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;
(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;
(e)
Submerged gravel wetlands;
(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:
(a)
Stormwater management ponds;
(b)
Stormwater management wetlands;
(c)
Stormwater management infiltration;
(d)
Stormwater management filtering systems; and
(e)
Stormwater management open channel systems.
(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.