Sec. 32-171. Definitions

Administration. The Maryland Department of the Environment (MDE) Water Management Administration (WMA).

Administrative Waiver. A decision by the Director pursuant to this regulation to allow the construction of a development to be governed by the stormwater management ordinance in effect as of May 4, 2009, in the County where the project will be located.

Adverse Impact. Any deleterious effect on waters or wetlands, including their quality, quantity, surface area, species composition, aesthetics or usefulness for human or natural uses which are or may potentially be harmful or injurious to human health, welfare, safety or property, to biological productivity, diversity, or stability or which unreasonably interfere with the enjoyment of life, property, and including outdoor recreation.

Agricultural Land Management Practices. Those methods and procedures used in the cultivation of land in order to further crop and livestock production and conservation of related soil and water resources.

Alternative Practice. An environmental site design practice or technique or structural stormwater management measure that is not found in the Maryland Design Manual and is proposed during concept plan approval. Alternative practices shall be designed to meet the criteria in the Maryland Design Manual, meet the minimum requirements specified in Section 32-178 of this Division and be approved by the Administration.

Applicant. Any person, agent, firm or governmental agency that executes the necessary forms to procure official approval of a project, or a permit to carry out the construction of a project.

Approval.

Aquifer. Porous water bearing geological formation generally restricted to materials capable of yielding an appreciable supply of water.

Best Management Practice (BMP). A structural device or nonstructural practice designed to temporarily store or treat stormwater runoff in order to mitigate flooding, reduce pollution, and provide other amenities.

Bioretention. A structural soil/plant device, source control, terrestrial base, filter/infiltrating device for managing stormwater runoff.

Channel Protection Storage Volume (Cpv). The volume used to design structural management practices to control stream channel erosion. Methods for calculating the channel protection storage volume are specified in the Maryland Design Manual and the Prince George's County Design Manual.

Chesapeake Bay Critical Area. All waters of and lands under the Chesapeake Bay and its tributaries to the head of tide as indicated on the State wetlands' maps; and all State and private wetlands designated under the Annotated Code of Maryland, Natural Resources Article, Title 9; and all land and water areas within one thousand (1,000) feet beyond the landward boundaries of State or private wetlands and heads of tide designated under the Annotated Code of Maryland, Natural Resources Article Title 9, as indicated on approved Chesapeake Bay Critical Area Overlay Zoning Map Amendments.

Clearing. The removal of trees and brush from land, but which does not include the ordinary mowing of grass.

Concept Plan. The first of three required plan approvals that includes the information necessary to allow an initial evaluation of a proposed project.

Conservation Agreement. A formal agreement that commits a grading or building permit applicant to the execution of various approved elements of a Conservation Plan, including a stormwater concept management plan, an approved sediment and erosion control plan, a vegetation management plan and other plans that may be required by the Department or the Prince George's County Planning Board.

Conservation Landscaping. A native plant landscape or intentional naturalization designed to provide climate resilient and ecosystem benefits including cooler surfaces, carbon sequestration, pollinator and wildlife support, reduced runoff and pollution, and healthy soils. Types of conservation landscapes and practices may include but not be limited to: Bayscapes, Stormwater Gardens, Urban Meadow, Landscape Restoration, Urban Soil Restoration, and Baywise Maintenance. All practices must incorporate low carbon methods. Soil restoration practices must include vertical composting into compacted soil, eroded soil, or urban fill to re-establish a healthy soil structure and biome.

Conservation Plan. A plan developed in accordance with Subtitle 5B, which demonstrates how a project has been designed to meet the specific Critical Area Commission criteria. The Conservation Plan consists of an approved stormwater management concept plan, an approved sediment and erosion control plan, a vegetation management plan, and such other plans relating to environmental systems as may be required by the Washington Suburban Sanitary Commission, the Maryland-National Capital Park and Planning Commission, the Prince George's County Health Department, the Department or the Prince George's Soil Conservation District.

County. Prince George's County, Maryland.

County Engineer. Department engineering staff.

Department. Department of Permitting, Inspections, and Enforcement.

Detention Structure. A permanent structure for the temporary storage of runoff designed so as not to create a permanent pool of water.

Develop Land. To change the runoff characteristics of a parcel of land in conjunction with residential, commercial, industrial, or institutional construction or alteration.

