HomeMy WebLinkAboutBLD2006-00519 Stormwater Management Plan i •
PERMIT # BID
06 - 0519
JEFFERSON COUNTY DCD
STORMWATER SITE PLAN
CURTIS STACEY/TANYA ROYER
Report Prepared for:
Curtis Stacey
481 Snow Creek Road --
Quilcene, WA 98376
September 1, 2006
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Report By: APPROVED
Tillman Engineering STORMWATER PLAN
P.O. Box 1375
Port Hadlock, Washington 98339
(360) 379-9661 OCT 1 2 2006
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Table of Contents
September 1, 2006 1
I. PROJECT OVERVIEW 4
II. PLOT PLAN- (See Attachment 'A', Site Plan) 4
III. CONDITIONS SUMMARY 4
IV. OFF SITE ANALYSIS ' 4
V. ANALYSIS AND DESIGN OF STORMWATER FACILITIES 4
VI. SPECIAL REPORTS AND STUDIES 5
VIL BASIN AND COMMUNITY PLANNING AREAS 5
VIII. OTHER PERMITS 5
2.5.1 Minimum Requirement#1: Preparation of Storm water Site Plans 5
2.5.2 Minimum Requirement#2: Construction Storm water Pollution Prevention
(SWPP) 5
2.5.3 Minimum Requirement#3:Source Control of Pollution 8
2.5.4 Minimum Requirement#4:Preservation of Natural Drainage Systems and
Outfalls 8
2.5.5 Minimum Requirement#5: On-site Storm water Management 8
2.5.6 Minimum Requirement#6: Runoff Treatment 9
2.5.7 Minimum Requirement#7: Flow Control 9
2.5.8 Minimum Requirement#8: Wetlands Protection 10
2.5.9 Minimum Requirement#9: Basin/Watershed Planning 10
2.5.10 Minimum Requirement#10: Operation and Maintenance 11
HI. CONDITIONS SUMMARY 4
IV. OFF SITE ANALYSIS 4
V. ANALYSIS AND DESIGN OF STORMWATER FACILITIES 4
VI. SPECIAL REPORTS AND STUDIES 5
VII. BASIN AND COMMUNITY PLANNING AREAS 5
VIII. OTHER PERMITS 5
2.5.1 Minimum Requirement#1: Preparation of Stormwater Site Plans 5
2.5.2 Minimum Requirement#2: Construction Storm water Pollution Prevention
(SWPP) 5
2.5.3 Minimum Requirement#3: Source Control of Pollution 8
Curtis Stacey Stormwater Site Plan
481 Snow Creek Road
Quilcene,WA 98376
September 1, 2006
Page 2
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2.5.4 Minimum Requirement #4: Preservation of Natural Drainage Systems and
Outfalls 8
2.5.5 Minimum Requirement#5: On-site Stormwater Management 8
2.5.6 Minimum Requirement#6: Runoff Treatment 9
2.5.7 Minimum Requirement#7: Flow Control 9
2.5.8 Minimum Requirement#8: Wetlands Protection 10
2.5.9 Minimum Requirement#9: Basin/Watershed Planning 10
2.5.10 Minimum Requirement#10: Operation and Maintenance 11
ATTACHMENT I S.C.S. MAP OF THE PROJECT LOCATION
ATTACHMENT II SITE PLANS
I;
Curtis Stacey Stormwater Site Plan
481 Snow Creek Road
Quilcene,WA 98376
September 1,2006
Page 3
I. PROJECT OVERVIEW
The applicant is proposing the construction of a single-family residence on an 8.76 acre Lake Leland
waterfront parcel in Quilcene. The project applicant is Curtis Stacey, who currently resides on the
property.
II. PLOT PLAN - (See Attachment 'A', Site Plan)
III. CONDITIONS SUMMARY
The subject property contains previous development including driveways, clearings, earthwork cuts and
fills, a double-wide mobile home currently used as Stacey's residence.
Most of the subject property is easterly sloping at mild grades of approximately 10-15 percent. The site is
within the Lake Leland Valley, with the namesake lake bordering the easterly side of the site.
