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RS_Drainage_Technical_Information_Report_200526_APPROVED
coterra 321 3rd Avenue South, Suite 406 Seattle, Washington 98104 206.596.7115 TECHNICAL INFORMATION REPORT Project: Renton Housing Authority Sunset Oaks Apartments Renton, WA 98056 Prepared For: Renton Housing Authority 2900 NE 10th St Renton, WA 98056 Prepared By: Max Berde, PE Reviewed By: Peter Apostol, PE Date: May 26, 2020 ENGINEERING PLLC APPROVED 06/16/2020 msippo DEVELOPMENT ENGINEERING DIVISION SURFACE WATER UTILITY jfarah 06/17/2020 TABLE OF CONTENTS Section No. Subject Page No. SECTION I PROJECT OVERVIEW .....................................................................1 SECTION II CONDITIONS AND REQUIREMENTS SUMMARY ...................15 SECTION III OFFSITE ANALYSIS ......................................................................18 SECTION IV FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ..........................................21 SECTION V CONVEYANCE SYSTEM ANALYSIS AND DESIGN ................24 SECTION VI SPECIAL REPORTS AND STUDIES .............................................24 SECTION VII OTHER PERMITS ...........................................................................24 SECTION VIII EROSION AND SEDIMENT CONTROL ......................................24 SECTION IX BOND QUANTITIES AND DECLARATION OF COVENANTS ...............................................26 SECTION X OPERATIONS AND MAINTENANCE MANUAL .......................28 LIST OF FIGURES FIGURE 1 VICINITY MAP .................................................................................4 FIGURE 2 TIR WORKSHEET ............................................................................5 FIGURE 3 EXISTING SITE SOILS...................................................................12 FIGURE 4 EXISTING LAND COVER .............................................................13 FIGURE 5 DEVELOPED LAND COVER ........................................................14 FIGURE 6 OFF-SITE DRAINAGE SYSTEM ...................................................19 FIGURE 7 ROW UPSTREAM DRAINAGE AREAS .......................................25 FIGURE 8 BACKWATER ANALYSIS AREAS .......................... APPENDIX D LIST OF APPENDICIES APPENDIX A CIVIL PLANS APPENDIX B FLOW CONTROL/DETENTION CALCULATIONS APPENDIX C WATER QUALITY CALCULATIONS APPENDIX D CONVEYANCE/BACKWATER CALCULATIONS APPENDIX E DRAINAGE REVIEW FLOWCHART APPENDIX F BOND QUANTITIES WORKSHEET APPENDIX G DECLARATION OF COVENANTS APPENDIX H OPERATIONS AND MAINTENANCE MANUAL APPENDIX I SPECIAL REPORTS AND STUDIES Sunset Oaks Apartments Page 1 Project No. 19003 Renton, WA Coterra Engineering PLLC SECTION I – PROJECT OVERVIEW General Description: The proposed Sunset Oaks Apartment project includes the construction of three multi- story apartment buildings on a proposed 1.053 acre lot currently consisting of five currently-undeveloped parcels. The existing five parcels were previously developed as single-family homes and previously demolished. Proposed project includes on-site parking, landscaping, frontage improvements on Glennwood Ave NE and Harrington Ave NE, and associated utility and storm drainage improvements. The project proposes to construct a public alley between Glennwood Ave NE and Harrington Ave NE on the northern margin of the site. The alley will be dedicated to the City of Renton. The project site, located in the City of Renton, is bounded by Glennwood Ave NE to the west, Harrington Ave NE to the east, Sunset Lane NE (NE 10th Street) to the south, and residential parcels to the north (see Figure 1 for vicinity map). The proposed project has been designed to meet the requirements of the 2017 City of Renton Surface Water Design Manual (SWDM). A summary of the project data is provided in the TIR worksheet (see Figure 2). Site Soils: The NRCS map (see Figure 3) of the site shows a majority of the site consisting of “Arents, Alderwood material” with a small portion of the west side of the site consisting of “Ragnar-Indianola” soils. Additional information on the site’s soils is provided in a geotechnical report prepared by Zipper Geo Associates, LLC, and dated November 5, 2019. The findings of the report are based on soil samples taken from five borings that were excavated on-site. In general, the results of the borings uncovered 3’-12’ of medium dense to dense sand with variable silt and gravel contents. Below that layer the borings encountered very dense sand with variable silt and gravel contents that the geotechnical engineer interprets to be glacial till. For more information, see the geotechnical report included in Appendix I. Predeveloped Conditions: The existing site is currently undeveloped with areas of impervious remaining from demolition and clearing of the former single-family residences on the 3 project parcels. The remainder of the site is considering to be pervious, former landscaping, consisting of till grass for stormwater modeling purposes. There are several significant trees spread throughout the site. The project site consists of one Threshold Discharge Area which is defined by the City of Renton Surface Water Design Manual as: “an onsite area draining to a single natural discharge location, or multiple natural discharge locations that combine within one-quarter –mile downstream.” The site is generally flat with stormwater runoff draining overland generally north to south towards Sunset Lane NE. Sunset Oaks Apartments Page 2 Project No. 19003 Renton, WA Coterra Engineering PLLC The existing land coverage of the project site is presented in the table below. The existing site is presented graphically in Figure 4 which follows this section. The downstream path of stormwater runoff is described in the offsite analysis in Section III. Table 1 – Existing Site Land Coverage (Acres) Developed Conditions: The proposed developed condition includes three apartment buildings with at-grade parking stalls adjacent to and within the buildings; a public alley at the northern margin of the site; pedestrian walkways; and associated storm drainage, utility, and landscape improvements. The following table quantifies the areas of the proposed land coverage. The proposed site is presented graphically in Figure 5 which follows this section. Table 2 – Developed Site Land Coverage (Acres) The existing site topography will not be dramatically altered in the proposed condition. In general, the site will continue to drain from north to south towards Sunset Lane NE as it currently does in the existing condition. The proposed improvements within the project site described above and delineated in Table 2 trigger both flow control and water quality mitigation per the City of Renton Surface Water Design Manual. Sunset Oaks Apartments Page 3 Project No. 19003 Renton, WA Coterra Engineering PLLC Stormwater runoff will be collected by roof drains, catch basins, and area drains. Per Core Requirement #4 of the 2017 City of Renton Surface Water Design Manual, the proposed conveyance system will be designed to convey runoff resulting from the peak rates resulting from the 25-year storm event. The proposed flow control facility is a detention tank located under the northwest parking lot and which will discharge to the proposed 18” storm drainage main in Glennwood Ave NE to the west. Permeable pavements throughout the project site, including pervious asphalt and pervious concrete sidewalks, will provide water quality treatment. See Section IV for a detailed description of the design of the flow control and water quality facilities. Sunset Oaks Apartments Page 4 Project No. 19003 Renton, WA Coterra Engineering PLLC FIGURE 1 – VICINITY MAP Sunset Oaks Apartments Page 5 Project No. 19003 Renton, WA Coterra Engineering PLLC FIGURE 2 CITY OF RENTON TECHNICAL INFORMATION REPORT (TIR) WORKSHEET CITY OF RENTON SURFACE WATER DESIGN MANUAL 2017 City of Renton Surface Water Design Manual 12/12/2016 8-A-1 REFERENCE 8-A TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner _____________________________ Phone ___________________________________ Address __________________________________ _________________________________________ Project Engineer ___________________________ Company _________________________________ Phone ___________________________________ Project Name __________________________ CED Permit # ________________________ Location Township ________________ Range __________________ Section _________________ Site Address __________________________ _____________________________________ Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Land Use (e.g., Subdivision / Short Subd.) Building (e.g., M/F / Commercial / SFR) 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 (check one): Date (include revision dates): Date of Final: Full Targeted Simplified Large Project Directed ____________________________________ __________________ Plan Type (check one): Date (include revision dates): Date of Final: Full Modified Simplified ____________________________________ __________________ RENTON HOUSING AUTHORITY (425)226-1850 2900 NE 10TH STREET RENTON,WA 98056 PETER APOSTOL,PE COTERRA ENGINEERING,PLLC (206)596-7115 SUNSET OAKS APARTMENTS 23N 5E 9 1062 GLENNWOOD AVE NE RENTON,WA 98056 X X NPDES CONSTRUCTION STORMWATER X X X X X 12/10/2019 CIVIL CONSTRUCTION PERMITX REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-2 Part 6 SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Blanket Description: (include conditions in TIR Section 2) ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Approved Adjustment No. ______________________ Date of Approval: _______________________ Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: _______________________ Completion Date: _______________________ Describe: _________________________________ _________________________________________ _________________________________________ Re: SWDM Adjustment No. ________________ 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 ______________________ _____________________________________ EAST LAKE WASINGTON -RENTON SUB BASIN:JOHNS CREEK MIN REQUIREMENTS #1 -#9;SPECIAL REQUIREMENTS #1 -#5 RENTON REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2017 City of Renton Surface Water Design Manual 12/12/2016 Ref 8-A-3 Part 10 SOILS Soil Type ______________________ ______________________ ______________________ ______________________ Slopes ________________________ ________________________ ________________________ ________________________ Erosion Potential _________________________ _________________________ _________________________ _________________________ High Groundwater Table (within 5 feet) Other ________________________________ Sole Source Aquifer Seeps/Springs Additional Sheets Attached Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE Core 2 – Offsite Analysis_________________ Sensitive/Critical Areas__________________ SEPA________________________________ LID Infeasibility________________________ 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 (include facility summary sheet) Standard: _______________________________ or Exemption Number: ____________ On-site BMPs: _______________________________ Conveyance System Spill containment located at: _____________________________ Erosion and Sediment Control / Construction Stormwater Pollution Prevention CSWPP/CESCL/ESC Site Supervisor: _____________________ Contact Phone: _________________________ After Hours Phone: _________________________ AmC -ARDENTS,ALDERWOOD MATERIALS 0 -5%LOW GLENNWOOD AVE NE MIN REQUIREMENTS #1 -#9;SPECIAL REQUIREMENTS #1 -#5 1 PEAK RATE FLOW CONTROL STANDARD REQUIRED MEF PER CORE REQUIREMENT #9 TBD RdC -RAGNAR-INDIANOLA 0 -5%LOW 1062 GLENNWOOD AVE NE RENTON,WA 98056 REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-4 Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No Water Quality (include facility summary sheet) Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog or Exemption No. _______________________ Special Requirements (as applicable): Area Specific Drainage Requirements Type: SDO / MDP / BP / Shared Fac. / None Name: ________________________ Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): _______________ Datum: Flood Protection Facilities Describe: Source Control (commercial / industrial land use) Describe land use: Describe any structural controls: Oil Control High-Use Site: Yes / No Treatment BMP: _________________________________ Maintenance Agreement: Yes / No with whom? _____________________________________ Other Drainage Structures Describe: MULTI-FAMILY DETENTION FACILITY -DETENTION TANK REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2017 City of Renton Surface Water Design Manual 12/12/2016 Ref 8-A-5 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 Control Pollutants Protect Existing and Proposed BMPs/Facilities Maintain Protective BMPs / Manage Project 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 BMPs/Facilities, restore operation of BMPs/Facilities as necessary Flag limits of sensitive areas 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 On-site BMPs Other ________________ ________________ ________________ ________________ ________________ ________________ Vegetated Flowpath Wetpool Filtration Oil Control Spill Control On-site BMPs Other ________________ ________________ ________________ ________________ ________________ ________________ ________________ 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 _______________________________ X X X X XX X X X X X X X DETENTION TANK X X BIOPOD FILTRATION VAULT X X X X PERMEABLE PAVEMENT REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 12/12/2016 2017 City of Renton Surface Water Design Manual 8-A-6 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 5/26/2020 Sunset Oaks Apartments Page 12 Project No. 19003 Renton, WA Coterra Engineering PLLC FIGURE 3 – EXISTING SITE SOIL CONDITIONS Arents, Alderwood material Ragnar-Indianola association coterra 321 3rd Avenue South, Suite 406Seattle, Washington 98104206.596.7115 coterraengineering.com ENGINEERING PLLC coterra 321 3rd Avenue South, Suite 406Seattle, Washington 98104206.596.7115 coterraengineering.com ENGINEERING PLLC Sunset Oaks Apartments Page 15 Project No. 19003 Renton, WA Coterra Engineering PLLC SECTION II – CONDITIONS AND REQUIREMENTS SUMMARY The proposed project is subject to a Full Drainage Review per the 2017 City of Renton Surface Water Design Manual and is therefore subject to all nine core requirements and all six special requirements. These requirements are listed below along with a discussion of their applicability