Development. Any man-made change to improved or unimproved real estate including, but not limited to, any construction, reconstruction, modification, extension or expansion of buildings or other structures, placement of fill or concrete, construction of new or replacement infrastructure, dumping, mining, dredging, grading, paving, drilling operations, storage of materials, land excavation, land clearing, land improvement, landfill operation, or any combination thereof.

Direct Discharge. The concentrated release of stormwater to tidal waters or vegetated tidal wetlands from new development or redevelopment projects in the Chesapeake Bay Critical Area.

Director. The Director of Permitting, Inspections, and Enforcement.

Drainage Area. The area contributing runoff to a study point measured in a horizontal plane enclosed by a ridge line.

Easement. A grant or reservation by the owner of land for the use of such land by others for a specific purpose or purposes, the use of which must be included in the conveyance of land affected by such easement.

Environmental Site Design (ESD). Using small scale stormwater management practices, nonstructural techniques, and better site planning to mimic natural hydrologic runoff characteristics and minimize the impact of land development on water resources. (Methods for designing ESD practices are specified in the Maryland Design Manual and the Prince George's County Design Manual).

Exemption. Those land development activities that are not subject to the stormwater management requirements contained in this Division.

Extended Detention. A stormwater design feature that provides gradual release of a volume of water in order to increase settling of pollutants and protect downstream channels from frequent storm events. (Methods for designing extended detention BMPs are specified in the Maryland Design Manual and the Prince George's County Design Manual).

Extreme Flood Volume (Qf). The storage volume required to control infrequent, but large storm events in which overbank flow reaches or exceeds the boundaries of the 100-year floodplain.

Filtration. The attenuation of stormwater runoff pollutants by plant and/or soil/sand complexes.

Final project approval. Approval of the final stormwater management plan and erosion and sediment control plan required to construct a project's stormwater management facilities that includes securing bonding or financing for final development plans if either is required as a prerequisite for approval.

Final Stormwater Management Plan. The last of the three required plan approvals that includes the information necessary to allow all approvals and permits to be issued by the Department.

Flow Attenuation. Prolonging the flow time of runoff to reduce the peak discharge.

Grading. Any act by which soil is disturbed, cleared, stripped, grubbed, excavated, scarified, filled or any combination thereof.

Impervious Area. An area that is covered with solid material or is compacted to the point where water cannot infiltrate underlying soils (e.g., parking lots, roads, houses, patios, swimming pools, compacted gravel areas, and so forth) and where natural hydrologic patterns are altered.

Infiltration. The passage or movement of water into the soil surface.

Maryland Design Manual. The latest edition of the 2000 Maryland Stormwater Design Manual, Volumes I and II, that serve as the State of Maryland's official guide for stormwater management principals, methods and practices.

Major Watersheds. The forty-two (42) watersheds identified in the watershed management plan for the purposes of identifying the preferred stormwater management approach within that major watershed.

Maximum Extent Practicable (MEP). Designing stormwater management systems so that all reasonable opportunities for using ESD planning techniques and treatment practices are exhausted and only where absolutely necessary, a structural BMP is implemented.

Natural Resource Inventory (NRI). A plan map and supporting documentation that provides all required information regarding the existing physical and environmental conditions on site and is approved by the Planning Director of the Maryland-National Capital Park and Planning Commission, or the Director's designee.

Off-Site Stormwater Management. The design and construction of a regional facility necessary to control stormwater from more than one development which is to be located outside the proposed area of development.

One Hundred (100) Year Floodplain. That area which would be inundated by a flood that has a one percent (1%) chance of being equaled or exceeded in any given year.

On-Site Stormwater Management. The design and construction of systems necessary to control stormwater within the proposed area of development.

Overbank Flood Protection Volume (Qp). The volume controlled by structural practices to prevent an increase in the frequency of out-of-bank flooding generated by development. (Methods for calculating the overbank flood protection volume are specified in the Maryland Design Manual and the Prince George's County Design Manual).

Permittee. The individual or corporation officer that signs the stormwater management permit and is legally responsible for all activities pertaining to the permit.

Person. The federal government, the State, any county, municipal corporation, or other political subdivision of the State, or any of their units, or an individual receiver, trustee, guardian, executor, administrator, fiduciary, or representative of any kind, or any partnership, firm, association, public or private corporation, or any other entity.

