A drainage system shall be designed and constructed by the subdivider to provide for the proper drainage of the surface water of the subdivision and the drainage area of which it is a part. To this end the subdivision shall be graded as required by § 151.075 (Schedule of Required Improvements) and the following requirements and methods shall be followed:
(A) Drainage plan. Prior to the start of any construction (houses or streets), the subdivider shall furnish a plot plan showing the slab or floor elevation of each house proposed to be constructed. He shall also show by the use of arrows how he proposes to surface drain each lot. The subdivider shall submit topographic maps showing the area to be drained with calculations prepared by a registered professional engineer in determining the proposed storm water collection system.
(B) Drainage requirements (grading). No final grading or sidewalk or pavement construction or installation of utilities shall be permitted in any proposed street until the final plat has been approved, or conditionally approved. The subdivider shall grade each subdivision as specified in § 151.075 (Schedule of Required Improvements) in order to establish street, block, and lot grades in proper relation to each other and to topography, as follows:
(1) Street grading plan. A grading plan shall be prepared for the streets along with street improvement details. The grading of the roadway shall extend the full width of the right-of-way. Planting strips shall be graded at a gradient of not less than 2% or more than 3% upward from the curb to the sidewalk or property line.
(2) Block and lot grading.
(a) Block grading shall be as follows:
1. A ridge along rear lot lines, draining into the streets.
2. Parts of all lots draining to a sidewalk or ditch along rear lot lines.
(b) Lot grading shall be as follows: Lots shall be graded so that water drains away from each building at a minimum grade of 2%. Surface drainage swales shall have a minimum grade of 2% and shall be designed so that surface water will drain into a driveway, street gutter, storm sewer, drain inlet or natural drainage way. The minimum grades of driveways shall be 4/10% and a maximum of 153.
(3) Topsoil. If grading results in the stripping of topsoil, the topsoil shall not be removed from the site or used as fill, but saved and uniformly spread over the lots as grading is finished.
(4) Trees. As many trees as can be reasonably utilized in the final development plan shall be retained and the grading adjusted to the existing grade at the trees.
(C) Drainage systems requirements. The design criteria for the drainage systems shall be based on the State of Ohio Department of Highways, Manual of Locations and Design. Run off or design discharge for sewer design where the contributing area generally consists of pavement and a barrow strip back of the pavement, shall be obtained from the rational formula: Q=Cia (See Manual of Location and Design). Peak rates of runoff from water sheds under 1,000 acres shall be obtained from the following formula:
Q=RF x CF x FF x Q (See Manual of Location and Design). The following minimum design frequencies are to be used:
Roadway ditches 2 years
Storm sewers 10 years
Culvert under roadways 25 years
Watercourses 10 years
(1) Road drainage system. The road storm drainage system shall serve as the prime drainage system. It shall be designed to carry roadway, adjacent land, and house storm water drainage.
(2) The storm sewer system shall also comply with the latest erosion and sediment control and storm water management requirements of the village.
(a) Road storm sewers (enclosed).
1. The design discharge used to determine pavement inlet spacing shall be based on the rational method mentioned in division (C) above. The gutter flow between inlets shall be calculated by the equation: Q=.26 Z/N S1/2 F8/3. (See Manual of Location and Design)
2. The inlet spacing shall be based on a ten-year frequency, 15 minutes duration design storm. The spread of water on the pavement shall be limited to two feet into the traveled lane. In addition, standard manholes, or combination manhole inlets for cleaning purposes shall be placed no further than 300 feet apart.
(b) Off-road drainage systems. The design of the off-road drainage system shall include the watershed affecting the allotment and shall be extended to a watercourse or ditch adequate to receive the storm drainage.
1. All watercourses or ditches with a design capacity not exceeding the capacity of a 36 inch concrete pipe shall be enclosed. Existing creeks or ditches constructed by the subdivider which exceed the above limits shall be constructed with a minimum 15 foot wide continuous earth roadway to provide access for maintenance equipment to all sections of the ditch. The ditch easement shall be wide enough to contain said ditch slopes and roadway with ample clearance for the operation of maintenance equipment. Open ditches will have a side slope ration of 2:1 and a minimum two-foot bottom width.
2. No open ditch shall be constructed within 100 feet of the rear of a house as measured from the house to the edge of the ditch easement.
3. Any storm drainage courses carried alongside lot lines shall be enclosed with approved pipe.
(3) Drainage easement. Easements for drainage purposes shall be a minimum of 20 feet in width. Where the watercourse is large, easement widths shall be increased as determined by the Village Engineer. Where watercourses cross plotted lots diagonally the subdividers shall straighten such courses where practicable and shall substantially follow sublot lines. Easements shall be shown on the record plat and deeds shall cover all existing or reconstructed watercourses.
(4) Protection of drainage systems. The subdivider shall adequately protect all ditches (roadways and watercourses) to the satisfaction of the Village Engineer as follows:
(a) Any watercourse having a gradient in excess of 2½% shall be enclosed with pipe with the necessary inlets and shall be piped to a storm sewer, if nearby, or otherwise to a natural watercourse. Where a street is of considerable length and of various gradients, part of which require storm sewers, the lengths between the storm sewers even though less than 2½% gradient shall also be enclosed in pipe, when required by the Village Engineer, material and construction shall be in accordance with the specifications of the Village Engineer. Watercourses or road gutters having a gradient exceeding 1½% shall be sodded or paved with brick, concrete, half tile or broken concrete slabs. All areas within the right-of-way not paved or sodded shall be fertilized and seeded.
(b) All adjoining land where the vegetation has been injured or destroyed where the land is in need of protection to prevent erosion, deposits in the drainage facilities and/or unsightly conditions shall be restored and protected by the Village Engineer.
(c) In all cases, any drainage facility within the subdivision shall be in a stable condition, free from either erosion or sedimentation and/or other debris.
(5) Pipe policy. The pipe policy of the current State of Ohio Department of Transportation. "Construction and Material Specifications" shall be used in designing storm sewer systems subject to the approval of the Village Engineer.
(Ord. 2018-80, passed 11-20-18)