A portion of the site is bare earth, including an area where recent earthwork activities have taken place in
anticipation of placing the homesite. Most of the site is vegetated with native trees and vegetation,
including along the shore of Lake Leland itself.
Surface Soil Conditions
The native site soils are mapped in the Soil Survey of Jefferson County Area, Washington,August 1975,by
the Soil Conservation Service (SCS). The dominant soil type mapped in the project vicinity is Alderwood
gravelly loamy sand(AIC) and(AID). See the attached pages from the soil survey for specific soil profile
descriptions.
Approximately twelve soil log holes have been evaluated on the site by this office in preparation of the
septic system design for this project. These soil logs verified presence of relatively shallow native soils
underlain by relatively impervious subsoil units.
Storm Drainage
The site storm drainage is overland flow and subsurface flow in the shallow site soils. It is believed that
most or all of the stormwater runoff from this site eventually flows into Lake Leland.
IV. OFF SITE ANALYSIS
As with most projects, there is the potential for off-site transport of eroded soils. Implementation of
erosion controls and timing of earthmoving activities to coincide with the summer dry season will reduce
the risk of sedimentation to Lake Leland.
There may be some contribution to site stormwater from adjacent properties to the west due the easterly
sloping landform. It is important to maintain to the extent practical stormwater flows to the lake.
V. ANALYSIS AND DESIGN OF STORMWATER FACILITIES
Stormwater runoff from the proposed residence will be collected via gutters and downspouts on the
building and will be dispersed onto the surface of the ground downslope of the homesite. The homesite is
located approximately 170' from the shoreline and runoff collected from the home's gutters will be allowed
to enter the natural site drainage.
Curtis Stacey Stormwater Site Plan
481 Snow Creek Road
Quilcene,WA 98376
September 1, 2006
Page 4
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Stormwater runoff from the new parking area and the existing developed areas such as the driveway will
remain uncontrolled, flowing overland to the east. Most areas of the site will remain in an undisturbed
condition and will flow runoff as they have historically. Runoff from the parking areas will essentially
route across lawn areas, which act as a filter strip. Prudent actions and maintenance of these facilities will
ensure long term water quality for stormwater runoff.
VI. SPECIAL REPORTS AND STUDIES
None.
VII. BASIN AND COMMUNITY PLANNING AREAS
There is no known basin plan for this locale.
VIII. OTHER PERMITS
The proponent has applied for an on-site sewage permit,a reserve area designation permit for the existing
residence, and a building permit and demolition permit for on site structures proposed to be replaced with
smaller buildings.
2.5.1 Minimum Requirement#1: Preparation of Stormwater Site Plans
All projects meeting the thresholds in Section 2.4 shall prepare a Stormwater Site
Plan for local government review. Stormwater Site Plans shall be prepared in
accordance with Chapter 3 of this volume.
This project proposes the current grading less than 100 cubic yards of material and approximately 9,000 sf
of land disturbing activity to excavate for the homesite and septic system. The proponent also proposes
construction of an approximate 3500 SF residence with approximately 1000 estimated SF of related
parking area and driveway improvements. The driveways are already in existence. Minimum requirements
1 through 10 of the current Stormwater Manual for Western Washington will apply for all new impervious
surfaces and converted pervious surfaces.
2.5.2 Minimum Requirement #2: Construction Stormwater Pollution Prevention
(SWPP)
Element 1: Mark Clearing Limits
The project requires no additional clearing. A silt fence will be placed at the easterly edge of the homesite
clearing to act as a sediment barrier to protect the lake during fall and winter rains.
Element 2: Establish Construction Access
Construction access for the project site is existing at the present time in the form of a developed driveway
from Snow Creek Road. No additional work is required.
Snow Creek Road will be checked at the end of each work day and cleaned, if required. Sediment from
cleaning activities will be disposed of in an appropriate manner.
Curtis Stacey Stormwater Site Plan
481 Snow Creek Road
Quilcene,WA 98376
September 1, 2006
Page 5
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Element 3: Control Flow Rates
No offsite flows are anticipated during construction. Flow control is not required as Lake Leland is a
receiving water body. All stormwater run-off will be dispersed and/or infiltrated on-site, and flow
attenuation will result. The lake will be protected from sediment during construction by the
aforementioned practices.
