be provided through the development site for all storms greater than the 10-year recurrence interval. This flood routing path must be clearly shown on the site development plans. The applicant shall provide stormwater calculations for the proposed enclosure and flood routing to the Municipality for approval. The enclosure shall not raise the flood elevation on upstream property owners.
(3) Stream Identification: Streams covered under this requirement include all streams shown on USGS 7.5 minute Quad maps as solid or dashed blue or purple lines or a surface watercourse (either man-made or natural), with a well-defined bed and bank and channel and that conveys in part or in whole stormwater discharge, and which confines and conducts continuous or periodic flowing water. This definition does not include roadside drainage-ways that convey only immediate right-of-way drainage nor does this definition include channels of a temporary nature formed as part of an approved construction activity and that will be removed at the conclusion of construction.
The Applicant shall identify and label all streams within the project site and/or receiving stormwater discharges from the project site on the master drainage plan (see Section 935.03(b)) submitted as part of the Stormwater Management Report. The Applicant shall provide information that supports the classification of the stream on/adjacent to their site. Such information may include, but not be limited to, copies from USGS Quad sheets, photographs, FEMA maps, or soils maps showing the location of a stream and delineation of upstream tributary area.
If the City determines that the submitted evidence is inconclusive, then they may require a site inspection and input from other sources of information including the City Engineer, the U.S. Army Corps of Engineers, Ohio EPA, ODNR, or the Franklin Soil and Water Conservation District. Final determination regarding whether the watercourse or channel meets the classification of a stream for the purposes of this Chapter shall be at the discretion of the City Administrator or his/her designee.
(4) The Stream Corridor Protection Zone consists of the stream and the riparian area along the stream. Its purpose is to allow the natural, lateral movement of open water courses, provide sufficient area for flood conveyance, protect water quality and prevent structures from being impacted by natural streambank erosion. The Stream Corridor Protection Zone is established through designation of a riparian setback boundary that will be required on all natural streams and manmade open channels, as required under subsection 935.08(e)(2) and designated under subsection 935.08(e)(3). A Stream Corridor Protection Zone is not required for a roadside drainage ditch that carries only immediate adjacent right-of-way drainage. (Ord. 13-012. Passed 5-13-13.)
(5) The Stream Corridor Protection Zone shall be created with the establishment of a riparian setback boundary on each side of the open channel. The total width between the setback boundaries shall be established using the following criteria, whichever is greater:
A. The FEMA designated 100-year floodway, or
B. Using the equation below with a minimum of 50-feet (plus channel width; i.e., 25-ft each side of channel, measured from ordinary high water mark) to a maximum of 250-feet (plus channel width). The zone shall be centered on the stream valley generally located at the point where both zone boundaries intersect equal natural ground elevations on either side of the stream. Where topography is flat the zone shall be centered on centerline of the stream:
Stream Corridor Protection Zone, in feet of width1 = 147(DA)0.38
Where DA = drainage area of the stream in square miles, or
C. 50-feet plus channel width (i.e., 25-ft each side of channel, measured from ordinary high water mark).
1Note: This equation is from Appendix 7 of the “Rainwater and Land Development Manual” by the Ohio Environmental Protection Agency based on regional curve analysis for various watercourses measured in the eastern region of the United States, in studies conducted by Ward (2001), Williams (1986) and Dunne and Leopold (1978).
The Stream Corridor Protection Zone shall consist of three subzones as follows:
Subzone 1 - The Stream Channel: This is the main channel of the stream the banks of which are formed on either side of the stream centerline by the ordinary highwater mark, which is a field determination based feature.
Subzone 2 - The Streamside Buffer: exists on each side of the stream channel and has a cross-sectional width equivalent to 10 % of the Stream Corridor Protection Zone (SCPZ) as determined above, but no less than 25-feet from the ordinary highwater mark. The outer edge of the streamside buffer (on either side of the stream channel) is measured from the ordinary highwater mark.
Subzone 3 - The Outer Buffer: exists on each side of the stream channel. The inner edge is contiguous to the streamside buffer boundary and the outer edge establishes the outer boundary of the Stream Corridor Protection Zone.
Figure 2 displays the typical subzones within the Stream Corridor Protection Zone.
