26.17.02.02

.02 Definitions.

A. The following definitions describe the meaning of terms used in this chapter and the 2000 Maryland Stormwater Design Manual, Volumes I & II. The definitions will be valid unless the context in which they are used clearly requires a different meaning. Terms not defined below shall have the meanings given to them in the relevant statutes or, if not defined in statutes, the meanings attributed by common use. The definitions for these terms are provided below as a convenience, but persons affected by the Department's regulations should be aware that these definitions are subject to amendment by the General Assembly.

B. In this chapter, the following terms have the meanings indicated.

(1) "Administration" means the Water Management Administration.

(2) "Agricultural land management practices" means 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.

(3) "Approving agency" means the entity responsible for review and approval of stormwater management plans.

(4) "Aquifer" means a porous water-bearing geologic formation generally restricted to materials capable of yielding an appreciable supply of water.

(5) "Best management practice (BMP)" means 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.

(6) "Channel protection storage volume" means 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 2000 Maryland Stormwater Design Manual, Volumes I & II.

(7) "Concept plan" means the first of three required plan approvals that includes the information necessary to allow an initial evaluation of a proposed project.

(8) "Department" means the Department of the Environment.

(9) "Design Manual" means the 2000 Maryland Stormwater Design Manual, Volumes I & II, that serves as the official guide for stormwater management principles, methods, and practices.

(10) "Detention structure" means a permanent structure for the temporary storage of runoff which is designed so as not to create a permanent pool of water.

(11) "Develop land" means to change the runoff characteristics of a parcel of land in conjunction with residential, commercial, industrial, or institutional construction or alteration.

(12) "Direct discharge" means the concentrated release of stormwater to tidal waters or vegetated tidal wetlands from new development or redevelopment projects in the Critical Area.

(13) "Direct runoff" means the flow of rainwater, snowmelt, or spring flow over the land surface toward stream channels.

(14) "Drainage area" means that area contributing runoff to a single point measured in a horizontal plane, which is enclosed by a ridge line.

(15) Environmental Site Design.

(a) "Environmental site design (ESD)" means 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.

(b) "Environmental site design (ESD)" design methods are specified in the Design Manual.

(16) "Extended detention" means 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 Design Manual.

(17) "Extreme flood volume" means the storage volume required to control those infrequent but large storm events in which overbank flows reach or exceed the boundaries of the 100-year floodplain.

(18) "Final stormwater management plan" means the last of three required plan approvals that includes the information necessary to allow all approvals and permits to be issued by the appropriate authority.

(19) "Flow attenuation" means prolonging the flow time of runoff to reduce the peak discharge.

(20) "Impervious area" means any surface that does not allow stormwater to infiltrate into the ground.

(21) "Infiltration" means the passage or movement of water into the soil surface.

(22) "Maximum extent practicable (MEP)" means 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.

(23) "Off-site stormwater management" means the design and construction of a facility necessary to control stormwater from more than one development.

(24) "On-site stormwater management" means the design and construction of systems necessary to control stormwater within an immediate development.

(25) "Overbank flood protection volume" means 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 Design Manual.

(26) "Person" means 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.

(27) "Planning techniques" means a combination of strategies employed early in project design to reduce impact from development and to incorporate natural features into a stormwater management plan.

(28) "Recharge volume" means that portion of the water quality volume used to maintain ground water recharge rates at development sites. Methods for calculating the recharge volume are specified in the Design Manual.

(29) "Redevelopment" means any construction, alteration, or improvement performed on sites where existing land use is commercial, industrial, institutional, or multifamily residential and the existing site impervious area exceeds 40 percent.

(30) "Retention structure" means a permanent structure that provides for the storage of runoff by means of a permanent pool of water.

(31) "Retrofitting" means the construction of a structural BMP in a previously developed area, the modification of an existing structural BMP, or the implementation of a nonstructural practice to improve water quality over current conditions.

(32) "Sediment" means soils or other surficial materials transported or deposited by the action of wind, water, ice, or gravity as a product of erosion.

(33) "Site" means any tract, lot, 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 part of a unit, subdivision, or project.

(34) "Site development plan" means the second of three required plan approvals that includes the information necessary to allow a detailed evaluation of a proposed project.

(35) "Stormwater" means water that originates from a precipitation event.

(36) "Stormwater management" means, for:

(a) Quantitative control, a system of vegetative and structural measures that control the increased volume and rate of surface runoff caused by man-made changes to the land; and

(b) Qualitative control, a system of vegetative, structural, and other measures that reduce or eliminate pollutants that might otherwise be carried by surface runoff.

(37) "Stormwater Management Subtitle" means Environment Article, Title 4, Subtitle 2, Annotated Code of Maryland and cumulative supplement.

(38) "Stormwater management system" means natural areas, ESD practices, stormwater management measures, and any other structure through which stormwater flows, infiltrates, or discharges from a site.

(39) "Water quality volume" means the volume needed to capture and treat 90 percent of the average annual runoff volume at a development site. Methods for calculating the water quality volume are specified in the Design Manual.

(40) "Watershed" means the total drainage area contributing runoff to a single point.