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Home My WebLink AboutBLD2006-00678 Stormwater Management Plan • • a ' _f STORMWATER POLLUTION PREVENTION PLAN for Westall Property Prepared for James Westall c/o Skookum 385 Benedict St. Port Townsend, WA 98368 September 2006 Prepared by air E N G I N E E R INJ G 2020 ENGINEERING, Inc. 700 Dupont Street PO Box 1621,Bellingham,WA 98227 (360) 671-2020 Fax (360) 671-0322 Westall Property-SWPPP 1 September,2006 • • PROJECT DESCRIPTION This project involves the construction of a residential area consisting of five buildings and associated walkways, parking areas and driveways. The purpose of this SWPPP is to provide guidance to the owner/contractor and the owner/contractor's dedicated erosion control lead in minimizing erosion and sedimentation problems due to this project. The owner/contractor is responsible to implementing all appropriate measures to meet County, State and Federal guidelines regarding water quality. This SWPPP, in conjunction with the civil plans by 2020 Engineering, Inc., describes the minimum starting measures to implement. However, additional measures may be needed based on the actual onsite performance of BMPs and the schedule and techniques used by the contractor. Contact information is provided below, and should be amended as appropriate. Project Owner: Civil Engineer: 2020 Engineering, Inc. P.O. Box 1621 Bellingham, WA 98227 Phone: (360) 671-2020 Contractor: 1 ` - Erosion Control Lead Person: Phone: Email: Fax: A copy of this SWPPP, a list of the appropriate contact persons, and copies of completed inspection forms shall be maintained onsite at all times during the project. Westall Property-SWPPP 2 September,2006 • • EXISTING CONDITIONS Location. The project is located in on the Quimper Peninsula, south of Port Townsend in Section 17, Township 29 North, Range 1 West, W.M. Jefferson County, Washington. Topography. The entire area encompasses approximately 6 acres, with the project site covering approximately 1.4 ac. The site slopes generally from west to east, with slopes from approximately 10 to 30%. Land Cover and Soils. The land is currently undeveloped. The underlying soils are characterized in general as a sandy loam or silt loam. The site has mostly hydrologic group "Type C" soils, as described by the SCS Soils Manual for Jefferson County Area, Washington. The property lies along the Port Discovery shoreline. Structures and Utilities. It is the contractor's responsibility to locate any onsite and adjacent utilities. The one-call utility locate number is 1-800-424-5555. There is a former railroad grade through the west end of the property. Onsite Drainage Description. The majority of current surface runoff sheetfiows down the ridge to the shoreline over native vegetation areas and is either infiltrated or flows offsite into Port Discovery. Contributing Offsite Areas. Due to the slopes and the location of Highway 20, no stormwater runoff will flow onto the site from offsite areas. Downstream Conveyance. Any stormwater runoff that is not detained onsite travels southeast off of the site to Port Discovery. Westall Property-SWPPP 3 September,2006 — • • PROPOSED CONDITIONS The scope of work is to grade building pads for each of the five buildings, and the associated walkways, parking areas, and driveway access to Highway 20. As much native vegetation as possible will be maintained in order to limit stormwater runoff and infiltrate any runoff that is produced. Landscaped areas will use amended soil to increase the infiltration and retention of water in the existing soils. Amended soils are existing soils with 4 inches of Grade A composted tilled into them to a depth of 8 to 12 inches. In areas where topsoil has been removed during earthwork activities, a compost soil blend consisting of 2/3 sand and 1/3 compost shall be applied on the ground surface at a depth of 12 inches to provide topsoil for lawn and landscape areas. wl Westall Property-SWPPP 4 September,2006 • • EROSION AND SEDIMENTATION CONTROL Temporary erosion and sedimentation controls (TESC) and Best Management Practices (BMPs) will be used to mitigate potential erosion and sedimentation due to construction— activities. A detailed summary of the suggested minimum gr,.osion and sedimentation control elements follows below: ! ` Element #1 Mark Clear Limits ) Prior to beginning land-disturbing activities, including clearing and grading, all work limits shall be marked. Areas to be marked include the roadway areas and their associated drainage facilities (infiltration trenches). Either wood lath stakes or painted ground surfaces may be used to mark the limits. Element #2 Establish Construction Access Any new construction access points required off of Highway 20 shall have stabilized quarry spall construction entrances (BMP C105) meeting Jefferson County standards. In addition, the adjacent roadway areas shal be cleaned at the end of each day, with swept up materials deposited in a controlled onsite sediment disposal area, or an approved offsite disposal location. Element #3 Control Flow Rates Temporary sediment traps or ponds (BMP C240 or BMP C241) shall be built if necessary to collect any surface runoff during construction to prevent sediment laden runoff from reaching offsite areas, streams or other water bodies. Siting of the traps or ponds shall be at locations where overflow can discharge into existing vegetated areas. Element #4 Install Sediment Controls The owner/contractor shall endeavor to maintain any natural vegetation in as undisturbed condition as possible. Where work is performed, the following BMPs may be used to control runoff: • Straw Bale Barrier (BMP C230). Use as a temporary emergency measure, as straw bales do not last long under heavy flow conditions. • Silt Fence (BMP C233). Place silt fence parallel to contours between work areas Westall Property-SWPPP 5 September,2006 • • and protected areas, and around exposed infiltration surfaces under construction. • Straw Wattles (BMP C235). Place where surface flow begins to channelize, to slow runoff and allow sedimentation. • Sediment Trap (BMP C240). Construct as needed to prevent dirty runoff from reaching the wetland or offsite areas. Element #5 Stabilize Soils Any exposed soils unworked for a significant period shall be stabilized using effective cover BMPs. Between October 1 and April 30, no exposed and unworked soils shall remain unstabilized for more than two days. Between May 1 and September 30, no exposed and unworked soils shall remain unstabilized for more than seven days. Soils planning to be exposed and unworked for greater than one month shall be temporarily seeded (BMP C120) or sodded (BMP C124), with adequate protection provided to stabilize the soil until the vegetation is established. Stockpiles and areas exposed for shorter periods may be stabilized using appropriate measures from the following BMPs. • Nets and Blankets (BMP C122) • Plastic Covering (BMP C123) s • Surface Roughening (BMP C130) 4 �' • Gradient Terraces (BMP C131) • Dust Control (BMP C140) Element#6 Protect Slopes Steep slopes or landslide hazard areas shall have a undisturbed vegetated buffer to protect them. The buffer shall follow requirements set forth in the land use permit. On stockpiles and ditches or temporary embankments, appropriate measures from Element #5 shall be used to minimize erosion. Element#7 Protect Drain Inlets Any drain inlets (catch basins) shall be protected by placing storm drain inlet protection (BMP C220) at each catch basin. Each basin shall be inspected weekly, and daily during significant storm events. Inlet protection shall be cleaned or replaced prior to the accumulation of six inches of sediment. Westall Property-SWPPP 6 September,2006 Element #8L. Stabilize Channel and Outlets I j Any outlets from temporary or permanent stormwater pipes or facilities IIshall be armored :-EvE'c'LL'N1 with rocks or quarry spalls to prevent scour and erosion (BMP C209). Element#9 Control Pollutants All potential pollutants, including but not limited to wash water, human wastes, chemicals, oils, fuels, vehicular lubrication and cooling fluids, miscellaneous trash and waste materials, demolition debris, pesticides, herbicides, and fertilizers shall be handled in such a manner to prevent contamination of stormwater. Stored hazardous materials shall be protected from vandalism, covered, and have spill containment in place, including plastic or other ground cover to minimize the opportunity for any spilled materials to infiltrate into the porous soils. Any spillage of hazardous materials into surface waters or into the ground shall be immediately reported to Jefferson County, the Washington State Department of Ecology, and other appropriate state or federal authorities, and immediately contained. Pesticides, herbicides or fertilizers shall not be applied during or immediately prior to expected precipitation events, and application shall follow the manufacturer's recommendations. Element #10 Control De-Watering De-watering water from trenches or other excavations shall be discharged