Rhode Island Code of Regulations › Title 250 - Department of Environmental Management › Chapter 150 - Water Resources › Subchapter 10 - Wastewater And Storm Water › Part 8 - Stormwater Management, Design and Installation Rules › Section 250-RICR-150-10-8.5 - Definitions

Current through June 14, 2024
A. As used in these rules, the following
				  terms shall, where the context permits, be construed as follows:
1. "Approving agency" means an entity that
				  will enforce or require compliance with the minimum standards in this
				  Part.
2. "Aquatic bench" means a
				  10-15 foot wide bench which is located around the inside perimeter of a
				  permanent pool and is normally vegetated with aquatic plants; the goal is to
				  provide pollutant removal and enhance safety in areas using stormwater
				  ponds.
3. "Aquifer" means a porous
				  water-bearing formation of permeable rock, sand or gravel capable of yielding
				  economically significant quantities of groundwater.
4. "ASTM" means American Society of Testing
				  Materials.
5. "Baseflow" means the
				  portion of streamflow that is not due to storm runoff but is the result of
				  groundwater discharge or discharge from lakes or similar permanent impoundments
				  of water.
6. "Bioretention" means a
				  water quality practice that utilizes vegetation and soils to treat urban
				  stormwater runoff by collecting it in shallow depressions, before filtering
				  through an engineered bioretention planting soil media.
7. "BMP" means best management
				  practice.
8. "Buffer" means a
				  special type of preserved area along a watercourse or wetland where development
				  is restricted or prohibited. Buffers protect and physically separate a resource
				  from development. Buffers also provide stormwater control flood storage and
				  habitat values.
9. "Catch basin"
				  means a structure containing a sump placed below grade to conduct water from a
				  street or other paved surface to the storm sewer.
10. "Catch basin insert" means a structure,
				  such as a tray, basket, or bag that typically contains a pollutant removal
				  medium (filter media) and a method for suspending the structure in the catch
				  basin. They are placed directly inside of existing catch basins where
				  stormwater flows into the catch basin and is treated as it passes through the
				  structure.
11. "Channel" means a
				  natural stream that conveys water; a man-made ditch or swale excavated for the
				  flow of water.
12. "Channel
				  protection" or "CPv" means a design criterion which requires 24hour detention
				  of the 1-year, post-developed, 24-hour Type III storm event runoff volume for
				  the control of stream channel erosion.
13. "Channel stabilization" means erosion
				  prevention and stabilization of velocity distribution in a channel using
				  jetties, drops, revetments, structural linings, vegetation and other
				  measures.
14. "Check dams" means
				  small temporary dams constructed across a swale or drainage ditch to reduce the
				  velocity of concentrated stormwater flows.
15. "Cistern" means a container that stores
				  large quantities of rooftop stormwater runoff and may be located above or below
				  ground. Also see Rain Barrel.
16.
				  "Clay" means
a. A mineral soil separate
				  consisting of particles less than 0.002 millimeter in equivalent
				  diameter.
b. A soil texture
				  class.
c. (Engineering) A
				  fine-grained soil (more than 50% passing the No. 200 sieve) that has a high
				  plasticity index in relation to the liquid limit. (Unified Soil Classification
				  System).
17. "Combined
				  sewer overflows" or "CSOs" means combined sewers collect both stormwater runoff
				  and sanitary wastewater in a single set of sewer pipes. When combined sewers do
				  not have enough capacity to carry all the runoff and wastewater or the
				  receiving water pollution control plant cannot accept all the combined flow,
				  the combined wastewater overflows from the collection system into the nearest
				  body of water, creating a CSO.
18.
				  "Compaction" means any process by which the soil grains are rearranged to
				  decrease void space and bring them in closer contact with one another, thereby
				  increasing the weight of solid material per unit of volume, increasing the
				  shear and bearing strength and reducing permeability.
19. "Contour" means
a. An imaginary line on the surface of the
				  earth connecting points of the same elevation.
b. A line drawn on a map connecting points of
				  the same elevation.
20.
				  "CRMC" means Rhode Island Coastal Resources Management Council.
21. "Crushed stone" means gravel-sized
				  particles that pass through a 3-inch sieve and are retained on the No. 4 sieve,
				  and are angular in shape as produced by mechanical crushing. Crushed stone must
				  be washed in order to be used in stormwater BMPs to prevent clogging by
				  fines.
22. "Curve number" or "CN"
				  means a numerical representation of a given area's hydrologic soil group, plant
				  cover, impervious cover, interception and surface storage derived in accordance
				  with Natural Resources Conservation Service methods. This number is used to
				  convert rainfall volume into runoff volume.
