GENERAL DESIGN REQUIREMENTS

1. The basin shall be designed to provide a minimum of 4 (four) feet between the basin bottom and the groundwater table.

2. One soil boring for each 10,000 square feet of basin bottom area to a depth of six feet below the bottom. In Accordance with Part I, II, B, and item 10.

3. Constructed basin sideslopes shall be no steeper than 5:1. However, these requirements may be waived for untouched Natural Low Areas.

4. All riprap must be stone.

5. Two feet of free board will be required above the 25-year stormwater elevation on all drainage facilities.

6. Basin Inlet Design:

a. An inline 60 inch concrete manhole with a 3 foot open bottom sump, filled with stone riprap will be required when discharge velocities are greater than 8.0 ft/sec.

b. Flared end sections with end section grates are required.

c. Stone rip rap apron.

1. 12 inch to 30 inch inlets require a minimum of 10 syd rip rap.

2. 30 inch to 60 inch inlets require a minimum of 25 syd rip rap.

3. Riprap shall be 8 inch stone or larger, minimum depth of 16 inches over filter fabric. MDOT standard heavy stone riprap may be required should velocities warrant.

7. Placement of retention/detention basins within the 100-year floodplain is prohibited.

8. Anti-seep collars are required on any pipe passing through the sides of any exterior embankment.