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HomeMy WebLinkAboutMLA08-00509 STORMWATER SITE PLAN I ' Stormwater Site Plan Report (PRELIMINARY) for Tala Point 1 ,g,D D. 0 WAS I61- • NAL ' EXPIRES 4.-73-40:6y 1 DRS Project No. 08031 1 Owner/Applicant OPG Properties, LLC 19245 Tenth Avenue NE Poulsbo, WA 98370 ' 360.394.0573 Report Prepared by ' r � D. R. STRONG Consulting Engineers, Inc. ' 10604 N.E. 38th Place, Suite 101 Kirkland WA 98033 (425) 827-3063 Report Issue Date December 19, 2008 ©2008 D. R.STRONG Consulting Engineers Inc. I 1 TALA POINT STORMWATER SITE PLAN REPORT I TABLE OF CONTENTS ISECTION I PROJECT OVERVIEW 1 JEFFERSON COUNTY STORMWATER SITE PLAN SUBMITTAL TEMPLATE 1 I JEFFERSON COUNTY STORMWATER CALCULATION WORKSHEET 10 SECTION II OFFSITE ANALYSIS 14 I DOWNSTREAM ANALYSIS 14 UPSTREAM ANALYSIS 17 SECTION III EXISTING SITE HYROLOGY 20 I NARRATIVE 20 EXISTING HYDROLOGY 20 SOILS 20 I CRITICAL AREAS 21 OFFSITE AREAS 21 SECTION IV DEVELOPED SITE HYDROLOGY 23 INARRATIVE 23 DRAINAGE 23 OFFSITE IMPROVEMENTS 24 ISECTION V DETENTION RETENTION ANALYSIS AND DESIGN 26 HYDROLOGICAL ANALYSIS 26 I WWHM RESULTS 26 BIOFILTRATION SWALE SIZING CALCULATIONS AND HYDROGRAPHS 34 WETLAND PROTECTION 36 U SECTION VI CONEYANCE SYSTEM ANALYSIS 37 ONSITE CONVEYANCE 37 BACKWTER TABLE 38 IAPPENDIX A OTHER STUDIES 39 APPENDIX B DOWNSTREAM PHOTOS 40 IAPPENDIX C SOIL SURVEY INFORMATION 41 IAPPENDIX D OPERATIONS AND MAINTENANCE MANUAL 44 APPENDIX E AREA BREAKDOWN 45 I FIGURES FIGURE 1 VICINITY MAP 13 FIGURE 2 DOWNSTREAM MAP 18 I FIGURE 3 UPSTREAM BASIN AREA 19 FIGURE 4 PRE DEVELOPED BASIN MAP 22 FIGURE 5 DEVELOPED MAP MAP 25 I I ©2008 D.R.STRONG Consulting Engineers Inc. Tala Point Stormwater Site Plan Report Jefferson County,Washington SECTION I PROJECT OVERVIEW iJefferson County Stormwater Site Plan Submittal Template DEPARTMENT OF COMMUNITY DEVELOPMENT 621 Sheridan Street Port Townsend Washington 98368 360/379-4450 360/379-4451 Fax http://www.cojefferson.wa.us/commdevelopment/ ' STORMWATER SITE PLAN SUBMITTAL TEMPLATE ' MLA# PROJECT/APPLICANT NAME: Please answer all of the following questions to the best of your ability. Where the question calls for depiction on a site map,the applicant ' may choose to either incorporate the elements into the general plot plan for the Master Land Use Application or to submit a separate stormwater site plan map. ' Project Overview 1. Describe the proposed developed conditions of the site. Indicate position and relative size of proposed improvements on the site map. ' Tala Point is separated into three (3) separate clusters, an 8-lot development in the southwest, a 14-lot development in the southeast corner, and a 32-lot development in the northeast corner. Two of the lots in the northeastern corner are located directly adjacent to the shoreline. These clusters will comprise of roughly 1 acre minimum lots with an anticipated ' 8,000 SF of impervious area per lot(houses and driveways). The road system will have varying pavement and shoulder widths from 30 feet in width (East Ludlow Ridge Road), to 22 feet for the southwest and northwest clusters, down to 20 feet for the joint-use drive to the two(2)shoreline lots. ' The threshold discharge areas for the southwestern cluster will have its road system fully dispersed to the east towards the DNR parcel. Per the BMP's listed in the DOE Manual for roadside dispersion, a minimum of 100 feet of vegetated flow path is required. A 125-foot flow path has been provided between the proposed road easement and the Site's ' property line. The driveways and houses for lots 2-5 will have their runoff conveyed to the east side of the road system and dispersed through a 100-foot vegetative path. The driveways and houses for lots 1, and 6-8 will have their runoff dispersed to the west and northeast through a 100-foot minimum vegetative flow path. ' The threshold discharge areas of the southeastern cluster will have its road system fully dispersed to the east towards the single-family lots through an open space located between the road easement and the property lines. The minimum 100- foot flow path is measured from the edge of the road's shoulder to the single-family property line. The lots in this cluster will utilize shared driveways that will be dispersed through a 100-foot minimum vegetative path located between each lot sharing a driveway. The individual lots will also have their roof run-off dispersed through a 100-foot minimum vegetative path to the east within the adjacent open space tract. The threshold discharge areas for the northwestern cluster will utilize a combination of methods for handling the runoff generated from this area. The road system for the upper lots from lot 29 will sheet flow to the north and east before ' ©2008 D.R.STRONG Consulting Engineers Inc. 1 Tala Point Full Drainage Report Jefferson County,Washington I reaching East Ludlow Ridge Road. The roadside runoff from lot 6 south will be coveyed to a stormwater treatment tract and treated through a bio-filtration swale before entering a tight-line pipe that directly discharges into Puget Sound. The I single-family lots 3-18 will have their roof and driveway runoff dispersed through a 100-foot minimum vegetative path prior to meeting the existing steep slope areas. The runoff for lots 29-32 as well the portions of the road north of lot 29 will be sheet flow dispersed to the east. Lots 19-28 will be dispersed with a minimum flow path of 50 feet to the west, therefore requiring a minimum of a 50-foot setback from any conveyance system for the road system. IExisting Conditions Summary 2. Describe the existing topography. Indicate contours on the site map. IThe Site is situated along a point of land that extends northerly out towards Puget Sound. The developed portion is flat to moderately sloped (2-20%) and is divided by a ridgeline splitting the Site's discharge areas to primarily flowing east or I west. The western side has a series of well defined steep slope areas in excess of 40% that extend westerly down towards the lower shelf, or directly towards Puget Sound. 3. Describe the existing vegetation. Indicate native vegetation areas on the site map. IThe Site is dominated by second and third growth forest consisting primarily of Douglas Fir, Western Red Cedar, Western Hemlock, and a few clusters of Big Leaf Maple, and Red Alder. The majority of existing trees are the result of regrowth Ifollowing logging activities that have been conducted within the last 25-35 years. 4. Describe the existing soils. Indicate soil type on the site map. IThe site is listed containing Cassolary Sandy Loam (CfC and CfE) Cassolary-Kitsap Complex (CkD), Kitsap Silt Loam (KtE), Sinclair Sandy Loam (SnC), Swantown gravelly sandy loam (StB), and Whidbey gravelly sandy loam (WhC) according to the US Department of Agriculture Soils Conservation's Series Mapping. I5. 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 Imap, if applicable, and indicate acreage of each. Tala Point is primarily defined by a ridge that transects the middle of the Site dividing it into primarily easterly or westerly flow paths, separated out into eleven well-defined drainage basins and two undefined basins. Given the low permeability Iof a majority of the Site's surface soils, runoff generated will be in the form of sheet flow. The Site receives upstream runoff from the Department of Natural Resource's (DNR) parcel located in the center of the Project. Runoff generated south of Paradise Bay Road is intercepted by the road and drainage features and conveyed around the site, eliminating Iany tributary runoff from that area. The easterly portions of the Site is primarily sheet flow before becoming channelized to one of the drainage features. A portion of the runoff drains to a wetland, which is drained by a Type Ns stream. All of the channelized runoff flows easterly before exiting into Puget Sound. Runoff from the most northerly areas did not appear to have a defined flow-path and sheet-flows to Puget Sound through one of numerous separate undulating swales and drainage features. I The westerly portions of the Site sheet flows toward their respective drainage feature before being conveyed west to Puget Sound. Runoff in this area passes through steep slope areas. It did not appear that these drainage features create hazardous or highly erosive issues. The northerly areas for this divide did not appear to have a defined flow-path and I sheet-flows to Puget Sound through one of numerous separate undulating swales and drainage features. A map defining the separate flow-paths can be found in the Stormwater Site Plan Document. Describe any excess levels of noise generated by the proposed use or activity:IS. No excessive noise is expected to be generated by the Site. The noise generated will be consistent with a subdivision of this size, and will be from the single-family residences, internal road infrastructure and Paradise Bay Road. I7. 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. I ©2008 D.R. STRONG Consulting Engineers Inc. 2 Tala Point Full Drainage Report Jefferson County,Washington A Category IiI wetland has been delineated along the eastern side of the Site. A small Category IV wetland was also located adjacent to Ludlow Ridge Road. These wetlands are drained by Type Ns streams and flow to the east. The west side of the Site contains several steep slope areas with some drainage features that convey runoff to the west. A critical area study was conducted by Wiltermood Associates Inc. ' 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.). ' Tala Point is a peninsula of land that extends out into Puget Sound in a northerly direction. Surrounded by developed private property to the North, East and West, and undeveloped property to the south and Center, the Site only touches Puget Sound in the northwestern comer of the Site. The Site contains two separate classified wetlands along the eastern ' half, which is drained by Type Ns Streams. Several other drainage features drain the runoff generated by the Site into Puget Sound. There was no evidence of any fish or fish habitat in or within %mile of the Site that was tributary to Puget Sound. There is an identified Bald Eagle's nest located near the northwestern corner of the Site. The western half of the site has a long ridgeline of steep slope areas along the upper portion, and another bluff along Puget Sound. Paradise Bay Road and East Ludlow Ridge Road provide site access. An extension of an existing water system located south of the Site will be extended through the site to provide domestic water service. The developed Site will utilize a ' combination of on-site community drainfields and individual single-family drain fields since no sanitary sewer systems are located in the vicinity. ' The surrounding properties comprise of single-family residences to the north, east and west. An 80-acre parcel located in the Center of the Site, owned by the DNR, currently is undeveloped. The properties south of Paradise Bay road are also currently undeveloped. ' A critical areas study for the DNR parcel has not been generated, therefore the status and extent of any potential impacts from their parcel to the developed Site is unknown. Should any critical areas exist, the proposed development is anticipated to meet requirements of the Jefferson County Critical Ordinance for buffers and setbacks should any be ' identified. The proposed road systems for the southwestern cluster is set back 125 feet from the property line and Tala Ridge Road to the east is an existing roadway. In addition, as part of the Site development the proposed water system will pass through a portion of the DNR parcel. The water system will be extended within the existing road alignment that ' crosses through the DNR parcel. Since this road is an existing condition, no additional or adverse impacts to any potential existing critical areas are proposed or anticipated. Any work conducted inside or adjacent to the DNR parcel will meet the requirements of the Jefferson County's Critical Areas ordinance. 