Chapter 22.01 Stormwater Management Regulations and Requirements

(a) Stormwater pollution is a problem associated with land utilization, development, redevelopment and the common occurrence of potential pollutants such as pesticides, fertilizers, petroleum products, pet wastes and numerous others.

(b) Land utilization, development and redevelopment is also known to increase both the volume and duration of peak flows. The resulting erosion, scouring, and deposition of sediment affect the ecological balance.

(c) Sedimentation and stormwater pollution cause diversity of species to decrease and allows more tolerant (and usually less desirable) species to remain.

(d) Development and redevelopment of land may have led to:

(1) Water quality degradation through discharge of nutrients, metals, oil and grease, toxic materials, and other detrimental substances including, without limitation, insect and weed control compounds, drainage, and storm and surface water runoff problems within the City; and

(2) Safety hazards to both lives and property posed by uncontrolled water runoff on streets and highways.

(e) Continuation of present stormwater management practices, to the extent that they exist, will lead to further water quality degradation, erosion, and property damage, and endanger the health and safety of the inhabitants of the City.

(f) In the future such problems and dangers will be reduced or avoided if existing properties and future developers, both private and public, provide for stormwater quality and quantity controls.

(g) Stormwater quality and quantity controls can be achieved when land is developed or redeveloped by implementing appropriate best management practices (BMPs).

(h) Best management practices can be expected to perform as intended only when properly designed, constructed and maintained. (Ord. 10-894 § 1).

22.01.020 Need.

The City Council finds that this chapter is necessary in order to:

(a) Minimize or eliminate water quality degradation;

(b) Prevent erosion and sedimentation in creeks, streams, ponds, lakes and other water bodies;

(c) Protect property owners adjacent to existing and developing lands from increased runoff rates which could cause erosion of abutting property;

(d) Preserve and enhance the suitability of waters for contact recreation, fishing, and other beneficial uses;

(e) Preserve and enhance the aesthetic quality of the water;

(f) Promote sound development policies which respect and preserve City surface water, groundwater and sediment;

(g) Enhance the safety of City roads and rights-of-way;

(h) Decrease stormwater-related damage to public and private property from existing and future runoff;

(i) Protect the health, safety and welfare of the inhabitants of the City;

(j) Promote low impact development strategies that reduce impervious surface and stormwater runoff. (Ord. 10-894 § 1).

22.01.030 Purpose.

(a) The provisions of this chapter are intended to guide and advise all who conduct new development or redevelopment within the City. The provisions of this chapter establish the minimum level of compliance which must be met to permit a property to be developed or redeveloped within the City.

(b) The provisions of this chapter are also intended to guide and advise all residential and commercial property owners within the City on regulations pertaining to the introduction of pollutants into the stormwater system in our efforts to protect water quality within the City.

(1) Minimize water quality degradation and sedimentation in streams, ponds, lakes, wetlands and other water bodies;

(2) Minimize the impact of increased runoff, erosion and sedimentation caused by land development and maintenance practices;

(3) Maintain and protect groundwater resources;

(4) Minimize adverse impacts of alterations on ground and surface water quantities, locations and flow patterns;

(5) Decrease potential landslide, flood and erosion damage to public and private property;

(6) Promote site planning and construction practices that are consistent with natural topographical, vegetational and hydrologic conditions;

(7) Maintain and protect the City stormwater management infrastructure and those downstream;

(8) Provide a means of regulating the contribution of pollutants to the municipal stormwater system from all nonstormwater discharges, illicit connections, or illegal dumping into the municipal stormwater system by any person or from any property within the City of DuPont;

(9) Provide a means of regulating clearing and grading of private and public land while minimizing water quality impacts in order to protect public health and safety; and

(10) Provide minimum development regulations and construction procedures which will preserve, replace or enhance, to the maximum extent practicable, existing vegetation to preserve and enhance the natural quality of lands, wetlands and water bodies. (Ord. 10-894 § 1).

22.01.040 Definitions.

For the purposes of this chapter, the following definitions shall apply:

“AKART” means all known, available and reasonable methods of prevention, control, and treatment. See also the State Water Pollution Control Act, RCW 90.48.010 and 90.48.520.

“American Public Works Association” or “APWA” means the adopted edition of the Washington State chapter of the American Public Works Association.

“Approval” means the proposed work or completed work conforms to this chapter in the opinion of the Director or his/her designee.

“Arterial” means a road or street primarily for through traffic. A major arterial connects an interstate highway to cities and counties. A minor arterial connects major arterials to collectors. A collector connects an arterial to a neighborhood. A collector is not an arterial. A local access road connects individual homes to a collector.

“As graded” means the extent of surface conditions on completion of grading.

“Basin plan” means a plan and all implementing regulations and procedures including but not limited to land use management adopted by ordinance for managing surface and stormwater management facilities and features within individual sub-basins.

“Bedrock” means the more or less solid rock in place either on or beneath the surface of the earth. It may be soft, medium, or hard and have a smooth or irregular surface.

“Bench” means a relatively level step excavated into earth material on which fill is to be placed.

“Best management practice” or “BMP” means the schedule of activities, prohibitions of practices, maintenance procedures and structural and/or managerial practices approved by the Department of Ecology that, when used singly or in combination, prevent or reduce the release of pollutants and other impacts to waters of Washington State. BMPs are listed and described in the Manual.

“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 Department (see BMP C160 in the Stormwater Management Manual for Western Washington (2005)). 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.

“Civil engineer” means a professional engineer licensed in the State of Washington in civil engineering.

“Civil engineering” means the application of the knowledge of the forces of nature, principles of mechanics and the properties of materials to the evaluation, design and construction of civil works for the beneficial uses of mankind.

“Clean Water Act” means the federal Water Pollution Control Act (33 U.S.C. Section 1251 et seq.), and any subsequent amendments thereto.

“Clearing” means the destruction and removal of vegetation by manual, mechanical, or chemical methods.

“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 wholesale 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.

“Compaction” means densification of a fill by mechanical means.

“Critical areas” means, at a minimum, areas which include wetlands, areas with a critical recharging effect on aquifers used for potable water, fish and wildlife habitat conservation areas, frequently flooded areas, geologically hazardous areas, including unstable slopes, and associated areas and ecosystems.

“Design storm” means a prescribed hyetograph and total precipitation amount (for a specific duration recurrence frequency) used to estimate runoff for a hypothetical storm of interest or concern for the purposes of analyzing existing drainage, designing new drainage facilities or assessing other impacts of a proposed project on the flow of surface water. (A hyetograph is a graph of percentages of total precipitation for a series of time steps representing the total time during which the precipitation occurs.)

“Detention” means the release of stormwater runoff from the site at a slower rate than it is collected by the stormwater facility system, the difference being held in temporary storage.

“Detention facility” means an above or below ground facility, such as a pond or tank, 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.

“Director” means the Mayor of the City of DuPont or his/her designee.

“Drainage basin” means a geographic and hydrologic subunit of a watershed.

“Earth material” means any rock, natural soil or fill and/or any combination thereof.

“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 on residential development sites are considered ineffective if 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 Stormwater Management Manual for Western Washington (2005).

“Engineering geologist” means a geologist experienced and knowledgeable in engineering geology.

“Engineering geology” means the application of geologic knowledge and principles in the investigation and evaluation of naturally occurring rock and soil for use in the design of civil works.

“Erosion” means the wearing away of the land surface by running water, wind, ice, or other geological agents, including such processes as gravitational creep. Detachment and movement of soil rock fragments by water, wind, ice, or gravity.

“Excavation” means the mechanical removal of earth material.

“Experimental BMP” means a BMP that has not been tested and evaluated by the Department of Ecology in collaboration with local governments and technical experts.

“Fill” means a deposit of earth material placed by artificial means.

“Forest practice” means any activity conducted on or directly pertaining to forest land and relating to growing, harvesting, or processing timber, including but not limited to:

(1) Road and trail construction;

(2) Harvesting, final and intermediate;

(3) Pre-commercial thinning;

(4) Reforestation;

(5) Fertilization;

(6) Prevention and suppression of diseases and insects;

(7) Salvage of trees; and

(8) Brush control.

“Frequently flooded areas” means the 100-year floodplain designations of the Federal Emergency Management Agency and the National Flood Insurance Program.

