HomeMy WebLinkAboutBLD2021-00602 - 05 Stormwaterstormwater calc worksheet QR code – REV. 5/31/2019 page 1 of 2
DEPARTMENT OF COMMUNITY DEVELOPMENT
621 Sheridan Street, Port Townsend, WA 98368
Tel: 360.379.4450 | Fax: 360.379.4451
Web: www.co.jefferson.wa.us/communitydevelopment
E-mail: dcd@co.jefferson.wa.us
STORMWATER CALCULATION WORKSHEET
PARCEL # PROJECT/APPLICANT NAME:
DETERMINING STORMWATER MANAGEMENT REQUIREMENTS: This stormwater calculation worksheet should be completed first to
classify the proposal as “small,” “medium,” or “large.” The size determines whether a Stormwater Site Plan is re quired in
conjunction with a stand-alone stormwater management permit application, building permit application, or other land use approval
application that involves stormwater review. The basic information will also be helpful for completing a Stormwater Site Plan, if
required.
Land-disturbing activity is any activity that results in movement of earth, or a change in the existing soil cover (both vegetative and
non-vegetative) and/or the existing soil topography. Land disturbing activities include, but are not limited to clearing, grading, filling,
excavation, and compaction associated with stabilization of structures and road construction.
Native vegetation is vegetation comprised of plant species, other than noxious weeds, which reasonably could have been expected
to naturally occur on the site. Examples include species such as Douglas fir, western hemlock, western red cedar, alder, big -leaf
maple, and vine maple; shrubs such as willow, elderberry, salmonberry, and salal; herbaceous plants such as sword fern, foam
flower, and fireweed.
LAND DISTURBING ACTIVITY, CONVERSION OF NATIVE VEGETATION, AND VOLUME OF CUT/FILL
Calculate the total area to be cleared, graded, filled, Answer the following two questions related to
excavated, and/or compacted for proposed development conversion of native vegetation:
project. Include in this calculation the area to be cleared for:
Does the project convert ¾ acres or more of
Construction site for structures _________________ sq/ft native vegetation to lawn or landscaped areas?
Drainfield, septic tank, etc. ____________________ sq/ft Circle: Yes No
Well, utilities, etc. ___________________________ sq/ft Does the project convert 2 ½ acres or more of
native vegetation to pasture?
Driveway, parking, roads, etc. ___________________sq/ft
Circle: Yes No
Lawn, landscaping, etc. ______________________ sq/ft
Other compacted surface, etc. _________________ sq/ft Indicate Total Volumes of Proposed:
(Includes BMP T5.13 Fill Volume)
Temporary construction area ______________ sq/ft
Total Land Disturbance ____________________ sq/ft Cut __________ Fill __________ (cu/yd)
PARCEL SIZE (I.E., SITE)
Size of parcel _________ acres An acre contains 43,560 square feet. Multiply the acreage by this figure.
Size of parcel in square feet _________________ sq/ft
Scan the QR
code to access
the digital form
Received by DCD 10/12/2021
937-200-301 Quilcene School District Bus Barn
4.64
202,118
4,880
4,000
29,344
1,908
10,000
50,132 < 100 < 100
stormwater calc worksheet QR code – REV. 5/31/2019 page 2 of 2
~ Applicants for “small” projects must comply only with Minimum Requirement #2—Construction Stormwater Pollution Prevention.
Please submit the Small Project Certification (Worksheet “s). The proponent is responsible for employing the 12 Elements to control
erosion and prevent sediment and other pollutants from leaving the site during the construction phase of the project. Pick u p the
Construction Stormwater Pollution Prevention (SWPPP) Best Management Practices (BMPs) Fact Sheet.
~ Applicants for “medium” projects—those that must meet only Minimum Requirements #1 through #5 must submit Worksheet A1
and B1, a stormwater site plan and a construction stormwater pollution prevention site plan (See Reference A1A and B1A for
guidance).).
~ “Large” projects—those that must meet all 9 Minimum Requirements— must submit Worksheet A1 and B1, a stormwater site plan
and a construction stormwater pollution prevention site plan (See Reference A1A and B1A for guidance). Large projects also may
require engineering. See Worksheet L to determine additional large project requirements.
