“Adjustment” means a variation in the application of a minimum requirement to a particular project.

“Arterial” means 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, 36.86.070, and 47.05.021.

“Best management practice (BMP)” means the schedule of activities, prohibition of practices, maintenance procedures, and structural 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.

“Category 1 project site” means a project site subject to Minimum Requirements Nos. 1 through 5. See LMC 13.40.050.

“Category 2 project site” means a project site subject to Minimum Requirements Nos. 1 through 9. See LMC 13.40.050.

“Certified erosion and sediment control lead (CESCL)” means an individual who has current certification through an approved erosion and sediment control training program that meets the minimum training standards established by Ecology (see BMP C160: Certified Erosion and Sediment Control Lead in the Stormwater Management Manual for Western Washington). A CESCL is knowledgeable in the principles and practices of erosion and sediment control. The CESCL must have the skills to assess site conditions and construction activities that could impact the quality of stormwater and the effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges. Certification is obtained through an Ecology-approved erosion and sediment control course. Course listings are provided online at Ecology’s website.

“Chapter” means this chapter and any administrative rules and regulations adopted to implement this chapter.

“Construction stormwater pollution prevention plan (construction SWPPP)” means a document that describes the potential for pollution problems on a construction project and explains and illustrates the measures to be taken on the construction site to control those problems.

“Critical area” means the following areas:

“Department” means the Lynnwood public works department.

“Design storm” means that rainfall event or pattern of events which is selected by the public works department for use in analyzing and designing drainage facilities.

“Detention facilities” means facilities designed to hold runoff while gradually releasing it at a predetermined maximum rate.

“Developer” means the individual(s), corporation(s), or other legal entity submitting stormwater site plans as described in LMC 13.40.070.

“Director” means the Lynnwood public works director and/or the director’s designee.

“Drainage area” means the watershed contributing water runoff to and including the subject property.

“Drainage facilities” means any facilities installed or constructed in conjunction with a stormwater site plan for the purpose of flow control or runoff treatment.

“Ecology” means the Washington State Department of Ecology.

“Effective impervious surface” means those impervious surfaces that are connected via sheet flow or discrete conveyance to a drainage system. Impervious surfaces are considered ineffective if:

“Erodible or leachable materials” means 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.

“Exception” means relief from the application of a minimum requirement to a project.

“Exemption” means land uses and land-disturbing activities that are not required to follow the provisions of this chapter.

“Groundwater” means water in a saturated zone or stratum beneath the surface of the land or below a surface water body. Refer to Chapter 173-200 WAC.

“Hard surface” means an impervious surface, a permeable pavement, or a vegetated roof.

“Highway” means a main public road connecting towns and cities.

“Impervious surface” means a nonvegetated surface area which either prevents or retards the entry of water into the soil mantle as under natural conditions prior to development. A nonvegetated 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 limited to, roof tops, walkways, patios, driveways, parking lots or storage areas, concrete or asphalt paving, gravel roads, packed earthen materials, and oiled, macadam or other surfaces which similarly impede the natural infiltration of stormwater. Open, uncovered retention/detention facilities shall not be considered as impervious surfaces for purposes of determining whether the thresholds for application of minimum requirements are exceeded. Open, uncovered retention/detention facilities shall be considered impervious surfaces for purposes of runoff modeling.

“Land-disturbing activity” means any activity that results in 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, including landscape maintenance and gardening, are not considered land-disturbing activity. Stormwater facility maintenance is not considered land-disturbing activity if conducted according to established standards and procedures.

“LID best management practices (BMPs)” means distributed stormwater management practices, integrated into a project design, that emphasize predisturbance hydrologic processes of infiltration, filtration, storage, evaporation and transpiration. LID BMPs include, but are not limited to, bioretention, rain gardens, permeable pavements, roof downspout controls, dispersion, soil quality and depth, minimal excavation foundations, vegetated roofs, and water reuse.

“LID principles” means land use management strategies that emphasize conservation, use of on-site natural features, and site planning to minimize impervious surfaces, native vegetation loss, and stormwater runoff.

“Low impact development” is a stormwater and land use management strategy that strives to mimic predisturbance hydrologic processes of infiltration, filtration, storage, evaporation, and transpiration by emphasizing conservation, use of on-site natural features, site planning, and distributed stormwater management practices that are integrated into a project design.

“Maintenance” includes activities conducted on currently serviceable structures, facilities, and equipment that involves no expansion or use beyond that previously existing and results in no significant adverse hydrologic impact. It includes those usual activities taken to prevent a decline, lapse, or cessation in the use of structures and systems. Those usual activities may include replacement of dysfunctional facilities, including cases where environmental permits require replacing an existing structure with a different type structure, as long as the functioning characteristics of the original structure are not changed. One example is the replacement of a collapsed, fish blocking, round culvert with a new box culvert under the same span, or width, of roadway. In regard to stormwater facilities, maintenance includes assessment to ensure ongoing proper operation, removal of built-up pollutants (i.e., sediments), replacement of failed or failing treatment media, and other actions taken to correct defects as identified in the BMP design guidance within Volume V of the SWMMWW. See also Road Maintenance exemptions in LMC 13.40.030.

“Maximum extent practicable” refers to paragraph 402(p)(3)(B)(iii) of the federal Clean Water Act, which reads as follows: “[Permits for discharges from municipal storm sewers] shall require controls to reduce the discharge of pollutants to the maximum extent practicable, including management practices, control techniques, and system, design, and engineering methods, and other such provisions as the administrator or the state determines appropriate for the control of such pollutants.”

