HomeMy WebLinkAboutO-2476 - Repeals and replaces Ch. 14.15, on-site storm water drainage code (14.15)·'..
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CITY OF MARYSVILLE
Marysville,Washington
ORDINANCE NO.2 if7 {p
AN ORDINANCE OF THE CITY OF MARYSVILLE,WASHINGTON
REPEALING CHAPTER 14.15 (ON-SITE STORMWATER DRAINAGE CODE)
OF THE MARYSVILLE MUNICIPAL CODE AND ENACTING A NEW
CHAPTER 14.15 ON-SITE STORMWATER DRAINAGE CODE.
WHEREAS,the City Council of the City of Marysville adopted revisions to the City's on-
site stonnwater drainage code in 1999,that adopted by reference the latest edition of the State
Department of Ecology's Stonnwater Management Manual as the City's technical standards.
WHEREAS,the State Department of Ecology published a revised manual,entitled the
"Stormwater Management Manual for Western Washington"in August,2001, that resulted in
immediate and significant revisions to the City's stonnwater regulations,effective upon
publication of Ecology's manual,without any additional public notice,hearing or review by the
local legislative body; and
WHEREAS,the Marysville City Council deemed it appropriate to solicit additional
comment and review from agencies and public,and to commission City staff to promulgate
proposed revisions to the existing on-site stonnwater drainage code to provide consistency
between the Manual and the existing municipal code, as well as propose local revisions to the
Manual to address community concerns and priorities;and
WHEREAS,following a comprehensive review of the above-referenced Manual by City
staff, and the Marysville City Council,the proposed revisions were distributed to agencies and
the general public;and
WHEREAS,after providing notice to the public as required by law, on April 28, 2003, the
City Council held a public hearing on proposed changes to the City's on-site stonnwater
drainage code and received public input and comment on said proposed revisions;and
NOW,THEREFORE,THE CITY COUNCIL OF THE CITY OF MARYSVILLE,
WASHINGTON DO ORDAIN AS FOLLOWS:
Section 1.The existing On-Site Stonnwater Drainage Code,Chapter 14.15 is HEREBY
REPEALED.
Section 2. A new chapter MMC 14.15 On-Site Stonnwater Drainage Code is HEREBY
ENACTED reading as follows:
Chapter 14.15
ON-SITE STORMWATER
DRAINAGE CODE
Sections:
14.15.010 Purpose.
14.15.015 Stonnwater management manual adopted.
14.15.020 Definitions.
14.15.030 Applicability.
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14.15.040 Minimum requirement thresholds
14.15.050 Minimum requirements
14.15.060 Mandatory requirements for all drainage improvements.
14.15.065 Contents ofa stormwater site plan.
14.15.070 Development in critical flood, drainage and/or erosion areas.
14.15.080 Establishment of regional facilities.
14.15.090 Fees.
14.15.100 Construction standards and specifications.
14.15.110 Review and approval of plans.
14.15.120 Inspections - Construction.
14.15.130 Bonds and liability insurance required.
14.15.140 City assumption of maintenance.
14.15.150 Retroactivity relating to city maintenance of drainage facilities.
14.15.160 Maintenance of drainage facilities by owner.
14.15.165 Maintenance of drainage swales and ditches.
14.15.170 Applicability to governmental entities.
14.15.175 Adjustments.
14.15.180 Exceptions
14.15.185 Additional procedures and review.
14.15.190 Enforcement.
14.15.200 No special duty created.
14.15.210 Severability.
14.15.220 Appeals.
14.15.010 Purpose.
The city council finds that this chapter is necessary to promote sound development policies and
construction procedures which respect the city's watercourses; to minimize water quality
degradation and control of sedimentation of creeks, streams, ponds, lakes, and other water
bodies; to protect the life, health, and property of the general public; to preserve and enhance the
suitability of waters for contact recreation and fish habitat; to preserve and enhance the aesthetic
quality of the waters; to maintain and protect valuable ground water quantities, locations, and
flow patterns; to ensure the safety of city roads and rights-of-way; and to decrease drainage-
related damages to public and private property. (Ord. 2245 §2, 1999).
14.15.015 Stormwater management manual adopted.
The 2001 State Department of Ecology's Stormwater Management Manual for Western
Washington, is hereby adopted as a technical reference manual and is hereinafter referred to as
the Manual.
14.15.020 Definitions.For the purpose of this Chapter certain terms, phrases, words and their
derivatives shaIl be construed as specified in this Section. Words used in the singular include the
plural and the plural the singular. The words "shall", "will" and "must" are mandatory; the words
"should" and "may" are permissive. When any definition in this chapter conflicts with
definitions in the Manual or any other ordinance of the city, that which provides more
environmental protection shaIl apply unless specificaIlyprovided otherwise in this chapter.
(I)"Adjustment" means a project proposal that has received approval as providing substantiaIly
equivalent environmental protection while maintaining the objectives of safety, function, and
facility maintenance based upon sound engineering.
(2) "Applicant" means any person who has applied for a development permit or approval.
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(3)"Basin plan" means a plan that assesses, evaluates, and proposes solutions to existing and
potential future impacts to the beneficial uses of, and the physical, chemical, and biological
properties of waters of the state within a basin..' A plan should include but not be limited to
recommendations for:
• Stormwater requirements for new development and redevelopment;
• Capital improvement projects;
• Land use management through identification and protection of critical areas, comprehensive
land use and transportation plans, zoning regulations, site development standards, and
conservation areas;
• Source control activities includingpublic education and involvement, and business programs;
• Other targeted stormwater programs and activities, such as maintenance, inspections, and
enforcement;
• Monitoring; and
• An implementation schedule and funding strategy.
(4) "Biofiltration facility" means the simultaneous processes of filtration, absorption, and
biological uptake of pollutants in stormwater to take place when runoff flows over and through
vegetated treatment facilities.
(5) "Best management practices (BMPs)" refers to physical, structural, and/or managerial
practices, that when used singly or in combination, prevent or reduce pollution of water and have
been approved by the engineer. BMPs include, but are not limited to, infiltration, retention and/or
detention, biofiltration facilities, open ditches with check dams, filter fabric strips, oil/water
separators, wet ponds, constructed wetlands, erosion and sedimentation control, and other
treatment/abatement facilities.
(6) "City planner" alsomeans plaHHiHg community development director.
(7) "Clearing" means the destruction and removal of vegetation by manual, mechanical or
chemical methods.
(8)"Comprehensive drainage plan" means a detailed analysis adopted by the city which
compares the capabilities and needs for runoff accommodation due to various combinations of
development, land use, structural and nonstructural management alternatives. The plan
recommends the form, location, and extent of quantity and quality control measures which would
satisfy legal constraints, water quality standards and community standards and identifies the
institutional and funding requirements for plan implementation.
(9)"Computations"means calculations, including coefficients and other pertinent data made to
determine the drainage plan with flow of water given in cubic feet per second (cfs).
(10)"Construction stormwater pollution prevention plan" or "Construction SWPPP" means a
plan that includes a narrative, drawings, and details for describing construction practices,
stabilization techniques, and structural BMPs that are to be implemented to prevent erosion and
sedimentation, and control other pollutants at a construction site.
(11) "Conveyance system" means the drainage facilities, both natural and man-made, which
collect, contain, and provide for the flow of surface and stormwater from the highest points on
the land down to a receiving water. The natural elements of the conveyance system include
swales and small drainage courses, streams, rivers, lakes, and wetlands. The human-made
elements of the conveyance system include gutters, ditches, pipes, channels, and most
retention/detention facilities.
(12)"Current conditions" means the state, status, or conditions (land use, impervious surfaces,
topography, soils, and surface water flows) present of the subject property at the time the
analysis is conducted.
