A.
The minimum control requirements established in this section and the Design Manual are as follows:
(1)
The Department of Public Works shall require that the planning techniques, nonstructural practices, and design methods specified in the Design Manual be used to implement ESD to the MEP. The use of ESD planning techniques and treatment practices must be exhausted before any structural BMP is implemented. Stormwater management plans for development projects subject to this chapter shall be designed using ESD sizing criteria, recharge volume, water quality volume, and channel protection storage volume criteria according to the Design Manual. The MEP standard is met when channel stability is maintained, predevelopment groundwater recharge is replicated, nonpoint source pollution is minimized, and structural stormwater management practices are used only if determined to be absolutely necessary.
(2)
In the coastal plain, the following minimum control requirements apply in accordance with the Design Manual and must be addressed utilizing ESD to the MEP:
(a)
Water quality volume;
(b)
Recharge volume;
(c)
Channel protection storage volume; and
(d)
Overbank flood protection volume for the two-year-frequency storm event may be required if the Department determines downstream conditions so warrant. (Structural practices may be considered only if ESD measures implemented to the MEP cannot provide the necessary volume.).
(3)
In the Piedmont Region, the following minimum control requirements apply in accordance with the Design Manual and must be addressed utilizing ESD to the MEP:
(a)
Water quality volume;
(b)
Recharge volume;
(c)
Channel protection storage volume; and
(d)
Overbank flood protection volume for the ten-year-frequency storm event may be required if the Department determines downstream conditions so warrant (Structural practices may be considered only if ESD measures implemented to the MEP cannot provide the necessary volume.).
(4)
Except as provided below, in the Transition Region the minimum control requirements shall be those as specified for the Piedmont Region. If an applicant demonstrates that the site to be developed within the Transition Region contains predominantly coastal plain characteristics for topography and soils, then the minimum control requirements shall be that of the coastal plain. To be considered predominantly coastal plain topography, the average slope on the site to be developed, from the highest elevation to the lowest elevation, must be 8% or lower. To be considered predominantly coastal plain soils, at the concept plan phase a soils report indicating that the site to be developed contains greater than 50% of soils determined by the Engineer to be classified as coastal plain. At the preliminary plan phase, the soils report must be certified and sealed by a Maryland-registered geotechnical engineer [See § 325-14(A)(6) for the minimum information required in a soils report.] for any proposed structural practices.
(5)
In addition to the applicable requirements above, all development and redevelopment activities that take place in the intensely developed areas (IDA) of the Chesapeake Bay Critical Area shall result in a reduction of pollutant loadings from the site by at least 10%. The process for determination of pollutant loading reduction shall be as outlined by the Critical Areas Commission in "A Framework for Evaluation of Compliance with the 10% Rule in the Critical Area," April 1987, or a comparable methodology as approved by the Department of Public Works.
(6)
The Department of Public Works may require more than the minimum control requirements for overbank flood protection for the two- and ten-year-frequency storm event if hydrologic or topographic conditions warrant or if flooding, stream channel erosion, or water quality problems exist downstream from the proposed project.