to this project. See Appendix E for drainage review type flowchart. Core Requirements: Req. #1 Discharge at Natural Location: Existing discharge locations will be maintained. Req. #2 Offsite Analysis: See Section III below. Req. #3 Flow Control: The project is required to meet the Peak Rate Flow Control Standard. The proposed improvements exceed the threshold of 5,000 sf of new and replaced impervious surface, therefore triggering the requirement of a flow control facility and on-site flow control BMPs. A detention tank is proposed to meet the Peak Rate Flow Control Standard requirement. Onsite BMPs are also required as part of the project and are discussed below in Core Requirement #9. For further details see Section IV. Req. #4 Conveyance System: The new conveyance system has been designed to convey the 25-year peak flow from the developed site conditions as well as has been check with a 100-year peak flow backwater calculation. Req. #5 Erosion and Sediment Control: Construction erosion and sediment control systems will be designed and provided for review at civil construction permit submittal. Sunset Oaks Apartments Page 16 Project No. 19003 Renton, WA Coterra Engineering PLLC Req. #6 Maintenance and Operations: A Declaration of Covenant is required for this project and will be submitted for review by City of Renton staff before recording. The proposed facilities will be owned and maintained by Renton Housing Authority. Req. #7 Financial Guarantees: A financial guarantee will be necessary for this project. Bonding will be required for the construction of improvements and will be obtained prior to construction. Req. #8 Water Quality: The proposed improvements located on the project site exceed 5,000 sf of new and replaced Pollution-Generating Impervious Surface (PGIS), therefore triggering the requirement of a water quality facility. Based on the proposed site usage, multi-family housing, Enhanced Basic Water Quality treatment is required per Core Requirement #8 of the 2017 City of Renton Surface Water Design Manual for targeted PGIS. Although permeable pavement is proposed to be installed throughout the site, it will not provide Enhanced Basic Water Quality Treatment per the City of Renton SWDM requirements. Enhanced Basic Water Quality treatment per Core Requirement #8 of the 2017 City of Renton Surface Water Design Manual for targeted PGIS is required. An Oldcastle BioPod media filtration vault is proposed to meet the requirements of the Enhanced Basic Water Quality requirement within the SWDM. For further details see Section IV. Req. #9 On-Site BMPs: The proposed improvements exceed the threshold of 5,000 sf of new and replaced impervious surface, therefore triggering the requirements of Core Requirement #9 to implement on-site flow control facilities to the maximum extent feasible. Following the City of Renton SWDM required list method for Individual Large Lots implementing on-site BMPs to comply with Core Requirement #9, permeable pavement was determined to be the first feasible BMP for the proposed project site. Sunset Oaks Apartments Page 17 Project No. 19003 Renton, WA Coterra Engineering PLLC Permeable pavement will be installed throughout the project site and for concrete sidewalks in any frontage improvements on Glennwood Ave NE and Harrington Ave NE. Porous asphalt, porous concrete sidewalks, and permeable parking lot pavers are proposed for the project site. For further details see Section IV. Special Requirements: Req. #1 Area Specific Requirements: Proposed project site is part of the Sunset Terrace Redevelopment Project within the City of Renton. Master Site Plan was reviewed and approved by City of Renton. Additionally, Sunset Terrace Redevelopment Project was reviewed by NOAA for compliance with requirements of Section 7 of the Endangered Species Act (ESA) with respect to its potential effects on species listed or proposed for listing under the ESA. Project must maintain specific impervious coverage limits for overall Sunset Terrace Redevelopment Project which were approved as part of previous reviews and agreements. To meet these approved impervious coverage thresholds, proposed Sunset Oaks Apartments project must implement permeable pavement throughout project site and for sidewalks on any frontage improvements. Req. #2: Floodplain/Floodway Delineation This project is not adjacent to any floodplains or floodways. Therefore no delineation is necessary. Req. #3 Flood Protection Facilities: This project is not adjacent to any applicable areas and will not affect any applicable facility. Req. #4 Source Controls: This project is a multi-family project and will provide appropriate source controls. Req. #5 Oil Control: Sunset Oaks Apartments Page 18 Project No. 19003 Renton, WA Coterra Engineering PLLC No oil control requirements are applicable to this project. Req. #6 Aquifer Protection Area The proposed project site is not within an Aquifer Protection Area per City of Renton mapping. SECTION III – OFFSITE ANALYSIS Task 1 – Study Area Definition and Maps Maps of the project site and surrounding area were obtained from the King County GIS website. Topographical site information is from the topographical survey for the project. Storm drainage system maps were compiled from City of Renton GIS maps and as-built plans. Aerial images were obtained from Google Earth. Task 2 – Resource Review The City of Renton Public Works Department was contacted regarding the resources listed in section 2.3.1.1 of the 2017 City of Renton Surface Water Design Manual. The following is a summary of the resource review: Adopted Basin Plans o City of Renton Basin Name: John’s Creek Basin Basin Reconnaissance Summary Reports o None completed to our knowledge. Floodplain/Floodway (FEMA) Maps o The site is not within a floodplain or floodway per FEMA mapping. Other Offsite Analysis Reports o Sunset Terrace Regional Stormwater Facility Final TIR Environmentally Sensitive Areas Map o There are no Environmentally Sensitive areas mapped within the vicinity of the site. USDA Soils Survey o A geotech report has been completed and site soils are primarily medium dense sand with silt that was underlain by impermeable glacial till soil. Wetlands Inventory Maps o There are no Wetlands mapped within the vicinity of the site. Sunset Oaks Apartments Page 19 Project No. 19003 Renton, WA Coterra Engineering PLLC Task 3 – Field Inspection A field inspection site visit was conducted on May 10, 2019. Due to recent construction of the Sunset Terrace Regional Stormwater Facility, the adjacent storm drainage system has been recently updated. The storm drainage is conveyed south and west from Glennwood Ave NE before connecting into the existing system on NE Sunset Blvd, where larger diameter conveyance piping flows west towards Lake Washington beyond ¼ mile downstream from the site. The entire downstream system is comprised of closed pipe conveyance. No known open drainage complaints are associated with the downstream conveyance system. Task 4 – Drainage System Description and Problem Description There are no known problems with the downstream system. Task 5 – Mitigation of Existing or Potential Problems Based on the requirements for the design of the proposed drainage systems, no negative impacts to the systems downstream of the project site are anticipated. Existing Upslope Drainage Areas There is no significant upslope unmitigated drainage areas flowing onto the proposed project site. Sunset Oaks Apartments Page 20 Project No. 19003 Renton, WA Coterra Engineering PLLC FIGURE 6 – DOWNSTREAM DRAINAGE SYSTEM Sunset Oaks Apartments Page 21 Project No. 19003 Renton, WA Coterra Engineering PLLC SECTION IV – FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN Flow Control The project site is located in a Peak Flow Control Standard area per the 2017 City of Renton Surface Water Design Manual. This standard requires that the developed site discharge rates match the existing site conditions discharge rates for the 2-, 10-, and 100- year return periods. The proposed improvements will create more than 2,000 SF of new plus replaced imperious surfaces, therefore the project is required to meet the flow control standard as well as implement on-site flow control BMPs. MGS Flood stormwater modeling program – utilizing a continuous hydrologic model – was implemented to size a detention facility which matched the existing site discharge rates for the 2-, 10-, and 100-year return events. A detention tank was sized in MGS Flood to meet the flow control requirement. Based on the MGS Flood analysis, an 1039 CF detention tank is required for the proposed project. The MGS Flood calculations are included in Appendix B of this report. The proposed detention tank was designed per the City of Renton SWDM requirements including 0.5’ sediment storage (dead storage). Sizing details are shown on the Storm Drainage Plan, Civil Details, and appendices. Updated detention calculations included in this submittal accounted for the bypass areas which are targeted onsite areas for flow control which cannot be captured by gravity and routed to the onsite detention tank. MGS Flood calculations include this bypass area, as shown in Figure 5, in the detention calculations such that the 2, 10, and 100 year peaks are matched at the point of compliance downstream of and including the bypass area. On-Site Flow Control BMPs The proposed site is classified as a Large Lot BMP Site as the proposed site is over 22,000 SF. Implementation of On-Site Flow Control BMPs is therefore required per Core Requirement #9. On-site BMPs are evaluated for targeted surfaces, per the list from section 1.2.9.2.2 for Large Lot BMP Projects in the 2017 City of Renton Surface Water Design Manual. Analysis of feasibility of the on-site BMPs from the SWDM list follow in order per SWDM feasibility determination instructions. Full Dispersion: Infeasible. Per on-site BMP infeasibility criteria in section C.2.1.1, the total area of impervious surfaces plus non-native pervious surfaces on the project site exceed 35% of the total site area. Full Infiltration: Infeasible. Per Minimum Design Requirements for Full Infiltration in section C.2.2.2, existing soils must be “coarse sands or cobbles or medium sands.” Soils collected in on-site borings per the Geotechnical Engineering Report prepared by Zipper Geo Associates, LLC, dated 11/5/2019, are classified dense to dense sand Sunset Oaks Apartments Page 22 Project No. 19003 Renton, WA Coterra Engineering PLLC with variable silt and gravel contents. Below this layer was encountered very dense sand with variable silt and gravel contents that the geotechnical engineer interpreted to be glacial till. These soils were found at a depth of typical on-site infiltration facilities or infiltration BMPs. Limited Infiltration: Infeasible. As described above, the geotechnical investigation has determined that the project site is underlain by glacial till. Per Zipper Geo Associates 11/5/2019 report: “The SWDM requires that the measured distance (separation) between the bottom of the infiltration device and top of an impermeable layer be at least 3 feet. The recommended depth to hardpan at this site is 3 feet below existing site grade. The bottom of an infiltration device at this site would be located below existing site grades and therefore the minimum separation distance is not achievable. As such, limited infiltration is not feasible.” Bioretention: Infeasible. Bioretention is considered infeasible for projects that cannot meet the minimum design requirements for bioretention. Per section C2.6 of the City of Renton SWDM, “ Many locations in the City have soils that are underlain by a compacted layer of soil (i.e., glacial till or hardpan) which severely limits soaking capacity and causes water to perch on the relatively impervious layer during the wet season. This can make bioretention impracticable, unreliable, and reduce plant survivability in the bioretention system.” Per the Geotechnical Engineering Report prepared by Zipper Geo Associates, dated 11/5/2019, “Our explorations encountered glacial till at a depth of about 3 to 5 feet below existing site grade. For purposes of stormwater infiltration, glacial till (or hardpan) is generally considered a hydraulically restrictive layer, or essentially impermeable for purposes of stormwater infiltration. As such, it is our opinion that sufficient permeable soils do not exist at the site and therefore stormwater infiltration is not feasible, in our opinion.” Based on the project geotechnical engineer guidance, bioretention is not feasible on the project site. Permeable Pavement: Feasible and Required Implementation Per Project Conditions. Per agreed upon terms between Sunset Oaks Apartments project owner/agents (Renton Housing Authority) and reviewing agencies (City of Renton, NOAA, NMFS) to maintain compliance with existing conditions of approval for the Sunset Terrace Redevelopment Project, Sunset Oaks Apartments project will implement permeable pavements for all at-grade hard surfaces throughout project site and any proposed sidewalks as part of required frontage improvements. Per the geotechnical engineer’s recommendation, a 6 inch sand layer is proposed under the permeable pavement section. The permeable pavement is not proposed to meet the Enhanced Basic Water Quality requirement for the targeted onsite surfaces, but will be utilized as an On-Site Flow Control BMP to further mitigate developed hard surfaces on the project site. Perforated underdrains are proposed within the aggregate base course of the permeable pavement section and are shown graphically on sheet C4.0. Sunset Oaks Apartments Page 23 Project No. 19003 Renton, WA Coterra Engineering PLLC Basic Dispersion: o Splash blocks: Infeasible. Required 50’ vegetated flow path is infeasible based on proposed site design. o Rock pads: Infeasible. Required 50’ vegetated flow path is infeasible based on proposed site design. o Gravel-filled trenches: Infeasible. Per section C.2.4.4, setbacks of at least 10’ from buildings and 5’ from property line are required. Proposed site layout cannot accommodate 25’ flowpath with required setbacks. o Sheet flow: Infeasible. Required 10’ vegetated flow path located on the project property is infeasible based on proposed site design. Per 1.2.9.2.2 of the SWDM, for projects that will result in an impervious surface coverage greater than 65% on the buildable portion of the site/lot, on-site BMPs must be applied to 20% of the target impervious surfaces. The use of permeable pavement as an On-Site BMP for all the project