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. The Site consists of eleven (11) different defined threshold discharge areas and two (2) separate multiple undefined threshold discharge areas, therefore, the Site will utilize a combination of flow control methods throughout the Site. The southeastern cluster will utilize "Full Dispersion for flow control and water quality. To manage the runoff generated by East Ludlow Ridge Road, the 14 lots will be setback a minimum of 100-feet from the edge of the Road Improvements. ©2008 D.R.STRONG Consulting Engineers Inc. 3 Tata Point Full Drainage Report Jefferson County,Washington This area will provide the minimum 100-foot flow path necessary for dispersion. The lots in this area will utilize a joint-use driveway and have its runoff conveyed to the back of the lots before being dispersed through the open space tract to the ' east. The individual lots will also have their runoff dispersed for a minimum of 100-feet through the open space tract to the east. The southwestem tract will also be fully dispersed. Runoff in this area flows both to the east and west, however all of the ' runoff drains to Puget Sound to the West. The road system will be dispersed fora minimum of 100-feet to the east before exiting the Site. In addition, lots 2-5 will also have its runoff dispersed in this area to the east. The flow paths for the Road System will be combined with individual lots 2-5, but will not be concentrated in excess of the requirements listed in ' the DOE Manual. The remaining lots 1 and 6-8 will be fully dispersed through 100-minimum flow paths to the west before exiting the Site. ' The northwestern cluster will utilize combinations of drainage systems. A small portion to the north flows to the East and includes lots 29-32. These lots and the portion of the road system serving them will be fully dispersed through the open space tract separating the lots from East Ludlow Ridge Road. A 100-foot minimum flow path will be provided. Lot 3-18 will be fully dispersed through 100-foot minimum flow paths to the north and west before its runoff continues towards Puget Sound. Lots 19-28 and the road system serving those lots will be collected by a roadside ditch and conveyed to a stormwater tract located at the low point between lots 16 and 17. This runoff will then be treated through a Biofiltration swale before being tight-lined down to Puget Sound. The remaining portion of the road system that drains to the east will be dispersed through a series of dispersion trenches located in the open space tract to the south. Runoff generated by lots 1 and 2 near the shoreline will connect to the tight-line pipe serving the upper lots and directly discharge to Puget Sound. ' 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.] ' A water quality tract will be located in the northwestern cluster and contain a basic bio-filtration swale. 11. Describe the performance goals and standards applicable to the project. The Site will utilize a combination of performance standards, all of which are required to meet the standards listed in the 2005 Washington State Department of Ecology Stormwater Management Manual for Western Washington as adopted by Jefferson County. The southeastern and southwestern clusters and lots 3-18 and 29-32 of the northwestern cluster will meet the requirements of "Full Dispersion" as described in Volume V BMP T.530. The remainder of the site will be discharged directly to Puget Sound via a closed pipe conveyance system. ' 12. Describe the flow control system. ' Based upon soils information and recommendations by the Geotechnical Engineer, onsite infiltration is not a feasible option for this site. Therefore, flow control will primarily be handled through full on-site dispersion. A portion of the northwestern cluster will have its runoff directly discharged into Puget Sound. 13. Describe the water quality system. ' Water quality will be handled through the use of full dispersion through native vegetation, and through the use of a bio- filtration swale. ' 14. Describe the conveyance system analysis and design. A large-scale conveyance system will not be necessary for this project. Conveyance systems will primarily consist of 12- inch pipes and culverts necessary to convey runoff to their respective dispersion facilities. In the northwestern cluster, a roadside ditch will convey a portion of the runoff to the bio-filtration swale. From there runoff will be conveyed through a 18-inch pipe system across the lots and down the steep slope areas through a 12"HDPE pipe anchored to the hillside before being discharged into Puget Sound. Initial runoff calculations indicate that the areas that are to be directly ' ©2008 D.R.STRONG Consulting Engineers Inc. 4 Tala Point Full Drainage Report Jefferson County,Washington discharged will generate approximately 9 cfs of runoff for the 100-year storm event. Based on Manning's Equation, a 12- inch pipe in excess of 10% can handle 12.21 cfs, and an 18-inch pipe at 2% can handle 16.09 cfs. This should be a ' reasonable approximation for preliminary evaluation. A full backwater analysis will be provided after preliminary review and approval. 15. Describe the source of fill material, physical characteristics of fill material, and deposition of excess material. ' it is anticipated that this site will generate balanced cut and fills. It is not anticipated that excess cut will need to be exported from the site, nor is any soil import planned. Placement of earthwork will be based upon the Geotechnical Engineers Recommendations. 16. Proposed methods of placement and compaction consistent with the applicable standards on Appendix Chapter 33 of the ' Uniform Building Code. Methods of placement and compaction will follow strict adherence to the UBC and per the Geotechnical Engineer's recommendations. ' 17. Describe the proposed surfacing material. ' The road system will be designed to meet the requirements of Jefferson County Road Standards. Driveways will be constructed with either Concrete, Asphalt, Pervious Pavement or a combination of said materials. Roof materials will likely be comprised composite materials typical of single family residences. 18. Describe methods for restoration of the site. Large portions will remain undeveloped or under selective harvesting. The developed portions of the site will be restored with landscaping and permanent plantings ' 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. An O&M manual will be included in the Stormwater Site Plan document and will be provided at the time of the Final Stormwater Site Plan design, which will be conducted after preliminary review and approval. 20. List here and include any special reports or studies conducted to prepare the Stormwater Site Plan. Geotechnical Engineers Report ZZA Terra con Critical Areas Study liltermood Associates, Inc. Bald Eagle Habitat Study Fleming Ecological Services Traffic Study Geri Reinart Groundwater Hydrological Analysis Bender Consulting, Inc. ' 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. ' NOl Permit Forrest Practice Permit HPA Permit ' Shoreline Development Permit Jefferson County Master Permit ©2008 D.R. STRONG Consulting Engineers Inc. 5 Tala Point Full Drainage Report Jefferson County,Washington I I *Note:conditions for each will be listed upon permit review and/or preliminary review and approval. ICONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN (SWPPP) I 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 IPractices(BMPs)Packet for guidance, particularly with rural residential development. SECTION I—CONSTRUCTION SWPPP NARRATIVE I 1. Construction Stormwater Pollution Plan Elements. Describe how each of the Construction SWPPP elements has been or I 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). I12 Required Elements—Construction SWPPP 1. Mark Clearing Limits. IA full SWPPP plan meeting all 12 requirements will be provided after preliminary approval in an effort to minimize the number of submittals and to better coordinate with the approved Site Plan as prescribed by the Hearing Examiner. The following responses are a written summary of the proposed SWPPP plan for each of the 12 segments: IThe clearing limits will comprise the areas need for the road system, individual lots (for utility hook-ups), required storm drainage facilities, water system, and community drainfrelds. The remaining site will be left as native open space, with the I exception of select timber harvesting. Individual SWPPP plans will be developed for each individual lot at the time of building permit. In addition, a separate forest practice permit will be obtained for select timber harvesting. 