I Basins typically range from I to 50 square miles.
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(13) "Cut and fill" means the process of earth moving by excavating part of an area and using the
excavated material for adjacent embankments or fill areas.
(14)("Department" means the public works or community development department of the city
of Marysville, as appropriate for capital or private development projects.
(15) "Design storm" means a rainfall (or other precipitation) event or pattern of events for use in
analyzing and designing drainage facilities, specifying both the return period in years and the
duration in hours.
(16) "Detention" means the release of stormwater runoff from the site at a slower rate than it is
collected by the stormwater drainage system, the difference being held in temporary storage.
(17) "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.
-(18) "Developed conditions" means the state, status, or condition of the subject property at the
time the proposed project has been completed, which may include existing buildings, impervious
areas, and topography as is.
(19) "Developer" means the individual(s) or corporation(s) or governmental agency(ies)
applying
for the permits or approvals described in MMC 14.15.030.
(20) "Development" means any artificial change to property, including but not limited to
building or other structures, mining, dredging, filling, all land-disturbing activities, clearing,
grading, landscaping, paving, excavation, or drilling operations, any activity that requires a
permit or approval, including but not limited to a building permit, grading permit, shoreline
substantial development permit, conditional use permit, unclassified use permit, zoning variance
or reclassification, plarmed unit development, subdivision, short subdivision, master plan
development, building site plan, or right-of-way use permit.
(21) "Developmental coverage" means all developed areas within the subject property including
but not limited to rooftops, driveways,carports, accessory buildings, parking areas, and any other
impervious surfaces. During construction, "development coverage" includes the above in
addition to the full extent of any alteration of previously occurring soils, slope, or vegetation due
to grading, temporary storage, access areas, or other short term causes.
(22) "Director of Public Works" or "Director" means the Director of the Public Works
Department or hislher designee.
(23) "Drainage area" means the watershed (acreage) contributing surface water runoff to and
including the subject property.
(24) "Drainage site" means a geographical area that serves a common or combined use including
but not limited to shopping malls and strips, condominiums, apartment complexes, office parks,
and housing tracts. A site may include one or more parcels and/or include one or more buildings.
See also "development."
(25) "Drainage system" means the system of collecting, conveying, and storing surface and
stormwater runoff. Drainage facilities shall include but not be limited to all surface and
stormwater runoff conveyance and containment facilities including streams, pipelines, channels,
ditches, swamps, lakes, wetlands, closed depressions, infiltration facilities, retention/detention
facilities, erosion/sedimentation control facilities, and other drainage structures and
appurtenances, both natural and manmade.
(26) "Drainage treatment/abatement facilities" means any facilities installed or constructed in
conjunction with a drainage plan for the purpose of treating urban runoff to improve water
quality, excluding retention or detention facilities.
(27) "Effective impervious area" means those impervious surfaces that are connected via sheet
flow or discrete conveyanceto a drainage system.
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(28)"Engineer"means the city engineer or development services manager, as designated for
enforcement of capital or private development activities,ar llllblie '.'larks direetar of Marysville.
(29)"Environmentally sensitive areas" means areas defined as such by the Marysville sensitive
areas ordinance.
(30)"Erosion" means the wearing away of the land surface by running water, wind, ice or other
geological agents, including such processes as gravitational creep; and the detachment and
movement of soil or rock fragments by water, wind, ice or gravity.
(31) "Erosion and sediment control" means any temporary or permanent measures taken to
reduce erosion, control siltation and sedimentation,and ensure that sediment-laden water does
not leave the site.
(32)"Excavation"means the mechanical removal of earth material.
(33)"Exception"means relief from specific mandates of a Minimum Requirement.
(34)"Fill,"means a deposit of earth material placed by artificial means.
(35)"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:
• Road and trail construction;
• Harvesting, final and intermediate;
• Pre-commercial thinning;
• Reforestation;
• Fertilization;
• Prevention and suppression of diseases and insects;
• Salvage of trees; and
• Brush control.
(36)"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.
(37)"Existing grade" means the grade prior to grading.
(38) "Rough grade" means the stage at which the grade approximately conforms to the approved
plan.
(39)"Finish grade" means the final grade of the site, which conforms to the approved plan.
(40)"Grading"or "grading activity" means any excavating, filling, or grading or combination
thereof.
(41) "Ground water" means water in a saturated zone or stratum beneath the surface ofland or a
surface water body.
(42)"Illicit discharge" means all non-stormwater 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 gray water systems.
(43)"Impervious areas" means that hard surface area which either prevents or retards the entry
of water into the soil mantle and/or causes water to run off the surface in greater quantities or at
an increased rate of flow from that present under natural conditions prior to development.
Common impervious surfaces include, but are not limited to,roof tops, walkways, patios,
driveways, parking lots or storage areas, concrete or asphalt paving, gravel roads, packed earthen
materials, and oil, macadam, or other surfaces which similarly impede the natural infiltration of
surface and stormwater runoff. Open, uncovered retention/detention facilities shall not be
considered as impervious surfaces for the purposes of this document.
(44)"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 roadside ditch, wetland, spring or seep.
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(45) "Land clearing" or "Clearing" means the destruction or removal of vegetation from a site
by physical, mechanical, chemical or other means. This does not mean mowing, landscape
maintenance or pruning consistent with accepted horticultural and arboricultural practices, which
does not impair the health or survival of the trees and associated vegetation.
(46) "Land-disturbing activities" means any activity that disturbs or alters land surface including
clearing and grading.
-(47) "Lowest floor" means the lowest enclosed area (including basement)of a structure. An
area used solely for parking of vehicles, building access, or storage is not considered a building's
lowest floor; provided, that the enclosed area meets all ofthe structural requirements of the flood
hazard standards.
(48) "Manual" refers to the Washington Department of Ecology's "Stormwater Management
Manual for Western Washington, as amended."
(49)"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.
(50) "Natural location"of drainage systems refers to the location of those channels, swales, and
other natural 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.
(51) "New development" means the following activities: land-disturbing activities; structural
development, including construction, installation, or expansion of building or other structures;
installation of impervious surfaces, and subdivisions or short plats.
(52) "On-site stormwater management BMPs" means site development techniques that serve to
infiltrate, disperse, and retain stormwater runoff on-site.
(53) "Parcel" means a tract or plot of land of any size, which mayor may not be subdivided or
improved.
(54) "Permanent erosion and sediment control" means the continuous on-site and off-site control
measures that are needed to prevent accelerated erosion, sedimentation or related pollution from
occurring after completion of the grading activityor the construction project.
(55) "Permanent stormwater control (PSC) plan" means a plan which includes permanent BMPs
for the control of pollution from stormwater runoff after construction and/or land disturbing
activityhas been completed.
(56) "Person" means any individual, partnership, corporation, association, organization,
cooperative, public or municipal corporation, agency of the state, or local government unit,
however designated.
(57) "Planned residential developments" refers to residential developments which are planned
and/or developed in several stages but submitted together for approvals, and which typically
consist of clusters of structures interspersed with areas of common open spaces (refer to Chapter
19.48MMC).
(58)"Pollutant"shall mean any substance which, when added to water, would contaminate or
alter the chemical, physical, or biological properties of any waters of the city's drainage system
or of the state. This includes a change in temperature, taste, color, turbidity, or odor of the
waters, or such discharge of any liquid, gaseous, solid, radioactive, or other substance into any
waters of the city's drainage system or of the state as will or is likely to create a nuisance.It also
includes any substance which renders such waters harmful, detrimental, or injurious to the public
health, safety, or welfare, or to domestic, commercial, industrial, agricultural, recreational, or
other legitimate beneficial use, or to livestock, wild animals, birds, fish, or other aquatic life.