Element 4: Install Sediment Controls -
The duff layer,native topsoil,and natural vegetation will be retained in an undisturbed state to the
maximum extent practicable.
Silt fence will be placed downslope of earth disturbing activity,as required, to prevent sediment from
entering undisturbed areas. Other sediment control BMPs will be utilized, if required.
Element 5: Stabilize Soils
All exposed and unworked soils not targeted additional site grading shall be stabilized by application of
BMP C120,Temporary and Permanent Seeding,and BMP C121,Mulching,to protect the soil from the
erosive forces of raindrop impact and flowing water,and wind erosion.
From October 1 through April 30, no soils shall remain exposed and unworked for more than 2 days. From
May 1 to September 30, no soils shall remain exposed and unworked for more than 7 days.This condition
applies to all soils on site, whether at final grade or not. These time limits may be adjusted by the local
permitting authority if it can be shown that the average time between storm events justifies a different
standard.
Work on this construction site will not exceed the capability of the contractor to re-stabilize the disturbed
soils, meeting the timing conditions listed above.
Element 6: Protect Slopes
The existing site slopes will be suitably protected by application of measures as discussed in Element 5
above. No unstable slopes are located onsite and there are no mass stability concerns.
Element 7: Protect Drain Inlets
There are no storm drain inlets with this project.
Element 8: Stabilize Channels and Outlets
There are no channels or outlets proposed with this project.
Element 9: Control Pollutants
All pollutants, including waste materials and demolition debris, that occur on-site during construction, will
be handled and disposed of in a manner that does not cause contamination of stormwater.
Cover,containment, and protection from vandalism will be provided for all chemicals, liquid products,
petroleum products, and non-inert wastes present on the site(see Chapter 173-304 WAC for the definition
of inert waste).
Curtis Stacey Stormwater Site Plan
481 Snow Creek Road
Quilcene, WA 98376
September 1, 2006
Page 6
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Maintenance and repair of heavy equipment and vehicles involving oil changes, hydraulic system drain
down, solvent and de-greasing cleaning operations, fuel tank drain down and removal,and other activities
which may result in discharge or spillage of pollutants to the ground or into stormwater runoff will be
conducted using spill prevention measures, such as drip pans.
Contaminated surfaces will be cleaned immediately following any discharge or spill incident. Emergency
repairs may be performed on-site using temporary plastic placed beneath and, if raining, over the vehicle.
Wheel wash, or tire bath wastewater, will be discharged to a separate on-site treatment system or to a '
sanitary sewer.
Application of agricultural chemicals, including fertilizers and pesticides, will be conducted in a manner
and at application rates that will not result in loss of chemical to stormwater runoff. Manufacturers'
recommendations will be followed for application rates and procedures.
Management of pH-modifying sources will prevent contamination of runoff and stormwater collected on
the site. These sources include,but are not limited to,bulk cement, cement kiln dust, fly ash,new concrete
washing and curing waters, waste streams generated from concrete grinding and sawing,exposed aggregate
processes, and concrete pumping and mixer washout waters.
Element 10: Control De-Watering
Highly turbid or otherwise contaminated dewatering water,such as from construction equipment operation,
clamshell digging, concrete tremie pour,or work inside a cofferdam, will be handled separately from
stormwater at the site.
Other disposal options, may include: 1) infiltration, 2)transport off-site in vehicle, such as a vacuum flush
truck, for legal disposal in a manner that does not pollute state waters, 3)on-site treatment using chemical
treatment or other suitable treatment technologies.
Dewatering is not anticipated for this project.
Element 11: Maintain BMPs
All temporary and permanent erosion and sediment control BMPs will be maintained and repaired as
needed to assure continued performance of their intended function. All maintenance and repair will be
conducted in accordance with BMPs.
Sediment control BMPs will be inspected weekly or after a runoff-producing storm event during the dry
season and daily during the wet season.
All temporary erosion and sediment control BMPs will be removed within 30 days after final site
stabilization is achieved or after the temporary BMPs are no longer needed.
Trapped sediment will be removed or stabilized on site.
Disturbed soil areas resulting from removal of BMPs or vegetation will be permanently stabilized.
