HomeMy WebLinkAboutMLA18-00043 Stormwater PlanON c
' ° JEFFERSON COUNTY
DEPARTMENT OF COMMUNITY DEVELOPMENT
621 Sheridan Street • Port Townsend • Washington 98368
R. CO 360/3794450 • 360/379-4451 Fax
dNG http://www co.jefferson.wa.us/commdevelopment/
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STORMWATER SITE PLAN SUBMITTAL TEMPLATE
MLA # PROJECT/APPLICANT NAME:
Project Overview
1. Describe the proposed developed conditions of the site. Indicate position and relative
size of proposed improvements on the site map.
The proposed developed condition would consists of a new single family residence (2,400 sq. ft.
roof area), with a new gravel driveway (3,170 sq. ft.), garden (1,250 sq. ft.), and onsite septic
system. The SFR will be located in the northwest portion of the property.
Existing Conditions Summary
2. Describe the existing topography. Indicate contours on the site map.
Grades on site are relatively flat (2%-5%). The site slopes gently to the south and east.
Topographic data based on the aerial GIS mapping available from the Jefferson County jMAP —
Parcel Map Viewer.
3. Describe the existing vegetation. Indicate native vegetation areas on the site map.
The site has been previously logged. Vegetation onsite includes grasses, trees, and various
shrubs. The remaining trees are primarily limited to the northeast corner of the site and a couple
of small pockets within the site.
4. Describe the existing soils. Indicate soil type on the site map.
The majority of soils on site are classified by the NRCS Soils Survey as Type CmC, or Clallam
gravelly sandy loam. A typical profile consists of 0 — 3 inches of gravelly sandy loam, 3 — 23
inches of very gravelly sandy loam, 23 — 60 inches of gravelly sandy loam with restrictive layer
at 20 to 40 inches.
5. Describe the existing site hydrology (i.e., drainage; behavior of water on the site—above,
below, and on the ground). Indicate existing stormwater drainage to and from the site on
the site map. Depict separate drainage basins on the site map, if applicable, and indicate
acreage of each.
There are no defined drainage channels onsite. The high point of the site is in the northwest
corner and it is assumed that runoff sheet flows to the south and east. A portion of the runoff
from the site drains to a wetland located in the northeast corner of the site and it is assumed that
the remainder of the stormwater sheet infiltrates or sheet flows off the site along the east property
line. There are no defined offsite drainages that discharge to this property.
6. Describe any excess levels of noise generated by the proposed use or activity:
The proposed project is for residential use and no excess levels of noise are anticipated.
7. Describe significant geographic features and critical areas (i.e., environmentally sensitive
areas such as wetlands, streams, steep slopes, etc.) on the site. Indicate location on the site
map.
A category 3 wetland is located in the northeast corner of the site. A Wetland Delineation and
Rating Report has been prepared by Marine Survey and Assessments and is included with this
submittal.
8. Describe the general vicinity of the site, including adjacent land uses and structures,
utilities, roads, and sensitive/critical areas (streams, wetlands, lakes, steep slopes, etc.).
The address of the lot is 30 Sunshine Drive; the parcel is located in Section 28, Township 30 N,
Range 2 W. Access to the parcel is off of Sunshine Drive from Gardner Beach Road from
Diamond Point Road north of Highway 101. The parcel is zoned RR — 5 Rural Residential.
Adjacent parcels are zoned similarly and have been developed primarily for residential uses.
Power and water utilities are available directly adjacent to the site and will be supplied by
Jefferson County PUD. Eagle Creek is located approximately 200 feet east of the site.
Permanent Stormwater Control Plan
This portion of the Stormwater Site Plan consists of the selection and installation of the
appropriate stormwater control BMPs and facilities to remain in place after construction
of the project is completed.
"Medium" size projects are required to have the totals calculated of all impervious
surfaces, pollution -generating impervious surfaces, and pollution -generating pervious
surfaces to verify that the thresholds for treatment facilities and flow control facilities are
not exceeded.
9. Describe the developed site hydrology, as proposed. Indicate whether stormwater will
be fully dispersed (i.e., per BMP T5.30 in the Manual) or, if not, what types of stormwater
flow control will be utilized for the site or specific threshold discharge areas within the site.
Locate these facilities on the site plan and differentiate proposed facilities from existing
facilities.
