HomeMy WebLinkAbout141-97 - Ord. Adoption of the Stormwater Management Ordinance ORDINANCE NO. 141-97
ADOPTION OF THE
MASON COUNTY STORMW ATE R MANAGEMENT ORDINANCE
IN THE MATTER OF:
Adopting the Mason County Stormwater Management Ordinance to establish standard procedures of Mason County
departments in the review of proposed new development and redevelopment in the county;
WHEREAS,the 1994 Puget Sound Water Quality Management Plan(as amended)requires all counties and cities within the
Pu et Sound drainage basin to adopt ordinances to control runoff from new development and redevelopment by January 1,
1905; and
WHEREAS,the Plan directs local governments to adopt stormwater programs which include minimum requirements for new
development and redevelopment set by the Plan and in guidance developed by Ecology; and
WHEREAS,a stormwater management ordinance committee was appointed by the County Commissioners and was closely
involved in the preparation of a stormwater management ordinance;and
WHEREAS,the Mason County Board of Commissioners held public hearings on October 28, 1997 and on December 2, 1997
to receive public comments and finalize the text of the Mason County Stormwater Management Ordinance;and
WHEREAS, the.provisions of this ordinance are intended to guide and advise all who conduct new development or
redevelopment within Mason County;and
WHEREAS, The provisions of this ordinance establish the minimum level of compliance which must be met to permit a
property to be developed or redeveloped within Mason County;
NOW THEREFORE, BE IT ORDAINED THAT:
The Mason County Board of Commissioners hereby adopts the Mason County Stormwater Management Ordinance
(Attachment A)which establishes the standard procedures of Mason Countydepartments in the review of development and
redevelopment proposals in the county;the permit review process shallly to proposals filed on or after January 1, 1998.
PASSED this day of 1997
BOARD OF COUNTY COMMISSIONERS
MASON COUNTY,WASHINGTON
ATTEST:
M ry 0 y, Chairperson
A.1301ender, ommis
one r,
Cindy sen, Commissioner
ecc ogers, Clerk of the oard
O . D TO FORM:
-C Fierosecuting ATo-rney
Michael Clift
c: Clerk of the Board
Public Works File:H:\WP\STRMWrR\MC-COMM\ORD-141.97
MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
Ordinance No. 141-97
CONTENTS
SECTION 1: FINDINGS OF FACT, NEED AND PURPOSE. . . . . . . . . . . . . . 1
1. 1 Findings of fact. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1. 2 Need. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1. 3 Purpose. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
SECTION 2 : DEFINITIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
SECTION 3 : GENERAL PROVISIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3 . 1 Abrogation and greater restrictions. . . . . . . . . . . . . 11
3 . 2 Interpretation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
SECTION 4: APPLICABILITY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
SECTION 5: REGULATED ACTIVITIES AND ALLOWED ACTIVITIES. . . . 11
5. 1 Regulated Activities. . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-12
5. 2 Exemptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
SECTION 6: GENERAL REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6. 1 Stormwater Management Manual Adopted. . . . . . . . . . . . 12-13
6. 2 Stormwater Best Management Practices (BMPs) . . . . . 13
6. 3 Illicit Discharges. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
SECTION 7 : APPROVAL STANDARDS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7. 1 Small Parcel Minimum Requirements . . . . . . . . . . . . . . 13
7 . 1. 1 Small Parcel Requirement #1
Construction Access Route . . . . . . . . . . . . 13-14
7. 1. 2 Small Parcel Requirement #2
Stabilization of Potentially Erodible Denuded Areas 14
7 . 1. 3 Small Parcel Requirement #3
Protection of--Adjacent Properties . . . . . . . . . . . . . 14
7 . 1. 4 Small Parcel Requirement #4
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7 . 1 . 5 Small Parcel Requirement #5
OtherBMPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7 . 2 New Development and Redevelopment
Minimum Standards . . . . . . . . . . . . . . . . . . . . . . . . . 14
7 . 2 . 1 New Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-15
7 .2 . 2 Redevelopment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-16
7 . 2 . 3 Minimum Requirement #1
Erosion and Sediment Control . . . . . . . . . . . . . . 16-19
7 . 2 . 4 Minimum Requirement #2
Preservation of Natural Drainage Systems 20
7 . 2 . 5 Minimum Requirement #3
Source Control of Pollution . . . . . . . . . . . . . . 20
7 . 2 . 6 Minimum Requirement #4
Runoff Treatment BMPs . . . . . . . . . . . . . . . . . . . . . 20-21
7 . 2 . 7 Minimum Requirement #5
Streambank Erosion Control . . . . . . . . . . . . . . . . 21
MASON COUNTY STORM4ATER MANAGEMENT ORDINANCE - ATTACHMENT A
Ordinance No. I4I-97
CONTENTS (cont. )
7 . 2 . 8 Minimum Requirement #6
Wetlands . . . . . . . . . ~ . . ~ ~ ~ ~ ~ ~ . ~ . ^ . . . ~ ~ . . . . . . . 21
7 . 2 . 9 Minimum Requirement #7
Water Quality Sensitive Areas . . . . . . . . . . . . . 22
7 . 2 . I0 Minimum Requirement #8
(}ffsite Analysis & Mitigation . . . . . . . . . . . . . 33-23
7 ' 2 . I1 Minimum Requirement #9
Basin Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7 . 2 . 12 Minimum Requirement #lO
Operation and Maintenance . . . . . . . . . . . . . . . . . 23-24
7 .2 . 13 Minimum Requirement #lI
F1rzaoc1aI Liability . . . . . . . . . ~ . ~ ~ . . . . . . . . . . 24
7 . 2 ' I4 Variances From These Staodardo. . ' . . ' . . - ~ ' ' . . - - 24
7 . 2 . 15 Experimental BMPs . . ~ . . . . . . ~ . . . ~ . ^ . ~ . ~ . . . . . . . . 24-25
7 . 2 . 15. 1 Approval of Experimental BMPs . . . . . . . . . . . . . . 25
SECTION 8 : ADMINISTRATION ' ' ' . . ' ' . . ' ' ~ . ' ^ . ' ' . ' ' . . ' ~ . ' . . . . . 25
8 . 1 Director . . . . . . . , . . - . . . ' ~ . . . . . . . . . . . ' ' ~ . . . . . . . . . 25
8 . 2 Review and Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8 . 3 Enforcement Aothoz-itv. . . . . . . . . . . . . ~ ~ . . ~ . . . . . . , . . 25
8 . 4 Inspection . . . . . . . . . . ~ . ~ . . ~ . . . . . . ~ . . ~ . . . ~ . . . . . . , 26
SECTION 9 : ENFORCEMENT . . . . . . . . ~ ~ . . . ~ . . . . ~ ~ ~ ~ . . ~ . . ~ . . . . . . . 26
9 ~ 1 General , . . . . . . . . . . ~ . ~ . . . . ~ . . ~ . . . . . . . . . ~ . ~ . . . . . . 26
9 .2 Stop Work Order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
9 . 3 Civil Penalty . . . . . . . . . . . . . . ^ ' . . . . . ' . . ~ . . . . . . . . . 27