APPLICANT SIGNATURE By signing the Stormwater Calculation Worksheet, I as the applicant/owner attest that the information provided herein
is true and correct to the best of my knowledge. I also certify that this application is being made with the full knowledge and consent of all owners
of the affected property.
________________________________________ ________________________
(LANDOWNER OR AUTHORIZED REPRESENTATIVE SIGNATURE) (DATE)
STORMWATER CALCULATIONS – IMPERVIOUS SURFACE
Impervious surface is a hard surface that either prevents or slows the entry of water into the soil as under natural
conditions prior to development. 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.
NEW EXISTING
Structures (all roof area) _________________sq/ft Structures (all roof area) _________________sq/ft
Sidewalks _________________sq/ft Sidewalks _________________sq/ft
Patios _________________sq/ft Patios _________________sq/ft
Solid Decks _________________sq/ft Solid Decks _________________sq/ft
(without infiltration below) (without infiltration below)
Driveway, parking, roads, etc _______________sq/ft Driveway, parking, roads, etc _______________sq/ft
Other _________________sq/ft Other _________________sq/ft
Total New _________________sq/ft Total Existing _________________sq/ft
TOTAL NEW + TOTAL EXISTING* _________________sq/ft *This amount will be used to check total lot coverage.
DEVELOPMENT v. REDEVELOPMENT
Divide the total existing
impervious surface above by the
size of the parcel and convert to
a percentage. ____________%
Does the site have > 35% or more
existing impervious surface?
The proposal is considered new development. Answer
questions in Figure 2.4.1 Flow Chart for New
Development to determine project size (next page).
The proposal is considered redevelopment Answer
questions in Figure 2.4.2. Flow Chart for
Redevelopment to determine project size (next page).
yes
no
Received by DCD 10/12/2021
4,880
1,908
29,344
36,132
36,132
Worksheet B1
Construction Protection: Medium and Large Projects(SWPPP: Stormwater Pollution Prevention Plan)
Submit a site plan demonstrating the construction protective measures or best management practices that will
be used for the project during the construction phase.
Refer to REFERENCE B1A for examples of Construction Best Management Practices (BMP’s) that you can use. The
activities that take place during construction are the highest risk for stormwater problems such as erosion and
sediment control (you may need to provide an additional site plan with greater detail for stormwater features. If so,
make sure it is consistent with the primary site plan. Remember that all site plans submitted for the project must
be consistent and accurate).
page 1 of 6
Element 1: Preserve Vegetation / Mark Clearing Limits
The goal of this element is to preserve native vegetation and to clearly show the limits of disturbance.
Choose any of the following that apply:
The site was cleared as part of clearing activity that is subject to an enforcement action and will be re-vegetated.
Restoration may be necessary to comply with Critical Area Regulations or stormwater requirements. Buffer Zones-
BMP C102 may apply if Critical Areas exist on-site and buffer zones shall be protected.
The perimeter of the area to be cleared shall be marked prior to clearing operation with visible flagging, orange
plastic barrier fencing and/or orange silt fencing as shown on the SWPPP site plan. Vehicles will only be allowed
in the areas to be graded, so no compaction of the undeveloped areas will occur. If this option is selected check
the BMPS you will use below:
C101 Preserving Natural
Vegetation
C102 Buffer
Zones
C103 High Visibility
Fence
It is necessary to disturb the entire property during this project due to existing site conditions, property
constraints, and proposed design. I understand that all disturbed land not covered by hard surface at the end of
the project is subject to soil amendment requirements per BMP T5.13 Post-Construction Soil Quality and Depth.
Element 2: Construction Access
The goal of this element is to provide a stabilized construction entrance/exit to prevent or reduce or sediment
track out.
Choose one of the following:
The driveway to the construction area already exists and will be used for construction access. All equipment and
vehicles will be restricted to staying on that existing impervious surface. If sediment is tracked off site, the road-
way will be cleaned thoroughly at the end of each day.
