Chapter 13.02
STORMWATER MANAGEMENT

Sections:

13.02.010    Definitions.

13.02.020    Purpose.

13.02.030    General provisions.

13.02.040    Severability.

13.02.050    Applicability.

13.02.060    Inspection.

13.02.070    Administration.

13.02.090    Enforcement—Penalties.

13.02.100    Exceptions—Appeals.

13.02.120    Regulated activities and allowed activities.

13.02.130    General requirements.

13.02.140    Approval standards.

13.02.010 Definitions.

For the purpose of this chapter and Chapter 13.04, the following words or phrases have the meanings set forth herein, unless the context indicates otherwise:

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

“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 subbasins.

“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 earthy material on which fill is to be placed.

“Best management practice” or “BMP” means physical, structural, and/or managerial practices that, when used singly or in combination, prevent or reduce pollution of water. BMPs are listed and described in the manual.

“City” means the city of Shelton, Washington.

“City council” means the city council of the city of Shelton, Washington.

“City manager” means the city manager of the city of Shelton, Washington.

“Civil engineer” means a professional engineer licensed in the state of Washington in civil engineering who is experienced and knowledgeable in the practice of soils engineering.

“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 propped 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.

“Contiguous property” means land adjoining and touching other property held by the same ownership. Land divided by a public road or alley shall not be considered contiguous.

“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, geological 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.

“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.

“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 or rock fragments by water, wind, ice, or gravity.

“Excavation” means the mechanical removal of earth material.

“Existing site conditions” means:

1.    For developed sites with stormwater facilities that have been constructed to meet the standards in the minimum requirements of this manual, “existing site conditions” shall mean the existing conditions on the site.

2.    For developed sites that do not have stormwater facilities that meet the minimum requirements, “existing site conditions” shall mean the conditions that existed prior to local government adoption of a stormwater management program. If in question, the existing site conditions shall be documented by aerial photograph records or other appropriate means.

3.    For all sites in water quality sensitive areas identified under minimum requirement No. 7, Water Quality Sensitive Areas, of Section 13.02.140(B)(9), “existing site conditions” shall mean undisturbed forest, for the purpose of calculating runoff characteristics.

4.    For all undeveloped sites outside of water quality sensitive areas, “existing site conditions” shall mean the existing conditions on the site.

“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.    Precommercial thinning;

4.    Reforestation;

5.    Fertilization;

6.    Prevention and suppression of diseases and insects;

7.    Salvage of trees;

8.    Brush control.

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

“Geological 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” means the grade prior to grading.

2.    “Rough grade” means the stage at which the grade approximately conforms to the approved plan.

3.    “Finish grade” means the final grade of the site which conforms to the approved plan.

“Grade” also means to finish the surface of a canal bed or roadbed, top of embankment to 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.

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

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

“Illicit discharge” means all nonstormwater discharges to stormwater drainage systems that cause or contribute to a violation of state water quality, sediment quality or ground water quality standards, including but not limited to sanitary sewer connections, industrial process water, interior floor drains, car washing and greywater systems.

“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 or parking areas, patched 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.

“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 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.

“Large parcel erosion and sediment control plan” or “large parcel ESC plan” means a plan to implement BMPs to control pollution generated during land-disturbing activity. Guidance for preparing a large parcel ESC plan is contained in the manual.

“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.

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

“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 timber land to other uses; and subdivision and short subdivision of land as defined in RCW 58.17.020. All other forest practices and commercial agriculture are not considered new development.

“Permanent stormwater quality control (PSQC) plan” means a plan which includes permanent BMPs for the control of pollution from stormwater runoff after construction and/or land-disturbing activity has been completed. For small sites, this requirement is met by implementing a small parcel erosion and sediment control plan. Guidance on preparing a PSQC plan is contained in the manual.

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

“Pollution” means contamination or other alteration of the physical, chemical, or biological properties of waters of the state, including change in temperature, taste, color, turgidity, 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.

“Rainwater harvesting system” means a system that collects stormwater runoff from roofs and other impervious surface areas, resulting in zero surface water discharge for all storm events.

“Redevelopment” means, on an already developed site, the creation or addition of impervious surfaces, 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 subbasin. 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 detention facility is used to detain stormwater runoff from a number of different businesses, developments or areas within a catchment.