9 . 3 . 1 Penalties Doe . ' . ' . . . . . . . ' . ~ . . ' ' . ^ ' ~ ^ ^ . . . . 27-28
9. 3 . 2 Penalty Recovered . . . . ' . . . . . . . ^ ^ . . . , . . . . . . 28
SECTION lO : EXCEPTIONS . ' ' . . . . . . . , . . ~ ^ ' . . ^ . ~ ^ ' , ~ . . . . . . . ' . . 28
-- 10. 1 }liobt of Appeal . . . . . . . . . . . . . . . ^ ~ . ~ . ^ . ^ . . . . . . . . . 28
IO 2 Findings f Fact
SON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
CTI 1: FINDINGS OF FACT, NEED AND PURPOSE
1.1 Findingsof Fact
The Board of Mason County Commissioners of Mason County hereby finds
that:
A. The 1994 Puget Sound Water Quality Management Plan (as amended)
requires all counties and cities within the Puget Sound drainage
basin to adopt ordinances to control runoff from new development
and redevelopment by January 1, 1995. The Plan also directs
local governments to adopt stormwater programs which include
minimum requirements for new development and re-development set
by the Plan and in guidance developed by Ecology.
B. Stormwater is a problem associated with land utilization and
development and common occurrence of potential pollutants such
as pesticides, fertilizers, petroleum products, animal wastes
and numerous others.
Land utilization and development is also known to increase both
the volume and duration of peak flows. The resulting erosion,
scouring, and deposition of sediment affect the ecological
balance in the stream.
Sedimentation and stormwater pollution cause diversity of
species to decrease and allows more tolerant (and usually less
desirable) species to remain.
Stormwater pollution can cause or contribute to closures of
shellfish beds and swimming beaches and other restrictions on
public use of the waters within Mason County.
C. An expanding population and increased development of land have
led to:
water quality degradation through discharge of nutrients,
metals , oil and grease, toxic materials, and other detrimental
substances including, without limitation, insect and weed
control compounds;
drainage and storm and surface water runoff problems within
Mason County; and
safety hazards to both lives and property posed by uncontrolled
water runoff on streets and highways.
D. Continuation of present stormwater practices, to the extent that
they exist, will lead to water quality degradation, erosion,
property damage, and endanger the health and safety of the
inhabitants of the County.
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
E. In the future such problems and dangers will be reduced or
avoided if existing properties and future developers, both
private and public, provide for stormwater quality and quantity
controls.
F. Stormwater quality and quantity controls can be achieved when
land is developed or redeveloped by implementing appropriate
best management practices (BMPs) .
G. Best management practices can be expected to perform as intended
only when properly designed, constructed and maintained.
1.2 NEED
The County finds that this chapter is necessary in order to:
A. Satisfy the mandate of Ecology as identified in Section 1. 1 A.
B. Minimize or eliminate water quality degradation.
C. Prevent erosion and sedimentation in creeks, streams, ponds,
lakes and other water bodies.
D. Protect property owners adjacent to existing and developing
lands from the undesirable impacts of increased runoff rates.
E. Preserve and enhance the suitability of waters for contact
recreation, fishing, and other beneficial uses.
F. Preserve and enhance the aesthetic quality of the water.
G. Promote sound development policies which respect and preserve
County surface water and sediment.
H. Ensure the safety of County roads and rights-of-way.
I. Decrease stormwater-related damage to public and private
property from existing and future runoff.
J. To protect the health, safety and welfare of the inhabitants of
the County.
1.3 PURPOSE
The provisions of this ordinance are intended to guide and advise all
who conduct new development or redevelopment within Mason County. The
provisions of this ordinance establish the minimum level of compliance
which must be met to permit a property to be developed or redeveloped
within Mason County.
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
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 groundwater 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 County stormwater infrastructure and
those downstream;
H. Provide a means of regulating clearing and grading of private
and public land while minimizing water quality impacts; and
I. Provide guidance on development and construction procedures
which will encourage the preservation of existing natural
vegetation to the maximum extent practicable.
SECTION 2 : DEFINITIONS
For the purposes of this chapter, the following- definitions shall
apply:
a. "American Public Works Association" or 11APWA11 means the adopted
edition of the Washington State Chapter of the American Public Works
Association.
b. "Approval" means the proposed work or completed work conforms to
this chapter in the opinion of the Director.
c. "As-graded" means the extent of surface conditions on completion
of grading.
d. "Basin plan" means a plan and all implementing regulations and
procedures including but not limited to land use management adopted
by ordinance for managing surface and stormwater management facilities
and features within individual sub-basins.
e. "Bedrock" means the more or less solid rock in place either on or
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
beneath the surface of the earth. It may be soft, medium, or hard and
have a smooth or irregular surface.
f. "Bench" means a relatively level step excavated into earth material
on which fill is to be placed.
g. "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.
h. "Buffer" means the zone contiguous with a sensitive area that is
required for the continued maintenance, function, and structural
stability of the sensitive area. The critical functions of a riparian
buffer (those associated with an aquatic system) include shading,
input of organic debris and coarse sediments, uptake of nutrients,
stabilization of banks, interception of fine sediments, overflow
during high water events, protection from disturbance by humans and
domestic animals, maintenance of wildlife habitat, and room for
variation of aquatic system boundaries over time due to hydrologic or
climatic effects. The critical functions of terretrial buffers include
protection of slope stability, attenuation of surface water flows from
storm water runoff and precipitation, and erosion control.
