Revision D – August 20th, 2021 Page 7
Notes:
1. Drain rock shall be graded from 1 inch to ¼ inch.
2. Drain rock shall be encased in a filter fabric material to avoid soil infiltration into the drain rock.
3. Recommended depth of drain rock unit varies dependent upon the type of existing soils.
a. Where existing soils are granular and permeable the depth of the drain rock unit can be
limited to 1 foot.
b. Where existing soils are fine graded and have low permeability the depth of the drain
rock unit should be increased to 3 feet or greater to provide a reservoir for short term
retention. Refer to engineering plans for the requirements specified by the project
engineer.
4. Concrete shall be 3/8 inch maximum aggregate mix, use a minimum of seven sacks of cement
per cubic yard of concrete and poured from a height of approximately 5 inches above the can.
Concrete should only be poured from one side. Vibrate or rod concrete to completely fill the
area below and on all sides of the base can. When concrete is visible on the side opposite to
the side that concrete is being poured from, pouring can commence from alternate locations.
5. Abbreviations: Asphalt Concrete (AC), Aggregate Base (AB).
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