“Retention/detention facility (R/D)” or “retention/infiltration system” 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 portion of a piece of property which is directly subject to development.

“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 fifty percent slope. Expressed in degrees, the slope is the angle from the horizontal plane, with a ninety-degree slope being vertical (maximum) and forty-five degrees being a 1:1 or one hundred percent slope.

“Small parcel erosion and sediment control plan” or “small parcel ESC plan” means a plan for small sites to implement temporary BMPs to control pollution generated during the construction phase only, primarily erosion and sediment.

“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 BMP that is intended to prevent pollutants from entering stormwater. A few examples of source control BMPs are erosion control practices, maintenance of stormwater facilities, constructing roofs over storage and working areas, and directing wash water and similar discharges to the sanitary sewer or a dead-end sump.

“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 the 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, pits, swales, ditches, culverts, street gutters, detention basins, retention basins, constructed wetlands, infiltration devices, catchbasins, oil/water separators, sediment basins and modular pavement.

“Stormwater Management Manual” or “manual” means the manual adopted by reference and prepared by Ecology that contains BMPs to prevent or reduce pollution (or a technically equivalent manual approved by Ecology).

“Stormwater site plan” means a plan which includes an erosion and sediment control (ESC) plan and/or a permanent stormwater quality control plan (PSQCP). For small sites, this plan is the equivalent of a small parcel erosion and sediment control plan. Guidance on preparing a stormwater site plan is contained in the manual.

“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 exiting 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 ground water 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. This includes wetlands created, restored or enhanced as part of a mitigation procedure. This does not include constructed wetlands or the following surface waters of the state intentionally constructed from sites that are not wetlands: irrigation and drainage ditches, grass-lined swales, canals, agricultural detention facilities, farm ponds, and landscape amenities. (Ord. 1921-0518 (part), 2018; Ord. 1637-0305 § 1 (part), 2005: Ord. 1438-1295 (part), 1995)

13.02.020 Purpose.

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. It is the purpose of this chapter to:

A.    Minimize water quality degradation and sedimentation in streams, ponds, lakes, wetlands and other water bodies;

B.    Minimize the impact of increased runoff, erosion and sedimentation caused by land development and maintenance practices;

C.    Maintain and protect ground water resources;

D.    Minimize adverse impacts of alterations on ground and surface water quantities, locations and flow patterns;

E.    Decrease potential landslide, flood and erosion damage to public and private property;

F.    Promote site planning and construction practices that are consistent with natural topographical, vegetational and hydrological conditions;

G.    Maintain and protect the city stormwater management infrastructure and those downstream;

H.    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

I.    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 qualities of land, wetlands and water bodies. (Ord. 1637-0305 § 1 (part), 2005: Ord. 1438-1295 (part), 1995)

13.02.030 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. 1637-0305 § 1 (part), 2005: Ord. 1438-1295 (part), 1995)

13.02.040 Severability.

If any provision of this chapter or its application to any person, entity, or circumstance is held invalid, the remainder of this chapter or the application of the provision to other persons, entities, or circumstances shall not be affected. (Ord. 1637-0305 § 1 (part), 2005: Ord. 1438-1295 (part), 1995)

13.02.050 Applicability.

When any provision of any other chapter of this code conflicts with this chapter, that which provides more environmental protection shall apply unless specifically provided otherwise in this chapter.

A.    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: building permit, commercial or residential; binding site plan; conditional use permit; right-of-way construction permit; grading and clearing permit; planned unit development; right-of-way permit; shoreline substantial development permit; shoreline variance; shoreline conditional use permit; shoreline environmental redesignation; unclassified use permit; variance; zone reclassification; subdivision; short subdivision; special use permit; utility and other use permit; zone reclassification; or any subsequently adopted permit or required approval not expressly exempted by this chapter.

