HomeMy WebLinkAboutApp C.1 stormwater calc worksheet-writablestormwater calc worksheet – REV. 10/20/2014 1
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
MLA # 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 required 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 Pla n, 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 li mited to clearing, grading, filling,
excavation, and compaction associated with stabilization of structures and road construction.
Native vegetation is vegetation comprised on plant species, other than noxious weeds, that are indigenous to the coastal reg ion of
the Pacific Northwest and 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.
Impervious surface is a hard surface that either prevents or retards the entry of water into the soil mantle as under natura l
conditions prior to development. A hard surface area which causes water to run off the surface in greater quantities or at a n
increased rate of flow from the flow present under natural conditions prior to development. Common impervious surfaces inclu de,
but are not limited to roof tops, walkways, patios, driveways, parking lots or storage areas, concrete or asphalt paving, gra vel roads,
packed earthen materials, and oiled, macadam or other surfaces which similarly impede the natural infiltration of stor mwater.
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:
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
stormwater calc worksheet – REV. 10/20/2014 2
The following questions will help determine whether the proposed project is considered development or redevelopment.
FURTHER INSTRUCTIONS: If the answer is yes, the proposal is considered redevelopment and the attached Figure 2 should be used
to determine the applicable Minimum Requirements. If the answer is no, the proposal is considered new development and the
attached Figure 1 should be used. At this juncture, the applicant should refer to the applicable Flo w Chart to determine the
Minimum Requirements for stormwater management. DCD staff will help verify the classification of the project and the applica tion
requirements.
For proponents of “small” projects who must comply only with Minimum Requirement #2 —Construction Stormwater Pollution
Prevention—an additional submittal is not required. 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 (SWPP) Best Management Practices (BMPs) Packet . Proponents of “medium”
projects—those that must meet only Minimum Requirements #1 through #5—and for “large” projects—those that must meet all 10
Minimum Requirements—are required to submit a Stormwater Site Plan. DCD has prepared a submittal template of a Stormwater
Site Plan, principally for rural residential projects. Complete the template in the Stormwater Site Plan Instructions and Submittal
Template or prepare a Stormwater Site Plan using the step-by-step guidance in the Stormwater Management Manual.
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 o f the affected
property.
________________________________________ ________________________
(LANDOWNER OR AUTHORIZED REPRESENTATIVE SIGNATURE) (DATE)
FOR OFFICE USE ONLY
SMALL_____ MEDIUM_____ LARGE______ REDEVELOPMENT_____ Stormwater Site Plan: Yes_____ No______
STORMWATER CALULATIONS – IMPERVIOUS SURFACE
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 of existing impervious surface? Circle: Yes No