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Home My WebLink AboutRS_ Technical Information Report_170621_v2Markup Summary Subject: Cloud+ Page Label: 34 Lock: Unlocked Status: Checkmark: Unchecked Author: Ian Fitz-James Date: 6/16/2017 9:44:38 AM Color: Depth: 1.06 Ian Fitz-James (2) Subject: Cloud+ Page Label: 49 Lock: Unlocked Status: Checkmark: Unchecked Author: Ian Fitz-James Date: 6/21/2017 2:55:48 PM Color: Depth: first cutoff should be less than or equal to 0% Subject: Text Box Page Label: 86 Lock: Unlocked Status: Checkmark: Unchecked Author: IFitz-James Date: 6/21/2017 3:16:57 PM Color: Depth: the city bond quantity worksheet has been updated to account for the recent sales tax increase and other miscellaneous items. please download it here: https://edocs.rentonwa.gov/Documents/0/edoc/883 098/Bond%20Quantity%20Worksheet.xlsx. confirm bond quantities with plan updates. IFitz-James (1) yed to the stormwater facility. break down the historic site conditions an – Historic Site Conditions – Thresho Total sf (ac)Impervioussf (ac) harge Area 46,236 (1.11) 0 harge Area 2,528 (0.06) 0 shold #2.A that 1.06 E-03 E-04 E-04 E-04 of Tolerance------- Base New %Change .017 0.018 1.8 .022 0.020 -11.4 .027 0.022 -17.6 .032 0.025 -20.1 first cutoff shouldbe less than orequal to 0% Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430‐7200 Date Prepared: Name:PE Registration No:Firm Name:Firm Address:Phone No. 6/1/2017Prepared by:FOR APPROVALProject Phase 1 Brandon Loucks50085Beyler Consulting LLC7602 Bridgeport Way W, STE D Lakewood, WA 98253‐301‐4157 SITE IMPROVEMENT BOND QUANTITY WORKSHEETPROJECT INFORMATION Engineer Stamp Required (all cost estimates must have original wet stamp and the city bond quantity worksheet has been updated to account for the recent sales taxincrease and other miscellaneous items. please download it here:https://edocs.rentonwa.gov/Documents/0/edoc/883098/Bond%20Quantity%20Worksheet.xlsx. confirm bond quantities with plan updates. BOUN SHORT PLAT SITE ADDRESS: 1024 Duvall Ave NE, Renton, Washington SECTION 10/TOWNSHIP 23 NORTH, RANGE 5 EAST, W.M. Technical Information Report U16-006297__ Associated Permit Number Prepared For: Warring Properties Contact: Socheat “Kent” Khnor 845 106th Ave, Suite 200 Bellevue, WA 98003 Date Prepared: November 21, 2016 Date Revised: May 30, 2017 Prepared By: Drew T. Young, P.E. Reviewed By: Brandon M. Loucks, P.E. Beyler Consulting LLC 7602 Bridgeport Way W, #3D Lakewood, WA 98499 253.301.4157 CONTACT phone: 253-301-4157 fax: 253-336-3950 info@beylerconsulting.com beylerconsulting.com LAKEWOOD OFFICE 7602 Bridgeport Way W #3D Lakewood, WA 98499 ISSAQUAH OFFICE 455 Rainier Blvd N Issaquah, WA 98027 Plan. Design. Manage. CIVIL & STRUCTURAL ENGINEERING | LAND SURVEYING | PLANNING PROJECT MANAGEMENT | FEASIBILITY | PERMIT EXPEDITING Page 1 Boun Short Plat TABLE OF CONTENTS I. PROJECT OVERVIEW ................................................................ 2 Project Description ...................................................................... 2 Figure 1. TIR Worksheet ............................................................ 4 Figure 2. Location Map .............................................................. 10 Figure 3. Drainage Basins, Subbasins, and Site Characteristics ....... 11 Figure 4. Soils Map ................................................................... 14 II. CONDITIONS AND REQUIREMENTS SUMMARY ....................... 15 III. OFFSITE ANALYSIS ................................................................ 20 3.1.1 Task 1 - Study Area Definition and Maps ......................... 20 3.1.2 Task 2 - Resource Review ............................................. 20 3.1.3 Task 3 - Field Inspection ............................................... 21 3.1.4 Task 4 - Drainage System Description and Problem Descriptions ............................................................................. 32 3.1.5 Task 5 - Mitigation of Existing or Potential Problems .......... 32 IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ................................................................................... 33 V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN ...................... 63 VI. SPECIAL REPORTS AND STUDIES ........................................... 67 VII. OTHER PERMITS ..................................................................... 67 VIII. CSWPPP ANALYSIS AND DESIGN ........................................... 67 IX. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT ................................................................................. 67 X. OPERATION AND MAINTENANCE MANUAL .............................. 67 XI. APPENDICES .......................................................................... 68 APPENDIX A – OFFSITE STUDY MAPS............................................... APPENDIX B – DOWNSTREAM SYSTEM TABLE AND MAPS ................... APPENDIX C – BOND QUANTITIES WORKSHEETS/COST DATA AND INVENTORY .................................................................................. APPENDIX D – GEOTECHNIAL REPORT ............................................. APPENDIX E – CSWPPP REPORT ...................................................... APPENDIX F – OPERATION AND MAINTENANCE WORKSHEETS ............ Page 2 Boun Short Plat I. PROJECT OVERVIEW Project Description The proponent of the Boun Short Plat proposes to subdivide an undeveloped parcel, with the exception of an abandoned shed building that is to be removed as part of this project, located in the City of Renton, King County Washington. The King County parcel number for the property is 102305-9139. The project parcel is approximately 57,677 sf, 1.32 acres in size. The parcel is zoned Residential 8 (R-8) according to the City of Renton Zoning Map effective as of July 1, 2015. The allowed density range in the R-8 zone is a minimum of 4.0 dwelling units per net acre (DUA) to a maximum of 8.0 DUA. The Boun Short Plat proposes to subdivide the current parcel into 7 single-family lots equating to a proposed density of 5.29 DUA. The proposed lots range in size from the smallest being 5,172 sf in size and the largest being 6,553 sf in size. A single tract will be created with this subdivision for the purpose of stormwater treatment and mitigation and open space area for the development. The remaining area will be dedicated to the City of Renton for public right-of-way use. The property is adjacent to Duvall Ave NE to the east, single family parcels to the south and north, and Chelan Ave NE to the west. The proposed project is keeping consistent with neighboring land use characteristics. The site will be accessed through two separate access points. The first access will be an extension of Chelan Place NE, an existing 20’ alleyway, from the south boundary to the north boundary of the project parcel. This access way will be developed into a 12’ paved alley within a 16’ wide right-of-way dedication which meets the current City of Renton street standards for alleys. An additional access point to Chelan Ave NE will be provided in the east to west direction through a 12’ paved alley within a 16’ public access and utilities easement. Half street frontage improvements will be included along the west boundary of the project site. Chelan Avenue NE will be improved to two separate variations of the current City of Renton Standards for Residential Access Streets. Starting from the south boundary of the project site, the east half of Chelan Avenue NE will be improved to provide a 15-foot travel lane, vertical curb and gutter, an 8-foot wide planter strip, and a 5-foot wide sidewalk for approximately 120 feet. At this point, the Residential Access Street will transition into a Limited Residential Access Street which consists of a 20-foot paved roadway, vertical curb and gutter, an 8-foot wide planter strip, and a 5-foot sidewalk. This road section will be constructed north until it reaches the north boundary line of the project. To incorporate these improvements, an 18’ right of way dedication will be necessary along a portion of the northwest boundary of the project parcel. An 18’ wide section of right-of-way north of the project site will not be improved as part of this project. As a condition of preliminary plat approval (LUA16-00124), a road standards modification will be submitted concurrently with the Utility Construction Permit to allow for the 18’ wide section of right-of-way to remain undeveloped. This project is subject to the 2009 King County Surface Water Design Manual (King Manual) and the City of Renton amendments to the Manual (Renton Manual). Per Figure 1.1.2.A of the Renton Manual, the Boun Short Plat project is subject to a full drainage review meeting core requirements #1 through #8 and special requirements #1 through #6. It has been determined that the site consists of two separate threshold discharges areas. Threshold Discharge Area #1 (West Basin) consists of a majority of the project site area that naturally discharges stormwater to the southwest corner of the parcel. Threshold Discharge Page 3 Boun Short Plat Area #2 (A-East Basin, B-North basin) consists of a small portion of land along the east boundary which naturally discharges stormwater east to an existing swale within Duvall Ave NE (TDA 2.A) and the 18’ wide panhandle section of land located north of the project site that naturally discharges stormwater to the northwest (TDA 2.B). A drainage adjustment, per Section 1.4 of the Renton Manual, is proposed to combine a portion of threshold discharge area #2.A with threshold discharge area #1. See section III and IV of this report for further details. Page 4 Boun Short Plat Figure 1. TIR Worksheet KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2009 Surface Water Design Manual 1/9/2009 1 Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner ________________________ Phone ______________________________ Address ____________________________ ____________________________________ Project Engineer ______________________ Company ___________________________ Phone ______________________________ Project Name _________________________ DDES Permit # ________________________ Location Township ______________ Range ________________ Section ________________ Site Address __________________________ _____________________________________ Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Landuse Services Subdivison / Short Subd. / UPD Building Services M/F / Commerical / SFR Clearing and Grading Right-of-Way Use Other _______________________ DFW HPA COE 404 DOE Dam Safety FEMA Floodplain COE Wetlands Other ________ Shoreline Management Structural Rockery/Vault/_____ ESA Section 7 Part 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review (circle): Date (include revision dates): Date of Final: Full / Targeted / Large Site ___________________ ___________________ ___________________ Type (circle one): Date (include revision dates): Date of Final: Full / Modified / Small Site __________________ __________________ __________________ Part 6 ADJUSTMENT APPROVALS Type (circle one): Standard / Complex / Preapplication / Experimental / Blanket Description: (include conditions in TIR Section 2) ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Date of Approval: ______________________ KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2009 Surface Water Design Manual 1/9/2009 2 Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: _______________________ Completion Date: _______________________ Describe: _________________________________ _________________________________________ _________________________________________ _________________________________________ _________________________________________ Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan : _________________________________ Special District Overlays: __________________________________________________________ Drainage Basin: ___________________________________ Stormwater Requirements: ________________________________________________________ Part 9 ONSITE AND ADJACENT SENSITIVE AREAS River/Stream _______________________ Lake _____________________________ Wetlands ___________________________ Closed Depression ___________________ Floodplain __________________________ Other ______________________________ ___________________________________ Steep Slope ______________________ Erosion Hazard ___________________ Landslide Hazard __________________ Coal Mine Hazard __________________ Seismic Hazard ___________________ Habitat Protection __________________ _________________________________ Part 10 SOILS Soil Type _________________ _________________ _________________ _________________ Slopes _________________ _________________ _________________ _________________ Erosion Potential _________________ _________________ _________________ _________________ High Groundwater Table (within 5 feet) Other ________________________ Sole Source Aquifer Seeps/Springs Additional Sheets Attached KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2009 Surface Water Design Manual 1/9/2009 3 Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE Core 2 – Offsite Analysis_________________ Sensitive/Critical Areas___________________ SEPA________________________________ Other_________________________________ _____________________________________ LIMITATION / SITE CONSTRAINT _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ Additional Sheets Attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: (name or description) Core Requirements (all 8 apply) Discharge at Natural Location Number of Natural Discharge Locations: Offsite Analysis Level: 1 / 2 / 3 dated:__________________ Flow Control (incl. facility summary sheet) Level: 1 / 2 / 3 or Exemption Number ____________ Small Site BMPs ___________________________________ Conveyance System Spill containment located at: _________________________ Erosion and Sediment Control ESC Site Supervisor: Contact Phone: After Hours Phone: Maintenance and Operation Responsibility: Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No Water Quality (include facility summary sheet) Type: Basic / Sens. Lake / Enhanced Basicm / Bog or Exemption No. ______________________ Landscape Management Plan: Yes / No Special Requirements (as applicable) Area Specific Drainage Requirements Type: CDA / SDO / MDP / BP / LMP / Shared Fac. / None Name: ________________________ Floodplain/Floodway Delineation Type: Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): ______________ Datum: Flood Protection Facilities Describe: Source Control (comm./industrial landuse) Describe landuse: Describe any structural controls: KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2009 Surface Water Design Manual 1/9/2009 4 Oil Control High-use Site: Yes / No Treatment BMP: ________________________________ Maintenance Agreement: Yes / No with whom? ____________________________________ Other Drainage Structures Describe: Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION Clearing Limits Cover Measures Perimeter Protection Traffic Area Stabilization Sediment Retention Surface Water Collection Dewatering Control Dust Control Flow Control MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION Stabilize Exposed Surfaces Remove and Restore Temporary ESC Facilities Clean and Remove All Silt and Debris, Ensure Operation of Permanent Facilities Flag Limits of SAO and open space preservation areas Other ______________________ Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch) Flow Control Type/Description Water Quality Type/Description Detention Infiltration Regional Facility Shared Facility Flow Control BMPs Other ________________ ________________ ________________ ________________ ________________ ________________ Biofiltration Wetpool Media Filtration Oil Control Spill Control Flow Control BMPs Other ________________ ________________ ________________ ________________ ________________ ________________ ________________ KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2009 Surface Water Design Manual 1/9/2009 5 Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS Drainage Easement Covenant Native Growth Protection Covenant Tract Other Cast in Place Vault Retaining Wall Rockery > 4’ High Structural on Steep Slope Other Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate. Signed/Date Page 10 Boun Short Plat Figure 2. Location Map Page 11 Boun Short Plat Figure 3. Drainage Basins, Subbasins, and Site Characteristics Figure 3.1 – Existing Conditions Map Figure 3.2 – Proposed Conditions Map MBMBSS~SHEET OFJOB NUMBERNO. DESCRIPTION INIT. DATE DRAWN BY:CHECKED BY:SCALE: HORZ:VERT: DATE:CIVIL & STRUCTURAL ENGINEERING | LAND SURVEYING | PLANNING PROJECT MANAGEMENT | FEASIBILITY | PERMIT EXPEDITING LAKEWOOD OFFICE7602 Bridgeport Way W #3D Lakewood, WA 98499 phone: 253-301-4157 fax: 253-336-3950 SNOQUALMIE OFFICE 35312 SE Center St Snoqualmie, WA 98065 phone: 425-392-8055 fax: 425-392-0108 beylerconsulting.com BEYLER CONSULTING Plan. Design. ManageFIGURE 3.11EXISTING BASIN MAP BOUN SHORT PLAT BASIN MAPS CITY OF RENTON,WASHINGTON16-2061A PORTION OF SECTION 10, TOWNSHIP 23 NORTH, 5 WEST, W.M.DUVALL AVE NE CHELAN AVE NE THRESHOLD DISCHARGEAREA #1(WEST BASIN)(46,236 SF)(1.06 ACRES)THRESHOLD DISCHARGEAREA #2.A(EAST BASIN)(8,771 SF)(5,760 SF TO BEDISCHARGED TO TDA1THROUGH DRAINAGEADJUSTMENT)(0.20 ACRES)BOUN SHORT PLATEXISTING BASIN MAPSCALE: 1" = 40'2040040THRESHOLD DISCHARGE AREA #2.B(NORTH BASIN)(2,669 SF)(0.061 ACRES)TO REMAIN UNDEVELOPED ANDDEDICATED TO CITY OF RENTONAS PUBLIC RIGHT OF WAY(MODIFICATION REQUEST #LUA16-000897, MOD)NATURAL DISCHARGELOCATION #1(EXISTING CATCH BASIN)NATURAL DISCHARGELOCATION #2.A(EXISTING SWALE)NATURAL DISCHARGELOCATION #2.B(SHEET FLOW TO NATIVEVEGETATION- NO APPARENTDISCHARGE LOCATION)BASIN AREA CALCULATIONSTHRESHOLD DISCHARGE AREA #1ONSITE (WEST BASIN)TOTAL BASIN AREA: 46,236 SF (1.06 ACRES)IMPERVIOUS (EXISTING SHED): 330 SFPERVIOUS (LAWN/GRASS): 45,906 SFOFFSITE (CHELAN AVE NE)TOTAL BASIN AREA: 2,528 SF (0.058 ACRES)PERVIOUS (LAWN/GRASS): 2,528 SFTHRESHOLD DISCHARGE AREA #2.AONSITE (EAST BASIN)TOTAL BASIN AREA:8,771 SF (0.20 ACRES)DRAINAGE ADJUSTMENT TO TDA #1: 5,760 SFPERVIOUS (LAWN/GRASS):3,011 SFTHRESHOLD DISCHARGE AREA #2.BONSITE (NORTH BASIN)TOTAL BASIN AREA: 2,669 SF (0.06 ACRES)IMPERVIOUS (GRAVEL DRIVEWAY): 789 SFPERVIOUS (LAWN/GRASS): 1,880 SFTHRESHOLD DISCHARGE AREA #1(OFFSITE)(2,528 SF)(0.058 ACRES) LOT 55,731 SFLOT 76,553 SFLOT 65,718 SFLOT 36,168 SFLOT 26,121 SFLOT 46,245 SFLOT 15,172 SFTRACT A7,277 SFMBMBSS~435434436 437437 437438438 438439439435434 SHEET OFJOB NUMBERNO. DESCRIPTION INIT. DATE DRAWN BY:CHECKED BY:SCALE: HORZ:VERT: DATE:CIVIL & STRUCTURAL ENGINEERING | LAND SURVEYING | PLANNING PROJECT MANAGEMENT | FEASIBILITY | PERMIT EXPEDITING LAKEWOOD OFFICE7602 Bridgeport Way W #3D Lakewood, WA 98499 phone: 253-301-4157 fax: 253-336-3950 SNOQUALMIE OFFICE 35312 SE Center St Snoqualmie, WA 98065 phone: 425-392-8055 fax: 425-392-0108 beylerconsulting.com BEYLER CONSULTING Plan. Design. ManageFIGURE 3.21PROPOSED BASIN MAP BOUN SHORT PLAT BASIN MAPS CITY OF RENTON,WASHINGTON16-2061A PORTION OF SECTION 10, TOWNSHIP 23 NORTH, 5 WEST, W.M.DUVALL AVE NE CHELAN AVE NE THRESHOLDDISCHARGE AREA #1(WEST BASIN)(48,397 SF)(1.11 ACRES)BOUN SHORT PLATPROPOSED BASIN MAPSCALE: 1" = 40'2040040THRESHOLD DISCHARGE AREA #2.B(NORTH BASIN)(2,669 SF)(0.061 ACRES)TO REMAIN UNDEVELOPED ANDDEDICATED TO CITY OF RENTONAS PUBLIC RIGHT OF WAY(MODIFICATION REQUEST #LUA16-000897. MOD)NATURAL DISCHARGELOCATION #1(RELOCATED CATCHBASIN)NATURAL DISCHARGELOCATION #2.A(EXISTING SWALE)THRESHOLD DISCHARGEAREA #2.A(EAST BASIN)(3,011 SF)(0.069 ACRES)BASIN AREA CALCULATIONSTHRESHOLD DISCHARGE AREA #1ONSITE (WEST BASIN)TOTAL BASIN AREA: 48,397 SF (1.11 ACRES)IMPERVIOUS (PGIS: ASPHALT ROAD): 4,485 SFIMPERVIOUS (PGIS: CONC. DRIVEWAYS):3,500 SF*IMPERVIOUS (PGIS: GRAVEL ACCESS ROAD): 535 SFIMPERVIOUS (ROOFTOPS): 19,113 SF*PERVIOUS (LAWN/GRASS): 20,764 SF*SEE RESTRICTED FOOTPRINT TABLE FOR LOT AREABREAKDOWN CALCULATIONSONSITE (VAULT BY-PASS)TOTAL BASIN AREA: 3,599 SF (0.083 ACRES)IMPERVIOUS (PGIS: ASPHALT/SWALK): 1,904 SFPERVIOUS (PLANTER STRIP/LAWN): 1,695 SFOFFSITE (VAULT BY-PASS)TOTAL BASIN AREA: 2,528 SF (0.058 ACRES)IMPERVIOUS (PGIS: ASPHALT): 2,050 SFPERVIOUS (PLANTER STRIP): 478 SFVAULT SIZING CALCULATIONS:TO DETENTION/WQ VAULT:TOTAL IMPERVIOUS: 27,633 SF (0.6344 ACRES)TOTAL PERVIOUS: 20,765 SF (0.4767 ACRES)VAULT BYPASS AREA CALCULATIONS:TO BYPASS DETENTION/WQ VAULT:TOTAL IMPERVIOUS: 3,954 SF (0.09 ACRES)TOTAL PERVIOUS: 2,173 SF (0.05 ACRES)THRESHOLD DISCHARGE AREA #2.AONSITE (EAST BASIN)TOTAL BASIN AREA: 3,011 SF (0.069 ACRES)PERVIOUS (LAWN/LANDSCAPE BUFFER): 3,011 SFTHRESHOLD DISCHARGE AREA #2.BONSITE (NORTH BASIN)TOTAL BASIN AREA: 2,669 SF (0.06 ACRES)IMPERVIOUS (GRAVEL DRIVEWAY): 789 SFPERVIOUS (LAWN/GRASS): 1,880 SFNATURAL DISCHARGELOCATION #2.B(SHEET FLOW TO NATIVEVEGETATION- NO APPARENTDISCHARGE LOCATION)THRESHOLD DISCHARGE AREA #1(ONSITE- VAULT BYPASS)(3,599 SF)(0.083 ACRES)THRESHOLD DISCHARGE AREA #1(OFFSITE-VAULT BYPASS)(2,528 SF)(0.058 ACRES)RESTRICTED FOOTPRINT TABLE (PER C.2.9.2 2009 KCSWDM)FOR SITES/LOTS THAT ARE SMALLER THAN 22,000 SQUARE FEET, ANY RECORDED LIMIT ON TOTAL IMPERVIOUS SURFACE LESS THAN A NORM OF 4,000 SQUARE FEET OR THEMAXIMUM ALLOWED BY THE SITE/LOT'S ZONING, WHICHEVER IS SMALLER, QUALIFIES FOR A RESTRICTED FOOTPRINT CREDIT EQUAL TO THE DIFFERENCE IN SQUARE FOOTAGE.LOT #SIZE (SF)MAX. IMPERV.PER ZONING(65%) (SF)10% OF LOTAREAMAX.IMPERV.ALLOWED(SF)EST.DRIVEWAY(SF)EST. ROOFTOP(SF)LOT 15,1723,3625172,8455002,345LOT 26,1213,9796123,3675002,867LOT 36,1684,0096173,3835002,883LOT 46,2454,0596253,3765002,876LOT 55,7313,7255733,1525002,652LOT 65,7183,7175723,1455002,645LOT 76,5534,2596553,3455002,845TOTAL AREAS3,50019,1131 REVISED PER CITY REVIEW #1 DTY 5/19 Page 14 Boun Short Plat Figure 4. Soils Map Page 15 Boun Short Plat II. CONDITIONS AND REQUIREMENTS SUMMARY The Boun Short Plat, File No. LUA16-000124; SHPL-A, is APPROVED WITH CONDITIONS and subject to the following conditions: 1. The width of Lot 7 shall be increased to comply with the minimum 50-foot lot width requirement of the R-8 zone. 2. A demolition permit shall be obtained for the removal of the detached accessory structure, and all required inspections shall be completed prior to the recording of the short plat. 3. A detailed landscape plan shall be submitted at the time of Utility Construction Permit Review. The detailed landscape plan shall include an 8-foot wide landscaping strip between the curb and sidewalk along the full length of the Chelan Avenue NE and Duvall Avenue NE frontages or a modification request to reduce the landscape strip shall be submitted and approved in accordance with RMC 4-9-250D at the time of Utility Construction Permit Review. 4. A Final Tree Retention Plan shall be submitted at the time of Utility Construction Permit Review. The Final Tree Retention Plan shall include minimum 2-inch caliper replacement trees within the onsite 10-foot landscape strip. The Final Tree Retention Plan shall be submitted to the Current Planning Project Manager for review and approval. 5. A modification request shall be submitted and approved for the proposed waiver of frontage improvements along the 18-foot wide panhandle north of the project site. The modification request shall be submitted at the time of Utility Construction Permit Review. 6. Access for Lots 1-7 shall be provided via the alley (Chelan Place NE). The front façade of the houses to be constructed on Lots 1-4 shall Duvall Avenue NE and the front façade of the houses to be constructed on Lots 5-7 shall face Chelan Avenue NE. A note to this effect shall be recorded on the face of the Short Plat map. 7. The width of the alley shall be revised to comply with the City’s adopted street standards, or a modification to these standards shall be requested at the time of Utility Construction Permit Review. Page 16 Boun Short Plat Review of Eight Core Requirements and Six Special Requirements The following comments are a review of the Core and Special Requirements per the 2009 King County Surface Water Stormwater Manual with City of Renton Amendments (where applicable). Core Requirement No. 1 Discharge at the Natural Location Threshold Discharge Area #1 Under existing conditions, the site’s topography suggests that stromwater runoff within threshold discharge area #1 sheet flows to the southwest over densely vegetated land cover consisting of various types of grass and brush. Any accumulated runoff is allowed to overflow onto Chelan Ave NE into an existing catch basin near the southwest corner of the project parcel. Under developed conditions, stormwater will sheet flow over impervious surfaces and be collected within a closed conveyance system. Rooftop runoff will be directly tightlined to this conveyance system. The closed conveyance system will route stormwater to a combined water quality and detention vault. The proposed stormwater vault will ultimately discharge stormwater to the catch basin located in Chelan Avenue NE near the southwest corner of the project site, matching the current natural discharge location. Threshold Discharge Area #2-A Under existing conditions, threshold discharge area #2-A which is located along the east boundary of the project parcel allows stormwater to sheet flow towards an existing conveyance swale located along the west side of Duvall Ave NE. This swale flows north along the western portion of Duvall Avenue NE. Under developed conditions, a portion of threshold discharge area #2-A will be allowed to sheet flow towards Duvall Ave NE. Accumulated runoff will be allowed to sheet flow to the existing conveyance swale, meeting the natural discharged location of threshold discharge area #2-A. The remaining portion of threshold discharge area #2-A will sheet flow west towards the closed conveyance system of Threshold Discharge Area #1. This stormwater will be collected, mitigated and released at the natural discharge location of Threshold Discharge Area #1. A drainage has been submitted to the City of Renton at time of Utility Construction Permit Review and has been approved. Threshold Discharge Area #2-B Currently, there are no planned improvements to this TDA. Therefore, this requirement is not applicable at this time. Core Requirement No 2 Offsite Analysis The project proposes to discharge stormwater within both threshold discharge areas to the May Creek drainage basin. A Level 1 offsite analysis has been completed for each of the two threshold discharge areas. Further narrative of this analysis can be found in Section III of this report. Core Requirement No 3 Flow Control Flow Control Facility Analysis and Design has been broken into two parts, part 1: Threshold Discharge Area #1 discussing the threshold area tributary to proposed onsite vault system, and Threshold Discharge Area #2, discussing the north and east portions of the onsite and offsite tributary area and improvements. Please refer to the Basin Maps in Figure 3, depicting areas as described herein. Page 17 Boun Short Plat Threshold Discharge Area #1 Flow Control Facility (1.2.3.1.B): The proposed project is located within the Flow Control Duration Standard – Matching Forested Site Conditions area. This level of flow control requires new impervious and pervious surfaces, that are not fully dispersed, to flow to a flow control facility that matches the flow durations of predeveloped rates for forested (historic) site conditions over the range of flows extending from 50% of the 2-year up to the full 50-year flow. To satisfy this requirement, an underground detention vault is proposed to detain onsite runoff to historic flow control levels per Section 1.2.3.1.B. See Section IV of this report for forested site conditions flow control performance standards and detention analysis. Flow Control BMPs (1.2.3.2): In addition to flow control facility requirements, implementation of flow control BMPs as part of this “subdivision” project is incentive-based per Section 1.2.3.3 of the Renton Manual. However, if the applicant wishes to implement or make provision for implementation of BMPs as