“Area of special flood hazard (ASFH)” means the land in the floodplain subject to a one percent or greater chance of flooding in any given year as calculated in this code and in the engineering standards.

“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 and 47.05.021. The definition of arterial set forth herein is limited to application and enforcement of this code and does not apply to other city codes and standards.

“As-built” means a final drawing of the actual installation of structures, materials and equipment.

“Basin plan or planning” means a plan or study to manage the quality and/or quantity of storm and surface water in a watershed or a drainage basin as provided for in BCC 24.06.140.

“Best management practices (BMP)” means the schedules of activities, prohibitions of practices, maintenance procedures, and structural and/or managerial practices approved by Ecology that, when used singly or in combination, prevent or reduce the release of pollutants and other adverse impacts to waters of Washington State.

“Bioretention” means engineered facilities that treat stormwater by passing it through a specified soil profile, and either retain or detain the treated stormwater for flow attenuation. Refer to the SWMMWW, Chapter 7 of Volume V, for bioretention BMP types and design specifications.

“Building” means any structure used or intended for supporting or sheltering any use or occupancy.

“Capital recovery charge” means a monthly charge imposed on improvements, developments, redevelopments or existing structures that place additional demand on each utility system after January 1, 1997. The capital recovery charge shall be based on an allocation of the utility’s in-service costs plus interest and the number of single-family equivalents served by each utility.

“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 the Washington State Department of Ecology (Ecology) (see BMP C160 in the SWMMWW). 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.

“Commercial agriculture” means 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 five 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.

“Conditionally permissible discharges” refers to those discharges permitted under BCC 24.06.125(D).

“Connection charges” means charges imposed as a condition of connecting to the utility system so that each connecting property bears its equitable share of the costs of the public drainage system and of the costs of facilities that benefit the property. Connection charges include latecomer charges, capital recovery charges and direct facilities charges.

“Converted vegetation (areas)” means the surfaces on a project site where native vegetation, pasture, scrub/shrub, or unmaintained nonnative vegetation (e.g., Himalayan blackberry, Scotch broom) are converted to lawn or landscaped areas, or where native vegetation is converted to pasture.

“Conveyance system” means 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.

“Detention facility” means an above or below ground facility, such as a pond or vault, that temporarily stores stormwater runoff and subsequently releases it at a slower rate than it is collected by the drainage facility system. There is little or no infiltration of stored stormwater.

“Direct facilities charge” refers to a connection charge for utility-funded facilities that directly benefit a property. Stormwater direct facilities charges shall be applied as specified in BCC 24.06.110.

“Director” means the director of the city’s utilities department, or his/her designated representative, including enforcement officers, or other persons designated by the city manager.

Drainage System. Refer to the definition of “storm and surface water system.”

“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: (1) the runoff is dispersed through at least 100 feet of native vegetation in accordance with BMP T5.30 – “Full Dispersion” as described in Chapter 5 of Volume V of the SWMMWW; (2) residential roof runoff is infiltrated in accordance with Downspout Full Infiltration Systems in BMP T5.10A in Volume III of the SWMMWW; or (3) approved continuous runoff modeling methods indicate that the entire runoff file is infiltrated.

“Emergency” means any natural or human-caused event or set of circumstances that disrupts or threatens to disrupt or endanger the operation, structural integrity or safety of the drainage system; or endangers the health and safety of the public or environment; or otherwise requires immediate action by the utility.

“Emergency management plan” provides the foundation, framework and guidelines for initiating and maintaining direction and control of the utility’s response efforts during all emergency or disaster scenarios. The emergency management plan is consistent with and supports the city of Bellevue emergency operations plans and emergency response plans maintained at the regional, state and federal levels of government.

“Emergency operation plan” provides guidance for mitigation, preparedness, response and recovery operations including disaster and emergency responsibilities and procedures, training and community education. The plan provides for the coordination of operations throughout the city during emergencies and disasters, and the best utilization of the city’s resources. The plan meets the requirements of a comprehensive emergency management plan as described in Chapter 118-30 WAC.

“Engineering standards” means the city’s utility engineering standards, which include standards for the design and construction of water, storm and surface water drainage and sanitary sewer facilities.

“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.

Flow Control BMPs. Refer to the definition of “runoff control BMPs.”

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

“Highway” means a main public road connecting towns and cities. The definition of “highway” is limited to application and enforcement of this code and does not apply to other city codes and standards.

“Hydroperiod” means the seasonal occurrence of flooding and/or soil saturation; it encompasses depth, frequency, duration and seasonal pattern of inundation.

“Illicit connection” means any infrastructure connection to the MS4 that is not intended, permitted or used for collecting and conveying stormwater or nonstormwater discharges allowed as specified in the NPDES permit (S5.C.3 and S6.D.3). Examples include, but are not limited to, sanitary sewer connections, floor drains, channels, pipelines, conduits, inlets, or outlets that are connected directly to the MS4.