23. "Cut" means a portion of land surface or
				  area from which earth has been removed or will be removed by excavation; the
				  depth below original ground surface to excavated surface.
24. "Darcy's law" means an equation stating
				  that the rate of fluid flow through a porous medium is proportional to the
				  potential energy gradient within the fluid. The constant of proportionality is
				  the hydraulic conductivity, which is a property of both the porous medium and
				  the fluid moving through the porous medium. Sizing of filtering BMPs and dry
				  swales is based on this principle.
25. "Deep sump catch basins" means storm
				  drain inlets that typically include a grate or curb inlet and at least a
				  four-foot sump to capture trash, debris and some sediment and oil and grease.
				  Also known as an oil and grease catch basin.
26. "Deicers" means materials applied to
				  reduce icing on paved surfaces. These consist of salts and other formulated
				  materials that lower the melting point of ice, including sodium chloride,
				  calcium chloride, calcium magnesium acetate, and blended products consisting of
				  various combinations of sodium, calcium, magnesium, and chloride, as well as
				  other constituents.
27. "DEM" means
				  Rhode Island Department of Environmental Management.
28. "Design points" or "Points of analyses"
				  means common locations at a site where pre-development and post-development
				  conditions can be compared.
29.
				  "Design storm" means a precipitation event for which the capacity of a best
				  management practice is sized and designed. Design storms are expressed in terms
				  of Type III, 24-hour events (i.e., 1-year, 10-year, and 100-year
				  storms).
30. "Detention" means the
				  temporary storage of storm runoff in a BMP with the goals of controlling peak
				  discharge rates.
31. "Detention
				  structure" means a structure constructed for the purpose of temporary storage
				  of surface runoff and gradual release of stored water at controlled
				  rates.
32. "Disposal site" means a
				  structure, well, pit, pond, lagoon, impoundment, ditch, landfill or other place
				  or area, excluding ambient air or surface water, where uncontrolled oil or
				  hazardous material has come to be located as a result of any spilling, leaking,
				  pouring, ponding, emitting, emptying, discharging, injecting, escaping,
				  leaching, dumping, discarding or otherwise disposing of such oil or hazardous
				  material. Disposal sites are designated as LUHPPLs.
33. "Disturbed area" means an area in which
				  the natural vegetative soil cover has been removed or altered and, therefore,
				  is susceptible to erosion.
34.
				  "Diversion" means a channel with a supporting ridge on the lower side
				  constructed across the slope to divert water from areas where it is in excess
				  to sites where it can be used or disposed of safely. Diversions differ from
				  terraces in that they are individually designed.
35. "Downstream analysis" means calculation
				  of peak flows, velocities, and hydraulic effects at critical downstream
				  locations to ensure that proposed projects do not increase post-development
				  peak flows and velocities at these locations.
36. "Drainage" means the removal of excess
				  surface water or ground water from land by means of surface or subsurface
				  drains.
37. "Drainage area" or
				  "watershed" means all land and water area from which runoff may run to a common
				  (design) point.
38. "Dry extended
				  detention pond" or "dry pond" or "detention basin" means a stormwater basin
				  designed to capture, temporarily hold, and gradually release a volume of
				  stormwater runoff to attenuate and delay stormwater runoff peaks. Dry extended
				  detention ponds provide water quantity control (peak flow control and stream
				  channel protection) as opposed to water quality control.
39. "Dry swale" means an open drainage
				  channel explicitly designed to detain and promote the filtration of stormwater
				  runoff through an underlying fabricated soil media.
40. "Dry well" means small excavated pits or
				  trenches filled with aggregate that receive clean stormwater runoff primarily
				  from building rooftops. Dry wells function as infiltration systems to reduce
				  the quantity of runoff from a site. The use of dry wells is applicable for
				  small drainage areas with low sediment or pollutant loadings and where soils
				  are sufficiently permeable to allow reasonable rates of infiltration.
41. "Emergency spillway" means an open and/or
				  closed channel designed to safely discharge stormwater flows in excess of the
				  principal spillway capacity.
42.
				  "Erosion" means
a. The wearing away of the
				  land surface by running water, wind, ice, or other geological agents, including
				  such processes as gravitational creep.
b. Detachment and movement of soil or rock
				  fragments by water, wind, ice or gravity. The following terms are used to
				  describe different types of water erosion:
(1) Accelerated erosion - Erosion much more
				  rapid than normal, natural or geologic erosion, primarily as a result of the
				  influence of the activities of man or, in some cases, of other animals or
				  natural catastrophes that expose base surfaces.
