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.
B.
Stormwater management and development plans, where applicable, shall
be consistent with adopted and approved watershed management plans
or flood management plans as approved by the Maryland Department of
the Environment in accordance with the Flood Hazard Management Act
of 1976.[1]
[1]
Editor's Note: See Environment Article, Title 5, Subtitle
8, § 5-801 et seq., Annotated Code of Maryland.
The ESD planning techniques and practices and structural stormwater
management measures established in this chapter and Design Manual
shall be used, either alone or in combination, in a stormwater management
plan. A developer shall demonstrate that ESD has been implemented
to the MEP before the use of a structural BMP is considered in developing
the stormwater management plan.
A.
ESD planning techniques and practices.
(1)
The following planning techniques shall be applied according to the Design Manual to satisfy the applicable minimum control requirements established in § 325-10 of this chapter:
(a)
Preserving and protecting natural resources;
(b)
Conserving natural drainage patterns;
(c)
Minimizing impervious area;
(d)
Reducing runoff volume;
(e)
Using ESD practices to maintain 100% of the annual predevelopment
groundwater recharge volume;
(f)
Using green roofs, permeable pavement, reinforced turf, or other
alternative surfaces;
(g)
Limiting soil disturbance, mass grading, compaction and placing
four inches of topsoil on any area(s) which has been disturbed;
(h)
Clustering development; and
(i)
Any practices approved by the Administration.
(2)
The following ESD treatment practices shall be designed according to the Design Manual to satisfy the applicable minimum control requirements established in § 325-10 of this chapter:
(a)
Disconnection of rooftop runoff;
(b)
Disconnection of non-rooftop runoff;
(c)
Sheet flow to conservation areas;
(d)
Rainwater harvesting;
(e)
Submerged gravel wetlands;
(f)
Landscape infiltration;
(g)
Infiltration berms;
(h)
Dry wells;
(i)
Micro-bioretention;
(j)
Rain gardens;
(k)
Swales;
(l)
Enhanced filters; and
(m)
Any practices approved by the Administration.
(3)
The use of ESD planning techniques and treatment practices specified
in this section shall not conflict with existing state law or local
ordinances, regulations, or policies. Counties and municipalities
shall modify planning and zoning ordinances and public works codes
to eliminate any impediments to implementing ESD to the MEP according
to the Design Manual. In the event that there is a conflict between
local ordinances and the Cecil County Stormwater Management Ordinance,
the Stormwater Management Ordinance shall take precedence.
B.
Structural stormwater management measures.
(1)
The following structural stormwater management practices shall be designed according to the Design Manual to satisfy the applicable minimum control requirements established in § 325-10 of this chapter:
(2)
The performance criteria specified in the Design Manual with regard
to general feasibility, conveyance, pretreatment, treatment and geometry,
environment and landscaping, and maintenance shall be considered when
selecting structural stormwater management practices.
(3)
Structural stormwater management practices shall be selected to accommodate
the unique hydrologic or geologic regions of the state.
C.
ESD planning techniques and treatment practices and structural stormwater management measures used to satisfy the minimum requirements in § 325-10 of this chapter must be contained within an easement recorded in the land records of Cecil County and remain unaltered by subsequent property owners. Whenever feasible, ESD planning techniques and treatment practices and structural stormwater management measures must be contained within common open space areas. Placing stormwater management measures within areas which will become County right-of-way should be avoided. Prior approval from the Department of Public Works shall be obtained before any stormwater management practice is altered.
D.
Alternative ESD planning techniques and treatment practices and structural
stormwater measures may be used for new development runoff control
if they meet the performance criteria established in the Design Manual
and all subsequent revisions and are approved by the Administration.
Practices used for redevelopment projects shall be approved by the
Department of Public Works.
E.
For the purposes of modifying the minimum control requirements or
design criteria, the owner/developer shall submit to the Department
of Public Works an analysis of the impacts of stormwater flows downstream
in the watershed. The analysis shall include hydrologic and hydraulic
calculations necessary to determine the impact of hydrograph timing
modifications of the proposed development upon a dam, highway, structure,
or natural point of restricted stream flow. The point of investigation
is to be established with the concurrence of the Department of Public
Works, downstream of the first downstream tributary whose drainage
area equals or exceeds the contributing area to the project or stormwater
management facility.
The basic design criteria, methodologies, and construction specifications,
subject to the approval of the Department of Public Works and the
Administration, shall be those of the Design Manual.
