The definitions of this chapter shall apply to this division and shall prevail over any conflicting definition in the Surface Water Design Manual, as defined in this chapter.
(Ord. 16-0428 § 4 (Att. C))
“Adjustment”
means a variation from the requirements of KMC § 13.35.050 and the Surface Water Design Manual approved by the city manager for a particular project in accordance with KMC § 13.35.050(C). The term “adjustment” replaces the term “variance,” which was used in prior editions of the Surface Water Design Manual.
(Ord. 16-0428 § 4 (Att. C))
“AKART”
means “all known, available, and reasonable methods of prevention, control, and treatment.” AKART represents the most current methodology that can be reasonably required for preventing, controlling, or abating the pollutants associated with a discharge. “AKART” applies to both point and nonpoint sources of pollution.
(Ord. 16-0428 § 4 (Att. C))
“Applicant”
means a property owner or a public agency or public or private utility which owns a right-of-way or other easement, or has been adjudicated the right to such an easement pursuant to RCW 8.12.090, or any person or entity designated or named in writing by the property or easement owner to be the applicant, in an application for a development proposal, permit or approval.
(Ord. 16-0428 § 4 (Att. C))
“Basin”
means a geographic area that contains or drains to a stream or river named or noted on common maps, such as Swamp Creek, or a geographic area that drains to a nonflowing water body named and noted on common maps, such as Lake Washington.
(Ord. 16-0428 § 4 (Att. C))
“Basin plan”
means a plan and all implementing regulations and procedures including, but not limited to, capital projects, public education activities and land use management adopted by ordinance for managing surface water and stormwater within individual subbasins.
(Ord. 16-0428 § 4 (Att. C))
“Construct or modify”
means to install a new drainage pipe or ditch or make improvements to an existing drainage pipe or ditch, for purposes other than maintenance, that either serves to concentrate previously unconcentrated surface water and stormwater runoff, or serves to increase, decrease and/or redirect the conveyance of surface water and stormwater runoff. “Construct or modify” does not include installation or maintenance of a driveway culvert installed as part of a single-family residential building permit.
(Ord. 16-0428 § 4 (Att. C))
“Conveyance system”
means the drainage facilities and features, both natural and constructed, which collect, contain and provide for the flow of surface water 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 constructed elements of the conveyance system include gutters, ditches, pipes, channels and most flow control and water quality treatment facilities.
(Ord. 16-0428 § 4 (Att. C))
“Developed parcel”
means any parcel altered from its native state by the construction, creation or addition of impervious or pervious surfaces, including the alteration of soil conditions, ground cover, and species of vegetation (such as landscaping).
(Ord. 16-0428 § 4 (Att. C))
“Development”
means any activity that requires a permit or approval, including, but not limited to, a building permit, grading permit, shoreline substantial development permit, conditional use permit, special use permit, zoning variance, zone reclassification, subdivision, short subdivision, binding site plan, site plan review or right-of-way use permit.
(Ord. 16-0428 § 4 (Att. C))
“Discharge”
means throw, drain, release, dump, spill, empty, emit, or pour forth any matter or to cause or allow matter to flow, run, or seep from land or be thrown, drained, released, dumped, spilled, emptied, emitted or poured into water.
(Ord. 16-0428 § 4 (Att. C))
“Drainage”
means the collection, conveyance, containment or discharge, or any combination thereof, of surface water and stormwater runoff.
(Ord. 16-0428 § 4 (Att. C))
“Drainage easement”
means a legal encumbrance that is placed against a property’s title to reserve specified privileges for the users and beneficiaries of the drainage facilities contained within the boundaries of the easement.
(Ord. 16-0428 § 4 (Att. C))
“Drainage facility”
means a constructed or engineered feature that collects, conveys, stores, treats, or otherwise manages stormwater runoff or surface water. “Drainage facility” includes, but is not limited to, a constructed or engineered stream, lake, wetland, or closed depression, or a pipe, channel, ditch, gutter, flow control facility, flow control BMP, water quality facility, erosion and sediment control facility, and any other structure and appurtenance that provides for drainage.