B.    Regulated activities shall be conducted only after the city approves a stormwater site plan which includes one or more of the following as required by this chapter:

1.    Small parcel erosion and sediment control plan.

2.    Large parcel erosion and sediment control plan.

3.    Permanent stormwater quality control (PSQC) plan. (Ord. 1637-0305 § 1 (part), 2005: Ord. 1438-1295 (part), 1995)

13.02.060 Inspection.

Duly authorized and properly identified city employees shall have the right to access any person’s property at all reasonable times for the purpose of ensuring conformity to this chapter. All activities regulated by this chapter, except those exempted within this chapter, shall be inspected by the city. The city shall 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, retaining walls and completion of a project. When required by the city, special inspection and/or testing shall be performed and the cost shall be charged to the developing person or persons. (Ord. 1637-0305 § 1 (part), 2005: Ord. 1438-1295 (part), 1995)

13.02.070 Administration.

The regulation of this chapter shall be under the supervision of the city manager; provided, however, that the city manager may delegate the duty of enforcing the provisions of this chapter to other designees. The city manager or designee may adopt written procedures for the purpose of carrying out the provisions of this chapter; provided, that said determinations are not contrary to this chapter. (Ord. 1921-0518 (part), 2018; Ord. 1637-0305 § 1 (part), 2005: Ord. 1438-1295 (part), 1995)

13.02.090 Enforcement—Penalties.

A.    Stop Work Order. The city shall have the authority to serve a person a stop work order if an action is being undertaken in violation of this chapter.

1.    The order shall contain, but not be limited to, the following:

a.    A description of the specific nature, extent, and time of violation and the damage or potential damage; and

b.    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.

2.    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.

3.    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.

B.    Criminal Penalty. Any person who willfully violates, disobeys, omits, neglects or refuses to comply with or resists the enforcement of this chapter or its provisions shall be deemed guilty of a misdemeanor and upon conviction thereof shall be punished by a fine of not in excess of one thousand dollars or by imprisonment in the jail for not to exceed ninety days or by both such fine and imprisonment. Each day that a violation exists shall constitute a separate offense.

C.    Civil Penalty. In addition to the foregoing criminal remedy, the violation of any of the provisions of this chapter may be deemed by the city to be a nuisance and threatening to the health and safety of the citizens of Shelton. The city may utilize any civil remedy available to it under the laws of the state of Washington to enforce these provisions, including injunctive relief. Furthermore, any person violating any of the provisions of this chapter may become liable to the city for any direct or indirect expense, loss or damage occasioned the city by reason of such violation. (Ord. 1637-0305 § 1 (part), 2005: Ord. 1438-1295 (part), 1995)

13.02.100 Exceptions—Appeals.

A.    Exceptions. After a public hearing, the city councilmembers may grant an exception from the requirements of this chapter. In granting any exception, the city council may prescribe conditions that are deemed necessary or desirable for the public interest. Exceptions may be granted prior to permit approval and construction. An exception may be granted following a public hearing; provided, that a written finding of fact is prepared that addresses 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.

B.    Any exception shall be approved prior to permit approval and construction.

C.    Exceptions granted shall be valid for two years, unless granted for a shorter period.

D.    All actions of the city councilmember shall be final and conclusive, unless appealed to superior court as provided for in state law. (Ord. 1921-0518 (part), 2018; Ord. 1637-0305 § 1 (part), 2005: Ord. 1438-1295 (part), 1995)

13.02.120 Regulated activities and allowed activities.

A.    Regulated Activities. Consistent with the minimum requirements contained in this chapter, the city shall approve or disapprove the following activities, unless exempted within this section:

1.    New Development.

a.    Land-disturbing activities.

b.    Structural development, including construction; installation or expansion of a building or other structure.

c.    Creation of impervious surfaces.

d.    Class IV general forest practices that are conversions from timber land to other uses.

e.    Subdivision, short subdivision and binding site plans, as defined in RCW 58.17.020.

2.    Redevelopment.

a.    On an already developed site, the creation or addition of impervious surfaces, 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, and land-disturbing activities with structural or impervious redevelopment.

B.    Exemptions. The following are exempt from the provisions of this chapter:

1.    Commercial agriculture, and forest practices regulated under WAC Title 222, except for Class IV general forest practices that are conversions from timber land to other uses.

2.    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. 1637-0305 § 1 (part), 2005: Ord. 1438-1295 (part), 1995)

13.02.130 General requirements.

A.    Stormwater Management Manual Adopted. The Department of Ecology 2005 Stormwater Management

Manual is adopted by reference and is hereinafter referred to as “the manual.”