hardscape areas exceeds the 20% requirement. Soil Amendment: Feasible. New and replaced pervious surfaces within the project limits will implement soil amendment per the soil quality and depth requirements of section C2.13 Water Quality The proposed new and replaced pollution-generating impervious surfaces (PGIS) on the project site trigger the requirement for water quality treatment of targeted surfaces. Per the City of Renton SWDM, the project site is within the Basin Water Quality Area; but the proposed site land use of multi-family housing triggers the Enhanced Basic Water Quality Menu. The proposed project will provide treatment of targeted PGIS as outlined by the Enhanced Basic Water Quality Menu. This will be provided by an Oldcastle BioPod media filtration vault, sized using MGS Flood software to treat the full 2-year release rate from the detention tank. The detention tank and onsite storm drainage system have been designed to capture as much of the proposed impervious surfaces for the project as possible based on proposed topography – which includes the runoff from all three proposed buildings. As a result, all targeted PGIS and non-targeted new impervious surfaces are routed through the water quality facility – including building roofs. No stormwater covenants are required for roofing materials as water quality treatment is provided for these surfaces by the proposed facility. Sizing calculations are provided in Appendix C. ROW Water Quality Per City of Renton requirements, a bioretention cell has been provided adjacent to the project site on Harrington Ave NE. Taking into consideration the full tributary area of the upstream ROW area, including ½ the existing roadway – as shown graphically on Figure coterra 321 3rd Avenue South, Suite 406Seattle, Washington 98104206.596.7115 coterraengineering.com ENGINEERING PLLC Sunset Oaks Apartments Page 24 Project No. 19003 Renton, WA Coterra Engineering PLLC 7, the bioretention cell has been designed to meet the SWDM requirement for water quality treatment and treat a minimum of 91% of the volume of runoff from the water quality treatment design storm for the full tributary upstream area. Figure 7 for a graphical depiction and calculations within Appendix C. Table 3 – Harrington Ave NE Bioretention Tributary Area (Acres) Roadway (PGIS) Sidewalk (Impervious) Landscape (Pervious) Total Area Harrington Ave NE Bioretention Cell 0.264 0.061 0.110 0.435 Based on the 0.435 acre tributary area, a 164 square foot bottom area bioretention cell with 3:1 side slopes was sized using MGS Flood to confirm that a minimum of 91% of runoff volume from the tributary drainage area is treated by the proposed bioretention cell. The bioretention cell is detailed on the Paving and Grading Plan and the Storm Drainage Plan. Detailed MGS Flood calculations are included in Appendix C. SECTION V – CONVEYANCE SYSTEM DESIGN AND ANALYSIS The new conveyance system has been designed to convey, per SWDM requirements, at least the 25-year peak flow rate from the developed site. Conveyance capacity calculations are included in Appendix D. This additionally includes a 100-year peak flow backwater calculation for the onsite storm system from the new public 18” storm main in Glennwood continuing onsite to the proposed detention tank. No backwater effects are anticipated. SECTION VI – SPECIAL REPORTS AND STUDIES A geotechnical analysis of the project site was performed and is included in Appendix I. SECTION VII – OTHER PERMITS In addition to the Site Plan Review, a Civil Construction Permit from the City of Renton is required, as well as an NPDES permit from the Washington State DOE for the discharge of construction stormwater from the project site. SECTION VIII – EROSION AND SEDIMENT CONTROL ESC Measures are being addressed as follows: Clearing Limits: Clearing limits are being delineated by perimeter silt fencing and chain link fencing. Sunset Oaks Apartments Page 25 Project No. 19003 Renton, WA Coterra Engineering PLLC Cover Measures: Temporary cover shall be installed if an area is to remain unworked for more than seven days during the dry season (May 1 to September 30) or for more than two consecutive working days during the wet season (October 1 to April 30). Any area to remain unworked for more than 30 days shall be seeded or sodded, unless the City of Renton determines that winter weather makes vegetation establishment infeasible. Perimeter Protection: Perimeter protection will be implemented by silt fencing around the site perimeter where drainage paths require. Traffic Area Stabilization: A stabilized construction entrance will be built for construction traffic. Sediment Retention: Catch basin protection will be provided on all drainage inlets on, adjacent to, and downstream of the project site. Surface Water Control: Surface water will be collected and conveyed via swales with check dams as necessary. Dust Control: Dust control, if required, will be provided through the limited use of water trucks. Stormwater Pollution Prevention and Spill Control (SWPPS) Based on existing topography, proposed grading on the project just includes minor grading for building pads, proposed parking areas, and the proposed alley through the project site. Contractor shall install and maintain BMPs during construction to prevent the tracking of sediments offsite and spread of sediment- laden water. BMPs will include stabilized construction entrance(s) and tire wash stations as needed to control tracking of sediments off the project site. Additionally, the project proposes to implement the following SWPPS measures per the 2016 King County SWDM (Appendix D) specifications as necessary: o Section D.2.2.1 Concrete Handling o Section D.2.2.2 Concrete Washout Area o Section D.2.2.3 Sawcutting and Surfacing Pollution Prevention o Section D.2.2.4 Material Delivery, Storage and Containment o Section D.2.2.10 Maintain Protective BMPs o Section D.2.2.11 Manage the Project Proposed grading work will be performed in the summer months and building pads establish and foundations poured prior to the end of the Dry Season (September 30) in Fall 2020. Final restoration of cleared and disturbed areas will be per landscape plan. As required by the NPDES permit obtained for the project site from Washington State DOE, the contractor will prepare and implement a final CSWPP for the project. Sunset Oaks Apartments Page 26 Project No. 19003 Renton, WA Coterra Engineering PLLC SECTION IX – BOND QUANTITIES AND DECLARATION OF COVENANTS A bond quantity worksheet for the proposed improvements is included with this submittal in Appendix F. There are two Declaration of Covenants which are required for the proposed project; one for inspection and maintenance of proposed stormwater facilities; and one for the inspection and maintenance of the proposed on-site BMPs. A draft version of these required covenants are provided as one document as allowed by the City of Renton. The Declaration of Covenants can be found in Appendix G. Covenant be signed and notarized prior to recording. SECTION X – OPERATIONS AND MAINTENANCE MANUAL An operation and maintenance manual which outlines required regular maintenance necessary for the proposed stormwater facilities is provided. The Operations & Maintenance Manual is provided in Appendix H. The maintenance of the stormwater facilities will be performed by Renton Housing Authority. Appendix A Civil Plans IN COMPLIANCE WITH CITY OF RENTON STANDARDS 5705'6.#0'0'4'06109# 5705'61#-5#2#46/'065coterra 321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.com ENGINEERING PLLC 5705'61#-5#2#46/'06524 Ä.7# Ä% Ä6'&ÄÄ IN COMPLIANCE WITH CITY OF RENTON STANDARDS 5705'6.#0'0'4'06109# 5705'61#-5#2#46/'065coterra 321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.com ENGINEERING PLLC 5705'61#-5#2#46/'06524 Ä.7# Ä% Ä6'&ÄÄ NO.DATEREMARKISSUE DATE:DRAWN BY:CHECKED BY:Sunset CrestTownhomesGlennwood Ave,Renton, WA.....................12.19.18MBPAPPUD SUBMITTALSHEET NO:SHEET TITLE:177 Western Avenue West Suite 266Seattle, WA 98119coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLCIN COMPLIANCE WITH CITY OF RENTON STANDARDS5705'6.#0'0'4'06109#5705'61#-5#2#46/'065coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLC5705'61#-5#2#46/'065 24 Ä.7# Ä% Ä 6'&ÄÄ4Ä:::::: NO.DATEREMARKISSUE DATE:DRAWN BY:CHECKED BY:Sunset CrestTownhomesGlennwood Ave,Renton, WA.....................12.19.18MBPAPPUD SUBMITTALSHEET NO:SHEET TITLE:177 Western Avenue West Suite 266Seattle, WA 98119coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLCIN COMPLIANCE WITH CITY OF RENTON STANDARDS5705'6.#0'0'4'06109#5705'61#-5#2#46/'065coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLC5705'61#-5#2#46/'065 24 Ä.7# Ä% Ä 6'&ÄÄ4Ä:::::: NO.DATEREMARKISSUE DATE:DRAWN BY:CHECKED BY:Sunset CrestTownhomesGlennwood Ave,Renton, WA.....................12.19.18MBPAPPUD SUBMITTALSHEET NO:SHEET TITLE:177 Western Avenue West Suite 266Seattle, WA 98119coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLCIN COMPLIANCE WITH CITY OF RENTON STANDARDS5705'6.#0'0'4'06109#5705'61#-5#2#46/'065coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLC5705'61#-5#2#46/'065 24 Ä.7# Ä% Ä 6'&ÄÄ4Ä:::::: NO.DATEREMARKISSUE DATE:DRAWN BY:CHECKED BY:Sunset CrestTownhomesGlennwood Ave,Renton, WA.....................12.19.18MBPAPPUD SUBMITTALSHEET NO:SHEET TITLE:177 Western Avenue West Suite 266Seattle, WA 98119coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLCIN COMPLIANCE WITH CITY OF RENTON STANDARDS5705'6.#0'0'4'06109#5705'61#-5#2#46/'065coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLC5705'61#-5#2#46/'065 24 Ä.7# Ä% Ä 6'&ÄÄ4Ä:::::: NO.DATEREMARKISSUE DATE:DRAWN BY:CHECKED BY:Sunset CrestTownhomesGlennwood Ave,Renton, WA.....................12.19.18MBPAPPUD SUBMITTALSHEET NO:SHEET TITLE:177 Western Avenue West Suite 266Seattle, WA 98119coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLCIN COMPLIANCE WITH CITY OF RENTON STANDARDS5705'6.#0'0'4'06109#5705'61#-5#2#46/'065coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLC5705'61#-5#2#46/'065 24 Ä.7# Ä% Ä 6'&ÄÄ4Ä:::::: NO.DATEREMARKISSUE DATE:DRAWN BY:CHECKED BY:Sunset CrestTownhomesGlennwood Ave,Renton, WA.....................12.19.18MBPAPPUD SUBMITTALSHEET NO:SHEET TITLE:177 Western Avenue West Suite 266Seattle, WA 98119coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLCIN COMPLIANCE WITH CITY OF RENTON STANDARDS5705'6.#0'0'4'06109#5705'61#-5#2#46/'065coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLC5705'61#-5#2#46/'065 24 Ä.7# Ä% Ä 6'&ÄÄ4Ä:::::: NO.DATEREMARKISSUE DATE:DRAWN BY:CHECKED BY:Sunset CrestTownhomesGlennwood Ave,Renton, WA.....................12.19.18MBPAPPUD SUBMITTALSHEET NO:SHEET TITLE:177 Western Avenue West Suite 266Seattle, WA 98119coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLCIN COMPLIANCE WITH CITY OF RENTON STANDARDS5705'6.#0'0'4'06109#5705'61#-5#2#46/'065coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLC5705'61#-5#2#46/'065 24 Ä.7# Ä% Ä 6'&ÄÄ4Ä:::::: NO.DATEREMARKISSUE DATE:DRAWN BY:CHECKED BY:Sunset CrestTownhomesGlennwood Ave,Renton, WA.....................12.19.18MBPAPPUD SUBMITTALSHEET NO:SHEET TITLE:177 Western Avenue West Suite 266Seattle, WA 98119coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLCIN COMPLIANCE WITH CITY OF RENTON STANDARDS5705'6.#0'0'4'06109#5705'61#-5#2#46/'065coterra321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.comENGINEERING PLLC5705'61#-5#2#46/'065 24 Ä.7# Ä% Ä 6'&ÄÄ4Ä:::::: IN COMPLIANCE WITH CITY OF RENTON STANDARDS 5705'6.#0'0'4'06109# 5705'61#-5#2#46/'065coterra 321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.com ENGINEERING PLLC 5705'61#-5#2#46/'06524 Ä.7# Ä% Ä6'&ÄÄ IN COMPLIANCE WITH CITY OF RENTON STANDARDS 5705'6.#0'0'4'06109# 5705'61#-5#2#46/'065coterra 321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.com ENGINEERING PLLC 5705'61#-5#2#46/'06524 Ä.7# Ä% Ä6'&ÄÄ IN COMPLIANCE WITH CITY OF RENTON STANDARDS 5705'6.#0'0'4'06109# 5705'61#-5#2#46/'065coterra 321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.com ENGINEERING PLLC 5705'61#-5#2#46/'06524 Ä.7# Ä% Ä6'&ÄÄ IN COMPLIANCE WITH CITY OF RENTON STANDARDS 5705'6.#0'0'4'06109# 5705'61#-5#2#46/'065coterra 321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.com ENGINEERING PLLC 5705'61#-5#2#46/'06524 Ä.7# Ä% Ä6'&ÄÄ IN COMPLIANCE WITH CITY OF RENTON STANDARDS 5705'6.#0'0'4'06109# 5705'61#-5#2#46/'065coterra 321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.com ENGINEERING PLLC 5705'61#-5#2#46/'06524 Ä.7# Ä% Ä6'&ÄÄ IN COMPLIANCE WITH CITY OF RENTON STANDARDS 5705'6.#0'0'4'06109# 5705'61#-5#2#46/'065coterra 321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.com ENGINEERING PLLC 5705'61#-5#2#46/'06524 Ä.7# Ä% Ä6'&ÄÄ IN COMPLIANCE WITH CITY OF RENTON STANDARDS 5705'6.#0'0'4'06109# 5705'61#-5#2#46/'065coterra 321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.com ENGINEERING PLLC 5705'61#-5#2#46/'06524 Ä.7# Ä% Ä6'&ÄÄ IN COMPLIANCE WITH CITY OF RENTON STANDARDS 5705'6.#0'0'4'06109# 5705'61#-5#2#46/'065coterra 321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.com ENGINEERING PLLC 5705'61#-5#2#46/'06524 Ä.7# Ä% Ä6'&ÄÄ IN COMPLIANCE WITH CITY OF RENTON STANDARDS 5705'6.#0'0'4'06109# 5705'61#-5#2#46/'065coterra 321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.com ENGINEERING PLLC 5705'61#-5#2#46/'06524 Ä.7# Ä% Ä6'&ÄÄ IN COMPLIANCE WITH CITY OF RENTON STANDARDS 5705'6.#0'0'4'06109# 5705'61#-5#2#46/'065coterra 321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.com ENGINEERING PLLC 5705'61#-5#2#46/'06524 Ä.7# Ä% Ä6'&ÄÄ IN COMPLIANCE WITH CITY OF RENTON STANDARDS 5705'6.