(Ord. 16-0428 § 4 (Att. C))
“Drainage review”
means an evaluation by the City staff of a proposed project's compliance with the drainage requirements in the Surface Water Design Manual. The types of drainage review include: simplified drainage review, targeted drainage review, directed drainage review, full drainage review and large project drainage review.
(Ord. 16-0428 § 4 (Att. C))
“Financial guarantee”
means a form of financial security posted to do one or more of the following: ensure timely and proper completion of improvements; ensure compliance with this code; or provide secured warranty of materials, workmanship of improvements and design. “Financial guarantee” includes assignments of funds, cash deposit, surety bonds or other forms of financial security acceptable to the city manager. “Performance guarantee,” “maintenance guarantee” and “defect guarantee” are considered subcategories of financial guarantee.
(Ord. 16-0428 § 4 (Att. C))
“Flow control BMP”
means a small-scale drainage facility or feature that is part of a development site strategy to use processes such as infiltration, dispersion, storage, evaporation, transpiration, forest retention, and reduced impervious surface footprint to mimic predeveloped hydrology and minimize stormwater runoff.
(Ord. 16-0428 § 4 (Att. C))
“Flow control BMP design and maintenance details”
means the diagrams/figures, design specifications, and maintenance instructions for each flow control BMP proposed on an individual site/lot that does not contain a flow control or water quality facility. These details are intended to be recordable to facilitate attachment to the declaration of covenant and grant of easement required for implementation of flow control BMPs on individual sites/lots. The City may waive all or a portion of this component if it determines there is no need to specify design details or maintenance instructions for certain proposed BMPs.
(Ord. 16-0428 § 4 (Att. C))
“Flow control BMP site plan (FCBMP site plan)”
means a scale drawing of an individual site/lot used to show how required flow control BMPs will be applied to the target surfaces of an individual site/lot that does not contain a flow control or water quality facility. The FCBMP site plan is intended to be a recordable document (or reducible to a recordable document) that can be attached to the declaration of covenant and grant of easement required for implementation of flow control BMPs on individual sites/lots. DPER may allow a written version of this plan if they determine there is no need to illustrate the size and location of proposed flow control BMPs.
(Ord. 16-0428 § 4 (Att. C))
“Flow control facility”
means a drainage facility designed to mitigate the impacts of increased surface water and stormwater runoff generated by site development pursuant to the drainage requirements in this division. Flow control facilities are 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 runoff for a short period of time and then release it to the conveyance system.
(Ord. 16-0428 § 4 (Att. C))
“Full drainage review”
means the evaluation required by KMC § 13.35.040 of a proposed project's compliance with the full range of core and special requirements in the Surface Water Design Manual. Full drainage review is required for any proposed project, unless the project is subject to simplified drainage review, targeted drainage review, directed drainage review, or large project drainage review that (A) would result in 2,000 square feet or more of new plus replaced impervious surface; or (B) would result in 7,000 square feet or more of land disturbing activity.
(Ord. 16-0428 § 4 (Att. C))
“Groundwater”
means all waters that exist beneath the land surface or beneath the bed of any stream, lake, or reservoir, or other body of surface water, whatever may be the geological formation or structure in which such water stands or flows, percolates or otherwise moves.
(Ord. 16-0428 § 4 (Att. C))
“High-use site”
means a commercial, industrial or street intersection site that generates a higher-than-average number of vehicle turnovers or has other characteristics that generate the potential for chronic oil accumulation. High-use sites include:
A. 
Commercial or industrial sites subject to:
1. 
An expected daily traffic count greater than 100 vehicles per 1,000 square feet of gross building area;
2. 
Petroleum storage or transfer in excess of 1,000 gallons per year, not including routine fuel oil storage or transfer; or
3. 
Use, storage or maintenance of a fleet of 25 or more diesel vehicles each weighing over 10 tons; or
B. 
Street intersections with average daily traffic counts of 25,000 vehicles or more on the main streetway and 15,000 or more vehicles on any intersecting streetway (excluding pedestrian or bicycle use improvement projects).
