A.  GENERAL REQUIREMENTS

Every engineering plan shall include a topographic survey of the existing project site and shall be signed and sealed by an Illinois licensed Land Surveyor or an Illinois licensed Professional Engineer.  All topographic data shall be collected a minimum of one hundred feet (100’) beyond the project site.  All plans shall indicate the existing contours in one-foot (1’) intervals.  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.

The minimum grading shall be two percent (2.0%) for any grass area such as but not limited to residential lot, dry bottom detention facility, parkway, and commercial site and park areas.  Park areas such as but not limited to ball fields, track and field facilities, etc. can be exempt from the minimum grading slope if an under drain system is proposed.  The maximum transition grading shall be 4:1.

Minimum slopes for parking areas shall be 0.50% and the maximum slopes shall be 3.0%. Where driving surfaces are adjacent to stormwater detention facilities, retaining walls or steep slopes a guardrail or other safety measure may be required at the discretion of the City Engineer.  All roadways shall conform to the standards set forth in the Streets section of these standards.

For streets, pavement centerline and top curb elevations shall be indicated on the grading plan every 50’ minimum with a spot grade and at critical locations (High/Low Points, locations where flood routes enter or exit the right-of-way, PC and PT of curves and corner radii, etc.).

All developments shall be designed in compliance with the “Illinois Accessibility Code” latest revision.  Each sidewalk curb ramp, within the right-of-way, shall be identified as to which IDOT standard is to be followed.  Where necessary or required, a specific grading blow up of an individual sidewalk curb ramp will be provided.

All grading plans shall indicate proposed spot elevation in bold lettering 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, as defined in Section IV, shall be shown with large arrows to depict the route. Overland flood routes located in side yards is discouraged.  However, when it is unavoidable and a flood route is located in the side yard of a structure with a basement, there shall be no basement windows on the side of the house where the flood route is located.  Top of foundation/ lowest opening elevations shall be one foot (1’) above the 100 year BFE and shall be two feet (2’) above the 100-year BFE for the flood route if the tributary area is greater than 20 acres. At critical locations along the overland flood route, the 100-year High Water Level and Flow shall be indicated on the Grading Plan, along with the location of the critical points.

Rim elevations for all storm sewer structures shall be shown on the grading plans at a minimum.

B.  RETAINING WALL

Should a site require a retaining wall, a detail shall be indicated on the plans to indicate the type and style of wall to be used.  A retaining wall system that is greater than three feet (3’) in total height shall be designed and sealed by an Illinois licensed Structural Engineer.  A retaining wall less than three feet (3’) in height may require a design signed and sealed by an Illinois licensed Structural Engineer at the discretion of the City Engineer.  All retaining walls within a detention basin or near a driving surface will require a design signed and sealed by an Illinois licensed Structural Engineer.   Guardrail or other safety measures may also be required at the discretion of the City Engineer. The design criteria can be provided during the final engineering submittal.

Retaining walls around detention basins may not be continuous. There must be a sloped opening to allow for maintenance.  Also, walls greater than three feet (3’) in height are not permitted.  If a height of greater than three feet (3’) must be attained, the wall must be constructed in a terrace fashion, three feet (3’) maximum high wall to a minimum three feet (3’) wide terrace, then another three feet (3’) maximum wall to another minimum three feet (3’) wide terrace, etc. and shall be designed and sealed by an Illinois licensed Structural Engineer.

Top and bottom of the retaining wall elevations at every elevation change and every 25’ of wall length.

The Buildings and Permits Department should be consulted regarding the need for hand rails on the proposed retaining wall.

The under drain outlet shall be shown on the plans.  Underdrains shall not discharge across a sidewalk/path if adjacent to retaining wall.

The ends of the retaining wall shall transition so that the grading shall not exceed the maximum transition grading of 4:1