I. "Civil Engineer" means a professional engineer licensed in the
State of Washington in Civil Engineering. -
j . "Civil Engineering" means the application of the knowledge of the
forces of nature, principles of mechanics and the properties of
materials to the evaluation, design and construction of civil works
for the beneficial uses of mankind.
k. "Clearing" means the destruction and removal of vegetation by
manual, mechanical, or chemical methods.
1. "Commercial agriculture" means those activities conducted on lands
defined in RCW 84. 34.020 (2) , and activities involved in the production
of crops or livestock for wholesale trade. An activity ceases to be
considered commercial agriculture when the area on which it is
conducted is proposed for conversion to a nonagricultural use or has
lain idle for more than five (5) 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.
m. "Compaction" means densification of a fill by mechanical means.
n. "Critical Areas" means, at a minimum, areas which include wetlands,
areas with a critical recharging effect on aquifers used for potable
water, fish and wildlife habitat conservation areas, frequently
flooded areas, geologically hazardous areas, including unstable
slopes, and associated areas and ecosystems.
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
O. "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. )
p. "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.
q. "Detention facility" means an above ground 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.
r. "Director" means the Mason County Public Works Director or a
designee who shall administer this ordinance.
s . "Drainage basin" means a geographic and hydrologic subunit of a
watershed.
t. "Earth material" means any rock, natural soil or fill and/or any
combination thereof.
u. "Ecology" means the Washington State Department of Ecology.
V. "Engineering geologist" means a geologist experienced and
knowledgeable in engineering geology.
w. "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.
x. "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.
y. "Excavation" means the mechanical removal of earth material.
z . "Existing site conditions" means
(1) For developed site with stormwater facilities that have
been constructed to meet standards in the Minimum
Requirements of this ordinance, 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
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
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 as
identified under Minimum Requirement #7, Water Quality
Sensitive Areas, 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.
aa. "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.
bb. "Fill" means a deposit of earth material placed by artificial
means.
cc. "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.
dd. "Frequently flooded areas" means the 100-year floodplain
designation of the Federal Emergency Management Agency and the
National Flood Insurance Program.
ee. "Geologically hazardous areas" means areas that because of their
susceptibility to erosion, sliding, earthquake or other geological
events, are not suited to the siting of commercial, residential or
industrial development consistent with public health or safety
concerns.
ff. "Grade" means the slope of a road, channel, or natural ground. The
finished surface of a canal bed, roadbed, top of embankment, or bottom
of excavation; any surface prepared for the support of construction
such as paving or the laying of a conduit.
(1) Existing Grade. The grade prior to grading.
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
(2) Rough Grade. The stage at which the grade approximately
conforms to the approved plan.
(3) Finish Grade. The final grade of the site which conforms to
the approved plan.
gg. "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 suitable outlet at a nonerosive velocity.
hh. (To) "Grade" means to finish the surface of a canal bed, roadbed,
top of embankment or bottom of excavation.
ii. "Ground water" means water in a saturated zone or stratum beneath
the surface of land or beneath a surface water body.
ji . "Hydroperiod" means the seasonal occurrence of flooding and/or
soil saturation; it encompasses depth, frequency, duration, and
seasonal pattern of inundation.
kk. "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, roof tops, walkways, patios, driveways,
parking lots or storage areas, concrete or asphalt paving, gravel
roads, packed earthen materials, and oiled, macadam or other surfaces
which similarly impede the natural infiltration of stormwater. Open,
uncovered retention/detention facilities shall not be considered as
impervious surfaces.
11 . "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
greywater systems.
mm. "Interflow" means that portion of rainfall that infiltrates into
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.
nn. "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.
oo. "Large Parcel Erosion and Sediment Control Plan" or "Large Parcel
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
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.
pp. "Manual" means the latest edition of Washington State Ecology's
Stormwater Management Manual for the Puget Sound Basin. Other terms
frequently used to mean "the Manual" include; the PSWQA Manual, and
the Technical Manual. The Manual is adopted with exceptions in Section
6. 1 of Mason County's Stormwater Management Ordinance.
qq. "Mitigation means, in the following order of preference:
(a) Avoiding the impact altogether by not taking a certain
action or part of an action;
(b) 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;
(c) Rectifying the impact by repairing, rehabilitating or
restoring the affected environment;
(d) Reducing or eliminating the impact over time by
preservation and maintenance operations during the life of
the action; and
(e) Compensation for the impact by replacing, enhancing, or
providing substitute resources or environments.
rr. "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.
ss. "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.
tt. "Person" means any individual, partnership, corporation,
association, organization, cooperative, public or municipal
corporation, agency of the state, or local government unit, however
designated.
uu. "Pollution" means contaminated or other alteration of the
physical, chemical, or biological properties, of waters of the state,
including change in temperature, taste, color, turbidity, or odor of
the waters, or such discharge of any liquid, gaseous, solid,
radioactive or other substance into any waters of the state as will
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
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®
vv. "Project Engineer" means, the proponent' s Engineer or Engineer's
representative who directly supervises the engineering and
administration of a construction project®
ww. "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.
xx. "Regional retention/detention system" means a stormwater quantity
control structure designed to correct existing excess surface water
runoff problems of a basin or sub-basin. The area downstream has been
previously identified as having existing or predicted significant and
regional flooding and/or erosion problems. This term is also used when
a detention facility is used to detain stormwater runoff from a number
of different businesses, developments or areas within a catchment.
yy. "Retention/detention facility (R/D) II 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.
zz. "Site: " means the portion of a piece of property which is directly
subject to development.
aaa. "Slope" means the degree of deviation of a surface from the
horizontal ; measured as a numerical ratio, percent, or in degrees.