Figure 2
(showing only channel and one side of the SCPZ, for clarity)
10% of SCPZ or
25-ft, whichever
is greater
The position of the outer boundary of the Stream Corridor Protection Zone may be modified at the Administrator's discretion to more accurately reflect local conditions such as to include known areas of environmental sensitivity in close proximity to channels banks, to include sensitive steep slopes adjacent to a channel edge or to exclude high terrain that is adjacent to a stream valley. Any proposed modifications to the Stream Corridor Protection Zone boundary shall be based on technical guidelines that are available in the office of the City Administrator.
The Stream Corridor Protection Zone must be clearly shown on site development plans.
(Ord. 2021-002. Passed 2-8-21.)
(6) Mitigation: Mitigation required for intrusion into the Stream Corridor Protection Zone shall be determined by the horizontal distance the intrusion encroaches into the Stream Corridor Protection Zone. The extent of horizontal encroachment represented by the intrusion into the Streamside Buffer and the Outer Buffer, will be used to determine the required mitigation. Encroachment into these subzones will require mitigation within the same Watershed Assessment Unit (14-digit HUC scale).
A. Mitigation resulting from State or Federal environmental regulations may be adjusted in recognition of these requirements. All mitigation shall, at a minimum include conserved or restored setback zone, and should be designed to maximize the ecological function of the mitigation. Including mitigation at the stream edge along with associated setback areas is one way to maximize ecological function. Mitigation shall be protected in perpetuity by binding conservation easements or environmental covenants. Granting of binding conservation easements or environmental covenants protected in perpetuity for land outside of disturbed area, but within a required riparian setback may in itself, at the discretion of the City Administrator, count towards required mitigation.
B. Unless otherwise approved by the Administrator, the standard form of mitigation for disturbance in the Stream Corridor Protection Zone shall at a minimum include reforestation/replanting activities within the Stream Corridor Protection Zone. The mitigation activity should include removal of invasive species and their replacement with native vegetation, if invasive species are a significant feature to the landscape within the Stream Corridor Protection Zone. Granting of binding conservation easements or environmental covenants protected in perpetuity for land outside of disturbed area and outside AND contiguous to the Stream Corridor Protection Zone, may count toward mitigation.
C. The City Administrator may at his/her discretion, allow for a stream restoration project to serve as the mitigation form, in lieu of or to supplement mitigation of land area by reforestation/replanting, provided that the proposed stream segment is in a degraded condition state (in the opinion of the City) and that it is in the public's best interest to restore this stream's form and ecological function. If this type of mitigation is allowed, it shall be designed by a registered Engineer in the State of Ohio. The design shall be subject to review and approval by the City Administrator or their designee.
D. Mitigation performance standards shall be met to the satisfaction of the City Administrator and based on Technical Guidelines for Mitigation, which are available in the office of the City Administrator.
E. Species selection for reforestation, if made part of a mitigation effort, shall follow the City's list of "Species of Plants and Shrubs recommended for stabilizing flood prone areas", which are included in the City's Technical Guidelines for Mitigation.
F. All mitigation activities and standards and specifications shall be illustrated on a plan that is to be submitted for review and approval to the City Administrator or their designee. The standard for plan content is contained in the Technical Guidelines for Mitigation document that is available in the office of the City Administrator. This document contains a mitigation protocol that outlines City preferences as to nature and extent of mitigation. Moreover, this document contains resources relating to stream restoration.
(7) Construction Requirements: The following conditions shall apply to all Stream Corridor Protection Zones:
A. Except as otherwise provided in this regulation, the Stream Corridor Protection Zone shall be preserved in its natural state.
B. Prior to any soil disturbing activity, the Stream Corridor Protection Zone shall be clearly delineated by the applicant or their designated representative on the site. Such delineation shall also be identified on the Erosion and Sediment Pollution Control Plan (see Chapter 1399) and this delineation shall be maintained throughout soil disturbing activity.
C. No later than the conclusion of construction, the applicant shall permanently delineate the Stream Corridor Protection Zone in an aesthetically harmonious manner, approved by the Administrator, such that the location of the riparian setback boundary defining the Stream Corridor Protection Zone is apparent to the casual observer and that permits access to the zone.
D. Language preventing property owners from constructing facilities and performing activities that are prohibited within the Stream Corridor Protection Zone shall be shown on the plat or separate instrument and reflected on all deeds.