(2) Gully erosion - The erosion process
				  whereby water accumulates in narrow channels and, over short periods, removes
				  the soil from this narrow area to considerable depths, ranging from 1 or 2 feet
				  to as much as 75 to 100 feet.
(3)
				  Rill erosion - An erosion process in which numerous small channels only several
				  inches deep are formed.
(4) Sheet
				  erosion - The spattering of small soil particles caused by the impact of
				  raindrops on wet soils. The loosened and spattered particles may or may not
				  subsequently be removed by surface runoff.
43. "Erosive velocities" means velocities of
				  water that are high enough to wear away the land surface. Exposed soil will
				  generally erode faster than stabilized soils. Erosive velocities will vary
				  according to the soil type, slope, structural, or vegetative stabilization used
				  to protect the soil.
44. "Exfilter"
				  means a conventional stormwater filter without an underdrain system. The
				  filtered volume ultimately infiltrates into the underlying soils.
45. "Extended detention" or "ED" means a
				  stormwater design feature that provides for the gradual release of a volume of
				  water over a 24- to 48-hour interval in order to increase settling of urban
				  pollutants and protect downstream channels from frequent storm
				  events.
46. "Filter strip" means a
				  strip of permanent vegetation to treat sheet flow from adjacent impervious
				  areas by causing deposition of transported material, thereby reducing sediment
				  flow.
47. "Filtering practices"
				  means practices that capture and store stormwater runoff and pass it through a
				  filtering media such as sand, organic material, or the native soil for
				  pollutant removal. Stormwater filters are primarily water quality control
				  devices designed to remove particulate pollutants and, to a lesser degree,
				  bacteria and nutrients. Filtering systems include sand filters, organic
				  filters, bioretention, and tree filters.
48. "Floodplain" means areas adjacent to a
				  stream or river that are subject to flooding or inundation during a storm event
				  that occurs, on average, once every 100 years (or has a likelihood of
				  occurrence of 1/100 in any given year).
49. "Flow splitter" means an engineered,
				  hydraulic structure designed to divert a percentage of storm flow to a BMP
				  located out of the primary channel, or to direct stormwater to a parallel pipe
				  system, or to bypass a portion of baseflow around a BMP.
50. "Forebay" means a storage space located
				  near a stormwater BMP inlet that serves to trap incoming coarse sediments
				  before they accumulate in the main treatment area.
51. "Grade" means
a. The slope of a road, channel or natural
				  ground.
b. The finished surface of
				  a canal bed, roadbed, top of embankment, or bottom of excavation; any surface
				  prepared for the support of construction, like paving or laying a
				  conduit.
c. To finish the surface
				  of a canal bed, roadbed, top of embankment or bottom of excavation.
52. "Grass channels" means
				  traditional vegetated open channels, typically trapezoidal, triangular, or
				  parabolic in shape, whose primary function is to provide non-erosive
				  conveyance, typically up to the 10-year frequency design flow. They provide
				  limited pollutant removal through filtration by grass or other vegetation,
				  sedimentation, biological activity in the grass/soil media, as well as limited
				  infiltration if underlying soils are pervious.
53. "Gravel" means
a. "Pea" gravel is an aggregate consisting of
				  mixed sizes of 1/4-inch to 3/4-inch particles that normally occur in or near
				  old streambeds and have been worn smooth by the action of water. Pea gravel is
				  often used as a filter layer in stormwater BMPs.
b. According to the Unified Soil
				  Classification System, gravel is a soil having particle sizes that pass through
				  a 3-inch sieve and are retained on the No. 4 sieve; may be angular in shape as
				  produced by mechanical crushing. Also referred to as "crushed stone." Crushed
				  stone can be used as a media for stormwater best management
				  practices.
c. Type of impervious
				  surface when used for road, driveway, or parking surfaces.
54. "Gravel WVTS" means a wet vegetated
				  treatment system that maintains a saturated gravel bed and provides treatment
				  by stormwater movement through the gravel bed and plant/soil treatment
				  processes.
55. "Green roofs" means
				  multilayered, constructed roof systems consisting of a vegetative layer, media,
				  a geotextile layer, and a synthetic drain layer installed on building rooftops.
				  Rainwater is either intercepted by vegetation and evaporated to the atmosphere
				  or retained in the substrate before being returned to the atmosphere through
				  transpiration and evaporation.
56.
				  "Ground cover" means plants that are low growing and provide a thick growth
				  that protects the soil as well as providing some beautification of the area
				  occupied.