Expressed as a ratio, the first number is the horizontal distance
(run) and the second is the vertical distance (rise) , as 2 : 1. A 2 : 1
slope is a 50 percent slope. Expressed in degrees, the slope is the
angle from the horizontal plane, with a go, slope being vertical
(maximum) and a 450 being a 1: 1 or 100 percent slope.
bbb. "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. Guidance for preparing a Small Parcel
ESC Plan is contained in the Manual.
ccc. :Soil" means the unconsolidated mineral and organic material on
the immediate surface of the earth that serves as a natural medium for
growth of land plants®
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
ddd. "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.
eee. "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.
fff. "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.
ggg. "Stormwater facility" means a constructed component of a
stormwater drainage system, designed or constructed to perform a
particular function, or multiple functions. Stormwater facilities
include, but are not limited to, pipes, swales, ditched, culvert,
street gutters, detention basins, constructed wetlands, infiltration
devices, catchbasins, oil/water separators, sediment basins and
modular pavement.
hhh. "Stormwater Management Manual" or "Manual" means the Manual, with
the exception of Vol. l Chapter 2, adopted by reference and prepared
by Ecology that contains BMPs to prevent or reduce pollution.
iii. "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 in an excavation, cut, or
fill where the lower surface changes to horizontal or meets the
existing ground slope.
kkk. "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.
111. "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.
mmm. "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.
nnn. "Water body" means surface waters including rivers, streams,
lakes, marine waters, estuaries, and wetlands.
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
000. "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.
ppp. "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
on the site that are not wetlands: Irrigation and drainage ditches,
grass-lined swales, canals, agricultural detention facilities, farm
ponds, and landscape amenities.
qqq. "Vegetation" means all organic plant life growing on the surface
of the earth.
SECTION 3: GENERAL PROVISIONS
3. 1 Abrogation and greater restrictions
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.
3.2 Interpretation
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.
SECTION 4: APPLICABILITY
Regulated activities shall be conducted only after Mason County Public
Works approves a Stormwater site Plan which includes one or more of
the following as required by this chapter:
A. Small Parcel Erosion and Sediment Control (ESC) Plan
B. Large Parcel Erosion and Sediment Control (ESC) Plan
C. Permanent Stormwater Quality Control (PSQC) Plan
SECTION 5: REGULATED ACTIVITIES AND ALLOWED ACTIVITIES
5. 1 Regulated activities
Consistent with the minimum requirements contained in this chapter,
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
the Director or their designee shall approve, conditionally approve,
or disapprove the following activities, unless exempted in Section 5.2
below:
A. New Development
(1) land disturbing activities;
(2) structural development, including construction;
installation or expansion of a building or other structure;
(3) creation of impervious surfaces;
(4) Class IV general forest practices that are conversions from
timber land to other uses;
(5) subdivision, short subdivision and binding site plans, as
defined in CH. 58. 17 . 020 RCW.
B. Redevelopment
(1) 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 associated with structural or impervious
redevelopment.
5.2 Exemptions
Commercial agriculture, and forest practices regulated under Title 222
WAC, except for Class IV General forest practices that are conversions
from timber land to other uses, are exempt from the provisions of this
chapter.
Development undertaken by the Washington State Department of
Transportation in state highway right-of-way is regulated by Chapter
173-270 WAC, the Puget Sound Highway Runoff Program.
All other new development and redevelopment is subject to the minimum
requirements of this chapter.
SECTION 6: GENERAL REQUIREMENTS
6. 1 Stormwater Management Manual adopted
The latest edition of Ecology's Stormwater Management Manual with the
exception of the Minimum Requirements Chapter, Volume I, Chapter 2,
is hereby adopted by reference and is hereinafter referred to as the
Manual. The use of other manuals or methods shall be pre-approved by
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE ® ATTACHMENT A
the Director or their designee.
6.2 So grater Best Management Practices (BMPs)
General: BMPs shall be used to control pollution from stormwater. BMPs
shall be used to comply with the standards in this Ordinance. BMPs are
in the Manual .
Farm Plan BMPs: For new development that will include "hobby farm"
elements such as pastures, corrals, etc, farm plan BMPs are
recommended (not required) for incorporation into the site design.
Contact Mason County' s Public Works Department or the Mason
Conservation District for further farm plan guidance.
Experimental BMPs: In those instances where appropriate BMPs are not
in the Manual, experimental BMPs should be considered. Experimental
BMPs are encouraged as a 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 outline in the Manual.
6.3 Illicit discharges
Illicit discharges to stormwater drainage systems are prohibited.
SECTION 7 : APPROVAL STANDARDS
7 . 1 Small parcel Minimum requirements
• The following new development shall be required to control
erosion and sediment during construction, to permanently
stabilize soil exposed during construction, to comply with Small
Parcel Requirements 1 through 4, to prepare a Small Parcel
Erosion and Sediment Control Plan, and may need to prepare a
Small Parcel Drainage Plan/Sketch (Mason County's Public Works
Department can provide additional instructions, guidance, and
examples if a Small Parcel Drainage Plan is deemed necessary) :
(a) Individual, detached, single family residences and
duplexes.
(b) Creation or addition of less than 5, 000 square feet of
impervious surface area.
(c) Land disturbing activities of less than one acre.
7. 1. 1 SMALL PARCEL REQUIREMENT #1 Construction Access Route
0 Construction vehicle access shall be, whenever possible, limited
to one route. Access points shall be stabilized to minimize the
tracking of sediment onto public roads.
0 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
13
MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
onto a road surface creating a hazard, the roads shall be
cleaned immediately, and thoroughly cleaned 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.
7 . 1.2 SMALL PARCEL REQUIREMENT #2 Stabilization of Potentially
Erodible Denuded Areas
• Soil stabilization. All exposed and unworked soils with erosion
potential 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 1 through
April 30, no soils shall remain exposed for more than 2 days.