“Geologically hazardous areas” means areas that because of their susceptibility to erosion, sliding, earthquake or other geological events, are not suited to the siting of commercial, residential or industrial development consistent with public health or safety concerns.

“Grade” means the slope of a road, channel, or natural ground. The finished surface of a canal bed, roadbed, top of embankment, or bottom of excavation; any surface prepared for the support of construction such as paving or the laying of a conduit.

(1) Existing Grade. The grade prior to grading.

(2) Rough Grade. The stage at which the grade approximately conforms to the approved plan.

(3) Finish Grade. The final grade of the site which conforms to the approved plan.

To “grade” means to finish the surface of a canal bed, roadbed, top of embankment or bottom of excavation.

“Gradient terrace” means an earth embankment or a ridge and channel constructed with suitable spacing and an acceptable grade to reduce erosion damage by intercepting surface runoff and conducting it to a stable outlet at a stable nonerosive velocity.

“Groundwater” means water in a saturated zone or stratum beneath the surface of land or a surface water body.

“Hazardous materials” means any material, including any substance, waste, or combination thereof, which because of its quantity, concentration, or physical, chemical, or infectious characteristics may cause, or significantly contribute to, a substantial present or potential hazard to human health, safety, property or the environment when improperly treated, stored, transported, disposed of, or otherwise managed.

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

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

“Hyperchlorinated” means water that contains more than 10 mg/Liter chlorine.

“Illicit connection” means any manmade conveyance that is connected to a municipal separate storm sewer without a permit, excluding roof drains and other similar-type connections. Examples include sanitary sewer connections, floor drains, channels, pipelines, conduits, inlets, or outlets that are connected directly to the municipal separate storm sewer system.

“Illicit discharge” means a discharge to a stormwater drainage system that is not composed entirely of stormwater, except discharges pursuant to a NPDES permit (other than the NPDES permit for discharges from the municipal storm sewer) and discharges resulting from fire-fighting activities.

“Impervious surface” means a hard surface area which either prevents or retards the entry of water into the soil mantle as under natural conditions prior to development, and/or 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 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.

“Interflow” means that portion of rainfall that infiltrates into the soil and moves laterally through the upper soil horizons until intercepted by a stream channel or until it returns to the surface; for example, in a wetland, spring or seep.

“Land disturbing activity” means any activity that results in a 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, demolition, construction, 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.

“Low impact development” means use of innovative or creative approaches to site design, using methods such as retention of natural vegetation, significant reduction of effective impervious surface, enhanced infiltration, and changes in traditional site features such as roads and structures, to achieve dramatically reduced or zero drainage discharge from the site after development.

“Low impervious surface” or “low effective impervious surface” means impervious surface reduction to a small fraction of that resulting from traditional site development techniques such that usual manmade drainage collection systems are not necessary.

“Low impervious surface project” or “low effective impervious surface project” means those projects characterized by a reduction of total impervious surface to a small fraction of that which would result from traditional development. Such projects will place impervious surfaces in increments such that runoff travel distance to a vegetative buffer is minimized and does not exceed a maximum of 15 feet. Further, the landscaped areas within such projects will be minimized and buffered on the down-slope side by a forested area. A forested area shall comprise at least 60 percent of the land area upon which the project is located, shall be maintained in perpetuity and shall substitute for a traditional drainage system. It is preferred that the site for such projects be characterized by a predominance of Soils Conservation Service Class C or D soils.

“Maintenance” means repair and maintenance including activities conducted on currently serviceable structures, facilities, and equipment that involve no expansion or use beyond that previously existing and result 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.

“Mitigation” means, in the following order of preference:

(1) Avoiding the impact altogether by not taking a certain action or part of an action;

(2) Minimizing impacts by limiting the degree or magnitude of the action and its implementation by using appropriate technology, or by taking affirmative steps to avoid or reduce impacts;

(3) Rectifying the impact by repairing, rehabilitating or restoring the affected environment;

(4) Reducing or eliminating the impact over time by preservation and maintenance operations during the life of the action; and

(5) Compensation for the impact by replacing, enhancing, or providing substitute resources or environments.

“Municipal separate storm sewer system” or “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):

(1) 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 CWA that discharges to waters of the United States;

(2) Designed or used for collected and conveying stormwater;

(3) Which is not a combined sewer; and

(4) Which is not part of a publicly owned treatment works (POTW) as defined at 40 CFR 122.2.

“National pollutant discharge elimination system stormwater discharge permit” or “NPDES permit” means a permit issued by the EPA (or by a state under authority delegated pursuant to 33 U.S.C. Section 1342(b)) that authorizes the discharge of pollutants to the waters of the State, whether the permit is applicable on an individual, group, or general area-wide basis.

“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.

“Natural location” means the location of those channels, swales, and other nonmanmade conveyance systems as defined by the first documented topographic contours existing for the subject property, either from maps or photographs or such other means as appropriate.

“New development” means the following activities: land disturbing activities, structural development, including construction, installation or expansion of a building or other structure; creation of impervious surfaces; Class IV--general forest practices that are conversions from timberland to other uses; and subdivision and short subdivision of land as defined and applied in Chapter 58.17 RCW. All other forest practices and commercial agriculture are not considered new development. Projects meeting the definition of redevelopment shall not be considered new development.

“Nonstormwater discharge” means any discharge to the storm drain system that is not composed entirely of stormwater.

“Person” means any individual, partnership, corporation, association, organization, cooperative, public or municipal corporation, agency of the State, or local government unit, however designated.

“Pollutant” means anything which causes or contributes to pollution. Pollutants may include, but are not limited to: paints, varnishes, and solvents; oil and other automotive fluids; nonhazardous liquid and solid wastes and yard wastes; refuse, rubbish, garbage, litter, or other discarded or abandoned objects and accumulations, so that same may cause or contribute to pollution; floatables; pesticides, herbicides, and fertilizers; hazardous substances and wastes; sewage, fecal coliform and pathogens; dissolved and particulate metals; animal wastes; wastes and residues that result from constructing a building or structure; and noxious or offensive matter of any kind.

“Pollution” means 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 impervious surface” or “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 Manual); 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, nonleachable 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 fire lanes, and infrequently used maintenance access roads.

“Pollution-generating pervious surfaces” or “PGPS” means 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” means 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.

“Premises” means any building, lot, parcel of land, or portion of land whether improved or unimproved including adjacent sidewalks and parking strips.

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

“Receiving waters” means bodies of water or surface water systems to which surface runoff is discharged via a point source of stormwater or via sheet flow.

“Redevelopment” means, on an already substantially developed site (i.e., has 35 percent 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, and/or replacement of impervious surface that is not part of a routine maintenance activity, and land disturbing activities associated with structural or impervious redevelopment.

“Regional retention/detention system” means a stormwater quantity control structure designed to correct existing excess surface water runoff problems of a basin or sub-basin. The area downstream has been previously identified as having existing or predicted significant and regional flooding and/or erosion problems. This term is also used when a detection facility is used to detain stormwater runoff from a number of different businesses, developments or areas within a catchment.

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

“Retention/detention facility” or “R/D” 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 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.

“Slope” means the degree of deviation of a surface from the horizontal; measured as a numerical ratio, percent, or in degrees. Expressed as a ratio, the first number is the horizontal distance (run) and the second is the vertical distance (rise), as 2:1. A 2:1 slope is a 50 percent slope. Expressed in degrees, the slope is the angle from the horizontal plane, with a 90 degree slope being vertical (maximum) and 45 degrees being a 1:1 or 100 percent slope.

“Soil” means the unconsolidated mineral and organic material on the immediate surface of the earth that serves as a natural medium for the growth of land plants.

"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 pollutants. Source control BMPs are separated into two types. Structural source control BMPs are physical, structural, or mechanical devices, or facilities that are intended to prevent pollutants from entering the stormwater. Operational BMPs are nonstructural practices that prevent or reduce pollutants from entering stormwater.

“Stormwater” means that portion of precipitation that does not naturally percolate into the ground or evaporate, but flows via overland flow, interflow, channels or pipes into a defined surface water channel, or a constructed infiltration facility.

“Stormwater drainage system” means constructed and natural features which function together as a system to collect, convey, channel, hold, inhibit, retain, detain, infiltrate, divert, treat or filter stormwater.