(Ord. 16-0428 § 4 (Att. C))
“Impervious surface”
means a hard surface area that either prevents or retards the entry of water into the soil mantle as under natural conditions before development; or that causes water to run off the surface in greater quantities or at an increased rate of flow compared to the flow present under natural conditions prior to development (see also “new impervious surface”). Common impervious surfaces include, but are not limited to, roofs, walkways, patios, driveways, parking lots, or storage areas, areas that are paved, graveled or made of packed or oiled earthen materials or other surfaces that similarly impede the natural infiltration of surface water or stormwater. For the purposes of applying the impervious surface thresholds and exemptions contained in the Surface Water Design Manual, permeable pavement, vegetated roofs, and pervious surfaces with underdrains designed to collect stormwater runoff are considered impervious surface while an open uncovered flow control or water quality facility is not. However, for the purposes of computing runoff, uncovered flow control or water quality facilities shall be modeled as impervious surfaces.
(Ord. 16-0428 § 4 (Att. C))
“Improvement”
means a permanent, human-made physical change to land or real property including, but not limited to, buildings, streets (with or without curbs or gutters), sidewalks, crosswalks, parking lots, water mains, sanitary and storm sewers, drainage facilities, and landscaping.
(Ord. 16-0428 § 4 (Att. C))
“Land disturbing activity”
means an activity that results in a change in the existing soil cover, both vegetative and nonvegetative, or to the existing soil topography. “Land disturbing activity” includes, but is not limited to, demolition, construction, clearing, grading, filling, excavation and compaction. “Land disturbing activity” does not include tilling conducted as part of agricultural practices, landscaping maintenance or gardening.
(Ord. 16-0428 § 4 (Att. C))
“Landslide hazard drainage area”
means an area tributary to a landslide hazard area (KMC § 18.20.1570) where the City has determined that overland flows from new projects will pose a significant threat to health and safety because of their close proximity to the landslide hazard area. A delineation of known landslide hazard areas can be found in the Kenmore Critical Areas - Geologic Hazard Areas Map (KMC § 18.55.130).
(Ord. 16-0428 § 4 (Att. C))
“LID best management practices” or “LID 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 are referred to as flow control BMPs in the Surface Water Design Manual and include, but are not limited to, bioretention, permeable pavements, limited infiltration systems, roof downspout controls, dispersion, soil quality and depth, and minimal excavation foundations.
(Ord. 16-0428 § 4 (Att. C))
“LID principles”
means land use management strategies that emphasize conservation, on-site natural features, and site planning to minimize impervious surfaces, native vegetation loss and stormwater runoff.
(Ord. 16-0428 § 4 (Att. C))
“Low impact development” or “LID”
means 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. Other common names for “LID” are “green stormwater infrastructure” or “natural drainage systems.”
(Ord. 16-0428 § 4 (Att. C))
“Maintenance”
means those usual activities taken to prevent a decline, lapse, or cessation in the use of currently serviceable structures, facilities, BMPs, equipment, or systems if there is no expansion of any of these, and there are no significant hydrologic impacts. Maintenance includes the repair or replacement of nonfunctional facilities and BMPs, and the replacement of existing structures with different types of structures, if the repair or replacement is required to meet current engineering standards or is required by one or more environmental permits and the functioning characteristics of the original facility or structure are not changed. For the purposes of applying this definition to the thresholds and requirements of this division, the city manager will determine whether the functioning characteristics of the original facility, structure, or BMP will remain sufficiently unchanged to consider replacement as maintenance. Drainage review is not required for projects proposing only maintenance.
(Ord. 16-0428 § 4 (Att. C))
“Municipal separate storm sewer system”
means a conveyance, or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, manmade channels, or storm drains):
A. 
Owned or operated by a state, city, town, borough, county, parish, district, association, or other public body (created by or pursuant to State law) having jurisdiction over disposal of wastes, stormwater, or other wastes, including special districts under State law such as a sewer district, flood control district or drainage district, or similar entity, or an Indian tribe or an authorized Indian tribal organization, or a designated and approved management agency under Section 208 of the Clean Water Act that discharges to waters of Washington State;
B. 