2. Establish Construction Access. I There will be a total of 3 construction entrances for the entire scope of work. The first will be located near the southwestern section of the site at the location of the existing logging road entrance onto Paradise Bay Road. The 1 second located at the intersection of East Ludlow Ridge Road and Paradise Bay Road. The third will be on the south side of Paradise Bay Road to be used for the installation of the domestic water system. I3. Control Flow Rates. The flow rates will be per the required DOE BMP's such as the use of swales, rock check dams, hay bails, TESC ponds and dispersion pads. I 4. Install Sediment Controls. I The sediment will be controlled through the used of sediment traps and ponds, silt fencing and all other required BMP's listed in the DOE manual. I5. Stabilize Soils. Soils will be stabilized through the use of permanent and temporary planting, straw mulch, covering soil stockpiles and exposed soils, and all other required BMP's as necessary per the DOE manual. I6. Protect Slopes. I ©2008 D.R.STRONG Consulting Engineers Inc. 6 Tala Point Full Drainage Report Jefferson County,Washington The SWPPP plan will closely follow all recommendations prescribed by both the DOE manual, and per the Geotechnical Engineer's recommendations. 7. Protect Drain Inlets. All culverts and catch basins will be protected through the use of catch-basin inserts, silt fences and debris barriers. t8. Stabilize Channels and Outlets. ' All temporary channels will be monitored to maintain soil stability with channels. All outlets will be armored with riprap energy dissipating pads. ' 9. Control Pollutants. All pollutants, including water materials and demolition debris that occur on-site during construction will be disposed of in a manner that does not contaminate stormwater. ' 10. Control De-Watering (the act of pumping groundwater or stormwater away from an active construction site). ' De-watering will be treated in the same manner as surface runoff is treated 11. Maintain Best Management Practices(BMPs). ' The developer and contractor will be required to follow and manage the implemented BMP's per an approved SWPPP plan and NOl permit throughout the life of the construction project. ' 12. Manage the Project. The project will be phased where feasible to prevent transportation of sediment. Certain activities will be limited or ' restricted based on seasonal limitations. Inspection and monitoring will be conducted by a Certified Professional in Erosion and Sediment Control. A copy of the SWPPP plan will be kept on-site at all times. ' 2. Adjacent Areas. a. Description of the adjacent areas that may be affected by site disturbance (e.g., streams, lakes, wetlands, residential areas, roads). ' The Site lies in a point of land surrounded by Puget Sound. A portion of the property's western side reaches Puget Sound. The remainder of the western, northern and eastern property is separated from Puget Sound by private property. ' Several drainage courses transect the private properties to the east and west before reaching the Puget Sound. No adverse impacts to any of the downstream properties are anticipated. ' b. Description of the downstream drainage path leading from the site to the receiving body of water (minimum distance of 400 yards). ' There were eleven (11) separate downstream paths from the Site down to Puget Sound. A detailed description of each flow path can be found in Section 1 of the Stormwater Site Plan document. ' 3. Environmentally Sensitive Areas. a. Description of environmentally sensitive areas that are on or adjacent to the site ' Wiltermood Associates Inc. was hired to identify and classify any streams and wetlands on the site. A Category Ill wetland was identified along the eastern side of the project and a small Category IV wetland was identified on along side of East Ludlow Ridge Road. This wetland system is drained by a small Type Ns Stream that continues to the east. ' ©2008 D.R.STRONG Consulting Engineers Inc. 7 Tala Point Full Drainage Report Jefferson County,Washington 111 Several other drainage courses were identified exiting the site. There is also an unclassified stream/drainage course that cuts across the southwestern corner of the site. In addition, there appears to be another stream located offsite east of the ' northern reach of East Ludlow Ridge Road. Puget Sound reaches a portion of the western side of the property. b. Description of special requirements for working in or near environmentally sensitive areas. ' Site construction will follow minimum requirement number 8 "Wetlands Protection as prescribed by the DOE Manual. This will include maintaining the required buffers as required by Jefferson County Code (65-foot buffer for Cat Ill Wetlands, 50- foot Buffer for Cat IV Wetlands, and 50-foot buffers for Type Ns Streams), through non-disturbance. in addition, runoff tributary to the stream and wetland generated by construction activities will be fully dispersed before reaching the critical area, providing water quality, and maintaining the existing hydrology. The steep slope areas will be delineated and have a 35-foot buffer established from the top of slope. 4. 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 site is mostly comprised of a moderate layer of Glacial Till(+0-60 feet) over the top of a thick layer of outwash soils. This soil has a moderate level of erosiveness, and a very low level of permeability. County mapping shows that there may be a landslide hazard along the western steep slope area. Preliminary Geotechnical Reports state recommend a minimum building setback of 75 feet from the top slope. A 35-foot buffer per Jefferson County Code will be maintained from the top of slope. ' 5. Construction Phasing. a. Construction sequence Construction sequences will be determined after Preliminary Plat review and approval. ' b. Construction phasing (if proposed) ' Construction phasing, though likely, will not be determined until after Preliminary Plat review and approval. 6. Construction Schedule. Wet season is October 1 through April 30 (page 2-21 of the Manual). I. Provide a proposed construction schedule. The construction schedule will be developed after preliminary review and approval. It is anticipated that construction will commence in the spring-summer of 2010. II. Wet Season Construction Activities. a. Proposed wet season construction activities. ' A wet and dry season construction activity plan will be developed as part of the SWPPP plan, which will be completed after Preliminary Plat approval. b. Proposed wet season construction activities for environmentally sensitive areas. No construction activity is anticipated within any environmentally sensitive areas during the wet season. ' 7. Financial/Ownership Responsibilities. a. Identify the property owner responsible for the initiation of bonds and/or other financial securities. Ol'ympic Property Group LLC or their successors will be responsible for all bonds and financial securities related to this project. ' b. Describe bonds and/or other evidence of financial responsibility for liability associated with erosion and sedimentation impacts. ' ©2008 D.R.STRONG Consulting Engineers Inc. 8 Tala Point Full Drainage Report Jefferson County,Washington Specific bonds and sureties will be determined prior to construction plan approval. ' 8. Engineering Calculations. Provide Design Calculations on a separate sheet for the following, if applicable. a. Sediment Ponds/Traps. Sediment ponds and traps will be sized and located as part of the SWPPP plan, which will be prepared after Preliminary Plat approval. b. Diversions. ' No runoff diversions are proposed for this site for the southeastern and southwestern clusters. The northwestern cluster will have it's a portion of its runoff collected at one location and point discharged to Puget Sound. This will divert small ' tributary areas from their natural discharge point, however, the affected discharge areas are not identified as streams and empty directly into Puget Sound, a very short distance beyond the property line. Therefore this diversion is not expected to have an adverse impact on the downstream paths. C. Waterways. There are no planned alterations to any waterways as part of this project. d. Runoff/Stormwater Detention Calculations ' Preliminary Runoff Calculations have been generated and are included in Section 5 of the Stormwater Site Plan Document. 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. Show 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. ' ©2008 D.R.STRONG Consulting Engineers Inc. 9 Tala Point Full Drainage Report Jefferson County,Washington 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. f. Detail stabilization techniques for outlet/inlet. g. Detail control/restrictor 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. 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 quality 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 Changes If the designer wishes to make changes or revisions to the originally approved Stormwater Site Plan, the proposed revisions shall be submitted to DCD prior to construction. The submittal shall include substitute pages that include all proposed ' changes, revised drawings showing any structural changes, and any other supporting information that explains and supports the reason for the change. Final Corrected Plan Submittal ' If the project included construction of conveyance systems, treatment facilities, flow control facilities, or structural source control BMPs (not standard on-site stormwater management BMPs), the applicant shall submit a final corrected plan ("as- builts") when the project is completed. These should be engineering drawings (stamped by a licensed civil engineer) that accurately represent the project as constructed. APPLICANT SIGNATURE ' By signing the Construction SWPPP 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. �knr Poi-/ I - 1Z,.,23 Os (LANDOWNER OR AUTHORIZED REPRESENTATIVE SIGNATURE) (DATE) THIS SPACE MAY BE USED FOR ADDITIONAL NOTES,IF NEEDED: ' ©2008 D.R.STRONG Consulting Engineers Inc. 10 Tale Point Full Drainage Report Jefferson County,Washington I I 1 ON �� cow JEFFERSON COUNTY I Fkiii DEPARTMENT OF COMMUNITY DEVELOPMENT 621 Sheridan Street• Port Townsend •Washington 98368 I 360/379-4450 • 360/379-4451 Fax http://www.co.jefferson.wa.us/commdevelopment/ IStormwater Calculation Worksheet Cf ,# PROJECT/APPLICANT NAME: Tala Point Preliminary Plat I 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 Iinvolves stormwater review. The basic information will also be helpful for completing a Stormwater Site Plan,if required. PARCEL SIZE(I.E.,SITE) I Size of parcel 262.7 _acres An acre contains 43,560 square feet. Multiply the acreage by this figure. Size of parcel in square feet_ 11,444,972 _sq/ft ILand-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. I 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. ILAND DISTURBING ACTIVITY,CONVERSION OF NATIVE VEGETATION,AND VOLUME OF CUT/FILL I 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: 270,000' Does the project convert%acres or more of Construction site for