A. Minimum depth of open drainage ditches or swales before installation of a storm culvert or conduit shall be eighteen inches (18") below the edge of the roadway surface, unless otherwise approved by the City Engineer. Maximum allowable depth of open drainage ditches or swales along local streets shall be two feet (2') below the edge of the roadway surface before enclosure with a conduit is required. (Ord. 0-82-02, 2-16-1982)
B. Minimum ditch gradient of open drainage ditches or swales shall be five-tenths of one percent (0.5%) with a positive direction of drainage to a proper or approved outlet or point of discharge. For ditch gradients less than five-tenths of one percent (0.5%), the flow line of the ditch shall have a four inch (4") thick by eighteen inch (18") wide granular (CA-6, grade 8) invert covered by four inches (4") of topsoil and grass or sod layer. If a ditch gradient of three-tenths of one percent (0.3%) cannot be maintained, storm sewers shall be installed. (Ord. 0-79-16, 6-18-1979)
C. Side slopes for open drainage ditches shall be maximum four to one (4:1) (horizontal to vertical) from the roadway shoulder to a two foot (2') minimum wide ditch flow line and a four to one (4:1) or less slope back to the right-of-way line. Changes to the minimum slopes may not be made unless approved by the City Engineer; but in no case shall the slope from the shoulder be greater than three to one (3:1) nor the flow line less than two feet (2') wide. The shoulder shall be four feet (4') in width with the two feet (2') adjacent to the pavement edge to be gravel over a stabilized base as approved by the City Engineer.
This provision for four to one (4:1) side slopes shall be effective April 1, 1989, and shall apply to all new subdivisions, road reconstruction projects where appropriate, and other drainage improvement projects unless otherwise authorized by the City Engineer. (Ord. 0-89-11, 4-3-1989)
D. No open roadway ditch or swale shall be filled or cross- sectional area reduced without first ensuring proper drainage over or across the property in question. Roadway drainage ditches may be filled if a properly sized culvert pipe is installed at an approved gradient. In general, corrugated metal pipe culverts may be used for lengths up to one hundred feet (100'). For culvert lengths in excess of one hundred feet (100'), a reinforced concrete pipe or equivalent shall be used.
If an intermediate drainage opening is required in culvert length up to one hundred feet (100'), an inlet box with an open grate shall be provided at minimum fifty foot (50') intervals.
E. All previous sections of drainage ditches or swales must have acceptable erosion protection or side slope stabilization. The "Standards and Specifications for Soil Erosion and Sediment Control for Northeastern Illinois Planning Commission" and the "Standard Specifications for Road and Bridge Construction", current editions, may be used as guidelines for implementation of acceptable measures for erosion protection of bank stabilization.
F. Culvert sizing and specifications shall be as follows:
1. Proper size and type of culvert as determined or approved by the City Engineer, based upon the local watershed drainage area tributary to the culvert in question.
2. Minimum culvert diameter of twelve inches (12") or multiple eight inch (8") diameter culverts, if approved. For culverts fifteen inches (15") in diameter or larger and culverts crossing public streets, flared end sections of the appropriate size and material will be required.
3. Culvert materials of corrugated metal pipe (CMP), reinforced concrete pipe (RCP), or approved equal by the City.
4. Minimum four inch (4") thick granular (CA-6, grade 8) bedding, extending one foot (1') beyond the ends of the culvert pipe. (Ord. 0-79-16, 6-18-1979)
5. Minimum three foot (3') extension of culverts beyond a driveway or roadway edge, unless a headwall structure is installed.
6. Minimum eight inches (8") of cover from top of culvert pipe to finished driveway surface. Minimum of six inches (6") of cover from top of culvert pipe to the finished edge of pavement surface on minor streets, unless otherwise approved by the City. (Ord. 0-82-02, 2-16-1982)
7. Proper grade or invert elevations as established, set or approved by the City.
G. New construction, reconstruction or roadway improvements shall not be initiated until a construction permit from the Building Official with the sanction or recommendations from the City Engineer has been obtained.
H. All costs associated with the setting of culverts, establishing or checking ditch gradients, correcting deficiencies or bringing ordinance violations into compliance, issuance of permits, or payment of penalties shall be the responsibility of the property owner(s) or developer(s) required to do the necessary drainage work. (Ord. 0-79-16, 6-18-1979)