“Stormwater facility” means a constructed component of a stormwater drainage system, designed or constructed to perform a particular function, or multiple functions. Stormwater facilities include, but are not limited to, pipes, swales, ditches, culverts, street gutters, detention basins, retention basins, constructed wetlands, infiltration devices, catch basins, oil/water separators, sediment basins and modular pavement. The Manual contains BMPs to prevent or reduce pollution.

“Stormwater Management Manual” or “Manual” means the 2005 Edition of the State of Washington Department of Ecology’s “Stormwater Management Manual for Western Washington” and all amendments and additions thereto. The Manual contains BMPs to prevent or reduce pollution.

“Stormwater Site Plan” means a comprehensive report containing all of the technical information and analysis necessary for the City to evaluate a proposed new development or redevelopment project for compliance with stormwater requirements. Guidance on preparing a Stormwater Site Plan is contained in the Manual.

“Threshold discharge area” means an on‑site area 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).

“Toe of slope” means a point or line of slope in an excavation or cut where the lower surface changes to horizontal or meets the existing ground slope.

“Top of slope” means a point or line on the upper surface of a slope where it changes to horizontal or meets the original surface.

“Treatment BMP” means a BMP that is intended to remove pollutants from stormwater. A few examples of treatment BMPs are detention ponds, oil/water separators, biofiltration swales and constructed wetlands.

“Unstable slopes” means those sloping areas of land which have in the past exhibited, are currently exhibiting, or will likely in the future exhibit mass movement of earth.

“Vegetation” means all organic plant life growing on the surface of the earth.

“Water body” means surface waters including rivers, streams, lakes, marine waters, estuaries, and wetlands.

“Watershed” means a geographic region within which water drains into a particular river, stream, or body of water as identified and numbered by the State of Washington water resource inventory areas (WRIAs) as defined in Chapter 173-500 WAC.

“Wetlands” means those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas. Wetlands may include those artificial wetlands intentionally created from nonwetland areas to mitigate the conversion of wetland 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. (Ord. 10-894 § 1).

22.01.050 General provisions.

(a) It is not intended that this chapter repeal, abrogate, or impair any existing regulations, easements, covenants, or deed restrictions. However, where this chapter imposes greater restrictions, the provisions of this chapter shall prevail.

(b) The provisions of this chapter shall be held to be minimum requirements in their interpretation and application and shall be liberally construed to serve the purposes of this chapter. (Ord. 10-894 § 1).

22.01.060 Applicability.

(a) When any provision of any other chapter of the City Code conflicts with this chapter, that provision which provides more environmental protection shall apply unless specifically provided otherwise in this chapter. Prior to fulfilling the requirements of this chapter, the City shall not grant any approval or permission to conduct a regulated activity including but not limited to the following: civil construction or building permit; grading and clearing permit; right-of-way permit; shoreline substantial development permit; subdivision; short subdivision.

(b) Regulated activities shall be conducted only after the City approves a Stormwater Site Plan. Guidance on preparing a Stormwater Site Plan is contained in the Manual. (Ord. 10-894 § 1).

22.01.070 Regulated activities.

Consistent with the Minimum Requirements contained in this chapter, the City shall approve or disapprove the following activities, unless exempted in DMC 22.01.080:

(a) New Development.

(1) Land disturbing activities, including Class IV--general forest practices that are conversions from timberland to other uses;

(2) Structural development, including construction, installation or expansion of a building or other structure;

(3) Creation of impervious surfaces; and

(4) Subdivision, short subdivision and binding site plans, as defined in RCW 58.17.020.

(5) Projects meeting the definition of redevelopment shall not be considered new development.

(b) Redevelopment.

(1) On a site that is already substantially developed (i.e., has 35 percent 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; land disturbing activity; and/or replacement of impervious surface that is not part of a routine maintenance activity. (Ord. 10-894 § 1).

22.01.080 Exemptions.

(a) Forest Practices. Forest practices regulated under WAC Title 222, except for Class IV--general forest practices that are conversions from timberland to other uses, are exempt from the provisions of the minimum requirements.

(b) Commercial Agriculture. Commercial agriculture practices involving working the land for production are generally exempt. However, the conversion from timberland to agriculture, and the construction of impervious surfaces, are not exempt.

(c) Oil and Gas Field Activities or Operations. Construction of drilling sites, waste management pits, and access roads, as well as construction of transportation and treatment infrastructure such as pipelines, natural gas treatment plants, natural gas pipeline compressor stations, and crude oil pumping stations are exempt. Operators are encouraged to implement and maintain best management practices to minimize erosion and control sediment during and after construction activities to help ensure protection of surface water quality during storm events.

(d) Road Maintenance. The following road maintenance practices are exempt: pothole and square cut patching, overlaying existing asphalt or concrete pavement with asphalt or concrete without expanding the area of coverage, shoulder grading, reshaping/regarding drainage systems, crack sealing, resurfacing with in-kind material without expanding the road prism, and vegetation maintenance.

The following road maintenance practices are considered redevelopment, and therefore are not categorically exempt. The extent to which the Minimum Requirements apply is explained for each circumstance:

(1) Removing and replacing a paved surface to base course or lower, or repairing the roadway base: If impervious surfaces are not expanded, Minimum Requirements Nos. 1 through 5 apply. However, in most cases, only Minimum Requirement No. 2, Construction Stormwater Pollution Prevention Plan, will be germane. Where appropriate, project proponents are encouraged to look for opportunities to use permeable and porous pavements.

(2) Extending the pavement edge without increasing the size of the road prism, or paving graveled shoulder: These are considered new impervious surface and are subject to the Minimum Requirements that are triggered when the thresholds identified for redevelopment projects are met.

(3) Resurfacing by upgrading from dirt to gravel, asphalt, or concrete; upgrading from gravel to asphalt, or concrete; or upgrading from a bituminous surface treatment (chip seal) to asphalt or concrete: These are considered new impervious surfaces and are subject to the Minimum Requirements that are triggered when the thresholds identified for redevelopment projects are met.

(e) Underground Utility Projects. Underground utility projects that replace the ground surface with in-kind material or materials with similar runoff characteristics are only subject to Minimum Requirement No. 2, Construction Stormwater Pollution Prevention Plan.

(f) Development undertaken by the Washington State Department of Transportation in State highway rights-of-way is regulated by Chapter 173-270 WAC, the Puget Sound Highway Runoff Program. (Ord. 10-894 § 1).

22.01.090 General requirements.

(a) The 2005 State of Washington Department of Ecology’s Stormwater Management Manual for Western Washington is hereby adopted by reference, except as modified herein for consistency with the requirements of the Western Washington Phase II Municipal Stormwater Permit, and is hereinafter referred to as the Manual.

(b) General. BMPs (best management practices) shall be used to control pollution from stormwater. BMPs shall be used to comply with the standards in this chapter. BMPs are in the Manual.

(c) Deviations. In order to achieve goals of low impervious surface development or other source reduction preventative actions or design, deviations from public works development standards may be considered and authorized in accordance with the procedures and requirements of such standards. Deviations that require approval under the Land Use Code, such as parking and landscaping standards, will require an administrative adjustment of standards in accordance with the procedures for the applicable standards.

(d) Illicit discharges to stormwater drainage systems are prohibited. No person shall throw, drain, or otherwise discharge into the MS4 any pollutants or water containing pollutants, other than stormwater.

(e) The following categories of nonstormwater discharges are prohibited unless the stated conditions are met:

(1) Discharges from potable water sources, including water line flushing, hyperchlorinated water line flushing, fire hydrant system flushing, and pipeline hydrostatic test water. Planned discharges shall be dechlorinated to a concentration of 0.1 ppm or less, pH-adjusted, if necessary, and volumetrically and velocity controlled to prevent resuspension of sediments in the MS4.

(2) Discharges from lawn watering and other irrigation runoff. These shall be minimized through, at a minimum, public education activities and water conservation efforts.

(3) Dechlorinated swimming pool discharges. The discharges shall be dechlorinated to a concentration of 0.1 ppm or less, pH-adjusted and reoxygenized if necessary, volumetrically and velocity controlled to prevent resuspension of sediments in the MS4. Swimming pool cleaning wastewater and filter backwash shall not be discharged to the MS4.