part of the subdivision project for purposes of receiving the BMP credits then the requirements outlined in Section 5.2.2.1 must be met depending on the site location of the proposed BMPs. Based on a site evaluation, it has been determined that dispersion and infiltration is infeasible based on proposed lot size and existing soil conditions. The applicant proposes to implement a restricted footprint for the seven (7) lots following section C.2.9.2 of the King Manual. See Part C of Section IV of this report for the Small Lot BMP performance standards and further analysis of the proposed BMPs. Flow Control Bypass (1.2.3.2.E): A flow control bypass facility per Section 1.2.3.2.E of the Renton Manual is also proposed. The project proposes to bypass a small amount of targeted onsite impervious area within Tract A which provides access to Chelan Ave NE as well as the proposed offsite improvements of Chelan Ave NE. The bypass of this target area is necessary due to grading constraints of the site. The onsite flow control facility was sized to incorporate a reduction in allowed flow release to match historic durations for 50% of the 2-year through 50-year peaks at the downstream point of compliance, Catch Basin 1. See Section IV for further detail. Threshold Discharge Area #2 (2-A & 2-B) Flow Control Facility (1.2.3.1.B): The proposed project is located within the Flow Control Duration Standard – Matching Forested (Historic) Site Conditions area. This is required unless an exception applies to the proposed site conditions. Per Section 1.2.3.1.B – Exemption #2 of the Renton Manual, the facility requirement in Flow Control Duration Standard Matching Forested Site Conditions Areas is waived for any threshold discharge area in which there is less than a 0.1 cfs difference in the sum of developed 100-year peak flows for those target surfaces subject to this requirement and the sum of forested (historic) site conditions 100-year peak flows for the same surface areas. The developed conditions for this Threshold Discharge Area do not exceed a 0.1 cfs difference in the sum of developed 100-year peak flows for those target surfaces subject to the flow control facility requirement and the sum of historic (forested) site conditions 100-year peak flows for the same surface areas. Thus, flow control is not required for this threshold discharge area per section 1.2.3.1.B of the Renton Manual. See Section IV of this report for details and a table of the target areas. Core Requirement No. 4 Conveyance System New pipes systems will be designed with sufficient capacity to convey and contain, at minimum, the 25-year peak flow. See Section V of this report for the conveyance analysis. Page 18 Boun Short Plat Core Requirement No. 5 Erosion and Sediment Control This development is expected to be constructed in a single phase. Please see Appendix E for the prepared CSWPPP, and sheets C2-C3 in the prepared Construction Plans. Core Requirement No. 6 Maintenance and Operations It is anticipated that the proposed stormwater system will be owned and operated by the City of Renton. Therefore, operations and maintenance recommendations can be made upon request by the City of Renton. Core Requirement No. 7 Financial Guarantees and Liability Financial guarantees can be made available to the City upon request. Core Requirement No. 8 Water Quality Water Quality Facility Analysis and Design has been broken into two parts, part 1: Threshold Discharge Area #1 discussing the threshold area tributary to proposed onsite vault system, and Threshold Discharge Area #2, discussing the north and east portions of the onsite and offsite tributary area and improvements. Please refer to the Basin Maps in Figure 3, depicting areas as described herein. Threshold Discharge Area #1 Treatment Facility (1.2.8) This TDA is located within a Basic Water Quality treatment area as designated by the City of Renton and is not subject to the requirements of Enhanced Water Quality as it is not a Commercial, Industrial or Multifamily land use or a road project with an expected average daily traffic (ADT) count of 7,500. The developed conditions of TDA #1 exceed the 5,000 sf of proposed pollution generating impervious (PGIS) surface area exemption per Section 1.2.8.1 of the Renton Manual. Therefore, the project proposes to satisfy the basic water quality treatment requirement through the use of an onsite combined detention/wetvault located near the southwest corner of the project parcel to provide treatment for onsite runoff. See Section IV of this report for further description of the treatment system. Untreated Discharge (Treatment Bypass) (1.2.8.2) This TDA proposes to bypass a small portion of the proposed onsite and the entire offsite target pollution-generating surface that would need to be pumped to be treated by the required water quality facility. Per Section 1.2.8.2 of the Renton Manual, the following criteria must be met; 1) treatment of the constrained area by filter strip, biofiltration, or a linear sand filter is not feasible, and a treatment trade as described above is not possible. 2) The untreated target surface is less than 5,000 square feet of new PGIS and is less than 5,000 square feet of new plus replaced PGIS on a redevelopment. 3) Any target PGPS within the area to be released untreated shall be addressed with a landscape management plan. The project proposes 4,022 sf of target PGIS which is less than the 5,000 sf threshold to allow for Untreated Bypass. See Section IV of this report for further description of the untreated discharge. Threshold Discharge Area #2 (2-A & 2-B) Treatment Facility (1.2.8) This TDA is located within a Basic Water Quality treatment area as designated by the City of Renton and is not subject to the requirements of Enhanced Water Quality as it is not a Commercial, Industrial or Multifamily land use or a road project with an expected average daily traffic (ADT) count of 7,500. The developed conditions of TDA #2 do not exceed the 5,000 sf of proposed pollution generating impervious (PGIS) surface area exemption per Page 19 Boun Short Plat Section 1.2.8.1 of the Renton Manual. Therefore, a treatment facility is not required within threshold discharge area #2. Special Requirement No. 1 Other Adopted Area-Specific Requirements This project is not in a designated Critical Drainage Area. This special requirement is not applicable. Special Requirement No. 2 Flood Hazard Area Delineation The project does not contain or is not adjacent to a flood hazard area for a river, stream, lake, wetland, closed depression, or marine shoreline that is within the 100-year floodplain according to King County and FEMA. Special Requirement No. 3 Flood Protection Facilities This project does not rely on any flood protection facility such as a levee or revetment nor will construct a new flood protection facility. Special Requirement No. 4 Source Control This project does not require a commercial building or commercial site development permit. This special requirement is not applicable. Special Requirement No. 5 Oil Control This project is not defined as a high-use site nor is a redevelopment project proposing $100,000 or more of improvements to an existing high-use site. This special requirement is not applicable. Special Requirement No. 6 Aquifer Protection Area This project is not in a designated Aquifer Protection Area (APA). This special requirement is not applicable. Page 20 Boun Short Plat III. OFFSITE ANALYSIS An offsite analysis report has been prepared per Section 1.2.2, Core Requirement #2. This is to identify and evaluate offsite flooding, erosion, and water quality problems that may be created or aggravated by the proposed project. The primary component of this offsite analysis report is the downstream analysis. The second component of the report is to evaluate the upstream drainage system to verify that significant flooding and erosion impact will not occur as a result of the project. 3.1 DOWNSTREAM ANALYSIS The following Level 1 downstream analysis is a review of the drainage system up to a mile downstream of the site. The four tasks outlined under this review are: Task 1 – Define and map the study area Task 2 – Review all available information on the study area Task 3 - Field inspect the study area Task 4 - Drainage System Description and Problem Descriptions Task 5 – Mitigation of Existing or Potential Problems 3.1.1 Task 1 - Study Area Definition and Maps The project is located in the May Creek Drainage Sub-Basin within the Lake Washington/Cedar River Watershed. The drainage study area is approximately a mile-long path encompassing the site's downstream corridor. See Appendix A for maps of the basic study area. The site is currently unimproved, with the exception of an abandoned shed, surrounded by single family residential uses on all sides. 3.1.2 Task 2 - Resource Review The following resources have been reviewed for the downstream analysis. This is a review of available information on the downstream area at least a mile downstream. Sources include the City of Renton GIS maps, King County GIS maps, and geotechnical studies. Adopted Basin Plan  The site is located in the May Creek Drainage Sub-Basin within the Cedar River/Lake Washington Watershed (WRIA Cedar Sammamish (8)) Sensitive Area (See Appendix A for Sensitive Area Maps)  Erosion- None Mapped  Seismic – None Mapped  Landslide – None Mapped  Coal Mine – None Mapped  Streams and Wetlands Map – None Mapped  Susceptible to Groundwater Contamination – None Mapped  100-year flood plain – According to King County iMAP and the FEMA Flood Maps, the 100-year flood plain is not located near the project property. Drainage Complaints and Studies King County –Relevant DNRP drainage complaints within 1 mile of the downstream corridor of each threshold discharge area within the last 10 years were searched. TDA #1 There are currently no open complaints within the downstream corridor nor are there any relevant drainage complaints that were made within Page 21 Boun Short Plat the last 10 years. Going beyond a Level 1 analysis (within the last 15 years), a single complaint pertaining specifically to a water quality cross connection was made in regards to the regional stormwater pond in 2004. See Appendix A for a drainage complaint map of the downstream corridor. TDA #2 There are currently no open complaints within the downstream corridor nor are there any relevant drainage complaints that were made within the last 10 years. Going beyond a Level 1 analysis (within the last 15 years), a single complaint was made in 2003 in regards to a potential septic tank dumping that was leaching into the roadside swale along Duvall Ave NE, just north of the site. See Appendix A for a drainage complaint map of the downstream corridor. 3.1.3 Task 3 - Field Inspection A site visit was performed on July 18, 2016 for the purpose of analyzing the proposed project site and its upstream and downstream corridor. The weather and conditions were light rain and cloudy. A description of the drainage path is described below. See Appendix B for downstream reach locations. THRESHOLD DISCHARGE AREA #1 (West Basin) Upstream The subject site sits on a high point with very little runoff crossing the site from adjacent properties. The site’s topography suggests that stormwater runoff from the site is divided and sheets flows to the southwest and to the northeast. The westerly portion of the site drains to the southwest into an existing catch basin within public right of way (Chelan Ave NE). Downstream Runoff contributing to the downstream corridor from the project site consists of the generated runoff from the improved roadway and rooftop of the project site. The following is a discussion of the downstream corridor from threshold discharge area #1’s natural discharge location. See Appendix B for a Summary of each reach including: pipe size, length, and material as well as a map of each reach’s location. Downstream Legend - Surface Flow Arrow - Closed Conveyance Flow Arrow - Closed Conveyance Flow Arrow (Tributary) Page 22 Boun Short Plat Reach 1 0’ The runoff generated from the project parcel sheet flows southeast and is collected within a Type 1 Catch Basin (Facility ID# 178992) within Chelan Ave NE. Photo 1: Site topography facing northeast from Chelan Ave NE towards Project Site. Reach 2 0’ – 31’ Stormwater is collected within an existing Type 1 Catch Basin (Facility ID# 178992) and conveyed west within a 12-inch CPEP Storm Main sloped at 3.21% (R-332511). At time of site visit, the pipe did not seem to be flowing at capacity nor were flooding problems observed. Photo 2: Facing North on Chelan Ave NE. Stormwater flows south within closed conveyance system. Project Site Ex. CB - Type 1 ID: 178992 Ex. CB - Type 1 ID: 178992 Ex. CB - Type 1 ID: 116933 N Page 23 Boun Short Plat Reach 3 31’ – 180’ Stormwater is collected within an existing Type 1 Catch Basin (Facility ID# 116931) and conveyed southwest within a 12-inch CPEP Storm Main sloped at 0.52% (R-332511). At time of site visit, the pipe did not seem to be flowing at capacity nor were flooding problems observed. Photo 3: Facing northwest on Chelan Ave NE. Stormwater flows southwest within closed conveyance system. Reach 4 180’ – 275’ Stormwater is collected within an existing Type 2-54” Catch Basin (Facility ID# 175753) and conveyed west within a 60-inch CMP WQ Tank (R-332511). This WQ facility is privately owned and operated. Photo 4: Facing north on NE 10th Street. Stormwater flows west within closed conveyance system/WQ Facility. Ex. CB - Type 1 ID: 116931 N Ex. WQ Facility ID: 175753 Page 24 Boun Short Plat Reach 5 275’ – 395’ Stormwater is discharged to an existing Type 2 Catch Basin (Facility ID# 116930) and conveyed west within a 12-inch of unknown material storm main (R-332511). It should be noted that per as-built R-332511, the storm main connection is incorrectly shown to connect to the existing sanitary sewer within NE 10th Street. Photo 5: Facing West on NE 10th Street. Stormwater flows west within closed conveyance system. Reach 6 395’ – 477’ Stormwater is collected within a Type 2 Catch Basin (Facility ID# 116927) and conveyed north within a 12-inch CPEP Storm Main (D-22661A) sloped at 4.86%. This portion of pipe discharges into a regional stormwater facility which was developed as part of the NE 10th Street/Anacortes Ave NE Detention Pond and Storm System Improvement Project. Photo 6: Facing West on NE 10th Street. Stormwater is collected within Type II Catch Basin and conveyed north within closed conveyance system. Ex. CB - Type 2 ID: 116930 Ex. CB - Type 2 ID: 116930 Page 25 Boun Short Plat Reach 7 477’ – 825’ Stormwater is detained within a combined water quality and detention pond. Stormwater is then released at a controlled flow rate from an existing Type II-54” Catch Basin (Facility ID# 115504) and conveyed south within an 18- inch CPEP Storm Main (D-22661A) sloped at 0.20%. Stormwater is collected within a Type 2-48” Catch Basin (Facility ID# 115505) and conveyed southwest within an 18-inch CPEP Storm Main (D-22661A) sloped at 0.20%. From this location, stormwater is convey back into NE 10th Street public right of way to a Type 2-48” Catch Basin (Facility ID# 116923) (D-226618). Reach 8 825’ – 1,003’ Stormwater is conveyed west from the Type 2 Catch Basin within an 18-inch CPEP Storm Main (D-226618) sloped at 0.24%. Photo 7: Facing Northwest on NE 10th Street. Stormwater is collected in Type II catch basin and conveyed west within closed conveyance system. Ex. CB - Type 2 ID: 116923 Page 26 Boun Short Plat Reach 9 1,003’ – 1,038’ Stormwater is collected within a Type 2 Catch Basin and conveyed west within an 18-inch CPEP Storm Main (D-226618) sloped at 0.14%. Photo 8: Facing Northeast on NE 10th Street. Stormwater is collected in Type II catch basin and conveyed west within closed conveyance system. Additional flow enters the conveyance system from a type I catch basin located to the north of the type 2 catch basin. Reach 10 1,038’ – 1,138’ Stormwater is collected within a Type 2 Catch Basin located at the intersection of NE 10th Street and Anacortes Ave NE and conveyed north within a 30-inch CPEP Storm Main (D-226617) sloped at 0.39%. Photo 9: Facing Northwest at intersection of NE 10th Street and Anacortes Ave NE. Stormwater is collected in Type II catch basin and conveyed north within closed conveyance system. Additional flow enters the conveyance system from storm main east of this location. Ex. CB - Type 2 ID: 116903 Ex. CB - Type 2 ID: 116902 Page 27 Boun Short Plat Reach 11 1,138’ – 1,258’ Stormwater is collected within a Type 2 Catch Basin located approximately 100 feet north of the intersection of NE 10th Street and Anacortes Ave NE. Stormwater is conveyed north within a 30-inch CPEP Storm Main (D-226617) sloped at 0.40%. Photo 10: Facing North along Anacortes Ave NE. Stormwater is collected in Type II catch basin and conveyed north within closed conveyance system. Reach 12 1,258’ – 1,333’ Stormwater is collected within a Type 2 Catch Basin (Facility ID# 116900) within Anacortes Ave NE and conveyed north within a 30-inch CPEP Storm Main (D-226617) sloped at 0.41%. Completing the downstream analysis ¼ of a mile downstream from the project site natural discharge location. Photo 11: Facing North along Anacortes Ave NE. Stormwater is collected in Type II catch basin and conveyed north within closed conveyance system. Ex. CB - Type 2 ID: 116901 Ex. CB - Type 2 ID: 116900 N N Ex. CB - Type 2 ID: 116895 ¼ mile downstream Page 28 Boun Short Plat THRESHOLD DISCHARGE AREA #2.A (East Basin) Upstream The subject site sits on a high point with very little runoff crossing the site from adjacent properties. The site’s topography suggests that stormwater runoff from the site is divided and sheets flows to the southwest and to the northeast. The easterly portion of the site drains to the northeast into an existing conveyance swale within public right of way (Duvall Ave NE). Downstream Runoff contributing to the downstream corridor from the project site consists of the generated runoff from the existing asphalt within Duvall Ave NE and proposed sidewalk. The following is a discussion of the downstream corridor from threshold discharge area #2.A’s natural discharge location. See Appendix B for a Summary of each reach including: pipe size, length, and material as well as a map of each reach’s location. Reach 1 0’ The runoff generated from the project parcel sheet flows northwest and is collected within an existing roadside conveyance swale (Facility ID# 450085) located along the east boundary of the project parcel. Stormwater is conveyed north. Photo 12: Facing northwest along Duvall Ave NE. Stormwater sheet flows east within project parcel and enters existing conveyance swale along the east boundary of the site. Project Site Ex. Conveyance Swale ID: 450085 Page 29 Boun Short Plat Reach 2 0’- 695’ Stormwater is conveyed north within the conveyance swale along Duvall Ave NE. Stormwater passes through a series of CMP culverts that were installed under various driveways along this segment of flow path. The swale is well established with various land covers. No evidence erosion or flooding were observed at time of site visit. Garbage and other types of debris were found at various locations along the swale which could cause potential issues if not cleaned. Photo 13: Facing northwest along Duvall Ave NE. Stormwater shallow channel flows within the swale. Stormwater flows north. Reach 3 695’- 753’ Stormwater is collected within a 12-inch concrete culvert (Facility ID# 700093). The inlet to concrete culvert had a small amount of sedimentation build up and leaf debris. Photo 14: Facing west along Duvall Ave NE. Shallow channel flow enters concrete culvert. Debris that could potential disrupt channel flow Ex. Conc. Culvert (Facility ID #700093) Page 30 Boun Short Plat Reach 3 753’- 835’ Stormwater is collected within a Type 1 Catch Basin (Facility ID# 130734). Stormwater is convey north within a 12-inch concrete pipe. Photo 15: Facing west along Duvall Ave NE. Stormwater is conveyed north within a Type 1 CB. Reach 4 835’- 883’ Stormwater is collected within a Type 1 Catch Basin (Facility ID# 130735). Stormwater is convey north within a 12-inch concrete pipe. Photo 16: Facing west along Duvall Ave NE. Stormwater is conveyed north within a Type 1 CB. Ex. CB - Type 1 ID: 130734 Ex. CB - Type 1 ID: 130735 Page 31 Boun Short Plat Reach 5 883’- 1103’ Stormwater is collected within a Type 1 Catch Basin (Facility ID# 130736). Stormwater is convey north within a 12-inch concrete pipe. The 12-inch concrete pipe is sloped at 3.4% (R-147402). Photo 17: Facing northwest along Duvall Ave NE. Stormwater is conveyed north within a Type 1 CB. Reach 6 1103’- 1402’ Stormwater is collected within a Type 1 Catch Basin (Facility ID# 130794). Stormwater is convey north within a 12-inch concrete pipe. The 12-inch concrete pipe is sloped at 1.3% (R-147402). Completing the downstream analysis ¼ of a mile downstream from the project site natural discharge location. Photo 18: Facing southwest along Duvall Ave NE. Stormwater is conveyed north within a Type 1 CB. Ex. CB - Type 1 ID: 130736 Ex. CB - Type 1 ID: 130794 Page 32 Boun Short Plat 3.1.4 Task 4 - Drainage System Description and Problem Descriptions There are no apparent drainage complaints in the vicinity of the project site. However, during the downstream analysis, a problem was identified with releasing stormwater within Threshold Discharge Area #1 to an existing water quality facility that was installed to treat stormwater for the Vuong Short Plat (Project R-332511). Any increase in stormwater above the design water quality flow rate would cause the facility to improperly function. Mitigation of this downstream problem is necessary to allow the project vault to discharge to the downstream network. 3.1.5 Task 5 - Mitigation of Existing or Potential Problems To mitigate the downstream issue identified in Task 4, a flow splitter is proposed to bypass flows higher than the water quality flow rate of the existing water quality facility to the downstream network. See Section IV of this report for further details. Page 33 Boun Short Plat IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN The stormwater flow control and water quality facilities were designed in accordance with the 2009 King County Surface Water Design Manual (King Manual) and the City of Renton amendments to the Manual (Renton Manual). Threshold Discharge Area #1 Existing Site Hydrology (Part A-1) Threshold Discharge Area #1 is comprised of approximately 80% (46,236 sf) of the project parcel. Under existing conditions, the site is currently undeveloped with exception to an abandoned barn that is located near the northern boundary line of the parcel. The site’s topography suggests that stormwater runoff within threshold discharge area #1 sheet flows to the southwest over densely vegetated land cover consisting of various types of grass and brush. There is approximately six (6) feet of vertical relieve across the site with an average slope around 5%. Any accumulated runoff is allowed to overflow onto Chelan Ave NE into an existing catch basin near the southwest corner of the project parcel. Developed Site Hydrology (Part B-1) Under developed conditions, a drainage adjustment will allow for nearly the entire site (50,746 sf) to drain to Threshold Discharge Area #1. Stormwater will sheet flow over impervious areas and be collected within a closed conveyance system. Rooftop runoff will be directly tightlined to this conveyance system. The closed conveyance system then will route stormwater to a combined water quality and detention vault for treatment and flow control. The disturbance on site will include construction clearing and grading, construction of 1 public alley way, 1 private alley way, associated utilities (sewer, water, storm, power, etc.), required landscaping buffers and tree replacement, and eventually seven single-family houses with an associated driveway. To account for this future development, an estimated impervious area equating to the maximum impervious allowed per table 4-2-110A was utilized to size stormwater facilities. It is proposed that each driveway and roof drain connection will be collected and conveyed to the stormwater facility. Tables 4.1 and 4.2 break down the historic site conditions and developed site conditions TABLE 4.1 – Historic Site Conditions – Threshold Discharge Area #1 Sub-basin Total sf (ac) Impervious sf (ac) Till Grass sf (ac) Till Forest sf (ac) Threshold Discharge Area #1 (On-site) 46,236 (1.11) 0 0 46,236 (1.11) Threshold Discharge Area #1 (Off-site) 2,528 (0.06) 0 0 2,528 (0.06) Portion of Threshold Discharge Area #2.A that will drain to TDA 1 (Onsite) (Drainage Adjustment Area) (8,771-3,011=5,760 sf) 5,760 (0.13) 0 0 5,670 (0.13) TOTAL AREAS 54,524 (1.25) 0 0 54,524 (1.25) 1.06 Page 34 Boun Short Plat TABLE 4.2 – Developed Conditions – Threshold Discharge Area #1 Sub-basin Total sf (ac) Impervious sf (ac) Till Grass sf (ac) Till Forest sf (ac) Threshold Discharge Area #1 (to Vault)* (includes TDA 2.A area (5,670 sf) per Drainage Adjustment) 48,397 (1.11) 27,633 (0.634) 20,764 (0.476) 0 Threshold Discharge Area #1 (On-site Bypass) 3,599 (0.083) 1,904 (0.044) 1,695 (0.039) 0 Threshold Discharge Area #1 (Off-site Bypass) 2,528 (0.058) 2,050 (0.047) 478 (0.011) 0 TOTAL 54,524 (1.25) 31,587 (0.725) 22,937 (0.527) 0 (0) * The area reflects the site area after ROW dedication Performance Standards (Part C-1) Flow Control Facility: Performance standards for flow control design use Table 1.2.3.1 of the Manual. The site is located in the Flow Control Duration Standard – Matching Forested Site Conditions as designated by the City of Renton Flow Control Applications Map. This level of control is necessary for runoff from target surfaces (new impervious and pervious surfaces not fully dispersed) within the threshold discharge area. An underground detention vault has been proposed to detain runoff to the historic flow control levels per the Manual. Table 1.2.3.2 of the Manual indicates the level of flow control required based on the flow control area and the identified downstream problems, if any. This project did not identify any downstream problems and being located in the Flow Control Duration Standard Matching Forested Site Conditions (conservation flow control area) shall apply: historic site conditions Level 2 flow control standard, which matches historic durations for 50% of 2-year through 50-year peaks and matches historic 2-year and 10-year peaks. Target surfaces: new impervious, new pervious per Section 1.2.3.1 page 1-34 of the Manual. Flow Control BMPs: In addition to flow control facility requirements, implementation of flow control BMPs as part of this “subdivision” project is optional per Section 5.2.2.1 of the Manual. However, if the applicant wishes to implement or make provisions for implementation of BMPs as part of the subdivision project for purposes of receiving the BMP credits, then the requirements outlined in Section 5.2.2.1 must be met depending on the site location of the proposed BMPs. Based on a site evaluation, it has been determined that full dispersion/infiltration and basic dispersion/partial infiltration is not feasible. Per Section 5.2.1.1 Small Lot BMP Requirements of the Manual, one or more BMPs must be applied to (or used to mitigate for) an impervious area equal to at least 10% of site/lot for site/lot sizes up to 11,000 square feet. The project proposes to utilize a restricted footprint to satisfy the Small Lot BMP implementation requirement. Utilizing Section C.2.9.2 – Restricted Footprint of the manual, the following lot coverage areas were determined. Page 35 Boun Short Plat TABLE 4.3 – Restricted Footprint (C.2.9.2) Lot Number Lot Size (sf) Allowed Impervious (sf per Zoning – 65%) Restricted Imp. Area (55% or 4,000 sf -10% site area, whichever is smaller) (sf) Lot 1 5,172 3,362 2,845 Lot 2 6,121 3,979 3,367 Lot 3 6,168 4,009 3,383 Lot 4 6,245 4,059 3,376 Lot 5 5,731 3,725 3,152 Lot 6 5,718 3,717 3,145 Lot 7 6,553 4,259 3,345 Water Quality