Element 12: Manage The Project
As stated in Element 5,work on this linear construction site will not exceed the capability of the contractor
to re-stabilize the disturbed soils, meeting the appropriate timing conditions.
Curtis Stacey Stormwater Site Plan
481 Snow Creek Road
Quilcene,WA 98376
September 1, 2006
Page 7
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The following activities are exempt from the seasonal clearing and grading limitations:
1. Routine maintenance and necessary repair of erosion and sediment control BMPs;
2. Routine maintenance of public facilities or existing utility structures that do not expose the soil or result
in the removal of the vegetative cover to soil;and
3. Activities where there is one hundred percent infiltration of surface water runoff within the site in
approved and installed erosion and sediment control facilities.
Inspection and Monitoring-All BMPs shall be inspected, maintained, and repaired as needed to assure
continued performance of their intended function.
Whenever inspection and/or monitoring reveals that the BMPs identified in the Construction SWPPP are
inadequate, due to the actual discharge of or potential to discharge a significant amount of any pollutant,
the SWPPP shall be modified, as appropriate, in a timely manner.
Maintenance of the Construction SWPPP-The Construction SWPPP shall be retained on-site or within
reasonable access to the site.The Construction SWPPP shall be modified whenever there is a significant
change in the design,construction, operation, or maintenance of any BMP.
2.5.3 Minimum Requirement #3: Source Control of Pollution
All known, available and reasonable source control BMPs shall be applied to all
projects. Source control BMPs shall be selected, designed, and maintained
according to this manual.
The contractor will utilize appropriate BMP's should the need arise for preventing stormwater from coming
into contact with pollutants.
2.5.4 Minimum Requirement #4: Preservation of Natural Drainage Systems and
Outfalls
Natural drainage patterns shall be maintained, and discharges from the project site
shall occur at the natural location, to the maximum extent practicable. The manner
by which runoff is discharged from the project site must not cause a significant
adverse impact to downstream receiving waters and downgradient properties. All
outfalls require energy dissipation.
This project proposes to maintain the natural drainage system to the maximum extent practical. The outlet
of site-generated stormwaters is in Lake Leland, at the eastern edge of the proponent's property. All
undisturbed natural drainage patterns within the project limits will be preserved and maintained in their
natural state.
2.5.5 Minimum Requirement#5: On-site Stormwater Management
Projects shall employ On-site Stormwater Management BMPs to infiltrate, disperse,
and retain stormwater runoff onsite to the maximum extent feasible without causing
flooding or erosion impacts. Roof Downspout Control BMPs, functionally
equivalent to those described in Chapter 3 of Volume III, and Dispersion and Soil
Curtis Stacey Stormwater Site Plan
481 Snow Creek Road
Quilcene, WA 98376
September 1, 2006
Page 8
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Quality BMPs, functionally equivalent to those in Chapter 5 of Volume V, shall be
required to reduce the hydrologic disruption of developed sites.
This section seeks to minimize impacts to downslope neighbors. In this case, there are none as the site
terminates at the receiving water body. Stormwater runoff from the site will be dispersed onto grass lawn
and into native vegetation over 150' from the shoreline. The location of the homesite will serve to
maximize infiltration back to the site soils and slow conduction to the lake to the extent possible.
Application of BMP C120,Temporary and Permanent Seeding,and BMP C121, Mulching,will minimize
any potential for erosion. '
2.5.6 Minimum Requirement #6: Runoff Treatment
Thresholds
The following require construction of stormwater treatment facilities
❑ Projects in which the total of effective, pollution-generating impervious surface
(PGIS) is 5,000 square feet or more in a threshold discharge area of the project, or
❑ Projects in which the total of pollution-generating pervious surfaces (PGPS) is
three-quarters (3/4) of an acre or more in a threshold discharge area, and from
which there is a surface discharge in a natural or man-made conveyance system
from the site.
It is unclear if this project meets this threshold. However,the driveway has existed for a long period of
time preceding this project report,and directs runoff into the grassed and native vegetation areas alongside
of the road. The water quality of this project would not be improved with additional stormwater treatment
facilities.