(4) Street and sidewalk wash water, water used to control dust, and routine external building wash down that does not use detergents. Discharges from these sources shall be minimized through public education activities in accordance with the permit. At active construction sites, street sweeping must be performed prior to washing the street.

(5) Other nonstormwater discharges. The discharges shall be in compliance with the requirements of the stormwater pollution prevention plan reviewed by the City, which addresses control of construction site dewatering discharges.

(6) Solid or liquid wastes thrown, drained or otherwise discharged directly or indirectly into the municipal storm drain system and/or surface and groundwaters. Examples of prohibited contaminants include, but are not limited to, the following:

(A) Trash or debris;

(B) Construction materials;

(D) Antifreeze and other automotive products;

(E) Metals in either particulate or dissolved form;

(F) Flammable or explosive materials;

(G) Radioactive material;

(H) Batteries;

(I) Acids, alkalis, or bases;

(J) Paints, stains, resins, lacquers, or varnishes;

(K) Degreasers and/or solvents;

(L) Pesticides, herbicides, or fertilizers;

(M) Steam cleaning wastes;

(N) Soaps, detergents, or ammonia;

(O) Domestic animal wastes;

(P) Recreational vehicle waste;

(Q) Animal carcasses;

(R) Food wastes;

(S) Bark and other fibrous materials;

(T) Lawn clippings, leaves, or branches;

(U) Silt, sediment, concrete, cement or gravel;

(V) Dyes (discharged without prior notification and approval of the City);

(W) Chemicals not normally found in uncontaminated water;

(X) Any other process-associated discharge except as otherwise allowed in this section; and

(Y) Any hazardous material or waste not listed above.

(f) The following categories of nonstormwater discharges are exempt from the discharge prohibitions established by this section:

(1) Diverted stream flows;

(2) Rising groundwaters;

(3) Uncontaminated groundwater infiltration (as defined at 40 CFR 35.2005(20));

(4) Uncontaminated pumped groundwater;

(5) Foundation drains;

(6) Air conditioning condensation;

(7) Irrigation water from agricultural sources that is commingled with urban stormwater;

(8) Springs;

(9) Water from crawl space pumps;

(10) Footing drains;

(11) Flows from riparian habitats and wetlands;

(12) Nonstormwater discharges covered by another NPDES permit; and

(13) Discharges from emergency fire fighting activities.

(g) Prohibition of Illicit Connections.

(1) The construction, use, maintenance, or continued existence of illicit connections to the storm drain system is prohibited.

(2) This prohibition expressly includes, without limitation, illicit connections made in the past, regardless of whether the connection was permissible under law or practices applicable or prevailing at the time of connection.

(3) A person is considered to be in violation of this section if the person connects a line conveying sewage to the MS4, or allows such a connection to continue. (Ord. 10-894 § 1).

22.01.100 Approval standards--New development.

(a) All new development shall comply with Minimum Requirement No. 2.

(b) The following new development shall be required to comply with Minimum Requirements Nos. 1 through 5:

(1) Creation or addition of 2,000 square feet or more of new, replaced, or new plus replaced impervious surface area; or

(2) Land disturbing activities of 7,000 square feet or greater.

(c) All new development that includes the creation or addition of 5,000 square feet, or greater, or converts three-quarters acre or greater, of native vegetation to lawn or landscaped areas, and/or converts two and one-half acres or greater of native vegetation to pasture shall comply with Minimum Requirements Nos. 1 through 9 in DMC 22.01.210 through 22.01.290.

Compliance shall be demonstrated through the implementation of an approved stormwater site. (Ord. 10-894 § 1).

22.01.110 Approval standards--Redevelopment.

(a) All redevelopment shall comply with Minimum Requirement No. 2.

(b) The following redevelopment shall be required to comply with Minimum Requirements Nos. 1 through 5:

(1) Creation or addition of 2,000 square feet or more of new, replaced, or new plus replaced impervious surface area; or

(2) Land disturbing activities of greater than 7,000 square feet.

(1) Addition of more than 5,000 square feet of new impervious surface area; or

(2) Conversion of three-quarters acre or more of native vegetation to lawn or landscaped areas; or

(3) Conversion of two and one-half acres or more of native vegetation to pasture.

(d) For road-related projects, runoff from the replaced and new impervious surfaces (including pavement, shoulders, curbs and sidewalks) shall meet all the Minimum Requirements if the new impervious surfaces total 5,000 square feet or more and total 50 percent or more of the existing impervious surfaces within the project limits. The project limits shall be defined by the length of the project and the width of the right-of-way.

(e) Other types of redevelopment projects shall comply with all the Minimum Requirements for the new and replaced impervious surfaces if the total of new plus replaced impervious surfaces is 5,000 square feet or more, and the valuation of proposed improvements, including interior improvements, exceeds 50 percent of the assessed value of the existing site improvements. (Ord. 10-894 § 1).

22.01.200 Minimum stormwater requirements for new development and redevelopment.

DMC 22.01.210 through 22.01.290 describe the Minimum Requirements for stormwater management for new development and redevelopment sites and projects, as applicable pursuant to the preceding sections. (Ord. 10-894 § 1).

22.01.210 Minimum Requirement No. 1--Preparation of Stormwater Site Plan.

(a) A Stormwater Site Plan is required for all projects meeting the thresholds found in DMC 22.01.100 and 22.01.110.

(b) The Stormwater Site Plan shall be prepared in accordance with Chapter 3 of Volume I of the 2005 Stormwater Management Manual for Western Washington. (Ord. 10-894 § 1).

22.01.220 Minimum Requirement No. 2--Construction Stormwater Pollution Prevention Plan (SWPP or SWPPP).

(a) If the site is covered under Ecology’s general NPDES permit for stormwater discharges associated with construction activities, the requirements of that permit shall be fully implemented to fulfill this requirement.

(b) All new development or redevelopment projects are responsible for preventing erosion and discharge of sediment and other pollutants into receiving waters. A Construction Stormwater Pollution Prevention Plan (SWPPP) is required for all projects which meet the thresholds in DMC 22.01.100 and 22.01.110. The SWPPP shall be implemented beginning with initial soil disturbance and until final stabilization.

(c) Sediment and erosion control BMPs shall be consistent with the BMPs contained in Chapters 3 and 4 of Volume II of the Stormwater Management Manual for Western Washington and/or other equivalent BMPs contained in technical stormwater manuals approved by the Department of Ecology.

(d) From October 1st through April 30th, clearing, grading and other soil disturbing activities may only be authorized by the City if silt-laden runoff will be prevented from leaving the site through a combination of the following:

(1) Site conditions including existing vegetative coverage, slope, soil type and proximity to receiving waters; and

(2) Limitations on activities and the extent of disturbed areas; and

(3) Proposed erosion and sediment control measures.

(e) Based on information provided and/or local weather conditions, the City may expand or restrict the seasonal limitation on site disturbance. The following activities are exempt from the seasonal clearing and grading limitations:

(1) Routine maintenance and necessary repair of erosion and sediment control BMPs;

(2) Routine maintenance of public facilities or existing utility structures that do not expose the soil or result in the removal of the vegetative cover to soil; and

(3) Activities where there is 100 percent infiltration of surface water runoff within the site in approved and installed erosion and sediment control facilities.

(f) The construction site operator shall include each of the 12 elements below in the SWPPP and ensure that they are implemented unless site conditions render the element unnecessary and the exemption from that element is clearly justified in the SWPPP. The SWPPP shall include both narrative and drawings. All BMPs shall be clearly referenced in the narrative and marked on the drawings. The SWPPP narrative shall include documentation to explain and justify the pollution prevention decisions made for the project.

(1) Element One--Preserve Vegetation/Mark Clearing Limits.

(A) Prior to beginning land disturbing activities, including clearing and grading, clearly mark all clearing limits, sensitive areas and their buffers, and trees that are to be preserved within the construction area.

(B) The duff layer, native top soil, and natural vegetation shall be retained in an undisturbed state to the maximum degree practicable.

(2) Element Two--Establish Construction Entrance.

(A) Construction vehicle access and exit shall be limited to one route, if possible.

(B) Access points shall be stabilized with quarry spalls, crushed rock or other equivalent BMP to minimize the tracking of sediment onto public roads.

(C) Wheel wash or tire baths shall be located on site, if stabilized construction entrance is not effective in preventing sediment from being tracked onto public roads.