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(59) "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 and 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, recreation or other legitimate beneficial uses, or to livestock, wild
animals, birds, fish, or other aquatic life.
(60) "Pollution-generating impervious surface (PGIS)" means those impervious surfaces
considered to be a significant source of pollutants in stormwater runoff. Such surfaces include
those which are subject to: vehicular use; industrial activities; 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. Metals roofs are also
considered to be PGIS unless they are coated with an inert, non-leachable 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.
(61) "Pollution-generating pervious surface (PGPS)" means any non-impervious surface subject
to use of pesticides, fertilizers, or loss of soil.
(62) "Private drainage system" means drainage systems located on private property and designed
to discharge directly as through pipes, channels, etc., or indirectly as sheet flow, subsurface flow,
etc. into the city's drainage system.
(63) "Project site" means that portion of a property, properties, or right of way subject to land
disturbing activities, new impervious surfaces, or replaced impervious surfaces.
(64) "Public drainage system" means that portion of the drainage system of the city located on
public right-of-way, easements or other property owned by the city, and those portions of private
drainage systemsoperated and maintained by the city.
(65) "Receiving waters" means bodies of water or surface water systems receiving water from
upstream manmade (or natural) systems. For the purpose of this chapter receiving waters are
Ebey Slough and the Snohomish River.
(66) "Redevelopment" means, on an already developed site, the creation and/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.
(67) "Regional" means an action that involves more than one discrete parcel.
(68) "Regional detention facility"means a stormwater quantity control structure designed to
correct existing surface water runoff problems for all or a portion of a basin or sub-basin. 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.
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(69)"Replaced impervious surface"means the removal and replacement of any exterior
impervious surfaces or foundation of a structure. Other impervious surfaces are considered
replaced if first removed down to bare soil or base course.
(70)"Retention/detention facility (RID)" means a type of drainage system 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
short period of time and then release it to the surface and stormwater management system.
(71)"Sediment"means solid particulate matter, both mineral and organic, that has been or is
being transported by water, air, gravity, or ice from its original site of origin.
(72)"Sedimentation"means the process by which sediment has been transported off the site of
the grading activity and settled onto land or the bed of a creek, stream, river, wetland, pond, or
other water body.
(73)"Site"means the area defined by the legal boundaries of a parcel or parcels of land subject
to new development or redevelopment.For road projects, the length of the project site and the
right-of-way boundaries define the site.
(74) "Site plan"means a plan which indicates the character of the existing site,topography,
natural drainage features on or adjacent to the site, the location and dimensions of all impervious
surfaces, flow arrows indicating the direction of stormwater flows on-site, and any off-site flows
entering the site, the proposed method of utilizing the existing drainage system.
(75)"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: I.
-(76)"Soil"means the unconsolidated mineral and organic material on the immediate surface of
the earth that serves as a natural medium for the growth ofland plants.
(77)"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. 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.
(78) "Storm drainage plan" means a plan approved by the city of Marysville which includes
either a small parcel or large parcel erosion and sediment control plan and/or a water quality
control plan.
(79)"Stormwater"means that portion of precipitation that does not naturally percolate into the
ground or evaporate, but flows via overland flow, interflow, pipes, or other features of a
stormwater drainage system into a defined surface waterbody or a constructed infiltration
facility.
(80)"Stormwater Management Manual for Western Washington"means the manual prepared by
the Department of Ecology that contains BMPs to prevent or reduce pollution.
(81) "Stormwater site plan" means the comprehensive report containing all of the technical
information and analysis necessary to evaluate a proposed new development or redevelopment
project for compliance with stormwater requirements. Contents of the Stormwater Site Plan will
vary with the type and size of the project, and individual site characteristics.It includes a
Construction Stormwater Pollution Prevention Plan (Construction SWPPP) and a Permanent
Stormwater Control Plan (PSC Plan).
(82)"Subject property"means the tract of land which is the subject of the permit and/or approval
action.
(83)"Surface water" means the naturally occurring water that flows over or is stored on the
earth's surface.
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-{84)"Temporary erosion control"means the on-site and off-site control measures that are
needed during construction activities to prevent accelerated erosion,sedimentation or related
pollution from occurring,but may not be needed when the project is completed or when ground
conditions have been stabilized by permanent erosion control measures.
(85)"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).
(86) "Total Maximum Daily Load (TMDL)"means a calculation of the maximum amount of a
pollutant that a waterbody can receive and still meet water quality standards, and an allocation of
that amount to the pollutant's sources.
(87)"Undeveloped conditions"means the state, status, or condition of the subject property prior
to any development of the property that has occurred, which may include trees,pastures,
meadows, or native features.
(88)"Uncontaminated"means water that has not come into contact with illicit discharges.
(89)"Waterbody"means surface waters including rivers, streams, lakes,marine waters,estuaries
and wetlands.
(90)"Water quality control plan (WQCP)"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. (Ord. 2245 §2, 1999).
(91)"Water quality design flow rate" means:
•Preceding detention facilities or when detention facilities are not required: that rate at or
below which 91 percent of the runoff volume, as estimated by an approved continuous runoff
model, will be treated.
•Downstream of detention facilities: the full 2-year release rate from the detention facility
(92)"Water quality design storm" means the 24-hour rainfall amount with a 6-month return
frequency.It is commonly referred to as the 6-month,24-hour design storm.
(93)"Water quality design storm volume"means the volume of runoff predicted from a 24-hour
storm with a 6-month return frequency.
(94)"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 (WRlA's)as defined in Chapter 173-500 WAC or succeeding regulation.
(95) Wetland or wetlands. Areas that are inundated or saturated by surface water 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 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 However, wetlands include those
artificial wetlands intentionally created to mitigate conversion of wetlands. See the Federal
Manual for Identifying and Delineating Jurisdictional Wetlands (January, 1987) for more
information.
14.15.030 Applicability.
(I)All persons taking any of the following actions or applying for any of the following permits
and/or approvals shall,unless otherwise excepted or exempted by other provisions of this
chapter, be required to submit for approval a site plan with their application and/or request: (a)
Creation or alteration of new or additional impervious surfaces; (b) New development;(c)
Redevelopment;(d)Building permit; (e)Subdivision approval;(f)Short subdivision approval;
(g)Commercial,industrial,or multifamily site plan approval; (h) Planned unit development;(i)
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Development within or adjacent to sensitive areas per MMC 19.24 *;(j)Conditional use
permits;(k)Substantial development permit required under Chapter 90.58 RCW (Shoreline
Management Act);(I)Logging,clearing,and other land-disturbing activities.Exception:
Activities not requiring machinery for construction or excavation and that are not subject to other
environmental regulation are considered exempt from the provisions of this chapter.In addition
to a site plan other plan requirements are set out in the text of this chapter and are summarized
for various types of activities in Table 14.15-1.
(2)Commencement of construction work under any of the nonexempt actions,permits,or
applications set forth in subsection (I)of this section shall not begin until the Department
approves a stonnwater pollution prevention plan pursuant to MMC 14.15.050(2).Exception:A
site plan only, and no stonnwater pollution prevention,shall be required for activities on single-
family lots in subdivisions where the final plat for the subdivision occurred after May 1,1999.
(3)Guidance on preparing a stonnwater pollution prevention plan is contained in the manual.
(4)Whenever a minimum area or quantity requirement is set forth in this chapter,such
requirement shall be met if any activity or development occurs on the subject property within a
continuous 18-month period.
14.15.040 Minimum Requirement Thresholds
1. New Development.The Minimum Requirements discussed in this Section are described in
Section 14.1 5.050.All new development shall be required to comply with Minimum
Requirement No.2.In addition,new development that exceeds certain thresholds shall be
required to comply with additional Minimum Requirements described in Section 14.15.050.
as follows:
A.The following new development shall comply with Minimum Requirement Nos.1
through 5.
