HomeMy WebLinkAboutBLD2021-00363-05- Stormwater or Approved 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
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
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the digital form
Jun 14 2021
stormwater calc worksheet QR code REV. 5/31/2019 page 2 of 2
~ Applicants for small 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 up the
Construction Stormwater Pollution Prevention (SWPPP) Best Management Practices (BMPs) Fact Sheet .
~ Applicants for medium 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 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
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