structures -q/ft native vegetation to lawn or landscaped areas? I 100,0002+178,8183 Drainfield,septic tank,etc._ q/ft Circle: Yes No Well,utilities,etc. 7,768° sq/ft Does the project convert 2 1/2 acres or more of native vegetation to pasture? I Driveway,parking,roads,etc._ 162,0005•'+514,5936 Circle: Yes No Lawn,landscaping,etc. 1,933,6577 sq/ft I Other compacted surface,etc._ sq/ft Indicate Total Volumes of Proposed: Total Land Disturbance 3,166,836 sq/ft Cut 21,993 Fill- 21,993 (cu/yd) I *See appendix E for footnotes and explanation of area breakdowns. Istormwater talc worksheet-REV.2/20!2208 1 I ©2008 D.R.STRONG Consulting Engineers Inc. 1 1 Tala Point Full Drainage Report Jefferson County,Washington I I IImpervious 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 I 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 CALULATIONS–IMPERVIOUS SURFACE INEW EXISTING Structures(all roof area) _ 270,000' —sq/ft Structures(all roof area) sq/ft I Sidewalks sq Patios sq lft Patios sglft Patios sq/ft Solid Decks sq/ft Solid Decks sq/ft I (without infiltration below) (without infiltration below) Driveway,parking,roads,etc 338,5898 sq/ft Driveway,parking,roads,etc_ 81,5009 —sq/ft 1 Other sq/ft 608,58910 Other sq/ft Total New _ _sgfft Total Existing _ 81,500 _sglft ITOTAL NEW+TOTAL EXISTING* _ 690,089 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. IDEVELOPMENT v.REDEVELOPMENT Divide the total existing impervious surface above by the size of the parcel and convert to a percentage: 0.06% ' Does the site have 35%or more of existing impervious surface? Circle: Yes No FURTHER INSTRUCTIONS: If the answer is yes,the proposal is considered redevelopment and the attached Figure 2 should be I 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 I 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, I 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 StomrwaterManagement Manual. APPLICANT SIGNATURE I 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. I Z r -tDofi '1 ,1!/9 n/9 l 1 z3 -G (LANDOWNER OR AUTHORIZED REPRESENTATIVE SIGNATURE) (DATE) ` a, f{,.els 4 + � ( E .- s".`7 Js-' ,.v , -x¢ a . _- -" - T . -- s teer ' ; � ¢ F stormwater calc worksheet—REV.2/202008 2 I *See appendix E for footnotes and explanation xplanatton of area breakdowns. I ©2008 D.R.STRONG Consulting Engineers Inc. 12 Tala Point Full Drainage Report Jefferson County,Washington I IFIGURE 1 VICINITY MAP ,,,,.„.7,,,::,, ?fir: � ;":`� " �'.. 4 t t,�.IC�OLL31^.�aIIp�BLI�DG � :04,:lii:ol:..:.7.1::%.C.14:.,,,,,,1 _ - Ei re"�r� 1,- :44 - ''‘,..7',.___ __,,,,,,,,.... c�' s'(°.s'.`.$ VyAS�, ,t;••t» • jp._,S ,t,�`! u z. W .,f, ,v , . for - ' €_,,yi l " rr .• ,.<'`�. 'f;;� ., . ,.P€rt.-Ludlowr. I t4,!'Ny,K: :* : - MN x"C S`.. i>A J.rkt :S,. '.,'?r q,5,,.:: ?s;.7'47.14._ . i 1 : y3 • • ^ ` s fSITE 4_-a,4 Twigs,Th .� V,f calk , � � 3 .,!{� `�s�'y..,.-4.:' tale,t -"''' '' ii•-•ite ,,f4,,,,,,...,;:,z4,,,, ,,:te::44,, ::,..,:„: . .•... :•,„ _. „..., _ .. . . _ . • , . . • ..., .,...• ,t.,-.A „,„:_.,... .,,•*.f..,•. . .... •• .: .. ._.... • : „,f--:.':!.$ .- . -, - - - - `�^W ., .` k .new. , •;,',.!y:•:;.4.4.,-,:1,14.4,1-10.- ' *"•'y "'.•> •+`��a`) . .s; :` 4 i x_ - •iia TNS '..• ", # ' •a .... ^.r.°2 ,,.. . tr:2OQ$Te•le Atlas `�_ :+' ` t�+ <.. Y::, yIM K :5 5- e ' Image 7.7'0Dg Eiaita3�'v Ge :X ' �,�'..-'40� .e� ,•2.: ',2GC'S;Et opa TviJ71,tios�itB ° I F�airter 47`S5'34.z3-M 122-4C:3-4.6Y:'V rinv Oft " y5ireariIi. IMIlllil''iltn.,' Y I • • b ; 4. s, a ait`9 ri32r" Map courtesy of Google Earth I I I I ©2008 D.R.STRONG Consulting Engineers Inc. 13 Tala Point Full Drainage Report Jefferson County,Washington SECTION II OFFSITE ANALYSIS DOWNSTREAM ANALYSIS General Note The following offsite analysis was conducted under clear and dry conditions. During the initial ' field reconnaissance, it was determined that due to topography and field conditions, it could appear that with every undulation of the land, a separate downstream path could be mapped. This would lead to endless paths being mapped and analyzed and would not be practical or 1 helpful to the Project. Therefore, engineering judgement was used to determine the downstream paths that best illustrate the drainage patterns for the area. Those paths are described herein and depicted in FIGURE 2. WESTERN SIDE Downstream Path 1 ' Downstream Path 1 begins approximately 640 feet north of the southwest property corner located along Paradise Bay Road. Runoff exits the Site in a westerly direction via a large ravine. That contains the path is in the range of 120 to 140 feet in depth with a more defined ' channel at its vertex. The channel conveys seasonal flows, varies in width and depth, is riddled with fallen trees and is surrounded by dense vegetation. The channel appears to be root stabilized, with no real signs of erosion or incision. Approximately 660 feet downstream of ' the Site, the ravine shallows up to nearly 50 feet. Approximately 140 feet downstream of this location, runoff enters a 36" Corrugated Metal Pipe (CMP) crossing underneath Ludlow Bay Road. The inlet was clean with negligible sediment buildup. The outlet was partially collapsed due to the surrounding rockery and had noticeable sediment buildup. Runoff continues through a grass-lined channel before entering an 18" Reinforced Concrete Pipe (RCP). Runoff exits the 18" RCP into a rock lined channel with what appears to be one rock-check dam. No flow was observed throughout this portion of the downstream path. Runoff continues through a grass lined swale with substantial standing water for approximately 280 feet before discharging to Ludlow Bay. The downstream analysis of this path was terminated at Ludlow tBay. Downstream Path 2 ' Downstream Path 2 begins approximately 40 feet northeast of the southwestern most corner along Ludlow Bay Road. Runoff exits the Site in a westerly direction via a 12-inch RCP. The ' culvert is partially full of sediment at the inlet and outlet with no defined channel downstream of the culvert. Due to the topography of the area, it was assumed that runoff sheet flows towards Ludlow Bay. No flow was observed along the entire length of this path. The downstream ' analysis of this path was terminated at Ludlow Bay. ©2008 D.R.STRONG Consulting Engineers Inc. 14 Tala Point Full Drainage Report Jefferson County,Washington Downstream Path 3 Downstream Path 3 begins at the west side of Ludlow Bay Road directly opposite the property located at 1051 Ludlow Bay Road. Runoff exits the Site to the west via an 18" High-Density Polyethylene (HDPE) pipe culvert. There exists a clear, incised channel upstream of the ' culvert. Downstream of the culvert was a clean, rock lined channel, with no observed flow. Runoff meanders through this channel before reaching a manmade square concrete channel (13" Depth X 21" Width). A series of concrete weirs were placed within the steeper portions of the channel, presumably to slow the velocity of runoff being conveyed through the channel. The square channel transitions to a trapezoidal channel (31" Top Width X 16" Bottom Width X 13" Depth) before entering a 12" RCP which conveys runoff to Ludlow Bay. No flow was ' observed along the entire length of this path. The downstream analysis of this path was terminated at Ludlow Bay. ' Downstream Path 4 Downstream Path 4 begins at the west side of Ludlow Bay Road directly opposite the property ' located at 1131 Ludlow Bay Road. Runoff exits the Site to the west via a 12" RCP. The culvert is partially blocked at the inlet, with no blockage at the outlet. Downstream of the culvert, runoff is conveyed west via corrugated plastic channel before entering a square concrete channel (6" Depth X 35" Width). The concrete channel disperses into what appears to be a boggy area and eventually to Ludlow Bay. No flow was observed along the entire length of this path. The downstream analysis of this path was terminated at Ludlow Bay. ' Downstream Path 4a Downstream Path 4a exits the site through adjacent properties on the east side of Ludlow Bay Road as sheet flow in base of swale. Flow enters a roadside ditch as sheet flow along a private gravel road extension of Ludlow Bay Road and travels south to join downstream flow- ' path 4 before entering a culvert under Ludlow Bay Road. ' Downstream Path 4b Downstream Path 4b consists of sheet flow and multiple separate swale flows from the west edge of the Site. These flows transverse steep slopes areas and crosses an old logging road continuing as sheet flow before discharging into Puget Sound in multiple separate flow-paths. EASTERN SIDE Downstream Path 5 Downstream Path 5 begins at the intersection of Paradise Bay Road and East Ludlow Ridge Road. Runoff crosses under East Ludlow Ridge Road on the north side of Paradise Bay Road ' with an 18" RCP. It appears that runoff exits the culvert into a moderately sized ravine. It appears that the ravine that contains the path is in the range of 40 to 50 feet in depth with a more defined channel at its vertex. The channel, which appears to convey seasonal flows, varies in width and depth and is riddled with fallen trees and is surrounded by dense vegetation. The channel slopes in the range of six to nine percent with approximate dimensions of 22" deep by 34" wide. This flow-path meets up with a culvert that drains a ' ©2008 D.R.STRONG Consulting Engineers Inc. 15 Tata Point Full Drainage Report Jefferson County,Washington ' portion of the property south of Paradise Bay Road. Based upon historical information, this appears to be the flow-path of the headwaters for the Type Ns Stream. Approximately 850' downstream of the intersection of Paradise Bay Road and East Ludlow Ridge Road, a tributary drainage path originating on site appears to intersect this flow path. Continuing in an easterly direction, runoff is conveyed beneath Tala Shore Drive South via an 18" concrete culvert. ' Runoff discharges to a large, heavily vegetated ravine that was inaccessible. Runoff discharges to Puget Sound. No flow was observed along the entire length of this path. The downstream analysis of this path was terminated at Puget Sound. ' Downstream Path 6 Downstream Path 6 begins at the western property line 301 Tala Shore Drive. Runoff exits the Site via a moderately sized ravine with no defined channel at the vertex. Soils appear to be loamy with minimal rock or gravel. Runoff is conveyed underneath Tala Shore Drive South via ' an 18" concrete culvert. The culvert discharges to a man-made rock-lined channel (40" Width X 10" Depth) before reaching an 18-inch CMP. The 18-inch CMP conveys runoff across the property to a junction box on the adjacent property. Runoff is diverted