The project is located within a Basic Water Quality treatment area as designated by the King County 2009 Water Quality Application Maps and is not subject to the Enhanced Basic WQ menu per Section 1.2.8.1.A of the Manual. The goal of Basic WQ treatment is 80% removal of total suspended solids. To satisfy this treatment requirement, the project proposed a combined detention/wetvault located in the southwest corner of the project to provide treatment for onsite. See Part E of this section for analysis of the water quality facilities. Stormwater Conveyance The conveyance system capacity standards require that new conveyance systems contain the 25-year peak flow and ensure that the 100-year event does not create a severe flooding or erosion problem. See Section V of this report for the conveyance analysis per Core Requirement #4. Flow Control Systems (Part D-1) To address the increased runoff impact of the parcel, stormwater runoff from the proposed development will be mitigated by an underground detention vault in the southwest corner of the property within a dedicated Tract. As identified in Section III – Downstream Analysis of this report, a modification to the downstream drainage network is necessary to allow for the vault to discharge to the existing storm main within Chelan Ave NE. The existing type 1 catch basin near the northwest corner of the intersection of Chelan Ave NE and NE 10th Street will be replaced with a larger type 2 – 60” catch basin to allow for the use of an orifice flow splitter. Vault The detention portion of the combination detention and water quality facility was designed under Section 5.3.3.1 of the Manual. The vault was designed to discharge flow under the Flow Control Duration Standard – Matching Forested Site Conditions as discussed in Part C of this section. The facility was sized according to HSPF methodology using King County Runoff Time Series (KCTRS) software per Section 3.2.2 of the Manual. The vault will have a primary control structure designed to discharge stormwater per the flow control requirements. The flow control system utilizes a flow-restrictor tee with multiple orifices as shown in Figure 5.3.4.D of the Manual. The detention portion of the vault is 4.5 feet deep. The vault is broken into a two detention chambers due to site constraints. The first chamber (combined WQ and Detention) is 17.25’Wx107.5’L, approximately a 6:1 length to width ratio. The second chamber (detention only) is approximately 17.25’Wx107.5’L, having a total surface area of Page 36 Boun Short Plat 3,708 sf (3,380 sf required) The total provided volume within the detention vault is 16,677 cf. This volume is based on several factors. The size of the contributing basin, the type of ground cover, and any applicable flow control BMP facility sizing credits listed in Table 5.2.2.A of the Manual. See Table 4.4 for the vault basin areas used for input into KCTRS. As part of flow control BMP requirements, at least 10% of each individual lot size must be mitigated using an applicable Flow Control BMP type to receive Flow Control Sizing Credits. Due to site constraints, a restricted footprint of the allowed impervious for each lot will be incorporated into the site design to meet the Flow Control BMP requirement. These credits are reflected in the table below. Due to grading constraints of the site, portions of Tract A target pervious and impervious surfaces as well as off-site right of way improvements of Chelan Ave NE target surfaces cannot be collected within the proposed stormwater vault. A mitigation of target surfaces that bypass the facility was incorporated into the sizing the detention vault, as allowed per section 1.2.3.2.E of the manual. Per Section 1.2.3.2.E of the manual, the following conditions are met and approved by the City’s Surface Water Utility: Requirement #1 - The point of convergence for runoff discharged from the bypassed target surfaces and from the project’s flow control facility must be within a quarter- mile downstream of the facility’s project site discharge point. Requirement #1 Satisfied, the point of convergence for the runoff discharged from the bypassed target surfaces and from the project’s flow control facility meet at proposed CB#1 of the development. This is the natural discharge location for Threshold discharge area #1. Requirement #2 – The increase in the existing site conditions 100-year peak discharge from the area of bypassed target surfaces must not exceed 0.4 cfs. Requirement #2 Satisfied, KCRTS was utilized to analyze the peak flow of the existing site conditions of the proposed bypass area. This area equates to a total of 6,127 sf (3,599 sf + 2,528 sf) (0.141 acres) of Till Lawn. When analyzed in KCRTS, the 100- year storm event peak flow was found to be 0.030 cfs which is less than the maximum allowed 0.4 cfs. See KCRTS Flow Frequencies below. Flow Frequency Analysis Time Series File:existing_bypass.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.013 3 2/09/01 2:00 0.030 1 100.00 0.990 0.006 7 1/05/02 16:00 0.016 2 25.00 0.960 0.016 2 2/27/03 7:00 0.013 3 10.00 0.900 0.003 8 8/26/04 2:00 0.013 4 5.00 0.800 0.007 6 1/05/05 8:00 0.012 5 3.00 0.667 0.013 4 1/18/06 16:00 0.007 6 2.00 0.500 0.012 5 11/24/06 3:00 0.006 7 1.30 0.231 0.030 1 1/09/08 6:00 0.003 8 1.10 0.091 Computed Peaks 0.025 50.00 0.980 Page 37 Boun Short Plat Requirement #3 – Runoff from the bypassed target surfaces must not create a significant adverse impact to downstream drainage systems, salmonid habitat, or properties as determined by RDSD. Requirement #3 Satisfied, the bypassed target surface runoff will not create a significant adverse impact to the downstream drainage system. The bypassed runoff has been accounted for within the release rate of the proposed detention vault to match historic flow durations from ½ of the 2-year storm event up to the 50-year event. Requirement #4 – Water quality requirements applicable to the bypassed target surfaces must be met. Requirement #4 Satisfied, the bypassed target surface runoff meets the requirements of Section 1.2.8.2.D for Untreated Discharges. See Part E-1 of this report for further detail on water quality treatment requirements. Requirement #5 – Compensatory mitigation by a flow control facility must be provided so that the net effect at the point of convergence downstream is the same with or without bypass. The mitigation may be waived if the existing site conditions 100-year peak discharge from the area of bypassed target surfaces is increased by more than 0.1 cfs and flow control BMPs as detailed in Appendix C are applied to all impervious surfaces within the area of bypassed target surfaces. One or combination of the following methods may be used to provide compensatory mitigation by a flow control facility subject to permission/approvals from other parties as deemed necessary by RDSD: a) Design the project’s flow control facility or retrofit offsite flow control facility as needed to achieve the desired effect at the point of convergence, OR b) Design the project’s flow control facility or provide/retrofit an offsite flow control facility to mitigate an existing developed area (either onsite or offsite) that has runoff characteristics (i.e. peak flow and volume) equivalent to those of the bypassed target surfaces but is currently not mitigated or required to be mitigated to the same flow control performance requirement as the bypassed target surfaces. Requirement #5 Satisfied, the method described in option a was utilized to size the onsite flow control facility. A point of compliance (point of convergence) analysis was completed within KCRTS to ensure that the controlled stormwater release of the vault combined with the uncontrolled bypass flow equates to less than or equal to historic site stormwater durations from ½ of the 2-year storm event through the 50-year storm event. Page 38 Boun Short Plat TABLE 4.4 – Design Vault Basin Areas Sub-basin Total Area sf (ac) Impervious sf (ac) Till Grass sf (ac) Till Forest sf (ac) Threshold Discharge Area #1 - Onsite 48,397 (1.11) 27,633 (0.634) 20,764 (0.476) - Threshold Discharge Area #1 – Onsite (Bypass) 3,599 (0.083) 1,904 (0.044) 1,695 (0.039) - Threshold Discharge Area #1 – Offsite (Bypass) 2,528 (0.058) 2,050 (0.047) 478 (0.011) - TOTAL Area to Vault 48,397 (1.11) 27,633 (0.634) 20,764 (0.476) - TOTAL Area to Bypass Vault 6,127 (0.141) 3,954 (0.091) 2,173 (0.050) - TABLE 4.5 – Vault Volume Summary Vault Function Storage Interval Required Volume (cf) Provided Volume (cf) Sediment Storage 422.66–424.3 - - Water Quality 424.3-429.3 3,607 9,406 Detention 429.3-433.8 16, 16, Freeboard 433.8-434.3 - 1,8 Control Structure (Primary Discharge Control) The control structure was designed to use multiple orifices in order to discharge flow at a conservative flow control release rate. Flow through these offices may be determined at any given elevation through the following equations listed in Section 5.3.4.2 of the Manual: ghCAQ2, (Orifice) Where C = 0.62, A is the area of the orifice in square feet, g is the gravity constant, and h is the headwater in feet, and 2/3739.9 DHQweir, (Weir) Where D equals the diameter of the riser (18 inches) Page 39 Boun Short Plat TABLE 4.6 – Flow Summary Vault Stage Elevation Head, h (ft) Flow Rate, Q (cfs) 429.3 0.0 0.000 430.3 1.0 0.007 431.3 2.0 0.010 432.3 3.0 0.013 433.3 4.0 0.038 434.8 4.5 0.049 Primary Overflow The primary overflow is the overflow weir on the 18-inch diameter control riser. The weir is intended as a safety measure if any of the orifices are plugged. The bottom of the weir (top of riser) is set at the peak detention volume storage depth. Per Table 3.2 of the Manual, KCRTS with 15-minute time steps is to be used to calculate the peak flow if the majority of the tributary area is detained. Per section 5.3.1.1 of the Manual, the 100-year, 15-minute developed peak must be able to bypass the control structure. The developed 100-yr, 15-minute peak flow = 0.989 cfs. See the following pages for KCRTS output. The freeboard necessary above the top of the riser to allow for primary overflow is determined from the weir equation as shown above. ))(5.1(739.9989.0 2/3Hcfs, H = 0.166 ft = 2.0” Six inches of freeboard have been provided above the top of riser in the vault. KCRTS Peak Flow Output (15-minute time steps) Flow Frequency Analysis Time Series File:dev15min.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.302 6 8/27/01 18:00 0.989 1 100.00 0.990 0.220 8 1/05/02 15:00 0.676 2 25.00 0.960 0.676 2 12/08/02 17:15 0.425 3 10.00 0.900 0.244 7 8/23/04 14:30 0.408 4 5.00 0.800 0.408 4 11/17/04 5:00 0.369 5 3.00 0.667 0.369 5 10/27/05 10:45 0.302 6 2.00 0.500 0.425 3 10/25/06 22:45 0.244 7 1.30 0.231 0.989 1 1/09/08 6:30 0.220 8 1.10 0.091 Computed Peaks 0.885 50.00 0.980 Page 40 Boun Short Plat KCRTS Vault Output Page 41 Boun Short Plat KCRTS Design Input Time Series Peak Flows Predeveloped Conditions TSF Flow Frequency Analysis Time Series File:pre.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.079 2 2/09/01 18:00 0.101 1 100.00 0.990 0.021 7 1/06/02 4:00 0.079 2 25.00 0.960 0.058 4 2/28/03 3:00 0.061 3 10.00 0.900 0.002 8 3/24/04 20:00 0.058 4 5.00 0.800 0.035 6 1/05/05 8:00 0.051 5 3.00 0.667 0.061 3 1/18/06 21:00 0.035 6 2.00 0.500 0.051 5 11/24/06 4:00 0.021 7 1.30 0.231 0.101 1 1/09/08 9:00 0.002 8 1.10 0.091 Computed Peaks 0.094 50.00 0.980 Page 42 Boun Short Plat Developed Conditions (To Vault) TSF Flow Frequency Analysis Time Series File:dev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.196 6 2/09/01 2:00 0.401 1 100.00 0.990 0.157 8 1/05/02 16:00 0.243 2 25.00 0.960 0.236 3 2/27/03 7:00 0.236 3 10.00 0.900 0.167 7 8/26/04 2:00 0.208 4 5.00 0.800 0.202 5 10/28/04 16:00 0.202 5 3.00 0.667 0.208 4 1/18/06 16:00 0.196 6 2.00 0.500 0.243 2 10/26/06 0:00 0.167 7 1.30 0.231 0.401 1 1/09/08 6:00 0.157 8 1.10 0.091 Computed Peaks 0.348 50.00 0.980 Page 43 Boun Short Plat Bypass TSF Flow Frequency Analysis Time Series File:bypass.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.027 6 2/09/01 2:00 0.053 1 100.00 0.990 0.021 8 1/05/02 16:00 0.034 2 25.00 0.960 0.032 3 2/27/03 7:00 0.032 3 10.00 0.900 0.023 7 8/26/04 2:00 0.028 4 5.00 0.800 0.028 4 10/28/04 16:00 0.028 5 3.00 0.667 0.028 5 1/18/06 16:00 0.027 6 2.00 0.500 0.034 2 10/26/06 0:00 0.023 7 1.30 0.231 0.053 1 1/09/08 6:00 0.021 8 1.10 0.091 Computed Peaks 0.047 50.00 0.980 Page 44 Boun Short Plat Retention/Detention Facility Type of Facility: Detention Vault Facility Length: 60.00 ft Facility Width: 60.00 ft Facility Area: 3600. sq. ft Effective Storage Depth: 4.50 ft Stage 0 Elevation: 0.00 ft Storage Volume: 16200. cu. ft Riser Head: 4.50 ft Riser Diameter: 18.00 inches Number of orifices: 2 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 0.53 0.016 2 3.56 1.10 0.032 4.0 Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) 0.00 0.00 0. 0.000 0.000 0.00 0.01 0.01 36. 0.001 0.001 0.00 0.02 0.02 72. 0.002 0.001 0.00 0.03 0.03 108. 0.002 0.001 0.00 0.04 0.04 144. 0.003 0.002 0.00 0.05 0.05 180. 0.004 0.002 0.00 0.15 0.15 540. 0.012 0.003 0.00 0.25 0.25 900. 0.021 0.004 0.00 0.35 0.35 1260. 0.029 0.005 0.00 0.45 0.45 1620. 0.037 0.005 0.00 0.55 0.55 1980. 0.045 0.006 0.00 0.65 0.65 2340. 0.054 0.006 0.00 0.75 0.75 2700. 0.062 0.007 0.00 0.85 0.85 3060. 0.070 0.007 0.00 0.95 0.95 3420. 0.079 0.007 0.00 1.05 1.05 3780. 0.087 0.008 0.00 1.15 1.15 4140. 0.095 0.008 0.00 1.25 1.25 4500. 0.103 0.009 0.00 1.35 1.35 4860. 0.112 0.009 0.00 1.45 1.45 5220. 0.120 0.009 0.00 1.55 1.55 5580. 0.128 0.009 0.00 1.65 1.65 5940. 0.136 0.010 0.00 1.75 1.75 6300. 0.145 0.010 0.00 1.85 1.85 6660. 0.153 0.010 0.00 1.95 1.95 7020. 0.161 0.011 0.00 2.05 2.05 7380. 0.169 0.011 0.00 2.15 2.15 7740. 0.178 0.011 0.00 2.25 2.25 8100. 0.186 0.011 0.00 2.35 2.35 8460. 0.194 0.012 0.00 2.45 2.45 8820. 0.202 0.012 0.00 Page 45 Boun Short Plat 2.55 2.55 9180. 0.211 0.012 0.00 2.65 2.65 9540. 0.219 0.012 0.00 2.75 2.75 9900. 0.227 0.013 0.00 2.85 2.85 10260. 0.236 0.013 0.00 2.95 2.95 10620. 0.244 0.013 0.00 3.05 3.05 10980. 0.252 0.013 0.00 3.15 3.15 11340. 0.260 0.014 0.00 3.25 3.25 11700. 0.269 0.014 0.00 3.35 3.35 12060. 0.277 0.014 0.00 3.45 3.45 12420. 0.285 0.014 0.00 3.55 3.55 12780. 0.293 0.014 0.00 3.56 3.56 12816. 0.294 0.014 0.00 3.57 3.57 12852. 0.295 0.015 0.00 3.58 3.58 12888. 0.296 0.015 0.00 3.59 3.59 12924. 0.297 0.017 0.00 3.61 3.61 12996. 0.298 0.018 0.00 3.62 3.62 13032. 0.299 0.021 0.00 3.63 3.63 13068. 0.300 0.023 0.00 3.64 3.64 13104. 0.301 0.024 0.00 3.65 3.65 13140. 0.302 0.024 0.00 3.75 3.75 13500. 0.310 0.029 0.00 3.85 3.85 13860. 0.318 0.033 0.00 3.95 3.95 14220. 0.326 0.036 0.00 4.05 4.05 14580. 0.335 0.038 0.00 4.15 4.15 14940. 0.343 0.041 0.00 4.25 4.25 15300. 0.351 0.043 0.00 4.35 4.35 15660. 0.360 0.045 0.00 4.45 4.45 16020. 0.368 0.047 0.00 4.50 4.50 16200. 0.372 0.048 0.00 4.60 4.60 16560. 0.380 0.512 0.00 4.70 4.70 16920. 0.388 1.360 0.00 4.80 4.80 17280. 0.397 2.450 0.00 4.90 4.90 17640. 0.405 3.750 0.00 5.00 5.00 18000. 0.413 5.220 0.00 5.10 5.10 18360. 0.421 6.650 0.00 5.20 5.20 18720. 0.430 7.180 0.00 5.30 5.30 19080. 0.438 7.670 0.00 5.40 5.40 19440. 0.446 8.140 0.00 5.50 5.50 19800. 0.455 8.570 0.00 5.60 5.60 20160. 0.463 8.990 0.00 5.70 5.70 20520. 0.471 9.390 0.00 5.80 5.80 20880. 0.479 9.770 0.00 5.90 5.90 21240. 0.488 10.140 0.00 6.00 6.00 21600. 0.496 10.490 0.00 6.10 6.10 21960. 0.504 10.830 0.00 6.20 6.20 22320. 0.512 11.170 0.00 6.30 6.30 22680. 0.521 11.490 0.00 6.40 6.40 23040. 0.529 11.800 0.00 6.50 6.50 23400. 0.537 12.110 0.00 Page 46 Boun Short Plat Hyd Inflow Outflow Peak Storage Stage Elev (Cu-Ft) (Ac-Ft) 1 0.40 0.05 4.43 4.43 15961. 0.366 2 0.20 0.04 4.18 4.18 15043. 0.345 3 0.24 0.04 4.19 4.19 15077. 0.346 4 0.20 0.03 3.75 3.75 13499. 0.310 5 0.21 0.01 2.84 2.84 10237. 0.235 6 0.20 0.01 0.99 0.99 3550. 0.081 7 0.16 0.01 2.69 2.69 9697. 0.223 8 0.17 0.01 1.42 1.42 5113. 0.117 Hyd R/D Facility Tributary Reservoir POC Outflow Outflow Inflow Inflow Target Calc 1 0.05 0.05 ******** ******* 0.08 2 0.04 0.03 ******** 0.09 0.05 3 0.04 0.03 ******** ******* 0.06 4 0.03 0.03 ******** ******* 0.04 5 0.01 0.03 ******** ******* 0.04 6 0.01 0.03 ******** ******* 0.03 7 0.01 0.02 ******** ******* 0.03 8 0.01 0.02 ******** ******* 0.03 ---------------------------------- Route Time Series through Facility Inflow Time Series File:dev.tsf Outflow Time Series File:rdout POC Time Series File:dsout Inflow/Outflow Analysis Peak Inflow Discharge: 0.399 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.048 CFS at 22:00 on Feb 9 in Year 1 Peak Reservoir Stage: 4.49 Ft Peak Reservoir Elev: 4.49 Ft Peak Reservoir Storage: 16164. Cu-Ft : 0.371 Ac-Ft Add Time Series:bypass.tsf Peak Summed Discharge: 0.079 CFS at 9:00 on Jan 9 in Year 8 Point of Compliance File:dsout.tsf Flow Frequency Analysis Time Series File:rdout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 0.048 1 2/09/01 22:00 0.048 4.49 1 100.00 0.990 0.012 6 1/07/02 5:00 0.047 4.43 2 25.00 0.960 0.045 3 3/06/03 22:00 0.045 4.33 3 10.00 0.900 0.009 8 8/26/04 8:00 0.029 3.75 4 5.00 0.800 0.012 7 1/08/05 6:00 0.013 2.87 5 3.00 0.667 0.013 5 1/20/06 1:00 0.012 2.69 6 2.00 0.500 0.029 4 11/26/06 23:00 0.012 2.67 7 1.30 0.231 0.047 2 1/09/08 17:00 0.009 1.42 8 1.10 0.091 Page 47 Boun Short Plat Computed Peaks 0.047 4.47 50.00 0.980 Flow Frequency Analysis Time Series File:dsout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.062 2 2/09/01 18:00 0.079 1 100.00 0.990 0.032 7 1/05/02 16:00 0.062 2 25.00 0.960 0.061 3 3/06/03 18:00 0.061 3 10.00 0.900 0.031 8 8/26/04 2:00 0.040 4 5.00 0.800 0.033 6 10/28/04 16:00 0.038 5 3.00 0.667 0.038 5 1/18/06 16:00 0.033 6 2.00 0.500 0.040 4 10/26/06 0:00 0.032 7 1.30 0.231 0.079 1 1/09/08 9:00 0.031 8 1.10 0.091 Computed Peaks 0.073 50.00 0.980 Flow Duration from Time Series File:rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.001 26106 42.573 42.573 57.427 0.574E+00 0.002 5825 9.499 52.073 47.927 0.479E+00 0.003 6489 10.582 62.655 37.345 0.373E+00 0.005 3888 6.341 68.995 31.005 0.310E+00 0.006 6848 11.168 80.163 19.837 0.198E+00 0.007 3968 6.471 86.634 13.366 0.134E+00 0.009 1947 3.175 89.809 10.191 0.102E+00 0.010 2926 4.772 94.581 5.419 0.542E-01 0.011 1428 2.329 96.910 3.090 0.309E-01 0.013 900 1.468 98.377 1.623 0.162E-01 0.014 378 0.616 98.994 1.006 0.101E-01 0.015 417 0.680 99.674 0.326 0.326E-02 0.017 8 0.013 99.687 0.313 0.313E-02 0.018 32 0.052 99.739 0.261 0.261E-02 0.019 5 0.008 99.747 0.253 0.253E-02 0.021 3 0.005 99.752 0.248 0.248E-02 0.022 2 0.003 99.755 0.245 0.245E-02 0.023 4 0.007 99.762 0.238 0.238E-02 0.024 16 0.026 99.788 0.212 0.212E-02 0.026 9 0.015 99.803 0.197 0.197E-02 0.027 9 0.015 99.817 0.183 0.183E-02 0.028 6 0.010 99.827 0.173 0.173E-02 0.030 7 0.011 99.839 0.161 0.161E-02 0.031 4 0.007 99.845 0.155 0.155E-02 0.032 4 0.007 99.852 0.148 0.148E-02 0.034 4 0.007 99.858 0.142 0.142E-02 0.035 6 0.010 99.868 0.132 0.132E-02 0.036 7 0.011 99.879 0.121 0.121E-02 0.038 9 0.015 99.894 0.106 0.106E-02 0.039 7 0.011 99.905 0.095 0.946E-03 0.040 5 0.008 99.914 0.086 0.864E-03 0.042 5 0.008 99.922 0.078 0.783E-03 0.043 10 0.016 99.938 0.062 0.620E-03 Page 48 Boun Short Plat 0.044 13 0.021 99.959 0.041 0.408E-03 0.045 14 0.023 99.982 0.018 0.179E-03 0.047 4 0.007 99.989 0.011 0.114E-03 Flow Duration from Time Series File:dsout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.001 26165 42.670 42.670 57.330 0.573E+00 0.003 8309 13.550 56.220 43.780 0.438E+00 0.004 5591 9.118 65.338 34.662 0.347E+00 0.006 6504 10.607 75.944 24.056 0.241E+00 0.008 4865 7.934 83.878 16.122 0.161E+00 0.010 3658 5.965 89.843 10.157 0.102E+00 0.011 2577 4.203 94.046 5.954 0.595E-01 0.013 1454 2.371 96.417 3.583 0.358E-01 0.015 1067 1.740 98.157 1.843 0.184E-01 0.016 412 0.672 98.829 1.171 0.117E-01 0.018 191 0.311 99.141 0.859 0.859E-02 0.020 161 0.263 99.403 0.597 0.597E-02 0.022 67 0.109 99.512 0.488 0.488E-02 0.023 29 0.047 99.560 0.440 0.440E-02 0.025 37 0.060 99.620 0.380 0.380E-02 0.027 37 0.060 99.680 0.320 0.320E-02 0.029 30 0.049 99.729 0.271 0.271E-02 0.030 17 0.028 99.757 0.243 0.243E-02 0.032 23 0.038 99.795 0.205 0.205E-02 0.034 13 0.021 99.816 0.184 0.184E-02 0.035 12 0.020 99.835 0.165 0.165E-02 0.037 6 0.010 99.845 0.155 0.155E-02 0.039 12 0.020 99.865 0.135 0.135E-02 0.041 11 0.018 99.883 0.117 0.117E-02 0.042 8 0.013 99.896 0.104 0.104E-02 0.044 10 0.016 99.912 0.088 0.881E-03 0.046 11 0.018 99.930 0.070 0.701E-03 0.048 10 0.016 99.946 0.054 0.538E-03 0.049 8 0.013 99.959 0.041 0.408E-03 0.051 5 0.008 99.967 0.033 0.326E-03 0.053 4 0.007 99.974 0.026 0.261E-03 0.054 5 0.008 99.982 0.018 0.179E-03 0.056 3 0.005 99.987 0.013 0.130E-03 0.058 2 0.003 99.990 0.010 0.978E-04 0.060 2 0.003 99.993 0.007 0.652E-04 0.061 3 0.005 99.998 0.002 0.163E-04 Duration Comparison Anaylsis Base File: pre.tsf New File: dsout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New %Change Probability Base New %Change 0.017 | 0.93E-02 0.97E-02 4.6 | 0.93E-02 0.017 0.018 1.8 0.022 | 0.63E-02 0.48E-02 -24.0 | 0.63E-02 0.022 0.020 -11.4 0.027 | 0.48E-02 0.32E-02 -32.9 | 0.48E-02 0.027 0.022 -17.6 0.032 | 0.37E-02 0.22E-02 -41.4 | 0.37E-02 0.032 0.025 -20.1 first cutoff should be less than or equal to 0% Page 49 Boun Short Plat 0.036 | 0.28E-02 0.16E-02 -43.7 | 0.28E-02 0.036 0.028 -22.8 0.041 | 0.22E-02 0.12E-02 -47.4 | 0.22E-02 0.041 0.032 -23.3 0.046 | 0.15E-02 0.70E-03 -52.2 | 0.15E-02 0.046 0.038 -17.6 0.051 | 0.99E-03 0.33E-03 -67.2 | 0.99E-03 0.051 0.043 -15.2 0.055 | 0.62E-03 0.18E-03 -71.1 | 0.62E-03 0.055 0.047 -15.8 0.060 | 0.34E-03 0.49E-04 -85.7 | 0.34E-03 0.060 0.050 -16.3 0.065 | 0.21E-03 0.00E+00 -100.0 | 0.21E-03 0.065 0.054 -17.1 0.070 | 0.16E-03 0.00E+00 -100.0 | 0.16E-03 0.070 0.055 -20.2 0.074 | 0.82E-04 0.00E+00 -100.0 | 0.82E-04 0.074 0.059 -20.1 0.079 | 0.16E-04 0.00E+00 -100.0 | 0.16E-04 0.079 0.062 -21.2 Maximum positive excursion = 0.000 cfs ( 1.8%) occurring at 0.017 cfs on the Base Data:pre.tsf and at 0.018 cfs on the New Data:dsout.tsf Maximum negative excursion = 0.009 cfs (-24.5%) occurring at 0.039 cfs on the Base Data:pre.tsf and at 0.029 cfs on the New Data:dsout.tsf ---------------------------------- Route Time Series through Facility Inflow Time Series File:dev.tsf Outflow Time Series File:rdout POC Time Series File:dsout Inflow/Outflow Analysis Peak Inflow Discharge: 0.399 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.048 CFS at 22:00 on Feb 9 in Year 1 Peak Reservoir Stage: 4.49 Ft Peak Reservoir Elev: 4.49 Ft Peak Reservoir Storage: 16164. Cu-Ft : 0.371 Ac-Ft Add Time Series:bypass.tsf Peak Summed Discharge: 0.079 CFS at 9:00 on Jan 9 in Year 8 Point of Compliance File:dsout.tsf Flow Frequency Analysis Time Series File:rdout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 0.048 1 2/09/01 22:00 0.048 4.49 1 100.00 0.990 0.012 6 1/07/02 5:00 0.047 4.43 2 25.00 0.960 0.045 3 3/06/03 22:00 0.045 4.33 3 10.00 0.900 0.009 8 8/26/04 8:00 0.029 3.75 4 5.00 0.800 0.012 7 1/08/05 6:00 0.013 2.87 5 3.00 0.667 0.013 5 1/20/06 1:00 0.012 2.69 6 2.00 0.500 0.029 4 11/26/06 23:00 0.012 2.67 7 1.30 0.231 0.047 2 1/09/08 17:00 0.009 1.42 8 1.10 0.091 Computed Peaks 0.047 4.47 50.00 0.980 Page 50 Boun Short Plat Flow Frequency Analysis Time Series File:dsout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.062 2 2/09/01 18:00 0.079 1 100.00 0.990 0.032 7 1/05/02 16:00 0.062 2 25.00 0.960 0.061 3 3/06/03 18:00 0.061 3 10.00 0.900 0.031 8 8/26/04 2:00 0.040 4 5.00 0.800 0.033 6 10/28/04 16:00 0.038 5 3.00 0.667 0.038 5 1/18/06 16:00 0.033 6 2.00 0.500 0.040 4 10/26/06 0:00 0.032 7 1.30 0.231 0.079 1 1/09/08 9:00 0.031 8 1.10 0.091 Computed Peaks 0.073 50.00 0.980 Flow Duration from Time Series File:rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.001 26106 42.573 42.573 57.427 0.574E+00 0.002 5825 9.499 52.073 47.927 0.479E+00 0.003 6489 10.582 62.655 37.345 0.373E+00 0.005 3888 6.341 68.995 31.005 0.310E+00 0.006 6848 11.168 80.163 19.837 0.198E+00 0.007 3968 6.471 86.634 13.366 0.134E+00 0.009 1947 3.175 89.809 10.191 0.102E+00 0.010 2926 4.772 94.581 5.419 0.542E-01 0.011 1428 2.329 96.910 3.090 0.309E-01 0.013 900 1.468 98.377 1.623 0.162E-01 0.014 378 0.616 98.994 1.006 0.101E-01 0.015 417 0.680 99.674 0.326 0.326E-02 0.017 8 0.013 99.687 0.313 0.313E-02 0.018 32 0.052 99.739 0.261 0.261E-02 0.019 5 0.008 99.747 0.253 0.253E-02 0.021 3 0.005 99.752 0.248 0.248E-02 0.022 2 0.003 99.755 0.245 0.245E-02 0.023 4 0.007 99.762 0.238 0.238E-02 0.024 16 0.026 99.788 0.212 0.212E-02 0.026 9 0.015 99.803 0.197 0.197E-02 0.027 9 0.015 99.817 0.183 0.183E-02 0.028 6 0.010 99.827 0.173 0.173E-02 0.030 7 0.011 99.839 0.161 0.161E-02 0.031 4 0.007 99.845 0.155 0.155E-02 0.032 4 0.007 99.852 0.148 0.148E-02 0.034 4 0.007 99.858 0.142 0.142E-02 0.035 6 0.010 99.868 0.132 0.132E-02 0.036 7 0.011 99.879 0.121 0.121E-02 0.038 9 0.015 99.894 0.106 0.106E-02 0.039 7 0.011 99.905 0.095 0.946E-03 0.040 5 0.008 99.914 0.086 0.864E-03 0.042 5 0.008 99.922 0.078 0.783E-03 0.043 10 0.016 99.938 0.062 0.620E-03 0.044 13 0.021 99.959 0.041 0.408E-03 Page 51 Boun Short Plat 0.045 14 0.023 99.982 0.018 0.179E-03 0.047 4 0.007 99.989 0.011 0.114E-03 Flow Duration from Time Series File:dsout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.001 26165 42.670 42.670 57.330 0.573E+00 0.003 8309 13.550 56.220 43.780 0.438E+00 0.004 5591 9.118 65.338 34.662 0.347E+00 0.006 6504 10.607 75.944 24.056 0.241E+00 0.008 4865 7.934 83.878 16.122 0.161E+00 0.010 3658 5.965 89.843 10.157 0.102E+00 0.011 2577 4.203 94.046 5.954 0.595E-01 0.013 1454 2.371 96.417 3.583 0.358E-01 0.015 1067 1.740 98.157 1.843 0.184E-01 0.016 412 0.672 98.829 1.171 0.117E-01 0.018 191 0.311 99.141 0.859 0.859E-02 0.020 161 0.263 99.403 0.597 0.597E-02 0.022 67 0.109 99.512 0.488 0.488E-02 0.023 29 0.047 99.560 0.440 0.440E-02 0.025 37 0.060 99.620 0.380 0.380E-02 0.027 37 0.060 99.680 0.320 0.320E-02 0.029 30 0.049 99.729 0.271 0.271E-02 0.030 17 0.028 99.757 0.243 0.243E-02 0.032 23 0.038 99.795 0.205 0.205E-02 0.034 13 0.021 99.816 0.184 0.184E-02 0.035 12 0.020 99.835 0.165 0.165E-02 0.037 6 0.010 99.845 0.155 0.155E-02 0.039 12 0.020 99.865 0.135 0.135E-02 0.041 11 0.018 99.883 0.117 0.117E-02 0.042 8 0.013 99.896 0.104 0.104E-02 0.044 10 0.016 99.912 0.088 0.881E-03 0.046 11 0.018 99.930 0.070 0.701E-03 0.048 10 0.016 99.946 0.054 0.538E-03 0.049 8 0.013 99.959 0.041 0.408E-03 0.051 5 0.008 99.967 0.033 0.326E-03 0.053 4 0.007 99.974 0.026 0.261E-03 0.054 5 0.008 99.982 0.018 0.179E-03 0.056 3 0.005 99.987 0.013 0.130E-03 0.058 2 0.003 99.990 0.010 0.978E-04 0.060 2 0.003 99.993 0.007 0.652E-04 0.061 3 0.005 99.998 0.002 0.163E-04 Vault - Flow Control Duration Performance Evaluation (Per Section 3.2.2) 1. The post-developed flow duration curve lies strictly on or below the predevelopment curve at the lower limit of the range of control (between 50% of the 2-year and the 2-year). See KCRTS Flow Duration Comparison on page 50 and 51 of this report. Requirement Satisfied - The dsout (combined flow duration of release of vault and bypass structure) duration curve lies strictly below the target duration curve. 2. At any duration within the range of control, the post-development flow is less than 1.1 times the predevelopment flow. Page 52 Boun Short Plat Requirement Satisfied – After running a flow durations comparison analysis, a maximum positive excursion found among the range of control was less than 10%. 3. The target duration curve may not be exceeded along more than 50% of the range of control. Requirement Satisfied - After running a flow duration’s comparison analysis, 1 of the 14 flow duration cutoff values (50%) were exceeded. 