(A) To ensure against surface ponding or street flooding, the hydraulic grade line (“HGL”) in any public inlet, catch basin or manhole must be below the rim elevation of the structure for the 100-year check storm. The headwater and tailwater elevations for the ten-year storm and 100-year check storm and outlet velocities shall be shown on all profiles of the public storm water system on the plans or on storm sewer profiles included with drainage calculations.
(B) To ensure proper conveyance of storm water runoff to a control facility on private property, the submittal must include information verifying that the headwater elevation for the 100-year storm in any inlet or manhole is not higher than the inlet grate. The headwater and tailwater elevations for the ten-year storm and 100-year check storm shall be shown on all profiles of the private storm water system on the plans or on storm sewer profiles included with the drainage calculations and outlet velocities shall be included in the drainage calculations.
(C) The maximum allowable headwater shall not exceed 1.2 times the structure rise unless specifically approved by the approving agency on a case-by-case basis.
(Ord. 012-118, passed 10-8-2012)