I.)Development that includes the creation or addition of 2,000 square feet or greater,of
new,replaced,or new plus replaced impervious surface area; or
2.)Development that includes land disturbing activity of 7,000 square feet or greater.
B.The following new development shall comply with Minimum Requirements #1 through
#10.
I.)Creates or adds 5,000 square feet or greater,of new impervious surface area; or
2.)Converts %acres or more of native vegetation to lawn or landscaped areas; or
3.)Converts 2.5 acres or more of native vegetation to pasture.
2.Redevelopment.All redevelopment shall be required to comply with Minimum Requirement
NO.2.In addition,redevelopment that exceeds certain thresholds shall be required to comply
with additional Minimum Requirements described in Section 14.15.050.as follows:
A. The following redevelopment shall comply with Minimum Requirement Nos. 1 through
5 for the new and replaced impervious surfaces and the land disturbed:
1.)The new,replaced,or total of new plus replaced impervious surfaces is 2,000 square
feet or more;or
2.)Redevelopment that includes land disturbing activity of 7,000 square feet or more.
B.The following redevelopment shall comply with Minimum Requirement Nos. 1 through
10 for the new impervious surfaces and converted pervious surfaces:
1.)Redevelopment that adds 5,000 square feet or more of new impervious surfaces;or
2.)Redevelopment that converts %acres or more of native vegetation to lawn or
landscaped areas; or
3.)Redevelopment that converts 2.5 acres or more of native vegetation to pasture.
C.Commingled Stonnwater.If the runoff from the new impervious surfaces and converted
pervious surfaces is not separated from runoff from other surfaces on the project site, the
stonnwater treatment facilities must be sized for the entire flow that is directed to them.
10
D. Equivalent Area. The Director may allow the Minimum Requirements to be met for an
equivalent (flow and pollution characteristics) area within the same site. For public road
projects, the equivalent area does not have to be within the project limits, but must drain
to the same receiving water.
E. 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.
Assessed Value Threshold2. Other types of development not regulated by Section
14.15.040.2.E. above, shall comply with all the Minimum Requirements for the new and
replaced impervious surfaces if the total of the 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.
F. Regional Facilities. The Director may exempt or institute a stop-loss provision for
redevelopment projects from compliance with Minimum Requirements for treatment,
flow control, and wetlands protection as applied to the replaced impervious surfaces if
the City has adopted a plan and schedule that fulfills those requirements in regional
facilities.
14.15.050 Minimum Requirements
This Section identifies the ten Minimum Requirements for stormwater management applicable to
new development and redevelopment sites. See the Manual for additional details related to each
of the Minimum Requirements. The Minimum Requirements are:
• Preparation of Stormwater Site Plans
• Construction Stormwater Pollution Prevention
• Source Control of Pollution
• Preservation of Natural Drainage Systems and Outfalls
• On-site Stormwater Management
•Runoff Treatment
• Flow Control
• Wetlands Protection
• Basin/Watershed Planning
• Operation and Maintenance
1.Minimum Requirement #1: Preparation of Stormwater Site Plans. All projects meeting the
thresholds in Section 14.15.040. shall prepare a Stormwater Site Plan.
2. Minimum Requirement #2: Construction Stormwater Pollution Prevention (SWPP). All new
development and redevelopment shall comply with Construction SWPP Elements #1 through
#12 below.
A. Projects in which the new, replaced, or new plus replaced impervious surfaces total
2,000 square feet or more or disturb 7,000 square feet or more of land must prepare a
Construction SWPP Plan (SWPPP) as part of the Stormwater Site Plan. Each of the
2 See the Supplemental Guidelines in Volume I, page 2-13 of the Stonnwater Management Manual for Western
Washington for other monetary criteria options.
11
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twelve elements must be considered and included in the Construction SWPPP unless the
Director decides that site conditions render the element unnecessary and the exemption
from that element is clearly justified in the narrative of the SWPPP.
B.Projects that add or replace less than 2,000 square feet of impervious surface or disturb
less than 7,000 square feet ofland are not required to prepare a Construction SWPPP, but
must consider all of the twelve Elements of Construction Stormwater Pollution
Prevention and develop controls for all elements that pertain to the project site.
C.Element I: Mark Clearing Limits.
1.)Prior to beginning land disturbing activities,including clearing and grading, all
clearing limits,sensitive areas and their buffers, and trees that are to be preserved
within the construction area should be clearly marked, both in the field and on the
plans, to prevent damage and offsite impacts.
2.) Plastic, metal, or stake wire fence may be used to mark the clearing limits.
D.Element 2: Establish Construction Access.
1.)Access Limited.Construction vehicle access and exit shall be limited to one route if
possible.
2.)Tracking Sediment. Access points shall be stabilized with quarry spall or crushed
rock to minimize the tracking of sediment onto public roads.
3.) Wheel Wash. Wheel wash or tire baths should be located on-site, if applicable.
4.) Clean Public Roads.Public roads shall be cleaned thoroughly at the end of each day.
Sediment shall be removed from roads by shoveling or pickup sweeping and shall
be transported to a controlled sediment disposal area. Street washing will be
allowed only after sediment is removed in this manner.
5.) Street Wash Water. Street wash wastewater shall be controlled by pumping back on-
site, or otherwise be prevented from discharging into systems tributary to state
surface waters.
E.Element 3: Control Flow Rates.
I.) General.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.
2.)Downstream Analysis.Downstream analysis is necessary if changes in flows could
impair or alter conveyance systems, stream banks, bed sediment or aquatic habitat.
3.)BMPs Functional.Stormwater retention/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).
4.)Additional Flow Standards. The Director may require pond designs that provide
additional or different stormwater flow control if necessary to address local
conditions or to protect properties and waterways downstream from erosion due to
increases in the volume, velocity, and peak flow rate of stormwater runoff from the
project site.
5.)Permanent Infiltration Ponds.If permanent infiltration ponds are used for flow
control during construction,these facilities should be protected from siltation during
the construction phase.
F.Element 4: Install Sediment Controls.
1.)Natural Vegetation. The duff layer, native top soil, and natural vegetation shall be
retained in an undisturbed state to the maximum extent practicable.
2.)Sediment Removal BMP.Prior to leaving a construction site, or prior to discharge to
an infiltration facility,stormwater runoff from disturbed areas shall pass through a
sediment pond or other appropriate sediment removal BMP.Runoff from fully
stabilized areas may be discharged without a sediment removal BMP, but must
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meet the flow control performance standard of Element #3. Full stabilization means
concrete or asphalt paving; quarry spalls used as ditch lining; or the use of rolled
erosion products, a bonded fiber matrix product, or vegetative cover in a manner
that will fully prevent soil erosion. The Director shall inspect and approve areas
stabilized by means other than pavement or quarry spalls.
3.) BMPs Functional. Sediment ponds, vegetated buffer strips,sediment barriers or
filters, dikes, and other BMPs intended to trap sediment on-site shall be constructed
as one of the first steps in grading, These BMPs shall be functional before other
land disturbing activities take place.
4.) Seeding. Earthen structures such as dams, dikes, and diversions shall be seeded and
mulched according to the timing indicated in Element #5.
G. Element 5: Stabilize Soils.
I.) General. All exposed and unworked soils shall be stabilized by application of
effective BMPs that protect the soil from the erosive forces of raindrop impact and
flowing water, and wind erosion.
2.)Applicable Practices. Applicable practices include, but are not limited to, temporary
and pennanent seeding, sodding, mulching, plastic covering, soil application of
polyacrylamide (PAM), early application of gravel base on areas to be paved, and
dust control.
