1248.03 STORM WATER MANAGEMENT AND EROSION CONTROL.
(a) General Requirements. All subdivisions shall provide detention/retention systems and make provision for storm and flood water runoff channels or basins in accordance with the City of Springboro Standard Construction Drawings and Specifications. The storm water drainage system shall be separate and independent of any sanitary sewer system. These design criteria are not intended to cover extraordinary situations. Deviations will be allowed and may be required in instances when considered justified by the City Engineer. Inlets shall be provided so that surface water is not carried across or around any intersection, or for a distance of more than three hundred and fifty feet (350’) in the gutter. When calculations indicate that curb capacities are exceeded at a point, no further allowance shall be made for flow beyond that point, and basins shall be used to intercept flow at that point. Surface water drainage patterns shall be shown for each and every lot and block.
(b) Location. The applicant, shall at the discretion of the City Engineer, be required to carry away by pipe any spring or surface water that may exist either previously to, or as a result of the subdivision. No open ditches shall be permitted unless specifically approved by the City Engineer. Pipes shall not be required to be installed when the diameter is in excess of sixty inches (60”). Exceptions to the piping requirement may be made for aesthetic water features as approved by the Planning Commission and City Engineer. Such drainage facilities shall be located in perpetual unobstructed easements of a width that meet generally accepted engineering principles.
(c) Accommodation of Upstream Drainage Areas. Storm sewers shall be designed to accommodate a ten-(10) year storm, post development tributary area, storm not including any detention.
(d) Effects on Downstream Drainage Areas. The developer shall also study the effect of each subdivision on existing downstream drainage facilities outside the area of the subdivision when requested of the City Engineer. Local government drainage studies together with such other studies as shall be appropriate and shall serve as a guide to needed improvements. Where it is anticipated that the additional runoff incidental to the development of the subdivision will overload an existing downstream drainage facility, the Planning Commission may withhold approval of the subdivision until provisions have been made for the expansion of the existing downstream drainage facility. No subdivision shall be approved unless adequate drainage will be provided to an adequate drainage watercourse or facility.
(e) Areas of Poor Drainage. Whenever a record plan is submitted for an area that is subject to flooding, the Planning Commission may approve such subdivision provided that the applicant fills the affected area of the subdivision to an elevation sufficient to place the elevation of streets and lots at a minimum of twelve inches (12”) above the elevation of the one hundred (100) year floodplain, as determined by FEMA Flood Insurance Rate Map (FIRM) information. In areas not covered by FIRM information, the City Engineer shall require the developer to establish a one hundred (100) year flood boundary. The record plan of the subdivision shall provide for a floodway along the bank of any stream or watercourse, in a width that shall be sufficient in times of high water to contain or move the water, and no fill shall be placed in the overflow zone nor shall any structure be erected or placed in the overflow zone. The boundaries of the overflow zone shall be subject to approval by the City Engineer. The Planning Commission may deny subdivision approval for areas of extremely poor drainage.
(f) Dedication and Drainage Easements.
(1) General requirements. When a subdivision is traversed by a watercourse, drainage way, channel, or stream, a storm water easement or drainage right-of-way shall be provided by the developer conforming substantially to the lies of such watercourse. The city is not responsible for the maintenance of said watercourses.
(2) Drainage easements. Where topography or other conditions are such as to make impractical the inclusion of drainage facilities within street rights-of- way, perpetual, unobstructed easements at least ten feet (10’) in width for drainage facilities, or as determined by the City Engineer, shall be provided across property outside the right-of-way and with satisfactory access to the right-of-way. Easements shall be indicated on the record plan. Drainage easements shall extend from the right-of-way to a natural watercourse or to other drainage facilities. Each lot shall contain a drainage easement along the side and or rear of the lot as required by the City Engineer. The city shall not maintain said drainage easements.
(g) Storm Water Management and Erosion Control
(1) Approval of a subdivision shall be conditioned upon the developer’s presentation of a detailed surface water management plan that will prevent erosion and not permit the discharge so that the runoff rate after development cannot be greater than the one (1)-year pre-development storm rate.
(2) Before a subdivision or parcel is cleared, graded or otherwise disturbed by the movement of earth by any person, partnership, or corporation, a Storm Water Management and Erosion Control Plan describing the proposed earth movement shall be provided to and approved by the City Engineer.
