§ 22-3. Minimum control requirements.

(a) In general.

The minimum control requirements for these management measures are as provided in this section and the State's Design Manual.

(b) Volume sizing criteria.

(1) The criteria in the State's Design Manual for environmental site design to the maximum extent practicable and the use of environmental site design planning techniques and treatment practices must be exhausted before any structural best management practice or alternative practice is implemented.

(2) Stormwater management plans for development projects subject to this Division II must be designed using environmental site design sizing criteria, recharge volume, water quality volume, and channel protection storage volume criteria according to the State's Design Manual. The maximum-extent-practicable standard is met when channel stability is maintained, predevelopment groundwater recharge is replicated, nonpoint source pollution is minimized, and structural stormwater management practices or alternative practices are used only if determined to be absolutely necessary.

(c) 10-year frequency storm event.

Runoff from the 10-year frequency storm event must be controlled in accordance with the State's Design Manual if the Department determines that additional stormwater management is necessary because historical flooding problems exist and downstream floodplain development and conveyance system design cannot be controlled.

(d) Additional control requirements.

The Department may require more than the minimum control requirements of the State's Design Manual if:

(1) hydrologic or topographic conditions warrant; or

(2) flooding, stream channel erosion, or water quality problems exist downstream from a proposed project.

(e) Alternative minimum controls.

With the approval of the State Water Management Administration, the Department may adopt alternative minimum control requirements that will:

(1) implement environmental site design to the maximum extent practicable; and

(2) control flood damages, accelerated stream erosion, water quality, and sedimentation.

(f) Consistency with FHMA plans.

Where applicable, stormwater management and development plans must be consistent with watershed management plans and flood management plans approved by the State Water Management Administration under the Flood Hazard Management Act of 1976.