A stabilized construction entrance will be installed prior to any vehicles entering the site, at the location
shown on the SWPPP site plan. If sediment is tracked off site, the roadway will be cleaned thoroughly at the end
of each day. If this option is selected check the BMPS you will use below:
C105 Stabilized
Construction Entrance /
Exit
C106 Wheel
Wash
C107 Construction
Road / Parking Area
Stabilization
Received by DCD 10/12/2021
x
x
x
x
x
x
Worksheet B1
Construction Protection: Medium and Large Projects(SWPPP: Stormwater Pollution Prevention Plan)
Element 3: Control Flow Rates
The goal of this element is to construct retention or detention facilities when necessary to protect properties
and waterways downstream of development sites from erosion and turbid discharges.
This element does not apply to my project because (check any that apply):
page 2 of 6
Site is mildly sloped (<5%),
There are no individually sloped sections greater than 10%,
The bulk of the project is scheduled to occur during dry season (May 1-Sept 30)
Sediment control BMPs shall be placed at the locations shown on the SWPPP Site Plan. If this option is selected
check the BMPS you will use below:
C233 Silt FenceC231 Brush Barrier
C234 Vegetated
Strip
C232 Gravel Filter
Berm
C235 Wattles
Element 4: Sediment Control
The goal of this element is to construct sediment control BMPs that minimize sediment discharges from the site.
Select one of the two statements applicable to the project.
The site has already been stabilized and re-vegetated.
Element 5: Stabilize Soils
• Soil stockpiles will be located within the disturbed area shown on the SWPPP Site Plan.
• Soil excavated for the foundation will be backfilled against the foundation and graded to drain away from the
building.
• No soils shall remain exposed and unworked for more than 7 days from May 1 to September 30 or more than
2 days from October 1 to April 30.
• Once the disturbed landscape areas are graded, the grass areas will be amended.
• All stockpiles will be covered with plastic or burlap if left unworked.
The goal of this element is to stabilize exposed and unworked soils by implementing erosion control BMPs.
Select one of the three statements applicable to the project.
My project will ensure the following:
This element does not apply to my project because:
My project must implement specific BMP’s to ensure compliance. (Check BMP’s you will use on the next page).
Received by DCD 10/12/2021
x
x
x
x x
x
Worksheet B1
Construction Protection: Medium and Large Projects(SWPPP: Stormwater Pollution Prevention Plan)
page 3 of 6
C120 Temporary &
Permanent Seeding
C123 Plastic CoveringC121 Mulching
C124 SoddingC122 Nets & Blankets
C125 Topsoil /
Composting
C131 Gradient
Terraces
C140 Dust Control
C235 Wattles
Element 6: Protect Slopes
The goal of this element is to design and construct cut-and-fill slopes in a manner to minimize erosion.
Select one of the two statements applicable to the project.
No cut slopes over 4 feet high or slopes steeper than 2 feet horizontal to 1 foot vertical, and no fill slopes over
4 feet high will exceed 3 feet horizontal to 1 foot vertical. Therefore, there is no requirement for additional
engineered slope protection.
The above checkbox is not checked. My submittal is designed by a licensed geologist to protect slopes. Based on
the licensed professionals recommendation (please attach their evaluation), the following BMP’s will be used:
C120 Temporary & Permanent
Seeding
C204 Pipe Slope Drains
C205 Subsurface
Drains
C206 Level Spreader
C207 Check Dams
C208 Triangular Silt Dike
(Geotextile-Encased Check Dam)
Catch basins on the site or immediately off site in the right-of-way are shown on the SWPPP Site Plan. Storm drain
inlet protection shall be installed. If this option is selected check the BMPS you will use below:
C220 Storm Drain Inlet Protection
The site has open ditches in the right-of-way or private road right-of-way.
There are no catch basins on or near the site.
Element 7: Protect Permanent Drain Inlets
The goal of this element is to protect storm drain inlets during construction to prevent stormwater runoff from
entering the conveyance system without being filtered or treated.
Select one of the three statements applicable to the project.
Received by DCD 10/12/2021
x
x
x
x
x
x
Worksheet B1
Construction Protection: Medium and Large Projects(SWPPP: Stormwater Pollution Prevention Plan)
A wattle shall be placed at the end of the swale to prevent erosion at the outlet of the swale. If this option is
selected check the BMPS you will use below:
C202 Channel Lining C207 Check Dams C235 WattlesC209 Outlet Protection
page 4 of 6
Element 8: Stabilize Channels and Outlets
The goal of this element is to design, construct, and stabilize on-site conveyance channels to prevent erosion
from entering existing stormwater outfalls and conveyance systems.