(D) If sediment is tracked off site, affected roads shall be cleaned thoroughly at the end of each day, or more frequently during wet weather. Sediment shall be removed from roads by shoveling or pickup sweeping and shall be transported to a controlled sediment disposal area.

(E) Street washing is allowed only after sediment is removed per subsection (f)(2)(D) of this section. Street wash wastewater shall be controlled by pumping back on site or otherwise be prevented from discharging into systems tributary to waters of the State.

(3) Element Three--Control Flow Rates.

(A) Properties and waterways downstream from development sites shall be protected from erosion due to increases in the velocity and peak volumetric flow rate of stormwater runoff from the project site.

(B) Where necessary to comply with subsection (f)(3)(A) of this section, stormwater retention or detention facilities shall be constructed as one of the first steps in grading. Detention facilities shall be functional prior to construction of site improvements (e.g., impervious surfaces).

(C) If permanent infiltration ponds are used for flow control during construction, these facilities should be protected from siltation during the construction phase.

(4) Element Four--Install Sediment Controls.

(A) Stormwater runoff from disturbed areas shall pass through a sediment pond, or other appropriate sediment removal BMP, prior to leaving a construction site or prior to discharge to an infiltration facility. Runoff from fully stabilized areas may be discharged without a sediment removal BMP, but shall meet the flow control performance standard of subsection (F)(3)(a) of this section.

(B) Sediment control BMPs (sediment ponds, traps, filters, etc.) shall be constructed as one of the first steps in grading. These BMPs shall be functional before other land disturbing activities take place.

(C) BMPs intended to trap sediment on site shall be located in a manner to avoid interference with the movement of juvenile salmonids attempting to enter off-channel areas or drainages.

(5) Element Five--Stabilize Soils.

(A) Exposed and unworked soils shall be stabilized by application of effective BMPs that prevent erosion.

(B) No soil should remain exposed and unworked for more than the time periods set forth below to prevent erosion:

(i) During the dry season (May 1st through September 30th): seven days.

(ii) During the wet season (October 1st through April 30th): two days.

(iii) Soils shall be stabilized at the end of the shift before a holiday or weekend if needed based on the weather forecast.

(iv) Soil stockpiles must be stabilized from erosion, protected with sediment trapping measures, and, where possible, be located away from storm drain inlets, waterways and drainage channels.

(6) Element Six--Protect Slopes.

(A) Design and construct cut and fill slopes in a manner that will minimize erosion.

(B) Off-site stormwater (run-on) or groundwater shall be diverted away from slopes and undisturbed areas with interceptor dikes, pipes and/or swales. Off-site stormwater should be managed separately from stormwater generated on the site.

(C) At the top of slopes, collect drainage in pipe slope drains or protected channels to prevent erosion. Temporary pipe slope drains shall handle the expected peak 10-minute flow velocity from a Type 1A, 10-year, 24-hour frequency storm for the developed condition. Alternatively, the 10-year, one-hour flow rate predicted by an approved continuous runoff model, increased by a factor of 1.6, may be used. The hydrologic analysis shall use the existing land cover condition for predicting flow rates from tributary areas outside the project limits. For tributary areas on the project site, the analysis shall use the temporary or permanent project land cover condition, whichever will produce the highest flow rates. If using the Western Washington Hydrology Model to predict flows, bare soil areas should be modeled as landscaped area.

(D) Excavated material shall be placed on the uphill side of trenches, consistent with safety and space considerations.

(E) Check dams shall be placed at regular intervals within constructed channels that are cut down a slope.

(7) Element Seven--Protect Drain Inlets.

(A) Storm drain inlets made operable during construction shall be protected so that stormwater runoff does not enter the conveyance system without first being filtered or treated to remove sediment.

(B) Inlet protection devices shall be cleaned or removed and replaced when sediment has filled one-third of the available storage (unless a different standard is specified by the product manufacturer).

(8) Element Eight--Stabilize Channels and Outfalls:

(A) All temporary on-site conveyance channels shall be designed, constructed, and stabilized to prevent erosion from the following expected peak flows. Channels shall handle the expected peak 10-minute flow velocity from a Type 1A, 10-year, 24-hour frequency storm for the developed condition. Alternatively, the 10-year, one-hour flow rate predicted by an approved continuous runoff model, increased by a factor of 1.6, may be used. The hydrologic analysis shall use the existing land cover condition for predicting flow rates from tributary areas outside the project limits. For tributary areas on the project site, the analysis shall use the temporary or permanent project land cover condition, whichever will produce the highest flow rates. If using the Western Washington Hydrology Model to predict flows, bare soil areas should be modeled as “landscaped area.”

(B) Stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes, and downstream reaches shall be provided at the outlets of all conveyance systems.

(9) Element Nine--Control Pollutants.

(A) All pollutants, including waste materials and demolition debris, that occur on site shall be handled and disposed of in a manner that does not cause contamination of stormwater.

(B) Cover, containment, and protection from vandalism shall be provided for all chemicals, liquid products, petroleum products, and other materials that have the potential to pose a threat to human health or the environment. On-site fueling tanks shall include secondary containment.

(C) Maintenance, fueling and repair of heavy equipment and vehicles shall be conducted using spill prevention and control measures. Contaminated surfaces shall be cleaned immediately following any spill incident.

(D) Wheel wash or tire bath wastewater shall be discharged to a separate on-site treatment system or to the sanitary sewer with local sewer district approval.

(E) Application of fertilizers and pesticides shall be conducted in a manner and at application rates that will not result in loss of chemical to stormwater runoff. Manufacturers’ label requirements for application rates and procedures shall be followed.

(F) BMPs shall be used to prevent or treat contamination of stormwater runoff by pH-modifying sources. These sources include, but are not limited to: bulk cement, cement kiln dust, fly ash, new concrete washing and curing waters, waste streams generated from concrete grinding and sawing, exposed aggregate processes, dewatering concrete vaults, concrete pumping and mixer washout waters. Construction site operators are required to adjust the pH of stormwater if necessary to prevent violations of water quality standards.

(G) Construction site operators are required to obtain written approval from the City prior to using chemical treatment other than CO2 or dry ice to adjust pH.

(10) Element 10--Control Dewatering.

(A) Foundation, vault, and trench dewatering water, which has similar characteristics to stormwater runoff at the site, shall be discharged into a controlled conveyance system prior to discharge to a sediment trap or sediment pond.

(B) Clean, nonturbid dewatering water, such as well-point groundwater, can be discharged to systems tributary to, or directly into, surface waters of the State, as specified in subsection (f)(8) of this section, provided the dewatering flow does not cause erosion or flooding of receiving waters. Clean dewatering water should not be routed through stormwater sediment ponds.

(i) Infiltration;

(ii) Transport off site in vehicle, such as a vacuum flush truck, for legal disposal in a manner that does not pollute State waters;

(iii) On-site chemical treatment or other suitable treatment technologies approved by the City;

(iv) Sanitary sewer discharge with local sewer district approval, if there is no other option; or

(v) Use of a sedimentation bag with outfall to a ditch or swale for small volumes of localized dewatering.

(D) Highly turbid or contaminated dewatering water shall be handled separately from stormwater.

(11) Element 11--Maintain BMPs.

(A) All temporary and permanent erosion and sediment control BMPs shall be inspected, maintained and repaired as needed to assure continued performance of their intended function in accordance with BMP specifications.

(B) All temporary erosion and sediment control BMPs shall be removed within 30 days after final site stabilization is achieved or after the temporary BMPs are no longer needed.

(12) Element 12--Manage the Project.

(A) Development projects shall be phased to the maximum degree practicable and shall take into account seasonal work limitations.

(B) Construction site operators are required to maintain, and repair as needed, all sediment and erosion control BMPs to assure continued performance of their intended function.

(C) Construction site operators are required to periodically inspect their sites. Site inspections shall be conducted by a certified erosion and sediment control lead who shall be identified in the SWPPP and shall be present on site or on call at all times.

(D) Construction site operators are required to maintain, update and implement their SWPPP. Construction site operators are required to modify their SWPPP whenever there is a change in design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the State. Such modifications shall be submitted and approved by the City prior to implementation. (Ord. 10-894 § 1).