From May 1 through September 30, no soils shall remain exposed
for more than 7 days.
7.1.3 SMALL PARCEL REQUIREMENT #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.
7 . 1.4 SMALL PARCEL REQUIREMENT #4 Maintenance
• All erosion and sediment control BMPs shall be regularly
inspected and maintained by the owner or authorized agent to
ensure continued performance: of their intended function.
7 . 1.5 SMALL PARCEL REQUIREMENT #5 Other BMPs
• As required by the Director, other appropriate BMPs to mitigate
the effects of increased runoff shall be applied.
7.2 NEW DEVELOPMENT AND REDEVELOPMENT - MINIMUM REQUIREMENTS
Development exceeding 5000 square feet of impermeable surfacing,
and land disturbing activities of one acre or more must have the
Large Parcel ESC Plan (if required) and the Permanent Stormwater
Quality Control (PSQC) Plan (if required) prepared and stamped
by a licensed civil engineer.
7.2 . 1 New Development
A. All new development that includes the creation or addition of
5, 000 square feet, or greater, of new impervious surface area,
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE ® ATTACHMENT A
and/or land disturbing activity of one acre or greater, shall
comply with Minimum Requirements #1 through #11 in Sections
7 .2 . 3 through 7.2. 13 .
Compliance shall be demonstrated through 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
5, 000 square feet, or greater, of new impervious surface area,
and land disturbing activity of less than one acre, shall comply
with Minimum Requirements #2 through #11 in Sections 7 . 2 . 4
through 7.2. 13 and the Small Parcel Minimum Requirements found
in section 7 . 1 above. This category of development shall also
prepare a Stormwater Site Plan that includes a Small Parcel
Erosion and Sediment Control Plan.
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.
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.
7.2.2 Redevelopment
A. Where redevelopment of �! 5, 000 square feet occurs:
The new development Minimum Requirements #1 through #11,
Sections 7.2 . 3 through 7.2 . 13 , 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. A Stormwater Site Plan shall
be prepared.
B. In addition to the above requirements, where one or more of the
following conditions apply, a Stormwater Site Plan shall also 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 #9) may be used to develop redevelopment
requirements that are tailored to a specific basin.
1 . Existing sites greater than 1 acre in size with 50% or more
impervious surface.
2 . 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:
is
MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
(I) Listed in reports required under section
305(b) of the Clean Water Act, and
designated as not supporting beneficial
uses;
(ii) Listed under section 303 (d) of the Clean
Water Act as not expected to meet water
quality standards or water quality goals;
(iii) 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.
3 . Sites where the need for additional stormwater control
measures has been identified through a basin plan, the
watershed ranking process under Ch. 400-12 WAC, or
through Growth Management Act planning.
7 .2.3 MINIMUM REQUIREMENT #1: EROSION AND SEDIMENT CONTROL
• All new development and redevelopment that includes land
disturbing activities of one acre or greater shall comply with
Erosion and Sediment Control Requirements 1 through 14, below.
Compliance with the Erosion and Sediment Control Requirements
shall be demonstrated through implementation of a Large Parcel
Erosion and Sediment Control Plan.
All new development and redevelopment that includes land
disturbing activities of <1 acre shall comply with the Small
Parcel Minimum requirements found in section 7 . 1, above.
Compliance with the Small Parcel Requirements shall be
demonstrated through implementation of a Small Parcel Erosion
and Sediment Control Plan.
The following erosion and sediment control requirements shall be
met:
A. EROSION AND SEDIMENT CONTROL REQUIREMENT #1: Stabilization
and Sediment Trapping
• All exposed and unworked soils shall be stabilized by suitable
application of BMPs. From October 1 to April 30, no exposed
and unworked soils shall remain unstabilized for more than 2
days. From May 1 to September 30 , no exposed and unworked
soils shall remain unstabilized for more than 7 days. Prior
to leaving the site, stormwater runoff shall pass through a
sediment pond or sediment trap, or other appropriate BMPs.
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
B. EROSION AND SEDIMENT CONTROL REQUIREMENT #2 : Delineate
Clearing and Basement Limits
0 In the field, mark clearing limits and/or any easements,
setbacks, sensitive/critical areas and their buffers, trees
and drainage courses.
C. EROSION AND SEDIMENT CONTROL REQUIREMENT #3 : Protection of
Adjacent Properties
Properties adjacent to the project site shall be protected
from damage by sediment deposition.
D. EROSION AND SEDIMENT CONTROL REQUIREMENT #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 #1 .
E. EROSION AND SEDIMENT CONTROL REQUIREMENT #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 #1.
Supplemental Guidelines: Consideration should be given to the
length and steepness of the slope, the soil type, upslope
drainage area, ground water conditions, and other applicable
factors. Slopes which are found to be eroding excessively
within two years of construction must be provided with
additional slope stabilizing measures until the problem is
corrected.
1. Roughened soil surfaces are preferred to smooth surfaces on
slopes (see BMP E2 . 35 in Chapter 11-5) .
2 . Interceptors (see BMP E2 . 55 in Chapter 11-5) should be
constructed at the top of long steep slopes which have
significant drainage areas above the slope. Diversions or
terraces may also be used to reduce slope length.
3 . Concentrated stormwater should not be allowed to flow down cut
or fill slopes unless contained within an adequate
temporary or permanent channel, or pipe slope drain (see
BMP E2 . 25 in Chapter 11-5) .
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
4 . Wherever a slope face crosses a water seepage plane which
endangers the stability of the slope, adequate drainage or
other protection should be provided (BMPs E2 .30 and E2.75 in
Chapter II-5) .
F. EROSION AND SEDIMENT CONTROL REQUIREMENT #6: Controlling Off-
site Erosion
• Properties and waterways downstream from development sites
shall be protected from damage by erosion due to increases in
the volume, velocity, or peak flow rate of stormwater runoff
from the project site.
G. EROSION AND SEDIMENT CONTROL REQUIREMENT #7: Stabilisation 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 the peak flow from a 2-year, 24-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.