57. "Groundwater
				  recharge" means the process by which water that seeps into the ground,
				  eventually replenishing groundwater aquifers and surface waters such as lakes,
				  streams, and the oceans. This process helps maintain water flow in streams and
				  wetlands and preserves water table levels that support drinking water
				  supplies.
58. "Groundwater recharge
				  volume" or "Rev" means the post-development design recharge volume (on a storm
				  event basis) required to minimize the loss of annual pre-development
				  groundwater recharge. The Rev is determined as a function of annual
				  pre-development recharge for site-specific soils or surficial materials,
				  average annual rainfall volume, and amount of impervious cover on a
				  site.
59. "Gully" means a channel
				  or miniature valley cut by concentrated runoff through which water commonly
				  flows only during and immediately after heavy rains. The distinction between
				  gully and rill is one of depth. A gully is sufficiently deep that it would not
				  be obliterated by normal tillage operations, whereas a rill is of lesser depth
				  and would be smoothed by ordinary farm tillage.
60. "Hazard classification" for dams means a
				  rating for a dam that relates to the probable consequences of failure or
				  misoperation of the dam, which is a determination made by the DEM Director
				  based on an assessment of loss of human life, damages to properties or
				  structures located downstream of the reservoir, or loss of use as a drinking
				  water supply. A higher hazard dam does not imply that it is more likely to fail
				  or be misoperated than a lower hazard dam.
61. "Head" or "Hydraulics" means
a. The height of water above any plane of
				  reference.
b. The energy, either
				  kinetic or potential, possessed by each unit weight of a liquid expressed as
				  the vertical height through which a unit weight would have to fall to release
				  the average energy possessed. Used in various terms such as pressure head,
				  velocity head, and head loss.
62. "Herbaceous perennial" means a plant
				  whose stems die back to the ground each year.
63. "Hydrodynamic separators" means a group
				  of stormwater treatment technologies designed to remove large particle total
				  suspended solids and large oil droplets, consisting primarily of
				  cylindrical-shaped devices that are designed to fit in or adjacent to existing
				  stormwater drainage systems. The most common mechanism used in these devices is
				  vortex-enhanced sedimentation, where stormwater enters as tangential inlet flow
				  into the side of the cylindrical structure. As the stormwater spirals through
				  the chamber, the swirling motion causes the sediments to settle by gravity,
				  removing them from the stormwater.
64. "Hydrograph" means a graph showing
				  variation in depth or discharge of a stream of water over a period of
				  time.
65. "Hydrologic cycle" means
				  the distribution and movement of water between the earth's atmosphere, land,
				  and water bodies.
66. "Hydrologic
				  soil group" or "HSG" means a Natural Resource Conservation Service
				  classification system in which soils are categorized into four runoff potential
				  groups. The groups range from A soils, with high permeability and little runoff
				  production, to D soils, which have low permeability rates and produce much more
				  runoff.
67. "Illicit discharges"
				  means unpermitted discharges to waters of the state that do not consist
				  entirely of stormwater or uncontaminated groundwater except certain discharges
				  identified in the RIPDES Phase II Stormwater General Permit.
68. "Impaired waters" means those waterbodies
				  not meeting water quality standards. Pursuant to Section 303(d) of the federal
				  Clean Water Act, 33 U.S.C.
				  §
												1313 (2018), each state prepares a
				  list of impaired waters (known as the 303(d) list) which is presented in the
				  state's Integrated Water Report as Category 5 waters. Those impaired waters for
				  which a TMDL has been approved by US EPA and is not otherwise impaired, are
				  listed in Category 4A.
69.
				  "Impervious cover" or "I" means those surfaces that cannot effectively
				  infiltrate rainfall consisting of surfaces such as building rooftops, pavement,
				  sidewalks, driveways, compacted gravel.
70. "Infill" means a development site that
				  meets all of the following: the site is currently predominately pervious (less
				  than 10,000 square feet of existing impervious cover); it is surrounded (on at
				  least 3 sides) by existing development (not including roadways); the site is
				  served by a network of existing infrastructure and does not require the
				  extension of utility lines or new public road construction to serve the
				  property; and the site is 1 acre or less where the existing land use is
				  commercial, industrial, institutional, governmental, recreational, or
				  multifamily residential.
71.
				  "Infiltration practices" means stormwater treatment practices designed to
				  capture stormwater runoff and infiltrate it into the ground over a period of
				  days.
72. "Infiltration rate" means
				  the rate at which stormwater percolates into the subsoil measured in inches per
				  hour.