4. The peak flow at the upper end of the range of control (historical 50-year) may not exceed predeveloped levels by more than 10%. Requirement Satisfied – Peak flows at the upper end of the range of control do not exceed predeveloped flow levels by greater than 10%. Vault – Additional Peak Flow Requirement (Match 2-year and 10-year peaks) The predeveloped peak flows were compared to the downstream point of convergence of the flow control system at the 2 and 10-year events for peak flow compliance. Peak Flow 2-Year (Predeveloped): 0.035 cfs Peak Flow 2-Year (Downstream Convergence [dsout]): 0.033 cfs Peak Flow 10-Year (Predeveloped): 0.061 cfs Peak Flow 10-Year (Downstream Convergence [dsout]): 0.061 cfs Requirement Satisfied – Peak flows are within tolerable range of acceptance to meet the matching criteria. Flow Splitter (Catch Basin #12) The following flow splitter was sized, in part, utilizing stormwater calculations that were completed during the development of the Vuong Short Plat, prepared by Touma Engineers. For further information about this stormwater system, see below. The flow splitter was sized utilizing Section 6.2.5 of the King County Manual. Per 6.2.5.1, orifice flow splitters shall be sized per Section 5.3.4.2. Qwq=CAorifice(2gh)^0.5 Where Qwq=0.11 cfs (Water Quality Flow Rate Per Vuong Short Plat) C = 0.62 (for plate orifice) G = 32.2 (ft/s2) H = Hydraulic Head (overflow elevation – outlet IE) = 429.37 - 427.87 = 1.5’ Solve A = 0.11/(0.62*(2*32.2*1.5)^0.5) = 0.0181 ft2 Solve for r = A = ϖr2 = (0.181/ϖ)^0.5 = 0.0759’ Solve for d = 2r = 2*0.0759 = 0.1518’ = 1.82” A 1.82” diameter orifice shall be installed at the bottom of the riser tee within the proposed type 2-60” catch basin. See sheet C5 of the plan set for further flow splitter details. Flow Splitter Flow Capacity Check: Per Section 6.2.5.2 – Design Criteria Item 3, the maximum head shall be minimized to flow in excess of the water quality design flow. Page 53 Boun Short Plat Specifically, flow to the WQ facility at the 100-year water surface shall not increase the design WQ flow by more than 10%. To analyze the flow splitter at the 100-year storm event, the rational method was utilized to calculate a 100-year storm event flow rate for both the Boun Short Plat and Vuong Short Plat which are tributary to this conveyance point. An assumed time of concentration was utilized of 6.3 minutes (minimum). Vuong Short Plat Total Sub-Basin Area = 1.13 acres (per Approved TIR) Impervious = 0.83 acres Pervious = 0.30 acres Boun Short Plat Total Sub-Basin Area = 1.25 acres Impervious = 0.725 acres Pervious = 0.527 acres Total contributing Sub-Basin Areas: Total Impervious = 1.56 acres Total Pervious = 0.83 acres Rational Method Equation Qr=CIrA Where Cc= (C1A1+C2A2+C3A3+….CnAn)/At Cc = (1.56 acres * 0.90 (per Table 3.2.1.A) + 0.83 acres * 0.25 (per Table 3.2.1.A))/2.39 Cc = 0.67 unitless Where Ir = Pr *ir; Pr = the total precipitation at the project site for the 24-hour duration storm event for a given return frequency. Per Figure 3.2.1.D for the 100-Year Storm Event, Pr = 3.9 inches. ir = (Ar)(Tc)(-br), where Ar = 2.61, Br = 0.63 per Table 3.2.1.B. ir = 2.61*6.3-0.63 ir = 0.8186 Ir = 3.9” * 0.8186 = 3.19 Q100 = 0.67*3.19*2.39 = 5.11 cfs Per Figure 5.3.4.H – Riser Inflow Curves, an approximate increase of 0.36’ of head will be necessary to pass the 100-year storm event through the top of the overflow riser with utilizing a 30” (2.5’) standpipe riser. However, a correction needs to be made to this figure to account for the minor flow that will leave the facility through the WQ facility orifice outlet. The following equation was derived to account for this flow loss. Q100 = 9.739 DH3/2 + CAorifice(2gh)^0.5 5.22 cfs = 9.739 * 2.5 * H3/2 + 0.62* 0.0181 (2*32.2*h)^0.5 Solving for H, H = 0.36’ Verify that the change of 0.36’ in head does not increase the amount of flow to WQ facility >10%. A modified flow splitter is proposed at Catch Basin #12 to allow for the overflow elevation of the WQ facility to be 0.4’ higher than the overflow elevation of the downstream Page 54 Boun Short Plat network outlet. This will allow for water to flow into the downstream network prior to allowing water to surcharge the water quality facility. The change in flow between the WQ flow rate and the 100-year storm event is the following (note: overflow above the 12” tee is not allowed, therefore weir flow was ignored): Qorifice=CAorifice(2gh)^0.5 = 0.62*0.0181*(2*32.2*(1.5+.36))^0.5 = 0.122 Percent Difference = (0.122 – 0.11)/0.123 = 0.976 = 9.7% < 10% Therefore, a 30” standpipe will have the capacity to convey the 100-year storm event without increase the amount of flow conveyed to the WQ facility by more than 10%. See Plan Sheet C5 of the accompanying plan set for further details. 3.2.1 RATIONAL METHOD 2009 Surface Water Design Manual 1/9/2009 3-13 TABLE 3.2.1.A RUNOFF COEFFICIENTS - "C" VALUES FOR THE RATIONAL METHOD General Land Covers Single Family Residential Areas* Land Cover C Land Cover Density C Dense forest Light forest Pasture Lawns Playgrounds Gravel areas Pavement and roofs Open water (pond, lakes, wetlands) 0.10 0.15 0.20 0.25 0.30 0.80 0.90 1.00 0.20 DU/GA (1 unit per 5 ac.) 0.40 DU/GA (1 unit per 2.5 ac.) 0.80 DU/GA (1 unit per 1.25 ac.) 1.00 DU/GA 1.50 DU/GA 2.00 DU/GA 2.50 DU/GA 3.00 DU/GA 3.50 DU/GA 4.00 DU/GA 4.50 DU/GA 5.00 DU/GA 5.50 DU/GA 6.00 DU/GA 0.17 0.20 0.27 0.30 0.33 0.36 0.39 0.42 0.45 0.48 0.51 0.54 0.57 0.60 * Based on average 2,500 square feet per lot of impervious coverage. For combinations of land covers listed above, an area-weighted "Cc:x At" sum should be computed based on the equation Cc: x At = (C1 x A1) + (C2 x A2) + ...+(Cn x An), where A8 = (A1 + A2 + ...+An), the total drainage basin area. TABLE 3.2.1.B COEFFICIENTS FOR THE RATIONAL METHOD "iR" EQUATION Design Storm Return Frequency aR bR 2 years 5 years 10 years 25 years 50 years 100 years 1.58 2.33 2.44 2.66 2.75 2.61 0.58 0.63 0.64 0.65 0.65 0.63 TABLE 3.2.1.C kR VALUES FOR Tt USING THE RATIONAL METHOD Land Cover Category kR Forest with heavy ground litter and meadow 2.5 Fallow or minimum tillage cultivation 4.7 Short grass pasture and lawns 7.0 Nearly bare ground 10.1 Grassed waterway 15.0 Paved area (sheet flow) and shallow gutter flow 20.0 3.2.1 RATIONAL METHOD 2009 Surface Water Design Manual 1/9/2009 3-17 FIGURE 3.2.1.D 100-YEAR 24-HOUR ISOPLUVIALS SNOHOMISH COUNTY KING COUNTY KING COUNTY PIERCE COUNTY KIRKLAND REDMOND REDMOND DUVALL WOODINVILLEBOTHELL MERCERISLAND RENTON TUKWILA SEATTLE SEATTLE BURIEN NORMANDY PARK SEATAC BELLEVUE NEWCASTLE ISSAQUAH SNOQUALMIE CARNATION NORTH BEND SEATTLE SHORELINE MEDINA BEAUXARTS CLYDEHILL YARROW POINTHUNTSPOINT LAKEFOREST PARK FEDERAL WAY PACIFICMILTON ALGONA AUBURN KENT KENT DES MOINES BLACK DIAMOND ENUMCLAW KENT Vashon Island MauryIsland COVINGTON MAPLEVALLEY 520 522 104 5 522 405 908 900 167 169 515 516 509 518 509 90 405 405 99 5 5 900 90 99 99 99 509 161 164 167 18 18 18 516 169 169 410 520 Elliott Bay LakeSamm amishLakeWashington P ugetSound CedarRiver Green River Whi t eRi ver Sa mmami shRiverSnoqualmie River 0 2 4 Miles N 100-Year 24-Hour Precipitation in Inches WESTERN KING COUNTY 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.83. 9 3.93.94.0 4.04.05.04.14.24.34.44.55.55.5 6.0 6.56.56.04.1 4.2 4.3 4. 4 4.54.6Project Location 5.3.4 CONTROL STRUCTURES — METHODS OF ANALYSIS 2009 Surface Water Design Manual 1/9/2009 5-47 Riser Overflow The nomograph in Figure 5.3.4.H may be used to determine the head (in feet) above a riser of given diameter and for a given flow (usually the 100-year peak flow for developed conditions). FIGURE 5.3.4.H RISER INFLOW CURVES 1 10 100 0.1 1 10HEAD IN FEET (measured from crest of riser) Qweir=9.739 DH3/2 Qorifice=3.782 D2H1/2 Q in cfs, D and H in feet Slope change occurs at weir-orifice transition Q (cubic feet per second)18 21 24 27 30 42 487254 10 12 15 33 36 RISER DIAMETER (inches)0.36' 5.22 WATERQUALITYThefollowingcalculationistodeterminewaterqualityvolume,itisbasedon1/3of2-yearstorm,whichis2/3=0.67”.The0.67”precipitationisusedforcomputingthewaterqualityvolume.SBUWSCSMETHODFORCOMPUTINGRUNOFFHYDROGRAPHSTORMOPTIONS:1-S.C.S.TYPE-lA2-7-DAYDESIGN STORM3-STORM DATAFILESPECIFYSTORMOPTION:1S.C.S.TYPE-lARAINFALLDISTRIBUTIONENTER:FREQ(YEAR),DURATION(HOUR),PRECIP(INCHES)1,24,0.67S.C.S.TYPE-lADISTRiBUTION1-YEAR24-HOURSTORM.67hTOTALPRECIP.*********ENTER:A(PERV),CN(PERV),A(IMPERV),CN(IMPERV),TCFORBASINNO.I0.3,86,0.83,98,6.3DATAPRINT-OUT:AREA(ACRES)PERVIOUSIMPERVIOUSTC(MINUTES)ACNACN1.1.386.0.898.06.3PEAK-Q(CFS)T-PEAK(HRS)VOL(CU-FT).117.8314961496cu.ft.isrequired.Itisproposedtoconstructunderground60-inchpipetostorethecalculatedwaterqualityvolume.Cross-sectionareaof60-inchpipelessthebottomandtop6-inchesis16.02s.fRefertosketchonfollowingsheetLengthof60-inchpipeis1496/16.02=93.33 IfUSE95.00ifof6OinchVUONG SHORT PLAT TIR EXERT Page 59 Boun Short Plat Water Quality System (Part E-1) The project is located within a Basic Water Quality treatment area as discussed in Part C in this Section. To satisfy this treatment requirement, the project proposes a combined detention/wetvault located in the southwest corner of the project to provide basic treatment for onsite runoff. Vault (Water Quality) The proposed water quality wetvault for the site has been sized to obtain adequate particulate removal efficiency per section 6.4.1.1 of the Manual. This is based on the volume of the wetvault in relation to the volume of stormwater runoff from the mean annual storm, VB/VR. For basic water quality vaults, this ratio, vault volume/mean annual storm, shall equal at least 3. The sizing of the wetvault is accomplished by first determining the acreage of pervious and impervious areas. These values are used to calculate the treatment runoff volumes by multiplying the acreage of each surface type by the mean annual storm (0.04 feet, per Figure 6.4.1.A of the Manual). Runoff factors are also applied to each surface type, 0.25 for grass and 0.90 for impervious. The sum of the grass and impervious runoff volumes is the total runoff volume from the mean annual storm, VR. To calculate the minimum required volume of the wetpool (VB), the mean annual runoff volume (VR) was multiplied by 3. Grass runoff = (20,765 sf)(0.04’)(0.25) = 208 cf Impervious runoff = (27,633 sf)(0.04’)(0.90) = 975 cf Forest runoff= (0 sf)(0.039’)(0.10)= 0 cf Total runoff volume, VR = 213 cf + 975 cf + 0 cf = 1,203 cf Total basin volume, VB = 1,203 cf x 3 = 3,607 cf The water quality portion of the vault is 16’Wx107.5’L, a 6:1 length to width ratio. The proposed depth of the wetvault is 5.00 feet. This provides a total volume of 8,600 cf. See sheet C7 of the engineering plan set for vault dimensions and details. Untreated Discharge Due to grading constraints of the site, portions of Tract A target pervious and impervious surfaces as well as off-site right of way improvements of Chelan Ave NE target surfaces cannot be collected within the proposed stormwater WQ wetvault. A discharge of untreated target surfaces is proposed, as allowed per section 1.2.8.2.D of the manual. Per Section 1.2.8.2.D of the manual, the following conditions must be met and approved by the City’s Surface Water Utility: Requirement #1 – Treatment of the constrained area by filter strip, biofiltration, or a linear sand filter is not feasible, and a treatment trade as described in Section C is not possible. Requirement #1 Satisfied, the constrained area primarily consists of asphalt road with public right of way. A filter strip, biofiltration, and a linear sand filter are not feasible due to the confined space. The project site is not subject to any upstream untreated runoff, therefore, a treatment trade is infeasible for this site. Requirement #2 – The untreated target surface is less than 5,000 square feet of new PGIS and is less than 5,000 square feet of new plus replaced PGIS on a redevelopment project. Page 60 Boun Short Plat Requirement #2 Satisfied, the untreated target surface equates to a total of 3,954 sf of new/replaced PGIS. This is less than the maximum 5,000 sf allowed. Requirement #3 – Any target PGPS within the area to be released untreated shall be addressed with a landscape management plan. Requirement #3 Satisfied, A landscape plan has been prepared for this development. Threshold Discharge Area #2 (2.A & 2.B) Existing Site Hydrology (Part A-2) Threshold Discharge Area #2 is comprised of approximately 20% (11,440 sf) of the project parcel. This includes 8,771 sf of area near the southeast corner of the project parcel and 2,669 sf of project area which consists of an 18-foot strip of land to be dedicated as part of this project. Under existing conditions, Threshold Discharge Area 2.A (the eastern portion of the project site) is currently undeveloped. The site’s topography suggests this portion of land sheet flows to the northeast over densely vegetated land cover consisting of various types of grass and brush. There is approximately three (3) feet of vertical relief across the site with an average slope around 5%. Any accumulated runoff is allowed to enter a stormwater conveyance swale within Duvall Ave NE near the northeast corner of the project parcel. Threshold Discharge Area 2.B (the 18’ strip of land located near the northwest corner of the project site) is currently undeveloped with the exception of an existing gravel driveway. The site’s topography suggests this portion of land sheet flows to the northwest over vegetated land cover consisting of short lawn. There is approximately one (1) foot of vertical relief across the site with an average slope around 2%. Any accumulated runoff would flow northwest along the western edge of the existing gravel access road. Threshold Discharge Area 2.A and 2.B join approximately ½ of a mile downstream of the project site. Developed Site Hydrology (Part B-2) Under developed conditions, a drainage adjustment will allow for a portion of the Threshold Discharge Area 2.A (5,760 sf) to drain to Threshold Discharge Area #1. The remaining 3,011 sf will allow stormwater to sheet flow over pervious landscape areas towards an existing conveyance swale within Duvall Ave NE. The disturbance within threshold discharge area #2 will include construction clearing and grading, construction of associated utilities (water, power, etc.), required landscaping buffers, and tree replacement. Tables 4.7 and 4.8 break down the historic site conditions and developed site conditions TABLE 4.7 – Historic Site Conditions – Threshold Discharge Area #2 Sub-basin Total sf (ac) Impervious sf (ac) Till Grass sf (ac) Till Forest sf (ac) Threshold Discharge Area #2.A – Onsite (8,771-5,760=3,011 sf) 3,011 (0.07) 0 0 3,011 (0.07) Threshold Discharge Area #2.B 2,669 (0.06) 0 0 2,669 (0.06) TOTAL 5,680 (0.130) 0 0 5,680 (0.130) Page 61 Boun Short Plat TABLE 4.8 – Developed Conditions – Threshold Discharge Area #2 Sub-basin Total sf (ac) Impervious sf (ac) Till Grass sf (ac) Till Forest sf (ac) Threshold Discharge Area #2.A - Onsite 3,011 (0.07) 0 (0.00) 3,011 (0.07) 0 Threshold Discharge Area #2.B 2,669 (0.06) 789 (0.02) 1,880 (0.04) 0 TOTAL 5,680 (0.13) 789 (0.02) 4,891 (0.11) 0 (0) * The area reflects the site area after ROW dedication Performance Standards (Part C-2) Flow Control Facility: The proposed project is located within the Flow Control Duration Standard – Matching Historic Site Conditions area: Match developed discharge durations to historic (forested) duration for the range of pre-developed discharge rates from 50% of the 2-year peak flow up to the full 50-year peak flow. The above is required unless a flow control exception applies to the proposed site conditions. Per Section 1.2.3.1.B – Exception 2, The facility requirement in Flow Control Duration Standard Matching Forested Site Conditions Areas is waived for any threshold discharge area in which there is no more than 0.1-cfs difference in the sum of the developed 100-year peak flows for those target surfaces subject to this requirement and the sum of forested (historic) site conditions 100-year peak flows for the same surface areas. The developed conditions do not exceed a 0.1 cfs difference in the sum of developed 100- year peak flows for those target surfaces subject to the flow control facility requirement and the sum of historic site conditions 100-year peak flows for the same surface areas. Thus flow control is not required for this threshold discharge area per section 1.2.3.1.B of the Renton Manual. Part D of this section for analysis output comparing the pre and post flow rates. Water Quality The project is located within the Basic Water Quality treatment area as designated by the King County 2009 Water Quality Application Maps and is not subject to the Enhanced Basic WQ menu per Section 1.2.8.1.A of the Manual. The goal of Basic WQ treatment is 80% removal of total suspended solids. This is required unless an applicable exemption to Core Requirment #8 applies. This threshold discharge area meets the treatment exemption for surface area per Section 1.2.8 Exemptions. The proposed conditions will not increase PGIS surface areas within Threshold Discharge Area #2. Therefore, a water quality facility for TDA #2.A is not proposed at this time. Stormwater Conveyance Not applicable for this TDA. Flow Control Systems (Part D-2) As mention in part C-2, a flow control facility is not required for this TDA. Flow calculations for each basin condition subject to the flow control analysis were analyzed at the 100-year storm event. See Table 4.9 and 4.10 below and following page for basin areas and KCRTS output. Page 62 Boun Short Plat TABLE 4.9 – Historic Site Conditions – Threshold Discharge Area #2.A – Target Surfaces Sub-basin Total sf (ac) Impervious sf (ac) Till Grass sf (ac) Till Forest sf (ac) Threshold Discharge Area #2.A - Onsite 5,680 (0.13) 0 0 5,680 (0.13) TABLE 4.10 – Developed Site Conditions – Threshold Discharge Area #2.A – Target Surfaces Sub-basin Total sf (ac) Impervious sf (ac) Till Grass sf (ac) Till Forest sf (ac) Threshold Discharge Area #2.A - Onsite 5,680 (0.13) 789 (0.02) 4,891 (0.11) 0 Flow Frequency Analysis Time Series File:pre.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.008 2 2/09/01 18:00 0.010 1 100.00 0.990 0.002 7 1/06/02 3:00 0.008 2 25.00 0.960 0.006 4 2/28/03 3:00 0.006 3 10.00 0.900 0.000 8 12/23/03 11:00 0.006 4 5.00 0.800 0.004 6 1/05/05 8:00 0.005 5 3.00 0.667 0.006 3 1/18/06 22:00 0.004 6 2.00 0.500 0.005 5 11/24/06 5:00 0.002 7 1.30 0.231 0.010 1 1/09/08 8:00 0.000 8 1.10 0.091 Computed Peaks 0.010 50.00 0.980 Flow Frequency Analysis Time Series File:dev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.014 4 2/09/01 2:00 0.033 1 100.00 0.990 0.009 6 1/05/02 16:00 0.018 2 25.00 0.960 0.018 2 2/27/03 7:00 0.015 3 10.00 0.900 0.007 8 8/26/04 2:00 0.014 4 5.00 0.800 0.009 7 10/28/04 16:00 0.014 5 3.00 0.667 0.015 3 1/18/06 16:00 0.009 6 2.00 0.500 0.014 5 11/24/06 3:00 0.009 7 1.30 0.231 0.033 1 1/09/08 6:00 0.007 8 1.10 0.091 Computed Peaks 0.028 50.00 0.980 Page 63 Boun Short Plat The difference at the 100-year storm event frequency is 0.023 cfs (0.033-0.010) which is less than the 0.1 cfs increase requirement. Therefore, a flow control facility is not required in Threshold Discharge Area #2. V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN Onsite The conveyance system was designed per Section 3 and 4 of the Manual. Table 3.2 of the Manual suggests that the Rational Method of analysis is required for undetained areas for tributary areas less than 10 ac. To analyze the proposed systems, the Rational Method was used based on:  QR = CIRA  King county I.D.F. Family (2009 Manual)  25 and 100-year 24-hour storm event flow  Runoff coefficients  Appropriate Manning’s number The Rational Method was used per section 3.2.1. of the Manual. The runoff coefficients, ‘C’ values were taken from Table 3.2.1.A. A C value of 0.9 was used for the roofed surface and a conservative time of concentration value of 6.3 minutes was used. This is a low travel time, but will provide relatively higher flow rate. Conveyance Pipes The new stormwater conveyance system has been proposed to convey runoff in a way that does not impact the drainage basin of the existing site. A conveyance and backwater analysis for the proposed project have been calculated as shown on the following page. Stormwater runoff will drain to catch basins and then flow through varying diameter storm pipes. All new pipes are to be designed with sufficient capacity to convey and contain at minimum the 25-year peak flow and not cause a flooding nuisance during a 100-year storm event. If for larger storms that may overtop the storm structures, all stormwater will be isolated on site. LOT 55,731 SFLOT 76,553 SFLOT 65,718 SFLOT 36,168 SFLOT 26,121 SFLOT 46,245 SFLOT 15,172 SFTRACT A7,277 SFSS~435434436 437437 437438438 438439439435434 SHEET OFJOB NUMBERNO. DESCRIPTION INIT. DATE DRAWN BY:CHECKED BY:SCALE: HORZ:VERT: DATE:CIVIL & STRUCTURAL ENGINEERING | LAND SURVEYING | PLANNING PROJECT MANAGEMENT | FEASIBILITY | PERMIT EXPEDITING LAKEWOOD OFFICE7602 Bridgeport Way W #3D Lakewood, WA 98499 phone: 253-301-4157 fax: 253-336-3950 SNOQUALMIE OFFICE 35312 SE Center St Snoqualmie, WA 98065 phone: 425-392-8055 fax: 425-392-0108 beylerconsulting.com BEYLER CONSULTING Plan. Design. ManageEXHIBIT1CONVEYANCE MAP BOUN SHORT PLAT BASIN MAPS CITY OF RENTON,WASHINGTON16-2061A PORTION OF SECTION 10, TOWNSHIP 23 NORTH, 5 WEST, W.M.DUVALL AVE NE CHELAN AVE NE BOUN SHORT PLATCONVEYANCE MAPSCALE: 1" = 30'1530030NATURAL DISCHARGELOCATION #1(RELOCATED CATCHBASIN)NATURAL DISCHARGELOCATION #2.A(EXISTING SWALE)CB #6SUB-BASIN #6SUB BASIN AREA = 45,510 SFIMPERVIOUS AREA = 26,380 SFPERVIOUS AREA = 19,130 SFCB #4CB #5SUB-BASIN #5SUB-BASIN AREA = 2,899 SFIMPERVIOUS AREA = 1,254 SFPERVIOUS AREA = 1,645 SFCB #3CB #2CB #1CB #9CB #10OUTLET #1EX. CB #SUB-BASIN #8SUB-BASIN AREA = 3,964 SFIMPERVIOUS AREA = 2,927 SFPERVIOUS AREA = 1,037 SFSUB-BASIN #7SUB-BASIN AREA = 1,257 SFIMPERVIOUS AREA = 1,006 SFPERVIOUS AREA = 251 SFSUB-BASIN #2SUB-BASIN AREA = 2,137 SFIMPERVIOUS AREA = 1,403 SFPERVIOUS AREA = 734 SFLINK 1LINK 2LINK 3LINK 4LINK 5LINK 6LINK 7LINK 8LINK 91 REVISED PER CITY REVIEW #1 DTY 5/17SUB-BASIN #1SUB-BASIN AREA = 540 SFIMPERVIOUS AREA = 520 SFPERVIOUS AREA = 20 SF COMPOSITE A C*A Tc i25 I25 Q25 (basin)Q25 (accum.)DIA. MATERIAL SLOPE QFULL VFULL V25 RThetaDEPTHd/D PIPE FROM TO (ac) C (ac) C C (ac) (Min.) cfs cfs in. n ft/ft cfs fps fps radians ft LINK‐9 CB10 CB9 0.0200 0.25 0.0700 0.9 0.76 0.0900 0.068 6.3 0.804 2.774 0.189 0.189 12 0.013 0.007 3.08 3.92 2.11 0.10 1.65 0.16 0.16 LINK‐8 CB9 CB2 0.0200 0.25 0.0300 0.9 0.64 0.0500 0.032 6.3 0.804 2.774 0.089 0.277 12 0.013 0.008 3.18 4.05 2.49 0.12 1.85 0.2 0.2 LINK‐7 CB6 CB4 0.4400 0.25 0.6100 0.9 0.63 1.0500 0.659 6.3 0.804 2.774 1.828 1.828 12 0.013 0.017 4.63 5.89 5.56 0.23 2.90 0.44 0.44 LINK‐6 CB5 CB4 0.0400 0.25 0.0300 0.9 0.53 0.0700 0.037 6.3 0.804 2.774 0.103 0.103 12 0.013 0.027 5.82 7.41 1.90 0.03 0.90 0.05 0.05 LINK‐5 CB4 CB3 0.0000 0.25 0.0000 0.9 0.00 0.0000 0.000 6.3 0.804 2.774 0.000 1.931 12 0.013 0.052 8.11 10.33 8.58 0.19 2.49 0.34 0.34 LINK‐4 CB3 Vault*0.0000 0.25 0.0000 0.9 0.00 0.0000 0.000 6.3 0.804 2.774 0.000 1.931 12 0.013 0.022 5.33 6.78 5.72 0.19 2.53 0.35 0.35 LINK‐3 Vault* CB2 0.0000 0.25 0.0000 0.9 0.00 0.0000 0.000 6.3 0.804 2.774 0.000 1.931 12 0.013 0.009 3.38 4.31 4.88 0.30 2.94 0.55 0.55 LINK‐2 CB2 CB1 0.0200 0.25 0.0500 0.9 0.71 0.0700 0.050 6.3 0.804 2.774 0.139 2.347 12 0.013 0.010 3.57 4.55 5.79 0.36 2.74 0.6 0.6 LINK‐1 CB 1 OUTLET #1 0.0005 0.25 0.0120 0.9 0.87 0.0125 0.011 6.3 0.804 2.774 0.030 2.377 12 0.013 0.010 3.57 4.55 5.79 0.36 2.74 0.6 0.6 (1) (2) (3) (4) (5) (6) (7) (8)(9)(10) (11) (12)(13)(14)(15)(16)(17)(18)(19) (20) Q Length Pipe Size n Value Outlet IE Inlet IE Barrel Area Vf Barrel Velocity Head TW Elev. Friction Loss Entr. HGL Elev. Entr. Head Loss Exit Head Loss Outlet Cont. Elev. Inlet Cont. Elev. Appr. Vel. Head Bend Head Loss Junction Head Loss HW Rim El Diff. PIPE FROM TO (cfs) (ft) (in) (ft) (ft) (sqft) (fps) (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) LINK‐1 OUTLET #1 CB1 2.38 30 12 0.013 428.52 428.82 0.79 3.03 0.142 429.00 0.08 429.08 0.07 0.142 429.30 429.92 ‐0.14 0.17 0.00 429.96 432.29 2.33 LINK‐2 CB1 CB2 2.35 13 12 0.013 428.82 428.95 0.79 2.99 0.139 429.96 0.03 429.99 0.07 0.139 430.20 430.05 ‐0.10 0.12 0.01 430.23 432.32 2.09 LINK‐3 CB2 Vault*1.93 39 12 0.013 428.95 429.30 0.79 2.46 0.094 430.23 0.09 430.32 0.05 0.094 430.46 430.35 0.00 0.00 0.00 430.46 437.00 6.54 LINK‐4 Vault* CB3 1.93 9 12 0.013 427.30 427.50 0.79 2.46 0.094 433.80 0.04 433.84 0.05 0.094 433.98 428.60 ‐0.09 0.12 0.00 434.00 437.63 3.63 LINK‐5 CB3 CB4 1.93 25 12 0.013 427.50 428.79 0.79 2.46 0.094 434.00 0.11 434.11 0.05 0.094 434.25 429.89 ‐0.08 0.11 0.00 434.27 436.98 2.71 LINK‐6 CB4 CB5 0.10 121 12 0.013 428.79 432.00 0.79 0.13 0.000 434.27 0.01 434.29 0.00 0.000 434.29 432.00 0.00 0.00 0.00 434.29 436.21 1.92 LINK‐7 CB4 CB6 1.83 68 12 0.013 428.79 429.93 0.79 2.33 0.084 434.27 0.20 434.47 0.04 0.084 434.60 430.83 0.00 0.00 0.00 434.60 436.50 1.90 LINK‐8 CB2 CB9 0.28 48 12 0.013 428.95 429.33 0.79 0.35 0.002 430.46 0.01 430.47 0.00 0.002 430.47 429.33 0.00 0.00 0.00 430.47 432.77 2.30 LINK‐9 CB9 CB10 0.19 39 12 0.013 429.33 429.62 0.79 0.24 0.001 430.47 0.00 430.48 0.00 0.001 430.48 429.62 0.00 0.00 0.00 430.48 432.62 2.14 BOUN SHORT PLAT BACKWATER CALCULATION SHEET (25 YEAR) LOCATION *Vault TW Elevation = Top Detention = 433.80 BOUN SHORT PLAT CONVEYANCE SYSTEM ANALYSIS AND SIZING TABLE USING THE RATIONAL METHOD (25 YEAR) LOCATION PERVIOUS IMPERVIOUS *Vault Modelled as a flow through structure at full capacity COMPOSITE A C*A Tc i100 I100 Q100 (basin)Q100 (accum.)DIA. MATERIAL SLOPE QFULL VFULL V25 RThetaDEPTHd/D PIPE FROM TO (ac) C (ac) C C (ac) (Min.) cfs cfs in. n ft/ft cfs fps fps radians ft LINK‐9 CB10 CB9 0.0200 0.25 0.0700 0.9 0.76 0.0900 0.068 6.3 0.819 3.192 0.217 0.217 12 0.013 0.007 3.08 3.92 2.11 0.10 1.65 0.16 0.16 LINK‐8 CB9 CB2 0.0200 0.25 0.0300 0.9 0.64 0.0500 0.032 6.3 0.819 3.192 0.102 0.319 12 0.013 0.008 3.18 4.05 2.63 0.13 1.95 0.22 0.22 LINK‐7 CB6 CB4 0.4400 0.25 0.6100 0.9 0.63 1.0500 0.659 6.3 0.819 3.192 2.104 2.104 12 0.013 0.017 4.63 5.89 5.73 0.24 3.02 0.47 0.47 LINK‐6 CB5 CB4 0.0400 0.25 0.0300 0.9 0.53 0.0700 0.037 6.3 0.819 3.192 0.118 0.118 12 0.013 0.027 5.82 7.41 1.90 0.03 0.90 0.05 0.05 LINK‐5 CB4 CB3 0.0000 0.25 0.0000 0.9 0.00 0.0000 0.000 6.3 0.819 3.192 0.000 2.222 12 0.013 0.052 8.11 10.33 8.84 0.20 2.57 0.36 0.36 LINK‐4 CB3 Vault*0.0000 0.25 0.0000 0.9 0.00 0.0000 0.000 6.3 0.819 3.192 0.000 2.222 12 0.013 0.022 5.33 6.78 6.12 0.21 2.74 0.4 0.4 LINK‐3 Vault* CB2 0.0000 0.25 0.0000 0.9 0.00 0.0000 0.000 6.3 0.819 3.192 0.000 2.222 12 0.013 0.009 3.38 4.31 5.49 0.36 2.74 0.6 0.6 LINK‐2 CB2 CB1 0.0200 0.25 0.0500 0.9 0.71 0.0700 0.050 6.3 0.819 3.192 0.160 2.701 12 0.013 0.010 3.57 4.55 8.18 0.60 2.09 0.75 0.75 LINK‐1 CB 1 OUTLET #1 0.0005 0.25 0.0120 0.9 0.87 0.0125 0.011 6.3 0.819 3.192 0.035 2.736 12 0.013 0.010 3.57 4.55 8.18 0.60 2.09 0.75 0.75 (1) (2) (3) (4) (5) (6) (7) (8)(9)(10) (11) (12)(13)(14)(15)(16)(17)(18)(19) (20) Q Length Pipe Size n Value Outlet IE Inlet IE Barrel Area Vf Barrel Velocity Head TW Elev. Friction Loss Entr. HGL Elev. Entr. Head Loss Exit Head Loss Outlet Cont. Elev. Inlet Cont. Elev. Appr. Vel. Head Bend Head Loss Junction Head Loss HW Rim El Diff. PIPE FROM TO (cfs) (ft) (in) (ft) (ft) (sqft) (fps) (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) LINK‐1 OUTLET #1 CB1 2.74 30 12 0.013 428.52 428.82 0.79 3.48 0.188 429.00 0.05 429.05 0.09 0.188 429.34 430.22 ‐0.18 0.23 0.00 430.27 432.29 2.02 LINK‐2 CB1 CB2 2.70 13 12 0.013 428.82 428.95 0.79 3.44 0.184 430.27 0.02 430.29 0.09 0.184 430.57 430.35 ‐0.13 0.16 0.01 430.61 432.32 1.71 LINK‐3 CB2 Vault*2.22 39 12 0.013 428.95 429.30 0.79 2.83 0.124 430.61 0.09 430.70 0.06 0.124 430.89 430.35 0.00 0.00 0.00 430.89 437.00 6.11 LINK‐4 Vault* CB3 2.22 9 12 0.013 427.30 427.50 0.79 2.83 0.124 433.80 0.04 433.84 0.06 0.124 434.03 428.60 ‐0.12 0.16 0.00 434.06 437.63 3.57 LINK‐5 CB3 CB4 2.22 25 12 0.013 427.50 428.79 0.79 2.83 0.124 434.06 0.13 434.19 0.06 0.124 434.38 429.89 ‐0.11 0.14 0.01 434.41 436.98 2.57 LINK‐6 CB4 CB5 0.12 121 12 0.013 428.79 432.00 0.79 0.15 0.000 434.41 0.02 434.43 0.00 0.000 434.43 432.00 0.00 0.00 0.00 434.43 436.21 1.78 LINK‐7 CB4 CB6 2.10 68 12 0.013 428.79 429.93 0.79 2.68 0.111 434.41 0.25 434.66 0.06 0.111 434.83 430.83 0.00 0.00 0.00 434.83 436.50 1.67 LINK‐8 CB2 CB9 0.32 48 12 0.013 428.95 429.33 0.79 0.41 0.003 430.89 0.01 430.90 0.00 0.003 430.90 429.33 0.00 0.00 0.00 430.90 432.77 1.87 LINK‐9 CB9 CB10 0.22 39 12 0.013 429.33 429.62 0.79 0.28 0.001 430.90 0.00 430.91 0.00 0.001 430.91 429.62 0.00 0.00 0.00 430.91 432.62 1.71 BOUN SHORT PLAT BACKWATER CALCULATION SHEET (100 YEAR) LOCATION *Vault TW Elevation = Top Detention = 433.80 BOUN SHORT PLAT CONVEYANCE SYSTEM ANALYSIS AND SIZING TABLE USING THE RATIONAL METHOD (100 YEAR) LOCATION PERVIOUS IMPERVIOUS *Vault Modelled as a flow through structure at full capacity Page 67 Boun Short Plat VI. SPECIAL REPORTS AND STUDIES Geotechnical Report Geotechnical Report, Proposed Boon-Phany Short Plat October 12, 2015; Prepared by PanGEO Incorporated VII. OTHER PERMITS Existing Permits: There are currently no other permits that effect the drainage submittal or the Technical Information Report. Future Permits: NPDES Permit Building Permit for Each Lot VIII. CSWPPP ANALYSIS AND DESIGN Please refer to Appendix E for the prepared CSWPPP IX. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT A completed Bond Quantities Worksheet can be found in Appendix D. X. OPERATION AND MAINTENANCE MANUAL The Operation and Maintenance of the proposed facilities is to be the responsibility of the City of Renton. The Maintenance worksheet from Appendix A of the 2009 King County Surface Water Design Manual have been included in Appendix F of this report. XI. APPENDICES APPENDIX A – OFFSITE STUDY MAPS 3,983 332 COR Critical Areas Map - Regulated Slopes This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. None 8/29/2016 Legend 2260 113 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 226 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Boundary Other City of Renton Addresses Parcels Slope City of Renton >15% & <=25% >25% & <=40% (Sensitive) >40% & <=90% (Protected) >90% (Protected) Slope King County >15% & <=25% >25% & <=40% >40% & <=90% >90% 3,983 332 COR Critical Areas Map - Seismic This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. None 8/29/2016 Legend 2260 113 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 226 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Boundary Other City of Renton Addresses Parcels Seismic Hazard Areas 3,983 332 COR Critical Areas Map - Wellhead Protection Areas This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. None 8/29/2016 Legend 2260 113 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 226 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Boundary Other City of Renton Addresses Parcels Wellhead Protection Area Zones Zone 1 Zone 1 Modified Zone 2 3,983 332 COR Critical Areas Map - Wetland This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. None 8/29/2016 Legend 2260 113 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 226 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Boundary Other City of Renton Addresses Parcels Wetlands Date: 8/29/2016 ±The information included on this map has been compiled by King County staff from a variety of sources and issubject to change without notice. King County makes no representations or warranties, express or implied,as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intendedfor use as a survey product. King County shall not be liable for any general, special, indirect, incidental, orconsequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuseof the information contained on this map. Any sale of this map or information on this map is prohibited except bywritten permission of King County. Legend Parcels Erosion hazard(1990 SAO) Seismic hazard(1990 SAO) Landslide hazard(1990 SAO) Coal mine hazard(1990 SAO) class 1 class 2 perennial class 2 salmonid class 3 unclassified Wetland (1990SAO) Sensitive areanotice on title Chinookdistribution Wildlife network severe moderate King County Critical Areas Map Date: 8/29/2016 ±The information included on this map has been compiled by King County staff from a variety of sources and issubject to change without notice. King County makes no representations or warranties, express or implied,as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intendedfor use as a survey product. King County shall not be liable for any general, special, indirect, incidental, orconsequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuseof the information contained on this map. Any sale of this map or information on this map is prohibited except bywritten permission of King County. Legend Parcels Bonded Commercial-MF Commercial-SF Construction DOT FMD Regional Residential Drainagecomplaints King County Drainage Complaints Map Project Area APPENDIX B – DOWNSTREAM SYSTEM TABLE AND MAPS 1,991 166 Threshold Discharge Area #1 - Downstream Map This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. 8/29/2016 Legend 1130 56 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 113 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Boundary Other City of Renton Addresses Parcels Wetlands Network Structures Inlet Manhole Utility Vault Unknown Structure Control Structure Pump Station Discharge Point Water Quality Detention Facilities Pond Tank Vault Wetland Pipe Culvert Open Drains Virtual Drainline Facility Outline Private Network Structures Project Site Natural Discharge Location #1 (Reach 1) Reach #2 Reach #3 Reach #4 Reach #5 Reach #6 Reach #7 (pond) Reach #8 1,991 166 Threshold Discharge Area #1 - Downstream Map 2 This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. 8/29/2016 Legend 1130 56 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 113 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Boundary Other City of Renton Addresses Parcels Wetlands Network Structures Inlet Manhole Utility Vault Unknown Structure Control Structure Pump Station Discharge Point Water Quality Detention Facilities Pond Tank Vault Wetland Pipe Culvert Open Drains Virtual Drainline Facility Outline Private Network Structures Reach #8 Reach #9 Reach #10 Reach #11 Reach #12 (approx. 1/4 mile downstream) OFF-SITEANALYSISDRAINAGE SYSTEMTABLESURFACEWATER DESIGNMANUAL,COREREQUIREMENT#2Basin:Subbasin Name: Subbasin Number:Symbol DrainageComponent Type, Name, and Size DrainageComponentDescriptionSlopeDistancefrom site dischargeExistingProblemsPotentialProblemsObservations of field inspector, resource reviewer, or resident see map Type: sheet flow, swale, stream, channel, pipe, pond; Size: diameter, surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume %¼ ml = 1,320 ft. constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion tributary area, likelihood of problem, overflow pathways, potential impacts May Creek Threshold Discharge Area #1Cedar River/ Lake Washington (WRIA8)Threshold Discharge Area #1TDA #1Reach 1Sheet FlowDense Vegetation5-100 ftNone ObservedReach 212" Conc. Pipe31 Feet3.2 31 ftNone ObservedReach 312" CPEP Pipe149 Feet0.5180 ftNone ObservedReach 412" CPEP Pipe95 Feet0.5275 ftThis Section of Pipe Drains to an ExistingWQ FacilityReach 560" CMP Pipe120 Feet0395 ftCapacity of WQ Fac.Capacity of WQ Fac.60" CMP WQ TankReach 612" CPEP Pipe82 Feet4.8477 ftNone ObservedReach 7PondRegional Facility-825 ftNone ObservedReach 818" CPEP Pipe178 Feet0.241,003 ftNone ObservedReach 918" CPEP Pipe35 Feet0.141,038 ftNone ObservedReach 1030" CPEP Pipe100 Feet0.391,138 ftNone ObservedReach 1130" CPEP Pipe120 Feet0.401,258 ftNone ObservedReach 1230" CPEP Pipe75 Feet0.411,333 ftNone Observed 3,983 332 Threshold Discharge Area #2.A - Downstream Map 1 This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. 9/1/2016 Legend 2260 113 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 226 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Boundary Other City of Renton Addresses Parcels Network Structures Inlet Manhole Utility Vault Unknown Structure Control Structure Pump Station Discharge Point Water Quality Detention Facilities Pond Tank Vault Wetland Pipe Culvert Open Drains Facility Outline Private Network Structures Inlet Manhole Natural Discharge Location #2.A (Reach 1) Project Site Reach #1 Reach #2 Reach #3 Reach #4 3,983 332 Threshold Discharge Area #2.A - Downstream Map 2 This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. 9/1/2016 Legend 2260 113 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 226 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Boundary Other City of Renton Addresses Parcels Network Structures Inlet Manhole Utility Vault Unknown Structure Control Structure Pump Station Discharge Point Water Quality Detention Facilities Pond Tank Vault Wetland Pipe Culvert Open Drains Facility Outline Private Network Structures Inlet Manhole Reach #5 Reach #6 (approx. 1/4 mile downstream OFF-SITEANALYSISDRAINAGE SYSTEMTABLESURFACEWATER DESIGNMANUAL,COREREQUIREMENT#2Basin:Subbasin Name: Subbasin Number:Symbol DrainageComponent Type, Name, and Size DrainageComponentDescriptionSlopeDistancefrom site dischargeExistingProblemsPotentialProblemsObservations of field inspector, resource reviewer, or resident see map Type: sheet flow, swale, stream, channel, pipe, pond; Size: diameter, surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume %¼ ml = 1,320 ft. constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion tributary area, likelihood of problem, overflow pathways, potential impacts Threshold Discharge Area #2TDA #2Threshold Discharge Area #2Cedar River/ Lake Washington (WRIA8)May Creek Reach 1Sheet FlowDense Vegetation5-100 ftNone ObservedReach 2SwaleShort Lawn2-4695 ftGarage/Debris in Swale could cause downstream blockage Garbage/DebrisNone Observed753 ft-58 Feet12" Conc. PipeReach 3None Observed835 ft-82 Feet12" Conc. PipeReach 4None Observed1,103 ft3.4220 Feet12" Conc. PipeReach 5None Observed1,402 ft1.3229 Feet12" Conc. PipeReach 6 APPENDIX C – BOND QUANTITIES WORKSHEETS/COST DATA AND INVENTORY Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430‐7200••Section I: Project Information•••Section II: Bond Quantities Worksheets•• Section II.a EROSION CONTROL (Stabilization/Erosion Sediment Control (ESC))• Section II.b TRANSPORTATION (Street and Site Improvements)• Section II.c DRAINAGE (Drainage and Stormwater Facilities): • Section II.d WATER ‐ONLY APPLICABLE IF WATER SERVICE IS PROVIDED BY CITY OF RENTON• Section II.e SANITARY SEWER ‐ ONLY APPLICABLE IF SEWER SERVICE IS PROVIDED BY CITY OF RENTON••••••Section III. Bond Worksheet•BOND QUANTITY WORKSHEET INSTRUCTIONSThis worksheet is intended to be a "working" copy of the bond quantity worksheet, which will be used throughout all phases of the project, from initial submittal to project close‐out approval. Submit this workbook, in its entirety, as follows:The following forms are to be completed by the engineer/developer/applicant as applicable to the project: The Bond Worksheet form will auto‐calculate and auto‐populate from the information provided in Section I and Section II.This section includes all pertinent information for the projectSection II contains a separate spreadsheet TAB for each of the following specialties: (1) electronic copy and (2) hard copies of the entire workbook for civil construction permit submittal. Hard copies are to be included as part of the Technical Information Report (TIR).(1) electronic copy and (1) hard copy of the entire workbook for final close‐out submittal.This section must be completed in its entiretyInformation from this section auto‐populates to all other relevant areas of the workbookThis section calculates the required Permit Bond for construction permit issuance as well as the required Maintenance Bond for project close‐out submittals to release the permit bond on a project. All unit prices include labor, equipment, materials, overhead and profit. Complete the 'Quantity' columns for each of the appropriate section(s). Include existing Right‐of‐Way (ROW), Future Public Improvements and Private Improvements.The 'Quantity Remaining' column is only to be used when a project is under construction. The City allows one (1) bond reduction during the life of the project with the exception of the maintenance period reduction.Excel will auto‐calculate and auto‐populate the relevant fields and subtotals throughout the document. Only the 'Quantity' columns should need completing.Additional items not included in the lists can be added under the "write‐in" sections. Provide a complete description, cost estimate and unit of measure for each write‐in item. Note: Private improvements, with the exception of stormwater facilities, are not included in the bond amount calculation, but must be entered on the form. Stormwater facilities (public and private) are required to be included in the bond amount.Page 1 of 14Ref 8‐H Bond Quantity WorksheetINSTRUCTIONSUnit Prices Updated: 03/2016Version: 06/2016Printed 6/1/2017 Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430‐7200Date Prepared: Name:PE Registration No:Firm Name:Firm Address:Phone No.Email Address:Project Name: Project Owner:CED Plan # (LUA): Phone:CED Permit # (U):Address: Site Address:Street Intersection: Addt'l Project Owner:Parcel #(s): Phone:Address: Clearing and grading greater than or equal to 5,000 board feet of timber? Yes/No:NOWater Service Provided by:If Yes, Provide Forest Practice Permit #:Sewer Service Provided by: Abbreviated Legal Description:THE EAST HALF OF THE SOUTHWEST QUARTER OF THE NORTHWEST QUARTER OF SECTION 10, TOWNSHIP 23 NORTH, RANGE 5 EAST, WILLAMETTE MERIDIAN, IN KING COUNTY, WASHINGTON;EXCEPT THE SOUTH 200 FEET; AND1012 Duvall Avenue NE Renton, WA 98059845 106th Ave, Suite 200NE 10th Street & Duvall Ave NE########206‐715‐98266/1/2017Prepared by:FOR APPROVALProject Phase 1Brandon@BeylerConsulting.comBrandon Loucks50085Beyler Consulting LLC7602 Bridgeport Way W, STE D Lakewood, WA 98253‐301‐4157SITE IMPROVEMENT BOND QUANTITY WORKSHEETPROJECT INFORMATIONCITY OF RENTONCITY OF RENTON1 Select the current project status/phase from the following options: For Approval ‐ Preliminary Data Enclosed, pending approval from the City; For Construction ‐ Estimated Data Enclosed, Plans have been approved for contruction by the City; Project Closeout ‐ Final Costs and Quantities Enclosed for Project Close‐out SubmittalEngineer Stamp Required (all cost estimates must have original wet stamp and signature)Clearing and Grading Utility ProvidersN/AProject Location and Description Project Owner InformationBoun Short PlatBellevue, WA 98004102305‐9139Kent Khnor ‐ Warring Properties16‐000124, SHPL‐APage 2 of 14Ref 8‐H Bond Quantity WorksheetSECTION I PROJECT INFORMATIONUnit Prices Updated: 06/14/2016Version: 06/14/2016Printed 6/1/2017the city bond quantity worksheet has been updated to account for the recent sales taxincrease and other miscellaneous items. please download it here:https://edocs.rentonwa.gov/Documents/0/edoc/883098/Bond%20Quantity%20Worksheet.xlsx. confirm bond quantities with plan updates. CED Permit #:########UnitReference # Price Unit Quantity CostBackfill & compaction‐embankmentESC‐16.50$ CYCheck dams, 4" minus rockESC‐2SWDM 5.4.6.380.00$ EachCatch Basin ProtectionESC‐335.50$ Each 10355.00Crushed surfacing 1 1/4" minusESC‐4WSDOT 9‐03.9(3)95.00$ CYDitchingESC‐59.00$ CYExcavation‐bulkESC‐62.00$ CY 15483,096.00Fence, siltESC‐7SWDM 5.4.3.11.50$ LF 480720.00Fence, Temporary (NGPE)ESC‐81.50$ LFGeotextile FabricESC‐92.50$ SYHay Bale Silt TrapESC‐100.50$ EachHydroseedingESC‐11SWDM 5.4.2.40.80$ SYInterceptor Swale / DikeESC‐121.00$ LFJute MeshESC‐13SWDM 5.4.2.23.50$ SYLevel SpreaderESC‐141.75$ LFMulch, by hand, straw, 3" deepESC‐15SWDM 5.4.2.12.50$ SYMulch, by machine, straw, 2" deepESC‐16SWDM 5.4.2.12.00$ SYPiping, temporary, CPP, 6"ESC‐1712.00$ LFPiping, temporary, CPP, 8"ESC‐1814.00$ LFPiping, temporary, CPP, 12"ESC‐1918.00$ LFPlastic covering, 6mm thick, sandbaggedESC‐20SWDM 5.4.2.34.00$ SYRip Rap, machine placed; slopesESC‐21WSDOT 9‐13.1(2)45.00$ CY 4180.00Rock Construction Entrance, 50'x15'x1'ESC‐22SWDM 5.4.4.11,800.00$ EachRock Construction Entrance, 100'x15'x1'ESC‐23SWDM 5.4.4.13,200.00$ Each 13,200.00Sediment pond riser assemblyESC‐24SWDM 5.4.5.22,200.00$ EachSediment trap, 5' high berm ESC‐25SWDM 5.4.5.119.00$ LF 24456.00Sed. trap, 5' high, riprapped spillway berm section ESC‐26SWDM 5.4.5.170.00$ LF 302,100.00Seeding, by handESC‐27SWDM 5.4.2.41.00$ SYSodding, 1" deep, level groundESC‐28SWDM 5.4.2.58.00$ SYSodding, 1" deep, sloped groundESC‐29SWDM 5.4.2.510.00$ SYTESC SupervisorESC‐30110.00$ HR 4440.00Water truck, dust controlESC‐31SWDM 5.4.7140.00$ HR 2280.00UnitReference # Price Unit Quantity CostEROSION/SEDIMENT SUBTOTAL: 10,827.00SALES TAX @ 9.5% 1,028.57EROSION/SEDIMENT TOTAL: 11,855.57(A)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR EROSION & SEDIMENT CONTROLDescription No.(A)WRITE‐IN‐ITEMS Page 3 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.a EROSION_CONTROLUnit Prices Updated: 06/14/2016Version: 06/14/2016Printed 6/1/2017 CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostGENERAL ITEMS Backfill & Compaction‐ embankment GI‐1 6.00$ CYBackfill & Compaction‐ trench GI‐2 9.00$ CY 2502,250.003002,700.00Clear/Remove Brush, by hand (SY) GI‐3 1.00$ SYBollards ‐ fixed GI‐4 240.74$ EachBollards ‐ removable GI‐5 452.34$ EachClearing/Grubbing/Tree Removal GI‐6 10,000.00$ Acre 0.22,000.001.212,000.00Excavation ‐ bulk GI‐7 2.00$ CYExcavation ‐ Trench GI‐8 5.00$ CY 2501,250.003001,500.00Fencing, cedar, 6' high GI‐9 20.00$ LFFencing, chain link, 4' GI‐10 38.31$ LFFencing, chain link, vinyl coated, 6' high GI‐11 20.00$ LFFencing, chain link, gate, vinyl coated, 20' GI‐12 1,400.00$ EachFill & compact ‐ common barrow GI‐13 25.00$ CYFill & compact ‐ gravel base GI‐14 27.00$ CYFill & compact ‐ screened topsoil GI‐15 39.00$ CYGabion, 12" deep, stone filled mesh GI‐16 65.00$ SYGabion, 18" deep, stone filled mesh GI‐17 90.00$ SYGabion, 36" deep, stone filled mesh GI‐18 150.00$ SYGrading, fine, by hand GI‐19 2.50$ SYGrading, fine, with grader GI‐20 2.00$ SY 641012,820.00Monuments, 3' Long GI‐21 250.00$ EachSensitive Areas Sign GI‐22 7.00$ EachSodding, 1" deep, sloped ground GI‐23 8.00$ SYSurveying, line & grade GI‐24 850.00$ Day 21,700.0054,250.0032,550.00Surveying, lot location/lines GI‐25 1,800.00$ Acre 0.2360.001.22,160.00Topsoil Type A (imported) GI‐26 28.50$ CYTraffic control crew ( 2 flaggers ) GI‐27 120.00$ HRTrail, 4" chipped wood GI‐28 8.00$ SYTrail, 4" crushed cinder GI‐29 9.00$ SYTrail, 4" top course GI‐30 12.00$ SYConduit, 2" GI‐31 5.00$ LF 2001,000.00Wall, retaining, concrete GI‐32 55.00$ SFWall, rockery GI‐33 15.00$ SF 1752,625.00SUBTOTAL THIS PAGE:6,200.00 10,810.00 32,155.00(B)(C)(D)(E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B) (C)Page 4 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 06/14/2016Printed 6/1/2017 CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B) (C)ROAD IMPROVEMENT/PAVEMENT/SURFACINGAC Grinding, 4' wide machine < 1000sy RI‐1 30.00$ SYAC Grinding, 4' wide machine 1000‐2000sy RI‐2 16.00$ SYAC Grinding, 4' wide machine > 2000sy RI‐3 10.00$ SYAC Removal/Disposal RI‐4 35.00$ SY 501,750.00Barricade, Type III ( Permanent ) RI‐5 56.00$ LF 12672.00Guard Rail RI‐6 30.00$ LFCurb & Gutter, rolled RI‐7 17.00$ LFCurb & Gutter, vertical RI‐8 12.50$ LF 2503,125.00Curb and Gutter, demolition and disposal RI‐9 18.00$ LF 50900.00Curb, extruded asphalt RI‐10 5.50$ LFCurb, extruded concrete RI‐11 7.00$ LFSawcut, asphalt, 3" depth RI‐12 1.85$ LF 210388.50Sawcut, concrete, per 1" depth RI‐13 3.00$ LFSealant, asphalt RI‐14 2.00$ LF 210420.00Shoulder, gravel, 4" thick RI‐15 15.00$ SYSidewalk, 4" thick RI‐16 38.00$ SY 2107,980.00Sidewalk, 4" thick, demolition and disposal RI‐17 32.00$ SYSidewalk, 5" thick RI‐18 41.00$ SYSidewalk, 5" thick, demolition and disposal RI‐19 40.00$ SYSign, Handicap RI‐20 85.00$ EachStriping, per stall RI‐21 7.00$ EachStriping, thermoplastic, ( for crosswalk ) RI‐22 3.00$ SFStriping, 4" reflectorized line RI‐23 0.50$ LFAdditional 2.5" Crushed Surfacing RI‐24 3.60$ SY 50180.00HMA 1/2" Overlay 1.5" RI‐25 14.00$ SYHMA 1/2" Overlay 2" RI‐26 18.00$ SYHMA Road, 2", 4" rock, First 2500 SY RI‐27 28.00$ SYHMA Road, 2", 4" rock, Qty. over 2500SY RI‐28 21.00$ SYHMA Road, 4", 6" rock, First 2500 SY RI‐29 45.00$ SY 27012,150.0065029,250.00HMA Road, 4", 6" rock, Qty. over 2500 SY RI‐30 37.00$ SYHMA Road, 4", 4.5" ATB RI‐31 38.00$ SYGravel Road, 4" rock, First 2500 SY RI‐32 15.00$ SYGravel Road, 4" rock, Qty. over 2500 SY RI‐33 10.00$ SYThickened Edge RI‐34 8.60$ LF 1301,118.00SUBTOTAL THIS PAGE:26,713.50 31,040.00 180.00(B)(C)(D)(E)Page 5 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 06/14/2016Printed 6/1/2017 CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostSITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR STREET AND SITE IMPROVEMENTSQuantity Remaining (Bond Reduction) (B) (C)PARKING LOT SURFACING No.2" AC, 2" top course rock & 4" borrow PL‐1 21.00$ SY2" AC, 1.5" top course & 2.5" base course PL‐2 28.00$ SY4" select borrow PL‐3 5.00$ SY1.5" top course rock & 2.5" base course PL‐4 14.00$ SYSUBTOTAL PARKING LOT SURFACING:(B)(C)(D)(E)LANDSCAPING & VEGETATION No.Street Trees LA‐1 225.00$ Each 61,350.00173,825.00Median Landscaping LA‐2 35.00$ Each 632,205.00Right‐of‐Way Landscaping LA‐3Wetland Landscaping LA‐4SUBTOTAL LANDSCAPING & VEGETATION:1,350.00 6,030.00(B)(C)(D)(E)TRAFFIC & LIGHTING No.Signs TR‐1Street Light System ( # of Poles) TR‐2 2,000.00$ Each 24,000.00Traffic Signal TR‐3Traffic Signal Modification TR‐4SUBTOTAL TRAFFIC & LIGHTING:4,000.00(B)(C)(D)(E)WRITE‐IN‐ITEMSSUBTOTAL WRITE‐IN ITEMS:STREET AND SITE IMPROVEMENTS SUBTOTAL: 38,263.50 41,850.00 38,365.00SALES TAX @ 9.5% 3,635.03 3,975.75 3,644.68STREET AND SITE IMPROVEMENTS TOTAL: 41,898.53 45,825.75 42,009.68(B)(C)(D)(E)Page 6 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.b TRANSPORTATIONUnit Prices Updated: 06/14/2016Version: 06/14/2016Printed 6/1/2017 CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostDRAINAGE (CPE = Corrugated Polyethylene Pipe, N12 or Equivalent) For Culvert prices, Average of 4' cover was assumed. Assume perforated PVC is same price as solid pipe.) Access Road, R/D D‐1 26.00$ SY 481,248.00* (CBs include frame and lid)Beehive D‐2 90.00$ EachThrough‐curb Inlet Framework D‐3 400.00$ EachCB Type I D‐4 1,500.00$ Each 710,500.0011,500.00CB Type IL D‐5 1,750.00$ EachCB Type II, 48" diameter D‐6 2,300.00$ Each 12,300.0024,600.0012,300.00 for additional depth over 4' D‐7 480.00$ FT 157,200.00125,760.0083,840.00CB Type II, 54" diameter D‐8 2,500.00$ Each for additional depth over 4' D‐9 495.00$ FTCB Type II, 60" diameter D‐10 2,800.00$ Each 12,800.00 for additional depth over 4' D‐11 600.00$ FT 21,200.00CB Type II, 72" diameter D‐12 6,000.00$ Each for additional depth over 4' D‐13 850.00$ FTCB Type II, 96" diameter D‐14 14,000.00$ Each for additional depth over 4' D‐15 925.00$ FTTrash Rack, 12" D‐16 350.00$ Each 1350.00Trash Rack, 15" D‐17 410.00$ EachTrash Rack, 18" D‐18 480.00$ EachTrash Rack, 21" D‐19 550.00$ EachCleanout, PVC, 4" D‐20 150.00$ EachCleanout, PVC, 6" D‐21 170.00$ Each 71,190.00Cleanout, PVC, 8" D‐22 200.00$ EachCulvert, PVC, 4" (Not allowed in ROW)D‐23 10.00$ LFCulvert, PVC, 6" (Not allowed in ROW)D‐24 13.00$ LF 2002,600.00Culvert, PVC, 8" (Not allowed in ROW)D‐25 15.00$ LFCulvert, PVC, 12" (Not allowed in ROW)D‐26 23.00$ LFCulvert, PVC, 15" (Not allowed in ROW)D‐27 35.00$ LFCulvert, PVC, 18" (Not allowed in ROW)D‐28 41.00$ LFCulvert, PVC, 24" (Not allowed in ROW)D‐29 56.00$ LFCulvert, PVC, 30" (Not allowed in ROW)D‐30 78.00$ LFCulvert, PVC, 36" (Not allowed in ROW)D‐31 130.00$ LFCulvert, CMP, 8" D‐32 19.00$ LFCulvert, CMP, 12" D‐33 29.00$ LFSUBTOTAL THIS PAGE:24,350.00 13,050.00 9,988.00(B) (C) (D) (E)Quantity Remaining (Bond Reduction) (B) (C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESPage 7 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 06/14/2016Printed 6/1/2017 CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostQuantity Remaining (Bond Reduction) (B) (C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESDRAINAGE (Continued)Culvert, CMP, 15" D‐34 35.00$ LFCulvert, CMP, 18" D‐35 41.00$ LFCulvert, CMP, 24" D‐36 56.00$ LFCulvert, CMP, 30" D‐37 78.00$ LFCulvert, CMP, 36" D‐38 130.00$ LFCulvert, CMP, 48" D‐39 190.00$ LFCulvert, CMP, 60" D‐40 270.00$ LFCulvert, CMP, 72" D‐41 350.00$ LFCulvert, Concrete, 8" D‐42 42.00$ LFCulvert, Concrete, 12" D‐43 48.00$ LFCulvert, Concrete, 15" D‐44 78.00$ LFCulvert, Concrete, 18" D‐45 48.00$ LFCulvert, Concrete, 24" D‐46 78.00$ LFCulvert, Concrete, 30" D‐47 125.00$ LFCulvert, Concrete, 36" D‐48 150.00$ LFCulvert, Concrete, 42" D‐49 175.00$ LFCulvert, Concrete, 48" D‐50 205.00$ LFCulvert, CPE, 6" (Not allowed in ROW)D‐51 14.00$ LFCulvert, CPE, 8" (Not allowed in ROW)D‐52 16.00$ LFCulvert, CPE, 12" (Not allowed in ROW)D‐53 24.00$ LFCulvert, CPE, 15" (Not allowed in ROW)D‐54 35.00$ LFCulvert, CPE, 18" (Not allowed in ROW)D‐55 41.00$ LFCulvert, CPE, 24" (Not allowed in ROW)D‐56 56.00$ LFCulvert, CPE, 30" (Not allowed in ROW)D‐57 78.00$ LFCulvert, CPE, 36" (Not allowed in ROW)D‐58 130.00$ LFCulvert, LCPE, 6" D‐59 60.00$ LFCulvert, LCPE, 8" D‐60 72.00$ LFCulvert, LCPE, 12" D‐61 84.00$ LFCulvert, LCPE, 15" D‐62 96.00$ LFCulvert, LCPE, 18" D‐63 108.00$ LFCulvert, LCPE, 24" D‐64 120.00$ LFCulvert, LCPE, 30" D‐65 132.00$ LFCulvert, LCPE, 36" D‐66 144.00$ LFCulvert, LCPE, 48" D‐67 156.00$ LFCulvert, LCPE, 54" D‐68 168.00$ LFSUBTOTAL THIS PAGE:(B) (C) (D) (E)Page 8 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 06/14/2016Printed 6/1/2017 CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostQuantity Remaining (Bond Reduction) (B) (C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESDRAINAGE (Continued)Culvert, LCPE, 60" D‐69 180.00$ LFCulvert, LCPE, 72" D‐70 192.00$ LFCulvert, HDPE, 6" D‐71 42.00$ LFCulvert, HDPE, 8" D‐72 42.00$ LFCulvert, HDPE, 12" D‐73 74.00$ LFCulvert, HDPE, 15" D‐74 106.00$ LFCulvert, HDPE, 18" D‐75 138.00$ LFCulvert, HDPE, 24" D‐76 221.00$ LFCulvert, HDPE, 30" D‐77 276.00$ LFCulvert, HDPE, 36" D‐78 331.00$ LFCulvert, HDPE, 48" D‐79 386.00$ LFCulvert, HDPE, 54" D‐80 441.00$ LFCulvert, HDPE, 60" D‐81 496.00$ LFCulvert, HDPE, 72" D‐82 551.00$ LFPipe, Polypropylene, 6" D‐83 84.00$ LFPipe, Polypropylene, 8" D‐84 89.00$ LFPipe, Polypropylene, 12" D‐85 95.00$ LF 13512,825.0022020,900.00Pipe, Polypropylene, 15" D‐86 100.00$ LFPipe, Polypropylene, 18" D‐87 106.00$ LFPipe, Polypropylene, 24" D‐88 111.00$ LFPipe, Polypropylene, 30" D‐89 119.00$ LFPipe, Polypropylene, 36" D‐90 154.00$ LFPipe, Polypropylene, 48" D‐91 226.00$ LFPipe, Polypropylene, 54" D‐92 332.00$ LFPipe, Polypropylene, 60" D‐93 439.00$ LFPipe, Polypropylene, 72" D‐94 545.00$ LFCulvert, DI, 6" D‐95 61.00$ LFCulvert, DI, 8" D‐96 84.00$ LFCulvert, DI, 12" D‐97 106.00$ LFCulvert, DI, 15" D‐98 129.00$ LFCulvert, DI, 18" D‐99 152.00$ LFCulvert, DI, 24" D‐100 175.00$ LFCulvert, DI, 30" D‐101 198.00$ LFCulvert, DI, 36" D‐102 220.00$ LFCulvert, DI, 48" D‐103 243.00$ LFCulvert, DI, 54" D‐104 266.00$ LFCulvert, DI, 60" D‐105 289.00$ LFCulvert, DI, 72" D‐106 311.00$ LFSUBTOTAL THIS PAGE:12,825.00 20,900.00(B) (C) (D) (E)Page 9 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 06/14/2016Printed 6/1/2017 CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostQuantity Remaining (Bond Reduction) (B) (C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESSpecialty Drainage ItemsDitching SD‐1 9.50$ CYFlow Dispersal Trench (1,436 base+) SD‐3 28.00$ LF French Drain (3' depth) SD‐4 26.00$ LFGeotextile, laid in trench, polypropylene SD‐5 3.00$ SYMid‐tank Access Riser, 48" dia, 6' deep SD‐6 2,000.00$ EachPond Overflow Spillway SD‐7 16.00$ SYRestrictor/Oil Separator, 12" SD‐8 1,150.00$ EachRestrictor/Oil Separator, 15" SD‐9 1,350.00$ EachRestrictor/Oil Separator, 18" SD‐10 1,700.00$ EachRiprap, placed SD‐11 42.00$ CY 8336.00Tank End Reducer (36" diameter) SD‐12 1,200.00$ EachInfiltration pond testing SD‐13 125.00$ HRPermeable Pavement SD‐14Permeable Concrete Sidewalk SD‐15Culvert, Box __ ft x __ ft SD‐16SUBTOTAL SPECIALTY DRAINAGE ITEMS:336.00(B) (C) (D) (E)STORMWATER FACILITIES (Include Flow Control and Water Quality Facility Summary Sheet and Sketch)Detention Pond SF‐1 Each Detention Tank SF‐2 Each Detention Vault SF‐3 65,000.00$ Each 165,000.00Infiltration Pond SF‐4 Each Infiltration Tank SF‐5 Each Infiltration Vault SF‐6 Each Infiltration Trenches SF‐7 Each Basic Biofiltration Swale SF‐8 Each Wet Biofiltration Swale SF‐9 Each Wetpond SF‐10 Each Wetvault SF‐11 37,000.00$ Each 137,000.00Sand Filter SF‐12 Each Sand Filter Vault SF‐13 Each Linear Sand Filter SF‐14 Each StormFilter SF‐15 Each Rain Garden SF‐16 Each SUBTOTAL STORMWATER FACILITIES:102,000.00(B) (C) (D) (E)Page 10 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 06/14/2016Printed 6/1/2017 CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostQuantity Remaining (Bond Reduction) (B) (C)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR DRAINAGE AND STORMWATER FACILITIESWRITE‐IN‐ITEMSWI‐1WI‐2WI‐3WI‐4WI‐5WI‐6WI‐7WI‐8WI‐9WI‐10WI‐11WI‐12WI‐13WI‐14WI‐15SUBTOTAL WRITE‐IN ITEMS:DRAINAGE AND STORMWATER FACILITIES SUBTOTAL: 24,686.00 13,050.00 111,988.00SALES TAX @ 9.5% 2,345.17 1,239.75 10,638.86DRAINAGE AND STORMWATER FACILITIES TOTAL: 27,031.17 14,289.75 122,626.86(B) (C) (D) (E)Page 11 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.c DRAINAGEUnit Prices Updated: 06/14/2016Version: 06/14/2016Printed 6/1/2017 CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostConnection to Existing Watermain W‐1 2,000.00$ Each 36,000.00Ductile Iron Watermain, CL 52, 4 Inch Diameter W‐2 50.00$ LFDuctile Iron Watermain, CL 52, 6 Inch Diameter W‐3 56.00$ LFDuctile Iron Watermain, CL 52, 8 Inch Diameter W‐4 60.00$ LF 19411,640.0021112,660.00Ductile Iron Watermain, CL 52, 10 Inch Diameter W‐5 70.00$ LFDuctile Iron Watermain, CL 52, 12 Inch Diameter W‐6 80.00$ LFGate Valve, 4 inch Diameter W‐7 500.00$ EachGate Valve, 6 inch Diameter W‐8 700.00$ Each 1700.00Gate Valve, 8 Inch Diameter W‐9 800.00$ Each 32,400.0021,600.00Gate Valve, 10 Inch Diameter W‐10 1,000.00$ EachGate Valve, 12 Inch Diameter W‐11 1,200.00$ EachFire Hydrant Assembly W‐12 4,000.00$ Each 14,000.00Permanent Blow‐Off Assembly W‐13 1,800.00$ Each 11,800.0011,800.00Air‐Vac Assembly, 2‐Inch Diameter W‐14 2,000.00$ EachAir‐Vac Assembly, 1‐Inch Diameter W‐15 1,500.00$ EachCompound Meter Assembly 3‐inch Diameter W‐16 8,000.00$ EachCompound Meter Assembly 4‐inch Diameter W‐17 9,000.00$ EachCompound Meter Assembly 6‐inch Diameter W‐18 10,000.00$ EachPressure Reducing Valve Station 8‐inch to 10‐inch W‐19 20,000.00$ EachWATER SUBTOTAL:21,840.00 20,760.00SALES TAX @ 9.5% 2,074.80 1,972.20WATER TOTAL: 23,914.80 22,732.20(B) (C) (D) (E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR WATERQuantity Remaining (Bond Reduction) (B) (C)Page 12 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.d WATERUnit Prices Updated: 06/14/2016Version: 06/14/2016Printed 6/1/2017 CED Permit #:########Existing Future Public PrivateRight‐of‐Way Improvements Improvements(D) (E)Description No. Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Quant. CostClean Outs SS‐1 1,000.00$ Each 77,000.00Grease Interceptor, 500 gallon SS‐2 8,000.00$ EachGrease Interceptor, 1000 gallon SS‐3 10,000.00$ EachGrease Interceptor, 1500 gallon SS‐4 15,000.00$ EachSide Sewer Pipe, PVC. 4 Inch Diameter SS‐5 80.00$ LFSide Sewer Pipe, PVC. 6 Inch Diameter SS‐6 95.00$ LF 15014,250.00Sewer Pipe, PVC, 8 inch Diameter SS‐7 105.00$ LF 21422,470.00Sewer Pipe, PVC, 12 Inch Diameter SS‐8 120.00$ LFSewer Pipe, DI, 8 inch Diameter SS‐9 115.00$ LFSewer Pipe, DI, 12 Inch Diameter SS‐10 130.00$ LFManhole, 48 Inch Diameter SS‐11 6,000.00$ Each 212,000.00Manhole, 54 Inch Diameter SS‐13 6,500.00$ EachManhole, 60 Inch Diameter SS‐15 7,500.00$ EachManhole, 72 Inch Diameter SS‐17 8,500.00$ EachManhole, 96 Inch Diameter SS‐19 14,000.00$ EachPipe, C‐900, 12 Inch Diameter SS‐21 180.00$ LFOutside Drop SS‐24 1,500.00$ LSInside Drop SS‐25 1,000.00$ LSSewer Pipe, PVC, ____ Inch Diameter SS‐26Lift Station (Entire System) SS‐27 LSSANITARY SEWER SUBTOTAL:55,720.00SALES TAX @ 9.5% 5,293.40SANITARY SEWER TOTAL: 61,013.40(B) (C) (D) (E)SITE IMPROVEMENT BOND QUANTITY WORKSHEETFOR SANITARY SEWERQuantity Remaining (Bond Reduction) (B) (C)Page 13 of 14Ref 8‐H Bond Quantity WorksheetSECTION II.e SANITARY SEWERUnit Prices Updated: 06/14/2016Version: 06/14/2016Printed 6/1/2017 Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430‐7200Date:Name:Project Name: PE Registration No:CED Plan # (LUA):Firm Name:CED Permit # (U):Firm Address:Site Address:Phone No.Parcel #(s):Email Address:Project Phase: Site Restoration/Erosion Sediment Control Subtotal (a) (a)11,855.57$ Existing Right‐of‐Way Improvements Subtotal (b) (b)65,813.33$ Future Public Improvements Subtotal (c) (c)129,571.35$ Stormwater & Drainage Facilities Subtotal (d) (d)163,947.78$ Bond Reduction (Quantity Remaining)2(e) (e)‐$ Site RestorationCivil Construction PermitMaintenance Bond71,866.49$ Bond Reduction2Construction Permit Bond Amount 3Minimum Bond Amount is $10,000.001 Estimate Only ‐ May involve multiple and variable components, which will be established on an individual basis by Development Engineering.2 The City of Renton allows one request only for bond reduction prior to the maintenance period. Reduction of not more than 70% of the original bond amount, provided that the remaining 30% willcover all remaining items to be constructed. 3 Required Bond Amounts are subject to review and modification by Development Engineering.* Note: The word BOND as used in this document means any financial guarantee acceptable to the City of Renton.** Note: All prices include labor, equipment, materials, overhead and profit. R((b)+(c)+(d)) x 150%EST1((b) + (c) + (d)) x 20%‐$ MAINTENANCE BOND */**(after final acceptance of construction)11,855.57$ 65,813.33$ 538,998.69$ 17,783.35$ ‐$ 129,571.35$ 163,947.78$ S(e) x 150%SITE IMPROVEMENT BOND QUANTITY WORKSHEET BOND CALCULATIONS6/1/2017Brandon Loucks50085Beyler Consulting LLCT(P +R ‐ S)Prepared by:Project InformationCONSTRUCTION BOND AMOUNT */**(prior to permit issuance)253‐301‐4157Brandon@BeylerConsulting.comBoun Short Plat16‐000124, SHPL‐A1012 Duvall Avenue NE Renton, WA 98059102305‐9139FOR APPROVAL########7602 Bridgeport Way W, STE D Lakewood, WA 98335556,782.04$ P (a) x 150%Page 14 of 14Ref 8‐H Bond Quantity WorksheetSECTION III. BOND WORKSHEETUnit Prices Updated: 06/14/2016Version: 06/14/2016Printed 6/1/2017 APPENDIX D – GEOTECHNIAL REPORT ________________________________________________ 3213 Eastlake Avenue E Ste. B Seattle, WA 98102 Tel: (206) 262-0370 Geotechnical & Earthquake Engineering Consultants October 12, 2015 PanGEO Project No. 07-107.200 Mr. Kent Khnor 26721 106th Avenue Kent, WA 98030 Subject: GEOTECHNICAL REPORT Proposed Boon-Phany Short Plat Chelan Avenue NE near NE 10th Street Renton, Washington Dear Mr. Khnor, As requested, PanGEO has completed a geotechnical engineering study for the proposed Boon- Phany short plat planned just north of the intersection of Chelan Avenue NE and NE 10th Street in Renton, Washington. This study was performed in accordance with our mutually agreed scope of work outlined in our proposal dated September 25, 2015. The proposal was subsequently approved by you on September 29, 2015. PanGEO previously completed a geotechnical report for the project site in 2007. Our current scope of work includes reviewing our previous report, conducting a site reconnaissance to confirm the site conditions remain unchanged, and updating the report. SITE AND PROJECT DESCRIPTION The project site is located on the east side of Chelan Avenue NE approximately 170 feet north of the intersection of Chelan Avenue NE and NE 10th Street in Renton, Washington (see Figure 1, Vicinity Map). Review of a preliminary site plan indicates that the vacant 1.32-acre, rectangular site extends approximately 200 feet in a north-south direction and approximately 285 feet in an east-west direction. The site is currently bound to the north by single-family houses and a grass lot, to the south by newly developed 2-story single family residences accessed by Chelan Place NE, to the east by Duvall Avenue NE, and to the west by Chelan Avenue NE which dead ends Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 2 near the northwest corner of the property. The Chelan Avenue NE right-of-way was being was being developed at the time of our field exploration in July, 2007. The northern-central portion of the site is currently occupied by a small shed that will be razed prior to redeveloping the site. The site is primarily vegetated with tall grass, miscellaneous trees and shrubs, and localized areas of blackberry brambles. Based on the topographic survey provided for our review (see Figure 2), much of the site is relatively level except for the approximately southwestern quarter of the site. In general, the southwestern quarter of the site descends to the southwest at gradients in the estimated range of 8 to 10 percent. Overall, there is an approximate elevation difference of 5 feet between the northeastern and southwestern site corners. Due to the relatively level site topography, we anticipate the new buildings will be constructed at or near existing grades. Cuts and fills in the southwestern quarter of the site may be on the order of 2 to 4 feet. As currently planned, the proposed development will create eight single-family residential lots, a stormwater drainage tract, and associated asphalt-paved access roads. We anticipate the buildings will be of lightly loaded wood frame construction with a combination of wood joist and slab-on-grade floors. An east-west trending stormwater drainage tract is planned along the approximately west half of the south property line. We understand that a detention vault may be utilized for stormwater/surfacewater management. Depending on the location and size of the vault, temporary excavations to reach construction elevations may extend off-site to the south and west. As such, it may be necessary to obtain temporary construction easements from the respective neighbor. SUBSURFACE EXPLORATIONS Five test pits (TP-1 to TP-5) were previously excavated on the subject property in 2007. The approximate test pit locations are indicated on Figure 2. A PanGEO geologist was present throughout the field exploration to observe the test pit excavation, to assist in sampling, and to prepare descriptive logs of the explorations. The test pits were excavated on July 23, 2007, using a Cat 330 tracked excavator owned and operated by Northwest Excavating of Mill Creek, WA. The test pits were excavated to depths ranging from 8 to 12 feet below the existing ground surface. The relative density and consistency of the underlying soil was estimated based on probing the walls of the excavation and the difficulty of completing the excavations. The soils Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 3 observed in the test pits were classified in the field, and a summary of the subsurface conditions is presented in Appendix A of this report. SITE GEOLOGY AND SUBSURFACE CONDITIONS Review of the geologic map of the Renton Quadrangle (Mullineaux, 1965) indicated the subject site and its vicinity are underlain by ground moraine deposits (Map Unit Qgt), also known as glacial till. Glacial till is a very dense heterogeneous mixture of silt, sand, and gravel laid down at the base of an advancing glacial ice sheet. Glacial till typically exhibits low compressibility and high strength characteristics. The test pits excavated at the site generally confirmed the mapped stratigraphy. Based on the results of our subsurface explorations, the site is underlain by a surficial layer of loose to medium dense weathered glacial till that extends up to approximately 2½ to 5 feet below existing site grades. The weathered glacial till typically consisted of light brown silty sand with gravel. The weathered till contained occasional cobbles and was generally dry to moist. Underlying the surficial layer of weathered glacial till we encountered dense glacial till, which consisted of silty sand with gravel, to the maximum exploration depth of about 12 feet. The glacial till was typically gray, moist, and contained sandy lenses and occasional cobbles. It should be noted that thin layers of loose existing fill with a varying organic content may be encountered at the site, as evidenced in Test Pit TP-5. Groundwater/seepage was not encountered in the test pits at the time of the excavations. However, iron oxide staining was typically observed near the contact with dense glacial till. The iron oxide stained zone is likely indicative of groundwater collecting above the low permeability glacial till. In addition, limited amounts of groundwater seepage are often present in sandy and gravelly zones of glacial till. It should be noted that groundwater elevations are likely to vary depending on the season, local subsurface conditions, and other factors. Groundwater levels are normally highest during the winter and early spring. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 4 SEISMIC DESIGN CONSIDERATIONS IBC Seismic Design Parameters The following provides seismic design parameters for the site that are in conformance with the 2012 International Building Code (IBC), which specifies a design earthquake having a 2% probability of occurrence in 50 years (return interval of 2,475 years). Based on the subsurface conditions encountered at the test pits, it is our opinion that IBC Site Class C should be used used for seismic design. Table 1 – Summary Seismic Design Parameters per 2012 IBC Site Class Spectral Acceleration at 0.2 sec. (g) SS Spectral Acceleration at 1.0 sec. (g) S1 Site Coefficients Design Spectral Response Parameters Fa Fv SDS SD1 C 1.4 0.529 1.0 1.3 0.937 0.458 Liquefaction Assessment Soil liquefaction is a condition where saturated cohesionless soils undergo a substantial loss of strength due to the build-up of excess pore water pressures resulting from cyclic stress applications induced by earthquakes. Soils most susceptible to liquefaction are loose, uniformly graded sands and loose silts with little cohesion. Due to the presence of dense soils at shallow depths and based on the lack of a shallow groundwater table at the site, the susceptibility of the site to earthquake-induced soil liquefaction is considered to be negligible. Special design considerations associated with soil liquefaction are not necessary for this project. EARTHWORK CONSIDERATIONS Site Preparation Site preparation includes striping and clearing of topsoil and sod, surface vegetation, root balls, existing foundations, and any other deleterious materials within the proposed development area and excavating to the design subgrade. All stripped materials should be properly disposed off-site or be “wasted” on site in non-structural landscaping areas. Based on the thickness of topsoil and Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 5 sod observed at the test pit locations, we estimate stripping depths will be in the range of 4 to 9 inches. Soil disturbed during stripping and clearing activities should be compacted to a firm and unyielding condition. Following the removal of deleterious and unsuitable materials, the exposed subgrade within the development area, such as building foundation, slab, and pavement areas, should be proof-rolled with a fully-loaded dump truck or a smooth roller compactor. The proof-rolling operation should be observed by a representative of PanGEO. If loose or unstable subgrade soils are observed during the proof roll, the soil should be over-excavated and replaced with structural fill. Temporary and Permanent Slopes All temporary excavations should be performed in accordance with Part N of WAC (Washington Administrative Code) 296-155. The contractor is responsible for maintaining safe excavation slopes and/or shoring. Excavations more than 4 feet deep should be properly shored or sloped. For planning purposes, it is our opinion that temporary excavations may be sloped as steep as ¾H:1V (Horizontal:Vertical). The inclination of temporary slopes should be re-evaluated in the field during construction based on actual observed soil conditions. Permanent cut and fill slopes should be graded no steeper than 2H:1V and should promptly be planted with an appropriate species of vegetation. Fill slopes should be constructed using 8- to 12-inch thick lifts with each lift compacted to a dense and unyielding condition prior to placing a subsequent lift. Structural Fill and Compaction In the context of this report, structural fill is defined as non-organic compacted fill placed under buildings, roadways, slabs, pavements, or other load-bearing areas. It may be possible to reuse some of existing site soils for structural backfill during periods of dry weather, provided the soil can be properly moisture conditioned and adequately compacted. However, due to the moderate to high fines content of the on-site soils, the soils should be considered moisture sensitive and generally unsuitable for use during wet weather construction. Imported structural fill, if needed, should consist of well-graded granular soils such as Gravel Borrow (WSDOT 9-03.14(1)), or an approved equivalent. PanGEO should review import material intended for use as structural fill prior to placement. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 6 Structural fill should be moisture conditioned to within about 3 percent of optimum moisture content, placed in loose, horizontal lifts less than 8 inches in thickness, and systematically compacted to a dense and relatively unyielding condition and to at least 95 percent of the maximum dry density, as determined using test method ASTM D 1557 (Modified Proctor). The procedure to achieve proper density of a compacted fill depends on the size and type of compacting equipment, the number of passes, thickness of the layer being compacted, and certain soil properties. When size of the excavation restricts the use of heavy equipment, smaller equipment can be used, but the soil must be placed in thin enough layers to achieve the required degree of compaction. Generally, inadequately compacted soils result from poor workmanship or soils placed at improper moisture content. Soils with a high percentage of silt or clay are particularly susceptible to becoming too wet, and coarse-grained materials easily become too dry for proper compaction. Silty or clayey soils with a moisture content too high for adequate compaction should be dried as necessary, or moisture conditioned by mixing with drier materials. Existing Test Pit Backfill It should be noted that the backfill in the test pits were backfilled with excavated soils and compacted with the excavator bucket. As such, the backfill is considered inadequate for supporting future load-bearing elements, including building foundation, pavements, slabs, underground vaults, buried pipes, etc. As such, where load-bearing elements are present, the existing backfill in the test pits should be removed and replaced with properly compacted structural fill. UTILITIES Trenching Utility trenches greater than 4 feet deep should be properly sloped. Temporary slope recommendations can be found on Page 4 of this report. Alternatively, conventional trench shoring systems such as trench boxes or steel sheets utilizing hydraulic bracing are considered feasible for this project. For shoring design purposes, the contractor may utilize an equivalent fluid weight of 35 pcf to represent the lateral earth pressures on the shoring. This pressure should be increased for backslopes above the shoring or to account for soil stockpiles and/or equipment traffic surcharges within a horizontal distance equal to the depth of the excavation. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 7 Pipe Bedding General recommendations relative to pipe bedding and backfill are presented below.  Pipe bedding material, placement, compaction, and shaping should be in accordance with the project specifications and the pipe manufacturer’s recommendations. As a minimum, the pipe bedding should meet the gradation requirements for Gravel Backfill for Pipe Zone Bedding, Section 9-03.12(3) of the 2014 WSDOT Standard Specifications;  Pipe bedding should be placed on relatively undisturbed native soils, or on compacted fill. If the native subgrades are disturbed, the disturbed material should be removed and replaced with compacted bedding material;  If the trench bottom encounters soft or unsuitable soils, it may be necessary to over- excavate the unsuitable material and backfill with pipe bedding material;  Pipe bedding should provide a firm, uniform cradle for the pipe. We recommend that a minimum 4-inch thickness of bedding material beneath the pipe be provided. Larger thicknesses may be necessary to prevent loosening and softening of the natural soils during pipe placement;  Prior to the placement of the pipe, the pipe bedding should be shaped to fit the lower part of the pipe exterior with reasonable closeness to provide continuous support along the pipe;  Pipe bedding material and/or backfill around the pipe should be placed in layers and tamped to obtain complete contact with the pipe. In areas where a trench box is used, the bedding material should be placed before the trench box is advanced. Trench Backfill In areas supporting pavements, trench backfill should be placed in 8- to 12-inch, loose lifts and compacted using mechanical equipment. If the trench backfill will consist of imported granular structural fill, the backfill should be compacted to at least 90 percent of its maximum dry density, as determined by test method ASTM D1557 (Modified Proctor). The upper 2 feet of backfill should be compacted to at least 95 percent of its laboratory determined maximum dry density. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 8 It is our opinion that the on-site till soils may be considered for use as trench backfill provided the soil can be compacted to the requirements of trench backfill. Because the on-site till soils are moisture sensitive, it may not be feasible to use the on-site soils as trench backfill in wet weather. Where used in structural areas, all trench backfill derived from the on-site soils should be compacted to 95 percent of its maximum dry density as determined by test method ASTM D1557 (Modified Proctor). We also recommend that trenches backfilled with the on-site fill be capped with at least 12 inches of imported granular structural fill. In non-structural areas where settlement of the trench backfill will not affect the use of the area, the trench backfill may be compacted to 85% of the materials maximum dry density. During placement of the initial lifts, the trench backfill should not be bulldozed into the trench or dropped directly on the pipe. Furthermore, heavy vibratory equipment should not be permitted to operate directly over the pipe until a minimum of 2 feet of backfill has been placed above the crown. Boulders and large sized cobbles should be removed from material to be used as trench backfill. PAVEMENT We anticipate that the future traffics in the development will be limited to light passenger-type vehicles. For lightly loaded pavement areas, we suggest a pavement section consisting of 2½- inches of hot-mix asphalt overlying a 4-inch thick layer of crushed surfacing top course (CSTC) or crushed surfacing base course (CSBC), overlying a properly compacted subgrade. The crushed rock base should be compacted to a minimum of 95 % of the materials maximum dry density determined in accordance with ASTM D1557 (Modified Proctor). Prior to placing the crushed rock, the pavement subgrade should be proof rolled using a fully loaded dump truck. The proof roll should be conducted under observation of a PanGEO representative. Any soft soils identified during the proof rolling should be removed and replaced with properly compacted structural fill. BUILDING FOUNDATIONS Based on the subsurface conditions encountered at the site, the new buildings may be supported on conventional spread and continuous footings bearing on competent native soils, or on properly compacted newly placed structural fill. Based on the results of our subsurface exploration, we anticipate competent native soils (glacial till) to be 2½ to 5 feet deep. Any loose soil should be Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 9 compacted to a dense condition. If loose soil cannot be adequately compacted, it should be overexcavated and replaced with a granular structural fill. On site soils should not be used as structural fill below the footings. Allowable Bearing Pressure We recommend that an allowable soil bearing pressure of 2,000 (psf) be used to size the footings. For allowable stress design, the recommended bearing pressure may be increased by one-third for transient loading, such as wind or seismic forces. Footing Embedment For frost heave considerations, exterior footings should be placed at a minimum depth of 18 inches below final exterior grade. Interior spread foundations should be placed at a minimum depth of 12 inches below the top of slab. Estimated Settlement Footings designed and constructed in accordance with the above should experience total settlement of less than one inch and differential settlement less than about ½ inch. Most of the anticipated settlement should occur during construction as dead loads are applied. Lateral Load Resistance Lateral loads on the structure may be resisted by passive earth pressure developed against the embedded near-vertical faces of the foundation system and by frictional resistance developed between the bottom of the foundation and the supporting subgrade soils. For footings bearing on competent native soil or on structural fill, a frictional coefficient of 0.5 may be used to evaluate sliding resistance developed between the concrete and the subgrade soil. Passive soil resistance may be calculated using an equivalent fluid weight of 300 pcf, assuming the footings are backfilled with structural fill. The above values include a factor of safety of 1.5. Unless covered by pavements or slabs, the passive resistance in the upper 12 inches of soil should be neglected. Footing Drain We recommend that a 4-inch diameter, schedule 40 PVC or SDR 35, perforated pipe embedded in pea gravel and wrapped in filter fabric be installed at the base of the perimeter footings to direct collected water to an appropriate outlet. Under no circumstances should roof downspout Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 10 drain lines be connected to the footing drain systems. Roof downspouts must be separately tightlined to an appropriate discharge. Cleanouts should be installed to allow for periodic maintenance of the footing drain and downspout tightline systems. Footing Excavation All footing subgrades should be in a dense, unyielding condition. The adequacy of the footing subgrade should be verified by PanGEO prior to placing forms or reinforcing steel. If the footing subgrade is still loose or yielding after re-compaction, it should be overexcavated down to competent native soil and replaced with structural fill or lean mix concrete. The overexcavation width should extend at least one-half the overexcavation depth beyond the edge of footing. FLOOR SLABS It is our opinion that conventional concrete slab-on-grade floors are appropriate for this site. Depending on the finished floor elevations, the floor slabs may be founded on the native soil compacted in-place to the requirements of structural fill or on newly placed structural fill. Interior concrete slab-on-grade floors should be underlain by a capillary break consisting of at least 4 inches of compacted ¾-inch, clean crushed rock (less than 3 percent fines). The capillary break material should also have no more than 10 percent passing the No. 4 sieve and less than 5 percent by weight of the material passing the U.S. Standard No. 100 sieve. The capillary break should be placed on a subgrade that has been compacted to a dense and unyielding condition. A 10-mil polyethylene vapor barrier should also be placed directly below the slab. RETAINING WALLS Based on our understanding of the current design concept and the lack of significant topographic relief at the site, we do not anticipate the need for retaining walls. However, depending on the final grading plan, short retaining walls may be needed to achieve the design grade. Given the competent foundation soils at the site, various wall types may be considered, including conventional cast-in-place concrete walls, gravity block walls such as Ultra Blocks or gabions, or mechanically stabilized earth (MSE) walls. Selection of wall types will largely depend on the desired aesthetics and cost considerations. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 11 In general, these walls should be designed to resist an active earth pressure of 35 pcf, and a uniform pressure of 7H pounds per square foot (psf) to account for the seismic loading condition, where H is the exposed wall height in feet. Lateral pressures from surface surcharges located within a distance equal to the exposed wall height should be estimated using a lateral pressure coefficient of 0.3 (i.e. the ratio of lateral pressure to vertical pressure). Where applicable, a lateral uniform pressure of 80 psf should be used to account for traffic surcharge. Proper drainage provisions such as weep holes or 4-inch perforated drain pipes should be incorporated into the design and construction of all retaining walls. For the design and construction of retaining wall foundations, the recommendations provided in the Building Foundations section of this report are applicable. INFILTRATION The site is underlain by glacial till at shallow depths. Glacial till is expected to exhibit very poor infiltration characteristics. In general, this soil unit is considered not appropriate for any significant stormwater infiltration. DETENTION VAULT DESIGN PARAMETERS Foundation We anticipate the bottom of the detention vault will be at least 5 feet below existing site grades. As such, dense glacial till is expected to be encountered at the vault foundation level. The detention vault should be supported on dense glacial till and/or granular structural fill. An allowable soil bearing capacity of 4,000 psf may be used for footings bearing on the dense to very dense glacial till and/or granular structural fill. If the vault foundation will straddle cross dense glacial till and granular structural fill, we recommend that the dense till be over-excavated 6 inches and replaced with crushed rock for a uniform support. The 6-inch crush rock should also be placed in the structural fill area. For allowable stress design, the recommended bearing pressure may be increased by one-third for transient loading, such as wind or seismic forces. Total footing settlement of less than one inch is anticipated with differential movement of less than ½ inch. Most of the anticipated settlement should occur during construction as dead loads are applied. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 12 If loose/soft soil is encountered at the vault foundation level, it should be overexcavated down to dense native till soil and replaced with granular structural fill and/or lean mix concrete. Vault foundation subgrade should be observed by a representative of PanGEO, prior to placing forms or rebar, to verify that conditions are as anticipated in this report. Lateral Earth Pressures Detention vault walls should be properly designed to resist the lateral earth pressures exerted by the soils behind the wall. The below grade portions of the walls with level backslopes should be designed for a static lateral earth pressure based upon an equivalent fluid weight of 50 pcf. A uniform lateral pressure of 7H psf should be added to reflect the increase loading for seismic conditions, where H corresponds to the buried depth of the wall. The recommended lateral pressures assume that the backfill behind the wall consists of adequately compacted free draining backfill and a footing drain. The portion of the wall located beneath the drainpipe, if any, should be designed to withstand a lateral pressure of 90 pcf to account for the potential accumulation of water behind the vault walls. Surcharge loads, where present, should also be included in the design of the vault walls. We recommend that a lateral load coefficient of 0.35 be used to compute the lateral pressure on the wall face resulting from surcharge loads located within a horizontal distance of one-half wall height. Lateral Resistance Lateral forces from seismic loading and unbalanced lateral earth pressures may be resisted by a combination of passive earth pressures and by friction acting on the base of the foundations. Passive resistance values may be determined using an equivalent fluid weight of 350 pcf. This value includes a factor of safety of 1.5, assuming the footing is poured against dense native soil or structural fill adjacent to the sides of footing has been compacted. A friction coefficient of 0.5 may be used to determine the frictional resistance at the base of the footings. These values include a factor safety of 1.5. Vault Backfill Vault backfill should consist of free draining granular soils such as Gravel Borrow (WSDOT 9- 03.14(1)). Vault backfill should be moisture conditioned to within about 3 percent of optimum moisture content, placed in loose, horizontal lifts less than 8 inches in thickness, and Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 13 systematically compacted to a dense and relatively unyielding condition and to at least 95 percent of the maximum dry density, as determined using test method ASTM D 1557. Within 5 feet of the wall, the backfill should be compacted to 90 percent of the maximum dry density. Vault Drainage We recommend that a 4-inch diameter, schedule 40 PVC or SDR 35, perforated pipe embedded in pea gravel and wrapped in filter fabric be installed as low on the vault walls as possible to direct collected water to an appropriate outlet. Cleanouts should be installed to allow for periodic maintenance of the footing drain. SURFACE DRAINAGE AND EROSION CONSIDERATIONS Adequate drainage provisions are imperative and we recommend both short and long term drainage measures be incorporated into the project design and construction. Surface runoff can be controlled during construction by careful grading practices. Typically, this includes the construction of shallow, upgrade perimeter ditches or low earthen berms to collect runoff and prevent water from entering the excavation. All collected water should be directed under control to a positive and permanent discharge system. Permanent control of surface water should be incorporated in the final grading design. Adequate surface gradients and drainage systems should be incorporated into the design such that surface runoff is directed away from structures. Potential problems associated with erosion may also be reduced by establishing vegetation within disturbed areas immediately following grading operations. WET SEASON CONSTRUCTION General recommendations relative to earthwork performed in wet weather or in wet conditions are presented below. Because the site soils are considered moisture sensitive due to a relatively high fines content, grading may be difficult and likely more costly during periods of wet weather. If earthworks will be performed during wet weather conditions, we recommend that the following guidelines be incorporated:  Earthwork should be performed in small areas to minimize subgrade exposure to wet weather. Excavation or the removal of unsuitable soil should be followed promptly Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 14 by the placement and compaction of clean structural fill. The size and type of construction equipment used may have to be limited to reduce soil disturbance.  During wet weather, the allowable fines content of the structural fill should be reduced to no more than 5 percent by weight based on the portion passing ¾-inch sieve. The fines should be non-plastic.  The ground surface within the construction area should be graded to promote run-off of surface water and to prevent the ponding of water.  Geotextile silt fences should be strategically located to control erosion and the movement of soil.  Excavation slopes and soils stockpiled on site should also be covered with plastic sheets. Under no circumstances should water be allowed to pond immediately adjacent to paved areas or foundations. All pavement drainage should be directed into conduits which carry runoff away from the pavement into storm drain systems or other appropriate outlets. UNCERTAINTY AND LIMITATIONS We have prepared this report for use by Mr. Kent Khnor and their project team. Recommendations contained in this report are based on a site reconnaissance, a subsurface exploration program, review of pertinent subsurface information, and our understanding of the project. The study was performed using a mutually agreed-upon scope of work. Variations in soil conditions may exist between the locations of the explorations and the actual conditions underlying the site. The nature and extent of soil variations may not be evident until construction occurs. If any soil conditions are encountered at the site that are different from those described in this report, we should be notified immediately to review the applicability of our recommendations. Additionally, we should also be notified to review the applicability of our recommendations if there are any changes in the project scope. The scope of our work does not include services related to construction safety precautions. Our recommendations are not intended to direct the contractors’ methods, techniques, sequences or procedures, except as specifically described in our report for consideration in design. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 15 Additionally, the scope of our work specifically excludes the assessment of environmental characteristics, particularly those involving hazardous substances. We are not mold consultants nor are our recommendations to be interpreted as being preventative of mold development. A mold specialist should be consulted for all mold-related issues. This report may be used only by the client and for the purposes stated, within a reasonable time from its issuance. Land use, site conditions (both off and on-site), or other factors including advances in our understanding of applied science, may change over time and could materially affect our findings. Therefore, this report should not be relied upon after 24 months from its issuance. PanGEO should be notified if the project is delayed by more than 24 months from the date of this report so that we may review the applicability of our conclusions considering the time lapse. It is the client’s responsibility to see that all parties to this project, including the designer, contractor, subcontractors, etc., are made aware of this report in its entirety. The use of information contained in this report for bidding purposes should be done at the contractor’s option and risk. Any party other than the client who wishes to use this report shall notify PanGEO of such intended use and for permission to copy this report. Based on the intended use of the report, PanGEO may require that additional work be performed and that an updated report be reissued. Noncompliance with any of these requirements will release PanGEO from any liability resulting from the use this report. Within the limitation of scope, schedule and budget, PanGEO engages in the practice of geotechnical engineering and endeavors to perform its services in accordance with generally accepted professional principles and practices at the time the Report or its contents were prepared. No warranty, express or implied, is made. We appreciate the opportunity to be of service to you on this project. Please feel free to contact our office with any questions you have regarding our study, this report, or any geotechnical engineering related project issues. We appreciate the opportunity to be of service. Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 16 Sincerely, Bryce C. Townsend, E.I.T. Siew L. Tan, P.E. Staff Geotechnical Engineer Principal Geotechnical Engineer Enclosures: Figure 1 Vicinity Map Figure 2 Site and Exploration Plan Appendix A Summary Test Pit Logs Figure A-1 Terms and Symbols for Boring and Test Pit Logs Logs of Test Pits TP-1 through TP-5 Mr. Kent Khnor Geotechnical Report – Proposed Boon-Phany Short Plat October 12, 2015 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Page 17 REFERENCES International Building Code (IBC), 2012, International Code Council. Mullineaux, D. R., 1965, Geologic Map of The Renton Quadrangle, King County, Washington – Department of the Interior, U.S. Geologic Survey, scale 1:24,000. Washington State Department of Transportation/American Public Works Association, 2014, Standard Specifications for Road, Bridges, and Municipal Construction. 07-107.200 Boon-Phanny Short Plat Chelan Ave. NE near NE 10th St. Renton, Washington 1 VICINITY MAP Figure 1.grf 10/12/15 (9:48 ) Note: Base map obtained and modified from Google Maps. Not to Scale Figure No.Project No. Project Location Project No. Figure No.Boon-Phanny Short PlatChelan Ave. NE near NE 10th St. Renton, WashingtonSITE AND EXPLORATION PLAN07-107.200207-107 Boon-Phanny Short Plat Site Plan.grf 10/12/15 STSApprox. Test Pit Location(July, 2007)Legend:Approx. Scale1" = 50'Note:Preliminary site plan provided by client.Subject SiteTP-2TP-3TP-4TP-5TP-1432 4 33 4 34435436437 43 8437 438 ________________________________________________ 3213 Eastlake Avenue E Ste. B Seattle, WA 98102 Tel: (206) 262-0370 APPENDIX A SUMMARY TEST PIT LOGS MOISTURE CONTENT Layered: Laminated: Lens: Interlayered: Pocket: Homogeneous: Gravel Approx. RelativeDensity (%) Units of material distinguished by color and/orcomposition from material units above and below Layers of soil typically 0.05 to 1mm thick, max. 1 cm Layer of soil that pinches out laterally Alternating layers of differing soil material Erratic, discontinuous deposit of limited extent Soil with uniform color and composition throughout GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT <15 15 - 35 35 - 65 65 - 85 85 - 100 MONITORING WELL Highly Organic Soils Notes: GROUP DESCRIPTIONSMAJOR DIVISIONS UNIFIED SOIL CLASSIFICATION SYSTEM #4 to #10 sieve (4.5 to 2.0 mm) #10 to #40 sieve (2.0 to 0.42 mm) #40 to #200 sieve (0.42 to 0.074 mm) 0.074 to 0.002 mm <0.002 mm Liquid Limit < 50 Liquid Limit > 50 GRAVEL (<5% fines) GRAVEL (>12% fines) SAND (<5% fines) SAND (>12% fines) SILT / CLAY Terms and Symbols for Boring and Test Pit Logs Dusty, dry to the touch Damp but no visible water Visible free water 2-inch OD Split Spoon, SPT (140-lb. hammer, 30" drop) 3.25-inch OD Spilt Spoon (300-lb hammer, 30" drop) Non-standard penetration test (see boring log for details) Thin wall (Shelby) tube Grab Rock core Vane Shear Density Approx. Undrained ShearStrength (psf)California Bearing Ratio Compaction Tests Consolidation Dry Density Direct Shear Fines Content Grain Size Permeability Pocket Penetrometer R-value Specific Gravity Torvane Triaxial Compression Unconfined Compression <4 4 to 10 10 to 30 30 to 50 >50 SPTN-values Very Loose Loose Med. Dense Dense Very Dense Breaks along defined planes Fracture planes that are polished or glossy Angular soil lumps that resist breakdown Soil that is broken and mixed Less than one per foot More than one per foot Angle between bedding plane and a planenormal to core axis SPTN-values <2 2 to 4 4 to 8 8 to 15 15 to 30 >30 Sand Coarse Sand: Medium Sand: Fine Sand: Silt Clay Boulder: Cobbles: Gravel Coarse Gravel: Fine Gravel: CBR Comp Con DD DS %F GS Perm PP R SG TV TXC UCC Phone: 206.262.0370 Sand Very Soft Soft Med. Stiff Stiff Very Stiff Hard Bottom of Boring Well-graded GRAVEL Poorly-graded GRAVEL Silty GRAVEL Clayey GRAVEL Well-graded SAND Poorly-graded SAND Silty SAND Clayey SAND SILT Lean CLAY Organic SILT or CLAY Elastic SILT Fat CLAY Organic SILT or CLAY PEAT DESCRIPTIONS OF SOIL STRUCTURES 50% or more of the coarsefraction retained on the #4sieve. Use dual symbols (eg.GP-GM) for 5% to 12% fines. > 12 inches 3 to 12 inches 3 to 3/4 inches 3/4 inches to #4 sieve Figure A-1 50% or more of the coarsefraction passing the #4 sieve.Use dual symbols (eg. SP-SM)for 5% to 12% fines. for In Situ and Laboratory Testslisted in "Other Tests" column. <250 250 - 500 500 - 1000 1000 - 2000 2000 - 4000 >4000 Dry Moist Wet COMPONENT DEFINITIONS Fissured: Slickensided: Blocky: Disrupted: Scattered: Numerous: BCN: RELATIVE DENSITY / CONSISTENCY COMPONENT SIZE / SIEVE RANGE Groundwater Level at time of drilling (ATD)Static Groundwater Level Cement / Concrete Seal Bentonite grout / seal Silica sand backfill Slotted tip Slough 50%or more passing #200 sieve LOG KEY 07-041_EVERETT_AS.GPJ PANGEO.GDT 5/1/07SYMBOLS SAND / GRAVEL Consistency Silt and Clay Sample/In Situ test types and intervals 1. Soil exploration logs contain material descriptions based on visual observation and field tests using a systemmodified from the Uniform Soil Classification System (USCS). Where necessary laboratory tests have beenconducted (as noted in the "Other Tests" column), unit descriptions may include a classification. Please refer to thediscussions in the report text for a more complete description of the subsurface conditions. 2. The graphic symbols given above are not inclusive of all symbols that may appear on the borehole logs.Other symbols may be used where field observations indicated mixed soil constituents or dual constituent materials. COMPONENT SIZE / SIEVE RANGE TEST SYMBOLS 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Test Pit TP-1 Approximate ground surface elevation: 437 feet Ground Surface Conditions: Tall grass Depth (ft) Material Description 0 – 4 Loose to medium dense, dry to moist, rusty-brown, silty SAND with gravel, iron oxide staining (Weathered Glacial Till). 4 – 10 Dense, moist, gray, silty SAND with gravel and trace cobbles (Glacial Till). -occasional sandy lenses Test Pit terminated approximately 10 feet below ground surface. No groundwater/seepage observed in the test pit. Notes: Test pits excavated using a Cat 330 tracked excavator owned and operated by Northwest Excavating. Test pit elevations based on topographic information provided on a preliminary site plan. 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Test Pit TP-2 Approximate ground surface elevation: 437 feet Ground Surface Conditions: Tall grass Depth (ft) Material Description 0 – 5 Loose to medium dense, moist to wet, brown, silty SAND with some gravel (Weathered Glacial Till). 5 – 10 Dense, moist, gray, silty SAND with gravel, trace cobbles (Glacial Till). Test Pit terminated approximately 10 feet below ground surface. No groundwater/seepage observed in the test pit. Notes: Test pits excavated using a Cat 330 tracked excavator owned and operated by Northwest Excavating. Test pit elevations based on topographic information provided on a preliminary site plan. 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Test Pit TP-3 Approximate ground surface elevation: 438 feet Ground Surface Conditions: Blackberry brambles Depth (ft) Material Description 0 – 2½ Loose to medium dense, moist, rusty-brown, silty SAND with gravel (Weathered Glacial Till). -Iron oxide staining near contact. 2½ – 8 Dense, moist, gray, silty SAND with gravel, trace cobbles (Glacial Till). -Becomes very dense around 6 feet Test Pit terminated approximately 8 feet below ground surface. No groundwater/seepage observed in the test pit. Notes: Test pits excavated using a Cat 330 tracked excavator owned and operated by Northwest Excavating. Test pit elevations based on topographic information provided on a preliminary site plan. 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Test Pit TP-4 Approximate ground surface elevation: 438 feet Ground Surface Conditions: Tall grass Depth (ft) Material Description 0 – 4 Loose to medium dense, dry, light brown, silty SAND with gravel (Weathered Glacial Till). -Localized pockets of clean sand 4 – 10 Dense, moist, gray, silty SAND with gravel, contains cobbles (Glacial Till). -Increase in sand content and moisture content around 8 feet. Test Pit terminated approximately 10 feet below ground surface. No groundwater/seepage observed in the test pit. Notes: Test pits excavated using a Cat 330 tracked excavator owned and operated by Northwest Excavating. Test pit elevations based on topographic information provided on a preliminary site plan. 07-107.200 Chelan Ave. Short Plat, Renton PanGEO, Inc. Date Test Pits Excavated: July 23, 2007 Test Pits Logged by: STS Test Pit TP-5 Approximate ground surface elevation: 433 feet Ground Surface Conditions: Blackberry brambles Depth (ft) Material Description 0 – 1.5 Loose, moist, dark brown, silty SAND with abundant organics (Topsoil & Fill). 1.5 – 4 Medium dense, moist, relatively clean sand and gravel, iron oxide staining (Outwash). 4 - 12 Dense, moist, gray, silty SAND with gravel, trace cobbles (Glacial Till). -contains occasional silt and relatively clean sand lenses Test Pit terminated approximately 12 feet below ground surface. No groundwater/seepage observed in the test pit. Notes: Test pits excavated using a Cat 330 tracked excavator owned and operated by Northwest Excavating. Test pit elevations based on topographic information provided on a preliminary site plan. APPENDIX E – CSWPPP REPORT BOUN SHORT PLAT SITE ADDRESS: 1012 DUVALL AVE NE RENTON, WA 98059 SECTION 32, TOWNSHIP 24 N., RANGE 05 E., W.M. Construction Stormwater Pollution Prevention Plan Prepared for: Warring Properties Contact: Kent Khnor 845 106th Ave, Suite 200 Federal Way, WA 98003 Date Prepared: Date Revised: October 5, 2016 June 1, 2017 Prepared by: Drew Young, EIT Reviewed by: Landon Beyler, P.E. Beyler Consulting 7602 Bridgeport Way W #3D Lakewood, WA 98499 253.301.4157 Project Number: 16-206 Project Name: Boun Short Plat RPT-CSWPPP-Boun Short Plat 2016.10.05 Page 2 of 10 TABLE OF CONTENTS I. Construction Pollution Prevention Plan .................................... 3 Section 1 – Project Overview ........................................................ 3 Section 3 – Existing Site Conditions ............................................... 4 Section 4 – Adjacent Areas ........................................................... 4 Section 5 – Critical Areas ............................................................. 4 Section 6 – Soils ......................................................................... 4 Section 7 – Potential Erosion Problems ........................................... 4 Section 8 – Construction Stormwater Pollution Prevention Elements ... 5 Section 9 – Construction Phasing .................................................. 9 Section 10 – Construction Schedule ............................................... 9 Section 11 – Financial/Ownership Responsibilities .......................... 10 Section 12 – Engineering Calculations .......................................... 10 Section 13 – Conclusion ............................................................. 10 **EROSION CONTROL RESPONSIBILITY** The Construction Stormwater Polllution Prevention Plan should be kept onsite with a copy of the plans at all time. The objective is to control erosion and prevent sediment and other pollutants from leaving the site during the construction of the project. The owner or assigned contractor shall be responsible for maintaining erosion control Best Management Practices during construction. All BMPs shall be inspected, maintained, and repaired as needed to assure continued performance of their intended function. The owner or contractor shall identify a Certified Erosion and Sediment Control Lead. This person shall be on-site or on-call at all times. The Erosion Control Lead information shall be inserted into this report. The CSWPP shall be modified, if during inspection or investigations conducted by the owner/operator, or the applicable local or state regulatory authority, it is determined that the CSWPPP is ineffective in elimination or significantly minimizing pollutants in stormwater discharges from the site. The CSWPPP shall be modified as necessary to include additional or modified BMPs designed to correct problems identified. Revisions to the SWPPP shall be completed within seven (7) calendar days following the inspection. Construction site operators are required to be covered by a Construction Stormwater General Permit through the Department of Ecology if they are engaged in clearing, grading, and excavating activities that disturb one or more acres and discharge stormwater to surface waters of the state. Smaller sites may also require coverage if they are part of a larger common plan of development that will ultimately disturb one acre or more. Page 3 of 10 I. Construction Pollution Prevention Plan Section 1 – Project Overview The proponent of the Boun Short Plat proposes to subdivide an undeveloped parcel, with the exception of an abandoned shed building that is to be removed as part of this project, located in the City of Renton, King County Washington. The King County parcel number for the property is 102305-9139. The project parcel is approximately 57,677 sf, 1.32 acres in size. The parcel is zoned Residential 8 (R-8) according to the City of Renton Zoning Map effective as of July 1, 2015. The allowed density range in the R-8 zone is a minimum of 4.0 dwelling units per net acre (DUA) to a maximum of 8.0 DUA. The Boun Short Plat proposes to subdivide the current parcel into 7 single-family lots equating to a proposed density of 5.29 DUA. The proposed lots range in size from the smallest being 5,172 sf in size and the largest being 6,553 sf in size. A single tract will be created with this subdivision for the purpose of stormwater treatment and mitigation and open space area for the development. The remaining area will be dedicated to the City of Renton for public right-of-way use. The property is adjacent to Duvall Ave NE to the east, single family parcels to the south and north, and Chelan Ave NE to the west. The proposed project is keeping consistent with neighboring land use characteristics. The site will be accessed through two separate access points. The first access will be an extension of Chelan Place NE, an existing 20’ alleyway, from the south boundary to the north boundary of the project parcel. This access way will be developed into a 12’ paved alley within a 16’ wide right-of-way dedication which meets the current City of Renton street standards for alleys. An additional access point to Chelan Ave NE will be provided in the east to west direction through a 12’ paved alley within a 16’ public access and utilities easement. Half street frontage improvements will be included along the west boundary of the project site. Chelan Avenue NE will be improved to two separate variations of the current City of Renton Standards for Residential Access Streets. Starting from the south boundary of the project site, the east half of Chelan Avenue NE will be improved to provide a 15-foot travel lane, vertical curb and gutter, an 8-foot wide planter strip, and a 5-foot wide sidewalk for approximately 120 feet. At this point, the Residential Access Street will transition into a Limited Residential Access Street which consists of a 20-foot paved roadway, vertical curb and gutter, an 8-foot wide planter strip, and a 5-foot sidewalk. This road section will be constructed north until it reaches the north boundary line of the project. To incorporate these improvements, an 18’ right of way dedication will be necessary along a portion of the northwest boundary of the project parcel. An 18’ wide section of right-of-way north of the project site will not be improved as part of this project. As a condition of preliminary plat approval (LUA16-00124), a road standards modification will be submitted concurrently with the Utility Construction Permit to allow for the 18’ wide section of right-of-way to remain undeveloped. This project is subject to the 2009 King County Surface Water Design Manual (King Manual) and the City of Renton amendments to the Manual (Renton Manual). Per Figure 1.1.2.A of the Renton Manual, the Boun Short Plat project is subject to a full drainage review meeting core requirements #1 through #8 and special requirements #1 through #6. It has been determined that the site consists of two separate threshold discharges areas. Threshold Discharge Area #1 (West Basin) consists of a majority of the project site area that naturally discharges stormwater to the southwest corner of the parcel. Threshold Discharge Page 4 of 10 Area #2 (A-East Basin, B-North basin) consists of a small portion of land along the east