§ 17.10.085. Stormwater management measures.

The ESD planning techniques and practices and structural and nonstructural stormwater management measures established in this section shall be used, either alone or in a combination, in developing a stormwater management plan.

1.

ESD Planning Techniques and Practices.

a.

The following planning techniques shall be applied according to the Design Manual to satisfy the applicable minimum control requirements established in 17.10.080 of this Ordinance:

i.

Preserving and protecting natural resources;

ii.

Conserving natural drainage patterns;

iii.

Minimizing impervious area;

iv.

Reducing runoff volume;

v.

Using ESD practices to maintain one hundred percent of the annual predevelopment groundwater recharge volume;

vi.

Using green roofs, permeable pavement, reinforced turf, and other alternative surfaces;

vii.

Limiting soil disturbance, mass grading, and compaction;

viii.

Clustering development; and

ix.

Any practices approved by the Administration.

b.

The following ESD treatment practices shall be designed according to the Design Manual to satisfy the applicable minimum control requirements established in Section 17.10.080 of this Ordinance:

i.

Disconnection of rooftop runoff;

ii.

Disconnection of non-rooftop runoff;

iii.

Sheetflow to conservation areas;

iv.

Rainwater harvesting;

v.

Submerged gravel wetlands;

vi.

Landscape infiltration;

vii.

Infiltration berms;

viii.

Dry wells

ix.

Micro-bioretention;

x.

Rain gardens;

xi.

Swales;

xii.

Enhanced filters; and

xiii.

Any practices approved by the administration.

c.

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. The City shall modify Departments Planning and Zoning ordinances and Public Works codes to eliminate any impediments to implementing ESD to the MEP according to the Design Manual.

2.

Structural Stormwater Management Measures.

a.

The following structural stormwater management practices shall be designed according to the design manual to satisfy the applicable minimum control requirements established in Section 17.10.080(A) of this Code.

i.

Stormwater management ponds;

ii.

Stormwater management wetlands;

iii.

Stormwater management infiltration;

iv.

Stormwater management filtering systems; and

v.

Stormwater management open channel systems.

b.

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.

c.

Structural stormwater management practices shall be selected to accommodate the unique hydrologic or geologic regions of the State.

3.

ESD planning techniques and treatment practices and structural stormwater management measures used to satisfy the minimum requirements in Section 17.10.080 of this Ordinance must be recorded in the land records of Anne Arundel County and remain unaltered by subsequent property owners, unless prior approval from the Department of Public Works shall be obtained before any stormwater management practice is altered or removed.

4.

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.

5.

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 streamflow. 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.

6.

Incorporation of green roofs as part of the site design is encouraged. Applicant must show the quantity of storage for the design proposed which will be considered as an offset for the overall stormwater management requirement.

7.

Alternative structural and nonstructural stormwater management practices may be used for new development water quality control if they meet the performance criteria established in the design manual and approved by the administration. Practices used for redevelopment projects shall be approved by the Department of Public Works.

8.

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 any downstream area and any downstream appurtenances, structure, obstructions and hydraulically significant natural features. The points of investigation are to be established with the concurrence of the Department of Public Works.

9.

Stormwater management and development plans where applicable, shall be consistent with adopted and approved watershed management plans, flood management or floodplain management plans as approved by the Maryland Department of the Environment in accordance with the Flood Hazard Management Act of 1976 and any subsequent revisions.

(Ord. No. O-59-09, § I, 12-21-2009; Ord. No. O-26-10, § I, 9-13-2010)