22.01.230 Minimum Requirement No. 3--Source control of pollution.

All known, available and reasonable source control BMPs are required for all projects. Source control BMPs must be selected, designed and maintained in accordance with Volume IV of the Stormwater Management Manual for Western Washington or an approved equivalent manual approved by the Department of Ecology. (Ord. 10-894 § 1).

22.01.240 Minimum Requirement No. 4--Preservation of natural drainage systems and outfalls.

Natural drainage patterns shall be maintained and discharges from the project site shall occur at the natural location, to the maximum extent practicable. The manner by which runoff is discharged from the project site must not cause a significant adverse impact to downstream receiving waters and down gradient properties. All outfalls require energy dissipation. (Ord. 10-894 § 1).

22.01.250 Minimum Requirement No. 5--On-site stormwater management.

On-site stormwater management BMPs are required to infiltrate, disperse, and retain stormwater runoff on‑site to the maximum extent feasible without causing flooding or erosion impacts. Runoff Downspout Control BMPs, functionally equivalent to those described in Chapter 3 of Volume III of the Stormwater Management Manual for Western Washington (2005), and Dispersion and Soil Quality BMPs, functionally equivalent to those in Chapter 5 of Volume V of the Stormwater Management Manual for Western Washington (2005) shall be required to reduce the hydrologic disruption of developed sites. (Ord. 10-894 § 1).

22.01.260 Minimum Requirement No. 6--Runoff treatment.

(a) Project Thresholds. The following require construction of stormwater treatment facilities:

(1) Projects in which the total of effective, pollution-generating impervious surface (PGIS) is 5,000 square feet or more in a threshold discharge area of the project; or

(2) Projects in which the total of pollution-generating pervious surface (PGPS) is three-quarters of an acre or more in a threshold discharge area, and from which there is a surface discharge in a natural or manmade conveyance system from the site.

(b) Treatment Type Thresholds.

(1) Oil Control. Treatment to achieve oil control applies to projects that have high-use sites. “High-use sites” are those that typically generate high concentrations of oil due to high traffic turnover or the frequent transfer of oil. “High-use sites” include:

(A) An area of commercial or industrial site subject to an expected average daily traffic (ADT) count equal to or greater than 100 vehicles per 1,000 square feet of gross building area;

(B) An area of a commercial or industrial site subject to petroleum storage and transfer in excess of 1,500 gallons per year, not including routinely delivered heating oil;

(C) An area of a commercial or industrial site subject to parking, storage or maintenance of 25 or more vehicles that are over 10 tons gross weight (trucks, buses, trains, heavy equipment, etc.);

(D) A road intersection with a measured ADT count of 25,000 vehicles or more on the main roadway and 15,000 vehicles or more on any intersecting roadway, excluding projects proposing primarily pedestrian or bicycle use improvements.

(2) Enhanced Treatment. Enhanced treatment for reduction in dissolved metals is required for the following project sites that discharge directly to fish-bearing streams, lakes, or to waters or conveyance systems tributary to fish-bearing streams or lakes: industrial project sites, commercial project sites, multifamily project sites, and high AADT roads as follows: fully controlled and partially controlled limited access highways with annual average daily traffic (AADT) counts of 15,000 or more and all other roads with an AADT of 7,500 or greater. However, such sites listed above that discharge directly (or indirectly through a municipal storm sewer system) to basic treatment receiving waters (Appendix I-C of the Stormwater Management Manual for Western Washington (2005)), and areas of the above-listed project sites that are identified as subject to basic treatment requirements, are also not subject to enhanced treatment requirements. For developments with a mix of land use types, the enhanced treatment requirement shall apply when the runoff from the areas subject to the enhanced treatment requirement comprises 50 percent or more of the total runoff within a threshold discharge area.

(3) Basic Treatment. Basic treatment generally applies to:

(A) Project sites that discharge to the ground, unless:

(i) The soil suitability criteria for infiltration treatment are met; or

(ii) The project uses infiltration strictly for flow control, not treatment, and the discharge is within one-quarter mile of a fish-bearing stream, or a lake;

(B) Residential projects;

(C) Project sites discharging directly to salt waters, river segments, and lakes listed in Appendix I-C of the Stormwater Management Manual for Western Washington (2005);

(D) Project sites that drain directly to streams that are not fish-bearing, or to waters not tributary to fish-bearing streams; and

(E) Landscaped areas of industrial, commercial, and multifamily project sites, and parking lots of industrial and commercial project sites that do not involve pollution-generating sources (e.g., industrial activities, customer parking, storage of erodible or leachable material, wastes or chemicals) other than parking of employees’ private vehicles. For developments with a mix of land use types, the basic treatment requirement shall apply when the runoff from the areas subject to the basic treatment requirement comprises 50 percent or more of the total runoff within a threshold discharge area.

(c) Treatment Facility Sizing. “Water quality design storm volume” means the volume of runoff predicted from a 24-hour storm with a six-month return frequency (a.k.a., six-month, 24-hour storm). Wetpool facilities are sized based upon the volume of runoff predicted through use of the Natural Resource Conservation Service curve number equations in Chapter 2 of Volume III of the Stormwater Management Manual for Western Washington (2005), for the six-month, 24-hour storm. Alternatively, the 91st percentile, 24-hour runoff volume indicated by an approved continuous runoff model may be used.

(d) Water Quality Design Flow Rate.

(1) Preceding detention facilities or when detention facilities are not required: the flow rate at or below which 91 percent of the runoff volume, as estimated by an approved continuous runoff model, will be treated. Design criteria for treatment facilities are assigned to achieve the applicable performance goal at the water quality design flow rate (e.g., 80 percent TSS removal).

(2) Downstream of detention facilities: the water quality design flow rate must be the full two-year release rate from the detention facility. Alternative methods may be used if they identify volumes and flow rates that are at least equivalent. That portion of any development project in which the above PGIS or PGPS thresholds are not exceeded in a threshold discharge area shall apply on-site stormwater management BMPs in accordance with Minimum Requirement No. 5.

(e) Treatment Facility Selection, Design and Maintenance. Stormwater facilities shall be:

(1) Selected in accordance with the process identified in Chapter 4 of Volume I of the Stormwater Management Manual for Western Washington (2005);

(2) Designed in accordance with the design criteria in Volume V of the Stormwater Management Manual for Western Washington (2005); and

(3) Maintained in accordance with the maintenance schedule in Volume V of the Stormwater Management Manual for Western Washington (2005).

(f) Additional Requirements. The discharge of untreated stormwater from pollution-generating impervious surfaces to groundwater is not authorized, except for the discharge achieved by infiltration or dispersion of runoff from residential sites through the use of on-site stormwater management BMPs. (Ord. 10-894 § 1).

22.01.270 Minimum Requirement No. 7--Flow control.

(a) Applicability. All projects are required to provide flow control to reduce the impacts of stormwater runoff from impervious surfaces and land cover conversions. The requirement below applies to projects that discharge stormwater directly, or indirectly through a conveyance system, into fresh water.

(1) Flow control is not required for projects that discharge directly, or indirectly through an MS4, to a water listed in Appendix I-E of the Stormwater Management Manual for Western Washington (2005) subject to the following restrictions:

(A) Direct discharge to the exempt receiving water does not result in the diversion of drainage from any perennial stream classified as Type 1, 2, 3, or 4 in the State of Washington Interim Water Typing System, or Types “S,” “F,” or “Np” in the Permanent Water Typing System, or from any Category I, II, or III wetland; and

(B) Flow-splitting devices or drainage BMPs are applied to route natural runoff volumes from the project site to any downstream Type 5 stream or Category IV wetland:

(i) Design of flow-splitting devices or drainage BMPs will be based on continuous hydrologic modeling analysis. The design will assure that flows delivered to Type 5 stream reaches will approximate, but in no case exceed, durations ranging from 50 percent of the two-year to the 50-year peak flow; and

(ii) Flow-splitting devices or drainage BMPs that deliver flow to Category IV wetlands will also be designed using continuous hydrologic modeling to preserve preproject wetland hydrologic conditions unless specifically waived or exempted by regulatory agencies with permitting jurisdiction; and

(C) The project site must be drained by a conveyance system that is comprised entirely of manmade conveyance elements (e.g., pipes, ditches, outfall protection, etc.) and extends to the ordinary high water line of the exempt receiving water; and

(D) The conveyance system between the project site and the exempt receiving water shall have sufficient hydraulic capacity to convey discharges from future build-out conditions (under current zoning) of the site, and the existing condition from nonproject areas from which runoff is or will be collected; and

(E) Any erodible elements of the manmade conveyance system must be adequately stabilized to prevent erosion under the conditions noted above.