E. Land contained within the Stream Corridor Protection Zone may, at the applicant's option and if approved by City Council, be deeded in fee simple to the City. Alternatively, the land contained within the Stream Corridor Protection Zones shall be preserved via dedicated and binding conservation easement, environmental covenants, or reserve. If the land is deeded in fee simple to the City, then as a condition to acceptance the City may require the developer to provide an access improvement and/or access easement to be dedicated to the City through the subject development site, at the discretion of the City.
F. The applicant shall obtain all necessary permits from the Army Corps of Engineers, Ohio EPA, and other regulatory agencies. The applicant is responsible for all permitting fees.
(8) Post-Construction Requirements:
A. Permitted Uses and Activities. No use or activity permitted under these regulations shall be construed as allowing trespass on privately held lands.
1. Passive Uses. Uses that are passive in character shall be permitted in the Stream Corridor Protection Zone, including, but not limited to, passive recreational uses, as permitted by federal, state and local laws, such as hiking, fishing, picnicking, and similar uses. Construction of paved trails to further such passive recreation uses is also permitted; however, trails that become damaged due to natural erosion shall not be repaired but shall be moved upland or removed altogether.
2. Removal of Damaged or Diseased Trees. Damaged or diseased trees may be removed. Due to the potential for felled logs and branches to damage downstream properties and/or block watercourses or otherwise exacerbate flooding, logs and branches resulting from the removal of damaged or diseased trees that are greater than 6-inches in diameter at the cut end shall be cut into sections no longer than 6-feet, anchored to the shore or removed to a location no closer than 25 feet from channel bank.
3. Vegetation removal on existing levees and dikes.
4. Revegetation and/or Reforestation. Revegetation and/or reforestation of the Stream Corridor Protection Zone using species pursuant to the City's list of "Species of Plants and Shrubs recommended for stabilizing flood prone areas", which is contained in the City's Technical Guideline for Mitigation, available from the Office of the City Administrator. Proper species selection is dependent on soil conditions, available water and amount of sun exposure. Proper species selection will take into account these factors.
5. Public Utilities. Sanitary sewer, storm sewer pipe and/or water lines that are public utilities and public utility transmission lines may be located within the Stream Corridor Protection Zone and disturbances therein necessary to place and/or maintain such utilities are also authorized. The placement, construction and maintenance of such utilities shall minimize disturbance to riparian areas and shall mitigate any necessary disturbances per subsection 935.08
(e)(6) of this chapter. The developer and/or landowner shall secure the appropriate state and federal permits required for installations of this type. Stormwater pipe outfalls may be allowed within the Stream Corridor Protection Zone only where it is shown that elevations do not accommodate their position at a point outside the Stream Corridor Protection Zone; the construction and location of a stormwater pipe outlet within the Stream Corridor Protection Zone must have prior approval of the City Administrator.
6. Private Utilities. New Private utilities such as electric or telecommunication lines being either elevated or running perpendicular to the stream, and gas or cable TV conduit that runs perpendicular to the stream may be located in the Stream Corridor Protection Zone and disturbances therein necessary to place and/or maintain such facilities are authorized, unless prohibited by existing conservation easements or environmental covenants. However, the following related private utility features are not permitted within the Stream Corridor Protection Zone: substations and their appurtenances that support private utilities. The placement, construction and maintenance of such above-described permitted private utilities shall minimize disturbance to riparian areas and shall mitigate any necessary disturbances per subsection 935.08
(e)(6) of this chapter. The developer and/or landowner shall secure the appropriate state and federal permits required for installations of this type.
7. Public Roadways. Public roadways may cross the Stream Corridor Protection Zone and disturbances therein necessary to place and/or maintain the roadways are authorized. The placement, construction and maintenance of the roadway shall minimize disturbance to riparian areas and shall mitigate any necessary disturbances per subsection 935.08
(e)(6) of this chapter. There shall be no more than two roadway encroachments (including crossings) into the Stream Corridor Protection Zone within any proposed development. The developer and/or landowner shall secure the appropriate state and federal permits required for installations of this type. Construction of Public Roadways in FEMA-designated floodplains shall conform with permitting requirements and standards contained in Chapter 1341
"Flood Damage Prevention".
