Code of Maryland Regulations › Title 26 - DEPARTMENT OF ENVIRONMENT › Part 3 - SUBTITLES 13-18 › Subtitle 17 - WATER MANAGEMENT › Chapter 26.17.02 - Stormwater Management › Section 26.17.02.02 - Definitions

Current through Register Vol. 51, No. 14, July 12, 2024
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.