Designed or used for collecting or conveying stormwater;
C. 
Which is not a combined sewer;
D. 
Which is not part of a publicly owned treatment works as defined at 40 CFR 122.2; and
E. 
Which is defined as “large” or “medium” or “small” or otherwise designated by the Washington State Department of Ecology pursuant to 40 CFR 122.26.
(Ord. 16-0428 § 4 (Att. C))
“Native vegetated surface”
means a surface in which the soil conditions, ground cover, and species of vegetation are like those of the original native condition for the site. More specifically, this means (A) the soil is either undisturbed or has been treated according to the “native vegetated landscape” specifications in SWDM Appendix C, Section C.2.1.8; (B) the ground is either naturally covered with vegetation litter or has been topdressed between plants with four inches of mulch consistent with the native vegetated landscape specifications in SWDM Appendix C; and (C) the vegetation is either (1) comprised predominantly of plant species, other than noxious weeds, that are indigenous to the coastal region of the Pacific Northwest and that reasonably could have been expected to occur naturally on the site; or (2) comprised of plant species specified for a native vegetated landscape in SWDM Appendix C. Examples of these plant species include trees such as Douglas fir, western hemlock, western red cedar, alder, bigleaf maple and vine maple; shrubs such as willow, elderberry, salmonberry and salal; and herbaceous plants such as sword fern, foam flower, and fireweed.
(Ord. 16-0428 § 4 (Att. C))
“National Pollutant Discharge Elimination System”
means the national program for issuing, modifying, revoking, and reissuing, terminating, monitoring and enforcing permits, and imposing and enforcing pretreatment requirements, under Sections 307, 318, 402, and 405 of the Clean Water Act, for the discharge of pollutants to surface waters of the State from point sources. These permits are referred to as NPDES permits and, in Washington State, are administered by the Washington State Department of Ecology.
(Ord. 16-0428 § 4 (Att. C))
“New impervious surface”
means the addition of a hard or compacted surface such as roofs, pavement, gravel or dirt; or the addition of a more compacted surface, like paving over preexisting dirt or gravel. Permeable pavement and vegetated roofs are considered new impervious surface for purposes of determining whether the thresholds for application of minimum requirements are exceeded in the SWDM, as are lawns, landscaping, sports fields, golf courses, and other areas that have modified runoff characteristics resulting from the addition of underdrains designed to collect stormwater runoff. Open, uncovered retention/detention facilities shall not be considered impervious surfaces for purposes of determining whether the thresholds for application of minimum requirements in the SWDM are exceeded. Open, uncovered retention/detention facilities shall be considered impervious surfaces for purposes of runoff modeling.
(Ord. 16-0428 § 4 (Att. C))
“New pervious surface”
means the conversion of native vegetated surface or other native surface to a nonnative pervious surface (e.g., conversion of forest or meadow to pasture land, grass land, cultivated land, lawn, landscaping, bare soil, etc.) or any alteration of existing nonnative pervious surface that significantly increases surface water and stormwater runoff (e.g., conversion of pasture land, grass land, or cultivated land to lawn, landscaping or bare soil; or alteration of soil characteristics).
(Ord. 16-0428 § 4 (Att. C))
“Open space”
means any parcel, property or portion thereof classified for current use taxation under Chapter 84.34 RCW, or for which the development rights have been sold to the City. This definition includes lands which have been classified as open space, agricultural or timber lands under criteria contained in Chapter 84.34 RCW.
(Ord. 16-0428 § 4 (Att. C))
“Parcel”
means the smallest separately segregated unit or plot of land having an identified owner, boundaries and surface area which is documented for property tax purposes and given a tax lot number by the King County assessor.
(Ord. 16-0428 § 4 (Att. C))
“Permeable pavement”
means 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.
(Ord. 16-0428 § 4 (Att. C))
“Person”
means an individual, and his or her agent or assign, municipality, political subdivision, government agency, partnership, corporation, business, or any other entity.