H. EROSION AND SEDIMENT CONTROL REQUIREMENT #8: Storm Drain
Inlet Protection
• All storm drain inlets made operable during construction shall
be protected so that stormwater runoff shall not be discharged
offsite or be introduced into any fill area without first
being filtered or otherwise treated to remove sediment.
I. EROSION AND SEDIMENT CONTROL REQUIREMENT #9: Underground
Utility Construction
• The construction of underground utility lines shall be subject
to the following criteria:
(I) No more than 500 feet of trench shall be opened at one
time, unless provisions are made to protect against
adverse stormwater impacts.
(ii) Where consistent with safety and space considerations,
excavated material shall be placed on the uphill side of
trenches.
(iii) Trench dewatering devices shall discharge into a sediment
trap or sediment pond.
J. EROSION AND SEDIMENT CONTROL REQUIREMENT #10: Construction
Access Routes
• Construction vehicle access shall be, whenever possible,
18
MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
limited to one route. Access points shall be stabilized to
minimize the tracking of sediment onto public roads.
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 creating a hazard, the roads
shall be cleaned immediately, and thoroughly cleaned 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.
X. EROSION AND SEDIMENT CONTROL REQUIRE14ENT #11: Removal of
Temporary 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 shall be
permanently stabilized.
L. EROSION AND SEDIMENT CONTROL REQUIREMENT #12: Devatering
Construction Sites
• Trench dewatering devices shall be discharged in a manner that
will not adversely affect flowing streams, drainage systems or
offsite property. Water discharged from dewatering pumps shall
be routed through a sediment pond or trap unless it is clear.
M. EROSION AND SEDIMENT CONTROL REQUIREMENT #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.
N. EROSION AND SEDIMENT CONTROL REQUIREMENT #14 : Maintenance
• All temporary and permanent erosion and sediment control BMPs
shall be maintained and repaired as needed and in a timely
manner to assure continued performance of their intended
function. All maintenance and repair shall be conducted in
accordance with an approved manual.
O. EROSION AND SEDIMENT CONTROL REQUIREMENT #15: Financial
Liability
0 Performance bonding, or other appropriate instruments, may be
required to ensure compliance with the approved erosion and
sediment control plan.
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
7 .2.4 MINIMUM REQUIREMENT #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 extent practicable.
7.2 .5 MINIMUM REQUIREMENT #3: SOURCE CONTROL OF POLLUTION
• 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.
An adopted and implemented basin plan (Minimum Requirement #9)
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.
7 .2 . 6 MINIMUM REQUIREMENT #4: RUNOFF TREATMENT BMPS
0 All projects shall provide treatment of stormwater. Treatment
BMPs shall be sized to capture and treat the water quality
storm, defined as the 6 month, 24 hour storm. The first
priority for treatment of stormwater shall be to infiltrate as
much as possible of the water quality design storm into the
ground. (Infiltration BMP' s practices shall be in accordance
with Chapter III-3 of the PSWQA Manual) Pretreatment of
stormwater prior to infiltration into the ground may be
required in cases where:
1. The stormwater contains high concentrations of undesirable
dissolved chemicals that can move through soil.
2 . The stormwater contains large amounts of sediment that
might clog the infiltrative surfaces in the basin.
3 . The soils are extremely pervious and will not properly
filter the stormwater as in the case for some gravelly (Type
One) soils.
Stormwater treatment BMPs shall not be built within a natural
vegetated buffer, except for necessary conveyance systems as
approved by the Director.
An adopted and implemented basin plan (Minimum Requirement #9)
may be used to develop runoff treatment requirements that are
tailored to a specific basin.
The objectives of providing stormwater treatment BMPs are, for
both surface and ground waters, to protect the quality and
quantity, to allow attainment of the designated uses, and to
20
MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
meet state standards promulgated under Chapter 173 of the
Washington Administrative Code.
7 .2.7 MINIMUM REQUIREMENT #5- STREAKBANK EROSION CONTROL
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 in Minimum Requirement #4, Runoff Treatment BMPs:
Stormwater discharges to streams shall control streambank
erosion by limiting the peak rate of runoff from individual
development sites to 50 percent of the existing condition 2-
year, 24-hour design storm while maintaining the existing
condition peak runoff rate for the 10-year, 24-hour and loo-
year, 24-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 .
Stormwater treatment BMPs shall not be built within a natural
vegetated buffer, except for necessary conveyance systems as
approved by the Director, and maintained according to the
Manual.
An adopted and implemented basin plan (Minimum Requirement #9)
may be used to develop streambank erosion control requirements
that are tailored to a specific basin.
7.2.8 MINIMUM REQUIREMENT #6: WETLANDS
• Stormwater discharges to wetlands shall maintain the wetland's
natural hydroperiod and flows to the extent needed to preserve
or enhance its existing functions and values. Prior to
proposing discharge of higher volumes of stormwater to a
wetland, alternative discharge, detention, and infiltration
practices located in areas outside the wetland shall be
evaluated and employed by the Project Engineer where feasible
and practicable.
These requirements apply to existing natural wetlands and
wetlands created as mitigation for loss of wetland acreage.
Wetlands constructed and operated solely for use as stormwater
treatment / storage areas are exempt from these and most other
restrictions that apply to natural wetlands. Constructed
wetlands may lose this exemption if not operated and
maintained as stormwater areas for three or more years. Other
local, state, or federal wetland protection requirements may
also apply.
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
7 .2.9 MINIMUM REQUIREMENT #7: RATER QUALITY SENSITIVE AREAS
• Where the Mason County Commissioners or their designee
determine 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 to protect water quality.
An adopted and implemented basin plan (Minimum Requirement #9)
may be used to develop requirements for water quality
sensitive areas that are tailored to a specific basin.