“Illicit discharge” or otherwise referred to as a “prohibited discharge” means any discharge to the MS4 that is not composed entirely of stormwater or of nonstormwater discharges allowed as specified in the NPDES permit (S5.C.3 and S6.D.3).

“Illicit discharge detection and elimination system program (IDDE)” means an ongoing program authorized by BCC 24.06.045 to detect and remove illicit connections, discharges as defined in 40 CFR 122.26(b)(2), and improper disposal, including any spills not under the purview of another responding authority with jurisdiction, into the storm and surface water systems.

“Impervious surface” means a nonvegetated surface area that 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, rooftops, 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.

“Latecomer agreement” means a contract that provides for the reimbursement of costs to developers who construct facilities that directly benefit other properties.

“LID best management practices” means distributed stormwater management practices, integrated into a project design, that emphasize pre-disturbance 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 re-use.

“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 (LID)” means a stormwater and land use management strategy that strives to mimic pre-disturbance 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” means repair and maintenance activities conducted on currently serviceable structures, facilities, and equipment that involve 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 maintenance standards of Chapter 4, Volume V of the SWMMWW. See also pavement maintenance exemptions in Section 1 of Appendix 1 of the Western Washington Phase II Municipal Stormwater Permit.

“Maintenance standards” means the city’s utility maintenance standards, which include minimum requirements for maintaining the storm and surface water system so the system functions as intended and provides water quality protection and flood control.

“Maximum extent practicable” or “MEP” refers to paragraph 402(p)(3)(B)(iii) of the federal Clean Water Act, now or as hereafter amended, 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 utility or the state determines appropriate for the control of such pollutants.

“Minimum requirements (MRs)” refer to the regulations contained in BCC 24.06.065 and applicable engineering standards, which describe requirements for stormwater management for development and redevelopment as required by the NPDES permit.

“Municipal separate storm sewer system,” or “MS4,” is a regulated municipal storm utility system as defined in the Western Washington Phase II Municipal Stormwater Permit.

“National Pollutant Discharge Elimination System (NPDES)” 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 federal 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.

“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 of native vegetation include, but are not limited to, 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” means 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 in Chapter 58.17 RCW and in Chapters 20.45A and 20.45B LUC. Projects meeting the definition of redevelopment shall not be considered new development.

“NPDES permit” means an authorization, license or equivalent control document issued by the United States Environmental Protection Agency or the Washington State Department of Ecology to implement the requirements of the NPDES program.

“On-site stormwater management BMPs” is a synonym for low impact development BMPs.

“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.

“Permissible discharge” refers to those discharges permitted under BCC 24.06.125(C).

“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.

“Pollution” means the contamination or other alteration of the physical, chemical, or biological properties, of waters of the state, including 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 or render 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 (PGHS)” means those hard surfaces considered to be a significant source of pollutants in stormwater runoff. See the listing of surfaces under pollution-generating impervious surface.

“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: vehicular use, industrial activities (as further defined in the glossary of Volume I of the SWMMWW); storage of erodible or leachable materials, wastes, or chemicals, and which receive direct rainfall or the run-on or blow-in of rainfall; metal roofs unless they are coated with an inert, nonleachable material (e.g., baked-on enamel coating); or roofs that are subject to venting significant amounts of dusts, mists, or fumes from manufacturing, commercial, or other indoor activities.

“Pollution-generating pervious surface (PGPS)” means any nonimpervious surface subject to vehicular use, industrial activities (as further defined in the glossary of the SWMMWW); or storage of erodible or leachable materials, wastes, or chemicals, and that receive direct rainfall or run-on or blow-in of rainfall, use of pesticides and fertilizers, or loss of soil. Typical PGPS include permeable pavement subject to vehicular use, lawns, landscaped areas including: golf courses, parks, cemeteries, and sports fields (natural and artificial turf).

“Pre-developed condition” means the native vegetation and soils that existed at a site prior to the influence of Euro-American settlement. The pre-developed condition shall be assumed to be forested land cover unless reasonable, historic information is provided that indicates the site was prairie prior to settlement.

“Private storm and surface water system” or “private drainage facility” means any element of the storm and surface water system which is not a part of the public storm and surface water system as defined in this code.

“Procedure” means a procedure adopted by the utility, by and through the director, to implement this code, or to carry out other responsibilities as may be required by this code, engineering standards, related manuals, or other codes, ordinances, or resolutions of the city or other agencies. Procedure as defined herein is often referred to as a standard operating procedure or SOP.

“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. The definition of project site applies solely to application and enforcement of this code and does not supersede or replace the definition of “site” as defined elsewhere in the Bellevue City Code.

Prohibited Discharge. Refer to definition of “illicit discharge.”