B.    Stormwater Best Management Practices (BMPs).

1.    General. BMPs 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.

2.    Experimental BMPs. In those instances where appropriate BMPs are not in the manual, experimental BMPs should be considered. Experimental BMPs are encouraged as means of solving problems in a manner not addressed by the manual in an effort to improve stormwater quality technology. Experimental BMPs must be approved in accordance with the approval process outlined in the manual.

C.    Illicit Discharges. Illicit discharges to stormwater drainage systems are prohibited. (Ord. 1726-0508 § 1, 2008: Ord. 1637-0305 § 1 (part), 2005: Ord. 1438-1295 (part), 1995)

13.02.140 Approval standards.

A.    Small parcel minimum requirements shall be as follows:

1.    The following new development shall be required to control erosion and sediment during construction, to permanently stabilize soil exposed during construction, and to comply with small parcel requirements Nos. 1 through 5 below:

a.    Individual, detached, single-family residences and duplexes.

b.    Creation or addition of less than five thousand square feet of impervious surface area.

c.    Land-disturbing activities of less than one acre.

2.    Compliance shall be demonstrated through the implementation of an approved small parcel erosion and sediment control plan.

3.    Small Parcel Requirement No. 1—Construction Access Route. Construction vehicle access shall be, whenever possible, limited to one route. Access points shall be stabilized with quarry spall or crushed rock to minimize the tracking of sediment onto public roads.

4.    Small Parcel Requirement No. 2—Stabilization of Denuded Area—Soil Stabilization. All exposed soils shall be stabilized by suitable application of BMPs, including but not limited to sod or other vegetation, plastic covering, mulching, or application of ground base on areas to be paved. All BMPs shall be selected, designed and maintained in accordance with an approved manual. From October 1st through April 30th, no soils shall remain exposed for more than two days. From May 1st through September 30th, no soils shall remain exposed for more than seven days.

5.    Small Parcel Requirement No. 3—Protection of Adjacent Properties. Adjacent properties shall be protected from sediment deposition by appropriate use of vegetative buffer strips, sediment barriers or filters, dikes or mulching, or by a combination of these measures and other appropriate BMPs.

6.    Small Parcel Requirement No. 4—Maintenance. All erosion and sediment control BMPs shall be regularly inspected and maintained to ensure continued performance of their intended function.

7.    Small Parcel Requirement No. 5—Other BMPs. As required by the city, other appropriate BMPs to mitigate the effects of increased runoff shall be applied.

B.    Large development minimum requirements shall be as follows:

1.    New Development.

a.    All new development that includes the creation or addition of five thousand square feet or greater of new impervious surface area and/or land-disturbing activity of one acre or greater shall comply with minimum requirements Nos. 1 thorough 11 in subsections (B)(3) through (B)(13) of this section.

i.    Compliance shall be demonstrated thorough the implementation of an approved stormwater site plan consisting of a large parcel ESC plan and a PSQC plan, as appropriate.

b.    All new development that includes the creation or addition of five thousand square feet or greater of new impervious surface area and land-disturbing activity of less than one acre shall comply with minimum requirements Nos. 2 through 11 in subsections (B)(4) through (B)(13) of this section and the small parcel minimum requirements found in subsection A of this section.

c.    Compliance shall be demonstrated through the implementation of an approved stormwater site plan that includes a small parcel erosion and sediment control plan and a PSQC plan.

d.    This section does not apply to the construction of individual, detached, single-family residences and duplexes. Those types of new development are included in the small parcel minimum requirements.

2.    Redevelopment minimum requirements shall be as follows:

a.    Where redevelopment of five thousand square feet or greater occurs:

i.    New development minimum requirements Nos. 1 thorough 11 in subsections (B)(3) through (B)(13) of this section shall apply to that portion of the site that is being redeveloped, and source control BMPs shall be applied to the entire site, including adjoining parcels if they are part of the project.

b.    In addition to the above requirements, where one or more of the following conditions apply, a stormwater management plan shall be prepared that includes a schedule for implementing the minimum requirements to the maximum extent practicable, for the entire site, including adjoining parcels if they are part of the project. An adopted and implemented basin plan (minimum requirement No. 9 in subsection (B)(11) of this section) may be used to develop redevelopment requirements that are tailored to a specific basin.

i.    Existing sites greater than one acre in size with fifty percent or more impervious surface.