If the discharge is to a stream that leads to a wetland, or to a wetland that has an outflow to a stream, both this minimum requirement (Minimum Requirement No. 7) and Minimum Requirement No. 8 apply.

(b) Thresholds. The following require construction of flow control facilities and/or land use management BMPs that will achieve the standard flow control requirement for Western Washington:

(1) Projects in which the total of effective impervious surfaces is 10,000 square feet or more in a threshold discharge area; or

(2) Projects that convert three-quarters acre or more of native vegetation to lawn or landscape, or convert two and one-half acres or more of native vegetation to pasture in a threshold discharge area, and from which there is a surface discharge in a natural or manmade conveyance system from the site; or

(3) Projects that through a combination of effective impervious surfaces and converted pervious surfaces and converted pervious surfaces cause a 0.1 cubic feet per second increase in the 100-year flow frequency from a threshold discharge area as estimated using the Western Washington Hydrology Model or other approved model.

(4) That portion of any development project in which the above thresholds are not exceeded in a threshold discharge area shall apply on‑site stormwater management BMPs in accordance with Minimum Requirement No. 5.

(c) Standard Flow Control Requirement. Stormwater discharges shall match developed discharge durations to predeveloped durations for the range of predeveloped discharge rates from 50 percent of the two-year peak flow up to the full 50-year peak flow. The predeveloped condition to be matched shall be a forested land cover unless:

(1) Reasonable, historic information is available that indicates the site was prairie prior to settlement (modeled as “pasture” in the Western Washington Hydrology Model); or

(2) The drainage area of the immediate stream and all subsequent downstream basins had at least 40 percent total impervious area since 1985. In this case, the predeveloped condition to be matched shall be the existing land cover condition. Where basin-specific studies determine a stream channel to be unstable, even though the above criterion is met, the predeveloped condition assumption shall be the “historic” land cover condition, or a land cover condition commensurate with achieving a target flow regime identified by an approved basin study.

(3) This standard requirement is waived for sites that will reliably infiltrate all the runoff from impervious surfaces and converted pervious surfaces.

(d) Western Washington Alternative Requirement. An alternative requirement may be established through application of watershed-scale hydrological modeling and supporting field observations. Possible reasons for an alternative flow control requirement include:

(1) Establishment of a stream-specific threshold of significant bedload movement other than the assumed 50 percent of the two-year peak flow;

(2) Zoning and land clearing ordinance restrictions that, in combination with an alternative flow control standard, maintain or reduce the naturally occurring erosive forces on the stream channel; or

(3) A duration control standard is not necessary for protection, maintenance, or restoration of designated beneficial uses or Clean Water Act compliance.

(e) Additional Requirement. Flow control BMPs shall be selected, designed, and maintained in accordance with Volume III of the Stormwater Management Manual for Western Washington (2005) or an equivalent. (Ord. 10-894 § 1).

22.01.280 Minimum Requirement No. 8--Wetlands protection.

(a) Applicability. The requirements below apply only to projects whose stormwater discharges into a wetland, either directly or indirectly through a conveyance system. These requirements must be met in addition to meeting Minimum Requirement No. 6--Runoff treatment.

(b) Thresholds. The thresholds identified in Minimum Requirement No. 6--Runoff Treatment, and Minimum Requirement No. 7--Flow Control, shall also be applied for discharges to wetlands.

(c) Standard Requirement. Discharges to wetlands shall maintain the hydrologic conditions, hydrophytic vegetation, and substrate characteristics necessary to support existing and designated uses. The hydrologic analysis shall use the existing land cover condition to determine the existing hydrologic conditions unless directed otherwise by a regulatory agency with jurisdiction. A wetland can be considered for hydrologic modification and/or stormwater treatment in accordance with Guide Sheet 1B in Appendix 1-D of the Stormwater Management Manual for Western Washington (2005).

(d) Additional Requirements.

(1) Stormwater treatment and flow control facilities shall not be built within a natural vegetated buffer, except for:

(A) Necessary conveyance systems as approved by the City; or

(B) As allowed in wetlands approved for hydrologic modification and/or treatment in accordance with Guidesheet 1B in Appendix 1-D of the Stormwater Management Manual for Western Washington (2005).

(2) An adopted and implemented basin plan may be used to develop requirements for wetlands that are tailored to a specific basin. (Ord. 10-894 § 1).

22.01.290 Minimum Requirement No. 9--Operation and maintenance.

An operation and maintenance manual that is consistent with the provisions in Volume V of the Stormwater Management Manual for Western Washington (2005) is required for all proposed stormwater facilities and BMPs. The party (or parties) responsible for maintenance and operation shall be identified in the operation and maintenance manual. For private facilities, a copy of the manual shall be retained on site or within reasonable access of the site, and shall be transferred with the property to the new owner. For public facilities, a copy of the manual shall be retained in the appropriate department. A log of maintenance activity that indicates what actions were taken shall be kept and be available for inspection by the City. (Ord. 10-894 § 1).

22.01.295 Financial liability.

Performance bonding or other appropriate financial instruments shall be required as determined necessary by the City to ensure compliance with these standards. (Ord. 10-894 § 1).

22.01.300 Maintenance agreement.

(a) Upon completion of project construction and prior to the final approval of any clearing, filling or grading, civil construction or building permit for which a storm drainage plan is required, the City shall require the applicant or owner to execute an inspection and maintenance agreement binding on all subsequent owners of land served by the private storm drainage system. Such agreement shall provide for access to the system at reasonable times for regular inspection by the City or its authorized representative and for regular or special assessments of property owners to ensure that the facility is maintained in proper working condition to meet design standards and any provisions established.

(b) The agreement shall be recorded by the applicant and/or owner in the land records of Pierce County.

(c) The agreement shall also provide that, if after notice by the City to correct a violation requiring maintenance work, satisfactory corrections are not made by the owner(s) within a reasonable period of time (30 days maximum), the City may perform all necessary work to place the facility in proper working condition. The owner(s) of the facility shall be assessed the cost of the work and any penalties and there shall be a lien on the property, which may be placed on the tax bill and collected as ordinary taxes by the City. (Ord. 10-894 § 1).

22.01.310 Maintenance responsibility.

(a) The owner of the property on which work has been done pursuant to these regulations for private storm drainage systems, or any other person or agent in control of such property, shall maintain in good condition and promptly repair and restore all grade surfaces, walls, drains, dams and structures, vegetation, erosion and sediment control measures, BMPs, and other protective devices. Such repairs or restorations and maintenance shall be in accordance with approved plans.

(b) An operation and maintenance schedule shall be developed for any storm drainage system and shall state the required maintenance to be performed, the equipment and skill level necessary to perform the maintenance, and the required frequency of maintenance. The operation and maintenance schedule shall either be printed on the Stormwater Site Plan, SWPPP or submitted under separate cover.

(c) The maintenance and operation of a private storm drainage system shall be the responsibility of the property owner. Furthermore, the property owner shall, in accordance with the operation and maintenance schedule, record and log maintenance performed and date. Operation and maintenance records shall be retained by the property owner for a minimum of three years and shall be available to the City for inspection at all reasonable times.

(d) The City shall be responsible for the maintenance and operation of all public storm drainage facilities located within public easements and rights-of-way following the completion of the successful maintenance period and the acceptance of such facilities by the City.

(e) Maintenance of stormwater facilities shall be performed to the maintenance standards specified in Chapter 4 of Volume V of the latest edition of the Stormwater Management Manual for Western Washington. Unless there are circumstances beyond the City’s control, when an inspection identifies an exceedence of the maintenance standard, maintenance shall be performed:

(1) Within one year for typical maintenance of facilities, except catch basins.

(2) Within six months for catch basins.

(3) Within two years for maintenance that requires capital construction of less than $25,000.

Circumstances beyond the City’s control include denial or delay of access by property owners, denial or delay of necessary permit approvals, and unexpected reallocations of maintenance staff to perform emergency work. For each exceedence of the required time frame, the City shall document the circumstances and how it was beyond their control. (Ord. 10-894 § 1).