2.5.7 Minimum Requirement#7: Flow Control
Applicability
Projects must provide flow control to reduce the impacts of increased stormwater
runoff from new impervious surfaces and land cover conversions. The requirement
below applies to projects that discharge stormwater directly, or indirectly through a
conveyance system, into a fresh water- except for:
discharges into the Columbia River, Lakes Sammamish, Silver (Cowlitz Co.), Union
(King Co.), Washington, and Whatcom; discharges into a wetland; (See Minimum
Requirement#8 for flow control requirements applicable to discharges to wetlands)
Any exempted areas shall meet the following requirements:
❑ The area must be drained by a conveyance system that is comprised entirely of
manmade conveyance elements (e.g., pipes, ditches, outfall protection, etc.) and
extends to the ordinary high water line of the receiving water; and
Curtis Stacey Stormwater Site Plan
481 Snow Creek Road
Quilcene,WA 98376
September 1, 2006
Page 9
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❑ Any erodible elements of the manmade conveyance system for the area must be
adequately stabilized to prevent erosion; and
El Surface water from the area must not be diverted from or increased to an existing
wetland, stream, or near-shore habitat sufficient to cause a significant adverse
impact.
Local governments may petition Ecology to exempt projects in additional areas. A'
petition must justify the proposed exemption based upon a hydrologic analysis that
demonstrates that the potential stormwater runoff from the exempted area will not
significantly increase the erosion forces on the stream channel nor have near field
impacts.
All post development stormwater run-off generated by this project will be returned to the natural Lake
Leland hydrology.
2.5.8 Minimum Requirement#8: Wetlands Protection
Applicability
The requirements below apply only to projects whose stormwater discharges into a
wetland, either directly or indirectly through a conveyance system. These
requirements must be met in addition to meeting Minimum Requirement#6, Runoff
Treatment.
Thresholds
The thresholds identified in Minimum Requirement #6 — Runoff
Treatment, and Minimum Requirement #7— Flow Control shall also be applied for
discharges to wetlands.
Standard Requirement
Discharges to wetlands shall maintain the hydrologic conditions, hydrophytic
vegetation, and substrate characteristics necessary to support existing and
designated uses. A wetland can be considered for hydrologic modification and/or
stormwater treatment in accordance with Guide Sheet 1B in Appendix I-D of the
Stormwater Manual.
The plan proposes restoration, to the extent practicable,of the hydrologic conditions and preserves the
native lakeshore vegetation.
2.5.9 Minimum Requirement #9: Basin/Watershed Planning
Projects may be subject to equivalent or more stringent minimum requirements for
erosion control, source control, treatment, and operation and maintenance, and
Curtis Stacey Stormwater Site Plan
481 Snow Creek Road
Quilcene, WA 98376
September 1, 2006
Page 10
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alternative requirements for flow control and q wetlands hydrologic control as
identified in Basin/Watershed Plans. Basin/Watershed plans shall evaluate and
include, as necessary, retrofitting urban stormwater BMPs into existing
development and/or redevelopment in order to achieve watershed-wide pollutant
reduction and flow control goals that are consistent with requirements of the federal
Clean Water Act.
Standards developed from basin plans shall not modify any of the above minimum
requirements until the basin plan is formally adopted and implemented by the local
governments within the basin, and approved or concurred with by Ecology.
There are no adopted basin plans applicable to this project.
2.5.10 Minimum Requirement#10: Operation and Maintenance
An operation and maintenance manual that is consistent with the provisions in
Volume V of the Stormwater Manual shall be provided for all proposed stormwater
facilities and BMPs, and the party (or parties) responsible for maintenance and
operation shall be identified. At private facilities, a copy of the manual shall be
retained onsite or within reasonable access to the site, and shall be transferred with
property to the new owner. For public facilities, a copy of the manual shall be
retained in the appropriate department. A log of maintenance activity that indicates
what actions were taken shall kept and be available for inspection by the local
government.
An operation and maintenance manual has been developed for the stormwater facilities and BMP's related
to this project and a copy will be given to the owner for their reference and implementation and to be kept
on site. A copy is attached to this stormwater report.
Curtis Stacey Stormwater Site Plan
481 Snow Creek Road
Quilcene, WA 98376
September 1, 2006
Page 11