Stormwater will be fully dispersed per BMP T5.30 of the Manual. Runoff from the roof will be
conveyed to a dispersion trench and discharged into replanted forested area. The new driveway
west of the residence will sheet flow stormwater into replanted forest area directly adjacent to the
driveway.
10. If the project requires the use of stormwater treatment facilities, describe the types of
stormwater treatment facilities proposed for use on the site. Locate these facilities on the
site plan and differentiate proposed facilities from existing facilities. [This is normally for
"large" projects or projects that involve the potential for dispersion of contaminants.]
Total pollution generating hard surfacing (PGHS) was estimated to be 3,170 square feet, and thus
treatment of stormwater is not required. However, dispersion of stormwater from the pollution
generating surfaces through vegetated areas will provide treatment of that stormwater.
11. Describe the performance goals and standards applicable to the project.
The standards and goals of this project is to fulfill Minimum Requirements 1-5 as listed in the
2014 Stormwater Management Manual for Western Washington (D.O.E.). The project will
employ Full Dispersion to mitigate stormwater quality or quantity impacts from development.
12. Describe the flow control system.
A flow control system is not required or planned as the total hard surfaces on the project is less
than 10,000 square feet. However, on-site stormwater management BMP's will be utilized to
disperse runoff from hard surfaces (see Item 9 above) which will provide some measure of flow
control.
13. Describe the water quality system. None proposed.
14. Describe the conveyance system analysis and design.
Peak flow rates from the roof were calculated using the Rational Method. A 4"0 PVC pipe with
a minimum slope of 1% has sufficient capacity to convey the 25 -yr peak flow rate from the roof
without pressurized pipe flow.
15. Describe the source of fill material, physical characteristics of fill material, and
deposition of excess material.
Onsite material excavated for installation of the roadway and residence will be disposed of
onsite. The only other fill anticipated on site will be clean granular material for the driveway and
septic system and will be sourced from local pits.
16. Proposed methods of placement and compaction consistent with the applicable
standards in Appendix J and Chapter 33 of the Uniform Building Code.
No structural fill will be required for this project. Driveway gravel will be placed with a dump
truck, spread with backhoe or excavator, and compacted with a vibratory roller. Native onsite
material disposed of onsite will be spread with backhoe or excavator and compacted by
traversing with the equipment placing the material.
17. Describe the proposed surfacing material.
Surfacing onsite will consist of clean crushed gravel for the driveway and parking areas.
18. Describe methods for restoration of the site.
Soils disturbed during the construction of the residence and associated utilities will be amended
as outlined in BMP T5.13 and seeded and mulched as outlined in BMP C120, and BMP C121.
The areas which will be utilized for dispersion of stormwater and the remainder of the site that
was previously logged will be replanted with native trees (Douglas Fir, Western Red Cedar,
Western Hemlock, etc.).
19. An Operation and Maintenance Manual is required for each flow control and
treatment facility. [This is normally required for "large" projects only and only those for
which facilities are required to control flow or treat runoff.] If included, list the Manuals
here.
Operation and maintenance manual is not required for this project as there are no flow control or
treatment facilities planned.
20. List here and include any special reports or studies conducted to prepare the
Stormwater Site Plan.
A Wetland Delineation and Rating Report has been prepared to provide information on an
existing wetland in the northeast corner of the project.
21. List other necessary permits and approvals as required by other regulatory agencies.
If those permits or approvals include conditions that affect the drainage plan or contain
more restrictive drainage -related requirements, describe those conditions or restrictions
here.
Septic Permit: Jefferson County
Building Permit: Jefferson County
CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN
(SWPPP)
The Construction SWPPP addresses sediment and erosion control during construction. The
BMPs indicated by the applicant in the template that follows must be installed on the ground
during all construction phases of the project. The proponent is responsible for
preventing sediment and erosion impacts to environmentally sensitive areas and off-site areas.
Consult the Construction Stormwater Pollution Prevention (SWPP) Best Management Practices
(BMPs) Packet for guidance, particularly with rural residential
development.
SECTION I - CONSTRUCTION SWPPP NARRATIVE
1. Construction Stormwater Pollution Plan Elements. Describe how each of the Construction
SWPPP elements has been or will be addressed. Identify the type and location of BMPs used to
satisfy the required element. If an element is not applicable
to the proposal, justify in writing. Descriptions of the 12 Elements are found at section 2.5.2 of
the Manual (beginning on page 2-15).