3.) Soil Stabilization. Soil stabilization measures selected should be appropriate for the
time of year, site conditions, estimated duration of use, and potential water quality
impacts that stabilization agents may have on downstream waters or ground water.
4,) Soil Stockpiles. Soil stockpiles must be stabilized and protected with sediment
trapping measures.
5,) Linear Facilities. Work on linear construction sites and activities,including right-of-
way and easement clearing, roadway development,pipelines,and trenching for
utilities, shall not exceed the capability of the individual contractor for his portion
of the project to install the bedding materials, roadbeds, structures, pipelines, and/or
utilities, and to re-stabilize the disturbed soils,meeting the timing conditions listed
above in Section l4.l5.050.2.G.2.).
H. Element 6: Protect Slopes.
1.)Cut and Fill Slopes. Cut and fill slopes shall be designed and constructed in a
manner that will minimize erosion.
2.) Soil Types.Consider soil type and its potential for erosion.
3.)Runoff Velocities. Reduce slope runoff velocities by reducing the continuous length
of slope with terracing and diversions, reduce slope steepness, and roughen slope
surface.
4.) Diverted Flows. Divert upslope drainage and run-on waters from off-site with
interceptors at top of slope. Off-site stonnwater should be handled separately from
stonnwater generated on the site.Diversion of off-site stonnwater around the site
may be a viable option. Diverted flows shall be redirected to the natural drainage
location at or before the property boundary.
5.) Collected Flows. Contain downslope collected flows in pipes, slope drains, or
protected channels.
6.) Ground Water. Provide drainage to remove ground water intersecting the slope
surface of exposed soil areas.
7.) Excavation. Excavated material shall be placed on the uphill side of trenches,
consistent with safety and space considerations.
8.) Check Dams. Check dams shall be placed at regular intervals within trenches that
are cut down a slope,
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9,)Stabilize Soils.Stabilize soils on slopes, as specified in Element #5.
I.Element 7:Protect Drain Inlets.
I.) General. 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 treated to remove sediment.
2.) Roads. All approach roads shall be kept clean, and all sediment and street wash
water shall not be allowed to enter storm drains without prior and adequate
treatment unless treatment is provided before the storm drain discharges to waters
of the State.
J.Element 8:Stabilize Channels and Outlets.
1.) General. All temporary on-site conveyance channels shall be designed,constructed
and stabilized to prevent erosion from the expected velocity of flow from a 2 year,
24-hour frequency storm for the developed condition.
2.)Stabilization.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.
K.Element 9: Control Pollutants.
1.)General. All pollutants,including waste materials and demolition debris, that occur
on-site during construction shall be handled and disposed of in a manner that does
not cause contamination of stormwater.
2.)Vandalism.Cover,containment,and protection from vandalism shall be provided
for all chemicals,liquid products,petroleum products,and non-inert wastes present
on the site.
3.)Equipment Maintenance.Maintenance and repair of heavy equipment and vehicles
involving oil changes,hydraulic system drain down,solvent and de-greasing
cleaning operations,fuel tank drain down and removal,and other activities which
may result in discharge or spil1age of pollutants to the ground or into stormwater
runoff must be conducted using spil1 prevention measures,such as drip pans.
Contaminated surfaces shall be cleaned immediately following any discharge or
spill incident.Emergency repairs may be performed on-site using temporary plastic
placed beneath and,if raining, over the vehicle.
4.) Wheel Wash.Wheel wash, or tire bath wastewater,shall be discharged to a separate
on-site treatment system.1t may be discharged to the sanitary sewer system only if
expressly allowed by the local sewer district authority.
5.)Agricultural Chemicals.Application of agricultural chemicals,including 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'recommendations
shall be followed for application rates and procedures.
6.) pH Management.Management of pH-modifying sources shall prevent
contamination of runoff and stormwater collected on the site.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,and concrete pumping and mixer washout
waters.
1.Element 10: Control De-Watering.
1.) General. All foundation,vault, and trench de-watering water, which have 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.
Channels must be stabilized,as specified in Element #8.
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2.) Clean Water. Clean, non-turbid de-watering water, such as well-point ground water,
can be discharged to systems tributary to state surface waters, as specified in
Element #8, provided the de-watering flow does not cause erosion or flooding of
the receiving waters. These clean waters should not be routed through sediment
ponds with stormwater.
3.) Contaminated Water. Highly turbid or otherwise contaminated dewatering water,
such as from construction equipment operation, clamshell digging, concrete tremie
pour, or work inside a cofferdam, shall be handled separately from stormwater at
the site.
4.) Other Disposal Options. Depending on site constraints, dewatering may include:
infiltration; transport off-site in vehicle, such as a vacuum flush truck, for legal
disposal in a manner that does not pollute state waters; on-site treatment using
chemical treatment or other suitable treatment technologies; or sanitary sewer
discharge with [local sewer district approval] approval if there is no other option.
M. Element II:Maintain BMPs.
1.) General. 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 BMPs.
2.) Inspection. Sediment control BMPs shall be inspected weekly or after a runoff-
producing storm event during the dry season and daily during the wet season.
3.) Remove BMPs. 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. Trapped sediment shall be removed or stabilized on-site.
Disturbed soil areas resulting from removal of BMPs or vegetation shall be
permanently stabilized.
N. Element 12: Manage The Project.
1.) Phasing of Construction. Development projects shall be phased where feasible in
order to prevent, to the maximum extent practicable, the transport of sediment from
the project site during construction. Revegetation of exposed areas and
maintenance of that vegetation shall be an integral part of the activities for any
phase. Clearing and grading activities for developments shall be permitted only if
conducted pursuant to an approved site development plan (e.g., subdivision
approval) that establishes permitted areas of clearing, grading, cutting, and filling.
When establishing these permitted clearing and grading areas, consideration should
be given to minimizing removal of existing trees and minimizing
disturbance/compaction of native soils except as needed for building purposes.
These permitted clearing and grading areas and any other areas required to preserve
critical or sensitive areas, buffers, native growth protection easements, or tree
retention areas as may be required by the Director, shall be delineated on the site
plans and the development site.
2.) Coordination with Other Contractors. The primary project applicant shall evaluate,
with input from utilities and other contractors, the stormwater management
requirements for the entire project, including the utilities, when preparing the
Construction SWPPP.
3.) Inspection. All BMPs shall be inspected, maintained, and repaired as needed to
assure continued performance of their intended function.
a.) Certified Professional. A Certified Professional in Erosion and Sediment
Control shall be identified in the Construction SWPPP and shall be on-site or
on-call at all times.Certification may be through the Washington State
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Department of Transportation!Associated General Contractors (WSDOTIAGe)
Construction Site Erosion and Sediment Control Certification Program or any
equivalent local or national certification and/or training program.
b.)Sampling.Sampling and analysis of the stormwater discharges from a
construction site may be necessary on a case-by-case basis to ensure
compliance with standards.Monitoring and reporting requirements may be
established by the Director when necessary.
c.)Modify SWPPP.Whenever inspection and/or monitoring reveals that the
BMPs identified in the Construction SWPPP are inadequate,due to the actual
discharge of or potential to discharge a significant amount of any pollutant,the
SWPPP shall be modified,as appropriate,in a timely manner.
4.)Construction SWPPP.The Construction SWPPP shall be retained on-site or within
reasonable access to the site. The Construction SWPPP shall be modified whenever
there is a significant change in the design,construction,operation,or maintenance
ofanyBMP.
3.Minimum Requirement #3:Source Control Of Pollution.All known,available and
reasonable source control BMPs shall be applied to all projects.Source control BMPs shall
be selected,designed,and maintained according to the Manual.