7 .2 . 10 MINIMUM REQUIREMENT 48: OFF-SITE ANALYSIS AND MITIGATION
• DOWNSTREAM ANALYSIS MAY TRIGGER ADDITIONAL REQUIREMENTS
The Project Engineer shall provide a detailed qualitative
analysis of the flow path of the discharge from the project
site to the receiving water. This requirement shall apply to
all projects where a Drainage and Erosion Control Plan is
prepared, including those proposing retention facilities. This
analysis shall include flow routing, and provide existing pipe
and channel sizes and estimated capacities. In addition, the
Project Engineer shall discuss any known or expected
downstream erosion, flooding, or water quality problems,
including those that may be caused by interflow from the
proposed retention facility. The Director or designee shall
have the discretion to specify the distance and level of
detail to be provided by the Project Engineer. In making this
determination, the Director or designee shall consider such
factors as the relative size of the new development,
availability of other hydrologic work for the drainage area,
and the extent to which stormwater generated on the project
site is to be infiltrated.
Based upon this analysis, --the Project Engineer may determine
or the Director or designee may require that a quantitative
analysis of the conveyance system be performed both upstream
and downstream of the project site. A quantitative analysis
will not be required for most projects that propose to
infiltrate most or all stormwater. This analysis shall
determine conveyance system performance for the appropriate
design event(s) both with and without the proposed
development. The Director or designee shall have the
discretion to specify the distance and level of detail to be
provided by the Project Engineer. The Director or designee
shall consider factors such as the relative size of the new
development, availability of other hydrologic work for the
drainage area, and the results of the qualitative analysis, in
making this determination.
The quantitative downstream analysis will include modeling the
hydraulics of the proposed project and all other sources of
runoff tributary to the receiving water body for the
22
MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
appropriate Design Event. The Project Engineer shall include
an analysis of the impact of the 24-hour, 100-year event (in
addition to "Design Event" analysis) for each component of the
system including pond spillway.
The Director or designee may impose stricter discharge and/or
detention standards if the discharge from the project,
evaluated in the context of other existing conditions in the
drainage area, is reasonably expected to result in any of the
following:
0 Flooding
0 Loss of aquatic habitat due either to high or low flows
• Property Damage
• Water quality problems
• Erosion
0 Or an unacceptable interruption of vital services
If the Project Engineer (or Director or designee) determines
that greater treatment, infiltration and/or storage volumes
lower release rates, or downstream improvements are needed, '
he/she shall specify project design criteria or other means to
relieve the downstream problems (providing that such solution
will not violate minimum standards established in the Manual) .
Other means might include increases in downstream flow
capacity and/or offsite detention and infiltration facilities,
plans and financing for which will be subject to the approval
of the Director or designee.
7 .2 . 11 MINIMUM REQUIREMENT #9: BASIN PLANNING
0 Basin Plan Supersedes Manual .
If a proposed Project is located in a basin or subbasin for
which the County has an adopted basin plan, stormwater
requirements specifically identified in the basin plan shall
take precedence over those provided in this ordinance.
However, all other elements detailed in this Ordinance shall
continue to apply to such projects. Basin Plans are required
to be developed according to an approved manual .
7 .2 . 12 MINIMUM REQUIREMENT #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. An operation and Maintenance (O&M) Covenant will
be required to cover all privately owned and maintained
stormwater facilities approved by the Director. O&M Covenant
forms are available at the Mason County Public Works office. A
copy of the completed instrument, shall be recorded with the
County Auditors ' Office by the proponent, and a copy of the
recorded instrument is required to be submitted to the Public
23
MASON COUNTY STOR14WATER MANAGEMENT ORDINANCE - ATTACHMENT A
Works Department prior to final approval of the completed
permanent stormwater facilities.
7.2.13 MINIMUM REQUIREMENT #11: FINANCIAL LIABILITY
• Performance bonding, or other appropriate instruments shall be
required for all projects to ensure compliance with these
standards.
7.2 .14 VARIANCES FROM THESE STANDARDS
0 Variances from these standards may be allowed at the
discretion of the Director or designee provided that the
Proponent will substantially meet flow control and water
quality goals established by or implicit in these standards.
Compliance with Ordinance requirements shall normally occur
within the project area, but may be performed as offsite
mitigation in certain situations. Examples of cases when
variances may be approved include, but are not limited to, the
following:
O That the special conditions and circumstances exist
which are peculiar to the land, such as size, shape,
topography, or location, and that literal
interpretation of these standards would deprive the
property owner of rights commonly enjoyed by other
properties similarly situated; OR
o That the site is being remodeled and certain site
investigations would be destructive to existing
structures; OR
o That remodels of existing projects which are either
too small or so configured that in the Director's or
designee's opinion some requirements of the manual
cannot practically be met; OR
o That public works or private sector projects are in
an existing road right-of-way which is not of
adequate size to install preferred BMPs and for
which right-of-way cannot be expanded because of
encroaching structures or setbacks for existing
structures.
All requests for variances must be submitted in writing to the
Director or designee, and must clearly state the specific
Section(s) of the Ordinance from which a variance is requested and
why.
7 .2 . 15 EXPERIMENTAL BMPs
Experimental best management practices are defined as BMPs which
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MASON COUNTY STORKWATER MANAGEMENT ORDINANCE - ATTACHMENT A
have not been tested and evaluated by the Department of Ecology in
collaboration with local governments and technical experts. Some
so-called Experimental BMPs will likely be minor variations on an
existing theme. In that case, Ecology would review and approve or
disapprove the BMP in as timely a manner as possible. Where new
designs are developed (examples of experimental BMPs may be found
in Section 1-2 . 17 . 2 of the PSWQA Manual) , the review will be
extended through the use of a standing committee of technical
experts. These persons will review and comment on the practice,
and Ecology will then determine whether or not these BMPs should be
approved and/or added to the manual .
7.2. 15. 1 Approval of Experimental BMPs
Approval to use an Experimental BMP may be granted subject to
initial approval by the Department of Ecology and the local
government. If such Experimental BMPs prove useful they may be
incorporated into later editions of the Manual following appraisal
of the results and appropriate technical review conducted by
Ecology in collaboration with local governments and other
interested parties. Approval to use an Experimental BMP will only
be granted when a suitable contingency plan using approved BMPs has
been provided by the applicant to be used in the event that the
Experimental BMP does applicant
perform adequately.