73. "Land use with higher
				  potential pollutant load" or "LUHPPL" means area where the land use has the
				  potential to generate highly contaminated runoff, with concentrations of
				  pollutants in excess of those typically found in stormwater.
74. "Landfill" means a facility or part of a
				  facility established in accordance with a valid site assignment for the
				  disposal of solid waste into or on land. Landfills are designated as
				  LUHPPLs.
75. "Level spreader" means
				  a device for distributing stormwater uniformly over the ground surface as sheet
				  flow to prevent concentrated, erosive flows and promote infiltration.
76. "Limit of disturbance" means a line
				  delineating the boundary of the area to be disturbed during a development or
				  redevelopment project. Area outside this boundary shall not be
				  touched.
77. "Low impact
				  development" or "LID" means a site planning and design strategy intended to
				  maintain or replicate predevelopment hydrology through the use of site
				  planning, source control, and small-scale practices integrated throughout the
				  site to prevent, infiltrate and manage runoff as close to its source as
				  possible.
78. "Maximum extent
				  practicable" means to show that a proposed development has met a standard to
				  the maximum extent practicable, the applicant must demonstrate the following:
a. All reasonable efforts have been made to
				  meet the standard in accordance with current local, state, and federal
				  regulations,
b. A complete
				  evaluation of all possible management measures has been performed,
				  and
c. If full compliance cannot be
				  achieved, the highest practicable level of management is being
				  implemented.
79. "Mulch"
				  means a natural or artificial protective layer of suitable materials, usually
				  of organic matter such as wood chips, leaves, straw, or peat, placed around
				  plants that aids in soil stabilization, soil moisture conservation, prevention
				  of freezing, and control of weeds. In addition, mulches serve as soil
				  amendments upon decomposition (for organic mulches).
80. "Native plants" means plants that are
				  adapted to the local soil and rainfall conditions and that require minimal
				  watering, fertilizer, and pesticide application.
81. "Non-structural controls" means pollution
				  control techniques, such as management actions and behavior modification that
				  do not involve the construction or installation of devices.
82. "Off-line" means a stormwater management
				  system designed to manage small storm events by diverting a percentage of
				  stormwater flow away from the storm drainage system. Flow from large storm
				  events will bypass this stormwater management system.
83. "Oil separators" or "Particle separators"
				  means a device consisting of 1 or more chambers designed to remove trash and
				  debris and to promote sedimentation of coarse materials and separation of free
				  oil (as opposed to emulsified or dissolved oil) from stormwater runoff.
				  Oil/particle separators are typically designed as off-line systems for
				  pretreatment of runoff from small impervious areas, and therefore provide
				  minimal attenuation of flow. Also called oil/grit separators, water quality
				  inlets, and oil/water separators.
84. "On-line" means a stormwater management
				  system designed to manage stormwater in its original drainage channel or pipe
				  network such that all stormwater flow will be directed to and through the
				  stormwater management system.
85.
				  "Open channels" or "Swales" or "Grass channels" means systems that are used for
				  the conveyance, retention, infiltration and filtration of stormwater
				  runoff.
86. "Outfall" means the
				  point where water flows from a conduit, stream, or drain.
87. "Outlet" means the point at which water
				  discharges from stormwater practices such as pipes or channels.
88. "Outlet control structure" means a
				  hydraulic structure placed at the outlet of a channel, spillway, pond, etc.,
				  for the purpose of dissipating energy, providing a transition to the channel or
				  pipe downstream, while achieving the discharge rates for specified
				  designs.
89. "OWTS" means onsite
				  wastewater treatment system.
90.
				  "Peak discharge rate" means the maximum instantaneous rate of flow during a
				  storm, usually in reference to a specific design storm event.
91. "Peak flow control" means criteria
				  intended to address increases in the frequency and magnitude of a range of
				  potential flood conditions resulting from development and include stream
				  channel protection, conveyance protection, peak runoff attenuation, and
				  emergency outlet sizing.
92.
				  "Performance monitoring" means collection of data on the effectiveness of
				  individual stormwater treatment practices.
93. "Permanent pool" or "Wet pool" means an
				  area of a stormwater management practice that has a fixed water surface
				  elevation due to a manipulation of the outlet structure.
94. "Permeability" means the rate of water
				  movement through the soil column under saturated conditions.
95. "Permeable paving materials" means
				  materials that are alternatives to conventional pavement surfaces and are
				  designed to increase infiltration and reduce stormwater runoff and pollutant
				  loads. Alternative materials include porous asphalt, pervious concrete, and
				  various pavers and open-celled grids.