A. Lots shall be laid out so as to provide positive drainage away from all buildings, and individual lot drainage shall be coordinated with the Water Management and Erosion Control Plan for the development.
B. All disturbed ground shall be seeded within thirty (30) days of being disturbed.
(3) Performance principles. The following principles are effective in minimizing erosion and sedimentation and shall be included where applicable in the Water Management and Erosion Control Plan.
A. Stripping of vegetation, regrading or other development shall be done in a way that will minimize erosion. Natural vegetation shall be preserved whenever feasible.
B. Development plans shall preserve unique state or regional natural features, keep cut and fill operations to a minimum and ensure conformity with topography.
C. The smallest practical area of land shall be exposed at any one time and the duration of exposure shall be kept to a practical minimum. The topsoil shall be preserved and returned to the surface of areas to be re-vegetated, or new topsoil shall be provided, or the surface will be covered with sod, and structural erosion control shall be installed.
D. Disturbed soils shall be stabilized as quickly as practical, with temporary vegetation or mulching to protect exposed critical areas during development but no more than thirty (30) days or as determined by the City Engineer in accordance with generally accepted engineering practice as applied to the specific facts of the development.
E. The permanent final vegetation shall be installed within thirty (30) days final grading, or as determined by the City Engineer.
F. Provisions shall be made to effectively accommodate the increased runoff caused by soil and surface conditions during and after development. Retention and detention basins shall be provided according to the requirements of this section.
G. Sediment in the runoff water shall be trapped by the use of debris basins, sediment basins silt traps or similar measures until the disturbed area is stabilized.
(4) The following standards shall be followed in preparing StormWater Management and Erosion Control Plans.
A. All lots, tracts or parcels shall be graded to provide proper drainage away from the buildings and drains towards a natural stream, swale, storm sewer or other watercourse.
B. All drainage provisions shall be designed to comply with the standards set forth in Section 1248.08(g) above.
C. Concentration of surface runoff shall only be permitted in swales or watercourses.
D. The installation of specific storm water management and erosion control measures shall follow City of Springboro Standard Construction Drawings and Specifications.
(5) Proposed Storm Water Management and Erosion Control Plans shall include the following:
A. A vicinity sketch and boundary line survey of the project area.
B. Location of all existing buildings, structures, utilities, storm and sanitary sewers, and water lines in the project area as well as the next adjacent property or portion thereof within one hundred (100’) of the property line.
C. Locations of all trees greater than six inches (6”) in diameter as measured at a point five feet (5’) above the ground.
D. Location of all buildings and storm water sewers within one hundred feet (100’) of the project area.
E. Elevations, contours, dimensions, locations and extent of all work proposed to be done within and outside the project area, the existing elevations and contours of the land all in increments of two feet (2’), soil type, and proposed ground cover for areas not covered by buildings, structures or pavement.
F. Detailed plans of all proposed storm water provisions, retaining walls, vegetative practices, erosion and sedimentation control measures, location of fences around sediment basins, detention basins and other protective devices to be construed with or as part of the proposed project.
G. Provisions for maintenance of control facilities including easements to ensure short as well as long term erosion and sedimentation control.
H. A map showing the drainage area of land tributary to the project area and estimated runoff of the area served by any drainage structure or watercourse,
(6) Other provisions. In order to ensure that emergency measures could be taken by the City if the Storm Water Management and Erosion Control measures were not implemented according to the agreed upon plan and schedule, a performance bond in the amount of the cost of the water management and sedimentation control measures shall be required.
(h) Debris and Waste. No cut trees, timber, debris, earth, rocks, stones, junk, rubbish or other waste materials of any kind shall be buried on any buildable lot or street right of way, or left or deposited on any buildable lot or street right of way. Organic material may be buried on unbuildable lots.
(i) Security. The developer shall enter into a separate subdivider’s agreement secured
by a performance bond or cash escrow to guarantee completion of all lot improvement requirements including, but not limited to soil preservation, final grading, lot drainage, lawn/grass seeding, removal of debris and waste, fencing, and all other lot improvements required by the City Engineer before approval of the record plan by City Council. Whether or not a certificate of occupancy has been issued, the City may enforce the provisions of the subdivider’s agreement where the provisions of this section or any other applicable law, ordinance or regulation have not been met. (Ord. 04-41. Passed 8-19-04.)