ii.    Sites that discharge to a receiving water that has a documented water quality problem. Subject to local priorities, a documented water quality problem includes, but is not limited to, water bodies:

(A)    Listed in reports required under Section 305(b) of the Clean Water Act, and designated as not supporting beneficial uses;

(B)    Listed under Section 304(l)(1)(A)(i), 304(l)(1)(A)(ii), or 304(l)(1)(B) of the Clean Water Act as not expected to meet water quality standards or water quality goals;

(C)    Listed in Washington State’s Nonpoint Source Assessment required under Section 319(a) of the Clean Water Act that, without additional action to control nonpoint sources of pollution, cannot reasonably be expected to attain or maintain water quality standards.

iii.    Sites where the need for additional stormwater control measures has been identified through a basin plan, the watershed ranking process under Chapter 400-12 WAC, or through Growth Management Act planning.

3.    Minimum Requirement No. 1—Erosion and Sediment Control.

a.    All new development and redevelopment that includes land-disturbing activities of one acre or greater shall comply with erosion and sediment control requirements Nos. 1 through 14 in subsections (B)(3)(c)(i) through (xiv) of this section. Compliance with erosion and sediment control requirements shall be demonstrated through implementation of an approved large parcel erosion and sediment control plan.

b.    All new development and redevelopment that includes land-disturbing activities of one acre or greater shall comply with the small parcel minimum requirements found in subsection A of this section. Compliance with the small parcel requirements shall be demonstrated through implementation of a small parcel erosion and sediment control plan.

c.    The following erosion and sediment control requirements shall be met:

i.    Erosion and Sediment Control Requirement No. 1—Stabilization and Sediment Trapping. All exposed and unworked soils shall be stabilized by suitable application of BMPs. From October 1st to April 30th, no soils shall remain unstabilized for more than two days. From May 1st to September 30th, no soils shall remain unstabilized for more than seven days. Prior to leaving the site, stormwater runoff shall pass through a sediment pond or sediment trap, or other BMPs.

ii.    Erosion and Sediment Control Requirement No. 2—Delineate Clearing and Easement Limits. In the field, mark clearing limits and/or any easements, setbacks, sensitive/critical areas and their buffers, trees and drainage courses.

iii.    Erosion and Sediment Control Requirement No. 3—Protection of Adjacent Properties. Properties adjacent to the project site shall be protected from sediment deposition.

iv.    Erosion and Sediment Control Requirement No. 4—Timing and Stabilization of Sediment Trapping Measures. Sediment ponds and traps, perimeter dikes, sediment barriers, and other BMPs intended to trap sediment on-site shall be constructed as a first step in grading. These BMPs shall be functional before land-disturbing activities take place. Earthen structures such as dams, dikes, and diversions shall be seeded and mulched according to the timing indicated in erosion and sediment control requirement No. 1 in subsection (B)(3)(c)(i) of this section.

v.    Erosion and Sediment Control Requirement No. 5—Cut and Fill Slopes. Cut and fill slopes shall be designed and constructed in a manner that will minimize erosion. In addition, slopes shall be stabilized in accordance with erosion and sediment control requirement No. 1 in subsection (B)(3)(c)(i) of this section.

vi.    Erosion and Sediment Control Requirement No. 6—Controlling Off-Site Erosion. Properties and waterways downstream from development sites shall be protected from erosion due to increases in the volume velocity and peak flow rate of stormwater runoff from the project site.

vii.    Erosion and Sediment Control Requirement No. 7—Stabilization of Temporary Conveyance Channels and Outlets. All temporary on-site conveyance channels shall be designed, constructed and stabilized to prevent erosion from the expected velocity of flow from a two-year, twenty-four-hour frequency storm for the developed condition. Stabilization adequate to prevent erosion of outlets, adjacent streambanks, slopes and downstream reaches shall be provided at the outlets of all conveyance systems.

viii.    Erosion and Sediment Control Requirement No. 8—Storm Drain Inlet Protection. All storm drain inlets made operable during construction shall be protected so that stormwater runoff shall not enter the conveyance system without first being filtered or otherwise treated to remove sediment.

ix.    Erosion and Sediment Control Requirement No. 9—Underground Utility Construction. The construction of underground utility lines shall be subject to the following criteria:

(A)    Where feasible, no more than five hundred feet of trench shall be opened at one time.