96. "Piping" means removal of soil material
				  through subsurface flow channels or "pipes" developed by seepage
				  water.
97. "Plugs" means pieces of
				  vegetation, usually cut with a round tube, which can be used to propagate the
				  plant by vegetative means.
98.
				  "Point source" means any discernible, confined and discrete conveyance,
				  including but not limited to, any pipe, ditch, channel, tunnel, conduit, well,
				  discrete fissure, container, rolling stock, concentrated animal feeding
				  operation, landfill leachate collection system, vessel or other floating craft
				  from which pollutants are or may be discharged.
99. "Pondscaping" means plantings around
				  stormwater ponds that emphasize native vegetative species to meet specific
				  design intentions. Species are selected for up to six zones in the basin and
				  its surrounding setback, based on their ability to tolerate inundation and/ or
				  soil saturation.
100.
				  "Pretreatment" means techniques employed in stormwater BMPs to provide storage
				  or filtering to help trap coarse materials before they enter the
				  system.
101. "Principal spillway"
				  means an open and/or closed channel designed to allow a normal range of
				  stormwater flows to discharge from an impoundment.
102. "Qualifying pervious area" or "QPA"
				  means the generally flat, natural or landscaped vegetated areas that are fully
				  stabilized and where discharge from impervious areas may be directed via sheet
				  flow in order to obtain a Stormwater Credit.
103. "QA" means quality assurance.
104. "QAP" means quality assurance
				  plan.
105. "QC" means quality
				  control.
106. "Rational equation"
				  means an empirical equation acceptable for estimating peak flow rates for small
				  urbanized drainage areas with short times of concentration, but not for
				  estimating runoff volume. The Rational Equation is Q=CiA; where Q = peak
				  discharge, C = rational Method runoff coefficient, i = rainfall intensity
				  (inches/hour); and A = drainage area (acres).
107. "Redevelopment" means any construction,
				  alteration, or improvement that disturbs a total of 10,000 square feet or more
				  of existing impervious area where the existing land use is commercial,
				  industrial, institutional, governmental, recreational, or multifamily
				  residential.
108. "Responsible
				  authority" means authority responsible for long-term maintenance of stormwater
				  BMPs.
109. "Retention" means the
				  amount of precipitation on a drainage area that does not escape as runoff. It
				  is the difference between total precipitation and total runoff.
110. "Right of way" or "ROW" means right of
				  passage, as over another's property. A route that is lawful to use. A strip of
				  land acquired for transport or utility construction.
111. "RIPDES" means Rhode Island Pollutant
				  Discharge Elimination System.
112.
				  "Riser" means a type of outlet control structure that consists of a vertical
				  pipe that extends from the bottom of a pond BMP and houses the control devices
				  (weirs/orifices) to achieve the discharge rates for specified
				  designs.
113. "Runoff" means the
				  water from rain, snowmelt, or irrigation that flows over the land surface and
				  is not absorbed into the ground, instead flowing into surface waters or land
				  depressions.
114. "Safety bench"
				  means a flat area above the permanent pool and surrounding a stormwater basin
				  designed to provide a separation from the basin pool and adjacent
				  slopes.
115. "Sand" means
a. (Agronomy) A soil particle between 0.05
				  and 2.0 millimeters in diameter.
b.
				  A soil textural class.
c.
				  (Engineering) According to the Unified Soil Classification System, a soil
				  particle larger than the No. 200 sieve (0.074mm) and passing the No. 4 sieve
				  (approximately 1/4 inch).
116. "SARA 312 generator" means a facility
				  that is required by the Emergency Planning and Community Right to Know Act,
				  42 U.S.C §
												116 also known as Title III of the Superfund
				  Amendments and Reauthorization Act of 1989 (SARA Title III), to submit an
				  inventory of the location of hazardous chemicals which are located at the site.
				  SARA 312 generators are designated as LUHPPLs.
117. "Seasonal high groundwater table" or
				  "SHGT" means the elevation of the groundwater table during that time of the
				  year at which it is highest as determined by direct observation or by
				  interpretation of hydromorphic features in the soil profile.
118. "Sediment" means solid material, both
				  mineral and organic, that is in suspension, is being transported, or has been
				  moved from its site of origin by air, water, gravity, or ice and has come to
				  rest on the earth's surface either above or below sea level.
119. "Sediment chamber" or "forebay" means an
				  underground chamber or surface impoundment designed to remove sediment and/or
				  floatables prior to a primary or other secondary stormwater treatment
				  practice.
120. "Seepage" means
a. Water escaping through or emerging from
				  the ground.
b. The process by which
				  water percolates through the soil.