boundary which naturally discharges stormwater east to an existing swale within Duvall Ave NE (TDA 2.A) and the 18’ wide panhandle section of land located north of the project site that naturally discharges stormwater to the northwest (TDA 2.B). A drainage adjustment, per Section 1.4 of the Renton Manual, is proposed to combine a portion of threshold discharge area #2.A with threshold discharge area #1. See section III and IV of this report for further details. Section 2 – Erosion Control Specialist It will be responsibility of the owner and/or the contractor to regularly inspect and maintain the proposed erosion control BMPs, and will take additional measures, as necessary, to respond to changing site conditions. Should it become necessary, the engineer will be made available in providing recommendations for additional erosion control measures to the site. Section 3 – Existing Site Conditions Currently, the parcel is undeveloped with the exception of an abandoned shed building that is to be removed as part of this project. The project is composed of two (2) threshold discharge areas. The site has a localized high point near the south central portion of the property. Water sheet flows southwest and northeast from this high point with an overall vertical relieve of 5 feet. Several existing utility service connections (sewer, storm, water, power, cable, etc.) are located within the existing right of way boundary of Chelan Ave NE and Duvall Ave NE. There are no known vegetative buffers, floodplains, wetlands, geologic hazard areas, streams, creeks, ponds, ravines, or well protection areas present within or near the project area. Section 4 – Adjacent Areas The property is adjacent to Duvall Ave NE to the east, single family parcels to the south and north, and Chelan Ave NE to the west. The proposed project is keeping consistent with neighboring land use characteristics. Section 5 – Critical Areas King County GIS mapping and City of Renton GIS mapping were utilized to determine critical areas that may be located on or near the project site. There are no known vegetative buffers, floodplains, wetlands, geologic hazard areas, streams, creeks, ponds, ravines, or well protection areas present within or near the project area. Section 6 – Soils The Soil Conservation Service Soil Survey shows that the project area soils are comprised of Alderwood Gravelly Sandy Loam (Map Unit Symbol: AgC). Alderwood Gravelly Sandy Loam soils are generally derived from glacial drift and/or glacial outwash over dense glaciomarine deposits and are moderately well drained that range in slope from 8 to 15 percent. Page 5 of 10 Section 7 – Potential Erosion Problems Due to the existing stabilized ground cover and the site consisting of slopes between 0 to 5 percent, it is anticipated the site will be adequately protected from potential erosion problems. Care shall be given to stockpiled materials during construction to minimize the potential for erosion. Catch basins shall be fitted with inlet silt protections, both on-site and off-site, to protect the existing stormwater management systems. The existing drainage swale along Duvall Ave NE shall be protected from erosion, at a minimum, with silt perimeter fencing along cleared/graded areas. To minimize any potential erosion problems, Grade roads/driveways and construct bases as soon as possible. Cover any unworked soil during extended times of no construction activity. Keep as much construction traffic as possible on the road base and off open soils to avoid compaction of the native soils. Silt fences or other BMPs that are capable of retaining water shall be utilized to retain silt laden runoff to the project area. Section 8 – Construction Stormwater Pollution Prevention Elements Element 1: Mark Clearing Limits Prior to beginning land disturbing activities, including clearing and grading, all clearing limits, sensitive areas and their buffers, and trees that are to be preserved within the construction area shall be clearly marked, both in the field and on the plans, to prevent damage and offsite impacts Plastic, metal, or stake wire fence may be used to mark the clearing limits. The duff layer, native top soil, and natural vegetation shall be retained in an undisturbed state to the maximum extent practicable. If it is not practicable to retain the duff layer in place, it should be stockpiled on-site, covered to prevent erosion, and replaced immediately upon completion of the ground disturbing activities Suggested BMPs: BMP: Preserving Natural Vegetation BMP D.3.1.1: High Visibility Plastic or Metal Fence BMP D.3.3.1: Silt Fence Element 2: Establish Construction Access Construction vehicle access should utilitize the proposed stabilized construction entrance within the project clearing limits. Contractor shall restrict movement in and out of the site to one entrance and one exit. When a construction entrance is not preventing sediment from being tracked onto pavement, a wheel wash should be considered. If sediment is tracked off site, the public roads shall be cleaned thoroughly at the end of each day. During wet weather, public roads may need to be cleaned more frequently to prevent sediment from entering water of the state. Suggested BMPs: BMP D.3.4.1: Stabilized Construction Entrance/Exit BMP D.3.4.2: Construction Road/Parking Area Stabilization Page 6 of 10 Element 3: Control Flow Rates Properties and waterways downstream from development sites shall be protected from erosion due to increases in the volume, velocity, and peak flow rate of stormwater runoff from the project site. Temporary interceptor swales will be installed, as necessary, to direct runoff during construction to the temporary sediment trap located along the west boundary of the project site. Depending on the longitudinal slope of the swale, rock check dams will be placed to control flow rates of runoff. Suggested BMPs: BMP D.3.6.1: Interceptor Dike and Swale BMP D.3.6.4: Check Dams BMP D.3.5.1: Sediment Trap BMP D.3.6.5: Outlet Protection Element 4: Install Sediment Controls Prior to leaving a construction site, stormwater runoff from disturbed areas shall pass through a sediment removal BMP. Runoff from fully stabilized areas may be discharged without a sediment removal BMP. Full stabilization means the use of erosion products or vegetative cover that will fully prevent soil erosion. Suggested BMPs: BMP D.3.5.1: Sediment Trap BMP D.3.3.1: Silt Fence Element 5: Stabilize Soils The following constraints will apply. From October 1 through April 30, no soils shall remain exposed and unworked for more than 2 days. From May 1 to September 30, no soils will remain exposed and unworked for more than 7 days. This condition will apply to all soils on site, whether at final grade or not. The areas outside of the roadway will be stabilized with mulch, grass planting or other approved erosion control treatment during the construction phase. Suggested BMPs BMP D.3.2.1: Surface Roughening BMP D.3.2.6: Temporary and Permanent Seeding BMP D.3.2.2: Mulching BMP D.3.2.3: Nets and Blankets BMP D.3.2.4: Plastic Covering BMP D.3.2.7: Sodding BMP D.3.2.9: Compost Blankets BMP D.3.8: Dust Control Page 7 of 10 Element 6: Protect Slopes Design and construct cut and fill slopes in a manner that will minimize erosion. If found necessary to aid in surface water routing during construction, temporary interceptor swales shall be excavated to slope any developed runoff to a sediment trap or pond. Rock check dams shall be placed at regular intervals to reduce slope runoff velocities within the temporary inceptor swales. Exposed soils on slopes shall be stabilized as specified in Element 5. Suggested BMPs: BMP D.3.2.6: Temporary and Permanent Seeding BMP D.3.2.2: Mulching BMP D.3.2.3: Nets and Blankets BMP D.3.6.4: Check Dams Element 7: Protect Drain Inlets All storm drain inlets made operable during construction shall be protected so that stormwater runoff shall not enter the conveyance system without first being filtered or treated to remove sediment. Existing downstream catch basins located within the vicinity of the project site shall be protected using storm drain inlet protection. After installation of grated inlets on the property, these structures shall be provided a form of inlet protection. Suggested BMPs BMP D.3.5.3: Storm Drain Inlet Protection Element 8: Stabilize Channels and Outlets All temporary stormwater channels shall be stabilized to limit the erosion potential during construction. Temporary on-site conveyance channels shall be designed, construction and stabilized to prevent erosion. When the permanent outlets are installed, they shall be protected with washed rock/rip rap for erosion protection. Suggested BMPs BMP D.3.6.4: Check Dams BMP D.3.6.5: Outlet Protection Element 9: Control Pollutants Control of pollutants are the responsibility of the construction superintendent. Maintenance and repair of heavy equipment and vehicles involving oil changes, hydraulic system drain down, solvent and de-greasing cleaning operations, fuel tank drain down and removal, and other activities that may result in discharge or spillage of pollutants to the ground or into stormwater runoff must be conducted using spill prevention measures, such as drip pans. Contaminated surfaces will be cleaned immediately following any discharge or spill incident. The superintendent will be expected to use his best judgment in addressing any and all Page 8 of 10 conditions that are potentially damaging to the environment. Emergency repairs may be performed on-site using temporary plastic placed beneath and, if raining, over the vehicle. All pollutants, including waste materials and demolition debris that occur on-site during construction will be handled and disposed of in a manner that does not cause contamination of stormwater. Cover, containment, and protection from vandalism will be provided for all chemicals, liquid products, petroleum products, and non-inert wastes present on the site. Suggested BMPs BMP C151: Concrete Handling (2015 Washington State DOE Manual) BMP C152: Sawcutting and Surfacing Pollution Prevention (2015 DOE Manual) BMP C153: Material Delivery, Storage and Containment (2015 DOE Manual) Element 10: Control De-Watering De-watering is not anticipated. However, if encountered, de-watering shall be discharged into a closed conveyance system for discharge from the site. The water resulting from construction site de-watering activities must be treated prior to discharge or disposed in a manner that is consistent with the City of Renton Manual. Highly turbid or otherwise contaminated dewatering water, such as from construction equipment operation will be handled separately from stormwater. Element 11: Maintain BMPs All temporary and permanent erosion and sediment control BMPs shall be maintained and repaired as needed to assure continued performance of their intended function. All maintenance and repair will be conducted in accordance with standard procedures for the BMPs. Sediment control BMPs will be inspected weekly or after a runoff-producing storm event during the dry season and daily during the wet season. All temporary erosion and sediment control BMPs will be removed within 30 days after final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be removed or stabilized on site. Disturbed soil areas resulting from removal of BMPs or vegetation will be permanently stabilized with mulch, grass planting or other approved erosion control treatment. Suggested BMPs BMP C150: Materials On Hand (2015 DOE Manual) BMP C160: Certified Erosion and Sediment Control Lead (2015 DOE Manual) Element 12: Manage the Project Site construction will be performed after the erosion and sediment control measures have been constructed. Preparation for site grading and earthwork should include procedures intended to drain ponded water and control surface water runoff. Grading the site without adequate drainage control measures may negatively impact site soil. From October 1 through April 30, clearing, grading, and other soil disturbing activities shall only be permitted if the transport of sediment from the construction site to receiving waters will be prevented through a combination of favorable site and weather conditions, Page 9 of 10 limitations on extent of activity, and proposed erosion and sediment control measures. The Contractor and/or owner should stop the permitted activity if sediment leaves the construction site causing a violation of the surface water quality standard or if erosion and sediment control measures are not adequately maintained. Trenches should be opened only immediately prior to construction and the trenches will be backfilled immediately after any required testing or inspections of the installed improvements. Trenching spoils will be treated as other disturbed earthwork and measures will be taken to cover or otherwise stabilize the material, as required. All BMPs shall be inspected, maintained, and repaired as needed to assure continued performance of their intended function. Section 9 – Construction Phasing The recommended construction sequence will include these steps in this order, but some portions of the steps may be performed out of sequence as conditions require. The Construction Sequence is as follows: 1. The contractor shall become familiar with the property, construction drawings and geotechnical conditions on site. The contractor shall meet with the developer, civil engineer, and any other design professional to review the physical constraints affecting the proposed construction. 2. The contractor shall schedule and attend a pre-construction meeting with the City of Renton prior to preforming any site work. 3. For each phase of work, the project surveyor shall flag the limits of clearing and grading, and the contractor shall install all temporary erosions control measures. 4. When TESC measures are approved by the City inspector, install site improvements. 5. Proceed with site improvements making adjustments to the Erosion Control measures as needed. 6. Install final soil stabilization/amendments in areas where final grades have been achieved and future disturbance can be avoided. 7. Hydroseed or place straw mulch on any other disturbed areas. 8. Once the threat of erosion has passed, and all construction is complete, the remaining erosion control measure may be removed with approval from the City inspector. 9. All permanent drainage facilities shall be cleaned of any sediment and construction debris. Sediment laden water shall not be flushed downstream. All storm drainage facilities shall be protected in place from construction activity via brightly flagged stakes or, if necessary, temporary construction fencing. Section 10 – Construction Schedule The project is intended to begin construction in the Spring of 2017. Special consideration is required for source control during the wet season period, which may include phased construction, materials available for immediate stabilization of denuded areas and diligent review of site for noted erosion concerns. Page 10 of 10 Section 11 – Financial/Ownership Responsibilities The property owner will be responsible for bonds and other required securities for this project. Section 12 – Engineering Calculations Sediment Trap Calculations 15-Minute Peak Flow Calculations using KCRTS Flow Frequency Analysis Time Series File:dev-15min.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.304 6 8/27/01 18:00 1.02 1 100.00 0.990 0.224 8 1/05/02 15:00 0.690 2 25.00 0.960 0.690 2 12/08/02 17:15 0.429 3 10.00 0.900 0.244 7 8/23/04 14:30 0.425 4 5.00 0.800 0.425 4 11/17/04 5:00 0.374 5 3.00 0.667 0.374 5 10/27/05 10:45 0.304 6 2.00 0.500 0.429 3 10/25/06 22:45 0.244 7 1.30 0.231 1.02 1 1/09/08 6:30 0.224 8 1.10 0.091 Computed Peaks 0.909 50.00 0.980 SA = FS (Q2-year/Vs) = 2 * (0.304/.00096) = 633.3 sf = 634 sf See sheet C2 of the plan set for sediment trap location and details. Section 13 – Conclusion Erosion control procedures as described in this report and illustrated on the design plans, if properly implemented, should mitigate anticipated erosion effects from the development of this project. The success of erosion control measures is usually related to the Contractor’s attention to maintenance of such measures. However, in some instances, even with proper attention being paid to erosion control, measures such as those shown on the plans are unable to prevent the discharge of turbid water. In this event, secondary measures may be required. These additional BMPs are provided in Appendix D of the 2009 King County Surface Water Design Manual and Volume 2 of the 2012 edition of the Washington State Department of Ecology Stormwater Management Manual for Western Washington. APPENDIX F – OPERATION AND MAINTENANCE WORKSHEETS APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-5 NO. 3 – DETENTION TANKS AND VAULTS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Site Grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non-floatables). No trash or debris in vault. Tank or Vault Storage Area Sediment accumulation Accumulated sediment depth exceeds 10% of the diameter of the storage area for ½ length of storage vault or any point depth exceeds 15% of diameter. Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than ½ length of tank. All sediment removed from storage area. Plugged air vent Any blockage of the vent. Tank or vault freely vents. Tank bent out of shape Any part of tank/pipe is bent out of shape more than 10% of its design shape. Tank repaired or replaced to design. Tank Structure Gaps between sections, damaged joints or cracks or tears in wall A gap wider than ½-inch at the joint of any tank sections or any evidence of soil particles entering the tank at a joint or through a wall. No water or soil entering tank through joints or walls. Vault Structure Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Inlet/Outlet Pipes Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 1/9/2009 2009 Surface Water Design Manual – Appendix A A-6 NO. 3 – DETENTION TANKS AND VAULTS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance. Manhole access covered. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person. Access Manhole Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can opened as designed. Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat and covers access opening completely. Large access doors/plate Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-7 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Trash or debris of more than ½ cubic foot which is located immediately in front of the structure opening or is blocking capacity of the structure by more than 10%. No Trash or debris blocking or potentially blocking entrance to structure. Trash or debris in the structure that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the structure. Trash and debris Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Sediment Sediment exceeds 60% of the depth from the bottom of the structure to the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section or is within 6 inches of the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section. Sump of structure contains no sediment. Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Damage to frame and/or top slab Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering structure through cracks, or maintenance person judges that structure is unsound. Structure is sealed and structurally sound. Cracks in walls or bottom Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering structure through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Structure has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Structure Ladder rungs missing or unsafe Ladder is unsafe due to missing rungs, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows maintenance person safe access. T section is not securely attached to structure wall and outlet pipe structure should support at least 1,000 lbs of up or down pressure. T section securely attached to wall and outlet pipe. Structure is not in upright position (allow up to 10% from plumb). Structure in correct position. Connections to outlet pipe are not watertight or show signs of deteriorated grout. Connections to outlet pipe are water tight; structure repaired or replaced and works as designed. FROP-T Section Damage Any holes—other than designed holes—in the structure. Structure has no holes other than designed holes. Cleanout Gate Damaged or missing Cleanout gate is missing. Replace cleanout gate. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 1/9/2009 2009 Surface Water Design Manual – Appendix A A-8 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Cleanout gate is not watertight. Gate is watertight and works as designed. Gate cannot be moved up and down by one maintenance person. Gate moves up and down easily and is watertight. Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed. Damaged or missing Control device is not working properly due to missing, out of place, or bent orifice plate. Plate is in place and works as designed. Orifice Plate Obstructions Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Obstructions Any trash or debris blocking (or having the potential of blocking) the overflow pipe. Pipe is free of all obstructions and works as designed. Overflow Pipe Deformed or damaged lip Lip of overflow pipe is bent or deformed. Overflow pipe does not allow overflow at an elevation lower than design Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Inlet/Outlet Pipe Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal Metal Grates (If Applicable) Damaged or missing Grate missing or broken member(s) of the grate. Grate is in place and meets design standards. Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Manhole Cover/Lid Cover/lid difficult to Remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-9 NO. 5 – CATCH BASINS AND MANHOLES Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Sediment Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert of the lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin. Sump of catch basin contains no sediment. Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin by more than 10%. No Trash or debris blocking or potentially blocking entrance to catch basin. Trash or debris in the catch basin that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the catch basin. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane). No dead animals or vegetation present within catch basin. Trash and debris Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Damage to frame and/or top slab Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering catch basin through cracks, or maintenance person judges that catch basin is unsound. Catch basin is sealed and structurally sound. Cracks in walls or bottom Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Structure Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Inlet/Outlet Pipe Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 1/9/2009 2009 Surface Water Design Manual – Appendix A A-10 NO. 5 – CATCH BASINS AND MANHOLES Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal Metal Grates (Catch Basins) Damaged or missing Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance. Grate is in place and meets design standards. Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Manhole Cover/Lid Cover/lid difficult to Remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-11 NO. 6 – CONVEYANCE PIPES AND DITCHES Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes. Vegetation/roots Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Damage to protective coating or corrosion Protective coating is damaged; rust or corrosion is weakening the structural integrity of any part of pipe. Pipe repaired or replaced. Pipes Damaged Any dent that decreases the cross section area of pipe by more than 20% or is determined to have weakened structural integrity of the pipe. Pipe repaired or replaced. Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Trash and debris cleared from ditches. Sediment accumulation Accumulated sediment that exceeds 20% of the design depth. Ditch cleaned/flushed of all sediment and debris so that it matches design. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Vegetation Vegetation that reduces free movement of water through ditches. Water flows freely through ditches. Erosion damage to slopes Any erosion observed on a ditch slope. Slopes are not eroding. Ditches Rock lining out of place or missing (If Applicable) One layer or less of rock exists above native soil area 5 square feet or more, any exposed native soil. Replace rocks to design standards. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-17 NO. 12 – ACCESS ROADS Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Trash and debris exceeds 1 cubic foot per 1,000 square feet (i.e., trash and debris would fill up one standards size garbage can). Roadway drivable by maintenance vehicles. Trash and debris Debris which could damage vehicle tires or prohibit use of road. Roadway drivable by maintenance vehicles. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Any obstruction which reduces clearance above road surface to less than 14 feet. Roadway overhead clear to 14 feet high. Site Blocked roadway Any obstruction restricting the access to a 10- to 12 foot width for a distance of more than 12 feet or any point restricting access to less than a 10 foot width. At least 12-foot of width on access road. Erosion, settlement, potholes, soft spots, ruts Any surface defect which hinders or prevents maintenance access. Road drivable by maintenance vehicles. Road Surface Vegetation on road surface Trees or other vegetation prevent access to facility by maintenance vehicles. Maintenance vehicles can access facility. Erosion Erosion within 1 foot of the roadway more than 8 inches wide and 6 inches deep. Shoulder free of erosion and matching the surrounding road. Shoulders and Ditches Weeds and brush Weeds and brush exceed 18 inches in height or hinder maintenance access. Weeds and brush cut to 2 inches in height or cleared in such a way as to allow maintenance access. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Modular Grid Pavement Damaged or missing Access surface compacted because of broken on missing modular block. Access road surface restored so road infiltrates. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-23 NO. 17 – WETVAULT Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Site Trash and debris Trash and debris accumulated on facility site. Trash and debris removed from facility site. Trash and debris Any trash and debris accumulated in vault (includes floatables and non-floatables). No trash or debris in vault. Sediment accumulation Sediment accumulation in vault bottom exceeds the depth of the sediment zone plus 6 inches. No sediment in vault. Treatment Area Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch, any evidence of soil entering the structure through cracks, vault does not retain water or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. Baffles damaged Baffles corroding, cracking, warping and/or showing signs of failure or baffle cannot be removed. Repair or replace baffles or walls to specifications. Vault Structure Ventilation Ventilation area blocked or plugged. No reduction of ventilation area exists. Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Inlet/Outlet Pipe Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Inoperable valve Valve will not open and close. Valve opens and closes normally. Gravity Drain Valve won’t seal Valve does not seal completely. Valve completely seals closed. Access cover/lid damaged or difficult to open Access cover/lid cannot be easily opened by one person. Corrosion/deformation of cover/lid. Access cover/lid can be opened by one person. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person. Access doors/plate has gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat and covers access opening completely. Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate. Access Manhole Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access.