#0'0'4'06109# 5705'61#-5#2#46/'065coterra 321 3rd Ave South, Suite 406Seattle, Washington 98104ph 206.596.7115coterraengineering.com ENGINEERING PLLC 5705'61#-5#2#46/'06524 Ä.7# Ä% Ä6'&ÄÄISOMETRIC VIEW A PLAN VIEW A BPU-IB Bioretention/ Biofiltration Ph: 800.579.8819 | oldcastlestormwater.com INFRASTRUCTURE < NA US Patents Pending SECTION A-A BPU-IB Bioretention/ Biofiltration Ph: 800.579.8819 | oldcastlestormwater.com INFRASTRUCTURE < NR US Patents Pending TREATMENT FLOW CAPACITY 2 (GPM/CFS) TREATMENT FLOW CAPACITY 3 (GPM/CFS)A DIM B DIM A1 DIM B1 DIM BPU-IB-46 4'6'5'7'25.6 / 0.057 28.8 / 0.064 BPU-IB-48 4'8'5'9'38.4 / 0.086 43.2 / 0.096 BPU-IB-412 4'12'5'13'64.0 / 0.143 72.0 / 0.160 BPU-IB-66 6'6'7'7'38.4 / 0.086 43.2 / 0.096 BPU-IB-68 6'8'7'9'57.6 / 0.128 64.8 / 0.144 BPU-IB-612 6'12'7'13'96.0 / 0.214 108.0 / 0.241 BPU-IB-816 8'16'9'17'179.2 / 0.399 201.6 / 0.449 BioPod >Biofilter Underground Vault with Internal BypassBioPod>Biofilter Underground Vault with Internal Bypass 1 All Dimensions Are Nominal 2 Based on an WA Ecology GULD Approval for Basic, Enhanced & Phosphorus. At 1.60 gpm/sf Media Surface Area. 3 Based on an NJCAT Verification & NJ DEP Certification. At 1.80 gpm/sf Media Surface Area. Appendix B Flow Control/Detention Calculations EX Onsite EX Glenwood ROW EX Harrington ROW New Copy Lnk1 PR Bypass Glennwood Ave Harrington Ave Det 36 in-147 lf New Copy Lnk2 Detention Pipe Volume Calculator Blue Indicates Data Entry Cells, the rest are calculated. Storage Volume Provided by Horizontal Pipe of Diameter d Pipe Diameter (d)3.0 ft Pipe Length 147 ft Overflow Elevation:103.00 ft Pond Volume at Overflow (cu ft):1007 Target Volume from MGSFlood:1937 Note: Volume is increased by 1 for Elevations Greater than Pipe Diameter Pond Volume Table Because Routing Routine Requires Increasing Pond Volume Circular Section Geometry Read from CircularSections Tab *** Copy Table below to MGSFlood Program Elevation Volume Input Screen elev.Wetted Area storage storage DON'T INCLUDE THE COLUMN HEADINGS! ft y/d s.f.cu.ft.(ac.ft) ELEV (FT)Top Area (Dummy)VOLUME (CU FT) 100.00 0.000 0.000 0 0 100.00 10.0 0.0. 100.20 0.070 0.218 32 0.001 100.20 10.1 32.0. 100.40 0.130 0.540 79 0.002 100.40 10.2 79.4. 100.60 0.200 1.006 148 0.003 100.60 10.3 147.9. 100.80 0.270 1.540 226 0.005 100.80 10.4 226.4. 101.00 0.330 2.034 299 0.007 101.00 10.5 299.0. 101.20 0.400 2.641 388 0.009 101.20 10.6 388.2. 101.40 0.470 3.264 480 0.011 101.40 10.7 479.9. 101.60 0.530 3.804 559 0.013 101.60 10.8 559.2. 101.80 0.600 4.428 651 0.015 101.80 10.9 650.9. 102.00 0.670 5.035 740 0.017 102.00 11.0 740.1. 102.20 0.730 5.529 813 0.019 102.20 11.1 812.7. 102.40 0.800 6.062 891 0.020 102.40 11.2 891.2. 102.60 0.870 6.529 960 0.022 102.60 11.3 959.7. 102.80 0.930 6.851 1007 0.023 102.80 11.4 1007.1. 103.00 1.000 7.069 1039 0.024 103.00 11.5 1039.1. 103.20 1.070 7.069 1039 0.024 103.20 11.6 1040.1. 103.40 1.130 7.069 1039 0.024 103.40 11.7 1041.1. 103.60 1.200 7.069 1039 0.024 103.60 11.8 1042.1. 103.80 1.270 7.069 1039 0.024 103.80 11.9 1043.1. 104.00 1.330 7.069 1039 0.024 104.00 12.0 1044.1. 104.20 1.400 7.069 1039 0.024 104.20 12.1 1045.1. 104.40 1.470 7.069 1039 0.024 104.40 12.2 1046.1. 104.60 1.530 7.069 1039 0.024 104.60 12.3 1047.1. 104.80 1.600 7.069 1039 0.024 104.80 12.4 1048.1. 105.00 1.670 7.069 1039 0.024 105.00 12.5 1049.1. 105.20 1.730 7.069 1039 0.024 105.20 12.6 1050.1. 105.40 1.800 7.069 1039 0.024 105.40 12.7 1051.1. 105.60 1.870 7.069 1039 0.024 105.60 12.8 1052.1. 105.80 1.930 7.069 1039 0.024 105.80 12.9 1053.1. 106.00 2.000 7.069 1039 0.024 106.00 13.0 1054.1. 5/26/2020 PondPipe 3ft.xls ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.38 Program License Number: 201510001 Project Simulation Performed on: 05/25/2020 6:16 PM Report Generation Date: 05/26/2020 4:46 AM ————————————————————————————————— Input File Name: RHASO-MGS Flood - CCP - 3ft.fld Project Name: 19003 - RHA Sunset Oaks Analysis Title: Detention Sizing Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 13 Full Period of Record Available used for Routing Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961040 Puget East 40 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 1.249 1.249 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 1.249 1.249 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 3 ---------- Subbasin : EX Onsite ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.803 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 2 0.000 Impervious 0.250 ---------------------------------------------- Subbasin Total 1.053 ---------- Subbasin : EX Glenwood ROW ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.030 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000Green Roof 0.000 User 2 0.000 Impervious 0.060 ---------------------------------------------- Subbasin Total 0.090 ---------- Subbasin : EX Harrington ROW ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.038 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 2 0.000 Impervious 0.068 ---------------------------------------------- Subbasin Total 0.106 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 4 ---------- Subbasin : PR ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.058 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 2 0.000 Impervious 0.720 ---------------------------------------------- Subbasin Total 0.778 ---------- Subbasin : Bypass ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.207 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 2 0.000 Impervious 0.068 ---------------------------------------------- Subbasin Total 0.275 ---------- Subbasin : Glennwood Ave ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.051 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 2 0.000 Impervious 0.039 ----------------------------------------------Subbasin Total 0.090 ---------- Subbasin : Harrington Ave ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.040 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 2 0.000 Impervious 0.066 ---------------------------------------------- Subbasin Total 0.106 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Copy Lnk1 Link Type: Copy Downstream Link: None ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ------------------------------------------ Link Name: Det 36 in-147 lf Link Type: Structure Downstream Link Name: New Copy Lnk2 User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 100.00 0. 100.20 32. 100.40 79. 100.60 148. 100.80 226. 101.00 299. 101.20 388. 101.40 480. 101.60 559. 101.80 651. 102.00 740. 102.20 813. 102.40 891. 102.60 960. 102.80 1007. 103.00 1039. Massmann Infiltration Option Used Hydraulic Conductivity (in/hr) : 0.00 Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00Common Length (ft) : 0.000 Riser Crest Elevation : 103.00 ft Hydraulic Structure Geometry Number of Devices: 2 ---Device Number 1 --- Device Type : Circular Orifice Control Elevation (ft) : 100.50 Diameter (in) : 2.02 Orientation : Horizontal Elbow : No ---Device Number 2 --- Device Type : Circular Orifice Control Elevation (ft) : 102.50 Diameter (in) : 2.90 Orientation : Horizontal Elbow : Yes ------------------------------------------ Link Name: New Copy Lnk2 Link Type: Copy Downstream Link: None **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 3 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 4 Number of Links: 2 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: EX Onsite 98.135 Subbasin: EX Glenwood ROW 3.666 Subbasin: EX Harrington ROW 4.644 Link: New Copy Lnk1 0.000 _____________________________________ Total: 106.445 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: PR 7.088 Subbasin: Bypass 25.298 Subbasin: Glennwood Ave 6.233 Subbasin: Harrington Ave 4.888 Link: Det 36 in-147 lf Not Computed Link: New Copy Lnk2 0.000 _____________________________________ Total: 43.507 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.674 ac-ft/year, Post Developed: 0.275 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: New Copy Lnk1 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 344.64 Inflow Volume Including PPT-Evap (ac-ft): 344.64 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 344.64 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ********** Link: New Copy Lnk2 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 473.27 Inflow Volume Including PPT-Evap (ac-ft): 473.27 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 473.27 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: New Copy Lnk1 Scenario Postdeveloped Compliance Link: New Copy Lnk2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.221 2-Year 0.202 5-Year 0.299 5-Year 0.299 10-Year 0.405 10-Year 0.371 25-Year 0.543 25-Year 0.514 50-Year 0.713 50-Year 0.584 100-Year 0.828 100-Year 0.761 200-Year 0.871 200-Year 0.795 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals Appendix C Water Quality Calculations ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.38 Program License Number: 201510001 Project Simulation Performed on: 05/25/2020 6:16 PM Report Generation Date: 05/26/2020 4:46 AM ————————————————————————————————— Input File Name: RHASO-MGS Flood - CCP - 3ft.fld Project Name: 19003 - RHA Sunset Oaks Analysis Title: Detention Sizing Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 13 Full Period of Record Available used for Routing Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961040 Puget East 40 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 1.249 1.249 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 1.249 1.249 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 3 ---------- Subbasin : EX Onsite ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.803 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 2 0.000 Impervious 0.250 ---------------------------------------------- Subbasin Total 1.053 ---------- Subbasin : EX Glenwood ROW ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.030 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 WQ VAULT SIZED TO FULL 2-YR RELEASE RATE FROM DETENTION TANK Wetland 0.000Green Roof 0.000 User 2 0.000 Impervious 0.060 ---------------------------------------------- Subbasin Total 0.090 ---------- Subbasin : EX Harrington ROW ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.038 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 2 0.000 Impervious 0.068 ---------------------------------------------- Subbasin Total 0.106 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 4 ---------- Subbasin : PR ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.058 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 2 0.000 Impervious 0.720 ---------------------------------------------- Subbasin Total 0.778 ---------- Subbasin : Bypass ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.207 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 2 0.000 Impervious 0.068 ---------------------------------------------- Subbasin Total 0.275 ---------- Subbasin : Glennwood Ave ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.051 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 2 0.000 Impervious 0.039 ----------------------------------------------Subbasin Total 0.090 ---------- Subbasin : Harrington Ave ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.040 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 2 0.000 Impervious 0.066 ---------------------------------------------- Subbasin Total 0.106 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Copy Lnk1 Link Type: Copy Downstream Link: None ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ------------------------------------------ Link Name: Det 36 in-147 lf Link Type: Structure Downstream Link Name: New Copy Lnk2 User Specified Elevation Volume Table Used Elevation (ft) Pond Volume (cu-ft) 100.00 0. 100.20 32. 100.40 79. 100.60 148. 100.80 226. 101.00 299. 101.20 388. 101.40 480. 101.60 559. 101.80 651. 102.00 740. 102.20 813. 102.40 891. 102.60 960. 102.80 1007. 103.00 1039. Massmann Infiltration Option Used Hydraulic Conductivity (in/hr) : 0.00 Depth to Water Table (ft) : 100.00 Bio-Fouling Potential : Low Maintenance : Average or Better Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 12.00Common Length (ft) : 0.000 Riser Crest Elevation : 103.00 ft Hydraulic Structure Geometry Number of Devices: 2 ---Device Number 1 --- Device Type : Circular Orifice Control Elevation (ft) : 100.50 Diameter (in) : 2.02 Orientation : Horizontal Elbow : No ---Device Number 2 --- Device Type : Circular Orifice Control Elevation (ft) : 102.50 Diameter (in) : 2.90 Orientation : Horizontal Elbow : Yes ------------------------------------------ Link Name: New Copy Lnk2 Link Type: Copy Downstream Link: None **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 3 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 4 Number of Links: 2 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: EX Onsite 98.135 Subbasin: EX Glenwood ROW 3.666 Subbasin: EX Harrington ROW 4.644 Link: New Copy Lnk1 0.000 _____________________________________ Total: 106.445 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: PR 7.088 Subbasin: Bypass 25.298 Subbasin: Glennwood Ave 6.233 Subbasin: Harrington Ave 4.888 Link: Det 36 in-147 lf Not Computed Link: New Copy Lnk2 0.000 _____________________________________ Total: 43.507 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.674 ac-ft/year, Post Developed: 0.275 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: New Copy Lnk1 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 344.64 Inflow Volume Including PPT-Evap (ac-ft): 344.64 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 344.64 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ********** Link: New Copy Lnk2 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 473.27 Inflow Volume Including PPT-Evap (ac-ft): 473.27 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 473.27 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: New Copy Lnk1 Scenario Postdeveloped Compliance Link: New Copy Lnk2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.221 2-Year 0.202 5-Year 0.299 5-Year 0.299 10-Year 0.405 10-Year 0.371 25-Year 0.543 25-Year 0.514 50-Year 0.713 50-Year 0.584 100-Year 0.828 100-Year 0.761 200-Year 0.871 200-Year 0.795 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals FULL 2-YR DEVELOPED RELEASE RATE FROM DETENETION TANK ISOMETRIC VIEW BPU-IB C US Patents Pending THIS DOCUMENT IS THE PROPERTY OF OLDCASTLE INFRASTRUCTURE, INC. IT IS SUBMITTED FOR REFERENCE PURPOSES ONLY AND SHALL NOT BE USED IN ANY WAY INJURIOUS TO THE INTERESTS OF SAID COMPANY. COPYRIGHT © 2020 OLDCASTLE INFRASTRUCTURE, INC. ALL RIGHTS RESERVED. BioPodf Biofilter Underground Vault with Internal Bypass d Oldcas tl e d Oldcas tl e d Oldc a st l e Bioretention/ Biofiltration A PLAN VIEW A SECTION A-A BPU-IB C US Patents PendingSAUDFI1325-05 10 USAXXXXTHIS DOCUMENT IS THE PROPERTY OF OLDCASTLE INFRASTRUCTURE, INC. IT IS SUBMITTED FOR REFERENCE PURPOSES ONLY AND SHALL NOT BE USED IN ANY WAY INJURIOUS TO THE INTERESTS OF SAID COMPANY. COPYRIGHT © 2020 OLDCASTLE INFRASTRUCTURE, INC. ALL RIGHTS RESERVED. MODEL VAULT SIZE 1 (ID) VAULT FOOTPRINT 1 (OD) TREATMENT FLOW CAPACITY (GPM/CFS) A DIM B DIM C DIM A1 DIM B1 DIM 1.6 GPM/SF (WA GULD2) 1.8 GPM/SF (NJCAT3) BPU-46IB 4'6'1.5'5'7'25.6 / 0.057 28.8 / 0.064 BPU-48IB 4'8'1.5'5'9'38.4 / 0.086 43.2 / 0.096 BPU-412IB 4'12'1.5'5'13'64.0 / 0.143 72.0 / 0.160 BPU-66IB 6'6'1.5'7'7'38.4 / 0.086 43.2 / 0.096 BPU-68IB 6'8'1.5'7'9'57.6 / 0.128 64.8 / 0.144 BPU-612IB 6'12'2'7'13'91.2 / 0.203 102.6 / 0.229 BPU-812IB 8'12'2'9'13'121.6 / 0.271 136.9 / 0.305 BPU-816IB 8'16'2'9'17'172.8 / 0.385 194.4 / 0.433 BioPodf Biofilter Underground Vault with Internal Bypass fFIDSAUXXXXUSADFI11540010FIDSAUXXXXUSADFI1154 0010 SITE SPECIFIC DATA Structure ID Model Size Orientation (Left or Right) Treatment Flow Rate (cfs) Peak Flow Rate (cfs) Rim Elevation Pipe Data Pipe Location (Front or Side)Pipe Size Pipe Type Invert Elevation Inlet Outlet Notes: 1 All Dimensions are nominal, ID=Inside Dimension, OD=Outside Dimension.2 Treartment flow capacity at 1.6 gpm/sf media surface area based on an WA Ecology GULD Approval for Basic, Enhanced & Phosphorus. 