121. "SESC" means soil erosion and sediment
				  control.
122. "Setbacks" means the
				  minimum distance requirements for location of a structural BMP in relation to
				  roads, wells, septic fields, and other structures. Also, the area immediately
				  surrounding a best management practice that provides a separation barrier to
				  adjacent development and acts as filter to remove pollutants and provide
				  infiltration of stormwater prior to reaching the BMP.
123. "Shallow WVTS" means a wet vegetated
				  treatment system that consists of aquatic vegetation within a permanent pool
				  ranging in depth from 6" to 18" during normal conditions that is equivalent to
				  the entire WQv and provides treatment via settling and plant/soil treatment
				  processes.
124. "Sheet flow" means
				  water, usually storm runoff, flowing in a thin layer over the ground
				  surface.
125. "Side slopes" means
				  the slope of the sides of a channel, dam or embankment. It is customary to name
				  the horizontal distance first, as 1.5 to 1, or frequently, 1 1/2: 1, meaning a
				  horizontal distance of 1.5 feet to 1 foot vertical.
126. "Silt" means
a. (Agronomy) A soil separate consisting of
				  particles between 0.05 and 0.002 millimeter in equivalent diameter.
b. A soil textural class.
c. (Engineering) According to the Unified
				  Soil Classification System a fine-grained soil (more than 50% passing the No.
				  200 sieve) that has a low plasticity index in relation to the liquid
				  limit.
127. "Site" means
				  1 or more lots, tracts, or parcels of land to be developed or redeveloped for a
				  complex of uses, units or structures, including but not limited to commercial,
				  residential, institutional, governmental, recreational, open space, and/or
				  mixed uses. When calculating site size, jurisdictional wetland areas defined by
				  DEM or CRMC regulations and undeveloped lands protected by conservation
				  easements should be subtracted from the total site area.
128. "Site planning and design strategies"
				  means techniques of planning, engineering, and landscape design that maintain
				  predevelopment hydrologic functions and pollutant removal mechanisms to the
				  extent practical.
129. "Soil test"
				  means a chemical analysis of soil to determine needs for fertilizers or
				  amendments for species of plant being grown.
130. "Source control" means practices to
				  limit the generation of stormwater pollutants at their source.
131. "Stabilization" means providing adequate
				  measures, vegetative and/or structural, that will prevent erosion from
				  occurring.
132. "Stormwater" means
				  water consisting of precipitation runoff or snowmelt.
133. "Stormwater basin" means a land
				  depression or impoundment created for the detention or retention of stormwater
				  runoff.
134. "Stormwater filter"
				  means a stormwater treatment method that utilizes an artificial media to filter
				  out pollutants entrained in urban runoff.
135. "Stormwater management plan" means a
				  plan describing the proposed methods and measures to prevent or minimize water
				  quality and quantity impacts associated with a development project both during
				  and after construction. It identifies selected LID source controls and
				  treatment practices to address those potential impacts, the engineering design
				  of the treatment practices, and maintenance requirements for proper performance
				  of the selected practices.
136.
				  "Stormwater pollution prevention plan" or "SWPPP" means a plan that identifies
				  potential sources of pollution and outlines specific management activities
				  designed to minimize the introduction of pollutants into stormwater.
137. "Stormwater retrofits" means
				  modifications to existing development to incorporate source controls and
				  structural stormwater treatment practices to remedy problems associated with
				  and improve water quality mitigation functions of older, poorly designed, or
				  poorly maintained stormwater management systems.
138. "Stormwater treatment train" means
				  stormwater treatment practices, as well as site planning techniques and source
				  controls, combined in series to enhance pollutant removal or achieve multiple
				  stormwater objectives.
139. "Stream
				  buffers" means zones of variable width that are located along both sides of a
				  stream and are designed to provide a protective natural area along a stream
				  corridor.
140. "Stream order" means
				  the relative size of a stream based on Strahler's (1957) method. Streams with
				  no tributaries are first-order streams, represented as the start of a solid
				  line on a 1:24,000 USGS Quadrangle Sheet. A second-order stream is formed at
				  the confluence of two first-order streams. However, if a first-order stream
				  joins a second-order stream, it remains a second-order stream; it is not until
				  a second-order stream combines with another second-order stream that it becomes
				  a third-order stream, and so on. Peak flow controls (CPv and Qp) are waived for
				  discharges to fourth-order and larger streams.
141. "Street sweeper" means equipment that
				  removes particulate debris from roadways and parking lots. Includes mechanical
				  broom sweepers, vacuum sweepers, regenerative air sweepers, and dry vacuum
				  sweepers.