12 Required Elements — Construction SWPPP
1. Mark Clearing Limits.
The project area has been cleared previously. Silt fence will be installed east of the proposed
drain field area to restrict access to the wetland buffer.
2. Establish Construction Access.
Access to the site will be stabilized through early installation of the gravel driveway. The
driveway will be installed prior to septic installation or grading for the proposed residence.
3. Control Flow Rates.
Due to the size and scope of construction no flow control structures are proposed.
4. Install Sediment Controls.
Silt fence (per BMP C233) will be installed along the east edge of Sunshine Drive, west of the
proposed SFR construction site, and east and of the proposed septic system drainfield.
5. Stabilize Soils.
Disturbed soils will be amended as outlined in BMP T5.13 and seeded and mulched as detailed
in BMP C120 and BMP C121.
6. Protect Slopes.
Existing slopes will remain vegetated and in a natural state. New slopes will not exceed 3:1.
7. Protect Drain Inlets.
None planned. There are no existing catch basins within or adjacent to the subject property. One
catch basin will be installed for the dispersion trench, but it will act as a junction structure and is
not intended to collect surface runoff.
8. Stabilize Channels and Outlets.
No new channels or outlets are proposed with this submittal. No existing channels or outlets
were observed onsite.
9. Control Pollutants.
Concrete handling and concrete washout will comply with BMP C151 and BMP C154,
respectively. No other source pollutants are anticipated onsite.
10. Control De -Watering (the act of pumping groundwater or stormwater away from an
active construction site).
No de -watering is anticipated onsite.
11. Maintain Best Management Practices (BMPs).
BMPs implemented onsite will be inspected every week and within 24 hours of a storm event.
Any and all deficiencies will be addressed promptly (within 24 hours) and returned to proper
working condition as detailed in the SWMMWW.
12. Manage the Project.
The contractor will be responsible for adequately phasing the project to limit erosion and
promote sediment control. The contractor is responsible for inspecting and repairing all BMPs
onsite during construction.
Adjacent Areas.
a. Description of the adjacent areas that may be affected by site disturbance (e.g., streams,
lakes, wetlands, residential areas, roads).
There is a Category 3 Wetland in the northeast corner of the site. Sunshine Drive, a graveled
county road, is located east of the site. Gardner Beach Road, a paved county road, is located
south of the project. Eagle creek is located approximately 200 feet east of the site.
b. Description of the downstream drainage path leading from the site to the receiving body
of water (minimum distance of 400yards).
Stormwater runoff that is not infiltrated onsite flows into the wetland in the northeast corner of
the site or sheet flows off the east property line. Stormwater runoff eventually enters Eagle
Creek approximately 200 feet east of the project after passing through approximately 200 feet of
forested area..
Environmentally Sensitive Areas.
a. Description of environmentally sensitive areas that are on or adjacent to the site.
A category 3 wetland is located in the northeast corner of the site. A Wetland Delineation and
Rating Report has been prepared by Marine Survey and Assessments and is included with this
submittal.
b. Description of special requirements for working in or near environmentally sensitive
areas.
The wetland and associated 110 foot buffer will be protected through the use of a silt fence. No
work is planned within the buffer or wetland.
Erosion Problem Areas. Description of potential erosion problems on site in the context of
the characteristics of the on-site soils (e.g., erodibility, settleability, permeability, depth,
texture, soil structure).
The onsite soils that will be disturbed are primarily Clallam Gravelly Sandy Loam. This soil has
a low susceptibility to water erosion. However, due to the fine particles in the soil structure, it is
difficult to remove sediment from stormwater once it has been suspended. Erosion control
measures will focus on prevention of erosion (limiting exposed soils during wet season,
stabilizing exposed soils with straw or seeding and mulching, etc.) rather than removal of
sediments.
Construction Phasing.
a. Construction sequence:
Construct stabilized entrance and install silt fence
Clear and grub construction site
Install driveway
Excavate building foundation
Install septic system, storm drainage systems and utilities
Seed and mulch disturbed areas,
Construct SFR
Remove silt fence upon confirmation of soil stabilization.
b. Construction phasing (if proposed)
Construction Schedule. Wet season is October 1 through April 30 (page 2-20 of the
Manual).
I. Provide a proposed construction schedule.
Construction schedule contingent on permit timelines and approvals. Construction will begin
approximately 30 days after permit approval. Tentative start date is August 2018.