3 Treatment flow capacity at 1.8 gpm/sf media surface area based on an NJCAT Verification & NJ DEP Certification. Bioretention/ Biofiltration BPU-612-IB VAULT (6'x 12'VAULT) ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.38 Program License Number: 201510001 Project Simulation Performed on: 03/10/2020 3:34 PM Report Generation Date: 03/18/2020 8:05 AM ————————————————————————————————— Input File Name: RHASO - Harrington WQ - credit.fld Project Name: RHASO Analysis Title: Water Quality Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 13 Full Period of Record Available used for Routing Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961040 Puget East 40 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.334 0.435 Area of Links that Include Precip/Evap (acres) 0.000 0.004 Total (acres) 0.334 0.439 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Harrington Ave ROW ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.000 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 2 0.000 Impervious 0.334 ---------------------------------------------- Subbasin Total 0.334 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Harrington Ave ROW ---------- -------Area(Acres) -------- Till Forest 0.000 Till Pasture 0.000 Till Grass 0.110 Outwash Forest 0.000 Outwash Pasture 0.000 Outwash Grass 0.000 Wetland 0.000 Green Roof 0.000 User 2 0.000 Impervious 0.325 ---------------------------------------------- Subbasin Total 0.435 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ------------------------------------------ Link Name: New Copy Lnk2 Link Type: Copy Downstream Link: None ------------------------------------------ Link Name: Harrington ROW Bioretention Link Type: Bioretention Facility Downstream Link Name: New Copy Lnk2 Base Elevation (ft) : 340.03 Riser Crest Elevation (ft) : 340.28 Storage Depth (ft) : 0.25 Bottom Length (ft) : 54.7 Bottom Width (ft) : 3.0 Side Slopes (ft/ft) : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 Bottom Area (sq-ft) : 164. Area at Riser Crest El (sq-ft) : 253. (acres) : 0.006 Volume at Riser Crest (cu-ft) : 150. (ac-ft) : 0.003 Infiltration on Bottom only Selected Soil Properties Biosoil Thickness (ft) : 1.50 Biosoil Saturated Hydraulic Conductivity (in/hr) : 6.00 Biosoil Porosity (Percent) : 40.00 Maximum Elevation of Bioretention Soil : 340.03 Native Soil Hydraulic Conductivity (in/hr) : 0.00 Underdrain Present Orifice Present in Under Drain Orifice Control Elevation (ft) : 337.70 Orifice Diameter (in) : 8.000 Riser Geometry Riser Structure Type : Circular Riser Diameter (in) : 6.00 Common Length (ft) : 0.000 Riser Crest Elevation : 340.28 ft Hydraulic Structure Geometry Number of Devices: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 2 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Harrington Ave ROW 0.000 _____________________________________ Total: 0.000 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Harrington Ave ROW 13.443 Link: New Copy Lnk2 0.000 Link: Harrington ROW Biore 0.000 _____________________________________ Total: 13.443 Total Predevelopment Recharge is Less than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.000 ac-ft/year, Post Developed: 0.085 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 2 ********** Link: New Copy Lnk2 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 169.52 Inflow Volume Including PPT-Evap (ac-ft): 169.52 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 169.52 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ********** Link: Harrington ROW Bioretention ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 167.83 Inflow Volume Including PPT-Evap (ac-ft): 169.51 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 154.83, 91.34% Primary Outflow To Downstream System (ac-ft): 169.52 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 91.34% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Harrington Ave ROW Scenario Postdeveloped Compliance Link: New Copy Lnk2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.124 2-Year 0.126 5-Year 0.162 5-Year 0.162 10-Year 0.182 10-Year 0.198 25-Year 0.229 25-Year 0.260 50-Year 0.291 50-Year 0.297 100-Year 0.337 100-Year 0.346 200-Year 0.349 200-Year 0.381 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals Appendix D Conveyance/Backwater Calculations coterra 321 3rd Avenue South, Suite 406Seattle, Washington 98104206.596.7115 coterraengineering.com ENGINEERING PLLC BACKWATER ANALYSIS - PROPOSED PROJECT Project Name: RHA Sunset Oaks - Onsite Backwater Designed By: Max Berde Checked By: Peter Apostol Job Number: 19003 Storm Event:100-YEAR Conveyance System Information Outlet Control Inlet Control Headwater Summation Overtopping Check Pipe Segment Surface Total Length Pipe "n" Down- Down- Up- Up- Pipe Barrel Barrel Critical Critical TW TW Barrel Friction Entrance Entrance Entrance Exit Outlet Inlet Inlet Control Approach Bend Bend Q1 Q3 V1 Junction Head HW (HW - Rim) Over- CB/MH # CB/MH # Flow Flow L Size value Stream Stream Stream Stream Slope Velocity Velocity Depth Depth Elev. Check Hyd. Loss HGL Ke Head Head Control Control Control HW Veloctiy Kb Head Head Loss Elev. Clearance topping Down Up Q Qtot D Invert Rim Invert Rim Head Ratio Rad. Elev. Loss Loss Elev.HW/D Elev. Elev. Head Loss Loss Total Check CFS CFS FT IN FT FT FT FT % FPS FT FT FT FT FT FT FT FT FT FT FT FT FT FT FT CFS CFS FPS FT FT FT FT CB #1 CB #2 0.000 0.93 22.0 8 0.012 336.05 339.26 336.47 340.00 1.91% 2.67 0.11 0.69 0.46 336.72 336.72 0.17 0.11 337.14 0.50 0.06 0.11 337.30 1.35 337.37 337.37 0.11 0.02 0.00 0.93 0.00 2.67 0.00 337.26 -2.74 Okay CB #2 CB #3 0.063 0.93 46.0 8 0.012 336.47 340.00 336.78 341.70 0.67% 2.67 0.11 0.69 0.46 337.26 337.26 0.17 0.23 337.49 0.50 0.06 0.11 337.66 1.35 337.68 337.68 0.10 0.02 0.00 0.87 0.00 2.67 0.00 337.59 -4.11 Okay CB #3 CB #4 0.063 0.87 26.0 8 0.012 336.78 341.70 336.95 342.10 0.65% 2.49 0.10 0.66 0.44 337.59 337.59 0.17 0.11 337.70 0.50 0.05 0.10 337.84 1.35 337.85 337.85 0.08 0.02 0.00 0.81 0.00 2.49 0.00 337.77 -4.33 Okay CB # 4 CB #5 0.805 0.81 72.0 8 0.012 336.95 342.10 337.43 342.50 0.67% 2.31 0.08 0.64 0.47 337.77 337.77 0.17 0.27 338.10 0.50 0.04 0.08 338.22 1.35 338.33 338.33 0.02 0.00 0.00 0.00 2.31 0.00 338.33 -4.17 Okay coterra ENGINEERING PLLC collaborative civil engineering + site development + infrastructure design 19003 Backwater Analysis-Onsite old.xls 3/18/2020 UNIFORM FLOW ANALYSIS Project Name: RHA Sunset Oaks Designed By: Max Berde Checked By: Peter Apostol Job Number: 19003 Storm Event: 100-YEAR CB CB Pipe Q100-yr Manning's "n" Pipe Slope Qf Vf Uniform Uniform Downstream Upstream Size "n" % Pipe Full Pipe Full Flow Velocity Check in cfs unitless cfs ft/s Check *Check ** CB #1 CB #2 8 0.93 0.012 1.91%1.81 5.20 Ok Ok CB #2 CB #3 8 0.93 0.012 0.67%1.08 3.09 Warning!Ok CB #3 CB #4 8 0.87 1.20%0.65%1.06 3.04 Warning!Ok CB # 4 CB #5 8 0.81 0.012 0.67%1.07 3.07 Ok Ok collaborative civil engineering + site development + infrastructure design Appendix E Drainage Review Flowchart SECTION 1.1 DRAINAGE REVIEW 12/12/2016 2017 City of Renton Surface Water Design Manual 1-14 FIGURE 1.1.2.A FLOW CHART FOR DETERMINING TYPE OF DRAINAGE REVIEW REQUIRED Appendix F Bond Quantities Worksheet Planning Division |1055 South Grady Way – 6 th Floor | Renton, WA 98057 (425) 430-7200 Date 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:No Water Service Provided by: If Yes, Provide Forest Practice Permit #:Sewer Service Provided by: 2900 NE 10th St######## (425) 226-1850 Abbreviated Legal Description: 1062 Glenwood Ave NE Glenwood Ave & Harrington Ave Prepared by: FOR APPROVALProject Phase 1 Peter Apostol, PE 35163 Coterra Engineering 321 3rd Ave South, #406, Seattle, WA 98104 (206) 596-7115 peter@coterraengineering.com SITE IMPROVEMENT BOND QUANTITY WORKSHEET PROJECT INFORMATION CITY OF RENTON CITY OF RENTON 1 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 Submittal Engineer Stamp Required (all cost estimates must have original wet stamp and signature) Clearing and Grading Utility Providers N/A Project Location and Description Project Owner Information Sunset Oaks Apartments Renton, WA 98056 7227801315; 7227801290; 7227801310 Renton Housing Authority ##-###### 5/25/2020 Page 2 of 14 Ref 8-H Bond Quantity Worksheet SECTION I PROJECT INFORMATION Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 5/26/2020 CED Permit #:######## UnitReference #Price Unit Quantity CostBackfill & compaction-embankment ESC-1 6.50$ CY Check dams, 4" minus rock ESC-2 SWDM 5.4.6.3 80.00$ Each Catch Basin Protection ESC-3 35.50$ Each 9 319.50Crushed surfacing 1 1/4" minus ESC-4 WSDOT 9-03.9(3)95.00$ CY Ditching ESC-5 9.00$ CY Excavation-bulk ESC-6 2.00$ CY Fence, silt ESC-7 SWDM 5.4.3.1 1.50$ LF 420 630.00Fence, Temporary (NGPE)ESC-8 1.50$ LF Geotextile Fabric ESC-9 2.50$ SY Hay Bale Silt Trap ESC-10 0.50$ Each Hydroseeding ESC-11 SWDM 5.4.2.4 0.80$ SY Interceptor Swale / Dike ESC-12 1.00$ LF Jute Mesh ESC-13 SWDM 5.4.2.2 3.50$ SY Level Spreader ESC-14 1.75$ LF Mulch, by hand, straw, 3" deep ESC-15 SWDM 5.4.2.1 2.50$ SY Mulch, by machine, straw, 2" deep ESC-16 SWDM 5.4.2.1 2.00$ SY Piping, temporary, CPP, 6"ESC-17 12.00$ LF Piping, temporary, CPP, 8"ESC-18 14.00$ LF Piping, temporary, CPP, 12"ESC-19 18.00$ LF Plastic covering, 6mm thick, sandbagged ESC-20 SWDM 5.4.2.3 4.00$ SY Rip Rap, machine placed; slopes ESC-21 WSDOT 9-13.1(2)45.00$ CY Rock Construction Entrance, 50'x15'x1'ESC-22 SWDM 5.4.4.1 1,800.00$ Each 1 1,800.00Rock Construction Entrance, 100'x15'x1'ESC-23 SWDM 5.4.4.1 3,200.00$ Each Sediment pond riser assembly ESC-24 SWDM 5.4.5.2 2,200.00$ Each Sediment trap, 5' high berm ESC-25 SWDM 5.4.5.1 19.00$ LF Sed. trap, 5' high, riprapped spillway berm section ESC-26 SWDM 5.4.5.1 70.00$ LF Seeding, by hand ESC-27 SWDM 5.4.2.4 1.00$ SY Sodding, 1" deep, level ground ESC-28 SWDM 5.4.2.5 8.00$ SY Sodding, 1" deep, sloped ground ESC-29 SWDM 5.4.2.5 10.00$ SY TESC Supervisor ESC-30 110.00$ HR Water truck, dust control ESC-31 SWDM 5.4.7 140.00$ HR UnitReference #Price Unit Quantity Cost EROSION/SEDIMENT SUBTOTAL:2,749.50SALES TAX @ 10%274.95EROSION/SEDIMENT TOTAL:3,024.45 (A) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR EROSION & SEDIMENT CONTROL Description No. (A) WRITE-IN-ITEMS Page 3 of 14 Ref 8-H Bond Quantity Worksheet SECTION II.a EROSION_CONTROL Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 5/26/2020 CED Permit #:######## Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost GENERAL ITEMS Backfill & Compaction- embankment GI-1 6.00$ CY Backfill & Compaction- trench GI-2 9.00$ CY Clear/Remove Brush, by hand (SY)GI-3 1.00$ SY Bollards - fixed GI-4 240.74$ Each Bollards - removable GI-5 452.34$ Each Clearing/Grubbing/Tree Removal GI-6 10,000.00$ Acre 1.053 10,530.00 Excavation - bulk GI-7 2.00$ CYExcavation - Trench GI-8 5.00$ CY 1000 5,000.00 Fencing, cedar, 6' high GI-9 20.00$ LF Fencing, chain link, 4'GI-10 38.31$ LF Fencing, chain link, vinyl coated, 6' high GI-11 20.00$ LF Fencing, chain link, gate, vinyl coated, 20' GI-12 1,400.00$ Each Fill & compact - common barrow GI-13 25.00$ CY 200 5,000.00 Fill & compact - gravel base GI-14 27.00$ CY 500 13,500.00 Fill & compact - screened topsoil GI-15 39.00$ CY 250 9,750.00 Gabion, 12" deep, stone filled mesh GI-16 65.00$ SYGabion, 18" deep, stone filled mesh GI-17 90.00$ SY Gabion, 36" deep, stone filled mesh GI-18 150.00$ SY Grading, fine, by hand GI-19 2.50$ SY Grading, fine, with grader GI-20 2.00$ SY Monuments, 3' Long GI-21 250.00$ Each Sensitive Areas Sign GI-22 7.00$ Each Sodding, 1" deep, sloped ground GI-23 8.00$ SY Surveying, line & grade GI-24 850.00$ Day 3 2,550.00 Surveying, lot location/lines GI-25 1,800.00$ Acre 1.053 1,895.40Topsoil Type A (imported)GI-26 28.50$ CY Traffic control crew ( 2 flaggers )GI-27 120.00$ HR Trail, 4" chipped wood GI-28 8.00$ SY Trail, 4" crushed cinder GI-29 9.00$ SY Trail, 4" top course GI-30 12.00$ SY Conduit, 2"GI-31 5.00$ LF Wall, retaining, concrete GI-32 55.00$ SFWall, rockery GI-33 15.00$ SF SUBTOTAL THIS PAGE:48,225.40 (B)(C)(D)(E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B) (C) Page 4 of 14 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 5/26/2020 CED Permit #:######## Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B) (C) ROAD IMPROVEMENT/PAVEMENT/SURFACINGAC Grinding, 4' wide machine < 1000sy RI-1 30.00$ SY AC Grinding, 4' wide machine 1000-2000sy RI-2 16.00$ SY AC Grinding, 4' wide machine > 2000sy RI-3 10.00$ SY AC Removal/Disposal RI-4 35.00$ SY Barricade, Type III ( Permanent )RI-5 56.00$ LF Guard Rail RI-6 30.00$ LF Curb & Gutter, rolled RI-7 17.00$ LFCurb & Gutter, vertical RI-8 12.50$ LF 450 5,625.00 400 5,000.00 625 7,812.50 Curb and Gutter, demolition and disposal RI-9 18.00$ LF Curb, extruded asphalt RI-10 5.50$ LF Curb, extruded concrete RI-11 7.00$ LF Sawcut, asphalt, 3" depth RI-12 1.85$ LF Sawcut, concrete, per 1" depth RI-13 3.00$ LF Sealant, asphalt RI-14 2.00$ LF Shoulder, gravel, 4" thick RI-15 15.00$ SY Sidewalk, 4" thick RI-16 38.00$ SY 45 1,710.00Sidewalk, 4" thick, demolition and disposal RI-17 32.00$ SY Sidewalk, 5" thick RI-18 41.00$ SY Sidewalk, 5" thick, demolition and disposal RI-19 40.00$ SY Sign, Handicap RI-20 85.00$ Each Striping, per stall RI-21 7.00$ Each Striping, thermoplastic, ( for crosswalk )RI-22 3.00$ SF Striping, 4" reflectorized line RI-23 0.50$ LF Additional 2.5" Crushed Surfacing RI-24 3.60$ SY HMA 1/2" Overlay 1.5" RI-25 14.00$ SYHMA 1/2" Overlay 2"RI-26 18.00$ SY HMA Road, 2", 4" rock, First 2500 SY RI-27 28.00$ SY HMA Road, 2", 4" rock, Qty. over 2500SY RI-28 21.00$ SY HMA Road, 4", 6" rock, First 2500 SY RI-29 45.00$ SY HMA Road, 4", 6" rock, Qty. over 2500 SY RI-30 37.00$ SY HMA Road, 4", 4.5" ATB RI-31 38.00$ SY Gravel Road, 4" rock, First 2500 SY RI-32 15.00$ SYGravel Road, 4" rock, Qty. over 2500 SY RI-33 10.00$ SY Thickened Edge RI-34 8.60$ LF SUBTOTAL THIS PAGE:5,625.00 5,000.00 9,522.50 (B)(C)(D)(E) Page 5 of 14 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 5/26/2020 CED Permit #:######## Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B) (C) PARKING LOT SURFACING No.2" AC, 2" top