Select one of the three statements applicable to the project.
Construction will occur during the dry weather. No storm drainage channels or ditches shall be constructed either
temporary or permanent.
There are no existing or proposed stormwater conveyance channels on the project site.
C151 Concrete Handling C152 Sawcutting and Surfacing
Pollution Prevention
C153 Material Delivery, Storage, and Containment C154 Concrete Washout Area
If one or more of the checkboxes above are unchecked. Any and all pollutants, chemicals, liquid products and other
materials that have the potential to pose a threat to human health or the environment will be covered, contained, and
protected from vandalism. All such products shall be kept under cover in a secure location on-site. Concrete handling
shall follow BMP C151 C154. If this option is selected check the BMPS you will use below:
Element 9: Control Pollutants
This element does not apply to my project because (circle any that apply - If any box is unchecked this element applies.
The goal of this element is to design, install, implement and maintain BMPs to minimize the discharge of
pollutants from material storage areas, fuel handling, equipment cleaning, management of waste materials, etc.
There will be no concrete work,
There will be no sawcutting work,
There will be no hazardous materials on-site,
There will be no fertilizer or pesticide application,
There will be no heavy equipment associated with this project,
There will be no pressure washing, equipment maintenance or dewatering
Received by DCD 10/12/2021
x
x
x
x
x
Worksheet B1
Construction Protection: Medium and Large Projects(SWPPP: Stormwater Pollution Prevention Plan)
C203 Water Bars C236 Vegetated Filtration C206 Level Spreader
Element 10: Control De-watering
No dewatering of the site is anticipated.
Dewatering of the site is anticipated. If this option is selected check the BMPS you
will use below:
page 5 of 6
Select one of the two statements applicable to the project.
The goal of this element is to handle turbid or contaminated water from dewatering (removal of water)
separately from stormwater.
Describe the steps you will take:
Element 12: Manage the Project
The SWPPP will be implemented at all times. If applicable to the project, erosion control BMPs will be
implemented in the following sequence:
1. Mark clearing limits
2. Install stabilized construction entrance
3. Install protection for existing drainage systems and permanent drain inlets
4. Establish staging areas for storage and handling polluted material and BMPs
5. Install sediment control BMPs
6. Grade and install stabilization measures for disturbed areas
7. Maintain BMPs until site stabilization, at which time they may be removed
Element 11: Maintain Best Management Practices
Best Management Practices or BMPs shall be inspected and maintained during construction and removed within
30 days after the County Inspector or determines that the site is stabilized, provided that they may be removed
when they are no longer needed.
The goal of this element is to maintain and repair all temporary and permanent erosion and sediment control
BMPs to assure continued performance.
The goal of this element is to ensure that the owner and those performing the site work comply with the
SWPPP and properly coordinate to ensure that all BMPs are deployed at the proper time to achieve full
compliance with county regulations throughout the project.
Received by DCD 10/12/2021
x
x
Worksheet B1
Construction Protection: Medium and Large Projects(SWPPP: Stormwater Pollution Prevention Plan)
C102 Buffer Zone C103 High Visibility Fence
C233 Silt Fence
C231 Brush Barrier
C234 Vegetated Strip
Applicant or Representative Signature
Element 13: Protect Low Impact Development BMPs
page 6 of 6
The goal of this element is to protect permanent stormwater management BMPs from siltation and compaction
during construction. The permanent stormwater management BMPs used for runoff from roofs and other hard
surfaces include: full dispersion, roof downspout full infiltration or dispersion systems, perforated stubout
connections, rain gardens, bioretention systems, permeable pavement, sheetflow dispersion, and concentrated
flow dispersion.
Methods that will be used to protect permanent stormwater management BMPs include:
Sequencing the construction in a fashion to install these permanent BMPs at the latter part of the
construction grading operations,
Excluding equipment from the BMPs and the associated areas,
Using the erosion and sedimentation control BMPs listed below to protect facilities such as drywells,
raingardens, permeable pavement, or bioretention from accumulating sediment during construction and
before site restoration. If this option is selected check the BMPS you will use below:
Other
Received by DCD 10/12/2021
x
x
x