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

(2)    Trench dewatering devices shall discharge into a sediment trap or sediment pond.

x.    Erosion and Sediment Control Requirement No. 10—Construction Access Routes. Wherever construction vehicle access routes intersect paved roads, provisions must be made to minimize the transport of sediment (mud) onto the paved road. If sediment is transported onto a road surface, the roads shall be cleaned thoroughly at the end of each day. Sediment shall be removed from roads by shoveling or sweeping and be transported to a controlled sediment disposal area. Street washing shall be allowed only after sediment is removed in this manner.

xi.    Erosion and Sediment Control Requirement No. 11—Removal of Temporary BMPs. All temporary erosion and sediment control BMPs shall be removed within thirty days after final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be removed or stabilized on-site. Disturbed soil areas resulting from removal shall be permanently stabilized.

xii.    Erosion and Sediment Control Requirement No. 12—Dewatering Construction Sites. Dewatering devices shall discharge into a sediment trap or sediment pond.

xiii.    Erosion and Sediment Control Requirement No. 13—Control of Pollutants Other Than Sediment on Construction Sites. All pollutants other than sediment that occur on-site during construction shall be handled and disposed of in a manner that does not cause contamination of stormwater.

xiv.    Erosion and Sediment Control Requirement No. 14—Maintenance. All temporary and permanent erosion and sediment control BMPs shall be maintained and repaired as needed to assure continued performance of their intended function. All maintenance and repair shall be conducted in accordance with an approved manual.

xv.    Erosion and Sediment Control Requirement No. 15—Financial Liability. Performance bonding, or other appropriate financial instruments, shall be required for all projects to ensure compliance with the approved erosion and sediment control plan.

4.    Minimum Requirement No. 2—Preservation of Natural Drainage Systems. Natural drainage patterns shall be maintained and discharges from the site shall occur at the natural location to the maximum practicable.

5.    Minimum Requirement No. 3—Source Control of Pollution.

a.    Source control BMPs shall be applied to all projects to the maximum extent practicable. Source control BMPs shall be selected, designed, and maintained according to an approved manual.

b.    An adopted and implemented basin plan (minimum requirement No. 9 in subsection (B)(11) of this section) may be used to develop source control requirements that are tailored to a specific basin; however, in all circumstances, source control BMPs shall be required for all sites.

6.    Minimum Requirement No. 4—Runoff Treatment BMPs.

a.    All projects shall provide treatment of stormwater. Treatment BMPs shall be sized to capture and treat the water quality design storm, defined as the six-month, twenty-four-hour return period storm. The first priority for treatment shall be to infiltrate as much as possible of the water quality design storm, only if site conditions are appropriate and ground water quality will not be impaired. Direct discharge of untreated stormwater to ground water is prohibited. All treatment BMPs shall be selected, designed, and maintained according to an approved manual.

b.    Stormwater treatment BMPs shall not be built within a natural vegetated buffer, except for necessary conveyance systems as approved by the local government.

c.    An adopted and implemented basin plan (minimum requirement No. 9 in subsection (B)(11) of this section) may be used to develop runoff treatment requirements that are tailored to a specific basin.

7.    Minimum Requirement No. 5—Streambank Erosion Control.

a.    The requirement below applies only to situations where stormwater runoff is discharged directly or indirectly to a stream, and must be met in addition to meeting the requirements of minimum requirement No. 4, runoff treatment BMPs, in subsection (B)(6) of this section:

i.    Stormwater discharges to streams shall control streambank erosion by limiting the peak rate of runoff from individual development sites to fifty percent of the existing condition two-year, twenty-four-hour design storm while maintaining the existing condition peak runoff rate for the ten-year, twenty-four-hour and one-hundred-year, twenty-four-hour design storms. As the first priority, streambank erosion control BMPs shall utilize infiltration to the fullest extent practicable, only if site conditions are appropriate and ground water quality is protected. Streambank erosion control BMPs shall be selected, designed, and maintained according to an approved manual.

b.    Stormwater treatment BMPs shall not be built within a natural vegetated buffer, except for necessary conveyance systems as approved by the local government.

c.    An adopted and implemented basin plan (minimum requirement No. 9 in subsection (B)(11) of this section) may be used to develop streambank erosion control requirements that are tailored to a specific basin.