(Ord. 16-0428 § 4 (Att. C))
“Pervious surface”
means any surface material that allows stormwater to infiltrate into the ground. Examples include lawn, landscape, pasture, and native vegetation areas. Note: for purposes of threshold determination and runoff volume modeling for detention and treatment in the SWDM, vegetated roofs and permeable pavements are to be considered impervious surfaces along with lawns, landscaping, sports fields, golf courses, and other areas that have modified runoff characteristics resulting from the addition of underdrains.
(Ord. 16-0428 § 4 (Att. C))
“Pollution-generating impervious surface (PGIS)”
means an impervious surface considered to be a significant source of pollutants in stormwater runoff. Such surfaces include those that are subject to: vehicular use, industrial activities, or storage of erodible or leachable materials, wastes, or chemicals; and that receive direct rainfall or the run-on or blow-in of rainfall. A covered parking area would be included if runoff from uphill could regularly run through it or if rainfall could regularly blow in and wet the pavement surface. PGIS includes metal roofs unless they are coated with an inert, nonleachable material (see SWDM Reference 11-E). PGIS includes roofs that are exposed to the venting of significant amounts of dusts, mists, or fumes from manufacturing, commercial, or other indoor activities. PGIS includes vegetated roofs exposed to pesticides, fertilizers, or loss of soil. Other roofing types that may pose risk but are not currently regulated are listed in the SWDM Reference 11-E. Lawns, landscaping, sports fields, golf courses, and other areas that have modified runoff characteristics resulting from the addition of underdrains that have the pollution-generating characteristics described under the “pollution-generating pervious surface” definition are also considered PGIS.
(Ord. 16-0428 § 4 (Att. C))
“Pollution-generating pervious surface (PGPS)”
means a nonimpervious surface considered to be a significant source of pollutants in surface water and stormwater runoff. Such surfaces include those that are subject to vehicular use, industrial activities, storage of erodible or leachable materials, wastes, or chemicals, and that receive direct rainfall or the run-on or blow-in of rainfall; or subject to use of pesticides and fertilizers, or loss of soil. Such surfaces include, but are not limited to, the lawn and landscaped areas of a residential, commercial, or industrial site or land use, golf courses, parks, sports fields (natural and artificial turf), cemeteries, and County-standard grassed modular grid pavement.
(Ord. 16-0428 § 4 (Att. C))
“Project site”
means the portion of a site and any off-site areas subject to proposed project activities, alterations and improvements including those required by this code.
(Ord. 16-0428 § 4 (Att. C))
“Rate category”
means the classification in this division given to a parcel in the City based upon the type of land use on the parcel and the percentage of impervious surface area contained on the parcel.
(Ord. 16-0428 § 4 (Att. C))
“Redevelopment project”
means a project that proposes to add, replace or modify impervious surface for purposes other than a residential subdivision or maintenance on a site that:
A. 
Is already substantially developed in a manner that is consistent with its current zoning or with a legal nonconforming use; or
B. 
Has an existing impervious surface coverage of 35 percent or more.
(Ord. 16-0428 § 4 (Att. C))
“Replaced impervious surface”
means any existing impervious surface on the project site that is proposed to be removed and reestablished as impervious surface, excluding impervious surface removed for the sole purpose of installing utilities or performing maintenance on underground infrastructure. For structures, “removed” means the removal of buildings down to the foundation. For other impervious surfaces, “removed” means the removal down to base course or bare soil. It does not include the removal of pavement material through grinding or other surface modification unless the entire layer of PCC or AC is removed. Replaced impervious surface also includes impervious surface that is moved from one location to another on the project site where the following two conditions are met: (A) the area from which the impervious surface is moved from will be restored to the same or better runoff discharge characteristics as the area being covered by the moved impervious surface, and (B) impervious surface at the new location is either designated as non-pollutiongenerating or the pollution-generating characteristics remain unchanged compared to that of the original location.
(Ord. 16-0428 § 4 (Att. C))
“Residence”
means a building or structure or portion thereof, designed for and used to provide a place of abode for human beings. The term residence includes the term “residential” or “residential unit” as referring to the type of or intended use of a building or structure.