easterly to a man-made ' concrete swale (4.6' Top Width X 1.7' Bottom Width X 1.5' Depth) and discharged to Puget Sound. The swale discharges at the top of a near-vertical cut (40-60 tall) into Puget Sound. No flow was observed along the entire length of this path. The downstream analysis of this path was terminated at Puget Sound. Downstream Path 7 ' Downstream Path 7 begins at the eastern property line at Tala Shore Drive. Runoff exits the Site to the east via a 24-inch CMP. The bottom of the pipe appears to be rusted out at the inlet. The culvert discharges to a large ravine with a well-defined channel at its vertex. The ravine is heavily vegetated and is approximately 60 to 70 feet in depth. The ravine outlets at a near vertical cut and discharges runoff to Puget Sound. Trickle flow was observed. ' Downstream Path 8 Downstream Path 8 encompasses sheet flow discharging from the Site along the eastern property line north of Downstream Path 7. Runoff sheet flows across the adjacent properties and is intercepted by a roadside ditch on the west side of Tala Shore Drive. Runoff is diverted north through the roadside ditch and series of 12-inch CMP's (to convey runoff under driveways). Sediment build up was observed in the culverts. A private road extends off of the ' north end of Tala Shore Drive. Runoff reaches a 12-inch concrete culvert that conveys runoff east beneath this private road. Approximately two-inches of sediment build up was observed in the culvert. The channel downstream of the culvert ranges from two to five feet in depth as it heads in an easterly direction. Runoff continues east to Puget Sound. i Downstream Path 9 Downstream Path 9 consists of runoff discharged across the eastern property line of the Site ' adjacent to the southern portion of 821151002. Runoff is collected in a newly constructed catch basin located on the west side the private road. The catch basin discharges to the east via six-inch PVC pipe through a series of cleanouts before reaching a tightline conveying runoff ©2008 D.R. STRONG Consulting Engineers Inc. 16 Tala Point Full Drainage Report Jefferson County,Washington down the slope to Puget Sound. The pipe crosses the drainage path for Downstream Path 10. No flow was observed. Downstream Paths 10 tDownstream Paths 10 consists of runoff discharged across the eastern property line of Site. Runoff Sheet flows across the adjacent properties, is conveyed across the private road via an eight-inch ductile iron pipe (DIP). Standing water was observed on either side of the road. A channel was evident downstream of the culvert. The channel continues in a southeasterly direction before converging with Downstream Path 8. ' Downstream Path 11 ' Downstream Paths 11 consists of runoff discharged across the eastern property line of Site. Runoff Sheet flows across the adjacent properties, is conveyed across the private road via 24- inch CMP. The 24" culvert discharges easterly to a three-foot wide by three-foot deep channel with approximately six-inches of standing water. Runoff enters a 12-inch culvert of unknown material under another driveway before discharging to Puget Sound. Upstream Analysis The site has tributary area from two separate upstream areas as shown in Figure 3. The first is the 80-acre DNR parcel located in the center of the site. This upstream area is divided by a ridgeline that runs down the center of the parcel in a north-south direction. The eastern half contributes sheet-flow runoff that flows directly east towards East Ludlow Ridge Road. This ' runoff generally sheet-flows across East Ludlow Ridge Road. The western half of the property sheet-flows to a depressional area located near the property line separating the DNR parcel and the Site. This depressional area then flows north as concentrated flow to a location approximately 1000 feet south of the northwest corner of the DNR parcel before discharging to an existing drainage feature north of the 8-lot cluster, continuing westerly before outfalling into Puget Sound through Flow Path 3. A small portion of the Site, located in the far Southwestern corner receives runoff from a narrow 86 acre strip of land to the south. This runoff is received by the site as concentrated flow and is culverted under Paradise Bay Road. ' The remaining runoff generated from the south is intercepted by the roadside ditch on the south side of Paradise Bay road. This runoff is then conveyed around the southeastern corner of the site towards Puget Sound to the east, joining Flow Path 5. 1 t ©2008 D.R.STRONG Consulting Engineers Inc. 17 Tata Point Full Drainage Report Jefferson County,Washington I ' FIGURE 2 DOWNSTREAM BASIN MAP 1 1 I I ©2008 D.R.STRONG Consulting Engineers Inc. 18 Tala Point Full Drainage Report Jefferson County,Washington SNE 1 w zffi d� id NISV8 Wd�2�1SNMOa 1 OW '� =a�LL< s Z (1J1� in " ion ° ,6 � �� <3^ Z 8 I I- V dogn x mmat2 o g a n><,qm = 8 U :I 8 f 1NIOd V1V1 �Z =Ya�� � � ap e p•U z .1. a o a �i t.,,,,?. „.„.„. , ...„)„, , \ c,, ,,, 1 0 0 co s \\,a,t2q„,-,,yocc-ivoyvt_3'co-i c - 4 . , 'p; fi' \-<aL,lq.),1))).1,;0 \-yA\14411,),. ,. . z.,,7k.:::. 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The Site is almost completely undeveloped with the exception of East Ludlow Ridge Road. The upper portions of the Site are flat to moderately sloped (2-20%) and is divided by a ridgeline splitting the Site's discharge areas to primarily ' flowing east or west. The western side has a series of well defined steep slope areas in excess of 40% that extend westerly down towards the lower shelf, or directly towards Puget Sound. Developed property abuts the Site to the north, east and a majority of the western ' side. The south and center of the Site are undeveloped parcels. Paradise Bay Road crosses the southern portion of the Site. East Ludlow Ridge Road is a private road containing 14 feet of pavement and 4-8 foot shoulders on either side runs up the eastern side of the Site and ' serves the existing 16-lot development to the north. A small portion of the Site, located in the far Southwestern corner receives runoff from a narrow 86 acre strip of land to the south. This runoff is received by the site as concentrated flow and is culverted under Paradise Bay Road. ' The Site is dominated by second and third growth forest consisting primarily of Douglas Fir, Western Red Cedar, Western Hemlock, and a few clusters of Big Leaf Maple, and Red Alder. ' The majority of existing trees are the result of regrowth following logging activities that have been conducted within the last 25-35 years. ' Existing Hydrology Tala Point is primarily defined by a high point that transects the middle of the Site dividing it into primarily easterly or westerly flow paths, separated out into eleven well-defined drainage basins and two undefined basins. Given the low permeability of a majority of the Site's surface soils, runoff generated will be in the form of sheet flow. The Site receives upstream runoff from ' the Department of Natural Resource's parcel located in the center of the Project. Runoff generated south of Paradise Bay Road is intercepted by the road and drainage features and conveyed around the site, eliminating any tributary runoff from that area. ' The easterly portions of the Site is primarily sheet flow before becoming channelized to one of the drainage features. A portion of the runoff drains to a wetland, which is drained by a Type ' Ns stream. All of the channelized runoff flows easterly before exiting into Puget Sound. Runoff from the most northerly areas did not appear to have a defined flow-path and sheet- flows to Puget Sound through one of numerous separate undulating swales and drainage ' features. The westerly portions of the Site sheet flows toward their respective drainage feature before ' being conveyed west to Puget Sound. Runoff in this area passes through steep slope areas. It did not appear that these drainage features create hazardous or highly erosive issues. The northerly areas for this divide do not appear to have a well defined flow-path and is ' concentrated through one of numerous separate undulating swales and drainage features before discharging separately into Puget Sound. ' Soils The site is comprised of several soil types. These groups include Cassolary, Coastal Beach, Kitsap, Sinclair, Swantown and Whidbey series soils. See Appendix C for the NRCS Soils ©2008 D.R.STRONG Consulting Engineers Inc. 20 Tala Point Full Drainage Report Jefferson County,Washington I map and the Geotechnical Engineer's Report prepared by ZZA Terracon for more detailed soil information. ICritical Areas I A Category III wetland has been delineated along the eastern side of the Site. A small Category IV wetland was also located adjacent to East Ludlow Ridge Road. These wetlands are drained by Type Ns streams and flow to the east. The west side of the Site contains I several steep slope areas with some drainage features that convey runoff to the west. A critical area study was conducted by Wiltermood Associates Inc. I In addition, a small Type Ns Stream was identified near the entrance to the Site near the intersection of East Ludlow Ridge Road and Paradise Bay Road. This stream system appears to be culverted under Paradise Bay Road to the southeast of the existing intersection. I Offsite Areas I Access to East Ludlow Ridge Road is provided by an easement through an adjacent parcel located in the southeastern corner of the Site out to Paradise Bay Road. Paradise Bay Road separates a small portion from the rest of the parcel near the southwestern corner of the Site. I Currently Paradise Bay Road consists of 22 feet of pavement (11-foot drive aisles), and 2-4 foot shoulders. I A critical areas study for the DNR parcel has not been generated, therefore the status and extent of any potential impacts from their parcel to the developed Site is unknown. Should any critical areas be found, the proposed development is anticipated to meet requirements of the I Jefferson County Critical Ordinance for buffers and setbacks. The proposed road systems for the southwestern cluster is set back 125 feet from the property line, which should provide enough buffer area if necessary. IEast Ludlow Ridge Road is an existing roadway and therefore should be exempt from being considered a new impact to any unknown critical area located on the eastern side of the DNR IParcel. In addition, as part of the Site development the proposed water system will pass through a portion of the DNR parcel. The water system will be extended within the existing road alignment that crosses through the DNR parcel. Since this road is an existing condition, Ino additional or adverse impacts to any potential existing critical areas are proposed or anticipated. Any work conducted inside or adjacent to the DNR parcel will meet the I requirements of the Jefferson County's Critical Areas ordinance. I 1 ©2008 D.R.STRONG Consulting Engineers Inc. 21 Tala Point Full Drainage Report Jefferson County,Washington I ' FIGURE 4 PRE-DEVELOPED BASIN MAP 1 1 I I I I t ©2008 D.R.STRONG Consulting Engineers Inc. 22 Tala Point Full Drainage Report Jefferson County,Washington 4 o d`VW NISV8 GadO19A90-31d [ !Iib o $ rN 2 A Z O INIOd Y1VI F a ami°4 i F ti J '��NrnN 8 U U fir' zYv2a no . - f g Ff w - 1 r VP\f)..