8. Private driveways. Private driveways may be located in the Stream Corridor Protection Zone to access land uses not within the Stream Corridor Protection Zone, provided no feasible alternative that does not involve encroachment is possible in the opinion of the City Administrator, and provided that the driveway width does not exceed 24-feet - unless otherwise approved by the City Administrator - and their placement within the Stream Corridor Protection Zone is minimized. No more than one private drive crossing of a stream within the Stream Corridor Protection Zone will be allowed on an individual tax parcel or if the development of that parcel is part of a larger common plan of development, then no more than two private drive crossings will be allowed for all tax parcels that are a part of that larger common plan of development. Private drive construction shall minimize disturbance to riparian areas and shall mitigate all disturbances per subsection 935.08
(e)(6) of this chapter. The developer and/or landowner shall secure the appropriate state and federal permits required for installations of this type. Construction of private drives in FEMA-designated floodplains shall conform to permitting requirements and standards contained in Chapter 1341
"Flood Damage Prevention". This permitted use shall not include parking lots, which are a prohibited use within the SCPZ.
9. Stormwater Detention Facilities. Detention facilities may be located within the Outer Buffer subzone, provided:
a. The facility is not located in the existing 100-year floodplain area, and
b. Riparian area disturbance will be minimized, and all disturbances shall be mitigated per subsection 935.08(e)(6) of this chapter.
10. Stream restoration and/or stream relocation projects: construction activities associated with these type of activities may be allowed, provided they are appropriately permitted.
11. Floodplain recovery/restoration projects. Projects that recover and otherwise restore the floodplain form and function are permitted provided they are appropriately permitted. Any lands within the Stream Corridor Protection Zone that are modified under this permitted use shall include reforestation of the impacted landscape per subsection 935.08
(e)(6) of this chapter.
12. Emergency Channel Maintenance Activity. Emergency activities intended to restore and/or maintain the function and flood carrying capacity of the main channel area may be permitted, subject to authorization by the City Administrator and, if applicable, by appropriate state and/or federal agenc(ies). Such activity may include, but not be limited to removal of offending trees or brush or the accumulation of sediment in the main channel that is necessary to restore flow carrying capacity of the main channel.
13. Disturbance resulting from permitted stream and/or wetland mitigation projects is permitted, provided that mitigation is applied to offset impacts to local wetlands, per subsection 935.08(e)(6) of this chapter.
14. Disturbances in the Stream Corridor Protection Zone necessary to accomplish the uses described in paragraphs 1 through 12 of this subsection are also authorized. However, all such disturbances shall be minimized and any necessary disturbances shall be mitigated per subsection 935.08(e)(6) of this chapter
B. Prohibited Uses and Activities. Any use not authorized under these regulations shall be prohibited in the Stream Corridor Protection Zone. By way of example, the following uses are specifically prohibited, however prohibited uses are not limited to those examples listed here:
1. There shall be no buildings/structures (except permitted bridges), swimming pools, signs, billboards, fences, or other structures deemed unacceptable by the City Administrator.
2. Dredging or Filling. There shall be no drilling, filling, dredging, grading, or dumping of soils, spoils, or solid materials, except for fill associated with permitted uses listed in subsection 935.08
(e)(8)(A)(1 through 14) above. Floodplain fill activity must be compliant with the City's permitting requirements contained in the Chapter 1341
"Flood Damage Prevention".
3. Unless otherwise associated within a Permitted Use under subsection 935.08(e)(8)(A), no structural sediment controls (e.g., the installation of silt fence or a sediment settling pond) or structural post-construction controls shall be used in the following subzones of the Stream Corridor Protection Zone:
a. Stream channel subzone
b. Streamside Buffer subzone
c. Areas in the Outer Buffer subzone that are within the existing 100-year floodplain area., as defined by FEMA.
Activities and controls that would not impair the floodplain or stream stabilizing ability of the outer buffer can be considered.
4. Motorized Vehicles. There shall be no use of motorized vehicles except as needed for activities associated with those listed in subsection 935.08
(e)(8)(A)(1 through 14) above.
5. Parking Lots. There shall be no parking lots or storage of vehicles or other human made impervious cover except as allowed above.