course rock & 4" borrow PL-1 21.00$ SY 2" AC, 1.5" top course & 2.5" base course PL-2 28.00$ SY 4" select borrow PL-3 5.00$ SY 1.5" top course rock & 2.5" base course PL-4 14.00$ SY SUBTOTAL PARKING LOT SURFACING: (B)(C)(D)(E) LANDSCAPING & VEGETATION No.Street Trees LA-1 Median Landscaping LA-2 Right-of-Way Landscaping LA-3Wetland Landscaping LA-4 SUBTOTAL LANDSCAPING & VEGETATION: (B)(C)(D)(E) TRAFFIC & LIGHTING No.Signs TR-1 Street Light System ( # of Poles)TR-2 Traffic Signal TR-3 Traffic Signal Modification TR-4 SUBTOTAL TRAFFIC & LIGHTING: (B)(C)(D)(E) WRITE-IN-ITEMS SUBTOTAL WRITE-IN ITEMS: STREET AND SITE IMPROVEMENTS SUBTOTAL:5,625.00 5,000.00 57,747.90 SALES TAX @ 10%562.50 500.00 5,774.79 STREET AND SITE IMPROVEMENTS TOTAL:6,187.50 5,500.00 63,522.69 (B)(C)(D)(E) Page 6 of 14 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 5/26/2020 CED Permit #:######## Existing Future Public PrivateRight-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost DRAINAGE (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* (CBs include frame and lid) Beehive D-2 90.00$ Each Through-curb Inlet Framework D-3 400.00$ EachCB Type I D-4 1,500.00$ Each 8 12,000.00 CB Type IL D-5 1,750.00$ Each CB Type II, 48" diameter D-6 2,300.00$ Each 4 9,200.00 for additional depth over 4' D-7 480.00$ FT CB Type II, 54" diameter D-8 2,500.00$ Each for additional depth over 4'D-9 495.00$ FT CB Type II, 60" diameter D-10 2,800.00$ Each 2 5,600.00 for additional depth over 4'D-11 600.00$ FT CB Type II, 72" diameter D-12 6,000.00$ Each for additional depth over 4'D-13 850.00$ FT CB Type II, 96" diameter D-14 14,000.00$ Each for additional depth over 4'D-15 925.00$ FT Trash Rack, 12"D-16 350.00$ EachTrash Rack, 15"D-17 410.00$ Each Trash Rack, 18"D-18 480.00$ Each Trash Rack, 21"D-19 550.00$ EachCleanout, PVC, 4"D-20 150.00$ Each Cleanout, PVC, 6"D-21 170.00$ Each Cleanout, PVC, 8"D-22 200.00$ EachCulvert, PVC, 4" D-23 10.00$ LF Culvert, PVC, 6" D-24 13.00$ LF Culvert, PVC, 8" D-25 15.00$ LFCulvert, PVC, 12" D-26 23.00$ LF Culvert, PVC, 15" D-27 35.00$ LF Culvert, PVC, 18" D-28 41.00$ LFCulvert, PVC, 24"D-29 56.00$ LF Culvert, PVC, 30" D-30 78.00$ LF Culvert, PVC, 36" D-31 130.00$ LFCulvert, CMP, 8"D-32 19.00$ LF Culvert, CMP, 12"D-33 29.00$ LF SUBTOTAL THIS PAGE:26,800.00 (B)(C)(D)(E) Quantity Remaining (Bond Reduction) (B)(C) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Page 7 of 14 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 5/26/2020 CED Permit #:######## Existing Future Public PrivateRight-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost Quantity Remaining (Bond Reduction) (B)(C) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES DRAINAGE (Continued)Culvert, CMP, 15"D-34 35.00$ LFCulvert, CMP, 18"D-35 41.00$ LF Culvert, CMP, 24"D-36 56.00$ LF Culvert, CMP, 30"D-37 78.00$ LFCulvert, CMP, 36"D-38 130.00$ LF Culvert, CMP, 48"D-39 190.00$ LFCulvert, CMP, 60"D-40 270.00$ LF Culvert, CMP, 72"D-41 350.00$ LF Culvert, Concrete, 8"D-42 42.00$ LFCulvert, Concrete, 12"D-43 48.00$ LF Culvert, Concrete, 15"D-44 78.00$ LF Culvert, Concrete, 18"D-45 48.00$ LFCulvert, Concrete, 24"D-46 78.00$ LF Culvert, Concrete, 30"D-47 125.00$ LF Culvert, Concrete, 36"D-48 150.00$ LFCulvert, Concrete, 42"D-49 175.00$ LF Culvert, Concrete, 48"D-50 205.00$ LF Culvert, CPE Triple Wall, 6" D-51 14.00$ LFCulvert, CPE Triple Wall, 8" D-52 16.00$ LF Culvert, CPE Triple Wall, 12" D-53 24.00$ LF Culvert, CPE Triple Wall, 15" D-54 35.00$ LF Culvert, CPE Triple Wall, 18" D-55 41.00$ LFCulvert, CPE Triple Wall, 24" D-56 56.00$ LF Culvert, CPE Triple Wall, 30" D-57 78.00$ LF Culvert, CPE Triple Wall, 36" D-58 130.00$ LF Culvert, LCPE, 6"D-59 60.00$ LF Culvert, LCPE, 8"D-60 72.00$ LF 85 6,120.00 505 36,360.00 Culvert, LCPE, 12"D-61 84.00$ LFCulvert, LCPE, 15"D-62 96.00$ LF Culvert, LCPE, 18"D-63 108.00$ LF Culvert, LCPE, 24"D-64 120.00$ LFCulvert, LCPE, 30"D-65 132.00$ LF Culvert, LCPE, 36"D-66 144.00$ LF Culvert, LCPE, 48"D-67 156.00$ LFCulvert, LCPE, 54"D-68 168.00$ LF SUBTOTAL THIS PAGE:6,120.00 36,360.00 (B)(C)(D)(E) Page 8 of 14 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 5/26/2020 CED Permit #:######## Existing Future Public PrivateRight-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost Quantity Remaining (Bond Reduction) (B)(C) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES DRAINAGE (Continued)Culvert, LCPE, 60"D-69 180.00$ LFCulvert, LCPE, 72"D-70 192.00$ LF Culvert, HDPE, 6"D-71 42.00$ LF Culvert, HDPE, 8"D-72 42.00$ LFCulvert, HDPE, 12"D-73 74.00$ LF Culvert, HDPE, 15"D-74 106.00$ LF Culvert, HDPE, 18"D-75 138.00$ LF Culvert, HDPE, 24"D-76 221.00$ LF Culvert, HDPE, 30"D-77 276.00$ LF Culvert, HDPE, 36"D-78 331.00$ LF 147 48,657.00 Culvert, HDPE, 48"D-79 386.00$ LF Culvert, HDPE, 54"D-80 441.00$ LF Culvert, HDPE, 60"D-81 496.00$ LF Culvert, HDPE, 72"D-82 551.00$ LFPipe, Polypropylene, 6"D-83 84.00$ LF Pipe, Polypropylene, 8"D-84 89.00$ LF Pipe, Polypropylene, 12"D-85 95.00$ LFPipe, Polypropylene, 15"D-86 100.00$ LF Pipe, Polypropylene, 18"D-87 106.00$ LF Pipe, Polypropylene, 24"D-88 111.00$ LFPipe, Polypropylene, 30"D-89 119.00$ LF Pipe, Polypropylene, 36"D-90 154.00$ LF Pipe, Polypropylene, 48"D-91 226.00$ LFPipe, Polypropylene, 54"D-92 332.00$ LF Pipe, Polypropylene, 60"D-93 439.00$ LF Pipe, Polypropylene, 72"D-94 545.00$ LFCulvert, DI, 6"D-95 61.00$ LF Culvert, DI, 8"D-96 84.00$ LF Culvert, DI, 12"D-97 106.00$ LFCulvert, DI, 15"D-98 129.00$ LF Culvert, DI, 18"D-99 152.00$ LF Culvert, DI, 24"D-100 175.00$ LF Culvert, DI, 30"D-101 198.00$ LF Culvert, DI, 36"D-102 220.00$ LF Culvert, DI, 48"D-103 243.00$ LF Culvert, DI, 54"D-104 266.00$ LF Culvert, DI, 60"D-105 289.00$ LF Culvert, DI, 72"D-106 311.00$ LF SUBTOTAL THIS PAGE:48,657.00 (B)(C)(D)(E) Page 9 of 14 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 5/26/2020 CED Permit #:######## Existing Future Public PrivateRight-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost Quantity Remaining (Bond Reduction) (B)(C) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Specialty 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$ LF Geotextile, laid in trench, polypropylene SD-5 3.00$ SYMid-tank Access Riser, 48" dia, 6' deep SD-6 2,000.00$ Each Pond Overflow Spillway SD-7 16.00$ SY Restrictor/Oil Separator, 12"SD-8 1,150.00$ Each Restrictor/Oil Separator, 15"SD-9 1,350.00$ Each Restrictor/Oil Separator, 18"SD-10 1,700.00$ Each Riprap, placed SD-11 42.00$ CY Tank End Reducer (36" diameter)SD-12 1,200.00$ Each Infiltration pond testing SD-13 125.00$ HR Permeable Pavement SD-14 Permeable Concrete Sidewalk SD-15 Culvert, Box __ ft x __ ft SD-16 SUBTOTAL SPECIALTY DRAINAGE ITEMS: (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 Each Infiltration 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 Each Sand Filter SF-12 Each Sand Filter Vault SF-13 Each Linear Sand Filter SF-14 Each Proprietary Facility SF-15 25,000.00$ Each 1 25,000.00 Bioretention Facility SF-16 Each SUBTOTAL STORMWATER FACILITIES:25,000.00 (B)(C)(D)(E) Page 10 of 14 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 5/26/2020 CED Permit #:######## Existing Future Public PrivateRight-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost Quantity Remaining (Bond Reduction) (B)(C) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES WRITE-IN-ITEMS (INCLUDE ON-SITE BMPs)WI-1 WI-2 WI-3WI-4 WI-5 WI-6 WI-7 WI-8 WI-9 WI-10 WI-11 WI-12WI-13 WI-14 WI-15 SUBTOTAL WRITE-IN ITEMS: DRAINAGE AND STORMWATER FACILITIES SUBTOTAL:6,120.00 136,817.00 SALES TAX @ 10%612.00 13,681.70 DRAINAGE AND STORMWATER FACILITIES TOTAL:6,732.00 150,498.70 (B) (C) (D) (E) Page 11 of 14 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 5/26/2020 CED Permit #:######## Existing Future Public Private Right-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost Connection to Existing Watermain W-1 2,000.00$ Each 2 4,000.00 Ductile Iron Watermain, CL 52, 4 Inch Diameter W-2 50.00$ LFDuctile Iron Watermain, CL 52, 6 Inch Diameter W-3 56.00$ LF Ductile Iron Watermain, CL 52, 8 Inch Diameter W-4 60.00$ LF Ductile Iron Watermain, CL 52, 10 Inch Diameter W-5 70.00$ LF 360 25,200.00 Ductile Iron Watermain, CL 52, 12 Inch Diameter W-6 80.00$ LF Gate Valve, 4 inch Diameter W-7 500.00$ Each 1 500.00 Gate Valve, 6 inch Diameter W-8 700.00$ Each 1 700.00 Gate Valve, 8 Inch Diameter W-9 800.00$ Each Gate Valve, 10 Inch Diameter W-10 1,000.00$ Each Gate Valve, 12 Inch Diameter W-11 1,200.00$ Each 4 4,800.00 Fire Hydrant Assembly W-12 4,000.00$ Each 1 4,000.00Permanent Blow-Off Assembly W-13 1,800.00$ Each Air-Vac Assembly, 2-Inch Diameter W-14 2,000.00$ Each Air-Vac Assembly, 1-Inch Diameter W-15 1,500.00$ EachCompound Meter Assembly 3-inch Diameter W-16 8,000.00$ Each Compound Meter Assembly 4-inch Diameter W-17 9,000.00$ Each Compound Meter Assembly 6-inch Diameter W-18 10,000.00$ EachPressure Reducing Valve Station 8-inch to 10-inch W-19 20,000.00$ Each WATER SUBTOTAL:12,800.00 26,400.00 SALES TAX @ 10%1,280.00 2,640.00 WATER TOTAL:14,080.00 29,040.00 (B) (C) (D) (E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR WATER Quantity Remaining (Bond Reduction) (B)(C) Page 12 of 14 Ref 8-H Bond Quantity Worksheet SECTION II.d WATER Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 5/26/2020 CED Permit #:######## Existing Future Public PrivateRight-of-Way Improvements Improvements (D) (E)Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost Clean Outs SS-1 1,000.00$ Each 5 5,000.00 Grease Interceptor, 500 gallon SS-2 8,000.00$ Each Grease Interceptor, 1000 gallon SS-3 10,000.00$ Each Grease Interceptor, 1500 gallon SS-4 15,000.00$ Each Side Sewer Pipe, PVC. 4 Inch Diameter SS-5 80.00$ LF Side Sewer Pipe, PVC. 6 Inch Diameter SS-6 95.00$ LF 80 7,600.00 Sewer Pipe, PVC, 8 inch Diameter SS-7 105.00$ LF Sewer Pipe, PVC, 12 Inch Diameter SS-8 120.00$ LF Sewer Pipe, DI, 8 inch Diameter SS-9 115.00$ LFSewer Pipe, DI, 12 Inch Diameter SS-10 130.00$ LF Manhole, 48 Inch Diameter SS-11 6,000.00$ Each Manhole, 54 Inch Diameter SS-13 6,500.00$ EachManhole, 60 Inch Diameter SS-15 7,500.00$ Each Manhole, 72 Inch Diameter SS-17 8,500.00$ Each Manhole, 96 Inch Diameter SS-19 14,000.00$ EachPipe, C-900, 12 Inch Diameter SS-21 180.00$ LF Outside Drop SS-24 1,500.00$ LS Inside Drop SS-25 1,000.00$ LSSewer Pipe, PVC, ____ Inch Diameter SS-26Lift Station (Entire System)SS-27 LS SANITARY SEWER SUBTOTAL:7,600.00 5,000.00 SALES TAX @ 10%760.00 500.00 SANITARY SEWER TOTAL:8,360.00 5,500.00 (B) (C) (D) (E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR SANITARY SEWER Quantity Remaining (Bond Reduction) (B)(C) Page 13 of 14 Ref 8-H Bond Quantity Worksheet SECTION II.e SANITARY SEWER Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 5/26/2020 Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430-7200 Date: 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) Existing Right-of-Way Improvements Subtotal (b) (b)28,627.50$ Future Public Improvements Subtotal (c)34,540.00$ Stormwater & Drainage Facilities (Public & Private) Subtotal (d) (d)157,230.70$ (e) (f) Site Restoration Civil Construction Permit Maintenance Bond 44,079.64$ Bond Reduction 2 Construction Permit Bond Amount 3 Minimum Bond Amount is $10,000.00 1 Estimate Only - May involve multiple and variable components, which will be established on an individual basis by Development Engineering. 2 The City of Renton allows one request only for bond reduction prior to the maintenance period. Reduction of not more than 70% of the original bond amount, provided that the remaining 30% will cover all remaining items to be constructed. 3 Required Bond Amounts are subject to review and modification by Development Engineering. * Note: The word BOND as used in this document means any financial guarantee acceptable to the City of Renton.** Note: All prices include labor, equipment, materials, overhead and profit. EST1 ((b) + (c) + (d)) x 20% -$ MAINTENANCE BOND */** (after final acceptance of construction) 3,024.45$ 28,627.50$ 200,171.95$ 3,024.45$ -$ 157,230.70$ -$ 203,196.40$ P (a) x 100% SITE IMPROVEMENT BOND QUANTITY WORKSHEET BOND CALCULATIONS 5/25/2020 Peter Apostol, PE 35163 Coterra Engineering R ((b x 150%) + (d x 100%)) S (e) x 150% + (f) x 100% Bond Reduction: Existing Right-of-Way Improvements (Quantity Remaining)2 Bond Reduction: Stormwater & Drainage Facilities (Quantity Remaining)2 T (P +R - S) Prepared by: Project Information CONSTRUCTION BOND AMOUNT */** (prior to permit issuance) (206) 596-7115 peter@coterraengineering.com Sunset Oaks Apartments ##-###### 1062 Glenwood Ave NE 7227801315; 7227801290; 7227801310 FOR APPROVAL ######## 321 3rd Ave South, #406, Seattle, WA 98104 Page 14 of 14 Ref 8-H Bond Quantity Worksheet SECTION III. BOND WORKSHEET Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 5/26/2020 Appendix G Declarations of Covenants Page 1 of ___ Return Address: City Clerk’s Office City of Renton 1055 S Grady Way Renton, WA 98057 DECLARATION OF COVENANT FOR INSPECTION AND MAINTENANCE OF DRAINAGE FACILITIES AND ON-SITE BMPS Grantor: Grantee: City of Renton, a Washington municipal corporation Legal Description: Assessor's Tax Parcel ID#: IN CONSIDERATION of the approved City of Renton (check one of the following) Residential Building Permit Commercial Building Permit Clearing and Grading Permit Civil Construction or Utility Permit for Permit(s)_____________________ (Construction/Building/Utility Permit #) relating to the real property ("Property") described above, the Grantor(s), the owner(s) in fee of that Property, hereby covenants (covenant) with the City of Renton (“City of Renton” or “City”), a municipal corporation of the state of Washington, that he/she (they) will observe, consent to, and abide by the conditions and obligations set forth and described in Paragraphs 1 through 9 below with regard to the Property, and hereby grants (grant) an easement as described in Paragraphs 2 and 3. Grantor(s) hereby grants (grant), covenants (covenant), and agrees (agree) as follows: 1.The Grantor(s) or his/her (their) successors in interest and assigns ("Owners ") shall at their own cost, operate, maintain, and keep in good repair, the Property's drainage facilities constructed as required in the approved construction plans and specifications __________________ (Project Plan #) on file with the City of Renton and submitted to the City of Renton for the review and approval of permit(s) _____________________________ (Construction/Building/Utility Permit #). The Property's drainage facilities are shown and/or listed on Exhibit A – Site Plan. The Property’s drainage facilities shall be maintained in compliance with the operation and maintenance schedule included and attached herein as Exhibit B – Operations and Maintenance. Drainage facilities include pipes, channels, flow control facilities, water quality facilities, on-site best management practices (BMPs) and other engineered structures designed to manage and/or Page 2 of ___ treat stormwater on the Property. On-site BMPs include dispersion and infiltration devices, bioretention, permeable pavements, rainwater harvesting systems, tree retention credit, reduced impervious surface footprint, vegetated roofs and other measures designed to mimic pre-developed hydrology and minimize stormwater runoff on the Property. 