Appendix A — Glossary

A

Arterial

A road or street primarily for through traffic. The term generally includes roads or streets considered collectors. It does not include local access roads which are generally limited to providing access to abutting property. See also RCW 35.78.010, RCW 36.86.070, and  RCW 47.05.021.

B

Bioengineering

The combination of biological, mechanical, and ecological concepts (and methods) to control erosion and stabilize soil through the use of vegetation or in combination with construction materials.

BMPs

Best Management Practices. See Chapter 12.08 KCC for definition.

C

CESCL

Certified Erosion and Sediment Control Lead. See Chapter 12.08 KCC for definition.

CMP

Corrugated metal pipe

Commercial agriculture

Those activities conducted on lands defined in RCW 84.34.020(2) and activities involved in the production of crops or livestock for commercial trade. An activity ceases to be considered commercial agriculture when the area on which it is conducted is proposed for conversion to a nonagricultural use or has lain idle for more than 5 years, unless the idle land is registered in a federal or state soils conservation program, or unless the activity is maintenance of irrigation ditches, laterals, canals, or drainage ditches related to an existing and ongoing agricultural activity.

Conveyance system

The drainage facilities, both natural and manmade, which collect, contain, and provide for the flow of surface and stormwater from the highest points on the land down to a receiving water. The natural elements of the conveyance system include swales and small drainage courses, streams, rivers, lakes, and wetlands. The human‑made elements of the conveyance system include gutters, ditches, pipes, channels, and most retention/detention facilities.

CPEP

Corrugated polyethylene pipe

D

Discharge point

The location where a discharge leaves the Permittee’s MS4 through the Permittee’s MS4 facilities/BMPs designed to infiltrate.

E

Effective impervious surface

Impervious surfaces that are connected by means of sheet flow or discrete conveyance to a drainage system or receiving body of water. Most impervious areas are effective. The Washington State Department of Ecology considers impervious areas in residential development to be ineffective if the runoff is dispersed through at least 100 feet of native vegetation using approved dispersion techniques.

Erodible or leachable materials

Wastes, chemicals, or other substances that measurably alter the physical or chemical characteristics of runoff when exposed to rainfall. Examples include erodible soils that are stockpiled, uncovered process wastes, manure, fertilizers, oily substances, ashes, kiln dust, and garbage dumpster leakage.

G

GSS

Green Stormwater Solutions. See definition for Low Impact Development (LID).

H

HDPE

High‑density polyethylene

HDPP

High‑density polyethylene pipe

Highway

A main public road connecting towns and cities.

K

KCC

Kitsap County Code.

L

LID

Low Impact Development. See Chapter 12.08 KCC for definition.

LID principles

Land use management strategies that emphasize conservation, use of onsite natural features, and site planning to minimize impervious surfaces, native vegetation loss, and stormwater runoff.

O

On-site stormwater management BMPs

As used in this manual, a synonym for Low Impact Development BMPs. See Chapter 12.08 KCC for definition.

Outfall

A point source as defined by 40 CFR 122.2 at the point where a discharge leaves the permittee’s MS4 and enters a surface receiving waterbody or surface receiving waters. Outfall does not include pipes, tunnels, or other conveyances which connect segments of the same stream or other surface waters and are used to convey primarily surface waters (i.e., culverts).

P

Permeable pavement

Pervious concrete, porous asphalt, permeable pavers or other forms of pervious or porous paving material intended to allow passage of water through the pavement section. It often includes an aggregate base that provides structural support and acts as a stormwater reservoir.

Pervious surface

Any surface material that allows stormwater to infiltrate into the ground. Examples include lawn, landscape, pasture, native vegetation areas, and permeable pavements.

PVC

Polyvinyl chloride

R

Rain garden

A non-engineered shallow landscaped depression, with compost‑amended native soils and adapted plants. The depression is designed to pond and temporarily store stormwater runoff from adjacent areas, and to allow stormwater to pass through the amended soil profile.

S

SDAP

Site Development Activity Permit

Steep slopes

Slopes of 30 percent gradient or steeper within a vertical elevation change of at least 10 feet. A slope is delineated by establishing its toe and top, and it is measured by averaging the inclination over at least 10 feet of vertical relief. For the purpose of this definition:

• The toe of a slope is a distinct topographic break in slope that separates slopes inclined at less than 30 percent from slopes 30 percent or steeper. Where no distinct break exists, the toe of a steep slope is the lower‑most limit of the area where the ground surface drops 10 feet or more vertically within a horizontal distance of 25 feet;

  AND

• The top of a slope is a distinct topographic break in slope that separates slopes inclined at less than 30 percent from slopes 30 percent or steeper. Where no distinct break exists, the top of a steep slope is the upper‑most limit of the area where the ground surface drops 10 feet or more vertically within a horizontal distance of 25 feet.

Strahler order

The number that is assigned to a stream to define the stream size based on a hierarchy of tributaries:

• The headwaters are the 1st order and downstream segments are defined at confluences (two streams running into each other).
• At a confluence, if the two streams are not of the same order, then the highest numbered order is maintained on the downstream segment.
• At a confluence of two streams with the same order, the downstream segment gets the next highest numbered order (e.g., two 1st order streams would be numbered 2nd order downstream).
• Divergences such as braided streams maintain the same order all the way through the braid, just like it was a single stream; however, divergences that are not braided streams keep the upstream order number and follow the normal hierarchy further downstream.

SWPE

Solid‑wall polyethylene

T

TDA

Threshold discharge area. An area within a project site draining to a single natural discharge location or multiple natural discharge locations that combine within one-quarter mile downstream (as determined by the shortest flowpath) The examples in Figure A.1 illustrate this definition. The purpose of this definition is to clarify how the thresholds of this manual are applied to project sites with multiple discharge points.

Figure A.1. Example TDA Delineations.

Treatment train

A combination of two or more treatment BMPs connected in series.

U

Underground Injection Control (UIC) well

A structure built to discharge fluids from the ground surface into the subsurface:

• A bored, drilled, or driven shaft whose depth is greater than the largest surface dimension.
• A dug hole whose depth is greater than the largest surface dimension.
• An improved sinkhole, which is a natural crevice that has been modified.
• A subsurface fluid distribution system that includes an assemblage of perforated pipes, drain tiles, or other similar mechanisms intended to distribute fluids below the surface of the ground.

Examples of UIC wells or subsurface infiltration systems include:

• drywells
• drain fields
• infiltration trenches with perforated pipe
• storm chamber systems with the intent to infiltrate
• French drains
• bioretention systems intended to distribute water to the subsurface by means of perforated pipe installed below the treatment soil
• other similar devices that discharge to the ground

V

Vegetated flow path

A vegetated flow path consists of well‑established lawn or pasture, landscaping with well‑established groundcover, native vegetation with natural groundcover, or an area that meets Post‑Construction Soil Quality and Depth (see Vol II–5.4.1 Post Construction Soil Quality and Depth). The groundcover shall be dense enough to help disperse and infiltrate flows and to prevent erosion.