\47\ 'IlItC.,);.(\'‘\lf:70,;} <' 572' o . i Atm 1- t e), 3 rr, 7.. \15. 1,0,0.: FJ \ '� 9J . 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''ji 3 . 1, i °j4 � '�) 1'' ,'7`' f 4 ,'k` . r tf ,�,::1 . .;,€ : , p ..�-:� � r.•�,'� �:. lti�ti-9�r.�+, rj � p q�'� 1'l t ':� �s 4st?r;, s�'k. • � f ;_s. t 44;i-,-,ivir- .tok-o.yi„,?' - inir. -,,,,-;fil&I. ,:' 1,... / /, ',31 s. 1 A 0( ti4. ..,,,,,,,,.., / {,,, ,-,,,,I \\ .t,:',,4,•ift:: ,t.''112-,.74, 1:1\ -f, ;iti,i,1:I (7.it:::Etzv5i1/4,-, '',:ii,,,,,;i•ir :?js 00,c.'f.e!4 ,) elk.',t.,..... :,),.-",.. -s, op ' 1 9,£1'• t ,' t, i,%1 . \':3 t i k 3trill �♦ X41: , 5- ( /fVii,''':4Cegi `ii : , \•,415:1.,,,,,,,6". f,,,,' :,,, t). '''',41,r-,4,,, i' s t 3 *. , _'fir ; 1'1 s„ e" � 8. ��{1 tq4{�t+�r'•r it� �,4.1' }3e�."^"3�ry}.J # { fp r e'3' r2e.,,,a,,,-4,•.{�(� �±- ,i if} i -4(r i 11? i‘ 1 ,;;„tvw--;,-_iiirt ,A 1 i, , „ey,t,:i, ® Q f tit * : , , °-' t. 1 l3`... f- . gid! :, 1, ty - `3•✓k'•t is 6 `\ ripi) ) '4)r_i 1 L.?„,,,,4141t rri-,' Ail, ; 1 ppp I , S J [ F, ) : MN NIS NM MINI MIN 11111 NU 1E11 MIN NE MK MINI MINI 1111111 MINI Mill MINI INN ri SECTION IV DEVELOPED SITE HYDROLOGY ' Narrative The portion of the Site to be developed is approximately 77.78 acres (3,388,430 SF). This ' area will be developed into 54 single-family residential lots, private road system and Community Drainfield System. The remainder of the site is to remain in an undeveloped vegetative state with select timber harvesting activities. This represents an approximate ' overall development of 29.61%. This project is classified as a "Large Project" and therefore required to meet the ten minimum requirements for storm drainage The Site consists of eleven (11) different defined threshold discharge areas and two (2) separate multiple undefined threshold discharge areas, therefore, the Site will utilize a ' combination of flow control methods throughout the Site. For the purposes of this report the individual lots will assume an 8,000 SF of impervious area for Roof, Driveway and walks for areas not fully dispersed, which is conservative. ' Drainage ' The southeastern cluster will utilize "Full Dispersion for flow control and water quality. To manage the runoff generated by East Ludlow Ridge Road, the 14 lots will be setback a minimum of 100-feet from the edge of the Road Improvements. This area will provide the ' minimum 100-foot flow path necessary for dispersion. The lots in this area will utilize a joint- use driveway and have its runoff conveyed to the back of the lots before being dispersed through the open space tract to the east. The individual lots will also have their runoff ' dispersed for a minimum of 100-feet through the open space tract to the east. The southwestern tract will also be fully dispersed. Runoff in this area flows both to the east ' and west, however all of the runoff drains to Puget Sound to the West. The road system will be dispersed for a minimum of 100-feet to the east before exiting the Site. In addition, lots 2-5 will also have its runoff dispersed in this area to the east. The flow paths for the Road System ' will be combined with individual lots 2-5, but will not be concentrated in excess of the requirements listed in the DOE Manual. The remaining lots 1 and 6-8 will be fully dispersed through 100-minimum flow paths to the west before exiting the Site. Each threshold discharge area that is proposed to meet the requirements of "Full Dispersion" has been evaluated to ensure that the 35% total impervious area is not exceeded ' The northwestern cluster will utilize combinations of drainage systems. A small portion to the north flows to the east and includes lots 29-32. These lots and the portion of the road system ' serving them will be fully dispersed through the open space tract separating the lots from East Ludlow Ridge Road. A 100-foot minimum flow path will be provided. Lot 3-18 will be fully dispersed through 100-foot minimum flow paths to the north and west before its runoff ' continues towards Puget Sound. Lots 19-28 and the road system serving those lots will be collected by a roadside ditch and conveyed to a stormwater tract located at the low point between lots 16 and 17. This runoff will then be treated through a Biofiltration swale before being tight-lined down to Puget Sound. The remaining portion of the road system that drains to the east will be dispersed through a series of dispersion trenches located in the open space ' ©2008 D.R.STRONG Consulting Engineers Inc. 23 Tale Point Full Drainage Report Jefferson County,Washington I Itract to the south. Runoff generated by lots 1 and 2 near the shoreline will connect to the tight- line pipe serving the upper lots and directly discharge to Puget Sound. I Offsite Improvements IEast Ludlow Ridge Road connects to Paradise Bay Road through an access easement that crosses parcel number 821221001, which is not included as part of this project. This parcel is I approximately 15.18 acres in size. The Project proposes to realign the entrance to meet current AASHTO requirements for alignment and sight distances along East Ludlow Ridge Road. This will result in the abandonment of the existing road up to the Project boundary and I replacing it by filling and crossing the existing Type NS stream with approximately 9,830 SF of new impervious area, and another 2,750 SF in the right of way to connect to Paradise Bay Road. This area has its own threshold discharge area and the new impervious area I represents only 1.48% of the threshold area. Therefore, this improvement is eligible for full dispersion. The portions of the road system that crosses the Ns Stream will have it's runoff conveyed north before being dispersed through the natural vegetation via a controlled I dispersion trench. The additional 2,750 SF of impervious area within Paradise Bay Road will also be conveyed back to an area within the parcel to be fully dispersed. This realigned section of East Ludlow Ridge Road will replace the existing Road connection to Paradise Bay I Road. The Site fronts approximately 1,250 feet of Paradise Bay Road on both sides at its southwest I corner. At this time it is unknown what the required improvements for the frontage will be. Hydrological analysis for this area will be conducted upon further discussion and direction with the County and the Developer. I I I I I I I I ©2008 D.R.STRONG Consulting Engineers Inc. 24 Tala Point Full Drainage Report Jefferson County,Washington I IFIGURE 5 DEVELOPED BASIN MAP I I I I I I I I I I I I I I I ' t I ©2008 D.R.STRONG Consulting Engineers Inc. 25 Tala Point Full Drainage Report Jefferson County,Washington Q dVW NISV9 ODdO19A O O N m4o� i.- (r) o�� E 7,.. m m W di Q �2 aa ainm $ p ii .6 — 0,1 . r!kt-9 ' 5 0 z ffi z ,,,, g E g E 6 .INIOd H HI 68 w w o R I., ,.: .4" ...),. z ww fi ocp Wt Z#resI`M W 0 tv,0,. ,. „,,,,,\, . • _ ,- V;•'• ( {-""1,< \ ' '1 • 't,(ilitUtf•:, 2,"3, V t 0 :':f 'ci b- ' l 118 ))(1/11( $ ''' OVI., : pop =j \\\\ . . slj �` a c / w f x., 'Me .'y V1 ) i, , Q Z t,� F r•\ , \ .--,r(---, ri , J ��E d p p Q . .,. 1,,,,,jt)-:',1,\\,‘\\,,k\ ., /4‘,.._/7:\.1,41,•,. 4,„Aii-gv:55; .3- I 1/4\\\•\\<•\\,\:-\--, t fi i i \ \‘' k, \\t„,,:, /t�g � _ lig, \,, \\-\,:,...4";:,,i4'1/1 y\---4",;p4Pi, :,',A',,.‘vt; ki \ThH\ N ! °��'�`` �i� Y ��� ���}t/��'4•)\__ \\,,X tq� yl\ri)\,, \\:, , � )/ � i Il� \"y"l �yi. f=. 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'iV/4* Vff 1--;() ;4' '111 r ; VIlito,:" ' ly4 t f''''',414> m 6/-**0 ‘,('rii. \ ' - ' wA,/%/4 Ari ?ltrt,,, • If„ ,.. 1 - ft a vi&velr, , ''''1S‘kt 46411, ( rte N.:z\Na9,17 )i') ;( .c is, iteii v AT;4.°41%,-0 4. ;,,,,,11.;i:t.p...v \c41 •i .1'., R kr w'i : *Nei) li S§5'�' } ._ 40 17 \y 5 k :.t',e7� jt(t` �r ,.� } s3a : .1. �: IQN `�'='' � €, { pq,.d Y§ S� fj> `. °nom `r�, T 1 ,,. .4 3i? ,•-,;, 1.xa„."c' _...J•i- Wit' g , s . e ' SECTION V DETENTION/RETENTION ANALYSIS AND DESIGN Hydrological Analysis ' The portion of the northwestern cluster that is being point discharged to Puget Sound (Lots 19- 28 and its respective road system has been evaluated using the Western Washington Hydrology Modeling (WWHM) software version 3.0. In order to establish the necessary developed basin inflow hydrographs and required water quality calculations, this area was modeled utilizing simple pond design. WWHM Results Western Washington Hydrology Model PROJECT REPORT ' Project Name: default Site Address: City . Report Date : 12/18/2008 Gage : Port Angeles Data Start 1948/10/01 Data End 1993/09/30 Precip Scale: 0.80 WWHM3 Version: I PREDEVELOPED LAND USE Name Basin 1 Bypass: No GroundWater: No Pervious Land Use Acres C, Forest, Mod 21.98 Impervious Land Use Acres 1 Element Flows To: Surface Interflow Groundwater 1 Name Basin 1 Bypass: No GroundWater: No t ©2008 D.R.STRONG Consulting Engineers Inc. 26 Tala Point Full Drainage Report Jefferson County,Washington I I Pervious Land Use Acres C, Forest, Mod 9.27 111 C, Lawn, Mod 11.12 Impervious Land Use Acres Il ROADS FLAT 1.59 I Element Flows To: Surface Interflow Groundwater Vault 1, Vault 1, PName Vault 1 Width : 129.30232132487 ft. Length : 129.30232132487 ft. Depth: 7ft. Discharge Structure Riser Height: 6 ft. I Riser Diameter: 18 in. NotchType Rectangular Notch Width : 0. 035 ft. I Notch Height: 2.526 ft. Orifice 1 Diameter: 0. 853 in. Elevation: 0 ft. Element Flows To: IOutlet 1 Outlet 2 I Vault Hydraulic Table I Stage(ft) Area(acr) Volume(acr-ft) Dschrg(cfs) Infilt(cfs) 0.000 0.384 0.000 0. 000 0. 000 0.078 0.384 0. 030 0. 005 0.000 0. 156 0.384 0. 060 0. 008 0. 000 0.233 0.384 0.090 0.009 0. 000 0.311 0.384 0.119 0.011 0. 000 0. 389 0.384 0. 149 0. 012 0.000 I 0.467 0.384 0. 179 0. 013 0.014 0.000 0.544 0.384 0.209 0. 000 0. 622 0.384 0.239 0.015 0.000 I 0.700 0.384 0.269 0. 016 0.000 0.778 0.384 0.299 0. 017 0. 000 0. 856 0.384 0.328 0. 018 0. 000 0. 933 0.384 0.358 0. 018 0.000 I 1.011 0.384 0. 388 0. 019 0. 000 1.089 0.384 0. 418 0. 020 0. 000 1. 167 0.384 0.448 0.021 0. 000 I 1.244 0.384 0.478 0. 021 0.000 1.322 0.384 0. 507 0. 022 0.000 1. 