across undisturbed vegetation areas, to allow dispersal and infiltration, or into previously constructed temporary sediment traps (BMP C240). De-watering water shall not be allowed to discharge directly onto offsite areas, except as approved by the offsite owners. Element #11 Maintain BMPs All temporary and permanent erosion and sediment control BMPs shall be maintained repaired and enhanced as necessary to assure continued performance of their intended functions. Except as previously noted, all BMPs shall be inspected at a minimum on a weekly basis, and during or immediately following a significant storm event (any storm exceeding 0.5 inches rainfall within 24 hours, or 2.0 inches of rainfall within 7 days). Within 30 days of final site stabilization or when no longer applicable, temporary BMPs shall be removed from the site. Any accumulated debris and sediments shall be disposed of at an approved onsite or offsite location, and each BMP site itself shall be permanently stabilized. Westall Property-SWPPP 7 September,2006 • • Element#12 Manage the Project The grading work shall begin only after any needed temporary sedimentation and erosion control BMPs have been put in place. Soil disturbance shall be avoided during precipitation events, and priority shall be placed on maintaining existing vegetation in work areas as long as possible. The owner/contractor's erosion control lead shall follow the previous elements of this SWPPP, the erosion control requirements from the plans, and any requirements of County, State and Federal agencies. If circumstances require additional BMPs beyond those recommended in this SWPPP to prevent construction caused contaminated runoff from leaving the project site or contaminating the onsite infiltration facilities, it is the owner/contractor's responsibility to implement those additional BMPs. Note that the proposed raingarden and dispersion trench areas are infiltration facilities. Thus, a priority of the contractor shall be to prevent silt, sediment or debris laden water from reaching the infiltration surfaces of these facilities throughout construction of the facilities and the rest of the site, so that the permanent functionality of the infiltration facilities are not impaired. The erosion control lead shall also keep a weekly log of BMP inspections, noting any problems, repairs performed, or additional BMPs used. A sample weekly inspection form is attached on the following page. Copies of this SWPPP and completed inspection forms shall be maintained onsite at all times during the project. The owner/contractor shall be aware that the Washington State Department of Ecology has the authority to levy significant fines against the project owner if runoff exceeding allowed contaminant levels due to any onsite or project activity is found to be discharging from the project site. SWPPP DRAWINGS • Approved Civil Drawings with TESC Information (by 2020 Engineering, Inc., to be attached upon approval by Jefferson County) I Westall Property-SWPPP 8 September,2006 SAMPLE SWPPP INSPECTION FORM WEEK STARTING: Name of Erosion Control Lead: Weather Comments: Condition of Site and BMPs: Exposed Soils: Silt & Construction Limit Fencing: Quarry Spall Entrances: Adjacent Roadways and Properties Catch Basin Protection: Sediment Traps and Ponds: Stockpiled Materials: Other BMPs: Repairs Made: New BMPs Installed: Other Comments: ar� Westall Property-SWPPP 9 September,2006 ! `. vrJ • SECTION II—EROSION AND SEDIMENT CONTROL PLAN Sediment and erosion control measures may be depicted on the master land use application plot plan, a stormwater site plan,and/or a separate Construction SWPPP site plan. This is a checklist to ensure that the following are depicted on a site plan: 1. General. a. Vicinity Map b. Jefferson County Approval Block c. Erosion and Sediment Control Notes 2. Site Plan. a. Legal description of subject property. b. North arrow. c. Indicate boundaries of existing vegetation(e.g.,tree lines,pasture areas,etc.). d. Identify and label areas of potential erosion problems. e. Identify FEMA base flood boundaries and Shoreline Management boundaries(if applicable). f. Show existing and proposed contours. g. Indicate drainage basins and direction of flow for individual drainage areas. h. Label final grade contours and identify developed condition drainage basins. i. Delineate areas that are to be cleared and graded. j. Show all cut and fill slopes indicating top and bottom of slope catch lines. 