6. Stormwater Detention Facilities. Stormwater detention facilities are not allowed within the following subzones of the Stream Corridor Protection Zone:
a. Stream channel subzone
b. Streamside Buffer subzone
c. Areas in the Outer Buffer subzone that are within the existing 100-year floodplain area, as defined by FEMA..
7. Stormwater Pipe Outfalls, including headwalls, endwalls, and associated outlet open ditches should be located outside the Stream Corridor Protection Zone, where feasible and elevations permit, unless otherwise approved by the Administrator. Stormwater pipe outfalls shall discharge into a structural level spreader or a constructed open channel with appropriate protection from erosion that should also be outside the Stream Corridor Protection Area.
8. Private Utility lines and pipes that run parallel to the stream shall not be located in the Stream Corridor Protection Zone. Moreover, the following related private utility features are not permitted within the Stream Corridor Protection Zone: substations and their appurtenances that support private utilities.
9. Platted Lots. No part of any lot to be developed will be located within the Stream Corridor Protection Zone.
10. Other prohibited uses, unless otherwise designated a permitted or conditional use by the City, including:
a. Agriculture
b. Industry/commercial
c. Removal of topsoil, sand, gravel, rock, oil, gas
d. Application of herbicides/pesticides
C. Non-conforming Uses and Structures within the Stream Corridor Protection Zone.
1. A non-conforming use, existing at the time of passage of this regulation and within a Stream Corridor Protection Zone that is not permitted under this regulation may be continued but shall not be changed to a new use or enlarged unless changed to a use permitted under this regulation.
2. A non-conforming use, existing at the time of passage of this regulation and within a Stream Corridor Protection Zone that is not permitted under this regulation may be continued but shall not have the existing building footprint or roofline expanded or enlarged.
3. A non-conforming use, existing at the time of passage of this regulation and within a Stream Corridor Protection Zone that has substantial damage and that is discontinued, terminated, or abandoned for a period of six (6) months or more may not be revived, restored or re-established. "Substantial damage" means damage of any origin sustained to a structure whereby the cost of restoring the structure to its before damaged condition would equal or exceed 50 percent of the market value of the structure before the damage occurred
D. Maintenance of the Stream Corridor Protection Zone.
1. Disturbance of Natural Vegetation. There shall be no disturbance of the natural vegetation at any time, including during construction of the remainder of the site, except for such conservation maintenance that the landowner deems necessary to control noxious weeds; for such plantings as are consistent with these regulations; for removal of invasive species and their replacement with native vegetation; and for the passive enjoyment, access, and maintenance of landscaping or lawns existing at the time of passage of these regulations except as need for activities associated with those listed above.
2. Recommended Vegetation for Stabilizing Floodprone Areas. Proper selection of species for stabilization of floodprone areas is dependent on several factors, including soil conditions, available water and amount of sun exposure. Proper species selection and installation will take into account these factors. Refer to the City's list of "Species of plants and shrubs recommended for Stabilizing Flood Prone Areas", which is contained in a Technical Guideline for Mitigation, available in the office of the City Administrator.
(9) Appeals relating to provisions of this subchapter involving the Stream Corridor Protection Zone. Any person may appeal decisions or interpretations of the City Administrator, or his designee, issued in connection with the enforcement of any provisions of Section 935.08
(Stream Corridor Protection Zone) or request variances therefrom, provided that such person shall file in the office of the City Administrator, along with the fees established by Council for appeals and variances, a written petition to the Appeals Board as provided below.
A. The Appeals Board. The Appeals Board established under Section 939.24, shall hear and determine appeals of or variances to this Section 935.08 (Stream Corridor Protection Zone) and relating only to requirements under Section 935.08 and, upon receipt of a petition setting forth the requirements of Section 939.26 and the required fee(s), the Appeals Board shall set a time and place for a public hearing and shall give the petitioner written notice thereof. At the hearing, the petitioner shall be given an opportunity to be heard and show cause why any decision, interpretation or any item appearing on a notice or order should be modified or denied or a variance granted.
After a hearing, the Appeals Board shall sustain, modify or deny any item appealed or grant a variance by majority vote, depending on its findings as to whether the provisions of this chapter have been complied with, and the petitioner and the City Administrator shall be notified in writing of such findings.
The proceedings at such hearings, including the findings and decision of the Appeals Board and reasons therefor, shall be summarized and reduced to writing and entered as a matter of public record in the office of the City Administrator. The record shall also include a copy of every notice, order or variance issued in connection with the matter.