4.Minimum Requirement #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 downgradient properties.All outfalls require energy dissipation
5.Minimum Requirement #5:On-site Stormwater Management.Projects shall employ on-site
Stormwater Management BMPs to infiltrate,disperse,and retain storm water runoff on-site to
the maximum extent feasible without causing flooding or erosion impacts.On-site
Stormwater Management BMPs as identified in the Manual shall be used for roof downspout
control, flow dispersion,and soil quality.
6.Minimum Requirement #6:Runoff Treatment.
A.Thresholds.The following require construction of stormwater treatment facilities (see
Table 14.15.050.6.A):
I.)Projects in which the total of effective,pollution-generating impervious surface
(POlS)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 surfaces (PGPS)is three-
quarters (3/4)of an acre or more in a threshold discharge area, and from which there
is a surface discharge in a natural or man-made conveyance system from the site.
3)That portion of any development project in which the above POlS or PGPS
thresholds are not exceeded in a threshold discharge area shall apply On-site
Stormwater Management BMPs in accordance with Minimum Requirement #5.
Table 14.15.050.6.A):
Treatment Requirements by Threshold Discharge Area
<%acres of >%acres <5,000 sf >5,000 sf
PGPS PGPS POlS PGIS
Treatment Facilities .;.;
Onsite Stormwater .;.;.;.;
BMPs
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POPS =pollution-generating pervious surfaces
POlS =pollution-generating impervious surfaces
sf =square feet
B. Treatment Facility Sizing. Treatment facilities shall be sized to provide effective
treatment of91 percent of the annual average runoff volume.
I.)The Water Quality Design Volume shall be used to size volume-based treatment
facilities. The volume of runoff shall be estimated using methods approved in the
Manual.
2.) The Water Quality Design Flow Rate shall be used to size flow rate-based treatment
facilities.
3.) The Director may allow alternative methods if they identify volumes and flow rates
that are at least equivalent.
C. Treatment Facility Selection, Design, and Maintenance.Stormwater treatment facilities
shall be:
1.)Selected in accordance with the process identified in the Manual;
2.)Designed in accordance with the design criteria in the Manual; and
3.)Maintained in accordance with the maintenance schedule in the Manual.
D. Untreated Stormwater. Direct discharge of untreated stormwater from pollution-
generating impervious surfaces to ground water is prohibited, except for the discharge
achieved by infiltration or dispersion of runoff from residential sites through use of On-site
Stormwater Management BMPs.
7. Minimum Requirement #7: Flow Control.
A. Applicability
1.)Flow Control. Projects must provide flow control to reduce the impacts of
stormwater runoff from impervious3 surfaces and land cover conversions. The
requirement below applies to projects that discharge stormwater directly, or indirectly
through a conveyance system, into a fresh water, except for discharges into a wetland.
(See Minimum Requirement #8 for flow control requirements applicable to
discharges to wetlands.)
2.) Exempt Areas. The Director may petition the Department of Ecology to exempt
projects in certain areas provided those areas also meet the following criteria:
a.) The area 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 ordinaryhigh water line of the receiving water; and
b.) Any erodible elements of the manmade conveyance system for the area must be
adequately stabilized to prevent erosion; and
c.) Surface water from the area must not be diverted from or increased to an
existing wetland, stream, or near-shore habitat sufficient to cause a significant
adverse impact.
B. Thresholds. The following require construction of flow control facilities and/or land use
management BMPs that will achieve the standard requirement for western Washington
(See Section 14.15.050.7.C):
Table 14.1S.0S0.7.B.
3 The Stonnwater Management Manual for Western Washington (Volume I, page 2-29) includes the words
"increased"and "new"prior to "impervious surfaces".Thisis an error that willbe corrected via addenda to the
manual.
17
,.
Flow Control Requirements bv Threshold Discharge Area
Flow On-site
Control Stormwater
Facilities Management
BMPs
<%acres conversion to lawn/landscape, or <2.5 acres '"to pasture
>%acres conversion to lawn/landscape,or>2.5 acres '"v
to pasture
<I0,000 square feet of effective impervious area '"> I0,000 square feet of effective impervious area '"'"> 0.1 cubic feet per second increase in the 1OO-year '"v
flood frequency
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 %acres or more of native vegetation to lawn or landscape, or
convert 2.5 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 man-made conveyance
system from the site, or
3.) Projects that through a combination of effective impervious 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 HydrologyModel or other model authorized by the Director.
4.) That portion of any development project in which the above thresholds are not
exceeded in a threshold discharge area shall apply Onsite Stormwater Management
BMPs in accordance with Minimum Requirement 5.
C. Standard Requirement.
1.)Peak Flows. Stormwater discharges shall match developed discharge durations to
pre-developed durations for the range of pre-developed discharge rates from SO
percent of the 2-year peak flow up to the full SO-year peak flow.
2.) Pre-developed Condition. The pre-developed condition to be matched shall be a
forested land cover unless reasonable, historic information is provided that indicates
the site was prairie prior to settlement (modeled as "pasture"in the Western
Washington Hydrology Model). This standard requirement is waived for sites that
will reliably infiltrate all the runoff from impervious surfaces and converted pervious
surfaces.
D. Flow Control Facility Selection, Design, and Maintenance. Flow Control facilities shall
be selected, designed, and maintained in accordance with the Manual.
E. The base of a permanent infiltration systems shall be a minimum of 3 feet above the
seasonal high ground water mark.
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8.Minimum Requirement #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 #6,
RunoffTreatment.
B. Thresholds. The thresholds identified in Minimum Requirement #6 -Runoff
Treatment, and Minimum Requirement #7 - Flow Control shall also be applied for
dischargesto wetlands.
C. Standard Requirement. Discharges to wetlands shall maintain the hydrologic
conditions, hydrophytic vegetation, and substrate characteristics necessary to support
existing and designated uses. A wetland can be considered for hydrologic
modification and/or stormwater treatment in accordance with guidance within the
Manual.
D. Additional Requirements. The standard requirement does not excuse any discharge
from the obligation to apply whatever technology is necessary to comply with state
water quality standards, Chapter 173-201A WAC, or state ground water standards,
Chapter 173-200 WAC or successor regulations. Stormwater treatment and flow
control facilities shall not be built within a natural vegetated buffer, except for:
necessary conveyance systems as approved by the Director; or as allowed in wetlands
approved for hydrologic modification and/or treatment in accordance with the Manual.
An adopted and implemented basin plan (Minimum Requirement #9), or a Total
Maximum Daily Load (TMDL) may be used to develop requirements for wetlands that
are tailored to a specific basin.
9. Minimum Requirement #9: BasinlWatershed Planning. Projects may be subject to
equivalent or more stringent minimum requirements for erosion control, source control,
treatment, and operation and maintenance, and alternative requirements for flow control and
wetlands hydrologic control as identified in BasinIWatershed Plans. Standards developed
from basin plans shall not modif'y any of the above minimum requirements until the basin
plan is formally adopted and implemented by the City within the basin, and approved or
concurred with by the Department of Ecology.
10. Minimum Requirement #10: Operation and Maintenance. An operation and maintenance
manual that is consistent with the Manual shall be provided for all proposed stormwater
facilities and BMPs, and the person responsible for maintenance and operation shall be
identified. At private facilities, a copy of the manual shall be retained on-site or within
reasonable access to the site, and shall be transferred with the property to the new owner.
For public facilities, a copy of the manual shall be retained by the Director or other
appropriate location. A log of maintenance activity that indicates what actions were taken
shall be kept andbe available for inspection by the Director.
14.15.060 Mandatory requirements for all drainage improvements.
(1) Commencement of construction, grading or site alteration work under any of the permits or
approvals listed in MMC 14.15.030 shall not begin until such time as final approval of the
Stormwater Site Plan has been grantedby the Director or designee.