Planning Techniques. A combination of strategies employed early in project design to reduce the impact from development and to incorporate natural features into a stormwater management plan.

Pollutant. Sediment runoff due to erosion.

Pollution Trading. Program, process, policy to be implemented to reduce pollutants and to improve water quality and clean up the water body by addressing nutrients, sediments and other pollutants from a known source. This is intended to establish incentives for voluntary reductions of pollutants on an existing development with no known stormwater management in place. These pollution control devices are to be recorded through GIS watershed data base to be used for SWM banking.

Pond. Any stormwater management device that meets the category definition of MD 378-USDA Natural Resources Conservation Service: Conservation Standard Pond.

Preliminary Plan. The preliminary plan of subdivision submitted pursuant to the County's subdivision regulations.

Preliminary Project Approval. Approval of an Applicant's stormwater management concept plan, which includes:

Prince George's County Design Manual. The 2014 Prince George's County Stormwater Management Design Manual or any subsequent revisions that complements the Maryland Design Manual.

Recharge Volume (Rev). That portion of the water quality volume used to maintain groundwater recharge rates at development sites. (Methods for calculating the recharge volume are specified in the Maryland Design Manual and the Prince George's County Design Manual).

Redevelopment. Any construction, alteration or improvement performed on sites where existing land use is commercial, industrial, institutional, or multifamily residential and existing site impervious area within the limit of disturbance exceeds 40 percent.

Retention Structure. A permanent structure that provides for the storage of runoff and is designed to maintain a permanent pool of water.

Retrofitting. The implementation of ESD practices, the construction of structural BMP, or the modification of an existing structural BMP in a previously developed area to improve water quality over current conditions.

Sediment. Soils or other surficial materials transported or deposited by the action of wind, water, snow, ice or gravity as a product of erosion.

Site. For new development, any tract, lot, or parcel of land or combination of tracts, lots, parcels of land that are in one ownership or are contiguous and in diverse ownership, where development is to be performed as a part of a unit, subdivision or project.

Site Development Plan. The second of three required plan approvals that includes the information necessary to allow a detailed evaluation of a proposed project.

Stabilization. The prevention of soil movement by any of various vegetative and/or structural means.

Stormwater. Water that originates from a precipitation event.

Stormwater Management (SWM). Using ESD for the collection, conveyance, storage, treatment and disposal of stormwater runoff in a manner to prevent accelerated channel erosion, increased flood damage and/or degradation of water quality.

Stormwater Management Design Plan. The set of drawings and other documents that comprise all of the information and specifications for the systems, structures, concepts, and techniques that will be used to control stormwater as required by the approved concept plan and the Maryland Design Manual and the Prince George's County Design Manual.

Stormwater Management System. Natural areas, ESD practices, stormwater management measures, and any other structure through which stormwater flows, infiltrates or discharges from a site.

Stormwater Variance. The modification of the minimum stormwater management requirements for specific circumstances such that strict adherence to the requirements would result in unnecessary hardship and not fulfill the intent of this Division.

Stream Restoration. Restoration and reconstruction of existing waterways to maintain the ecological features of the stream, to mitigate stream bed incision and stream wall erosion, to preserve the capacity and to enhance the water quality of the stream. Stream restoration shall address the following including, but not limited to, intervention and installation of measures to repair damages to the stream corridors, hydrology, hydraulics, sediment transport, geomorphology, aquatic ecology, fisheries and riparian ecology.

Stripping. Any activity that removes the vegetation surface cover including tree removal, clearing, grubbing and storage or removal of topsoil.

Subdivision. The division of a lot, tract or parcel of land into two or more lots, plots, sites, parcels or other divisions by plat or deed.

Watercourse. Any natural or artificial stream, river, creek, ditch, channel, canal, conduit, culvert, drain, waterway, gully, ravine or wash, in and including any adjacent area that is subject to inundation from overflow or flood water.

Water Quality Volume (WQv). The volume needed to capture and treat 90 percent of the average annual rainfall at a development site. (Methods for calculating the water quality volume are specified in the Maryland Design Manual and the Prince George's County Design Manual.)

Watershed. The total drainage area contributing runoff to a single point.