3. Conveyance Systems. a. Designate locations for swales, interceptor trenches,or ditches. b. Show all temporary and permanent drainage pipes,ditches,or cut-off trenches required for erosion&sediment control. c. Provide minimum slope and cover for all temporary pipes or call out pipe inverts. d. Shows grades,dimensions,and direction of flow in all ditches,swales,culverts and pipes. e. Provide details for bypassing off-site runoff around disturbed areas. f. Indicate locations and outlets of any dewatering systems. 4. Location of Detention Best Management Practices(BMPs). Identify location of detention BMPs. 5. Erosion and Sediment Control Facilities. a. Show the locations of sediment trap(s),pond(s), pipes and structures. b. Dimension pond berm widths and inside and outside pond slopes. c. Indicate the trap/pond storage required and the depth, length,and width dimensions. d. Provide typical section views through pond and outlet structure. ._._._ _ e. Provide typical details of gravel cone and standpipe,and/or other filtering devices. :l t` , f. Detail stabilization techniques for outlet/inlet. g. Detail controVrestrictor device location and details. h. Specify mulch and/or recommended cover of berms and slopes. i. Provide rock specifications and detail for rock check dam(s),if applicable. j. Specify spacing for rock check dams as required. k. Provide front and side sections of typical rock check dams. I. Indicate the locations and provide details and specifications for silt fabric. — .-i : 3 LN m. Locate the construction entrance and provide a detail. 6. Detailed Drawings. Any structural practices used that are not referenced in the Ecology Manual should be explained and illustrated with detailed drawings. 7. Other Pollutant BMPs. Indicate on the site plan the locations of BMPs to be used for the control of pollutants other than sediment(e.g.,concrete wash water). 8. Monitoring Locations. Indicate on the site plan the water qualify sampling locations to be used for monitoring water quality on the construction site. Sampling stations should be located upstream and downstream of the project site. stormwater site plan template—rev.10/1/2003 11 • r STRATUM GROUP 1451 Grant Street, Bellingham, WA 98225 Phone(360)714-9409 January 3, 2007 Bill Irvine 1980 Cape George Road Port Townsend, WA 98368 Re: Geology Review of Stormwater Plan MLA#: MLA06-00651, Case #: BLD06-00678 Jefferson County, Washington Dear Mr. Irvine: I received a memo from Michele Farfan of Jefferson County Department of Community Development regarding the stormwater plan for the proposed development at Warren Westfall's property. Jefferson County requested that I review the stormwater plan for consistency with my geology evaluation of the property that was completed in November 2003. I have reviewed the stormwater plans for the site prepared by 2020 Engineering and spoke with the Jennifer Ramsey the project manager at 2020 Engineering regarding the stormwater plan. The stormwater plan will disperse stormwater runoff on the site in a manner consistent with the recommendations I made in my November 2003 report. Buildings 1, 2 and 5 and driveway areas will discharge stormwater in a dispersed manner into areas of amended soil and into existing natural swales with existing natural infiltration. Building 4 will discharge stormwater into a raingarden with and subsequently into a dispersion trench and onto an existing gravel road drainage route that will convey water to the base of the slope where it will infiltrate behind into the ground behind the old railroad grade on the west side of the property. The stormwater plan drawing indicates that Building 3 will direct its storm water into the raingarden planned between Buildings 3 and 4. The only change I recommend is that half the stormwater from Building 3 be directed towards a dispersion trench located south of Building 3 towards the existing natural infiltration area. Stratum Group appreciates the opportunity to be of service to you. Should you have any questions regarding our reconnaissance please contact our office at(360) 714-9409. Sincerely yours, Stratum Group `� i p washj .i c>„:04,...... Dan McShane, M.Sc., L.E.G. - Licensed Engineering Geologist ` .� ; _ �� JAN 8 2007 v \' _ • S4 , Y 7i' ; f )EVE.1.OPMENT j L._ S- - 0 _, ScoLL ZFiga m�Z F I P. ��_�o� wWg 5a � i v f—f''I fe � o8w �zrii �o ZF� l' LL U. II i, - II J a� ° \yb p o o If c) >-wW2z$W� cfy2 41 o f °z. iD.44 \ _ v�i Nv�i iiLLfV 02Kg gK wjO,oKSO0a7Q,g ` r't*. — Ot zT .4 M m.�aw_wa omccu.crUmC)K?to ZLL• � z�M Z 5 5 5 13 ® 1 t_ m m m Z ! 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