B. The failure of the petitioner or his representative to appear and state his case at any hearing shall have the same effect as if no petition had been filed.
C. Filing fees required by this section shall be in addition to the payment of the permits and inspection fees and any other fee which thereafter may occur, and no portion of such filing fee shall be refunded whatever the outcome of the appeal unless such petition shall have been withdrawn prior to the date set for such hearing.
D. Contents of Petition for Appeal.
1. The complainant shall set forth in the petition for appeal, the interpretation, ruling or order appealed from, and the related provisions of this chapter or related laws or ordinances, and shall state wherein the interpretation, ruling, or order is erroneous. If the appeal is a request for variance, the petition shall point out the provision or provisions from which the variance is sought and how the request satisfies the requirements of this section.
2. Petitions to the Appeals Board, in appeals filed in accordance with Section 939.25(a), may only be based on one of the following grounds:
a. The interpretation, ruling, or order is erroneous or constitutes an erroneous application of the particular provisions of this chapter or other related laws or ordinances pertaining to stormwater management, or is otherwise contrary to law, or
b. A variance is necessary and feasible and meets all of the following conditions:
i) Good and sufficient cause based on an unreasonable burden or hardship has been proven;
ii) The degree of variance is the minimum necessary to afford relief from the unreasonable burden or hardship imposed by this chapter or standards, specifications, requirements, regulations, and procedures adopted pursuant to this chapter;
iii) The variance may be granted without defeating the public health, safety, and welfare purposes and intent of this chapter or related laws or ordinances pertaining to stormwater management and finance.
(Ord. 13-012. Passed 5-13-13.)
(f) Detention Facilities.
(1) Ownership and maintenance. The owner and thus responsible party to provide maintenance and operation of a stormwater management facility (i.e., detention, retention basin, etc.), whether public or private, shall be determined to the satisfaction of the Municipality prior to the acceptance by the Municipality’s Council of the relevant subdivision plat and the acceptance of the final engineering and construction plan. No lot sales will be permitted until this is done.
(2) Location. All stormwater management facilities will be located in a reserve/open space as shown on the preliminary plat and final plat and will be owned by a homeowners association or an entity otherwise approved by the Municipality’s Council.
(3) Types of facilities. In development and developing urban and suburban areas, several means for controlling stormwater runoff could be used. This usually involves storing runoff on or below the ground surface. The following types of storage facilities may be considered for detention and are subject to approval by the Municipality’s Engineer: rooftops, parking lots, underground tanks and surface basins or ponds (i.e., dry or wet detention) and man-made stormwater wetland systems:
A. Parking Lot Storage. Parking lot storage is surface storage where shallow ponding is designed to flood specific graded areas of the parking lot. Controlled release features are incorporated into the surface drainage system of the parking lot. Parking lot storage is a convenient multi-use structural control method where impervious parking lots are planned. Design features include small ponding areas with controlled release by pipe-size and slope, and increased curb heights.
The major disadvantage is the inconvenience to users during the ponding function. This inconvenience can be minimized with proper design consideration. Clogging of the flow control device and icy conditions during cold weather are maintenance problems. Parking lot design and construction grades are critical factors. This method is intended to control the runoff directly from the parking area, and is usually not appropriate for storing large runoff volumes.
1. Ponding areas in parking or traffic areas shall be designed for a maximum potential depth of twelve (12) inches.
2. Flood routing or overflow must occur after the maximum depth is reached.
B. Tank Storage Tank storage utilizes an underground tank or chamber, either prefabricated or constructed in place, which has a special controlled release feature. This method is most applicable where land area is valuable, such as in industrial and commercial areas. Construction cost and operation costs, make this method relatively expensive. Storage trenches, a variation on basic tank storage, are rock-filled underground storage tanks. The storage is provided within the void spaces between the rock material.
C. Surface Basin - Wet Detention (pond) Wet Detention Basins (Ponds) are permanent ponds where functional stormwater management storage is provided above the normal water level with special features for controlled release. Historically, wet detention basins have proven extremely effective in abating increased runoff and channel erosion from urbanized areas. They are a major Soil Conservation land treatment practice.
