The on-site control measures shall be designed based on the size of the disturbed areas as follows:
(A) For disturbed areas draining less than one acre, filter barriers (including filter fences, straw bales, or equivalent control measures) shall be constructed to control all off-site runoff as specified in referenced handbooks. Vegetated filter strips with a minimum width of 25 feet may be used as an alternative where runoff in sheet flow is expected.
(B) For disturbed areas draining more than one acre but less than five acres, a sediment trap or equivalent control measure shall be constructed at the downslope point of the disturbed area in conjunction with other filter barriers.
(C) For disturbed areas draining more than five acres, a sediment basin or equivalent control measure shall be constructed at the downslope point of the disturbed area in conjunction with other filter barriers.
(D) Sediment basin and trap design shall provide for both detention storage and sediment storage. The detention storage shall be for equal volumes of "wet" detention storage and "dry" detention storage. Each shall be sized for the two-year, 24-hour runoff from the site. The release rate shall be that rate required to achieve a minimum detention time of ten hours. The outlet structure shall be placed such that it only drains the dry detention storage.
(E) The sediment storage shall be sized to store the estimated sediment load generated from the site over the duration of the construction period with a minimum storage equivalent to the volume of sediment generated in one year. A sediment removal schedule is required for construction periods exceeding one year.
(Ord. 2004-008, passed 6-16-04)