142. "Structural BMPs"
				  means devices that are constructed to manage stormwater runoff.
143. "Subgrade" means the soil prepared and
				  compacted to support a structure or a pavement system.
144. "Subwatershed" means the area draining
				  to the point of confluence between two first-order tributaries.
145. "Technical Release No. 55" or "TR-55"
				  means a watershed hydrology model developed by the US Soil Conservation Service
				  (now US Natural Resources Conservation Service) used to calculate runoff
				  volumes and provide a simplified routing for storm events through
				  ponds.
146. "Time of concentration"
				  means time required for water to flow from the most remote point of a drainage
				  area, in a hydraulic sense, to the point of analysis.
147. "Toe of slope" means where the slope
				  stops or levels out. Bottom of the slope.
148. "Token spillways" or "emergency
				  spillways" means spillways that are placed above the water elevation of the
				  largest managed storm and are required if not already provided as part of the
				  conveyance of the 100-year storm event.
149. "Topsoil" means fertile or desirable
				  soil material used to top dress road banks, subsoils, parent material,
				  etc.
150. "Total maximum daily
				  load" or "TMDL" means a calculation of the maximum amount of a pollutant that a
				  water body can receive and still meet water quality standards, and an
				  allocation of that amount to the pollutant's sources, including a margin of
				  safety.
151. "Total nitrogen" or
				  "TN" means the sum of total Kjeldahl nitrogen, nitrate, and nitrite. Nitrogen
				  is typically the growth-limiting nutrient in estuarine and marine
				  systems.
152. "Total phosphorus" or
				  "TP" means sum of orthophosphate, metaphosphate (or polyphosphate) and
				  organically bound phosphate. Phosphorus is typically the growth-limiting
				  nutrient in freshwater systems.
153. "Total suspended solids" or "TSS" means
				  the total amount of soils particulate matter that is suspended in the water
				  column.
154. "Trash rack" means a
				  grill, grate, or other device at the intake of a channel, pipe, drain or
				  spillway for the purpose of preventing oversized debris from entering the
				  structure and clogging the outlet weir/orifice.
155. "Tree filter" means a small bioretention
				  practice that may be contained in a concrete vault with an underdrain
				  connecting to the storm drain system, or may have an open base for infiltration
				  into the underlying soils.
156.
				  "Underground detention facilities" means vaults, pipes, tanks, and other
				  subsurface structures designed to temporarily store stormwater runoff for water
				  quantity control and to drain completely between runoff events. They are
				  intended to control peak flows, limit downstream flooding, and provide some
				  channel protection.
157.
				  "Underground infiltration systems" means structures designed to capture,
				  temporarily store, and infiltrate the water quality volume over several days,
				  including premanufactured pipes, vaults, and modular structures. Used as
				  alternatives to infiltration trenches and basins for space-limited sites and
				  stormwater retrofit applications.
158. "Urban stormwater runoff" means
				  stormwater runoff from developed areas.
159. "Velocity head" means the head due to
				  the velocity of a moving fluid, equal to the square of the mean velocity
				  divided by twice the acceleration due to gravity (32.16 feet per second per
				  second).
160. "Water balance" means
				  an equation describing the input, output, and storage of water in a watershed
				  or other hydrologic system.
161.
				  "Water quality flow" or "WQf" means the peak flow rate associated with the
				  water quality design storm or WQv.
162. "Water quality swales" means vegetated
				  open channels designed to treat and attenuate the water quality volume and
				  convey excess stormwater runoff. Dry swales are primarily designed to receive
				  drainage from small impervious areas and rural roads. Wet swales are primarily
				  used for highway runoff, small parking lots, rooftops, and pervious
				  areas.
163. "Water quality volume"
				  or "WQv" means the storage needed to capture and treat 90% of the average
				  annual stormwater runoff volume. In Rhode Island, this equates to 1-inch of
				  runoff from impervious surfaces.
164. "Watershed inches" means a measurement
				  used to compare stormwater volume requirements between sites of varying sizes.
				  Required volumes in acre-feet can be converted to watershed inches by dividing
				  by the total site area in acres and multiplying by 12 inches/feet.
165. "Wet swale" means an open drainage
				  channel or depression, explicitly designed to retain water or intercept
				  groundwater for water quality treatment.
166. "Wet vegetated treatment system" or
				  "WVTS" means shallow, constructed pools that capture stormwater and allow for
				  the growth of characteristic emergent vegetation. See also definition of
				  shallow WVTS and gravel WVTS.