Some problems encountered with wet detention basins are: site reservation (land requirements), permanent easements, complexity of design and construction, safety hazards and maintenance problems. Because of large land requirements, and the necessity of maintaining a permanent pool of water, wet detention basins have a broader application for in-stream control where large watershed areas are involved compared to their use as on-site facilities for small urban areas. However, the recreational and aesthetic benefits of permanent wet detention ponds may justify certain on-site applications. A five (5) foot chain link fence may be required where a wet retention basin is to be constructed adjacent to an existing single-family development for that part along the existing single-family section.
1. The Municipality encourages use of fountains for aeration and reserves the right to require such an appurtenance as a condition to plan approval.
2. The steepest side slopes for a Wet Detention basin should be:
i. 2:1 horizontal to vertical - below permanent storage, and
ii. 6-foot wide, 2-foot deep submerged bench at waters edge around perimeter of pond, and
iii. 5:1 horizontal to vertical - above permanent storage.
3. Unless otherwise approved by the Municipality’s Engineer, a minimum of 20 % of the pool area should be ten-feet deep for water-quality benefit.
4. Rock Channel Protection Type D, may be required to be placed at the normal water elevation, around the entire perimeter of the basin, five feet wide, centered on the normal water elevation.
5. Debris-control structures: Debris-control structures may be required and should be considered as an essential part of the design. The procedure recommended for use is Hydraulic Engineering Circular No. 9, available from the Superintendent of Documents, U.S. Government Printing Office, Washington D.C. For dams and levies over ten feet in height, refer to Section 1521.062, O.R.C.
D. Surface Basin – Dry Detention Dry detention basins are surface storage areas created by constructing a typical excavated or embankment basin. There is no normal pool level and a specific controlled release feature is included to control the rate of discharge.
Dry detention basins are a widely used method of stormwater management. The soil permeability and water storage potential are not as important with dry detention basins as with wet detention. Therefore, dry detention basins have the greatest potential for broad applications. They can be utilized in small developments because they can be designed and constructed as small structures or can be integrated into open, usable spaces for multi-use purposes such as recreation and parks.
1. The steepest side slopes for a Dry Detention basin should be 5:1.
2. Dry detention basin bottoms shall be sloped to drain, and such slopes shall be sufficient to mitigate against "flat spots" developing due to construction errors and soil conditions; or, bottoms shall be paved. The absolute minimum transverse slope the bottoms of such facilities shall be 0.50 %, and 2.0 % is the recommended transverse slope. All transverse bottom slopes flatter than 1 ½ % to and including 0.5 %, should be lined with 6-inch minimum thickness concrete, reinforced with steel mesh to accommodate temperature stresses, of air-entrained Class C concrete, and with synthetic linseed oil waterproofing treatment.
3. Invert ditches within dry detention basins, from the inlet to the outlet of all structures shall be paved if the slope is less than 0.50 %. Such ditches shall be paved with 6-inch minimum thickness concrete paving reinforced with steel mesh to accommodate temperature stresses, of air-entrained Class C concrete, and with synthetic or linseed oil waterproofing treatment. Minimum depth of paved invert ditch should be 1 foot.
4. Debris-control structures. Debris-control structures may be required and should be considered as an essential part of the design. The procedure recommended for use is Hydraulic Engineering Circular No. 9, available from the Superintendent of Documents, U.S. Government Printing Office, Washington D.C. For dams and levies over ten feet in height, refer to Section 1521.062, O.R.C.
E. Man-made Stormwater Wetland system: This technique involves a stormwater management facility that is intended to provide a water-quality benefit and incorporates a wetland system for water treatment. Use of this type of system must first be discussed with and reviewed by the Municipality’s Engineer prior to design to determine acceptance by the Municipality. Suggested design guidelines include:
1. Urban Runoff Quality Management: WEF Manual of Practice No. 23 and ASCE Manual and Report on Engineering Practice No. 87,. Water Environment Federation and American Society of Civil Engineers, 1998.
2. Design of Stormwater Wetland Systems: Guidelines for Creating Diverse and Effective Stormwater Wetland Systems, Thomas R. Schueler, Anascotia Restoration Team, Department of Environmental Programs, Metropolitan Washington Council of Governments, October 1992.
(Ord. 08-021. Passed 4-14-08.)
(Ord. 08-021. Passed 4-14-08.)