“Property owner” means any individual, company, partnership, joint venture, corporation, association, society or group that owns or has a contractual interest in the subject property or has been authorized by the owner to act on his/her behalf, including but not limited to an agent, contractor, operation, applicant, or developer.

“Public storm and surface water system” or “public drainage system” means those elements of the storm and surface water system maintained and operated by the utility, which includes elements located on property owned by the utility or in public right-of-way except to the extent that private ownership is indicated as a matter of record or by law and elements located on property on which the city has an easement, license, or other right of use for utility purposes.

“Rain garden” means a nonengineered 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.

“Receiving water body or receiving waters” are bodies of water or surface water systems to which surface runoff is discharged via a point source of stormwater or via sheet flow. Ground water to which surface runoff is directed by infiltration.

“Redevelopment” means, on a site that is already substantially developed (i.e., has 35 percent or more existing hard surface coverage), 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 maintenance activity; and land disturbing activities.

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

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

“Runoff control BMPs,” also referred to as “flow control BMPs,” means BMPs that are intended to control or manage the rate and/or quantity of stormwater runoff.

“Runoff treatment BMPs” means BMPs that are intended to remove sediment and other pollutants from stormwater runoff.

“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. The definition of “site” applies solely to application and enforcement of this code and does not supersede or replace the definition of “site” as defined elsewhere in the Bellevue City Code.

“Source control BMP” means a structure or operation that is intended to prevent pollutants from coming into contact with stormwater through physical separation of areas or careful management of activities that are sources of pollution. The SWMMWW 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 BMPs” are nonstructural practices that prevent or reduce pollutants from entering stormwater.

Standard Operating Procedure or SOP. Refer to the definition of “procedure.”

“Storm and surface water system plan” (or a similarly titled document) means the latest version of the city’s storm and surface water system plan as adopted by the city council.

“Storm and surface water system,” also referred to as the “drainage system,” means the entire system within the city, both public and private, naturally existing and manmade, for the drainage, conveyance, detention, treatment or storage of storm and surface waters. However, facilities directly associated with buildings or structures such as foundation drains, rockery/retaining wall drains, gutters and downspouts or groundwater under-drains are not considered parts of the storm and surface water system.

“Stream” means those areas where surface waters flow sufficiently to produce a defined channel or bed. A defined channel or bed is an area that demonstrates clear evidence of the passage of water and includes, but is not limited to, indicated by hydraulically sorted sediments or the removal of vegetative litter or loosely rooted vegetation by the action of moving water. The channel or bed need not contain water year-round. This definition is not meant to include irrigation ditches, canals, stormwater runoff devices or other entirely artificial watercourses unless they are used to convey streams naturally occurring prior to construction. Those topographic features that resemble streams but have no defined channels (i.e., swales) shall be considered streams when hydrologic and hydraulic analyses done pursuant to a development proposal predict formation of a defined channel after development. The definition of “stream” set forth herein is limited to application and enforcement of this code and does not apply to other city codes and standards.

“Structure” means a combination of materials constructed and erected permanently on or under the ground or attached to something having permanent location on or under the ground. Not included are residential fences, retaining walls less than 30 inches in height, rockeries less than 30 inches in height and similar improvements of a minor character. “Structure” can also mean a catchbasin or manhole in reference to a storm drainage system.

“SWMMWW” means the Washington State Department of Ecology 2012 Stormwater Management Manual for Western Washington (as amended in 2014) (now or hereafter amended).

“Threshold discharge area” means an on-site area draining to a single natural discharge location, or to multiple natural discharge locations that combine within one-quarter mile downstream (as determined by the shortest flowpath). Refer to the SWMMWW for additional information.

“Unsafe condition” means any condition on any premises which is a hazard to public health, safety, welfare, or environment that does or may impair or impede the operation or functioning of any portion of the public drainage system or which may cause damage thereto.

“Utility” means the storm and surface water utility administered as part of the Bellevue utilities department, as provided by Chapter 3.38 BCC.

“Utility developer extension agreement” means a contract between the utility and a developer that provides for plan review and inspection of storm drainage facilities that satisfy new development or redevelopment requirements.

“Vehicular use” means regular use of an impervious or pervious surface by motor vehicles. The following are subject to regular vehicular use: roads, unvegetated road shoulders, bike lanes within the traveled lane of a roadway, driveways, parking lots, unrestricted access fire lanes, vehicular equipment storage yards, and airport runways.

The following are not considered subject to regular vehicular use: paved bicycle pathways separated from and not subject to drainage from roads for motor vehicles, restricted access fire lanes, and infrequently used maintenance access roads.

“Wetland” means those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas. Wetlands do not include those artificial wetlands intentionally created from non-wetland 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 non-wetland areas to mitigate the conversion of wetlands.