A. Drainage System Required: An adequate system of stormwater drainage shall be constructed and installed consisting of natural watercourses, storm sewers and other necessary facilities which will drain the subdivision and protect roadway pavements.
B. Storm Drainage Computations:
1. Required For Entire Area: Storm sewers, where required, shall be constructed throughout the entire area contemplated for development. Such storm sewer shall be connected to adequate outfall. Intercepting storm water structure shall be provided at intervals approximately four hundred feet (400') as measured along the center line or as determined by the kind of character and runoff as approved by the Village Engineer.
2. Separate And Independent Systems: Storm sewer and sanitary sewer shall be separate and independent systems.
3. Structural Requirements: Storm sewer shall generally be constructed of concrete pipe with sufficient strength to develop the structural requirements necessary for the type of storm sewer to be constructed.
4. Capacity: Storm sewer capacity shall be determined by the use of the rational formula. The intensity (I) factor used shall be a return frequency of not less than five (5) years. The runoff coefficient (C) factor shall be determined by the character of the land to be drained in its developed state.
5. Grades And Drainage: All street grades, lot and block drainage shall be established so as to permit positive drainage.
6. Prevention Of Flooding: In areas where runoff from storms of greater intensity than those which the storm sewers are designed for will cause flooding of adjacent property, one of the following alternate procedures shall be instituted to preclude the possibility of flooding:
a. Storm sewers shall be installed on both sides of a roadway beneath the center line of the roadside ditch with intercepting storm water structures as in subsection B1 of this Section.
b. Storm sewers shall be designed to provide runoff capacity for maximum storm of record.
c. Contours of land shall be changed by grading to assure positive drainage.
7. Construction Of Detention Ponds: Construction of detention ponds shall be in accordance with the Village Engineer and the Village requirements.
A dry flow drainage shall be provided in detention areas.
Detention areas must be capable of total drainage in not over seventy two (72) hours.
Total area of parks with detention ponds shall be not less than five (5) acres.
8. Dry Land Bridge: Where any roadway within the subdivision crosses ground wherein peat or unstable materials are situated, the Village may require that the subdivider build a dry land bridge encompassing the roadway as it crosses such ground, or the subdivider shall remove such peat or unstable material and replace it with stable solid fill.
9. Culverts: To facilitate the flow of surface water along the ditches as specified in this Section, and to prevent standing pools of water:
a. All culverts shall be designed to accommodate a five (5) year frequency for one hour duration for the total watershed area tributary to the culvert.
b. Culverts shall be placed beneath private driveways and a minimum of eight inches (8") shall be maintained between the top of the pipe and the roadway surface. For culverts under dedicated streets and roads a minimum of twelve inches (12") shall be maintained between the top of the pipe and the roadway surface. Culverts shall be reinforced concrete pipe (RCP CLIV).
c. Culverts beneath driveways shall be a minimum diameter of twelve inches (12"). Culverts beneath dedicated streets shall possess a minimum diameter of fifteen inches (15").
10. Ditches:
a. All ditch lines shall have a minimum width of six feet (6'). All ditch lines shall be sodded and pegged, as determined by the Village Engineer.
b. All slopes greater than four to one (4:1) shall be sodded and pegged.
c. Sedimentation basins shall be constructed at all points of discharge. (Ord. 99-O-791, 6-7-1999)