8.    Minimum Requirement No. 6—Wetlands.

a.    The requirements below apply only to situations where stormwater discharges directly or indirectly through a conveyance system into a wetland, and must be met in addition to meeting the requirements in minimum standard No. 4, runoff treatment BMPs, in subsection (B)(6) of this section:

i.    Stormwater discharges to wetlands must be controlled and treated to the extent necessary to meet the State Water Quality Standards, Chapter 173-201 WAC, or Ground Water Quality Standards, Chapter 173-200 WAC, as appropriate.

ii.    Discharges to wetlands shall maintain the hydroperiod and flows of existing site conditions to the extent necessary to protect the characteristic uses of the wetland. Prior to discharging to a wetland, alternative discharge locations shall be evaluated, and natural water storage and infiltration opportunities outside the wetland shall be maximized.

iii.    Created wetlands that are intended to mitigate for loss of wetland acreage, function and value shall not be designed to also treat stormwater.

iv.    In order for constructed wetlands to be considered treatment systems, they must be constructed on sites that are not wetlands and they must be managed for stormwater treatment. If these systems are not managed and maintained in accordance with an approved manual for a period exceeding three years, these systems may no longer be considered constructed wetlands. Discharges from constructed wetlands to waters of the state (including discharges to natural wetlands) are regulated under Chapter 90.48 RCW and Chapters 173-200 and 173-201 WAC.

v.    Stormwater treatment BMPs shall not be built within a natural vegetated buffer, except for necessary conveyance systems as approved by the local government.

vi.    An adopted and implemented basin plan (minimum requirement No. 9 in subsection (B)(11) of this section) may be used to develop requirements for wetlands that are tailored to a specific basin.

9.    Minimum Requirement No. 7—Water Quality Sensitive Areas.

a.    Where the director determines that the minimum requirements do not provide adequate protection of water quality sensitive areas, either on-site or within the basin, more stringent controls shall be required by the director to protect water quality.

b.    Stormwater treatment BMPs shall not be built within a natural vegetated buffer, except for necessary conveyance systems as approved by the city.

c.    An adopted and implemented basin plan (minimum requirement No. 9 in subsection (B)(11) of this section) may be used to develop requirements for water quality sensitive areas that are tailored to a specific basin.

10.    Minimum Requirement No. 8—Off-Site Analysis and Mitigation. All development projects shall conduct an analysis of off-site water quality impacts resulting from the project and shall mitigate these impacts. The analysis shall extend a minimum of one-fourth of a mile downstream from the project. The existing or potential impacts to be evaluated and mitigated shall include, at a minimum, but not be limited to:

a.    Excessive sedimentation.

b.    Streambank erosion.

c.    Discharges to ground water contributing or recharge zones.

d.    Violations of water quality standards.

e.    Spills and discharges of priority pollutants.

11.    Minimum Requirement No. 9—Basin Planning. Adopted and implemented watershed-based basin plans may be used to modify any or all of the minimum requirements; provided, that the level of protection for surface or ground water achieved by the basin plan will equal or exceed that which would be achieved by the minimum requirements in the absence of a basin plan. Basin plans shall evaluate and include, as necessary, retrofitting of BMPs for existing development and/or redevelopment in order to achieve watershed-wide pollutant reduction goals. Standards developed from basin plans shall not modify any of the above requirements until the basin plan is formally adopted and fully implemented by the city. Basin plans shall be developed according to an approved manual.

12.    Minimum Requirement No. 10—Operation and Maintenance. An operation and maintenance schedule shall be provided for all proposed stormwater facilities and BMPs, and the party (or parties) responsible for maintenance and operation shall be identified.

13.    Minimum Requirement No. 11—Financial Liability. Performance bonding or other appropriate financial instruments shall be required for all projects to ensure compliance with these standards.

14.    Exceptions. Exceptions to minimum requirements Nos. 1 through 11 may be granted prior to permit approval and construction. An exception may be granted following a public hearing; provided, that a written finding of fact is prepared that addresses the following:

a.    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;

b.    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;

c.    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

d.    The exception is the least possible exception that could be granted to comply with the intent of the minimum requirements. (Ord. 1637-0305 § 1 (part), 2005: Ord. 1438-1295 (part), 1995)