II. Wet Season Construction Activities.
a. Proposed wet season construction activities:
Placement of single family residence may occur during wet season, all other activities to be
completed during dry season.
b. Proposed wet season construction activities for environmentally sensitive areas.
None planned in environmentally sensitive areas, required buffers will be maintained
Financial/Ownership Responsibilities.
a. Identify the property owner responsible for the initiation of bonds and/or other financial
securities.
Catherine Carmella is the property owner and will be the party responsible for the initiation of
bonds and/or other financial securities.
b. Describe bonds and/or other evidence of financial responsibility for liability associated
with erosion and sedimentation impacts.
The contractor will be responsible for presenting the property owner with evidence of financial
responsibility for liability associated with erosion and sediment impacts during construction.
Upon completion of construction, the property owner will assume responsibility for any
erosion/sediment impacts.
8. Engineering Calculations. Provide Design Calculations on a separate sheet for the
following, if applicable.
a. Sediment Ponds/Traps.
b. Diversions.
c. Waterways.
d. Runoff/Stormwater Detention Calculations
DEPARTMENT OF COMMUNITY DEVELOPMENT
621 Sheridan Street, Port Townsend, %VA 98368
Tel: 360.379.4450 1 Fax: 360.379.4451
Web: wwwxo.1cllerson.wa,Lasler�tiinzutrutvcle�clot�tnenl
E-mail: dccliiuco.ie tTerson.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 Plan, if
required.
PARCEL SIZE (I.E., SITE:.)
Size of parcel 5.17 acres An acre contains 43,560 square feet. Multiply the acreage by this figure.
Size of parcel in square feet 225,205.2 sq/ft
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 on plant species, other than noxious weeds, that are indigenous to the coastal region of
the Pacific Northwest and which reasonably could have been expected to naturally occur on the site. Examples include 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,
excavated, and/or compacted for proposed development
project. Include in this calculation the area to be cleared for:
Construction site for structures 2,400 sq/ft
Drainfield, septic tank, etc. 2,500
Well, utilities, etc. .0
Driveway, parking, roads, etc. 3,170
Lawn, landscaping, etc. 1 ,250
Other compacted surface, etc.
C
Total Land Disturbance 9,320
sq/ft
sq/ft
sq/ft
sq/ft
sq/ft
sq/ft
Answer the following two questions related to
conversion of native vegetation:
Does the project convert 3/ acres or more of
native vegetation to lawn or landscaped areas?
Circle: Yes (No)
Does the project convert 2'/2 acres or more of
native vegetation to pasture?
Circle: Yes
Indicate Total Volumes of Proposed:
Cut 50 Fill 50 (cu/yd)
Impervious surface is a hard surface that either prevents or retards the entry of water into the soil mantle 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.
stormwater talc worksheet — REV 10/20/2014
STORMWATER CALULATIONS — IMPERVIOUS SURFACE
NEW
Structures (all roof area) 2,400 sq/ft
Sidewalks 0 scl/ft
Patios
❑c
Solid Decks 0 sq/ft
(without infiltration below)
Driveway, parking, roads, etc 3,170 sq/ft
Other 0 sq/ft
Total New 5,570 sq/ft
TOTAL NEW + TOTAL EXISTING* 5,570
EXISTING
Structures (all roof area)
Sidewalks
Patios
I
sq/ft
0 sq/ft
0 sq/ft
Solid Decks 0 sq/ft
(without infiltration below)
Driveway, parking, roads, etc 0 sq/ft
Other 0 sq/ft
Total Existing 0 sq/ft
'This amount will be used to check total lot coverage.
The following questions will help determine whether the proposed project is considered development or redevelopment.
DEVELOPMENT v. REDEVELOPMENT
Divide the total existing impervious surface above by the size of the parcel and convert to a percentage: 2.2 %
Does the site have 35% or more of existing impervious surface? Circle: Yes F1 No F
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 Flow Chart to determine the
Minimum Requirements for stormwater management. DCD staff will help verify the classification of the project and the application
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 of the affected
property.
(LANDOWNER OR AUTHORIZED REPRESENTATIVE SIGNATURE)
(DATE)
FOR OFFICE USE ONLY
SMALL MEDtLIM LARGE REDEVELOPMENT Stormwater Site Plan: Yes No
stormwater calc worksheet — REV. 10/20/2014 2