“Municipal separate storm sewer system (MS4)” means a conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, manmade channels, or storm drains):

“Native vegetation” means 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” includes 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 hard 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.

“New impervious surface” means a surface that is:

“Pervious surface” means any surface material that allows stormwater to infiltrate into the ground. Examples include lawn, landscape, pasture, native vegetation areas, and permeable pavements.

“Pollutant” means any substance which, when added to water, would contaminate or alter the chemical, physical, or biological properties of any waters of the state. This includes a change in temperature, taste, color, turbidity, or odor of the waters, or such discharge of any liquid, gaseous, solid, radioactive, or other substance into any waters of the state as will or is likely to create a nuisance. It also includes any substance which renders such waters harmful, detrimental, or injurious to the public health, safety, or welfare, or to domestic, commercial, industrial, agricultural, recreational, or other legitimate beneficial uses, or to livestock, wild animals, birds, fish, or other aquatic life.

“Pollution-generating hard surface” means those hard surfaces considered to be a significant source of pollutants in stormwater runoff. See the listing of surfaces under the pollution-generating impervious surface definition.

“Pollution-generating impervious surface (PGIS)” means those impervious surfaces considered to be a significant source of pollutants in stormwater runoff. Such surfaces include those which are subject to any of the following:

“Pollution-generating pervious surfaces (PGPS)” means any pervious surface subject to any of the following:

Typical PGPS include permeable pavement subject to vehicular use, lawns and landscaped areas including: golf courses, parks, cemeteries, and sports fields (natural and artificial turf).

“Project site” means that portion of a property, properties, or right-of-way subject to land-disturbing activities, new hard surfaces, or replaced hard surfaces.

“Redevelopment” on a site that is already substantially developed (i.e., has 35 percent or more of existing hard surface coverage) means the creation or addition of hard 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 hard surface that is not part of a routine maintenance activity; and land disturbing activities.

“Replaced hard surface” means the removal and replacement of hard surfaces down to the foundation for structures. For other hard surfaces, means the removal down to bare soil or base course and replacement.

“Replaced impervious surface” means the removal and replacement of impervious surfaces down to the foundation for structures. For other impervious surfaces, it means the removal down to bare soil or base course and replacement.

“Retention/detention facilities” means a type of drainage facility designed either to hold water for a considerable length of time and then release it by evaporation, plant transpiration, and/or infiltration into the ground; or to hold surface and stormwater runoff for a short period of time and then release it to the surface and stormwater management system.

“Site” means the area defined by the legal boundaries of a parcel or parcels of land that is (are) subject to new development or redevelopment. For road projects, the length of the project site and the right-of-way boundaries define the site.

“Source control BMP” means a structure or operation intended to prevent pollutants from coming into contact with stormwater through physical separation of areas or careful management of activities that are sources of pollutants. The Stormwater Management Manual for Western Washington separates source control BMPs into two types. Structural source control BMPs are physical, structural, or mechanical devices or facilities that are intended to prevent pollutants from entering stormwater. Operational source control BMPs are nonstructural practices that prevent or reduce pollutants from entering stormwater. See Volume IV of the Stormwater Management Manual for Western Washington for details.

“Storm drainage system” means publicly or privately owned facilities, including the city’s municipal separate storm sewer system, by which stormwater is collected and/or conveyed, including but not limited to any roads with drainage systems, municipal streets, gutters, curbs, inlets, piped storm drains, ditches and/or swales, pumping facilities, retention and detention basins, natural and human made or altered drainage channels, reservoirs, and other drainage structures.

“Stormwater” means runoff during and following precipitation and snowmelt events, including surface runoff, drainage, or interflow.

“Stormwater manual” means the Stormwater Management Manual for Western Washington prepared by the Washington State Department of Ecology. The city adopts the Stormwater Management Manual for Western Washington per the deadlines specified in the Western Washington Phase II Municipal Stormwater Permit.

“Stormwater site plan” means the comprehensive report containing all of the technical information and analysis necessary for regulatory agencies to evaluate a proposed development project for compliance with stormwater requirements. Contents of the stormwater site plan will vary with the type and size of the project, and individual site characteristics. It includes a construction stormwater pollution prevention plan (construction SWPPP) and a permanent stormwater control plan (PSC plan). Guidance on preparing a stormwater site plan is contained in the stormwater manual.

“Vehicular use” means regular use of an impervious or pervious surface by motor vehicles. The following are subject to regular vehicular use:

The following are not considered to be subject to regular vehicular use:

“Wetland” means areas that are inundated or saturated by surface water or groundwater at a frequency or duration sufficient to support, and under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soils conditions. Wetlands generally include swamps, marshes, bogs and similar areas. Wetlands do not include those artificial wetlands intentionally created from nonwetland sites, including, but not limited to, irrigation and drainage ditches, grass-lined swales, canals, detention facilities, wastewater treatment facilities, farm ponds, and landscape amenities, or those wetlands created after July 1, 1990, that were unintentionally created as a result of the construction of a road, street, or highway. Wetlands may include those artificial wetlands intentionally created from nonwetland areas to mitigate conversion of wetlands. (Ord. 3443 § 1, 2023; Ord. 2833 § 2, 2010)