(2) Surface water entering the subject property shall be received at the naturally occurring
location and surface water exiting the subject property shall be discharged at the natural location
with adequate energy dissipaters to minimize downstream damage and with no diversion at any
of these points.
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-.1'-;
(3) Where open ditch construction is used to handle drainage within the subject property, a
minimum of IS feet will be provided between any structures and the top of the bank of the
defined channel.
(a) In open channel work the water surface elevation will be indicated on the plan and profile
drawings. The configuration of the finished grades constituting the banks of the open channel
will also be shown on the drawings.
(b) Proposed cross-section of the channel will be shown with stable side slopes. Side slopes will
be three to one maximum unless stabilized in some manner approved by the department.
(c) The water surface elevation of the design flow will be indicated on the cross-section.
(4)Where a closed system is used to handle drainage within the subject property, all structures
will be a minimum of 10 feet from the closed system.
(5) The proposed measures for controlling runoff during construction including a statement
indicating the proposed staging of all clearing, grading and building activities.
(6) Drainage facilities shall be designed and constructed in accordance with city standards and as
directed by the engineer.
(7)Vegetation shall be established on areas disturbed or other locations on the site to protect
watercourses from erosion,siltation or temperature increases.
(8) Surface water exiting from the subject property shall have pollution control and oil separator
devices installed at the discharge point from the subject property when draining parking lots with
paved roadway surfaces or handling contaminated storm runoff. (Ord. 2245 § 2, 1999).
(9) Where open detention/retention ponds are used to handle drainage within the subject property
a 20 foot setback is required from all property lines. This setback may be reduced
administratively through the drainage plan review process if it can be demonstrated that the
reduction will not result in impacts on adjacent property, such as setbacks, or jeopardize the
integrity of the pond or adjacent buildings.
(10)Background Computations for Sizing Drainage Facilities.
(A)Depiction of the drainage area on a topographical map, with acreage indicated;
(B) Indications of the peak discharge and amount of surface water currently entering and leaving
the subject property;
(C) Indication of the peak discharge and amount of runoff which will be generated with the
subject property,if development is allowed to proceed;
(D)Computations shall be prepared using either the Western Washington Hydrology Model
(WWHM)or Waterworks software for hydrology as developed by Engenious Systems Inc. Flow
control and detention volumes will be computed using consistent software for the development.
Format shall be as directed by public works director or designee.
(11) Where the Manual cites 5 feet as the required groundwater separation for infiltration
facilities, 3 feet shall be used.
14.15.065 Contents of a Stormwater Site Plan
I. Site Plan Required. All projects for new development or redevelopment,which exceed the
thresholds of 2,000 square feet for impervious surfaces or 7,000 square feet for land
disturbance,must prepare a Stormwater Site Plan.
2.Contents of Plan.Contents of a Stormwater Site Plan will vary with the type and size of the
project and individual site characteristics.Two major elements included in a Stormwater Site
Plan are a Construction Stormwater Pollution Prevention Plan and a Permanent Stormwater
Control Plan. The following documents are to be included in a Stormwater Site Plan:
A. Project overview;
B.Existing conditions summary;
C. Off-site Analysis Report; (not necessary for manual equivalency)
D.Construction Stormwater Pollution Prevention Plan;
E.Permanent Stormwater Control Plan;
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F. Special Reports and Studies;
G. Other Permits;
H. Operation and Maintenance Manual; and
3. Detailed Information in Manual. Additional details on the content and the procedures for
preparation of a Stormwater Site Plan, a Construction Stormwater Pollution Prevention Plan,
and a Permanent Stormwater Quality Control Plan are included in the Manual.
14.15.070 Development in critical flood,drainage and/or erosion areas.
Development which would increase the volume of discharge from the subject property shall not
be permitted in areas where existing flooding, drainage, seismic hazard and/or erosion conditions
present an imminent likelihood of harm to the welfare and safety of the surrounding community
or property, until such time as the community hazard is alleviated. Where application of the
provisions of this section will deny all reasonable use of the property, the Director or designee
may waive the restrictions on development contained in this section; provided, that the resulting
development shall be subject to all of the remaining terms and conditions of this chapter. (Ord.
2245 § 2, 1999).
14.15.080 Establishment of regional facilities.
1.Public Benefit. In the event that public benefits would accrue due to modification of the
drainage plan for the subject property to better implement the recommendations of the
comprehensive drainage plan, the Director or designee may recommend that the city should
assume responsibility for the further design, construction, operation, and maintenance of the
drainage facilities, or any increment thereof, on the subject property. Such decision shall be
made concurrently with review and approval of the plan.
2.Applicant's Responsibility. In the event that the city decides to assume responsibility for all
or any portion of the design,construction,operation, and maintenance of the facilities, the
applicant shall be required to contribute a prorated share to the estimated cost of the facilities;
provided, that such share shall not exceed the estimated costs of improvements the applicant
would otherwise have been required to install. The applicant may be required to supply
additional information at the request of the Director or designee to aid in such determination by
the city. (Ord. 2245 § 2, 1999).
14.15.090 Fees.
Fees shall be charged for preliminary review,construction plan review, inspection, and final plan
review done upon completion of all civil work and approval of the final plat map. The city shall
have the option of sending plans out for review in which case fees will also include consultant
rates. (Ord. 2245 §2, 1999).
14.15.100 Construction standards and specifications.
The Director shall prepare, administer, and enforce detailed construction standards and
specifications for all on-site stormwater and erosion control facilities. (Ord. 2245 §2, 1999).
14.15.110 Review and approval of plans.
All storm drainage plans prepared in connection with any of the permits and/or approvals listed
in MMC 14.15.030 shall be submitted for review and approval by the Director or designee.
(Ord.2245 §2, 1999).
14.15.120 Inspections -Construction.
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All activities regulated by this chapter shall be inspected by the engineer and/or public works
department. Projects shall be inspected at various stages of the work 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 project. When required by the Director or
designee, a special inspection and/or testing shall be performed. The holder of any permit or
approval issued subject to a detailed drainage plan shall arrange with the engineer for scheduling
the following inspections:
(I)Initial Inspection. Whenever work on the site preparation, grading, excavations, or fill is
ready to be commenced, but in all cases prior thereto;
(2) Rough Grading. When all rough grading has been completed;
(3) Bury Inspection. Prior to burial of any.underground drainage structure;
(4) Finish Grading. When all work including installation of all drainage structures and other
protective devices has been completed;
(5) Planting. When erosion control planting shows active growth. In some circumstances not all
of the above inspections may be necessary.It shall be the discretion of the public works director
or designee to waive or combine any of the above inspections as dictated by conditions. The
public works director or designee shall inspect the work and shall either approve the same or
notify the applicant in writing in what respects there has been failure to comply with the
requirements of the approved plan. Any portion of the work which does not comply shall be
promptly corrected by the applicant. The public works director or designee may make
unscheduled site inspections to ensure compliance. Uncorrected violations will be subject to the
provisions ofMMC 14.15.190. (Ord. 2245 §2,1999).
14.15.130 Bonds and liability insurance required.
The department is authorized to require all persons constructing retention/detention or other
drainage treatment/abatement facilities to post surety or cash bonds. Where such persons have
previously posted, or are required to post, other such bonds on the facility itself or on other
construction related to the facility, such person may, with the permission of the public works
director or designee, and to the extent allowable by law, combine all such bonds into a single
bond; provided, that at no time shall the amount thus bonded be less than the total amount which
would have been required in the form of separate bonds; and provided further, that such a bond
shall on its face clearly delineate those separate bonds which it is intended to replace.