2.City of Renton shall have the right to ingress and egress over those portions of the Property necessary to perform inspections of the stormwater facilities and BMPs and conduct maintenance activities specified in this Declaration of Covenant and in accordance with the Renton Municipal Code. City of Renton shall provide at least thirty (30) days’ written notice to the Owners that entry on the Property is planned for the inspection of drainage facilities. After the thirty (30) days, the Owners shall allow the City of Renton to enter for the sole purpose of inspecting drainage facilities. In lieu of inspection by the City, the Owners may elect to engage a licensed civil engineer registered in the state of Washington who has expertise in drainage to inspect the drainage facilities and provide a written report describing their condition. If the engineer option is chosen, the Owners shall provide written notice to the City of Renton within fifteen (15) days of receiving the City’s notice of inspection. Within thirty (30) days of giving this notice, the Owners, or engineer on behalf of the Owners, shall provide the engineer’s report to the City of Renton. If the report is not provided in a timely manner as specified above, the City of Renton may inspect the drainage facilities without further notice. 3.If City of Renton determines from its inspection, or from an engineer’s report provided in accordance with Paragraph 2, that maintenance, repair, restoration, and/or mitigation work is required to be done to any of the drainage facilities, City of Renton shall notify the Owners of the specific maintenance, repair, restoration, and/or mitigation work (“Work”) required pursuant to the Renton Municipal Code. The City shall also set a reasonable deadline for the Owners to complete the Work, or to provide an engineer’s report that verifies completion of the Work. After the deadline has passed, the Owners shall allow the City access to re-inspect the drainage facilities unless an engineer’s report has been provided verifying completion of the Work. If the Work is not completed within the time frame set by the City, the City may initiate an enforcement action and/or perform the Work and hereby is given access to the Property for such purposes. Written notice will be sent to the Owners stating the City’s intention to perform such Work. This Work will not commence until at least seven (7) days after such notice is mailed. If, within the sole discretion of the City, there exists an imminent or present danger, the seven (7) day notice period will be waived and Work will begin immediately. 4.The Owners shall assume all responsibility for the cost of any Work, or any measures taken by the City to address conditions as described in Paragraph 3. Such responsibility shall include reimbursement to the City within thirty (30) days of the receipt of the invoice for any such Work performed. Overdue payments will require payment of interest at the maximum legal rate allowed by RCW 19.52.020 (currently twelve percent (12%)). If the City initiates legal action to enforce this agreement, the prevailing party in such action is entitled to recover reasonable litigation costs and attorney’s fees. 5.The Owners are required to obtain written approval from City of Renton prior to filling, piping, cutting, or removing vegetation (except in routine landscape maintenance) in open vegetated stormwater facilities (such as swales, channels, ditches, ponds, etc.), or performing any alterations or modifications to the drainage facilities referenced in this Declaration of Covenant. Page 3 of ___ 6.Any notice or consent required to be given or otherwise provided for by the provisions of this Agreement shall be effective upon personal delivery, or three (3) days after mailing by Certified Mail, return receipt requested. 7.With regard to the matters addressed herein, this agreement constitutes the entire agreement between the parties, and supersedes all prior discussions, negotiations, and all agreements whatsoever whether oral or written. 8.This Declaration of Covenant is intended to protect the value and desirability and promote efficient and effective management of surface water drainage of the real property described above, and shall inure to the benefit of all the citizens of the City of Renton and its successors and assigns. This Declaration of Covenant shall run with the land and be binding upon Grantor(s), and Grantor's(s') successors in interest, and assigns. 9.This Declaration of Covenant may be terminated by execution of a written agreement by the Owners and the City that is recorded by King County in its real property records. IN WITNESS WHEREOF, this Declaration of Covenant for the Inspection and Maintenance of Drainage Facilities is executed this _____ day of ____________________, 20_____. GRANTOR, owner of the Property GRANTOR, owner of the Property STATE OF WASHINGTON ) COUNTY OF KING )ss. On this day personally appeared before me: , to me known to be the individual(s) described in and who executed the within and foregoing instrument and acknowledged that they signed the same as their free and voluntary act and deed, for the uses and purposes therein stated. Given under my hand and official seal this _____ day of ___________________, 20_____. Printed name Notary Public in and for the State of Washington, residing at My appointment expires coterra ENGINEERING PLLC MAINTENANCE INSTRUCTIONS FOR A BIORETENTION CELL Your property contains an on-site BMP (best management practice) called “bioretention,” which was installed to mitigate the stormwater quantity and quality impacts on both the impervious (paved or roof) and pervious surfaces (lawn or landscape) on your property. Bioretention cells, like rain gardens, are vegetated closed depressions or ponds that retain and filter stormwater from an area of impervious surface or nonnative pervious surface. Bioretention cells rely on effective infiltration performance more so than rain gardens. The soil in the bioretention cell has been enhanced to encourage and support vigorous plant growth that serves to filter the water and sustain a minimum infiltration capacity. Depending on soil conditions, bioretention cells may have water in them throughout the wet season and may overflow during major storm events. However, standing water can also be an indicator that periodic maintenance is required to sustain infiltrative performance. This on-site BMP shall be maintained per Appendix A of the City of Renton’s Surface Water Design Manual. MAINTENANCE RESTRICTIONS The size, placement, and design of the rain garden as depicted by the site plan and design details must be maintained and may not be changed without written approval from the City of Renton or through a future development permit from the City of Renton. Chemical fertilizers and pesticides must not be used. INSPECTION FREQUENCY AND MAINTENANCE GUIDELINES • Bioretention cells must be inspected annually for physical defects and sediment accumulation. • Bioretention cells have inflow and overflow inlets and outlets. These need to be maintained to ensure that water is moving into and out of the bioretention area. Check inlets/outlets for debris/sediment blockage, bare spots (exposed soil), or other signs of erosion damage (soil movement). Remove debris and obstructions as necessary. • After major storm events, the bioretention cell should be checked to see that the overflow system is working properly and sedimentation is not occurring at the inlet. If erosion damage or bare spots are evident, they should be stabilized with soil, plant material, mulch, or landscape rock. Sediment deposits should be carefully removed and the sediment source eliminated. • Plants must be adapted to wet winter conditions and dry summer conditions. Vegetation is to be watered and pruned as needed. • Frequent watering is required to keep the plants healthy: o Year 1: weekly, o Year 2: bimonthly, o Year 3: bimonthly, o Year 4 and beyond: as needed for established plantings and dry periods. • Chemical fertilizers and pesticides must not be used. • Bioretention soil must be replaced in areas where sediment accumulation is preventing adequate infiltration of water through the soil. • Compacted soil should be decompacted. • Trash and debris must be removed often from the bioretention depression. • Mulch must be applied to bare soil at a minimum of 2 inches to maintain healthy growth. • Compost may be added if soil nutrients are no longer adequate to support plant growth. • Plant materials may be changed to suit tastes. • Vegetation should be maintained as follows: 1) Replace all dead vegetation as soon as possible; 2) Remove fallen leaves and debris as needed; 3) Remove all noxious vegetation when discovered; 4) Manually weed without herbicides or pesticides; 5) To protect infiltration performance, do not compact soils in the bioretention cell with heavy maintenance equipment and/or excessive foot traffic; 6) During drought conditions, use mulch to prevent excess solar damage and water loss. RECORDING REQUIREMENT These bioretention on-site BMP maintenance and operation instructions must be recorded as an attachment to the required declaration of covenant and grant of easement per Requirement 3 of Section C.1.3.4 of the City of Renton Surface Water Design Manual. The intent of these instructions is to explain to future property owners, the purpose of the BMP and how it must be maintained and operated. These instructions are intended to be a minimum; the City of Renton may require additional instructions based on site-specific conditions. See the City of Renton’s Surface Water Design Manual website for additional information and updates. MAINTENANCE INSTRUCTIONS FOR PERMEABLE PAVEMENT (NON-VEGETATED) Your property contains an on-site BMP (best management practice) called “permeable pavement,” which was installed to minimize the stormwater quantity and quality impacts of some or all of the paved surfaces on your property. Permeable pavements reduce the amount of rainfall that becomes runoff by allowing water to seep through the pavement into a free-draining gravel or sand bed, where it can be infiltrated into the ground. This on-site BMP shall be maintained per Appendix A of the City of Renton’s Surface Water Design Manual. Permeable Pavements The type(s) of permeable pavement used on your property is (CHECK THE BOX(ES) THAT APPLY): Porous concrete Porous asphalt Permeable pavers Modular grid pavement MAINTENANCE RESTRICTIONS The area covered by permeable pavement as depicted by the site plan and design details must be maintained as permeable pavement and may not be changed without written approval from the City of Renton or through a future development permit from the City of Renton. INSPECTION FREQUENCY AND MAINTENANCE GUIDELINES • Permeable pavements must be inspected after one major storm each year to make sure it is working properly. More frequent inspection is recommended. • Prolonged ponding or standing water on the pavement surface is a sign that the system is defective and may need to be replaced. If this occurs, contact the pavement installer or the City of Renton for further instructions. • A typical permeable pavement system has a life expectancy of approximately 25 years. To help extend the useful life of the system, the surface of the permeable pavement should be kept clean, stable and free of leaves, debris, and sediment through regular sweeping or vacuum sweeping. Aggregate fill in modular grid pavement may need periodic surface replenishment. • The owner is responsible for the repair of all ruts, deformation, and/or broken paving grids or pavers. • Modular grid pavement and permeable pavers filled with gravel or with gravel in the joints may need to be refilled periodically. RECORDING REQUIREMENT These permeable pavement on-site BMP maintenance and operation instructions must be recorded as an attachment to the required declaration of covenant and grant of easement per Requirement 3 of Section C.1.3.4 of the City of Renton Surface Water Design Manual. The intent of these instructions is to explain to future property owners, the purpose of the BMP and how it must be maintained and operated. These instructions are intended to be a minimum; the City of Renton may require additional instructions based on site-specific conditions. See the City of Renton’s Surface Water Design Manual website for additional information and updates. EXHIBIT C LEGAL DESCRIPTION OF SUNSET OAKS PROPERTY PARCEL 5 OF CITY OF RENTON LOT LINE ADJUSTMENT NO. LUA16-000132, RECORDED UNDER RECORDING NO. 20160603900008, IN KING COUNTY, WASHINGTON; AND LOTS 6 AND 11, BLOCK 41, CORRECTED PLAT OF RENTON HIGHLANDS NO. 2, ACCORDING TO THE PLAT THEREOF RECORDED IN VOLUME 57 OF PLATS, PAGES 92 THROUGH 96, INCLUSIVE, IN KING COUNTY, WASHINGTON. SITUATE IN THE COUNTY OF KING, STATE OF WASHINGTON. Appendix H Operations and Maintenance Manual APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-6 NO. 3 – DETENTION TANKS AND VAULTS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site 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 City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City 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. Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Tank or Vault Storage Area Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non-floatables). No trash or debris in vault. 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. Tank Structure 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. 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. Inlet/Outlet Pipes 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. Damaged inlet/outlet pipes 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. Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance. Manhole access covered. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-7 NO. 3 – DETENTION TANKS AND VAULTS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Access Manhole (cont.) 