400 0.384 0.537 0. 023 0. 000 I ©2008 D.R.STRONG Consulting Engineers Inc. 27 Tale Point Full Drainage Report Jefferson County,Washington I1.478 0.384 0.567 0.023 0.000 1.556 0.384 0.597 0.024 0. 000 I 1. 633 0.384 0. 627 0. 657 0.024 0. 000 1.711 0.384 0.025 0.000 1.789 0.384 0. 687 0.026 0. 000 1.867 0.384 0.716 0.026 0.000 I 1.944 0.384 0.746 0.027 0.000 2. 022 0.384 0.776 0.027 0.000 2. 100 0.384 0. 806 0.028 0. 000 I 2.178 0.384 0.836 0.028 0.029 0.000 2.256 0.384 0.866 0.000 2.333 0.384 0.896 0.029 0. 000 2.411 0.384 0. 925 0.030 0. 000 I 2. 489 0.384 0. 955 0.030 0. 000 2.567 0.384 0. 985 0.031 0.000 2. 644 0.384 1.015 0. 031 0.000 I 2.722 0.384 1.045 0.032 0. 000 2.800 0.384 1.075 0.032 0. 000 2.878 0.384 1.105 0.032 0.000 I 2. 956 0.384 1. 134 0.033 0.033 0.000 3.033 0.384 1.164 0.000 3.111 0.384 1.194 0.034 0.000 3.189 0.384 1.224 0.034 0. 000 I 3.267 0.384 1.254 0.035 0.000 3.344 0.384 1.284 0.035 0.000 3. 422 0.384 1.314 0.035 0.000 I 3.500 0.384 1.343 0.036 0.040 0. 000 3.578 0.384 1.373 0. 000 3. 656 0.384 1.403 0.045 0.000 I 3.733 0.384 1.433 0.052 0.059 0.000 3. 811 0.384 1.463 0.000 3.889 0.384 1.493 0.066 0.000 3. 967 0.384 1.522 0.074 0.000 I 4.044 0.384 1.552 0.083 0.000 4.122 0.384 1.582 0.092 0.000 4.200 0.384 1. 612 0.101 0.000 I 4.278 0.384 1. 642 0.110 0. 000 4 .356 0.384 1. 672 0.119 0.000 4.433 0.384 1.702 0. 129 0.000 4.511 0.384 1.731 0.139 0.000 I 4 .589 0.384 1.761 0.151 0.000 4.667 0.384 1.791 0.163 0.000 4.744 0.384 1.821 0.175 0.000 I 4.822 0.384 1.851 0.188 0.000 4 .900 0.384 1.881 0.201 0.000 4 . 978 0.384 1. 911 0.215 0. 000 I 5.056 0.384 1. 940 0.228 0.243 0. 000 5.133 0.384 1.970 0.000 5.211 0.384 2.000 0.257 0.000 5.289 0.384 2.030 0.272 0.000 I5.367 0.384 2.060 0.287 0.000 5. 444 0.384 2.090 0.302 0.000 5.522 0.384 2.120 0.318 0.000 I 5. 600 0.384 2.149 0.334 0.351 0.000 5. 678 0.384 2.179 0. 000 5.756 0.384 2.209 0.367 0.000 I ©2008 D.R.STRONG Consulting Engineers Inc. 28 Tala Point Full Drainage Report Jefferson County,Washington I 5. 833 0. 384 2.239 0. 384 0.000 5. 911 0.384 2.269 0. 401 0. 000 I 5. 989 0. 384 2.299 0. 419 0.000 6.067 0.384 2. 328 0. 673 0.000 6. 144 0. 384 2.358 1.224 0.000 6.222 0. 384 2. 388 1. 952 0.000 6.300 0.384 2.418 2. 823 0.000 6.378 0.384 2.448 3.815 0.000 6. 456 0.384 2. 478 4 . 915 0.000 I 6. 533 0.384 2.508 6. 113 0. 000 6. 611 0. 384 2. 537 7. 402 0. 000 6. 689 0.384 2.567 8.776 0. 000 I 6.767 0.384 2.597 10.23 11.76 0.000 6. 844 0.384 2. 627 0.000 6. 922 0.384 2. 657 13.36 0.000 7. 000 0.384 2. 687 15. 03 0.000 I 7. 078 0.384 2.717 16.77 0.000 7. 156 0.000 0.000 18.57 0. 000 1 MITIGATED LAND USE IANALYSIS RESULTS I Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.05581 I 5 year 0.131183 10 year 0.210944 25 year 0. 357787 50 year 0.509473 I 100 year 0.70592 Flow Frequency Return Periods for Mitigated. POC #1 I Return Period 2 year Flow(cfs) 0. 05581 5 year 0. 131183 10 year 0.210944 I 25 year 0. 357787 50 year 0. 509473 I 100 year 0.70592 Yearly Peaks for Predeveloped and Mitigated. POC #1 I Year 1950 Predeveloped Mitigated 0.040 0. 040 1951 0.117 0. 117 I 1952 0.139 0.139 1953 0.013 0.013 1954 0. 030 0. 030 1955 0.435 0. 435 I 1956 0.085 0.085 1957 0.043 0.043 1958 0. 033 0.033 I ©2008 D.R.STRONG Consulting Engineers Inc. 29 Tala Point Full Drainage Report Jefferson County,Washington I 1959 0.022 0.022 1960 0.082 0. 082 I 1961 0.067 0. 193 0. 067 1962 0. 193 1963 0. 016 0. 016 1964 0.028 0.028 I1965 0.067 0. 067 1966 0.035 0. 035 1967 0. 031 0.031 I 1968 0.219 0.026 0.219 1969 0. 026 1970 0. 023 0.023 I 1971 0. 022 0.031 0.022 1972 0.031 1973 0.183 0. 183 1974 0. 036 0. 036 I 1975 0.032 0.032 1976 0.035 0.035 1977 0.035 0. 035 I 1978 0. 025 0.016 0.025 1979 0. 016 1980 0.016 0. 016 1981 0.255 0.255 I 1982 0. 130 0.130 1983 0. 199 0. 199 1984 0.184 0. 184 I 1985 0.030 0.030 1986 0.103 0. 103 1987 0.394 0.394 I 1988 0.084 0.084 1989 0.032 0. 032 1990 0.031 0. 031 1991 0. 110 0.110 I 1992 0.316 0.316 1993 0.233 0.233 1994 0. 022 0. 022 I Ranked Yearly Peaks for Predeveloped and Mitigated. POC #1 I Rank Predeveloped 0.4350 Mitigated 1 0.4350 2 0.3939 0.3939 3 0.3161 0.3161 I 4 0.2551 0.2551 5 0.2327 0.2327 6 0.2193 0.2193 I 8 0.1993 0. 1925 0. 1993 8 0. 1925 9 0.1835 0.1835 10 0. 1831 0. 1831 I 11 0.1388 0. 1388 12 0.1304 0.1304 13 0.1166 0. 1166 I 14 0.1104 0. 1104 15 0.1031 0. 1031 16 0.0854 0.0854 I ©2008 D.R.STRONG Consulting Engineers Inc. 30 Tala Point Full Drainage Report Jefferson County,Washington II I17 0.0842 0.0842 18 0.0818 0. 0818 II 19 0.0675 0.0675 20 0.0669 0.0669 21 0.0430 0.0430 22 0.0396 0.0396 I 23 0. 0362 0.0362 24 0.0351 0.0351 25 0.0350 0.0350 II 26 0.0349 0.0349 27 0.0327 0. 0327 28 0.0325 0.0325 29 0.0319 0.0319 II 30 0.0314 0.0314 31 0.0313 0.0313 32 0.0312 0.0312 I 33 0.0300 0.0300 34 0.0299 0.0299 35 0.0281 0.0281 I 36 37 0.0263 0.0263 0.0245 0.0245 38 0.0231 0.0231 39 0.0225 0.0225 II 40 0.0220 0.0220 41 0.0219 0.0219 42 0.0164 0.0164 I 43 0.0163 0.0163 44 0.0160 0.0160 45 0.0129 0.0129 II POC #1 The Facility PASSED I The Facility PASSED. I Flow(CFS) Predev Dev Percentage Pass/Fail 0.0279 5617 0 0 Pass 0.0328 4173 0 0 Pass 0.0376 3217 0 0 Pass 11 0.0425 2686 0 0 Pass 0.0474 2267 0 0 Pass 0.0522 1888 0 0 Pass II 0.0571 1551 0 0 Pass 0.0620 1303 0 0 Pass 0.0668 1096 0 0 Pass II 0.0717 917 0 0 Pass 0.0765 761 0 0 Pass 0.0814 642 0 0 Pass 0.0863 564 0 0 Pass II 0.0911 486 0 0 Pass 0.0960 416 0 0 Pass 0.1009 363 0 0 Pass I'i I 0.1057 312 0 0 Pass 0.1106 273 0 0 Pass 0.1155 231 0 0 Pass I ©2008 D.R.STRONG Consulting Engineers Inc. 31 Tala Point Full Drainage Report Jefferson County,Washington II II0.1203 192 0 0 Pass 0.1252 148 0 0 Pass II 0. 1301 122 0 0 Pass 0.1349 105 0 0 Pass 0. 1398 87 0 0 Pass 0.1446 76 0 0 Pass II 0.1495 66 0 0 Pass 0.1544 61 0 0 Pass 0.1592 53 0 0 Pass I 0.1641 49 0 0 Pass 0. 1690 44 0 0 Pass 0.1738 40 0 0 Pass 0. 1787 37 0 0 Pass II 0.1836 35 0 0 Pass 0.1884 32 0 0 Pass 0.1933 30 0 0 Pass I 0.1982 28 0 0 Pass 0.2030 26 0 0 Pass 0.2079 25 0 0 Pass I 0.2127 22 0 0 Pass 0.2176 21 0 0 Pass 0.2225 20 0 0 Pass 0.2273 19 0 0 Pass II 0.2322 17 0 0 Pass 0.2371 17 0 0 Pass 0.2419 15 0 0 Pass II 0.2468 14 0 0 Pass 0.2517 11 0 0 Pass 0.2565 11 0 0 Pass II 0.2614 10 0 0 Pass 0.2663 9 0 0 Pass 0.2711 9 0 0 Pass 0.2760 8 0 0 Pass I 0.2808 1 0 0 Pass 0.2857 0 0 0 Pass 0.2906 0 0 0 Pass I 0.2954 0 0 0 Pass 0.3003 0 0 0 Pass 0.3052 0 0 0 Pass 0.3100 0 0 0 Pass I 0.3149 0 0 0 Pass 0.3198 0 0 0 Pass 0.3246 0 0 0 Pass I 0.3295 0 0 0 Pass 0.3344 0 0 0 Pass 0.3392 0 0 0 Pass II 0.3441 0 0 0 Pass 0.3490 0 0 0 Pass 0.3538 0 0 0 Pass 0.3587 0 0 0 Pass II 0.3635 0 0 0 Pass 0.3684 0 0 0 Pass 0.3733 0 0 0 Pass I 0.3781 0 0 0 Pass 0.3830 0 0 0 Pass 0.3879 0 0 0 Pass I ©2008 D.R.STRONG Consulting Engineers Inc. 32 Tala Point Full Drainage Report Jefferson County,Washington II II 0.3927 0 0 0 Pass 0.3976 0 0 0 Pass II 0.4025 0 0 0 Pass 0.4073 0 0 0 Pass 0.4122 0 0 0 Pass 0.4171 0 0 0 Pass II 0.4219 0 0 0 Pass 0.4268 0 0 0 Pass 0.4316 0 0 0 Pass I 0.4365 0 0 0 Pass 0.4414 0 0 0 Pass 0.4462 0 0 0 Pass 0.4511 0 0 0 Pass I 0.4560 0 0 0 Pass 0.4608 0 0 0 Pass 0.4657 0 0 0 Pass ' 0. 4706 0 0 0 Pass 0.4754 0 0 0 Pass 0.4803 0 0 0 Pass I 0.4852 0 0 0 Pass 0.4900 0 0 0 Pass 0.4949 0 0 0 Pass 0.4997 0 0 0 Pass II 0.5046 0 0 0 Pass 0.5095 0 0 0 Pass I I Water Quality BMP Flow and Volume for POC 1. On-line facility volume: 0.2274 acre-feet On-line facility target flow: 0.01 cfs. Adjusted for 15 min: 0.1154 cfs. I Off-line facility target flow: 0.0497 cfs. Adjusted for 15 min: 0.0501 cfs. IThis program and accompanying documentation is provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by the user. Clear Creek I Solutions and the Washington State Department of Ecology disclaims all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions and/or the Washington State Department of Ecology be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of I business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions or the Washington State Department of Ecology has been advised of the possibility of such damages. I I I I ©2008 D.R.STRONG Consulting Engineers Inc. 33 Tala Point Full Drainage Report Jefferson County,Washington Water Quality Analysis The portion of the Northwestern Cluster (21.98 acres) that is not being fully dispersed will be ' collected and conveyed to a low point located between lots 16 and 17. A bio-swale will be designed to serve as the method of water quality before entering the discharge system and being conveyed to Puget Sound. The bioswale will be designed to meet the requirements of ' the 2005 DOE Manual Chapter 9 BMP T9.10 Basic Biofiltration. The WWHM software is incapable of developing water quality calculations without detention/retention evaluation, and ' defines in the software do not provide clear definitions of how the 15-minute flow rate is provided. Therefore, both WWHM and Santa Barbara Unit Hydrograph (SBUH) modeling software was utilized to generate the 6-month 24-hour Water Quality Storm. Since SBUH ' indicate a higher maximum peak-Q, the Swale was evaluated using that hydrograph as opposed to the WWHM 15-minute peak-Q, which is conservative. ' The DOE Manual Appendix I-B defines the Water Quality Design Storm as: A 24-hour storm with a 6-month return frequency (a.d.a. 6-month 24-hour storm). The 6-month 24-hour storm can be estimated as 72% of the 2-year 24-hour rainfall amount for areas in Western Washington. The 2-year storm even for this site based upon the isopluvial map located in the DOE Manual Appendix III-A indicate a 2-year storm produces 1.5 inches of runoff, of which 1.08 inches represents 72% of that amount. ' Biofiltration Swale Sizing Calculations and Hydrographs SPECIFY STORM OPTION: 1 ' S.C.S. TYPE-1A RAINFALL DISTRIBUTION ENTER: FREQ(YEAR) , DURATION(HOUR) , PRECIP (INCHES) 2, 24, 1. 08 ******************** S.C.S. TYPE-1A DISTRIBUTION ******************** ********* 2—YEAR 24—HOUR STORM **** 1.08" TOTAL PRECIP. ******** ENTER: A(PERV) , CN(PERV) , A(IMPERV) , CN(IMPERV) , TC FOR BASIN NO. 1 20.39, 81.50, 1.59, 98, 61.78 DATA PRINT—OUT: ' AREA(ACRES) PERVIOUS IMPERVIOUS TC(MINUTES) A CN A CN 22.0 20.4 81.5 1. 6 98.0 61. 8 PEAK—Q(CFS) T—PEAK(HRS) VOL(CU—FT) .25 12. 