(I)Construction Bond. Prior to commencing construction, the person constructing the facility
shall post a construction bond in an amount sufficient to cover the cost of performing said
construction per the approved drainage plans. Alternatively, an equivalent cash deposit to an
escrow account administered by a local account bank may be allowed at the city's option.
(2) Maintenance Bond. After satisfactory completion of the facilities and release of the
construction bond by the city, the person constructing the facility shall commence a two-year
period of satisfactory maintenance of the facility. A cash bond to be used at the discretion of the
city, to correct deficiencies in said maintenance affecting public health, safety and welfare, must
be posted and maintained throughout the two-year maintenance period. The amount of the cash
bond shall be determined by the public works director or designee.In addition, at the discretion
of the city, a surety bond or cash bond to cover the cost of design defects or failures in
workmanship shall also be posted and maintained through the two-year maintenance period.
Alternatively, an equivalent cash deposit to an escrow account administered by a local account
bank may be allowed, at the city's option.
(3) Liability Policy. The person constructing the facility shall maintain a liability policy in an
amount to be determined by the city which shall name the city of Marysville as an additional
insured and which shall protect the city from any liability for any accident, negligence, failure of
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the facility, or any other liability whatsoever, relating to the construction or maintenance of the
facility. The liability policy shall be maintained for the duration of the facility by the owner of
the facility; provided, that in the case of facilities assumed by the city for maintenance pursuant
to MMC 14.15.140,the liability policy shall be terminated when the city maintenance
responsibility commences. (Ord.2245 §2, 1999).
14.15.140 City assumption of maintenance.
The city may assume the maintenance of retention/detention facilities after the expiration of the
two-year maintenance period if:
(1)AH of the requirements of this chapter have been fully complied with;
(2) The facilities have been inspected and approved by the department after two years of
operation;
(3)The surety bond required in MMC 14.15.130 has been extended for one year, covering the
city's first year of maintenance;
(4) All necessary easements entitling the city to properly maintain the facility have been
conveyed to the city. (Ord.2245 §2, 1999).
14.15.150 Retroactivity relating to city maintenance of drainage facilities.
If any person constructing retention/detention facilities and/or receiving approval of drainage
plans prior to the effective date ·of this chapter demonstrates, to the city's satisfaction, total
compliance with the requirements of this chapter, the city may, after inspection, approval, and
acknowledgment of the proper posting of the required bonds as specified in MMC 14.15.130,
assume maintenance of the facilities. (Ord.2245 §2, 1999).
14.15.160 Maintenance of drainage facilities by owner.
In the event that the city elects not to assume the operation and maintenance responsibility for
the facilities, it shall be the responsibility of the owner of the property, his heirs, successors and
assigns, to operate, maintain, repair and replace the facilities in continuous compliance with the
standards and specifications of the department. The Director or designee shall have authority to
periodically enter upon the property and inspect the facilities to insure such compliance. (Ord.
2245 §2, 1999).
14.15.165 Maintenance of drainage swales and ditches.
For provisions relating to the maintenance of drainage swales and ditches see MMC 14.17.030,
(Ord.2245 §2,1999).
14.15.170 Applicability to governmental entities.
All municipal corporations and governmental entities shall be required to submit a storm
drainage plan and comply with the terms of this chapter when developing and/or improving land
within the incorporated areas of the city of Marysvi11e or within adjacent areas which may affect
the city. (Ord.2245 §2, 1999).
14.15.175 Adjustments.
Adjustments to the Minimum Requirements may be granted prior to permit approval and
construction.Adjustments must be reviewed in the context of each application, site and potential
impacts. Approval does not establish precedent for subsequent applications that may reflect
different scale,complexity and site conditions. After receiving proper written application the
Director may grant an adjustment provided that a written finding of fact is prepared, that
addresses the following:
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1. The adjustment provides substantially equivalent environmentalprotection; and
2. The objectives of safety, function, environmental protection and facility maintenance, based
upon sound engineering, are met.
14.15.180 Exceptions
Exceptions to the Minimum Requirements may be granted prior to permit approval and
construction. Exceptions must be reviewed in the context of each application, site and potential
impacts. Approval does not establish precedent for subsequent applications that may reflect
different scale, complexity and site conditions. Application for an exception shall be filed in
writing with the Director and shall adequately detail the reason for an exception. The Director
shall provide a legal public notice of an application for an exception, and legal public notice of
the decision on the application. The Director may grant an exception from the requirements of
this Chapter provided a written finding of fact is prepared that supports that the following criteria
are met:
1. 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 site in question, and every effort to find creative ways to meet the intent of the minimum
standards has been made; and
2. That the granting of the exceptions will not be detrimental to the public health, welfare, and
safety, nor injurious to other properties in the vicinity and/or downstream, and to the quality
ofreceiving waters; and
3. The exception is the least possible exception that could be granted to comply with the intent
of the Minimum Requirements.
14.15.185 Additional procedures and review.
In various sections of this chapter, the public works director or designee, the city engineer, and
the city planner are empowered to impose requirements, give approvals, make determinations
and the like (hereinafter in this section "administrative determination(s)"). This section sets out
procedures for administrative determination(s). All administrative determination(s) shall be
made in a timely manner to satisfy all requirements of state law. All administrative
determination(s) shall be in writing and shall set out facts and conclusions to support the decision
made. All administrative determination(s) shall be made to achieve the purposes of this chapter
as set out in MMC 14.15.010. All administrative determination(s) may be appealed to the
hearing examiner by filing written notice of appeal with the city clerk within 10 days of service
of the administrative determination. (Ord. 2245 §2, 1999).
14.15.190 Enforcement.
Enforcement of the provisions of this chapter shall be pursuant to MMC Title 4. (Ord. 2245 §2,
1999).
14.15.200 No special duty created.
(1)It is the purpose of this chapter to provide for the health, welfare, and safety of the general
public, and not to create or otherwise establish or designate any particular class or group of
persons who will or should be especially protected or benefited by the terms of this chapter. No
provision or term used in this chapter is intended to impose any duty whatsoever upon the city or
any of its officers, agents, or employees for whom the implementation or enforcement of this
chapter shall be discretionary and not mandatory.
(2) Nothing contained in this chapter is intended to be, nor shall be, construed to create or form
the basis for any liability on the part of the city or its officers, agents, and employees for any
injury or damage resulting from the failure of any premises to abate a nuisance or to comply with
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Date of Publication:
.....,.,~
.the provisions of this chapter or by reason or as a consequence of any inspection,notice, or
order, in connection with the implementation or enforcement of this chapter, or by reason of any
action of the city related in any manner to enforcement of this chapter by its officers, agents, or
employees. (Ord. 2245 §2, 1999).
14.15.210 Severability.
If any section,subsection,sentence, clause, phrase, or word of this chapter should be held to be
invalid or unconstitutional by a court of competent jurisdiction,such invalidity or
unconstitutionality thereof shall not affect the validity or constitutionality of any other section,
subsection,sentence,clause, phrase, or word of this chapter. (Ord. 2245 § 2, 1999).
14.15.220 Appeals.
The decision of the Director may be appealed by an aggrieved party pursuant to MMC Title 15
to Hearing Examiner by filing written notice of appeal,including an appeal fee of $500, with the
City's Public Works Department or Community Development Department,within 10 days of
notice of the Director's decision.
PASSED by the City Council and APPROVED by the Mayor this I:L.f=A day of
/!Ary_---'-------',2003.
CITY OF MARYSVILLE
By r1djtJ~
DAVID A. ISER, M YOR
AU~~
By:c-KM/~cetCITY CLERK
Approved as to form:
BY:.~C~
GRANT K. WEED, CITY ATTORNEY
5/2-'(;/03
Effective Date:ft;/;;1 /0 3
(5 days after publication)I I
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