Every engineering plan shall include a topographic survey of the existing project site and shall be signed and sealed by a licensed Illinois professional land surveyor. All topographic data shall be collected a minimum of fifty feet (50') beyond the project site, but in no case less than is necessary to determine all area drainage patterns that may effect, or be affected by construction of the subdivision. All plans shall indicate the existing contours with one foot (1') contour interval. The existing contours and spot elevations must be indicated on the plans in a lighter line style or shade to provide distinction between the existing and proposed conditions. All topographic surveys shall provide bench mark information and shall be based on NGVD 1988.
The minimum slope for all vegetated areas shall be two percent (2%) unless approved by the Village Engineer under special conditions. The maximum slope for all transition areas shall be twenty five percent (25%).
Minimum slopes for parking areas shall be 0.50 percent and the maximum slopes shall be 4.0 percent. All parking areas that are adjacent to, and slope toward, stormwater detention facilities shall be constructed with guardrails or sufficient structural parking stops to minimize or preclude the possibility of unattended vehicles rolling into the detention facility.
All grading plans shall indicate proposed spot elevations at a minimum of every fifty feet (50'). The calculated slope shall be shown with an arrow in the direction of the downward slope. Overland flood routes shall be shown with large arrows to depict the route.
Rim elevations for all storm sewer structures shall be shown on the grading plans. (Ord. 2018-02-20, 2-20-2018)