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GLOSSARY North
Western Research Institute Stormwater - the “water that runs off surfaces such as rooftops, paved streets, highways, and parking lots. It can also come from hard, grassy surfaces including lawns, play fields, as well as graveled roads and parking lots.” Impervious
Surfaces - A hard surface
area which causes water to run off the surface in greater quantities or at
an increased rate of flow from the flow present under natural
conditions prior to development. Common impervious surfaces include,
but are not Land
disturbing activity
- Any activity that results in movement of earth, or a change in
the existing soil cover (both vegetative and nonvegetative) and/or the
existing soil topography. Land disturbing activities include, but are not
limited to clearing, grading, filling, and excavation. Compaction that is
associated with stabilization of structures and road construction shall
also be considered a land disturbing activity. Vegetation maintenance
practices are not considered land-disturbing activity. Native
vegetation
– Vegetation
comprised of plant species, other than noxious weeds, that are indigenous
to the coastal region of the Pacific Northwest and which reasonably could
have been expected to naturally occur on the site. Examples include trees
such as Douglas Fir, western hemlock, western red cedar, alder, big-leaf
maple, and vine maple; shrubs such as willow, elderberry, salmonberry, and
salal; and herbaceous plants such as sword fern, foam flower, and
fireweed. New
development -
Land disturbing
activities, including Class IV - general forest practices that are
conversions from timber land to other uses; structural development,
including construction or installation of a building or other structure;
creation of impervious surfaces; and subdivision, short subdivision and
binding site plans, as defined and applied in Chapter 58.17 RCW. Projects
meeting the definition of redevelopment shall not be considered new
development. Pollution-generating
impervious surface (PGIS) -
Those
impervious surfaces considered to be a significant source of pollutants in
stormwater runoff. Such surfaces include those which are subject to:
vehicular use; industrial activities (as further defined in the glossary);
or storage of erodible or leachable materials, wastes, or chemicals, and which
receive direct rainfall or the run-on or blow-in of rainfall. Erodible or
leachable materials, wastes, or chemicals are those substances which, when
exposed to rainfall, measurably alter the physical or chemical
characteristics of the rainfall runoff. Examples include
erodible soils that are stockpiled, uncovered process wastes, manure,
fertilizers, oily substances, ashes, kiln dust, and garbage dumpster
leakage. Metal roofs are also considered to be PGIS unless they are coated
with an inert, non-leachable material (e.g., baked-on enamel coating). A
surface, whether paved or not,
shall be considered subject to vehicular use if it is regularly used by
motor vehicles. The following are considered regularly-used surfaces:
roads, unvegetated road shoulders, bike lanes within the traveled lane of
a roadway, driveways, parking lots, unfenced fire lanes, vehicular
equipment storage yards, and airport runways. The
following are not considered regularly-used surfaces: paved
bicycle pathways separated from and not subject to drainage
from roads for motor vehicles, fenced firelanes, and infrequently used
maintenance access roads. Pollution-generating
pervious surfaces (PGPS) -
Any
nonimpervious surface subject to use of pesticides and fertilizers or loss
of soil. Typical PGPS include lawns, landscaped areas, golf courses,
parks, cemeteries, and sports fields. Pre-developed
condition – The native vegetation and soils that existed at a site
prior to the influence of Euro-American settlement. The predeveloped
condition shall be assumed to be a forested land cover unless reasonable,
historic information is provided that indicates the site was prairie prior
to settlement. Redevelopment
- On
a site that is already substantially developed (i.e., has 35% or more of
existing impervious surface coverage), the creation or addition of
impervious surfaces; the expansion of a building footprint or addition or
replacement of a structure; structural development
including construction, installation or expansion of a building or other
structure;; replacement of impervious surface that is not part of a
routine maintenance activity; and land disturbing activities. Best
Management Practices
are defined as schedules of activities, prohibitions of practices,
maintenance procedures, and structural and/or managerial practices, that
when used singly or in combination, prevent or reduce the release of
pollutants and other adverse impacts to waters of Washington State. The
types of BMPs are source control, treatment, and flow control. BMPs that
involve construction of engineered structures are often referred to as
facilities in this manual. For instance, the BMPs referenced in the menus
of Chapter 3 in Volume V are called treatment facilities. |