In addition, several Experimental BMPs have been included in the
Manual. People may wish to use these BMPs on a trial basis,
subject to approval by the local government and provision of a
contingency plan. In any event, use of Experimental BMPs is
encouraged whenever applied research is being undertaken so that
more information is made available to facilitate judgement on their
applicability and possible adoption as an approved BMP.
SECTION 8: ADMINISTRATION
8.1 Director
The Mason County Public Works Director or a designee shall
administer this Ordinance and shall be referred to as the Director.
The Director shall have the authority to develop and implement
administrative procedures to administer and enforce this Ordinance.
8.2 Review and approval
The Director may approve, conditionally approve or deny an
application for activities regulated by this Ordinance. Copies of
Sections 8 , 91 10, & 11 shall be given to all applicants.
8.3 Enforcement authority
The Director shall enforce this Ordinance.
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
8.4 Inspection
All activities regulated by this Ordinance, except those exempt in
Section 5.2 , are subject to inspection by the Director. The
Director may inspect projects at various stages of the work
requiring approval to determine that adequate control is being
exercised. Stages of work subject to inspection include, but are
not limited to, preconstruction; installation of BMPs; land
disturbing activities; installation of utilities, landscaping,
retaining walls and completion of project. As required by the
Director, inspections and/or testing shall be performed by the
owner or authorized agent.
SECTION 9: ENFORCEMENT
9. 1 General
Enforcement action shall be in accordance with this Ordinance
whenever a person has violated any provision of this Ordinance. The
choice of enforcement action and the severity of any penalty shall
be based on the nature of the violation, the damage or risk to the
public or to public resources, and/or the degree of bad faith of
the person subject to the enforcement action.
9.2 Stop Work order
The Director shall have the authority to serve a person a stop work
order if an action is being undertaken in violation of this
Ordinance.
A. Content of Order. The order shall contain:
(1) A description of the specific nature, extent, and time of
violation and the damage or potential damage; and
(2) A notice that the violation or the potential violation
cease and desist, and, in appropriate cases, the specific
corrective action to be taken within a given time. A
civil penalty under Section 9 . 3 below may be issued with
the order.
B. Notice. A stop work order shall be imposed by a notice in
writing, either by certified mail with return receipt
requested, or by personal service, to the person incurring the
same.
C. Effective Date. The stop work order issued under this Section
shall become effective immediately upon receipt by the person
to whom the order is directed.
D. Compliance. Failure to comply with the terms of a stop work
order shall result in enforcement actions including, but not
limited to, the issuance of a civil penalty.
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
® Civil Penalty
A person who fails to comply with the requirements of this
Ordinance, who fails to conform to the terms of an approval order
issued, who undertakes new development without first obtaining
County approval, or who fails to comply with a stop work order
issued under these regulations shall be deemed to be in violation
of this ordinance and subject to a civil penalty.
A• Amount of Penalty. The penalty shall not be less than
or exceed $ 100. 00 for each site per day. Each day of
continued violation or repeated violation shall constitute a
separate violation.
B. Aiding and Abetting. Any person who, through an act of
commission or omission, aids or abets in the violation shall
be considered to have committed a violation for the purposes
of the civil penalty.
C. Notice of Penalty. A civil penalty 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 from the County. The notice shall describe
the violation, approximate the date(s) of violation, and shall
order the acts constituting the violation to cease and desist,
and, in appropriate cases, require necessary corrective action
within a specified time.
D. Application for Remission or Mitigation. Any person incurring
a penalty may apply in writing within 10 business days of
receipt of the penalty to the County Public Works Director for
remission or mitigation of such penalty. Upon receipt of the
application, the County Public Works Director may remit or
mitigate the penalty only upon a demonstration of
extraordinary circumstances, such as the-presence of
information or factors not considered in setting the original
penalty. The decision may be appealed to the Board of County
Commissioners within 10 business days of the decision.
E. Appeal Of Civil Penalty. Persons incurring a penalty imposed
by the Director may appeal in writing within 10 business
days of the receipt of the penalty to the Board of Mason
County Commissioners. The Commissioner' s decision may be
appealed to the Mason County Superior Court within 10
business days of the decision.
9. 3. 1 Penalties due
Penalties imposed under this Section shall become due and payable
30 days after receiving it unless application for remission or
mitigation is made or an appeal is filed. Whenever an application
for remission or mitigation is made, penalties shall become due and
payable 30 days after the receipt of the decision regarding the
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE - ATTACHMENT A
remission or mitigation. Whenever an appeal of a penalty is filed,
the penalty shall become due and payable after all review
proceedings and a final decision has been issued confirming all or
part of the penalty. If the amount of a penalty owed the County is
not paid within the time specified, the County shall take actions
necessary to recover such penalty.
9.3.2 Penalty recovered
Penalties recovered shall be paid to a fund established by the
Board of Mason County Commissioners, dedicated to enforcement,
education, and/or enhancement of the stormwater management program.
SECTION 10: EXCEPTIONS
10. 1 Right of appeal
All actions of the Director shall be final and conclusive, unless
within 10 business days of the date of the Director's action,
the original applicant or an adverse party gives written notice of
appeal to the Board of Mason County Commissioners for review of the
actions.
10.2 Findings of fact
Exceptions to Minimum Requirements 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.
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MASON COUNTY STORMWATER MANAGEMENT ORDINANCE ® ATTACHMENT A
0®3 Prior approval
Any exception shall be approved prior to permit approval and
construction.
10.4 Duration of exception
Exceptions grantedshall be valid for 2 years, unless granted for a
shorter period.
10.5 Board of appeals
After a public hearing, the Board of Mason County Commissioners may
grant an exception from the requirements of this Ordinance. In
granting any exception, the Board of Mason County Commissioners may
prescribe conditions that are deemed necessary or desirable for the
public interest.
SECTION 11: SEVERABILITY
If any provision of this Ordinance or its application to any
person, entity, or circumstance is held invalid, the remainder of
this Ordinance or the application of the provision to other
persons, entities, or circumstances shall not be affected.
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