22.01.320 Administration.

The Director shall have the authority to develop and implement administrative procedures to administer and enforce this chapter. (Ord. 10-894 § 1).

22.01.330 Review and approval.

The Director may approve, conditionally approve or deny an application for activities regulated by this chapter. (Ord. 10-894 § 1).

22.01.340 Inspection.

All activities regulated by this chapter, except those exempt in DMC 22.01.080, shall be subject to inspection by the Director or his/her designee. The Director or his/her designee is authorized to inspect projects at various stages of the work requiring approval to determine that adequate control is being exercised. Stages of work requiring inspection include, but are not limited to, preconstruction; installation of BMPs; land disturbing activities; installation of utilities, landscaping, and retaining walls; and completion of project. When required by the Director or his/her designee, a special inspection and/or testing shall be performed. (Ord. 10-894 § 1).

22.01.350 Fees.

The City’s fee for review of plans for storm drainage and erosion control facilities and on-site inspection of facilities during construction or for the purposes of investigating illicit discharges shall be based on actual costs incurred by the City plus administrative fees, where applicable. If such fees are not paid when due, the Director, or his/her designee, may revoke or refuse to grant the underlying permit or approval. If as a result of such action work is not completed, the Director, or his/her designee, may judge the incomplete work to constitute a drainage problem subject to sanctions described in DMC 22.01.360 through 22.01.380. (Ord. 10-894 § 1).

22.01.360 Enforcement.

(a) Enforcement Authority. The Director shall have full power and authority of the Code Enforcement Officer to enforce this chapter pursuant to the provisions of Chapter 1.17 DMC. For purposes of enforcement of this chapter, the cumulative monetary penalty set forth at DMC 1.17.110(a)(2)(i) shall be determined by the Director in accordance with subsection (b) of this section and the maximum penalty shall be $1,000 per day for each violation; provided, that monetary penalties imposed pursuant to a notice of violation are subject to the remission and mitigation provisions of DMC 22.01.380(d).

(b) General. Enforcement action shall be in accordance with this chapter whenever a person has violated any provision of this chapter. The choice of enforcement action and the severity of any penalty shall be based on the nature of the violation, the damage or threat to the public or to public resources, and/or the degree of bad faith of the person subject to the enforcement action. (Ord. 10-894 § 1).

22.01.370 Stop work/compliance order.

A stop work or compliance order issued by the Director pursuant to DMC 1.17.080 shall conform to the following provisions of this chapter.

The Director shall have the authority to issue and serve an owner, or person(s) representing an owner, with a stop work order if action is being undertaken in violation of this chapter, and shall further have the authority to issue a compliance order to maintain or repair a component of a stormwater facility or BMP to bring it in compliance with this chapter, the Stormwater Management Manual and/or other City regulations. The order shall include:

(a) Content of Order. The order shall contain:

(1) A description of the specific nature, extent, and time of violation and the damage or potential damage; and

(2) A notice that the violation or the potential violation cease and desist, and, in appropriate cases, the specific corrective action to be taken within a given time. A civil infraction citation or notice of violation under DMC 22.01.360 may be issued with the order.

(b) Notice. A stop work order shall be imposed by a notice in writing, either by certified mail with return receipt requested or by personal service, to the person incurring the same.

(c) Effective Date. The stop work order issued under this section shall become effective immediately upon receipt by the person to whom the order is directed.

(d) Compliance. Failure to comply with the terms of a stop work order shall result in enforcement actions including, but not limited to, the issuance of a civil penalty. (Ord. 10-894 § 1).

22.01.380 Violation.

(a) A person who fails to comply with the requirements of this chapter, who fails to conform to the terms of an approval or order issued, who undertakes new development without first obtaining City approval, or who fails to comply with a stop work or compliance order issued under this chapter, shall be subject to enforcement action pursuant to DMC 22.01.360.

(b) Separate Violations. Each day of continued violation or repeated violation shall constitute a separate violation.

(c) Aiding or Abetting. Any person who, through an act of commission or omission, aids or abets in the violation shall be considered to have committed a violation of this chapter.

(d) Application for Remission or Mitigation. Any person incurring a monetary penalty pursuant to issuance of a notice of violation may apply in writing within 10 days of receipt of the notice of violation to the City for remission or mitigation of the monetary penalty set forth in the notice of violation. Upon receipt of the application, the City may remit or mitigate the penalty only upon a demonstration of extraordinary circumstances, such as the presence of information or factors not considered in setting the original penalty. Filing an application for remission or mitigation shall not toll the time period set forth in Chapter 1.17 DMC to file an appeal of the notice of violation.

(e) Penalties Due. Penalties imposed under this chapter shall become due and payable 30 days after receiving the notice of civil infraction or notice of violation, unless application for remission or mitigation is made or an appeal is filed. Whenever an application for remission or mitigation is made, penalties shall become due and payable 30 days after receipt of the decision regarding the remission or mitigation. Whenever an appeal of a penalty is filed, the penalty shall become due and payable after all review proceedings and a final decision has been issued confirming all or part of the penalty. If the amount of a penalty owed the City is not paid within the time specified, the City may take actions necessary to recover such penalty.

(f) Penalties Recovered. Penalties recovered shall be paid to a specific budget line item account within the Utility Fund dedicated to enforcement and/or enhancement of the Stormwater Management Program. (Ord. 10-894 § 1).

22.01.390 Exceptions--Variances.

(a) The City may grant an adjustment or exception (variance) from the requirements of this chapter in accordance with the provisions of this section. In granting any modification, the City may prescribe conditions that are deemed necessary or desirable for the public interest.

(b) Adjustments to the Minimum Requirements may be granted; provided, that a written finding of fact is prepared that addresses the following:

(1) The adjustment provides substantially equivalent environmental protection; and

(2) Based on sound engineering practices, the objectives of safety, function, environmental protection and facility maintenance are met.

(c) Exceptions to the Minimum Requirements may be granted prior to permit approval and construction following legal public notice of an application for exception or variance, legal public notice of the decision of the application, and a written finding of fact is prepared that documents the determination to grant the exception. An application for exception must address the following:

(1) The exception provides equivalent environmental protection and is in the overriding public interest; and that the objectives of safety, function, environmental protection and facility maintenance, based upon sound engineering, are fully met;

(2) That there are special physical circumstances or conditions affecting the property such that the strict application of these provisions would deprive the applicant of all reasonable use of the parcel of land in question, and every effort to find creative ways to meet the intent of the minimum standards has been made;

(3) That the granting of the exception will not be detrimental to the public health and welfare, nor injurious to other properties in the vicinity and/or downstream, and to the quality of waters of the State; and

(4) The exception is the least possible exception that could be granted to comply with the intent of the Minimum Requirements.

(d) Prior Approval. Any adjustment or exception shall be approved prior to permit approval and construction.

(e) An exception may be granted by the City upon determination that the application of such requirements imposes a severe and unexpected economic hardship. The following documentation shall be provided by the project applicant to determine whether the application imposes a severe economic hardship:

(1) The current (preproject) use of the site; and

(2) How the application of the Minimum Requirement(s) restricts the proposed use of the site compared to the restrictions that existed prior to the adoption of the Minimum Requirements; and

(3) The possible remaining uses of the site if the exception were not granted; and

(4) The uses of the site that would have been allowed prior to the adoption of the Minimum Requirements; and

(5) A comparison of the estimated amount and percentage of value loss as a result of the Minimum Requirements versus the estimated amount and percentage of value as a result of requirements that existed prior to adoption of the Minimum Requirements; and

(6) The feasibility for the owner to alter the project to apply the Minimum Requirements.

(f) In addition any exception must meet the following criteria:

(1) The exception will not increase the risk to the public health and welfare, nor injurious to other properties in the vicinity and/or downstream, and to the quality of waters of the State; and

(2) The exception is the least possible exception that could be granted to comply with the intent of the Minimum Requirements.

(g) Duration of Exception. As applicable, the City shall specify the duration of an exception at the time of approval.

(h) Right of Appeal. All determinations of the City shall be final and conclusive, unless within 30 days of the date of the City determination the original applicant or an adverse party gives written notice to the City Council for review of the action. (Ord. 10-894 § 1).

Prior legislation: Ords. 514 and 09-885.