(Ord. 16-0428 § 4 (Att. C))
“Runoff”
means that portion of water originating from rainfall and other precipitation that flows over the surface or just below the surface from where it fell and is found in drainage facilities, rivers, streams, springs, seeps, ponds, lakes, wetlands and shallow groundwater as well as on ground surfaces. For the purposes of this definition, “groundwater” means all waters that exist beneath the land surface or beneath the bed of any stream, lake, or reservoir, or other body of surface water, whatever may be the geological formation or structure in which such water stands or flows, percolates or otherwise moves.
(Ord. 16-0428 § 4 (Att. C))
“Shared facility”
means a drainage facility designed to meet one or more of the requirements of KMC § 13.35.050 for two or more separate projects contained within a basin. Shared facilities usually include shared financial commitments for those drainage facilities.
(Ord. 16-0428 § 4 (Att. C))
“Simplified drainage review”
means the drainage review for a proposed single-family residential project or agricultural project that: results in less than 5,000 square feet of new plus replaced pollution-generating impervious surface, results in less than three-quarter acre of pollution-generating pervious surface, limits target impervious and pervious surface as specified in SWDM Section 1.1.2.1, and meets the simplified drainage requirements specified in SWDM Appendix C, including flow control best management practices, erosion and sediment control measures, and drainage plan submittal requirements.
(Ord. 16-0428 § 4 (Att. C))
“Site”
means a single parcel, or two or more contiguous parcels that are under common ownership or documented legal control, used as a single parcel for a proposed project for the purposes of applying this code to a proposed project. For projects located primarily within dedicated rights-of-way, “site” includes the entire width of right-of-way subject to improvements proposed by the project.
(Ord. 16-0428 § 4 (Att. C))
“Source control best management practice” or 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. Source control BMPs are divided into two types. Structural source control BMPs are physical, structural, or mechanical devices or facilities that are intended to prevent pollutants from entering stormwater and an example may include enclosing and/or covering the pollutant source. Operational source control BMPs are nonstructural practices that prevent or reduce pollutants from entering stormwater and examples may include good housekeeping, preventive maintenance procedures, spill prevention and employee training.
(Ord. 22-0551 § 3 (Att. C))
“Stormwater”
means the water produced during precipitation or snowmelt, which runs off, soaks into the ground, or is dissipated through evapotranspiration. Stormwater that runs off or soaks into the ground ultimately becomes surface water or groundwater.
(Ord. 16-0428 § 4 (Att. C))
“Surface water”
means the water that exists on land surfaces before, during, and after stormwater runoff occurs and includes, but is not limited to, the water found on ground surfaces and in drainage facilities, rivers, streams, springs, seeps, ponds, lakes, wetlands, and Puget Sound. It also includes shallow groundwater.
(Ord. 16-0428 § 4 (Att. C))
“Surface Water Design Manual”
means the 2021 King County Surface Water Design Manual, and supporting documentation referenced or incorporated in the Manual, describing surface water and stormwater design and analysis requirements, procedures and guidance adopted pursuant to KMC § 13.35.030. A link to obtain an electronic version of the Surface Water Design Manual is available on King County's webpage.
(Ord. 16-0428 § 4 (Att. C); Ord. 22-0551 § 3 (Att. C))
“Surface water and stormwater management”
means the services provided by the surface water management program, including but not limited to planning, maintenance and operations, regulation, financial administration, public involvement, outreach and education, drainage investigation and enforcement, aquatic resource restoration, surface water and stormwater quality and environmental monitoring, intergovernmental relations and facility design and construction.
(Ord. 16-0428 § 4 (Att. C))
“Undeveloped parcel”
means any parcel which has not been altered from its native state by the construction, creation or addition of impervious or pervious surfaces, including the alteration of soil conditions, ground cover, and species of vegetation (such as landscaping).
(Ord. 16-0428 § 4 (Att. C))
“Water quality treatment facility”
means a drainage facility designed to reduce pollutants once they are already contained in surface water and stormwater runoff. A water quality treatment facility is the structural component of best management practices (BMPs). When used singly or in combination, a water quality treatment facility reduces the potential for contamination of both surface and groundwaters.
(Ord. 16-0428 § 4 (Att. C))