50 14951 I I ©2008 D.R. STRONG Consulting Engineers Inc. 34 Tala Point Full Drainage Report Jefferson County,Washington I ' Steps for sizing biofiltration swales per DOE Manual Volume V Chapter 9 Preliminary Steps P-1) 0.25 CFS P-2 ) S=2.0% P-3) (Per Table 9-3 and 9-4) Not applicable for equation tD-1) Depth = 4" D-2) Mannings N = 0.24 ' D-3) Trapezoidal D-4) Solve for b Q = Flow Rate (0.25) n = Manning's (0.24) Z = Trapezoidal Slope (3) s = Longitudinal Slope (0.0200 ft/ft) y = depth of flow (0.33) b = bottom of trapezoid (3.55) A = cross-sectional area (1.4967) T = top width of trapezoid (5.53) V = Velocity (.256) D =SBUH Peak/WWHM Peak WQ Flow Ratio per Figure 9.6a (1.6) L= Length (140 minimum) T = time (9 minimum) isolve for B�(2.5Qn/(1.49n1.67 s0.5 ))-Zy [(2.5(.25)(0.24))/(1.49(0.331.67))(0.020.5)] — 3(0.33) = 3.55 ' b 3.55 Solve for T T = b+2yZ 3.55+[2(.33)(3)]=5.53 T = 5.53 ' D-5) Solve for A A = by + Zy2 ' 3.55(.33) +3(.332)=1.4967 ft2 A = 1.4967ft2 D-6) Calculate V V = K(Q/A) 1.6(.24/1.4967) = .256 .256 < 1.0 = o.k. V=.256 ' D-7) Calculate L L = Vt(60 sec/min) .256(9)(60)=138.24 = use 140 feet L = 140 minimum ©2008 D.R.STRONG Consulting Engineers Inc. 35 Tala Point Full Drainage Report Jefferson County,Washington 1 1 Wetland Areas Protection All portions of the site located adjacent to any critical areas are located in areas utilizing "Full Dispersion" and providing a minimum of 100-feet of vegetative flow path before reaching any stream or wetland. A section of Tala Ridge Road that abuts the existing Category Ill and IV wetlands will have its runoff routed to a dispersion facility that will provide the 100-foot minimum flow path necessary prior to reaching the critical area at release rates not to exceed DOE requirements. 1 1 1 1 1 I I 1 1 1 1 1 1 ' ©2008 D.R.STRONG Consulting Engineers Inc. 36 Tala Point Full Drainage Report Jefferson County,Washington I ISECTION VI CONVEYANCE SYSTEM ANALYSIS AND DESIGN IThe 100- version storm runoff from the Site will be anal zed usin the KingCount Backwater y Y 9 Y IAnalysis Program version 5.30g at during the creation of the final Stormwater Site Plan after preliminary review and approval. I Onsite Conveyance The onsite stormwater conveyance systems will consist primarily of a series of culverts under the road system necessary to convey stormwater runoff to their respective dispersion systems. I The northwestern lot cluster will have a portion of its runoff directly discharged into Puget Sound through a 18-inch N-12 storm drain pipe for the portions through the lots, and a 12-inch High Density Polyethylene (HDPE) Pipe for the portions of runoff conveyed over the steep Islope areas. It is anticipated that the maximum runoff for a 100-year storm event will have a Q of about 9 cfs. Using Haestad Methods FlowMaster I version 3.43, a 18 pipe at 2% has a full-flow capacity of 16.09 cfs and a 12" pipe at 10% has a full flow capacity of 12.21 cfs. ioixl Haestad Methods FiowMa ter I version 3.43 I � gel.. " " �ucular Channel Mannings Equation Tala Point: y a Cenmentr Salve Far.. Diameter £t Uelocitg fps E Slape - ft 'ft Flow Areas£ Ptanning's nCritical'Slope ft/ft I Discharge cfs: Cg itical Depth ft ' .' Depth ft Fereent Ful3._ r Fronde Nicht,_ Full Capacity_ CES'„” efs ,> „q Enter (lorksheet Description ...,: �.m.::..., . . . ...,.a SF1> Hel <F2> Frim <P3> Calculator P Dn> Create Table <ESC> Exit F I ria De top fhd EX£ IF ' iQ XI Hae tad Methods FlowMaster I version 3.43 cular Channel Mann�ng's Equation Talc=Paint.:. I FG � Solve FaPT '--',,-kA',. �: s Diameter ft Flew".a.ty:_ '" f Slop F £t/ft 'Flew". . of a Mannings n x Critical Slope ft/ft rhrge cfs Critical Depth £t> D ft Percent PuLll "f F aFroude Number. I Full CapacitM cfs QMpX l* 94D. erns Enter'''?'t'—' he Roughne s.::fi •a.• - . (Fl> Hel. <F2> Print <F3> Calculator <F Dn> Create Viable <ESC> Exit I02008 D.R.STRONG Consulting Engineers Inc. 37 Tala Point Full Drainage Report Jefferson County,Washington I 1 BACKWATER TABLE To be created after Preliminary Plat review and approval. 1 1 1 i 1 1 1 1 i 1 1 1 1 1 1 1 ©2008 D.R.STRONG Consulting Engineers Inc. 38 Tala Point Full Drainage Report Jefferson County,Washington I APPENDIX A I OTHER REPORTS Geotechnical Engineers Report ZZA Terracon • Critical Areas Study Wiltermood Associates, Inc. I Bald Eagle Habitat Study Fleming Ecological Services Traffic Study Geri Reinart Groundwater Hydrological Analysis Bender Consulting, Inc. I I I I I I I I I I I I I I I ©2008 D.R.STRONG Consulting Engineers Inc. 39 Tala Point Full Drainage Report Jefferson County,Washington APPENDIX B STORMWATER POLLUTION PREVENTION PLAN The SWPPP Plan will be created after Preliminary Plat review and approval. I 1 I I 1 I ' ©2008 D.R.STRONG Consulting Engineers Inc. 40 Tala Point Full Drainage Report Jefferson County,Washington I IAPPENDIX C SOIL SURVEY INFORMATION (AS PROVIDED BY NRCS WEBSITE) ISoil Map—Jefferson County Area,Washington *83 LI 524000 524400 524800 525200 525600 026000 526400 47°56'a" 1 1 I 1 1 1 47°56'B" d' d # V 4."1/4,.„,--__,:„,,,,:„,-„,-,.,,„--„,,,,,,,,„,„„„-„-i„.-:- + 7v s..a a � ,,!- I .,Allaymennitiltit- d r t a `ha r• a a ., Mari'•�Ya t 4 j � P`I ilitiliiiitill.,i:',1 '1.,F`(:..4--;-:-',Z1,1'---7 ii-N ..r...,,,,..--- .0k:latal;%::;,i,itV-i.'•:::4111111111gilliiii:‘.;;!!!,;;;', 6ii n 6 „_, _.,,,,, .. ..., sowalt„,,,,-,.. •.6,,,„,,::,,,sylreltoorAtig,Neititsi* -PrI.Trmi''',' ', ' ‘-'' ' --'. d zs,:,, ---. ,/,,:ilr 14:41%1930s6t,..,,..40,14,_,.4#0,,,),. .,;*.t,:„}tz.,,z, ..::,. ,:::Afsgeoptarom,3:airi 2 s4.-.,-.,,,,,,4110,12,0 47°54'18" 524000 524400 524800 525200 525600 526000 526400 Map Seale:1.16600 it printed on A size(8.5"x 11")sheet I N Meters A 0 150 300 600 900 Feet 0 500 1,000 2,000 3,000 I USDA Natural Resources Web Soil Survey 2.1 12!16!2008 Conservation Service National Cooperative Soil Survey Page 1 of 3 MINI I ©2008 D.R.STRONG Consulting Engineers Inc. 41 Tala Point Full Drainage Report Jefferson County,Washington I I Soil Map—Jefferson County Area,Washington I MAP LEGEND MAP INFORMATION I Area or Interest(Axl) all very stony Spat Map Scale:1:16,300 i1 printed on A size(8.5"z 11")sheet. _� Area a In Brest 18011 .� Wet Spa The soil surveys that comprise your AOI were mapped at 1:20,000. sass y Other Please rely on the bar scale on each map sheet fa accurate map illij Soil Map Units measurements. Special Line Features Special Pant Features Gully Source of Map: Natural Resources Conservation Service Blowout Web Sal Survey URL: httpaiwebsoilsurvey.nres.usda.gov Short Steep Slope IIII ^ Coordinate System: UTM Zone 10N NAD83 ® Borrow Pit aner This product is generated from the USDA-NRCS certified data as of X Clay Spot Political Features the version date(s)listed below. e Closed DepressionI Cities - Sal Survey Area: Jefferson County Area,Washington >::: Gravel Pd Water Features Survey Area Data: Version 5,Sep 5,2007 Gravelly spot Oceans Date(s)aerial images were photographed: 7212006 O Landfill Streams and Canals The orthophoto or other base map on which the sal lines were k Lava Flow Transportation compiled and digitized probably differs from the background Rails imagery displayed on these maps.As a result,some minor shifting .1.. Marsh ar swamp a of map unit boundaries maybe evident. R. Mine o Quarry " Interstate Highways ® Miscellaneous Water US Routes p Perennial Water :V,-i- Major Roads II v Rock Outcrop } Saline Spot Sandy Spot - Severely Eroded Spa ¢ Sinkhole or a Slip of Sods Spa ▪ Spoil Area Lr Storey Spa I I USrb1 Natural Resources Web Sail Survey 2.1 12/16/2008 Conservation Service National Cooperative Soil Survey Page 2 of3 I I I I I I I I ©2008 D.R.STRONG Consulting Engineers Inc. 42 Tala Point Full Drainage Report Jefferson County,Washington I I Soil Map-Jefferson County Area,Washington IMap Unit Legend Jefferson County Area,Washington(WA631) Map Unit Symbol Map Unit Name Acres in AOl Percent of A01 I CfC Cassdary sandy loam,0 to 15 percent 148.8 10.8% slopes CfD Cassdary sandy loam,15 to 30 percent 47.5 3.5% slopes I CfE Cassdary sandy loam,30 to 50 percent 105.0 7.6% slopes CkC Cassolary-Kitsap complex,0 to 15 2.4 0.2% percent slopes I CkD Cassdary-Kitsap complex,15 to 30 53.6 3.9% percent slopes Co Coastal beaches 62.9 4.6% I KsD Kitsap gravelly loam,15 to 30 percemt 25.5 1.9% slopes KtC Kitsep silt loam.0 to 15 percent slopes 18.1 1.3% KtD Kitsap silt loam,15 to 30 percent slopes 8.9 0.6% I KtE SnC Kitsap silt loam,30 to 50 percent slopes 32.1 2.3% Sinclair gravelly sandy loam,0 to 15 64.4 4.7% percent slopes SnD Sinclair gravelly sandy loam,15 to 30 7.6 0.6% I StB percent slopes Swantown gravelly sandy loam,0 to 8 21.8 1.6% percent slopes WhC Whidbey gravelly sandy loam,0 to 15 220.5 16.1% I percent slopes Subtotals for Soil Survey Area 819.1 59.7% Totals for Area of Interest 1,373.1 100.0% I 1 I I IU DA Natural Resources Web Soil Survey 2.1 12/162008 Conservation Service National Cooperative Soil Survey Page 3 of 3 I I I ©2008 D.R.STRONG Consulting Engineers Inc. 43 Tala Point Full Drainage Report Jefferson County,Washington ' APPENDIX D ' OPERATIONS & MAINTENANCE MANUAL The 0 & M Manual will be created after Preliminary Plat review and approval 1 I I i I ©2008 D.R. STRONG Consulting Engineers Inc. 44 Tala Point Full Drainage Report Jefferson County,Washington I IAPPENDIX E IMPERVIOUS AREA BREAKDOWN I1. Impervious areas are based upon an overall impervious area average of 8,000 SF per lot, which is very conservative. Based on an 8,000 SF total, it is assumed that 5,000 SF will be I for structures and 3,000 SF will be for driveways, walks and other impervious surfaces. Therefore the structure area will be 5,000 SF x 54 lots. I 2. Lots 1-8 in the southwestern cluster and lots 1-2 of the northwestern cluster are on individual septic systems. These systems are approximated at 10,000 SF of disturbed area per lot. I3. Area disturbed for the community drainfield. I 4. Area disturbed for utility easement in the northwestern cluster serving the two shoreline lots. I5. Based on an average of 3,000 SF per lot x 54 lots. 6. Total area of onsite road system for full 60-foot easement. I7. Total area of all lots (2,573,273 SF) subtracting building and driveway areas (162,000+270,000 SF), individual drainfields (100,000 SF), and steep slope buffer areas Ilocated within the northwest and southwestern clusters (131,792 SF) PLUS the disturbed area for the bio-swale in the northwestern cluster (24,176). Note: lots 1-8 in the southwestern cluster and lots 3-18 in the northwestern cluster will have its runoff dispersed Ithrough a naturally vegetated portion of each lot which was not subtracted from the landscape area, therefore this number is conservative. I8. Total of driveways (162,000 SF), roads and shoulders (316,589 SF) subtracted by the area of existing pavement and shoulder currently within East Ludlow Ridge Road being widened Ias part of the development (40,000 SF). 9. Total area of impervious area and shoulder within East Ludlow Ridge Road from the Isouthern property line to the northern property line. I I I I ©2008 D.R.STRONG Consulting Engineers Inc. 45 Tala Point Full Drainage Report Jefferson County,Washington