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. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. Large access doors/plate 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; 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-8 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Structure Trash and debris 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. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Sediment accumulation 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. Damage to frame and/or top slab 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. 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 in walls or bottom 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 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. 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. FROP-T Section Damaged FROP-T 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-9 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED FROP-T Section (cont.) Damaged FROP-T (cont.) 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. Any holes—other than designed holes—in the structure. Structure has no holes other than designed holes. Cleanout Gate Damaged or missing cleanout gate Cleanout gate is missing. Replace cleanout gate. 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. Orifice Plate Damaged or missing orifice plate Control device is not working properly due to missing, out of place, or bent orifice plate. Plate is in place and works as designed. Obstructions to orifice plate Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Overflow Pipe Obstructions to overflow pipe Any trash or debris blocking (or having the potential of blocking) the overflow pipe. Pipe is free of all obstructions and works as designed. Deformed or damaged lip of overflow pipe Lip of overflow pipe is bent or deformed. Overflow pipe does not allow overflow at an elevation lower than design Inlet/Outlet Pipe 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. Damaged inlet/outlet pipe 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. Metal Grates (If applicable) 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 Damaged or missing grate Grate missing or broken member(s) of the grate. Grate is in place and meets design standards. Manhole Cover/Lid 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. 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 STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-10 NO. 5 – CATCH BASINS AND MANHOLES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Structure Sediment accumulation 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 and debris 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. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Damage to frame and/or top slab 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. 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 in walls or bottom 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 is structurally sound. 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. 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. Inlet/Outlet Pipe 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-11 NO. 5 – CATCH BASINS AND MANHOLES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Inlet/Outlet Pipe (cont.) Damaged inlet/outlet pipe 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. Metal Grates (Catch Basins) 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 Damaged or missing grate Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance. Grate is in place and meets design standards. Manhole Cover/Lid 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. 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 STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-12 NO. 6 – CONVEYANCE PIPES AND DITCHES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Pipes Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes. Vegetation/root growth in pipe 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. Damaged pipes 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. Ditches 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 City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City 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. Excessive vegetation growth 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. 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 STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-41 NO. 30 – PERMEABLE PAVEMENT BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Preventive Surface cleaning/ vegetation control Media surface vacuumed or pressure washed annually, vegetation controlled to design maximum. Weed growth suggesting sediment accumulation. No dirt, sediment, or debris clogging porous media, or vegetation limiting infiltration. Porous Concrete, Porous Asphaltic Concrete, and Permeable Pavers Trash and debris Trash and debris on the pavement interfering with infiltration; leaf drop in fall season. No trash or debris interfering with infiltration. Sediment accumulation Sediment accumulation on the pavement interfering with infiltration; runoff from adjacent areas depositing sediment/debris on pavement. Pavement infiltrates as designed; adjacent areas stabilized. Insufficient infiltration rate Pavement does not infiltrate at a rate of 10 inches per hour. Pavement infiltrates at a rate greater than 10 inches per hour. Excessive ponding Standing water for a long period of time on the surface of the pavement. Standing water infiltrates at the desired rate. Broken or cracked pavement Pavement is broken or cracked. No broken pavement or cracks on the surface of the pavement. Settlement Uneven pavement surface indicating settlement of the subsurface layer. Pavement surface is uniformly level. Moss growth Moss growing on pavement interfering with infiltration. No moss interferes with infiltration. Inflow restricted Inflow to the pavement is diverted, restricted, or depositing sediment and debris on the pavement. Inflow to pavement is unobstructed and not bringing sediment or debris to the pavement. Underdrain not freely flowing Underdrain is not flowing when pavement has been infiltrating water. Underdrain flows freely when water is present. Overflow not controlling excess water Overflow not controlling excess water to desired location; native soil is exposed or other signs of erosion damage are present. Overflow permits excess water to leave the site at the desired location; Overflow is stabilized and appropriately armored. Permeable Pavers Broken or missing pavers Broken or missing paving blocks on surface of pavement. No missing or broken paving blocks interfering with infiltration. Uneven surface Uneven surface due to settlement or scour of fill in the interstices of the paving blocks. Pavement surface is uniformly level. Compaction Poor infiltration due to soil compaction between paving blocks. No soil compaction in the interstices of the paver blocks limiting infiltration. Poor vegetation growth (if applicable) Grass in the interstices of the paving blocks is dead. Healthy grass is growing in the interstices of the paver blocks. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-42 NO. 31 – BIORETENTION BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Preventive Vegetation Vegetation to be watered and pruned as needed and mulch applied to a minimum of 2 inches to maintain healthy growth. Healthy vegetation growth with full coverage as designed. Bioretention Area Trash and debris Trash and debris in the bioretention area; leaf drop in the fall season. No trash or debris In the bioretention area. Sediment accumulation Sediment accumulation in the bioretention area interfering with infiltration. Water in the bioretention infiltrates as designed. Excessive ponding Standing water in the bioretention area for more than two days. Standing water infiltrates at the desired rate. Inflow restricted Inflow not getting into bioretention; debris/sediment blockage at inlet features; native soil is exposed or other signs of erosion damage is present. Unobstructed and properly routed inflow into bioretention area; inlet is stabilized and appropriately armored. Overflow not controlling excess water Overflow water not controlled by outlet features; native soil is exposed or other signs of erosion damage is present. Outlet features control overflow; overflow is stabilized and appropriately armored. Underdrain not freely flowing Underdrain is not flowing when bioretention area has been infiltrating water. Underdrain flows freely when water is present. Vegetation Poor vegetation coverage Plants not thriving across at least 80% of the entire design vegetated area within the BMP; overly dense vegetation requiring pruning. Healthy water tolerant plants in bioretention area, plants thriving across at least 80% of the entire design vegetated area within the facility. Insufficient vegetation Plants not water tolerant species. Plants are water tolerant. Weeds present Weeds growing in bioretention area. No weeds in bioretention area. Watering not occurring Planting schedule requires frequent watering (approx. weekly Year 1, bimonthly Years 2 and 3) for new facilities, and as needed for established plantings or dry periods Plants are established and thriving Pest control Signs of pests, such as wilting or chewed leaves or bark, spotting or other indicators; extended ponding period encouraging mosquitoes Plant community is pest-free when following an approved Integrated Pest Management plan; bioretention functioning normally and ponding controlled as needed for pest control Containment Berm and Earthen Slopes Erosion Erosion occurring at earthen slopes or containment berm side slope. Erosion on the containment berm and side slopes has been repaired and the cause of the erosion corrected. Voids created by nuisance animals (e.g., rodents) or tree roots Voids affecting berm integrity or creating leaky pond condition Voids have been repaired; facility is free of nuisance animals following an approved Integrated Pest Management plan. Settlement Any part of the containment berm top has less than 6 inches of freeboard from the maximum pond level to the top of the berm. A minimum of 6 inches freeboard from the maximum pond level to the top of the berm. Amended Soil Poor soil nutrients Soil not providing plant nutrients. Soil providing plant nutrients. Bare spots Bare spots on soil in bioretention area. No bare spots, bioretention area covered with vegetation or mulch mixed into the underlying soil. Compaction Poor infiltration due to soil compaction in the bioretention area. No soil compaction in the bioretention area. Bioltration SUBMITTAL PACKAGE Oldcastle Infrastructure (800) 579-8819 OldcastleStormwater.com BIOPOD™ TABLE OF CONTENTS 1 - FEATURES & BENEFITS 2 - WA ECOLOGY GULD APPROVAL 3 - INSPECTION & MAINTENANCE SECTION 1 FEATURES & BENEFITS STORMWATER BIOPOD™ SYSTEM WITH STORMMIX™ MEDIA Sustainable Green Infrastructure for Stormwater Management BioPod systems utilize an advanced biofiltration design for filtration, sorption and biological uptake to remove Total Suspended Solids (TSS), dissolved metals, nutrients, gross solids, trash and debris as well as petroleum hydrocarbons from stormwater runoff. Environmentally friendly and aesthetically pleasing, BioPod systems are a proven, Low-Impact Development (LID) solution for stormwater treatment. BioPod systems integrate seamlessly into standard site drainage and can accommodate a wide variety of vegetation to meet green infrastructure requirements. Stormwater Treatment,NATURALLY STANDARD SIZES BioPod units are available in many standard and custom sizes to meet most site-specific requirements. Contact your local Oldcastle Infrastructure representative for additional sizes. 4’ x 4’ 4’ x 6’ 4’ x 8’ 4’ x 10’ 6’ x 6’ 6’ x 8’ 6’ x 12’ 8’ x 16’ BIORETENTION / BIOFILTRATION BioPod systems use StormMix media, an engineered high-flow rate media (153 in/hr) to remove stormwater pollutants. The BioPod system has received a General Use Level Designation (GULD) approval from the Washington State Department of Ecology for Basic (TSS), Phosphorus, and Enhanced (dissolved metals) treatment. Offering flexibility of design and construction for your storm drain system, the BioPod system comes as an all-in-one, single-piece unit composed of durable precast concrete for ease of installation and a long service life. The BioPod system is offered in four configurations: High-Flow Bypass BioPod system offers an optional internal high-flow bypass that eliminates the need for a separate bypass structure, reducing costs and simplifying design so unit can be placed in a “sag” condition. Hydromodification BioPod system can be used in conjunction with other Oldcastle detention systems to address hydromodification and water treatment requirements. Collected flows may be utilized to supplement irrigation of the unit or surrounding vegetated areas by integrating a harvesting system, reducing consumption of local potable water. LEED WITH BIOPOD Can assist in earning LEED credits for: • Sustainable Sites (6.1, 6.2) • Water Efficiency (1.1, 1.2, 3.1, 3.2) • Materials & Resources (4.1, 4.2; 5.1, 5.2 in AZ, CA, NV, UT) BIOPOD SURFACE At-grade vault with media only, no vegetation. BIOPOD TREE Vault with media and tree(s). BIOPOD PLANTER Vault with media and vegetation. BIOPOD UNDERGROUND Below-grade vault with media only, no vegetation. Stormwater Treatment,NATURALLY (800) 579-8819 oldcastlestormwater.com BIOPOD™ SYSTEM WITH STORMMIX™ MEDIA SECTION 2 WA ECOLOGY GULD APPROVAL May 2019 GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS), DISSOLVED METALS (ENHANCED), AND PHOSPHORUS TREATMENT For Oldcastle Infrastructure, Inc.’s The BioPod™ Biofilter (Formerly the TreePod Biofilter) Ecology’s Decision: Based on Oldcastle Infrastructure, Inc. application submissions for the The BioPod™ Biofilter (BioPod), Ecology hereby issues the following use level designation: 1. General Use Level Designation (GULD) for Basic, Enhanced, and Phosphorus Treatment: Sized at a hydraulic loading rate of 1.6 gallons per minute (gpm) per square foot (sq ft) of media surface area. Constructed with a minimum media thickness of 18-inches (1.5-feet). 2. Ecology approves the BioPod at the hydraulic loading rate listed above, to achieve the maximum water quality design flow rate. The water quality design flow rates are calculated using the following procedures: Western Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using the latest version of the Western Washington Hydrology Model or other Ecology- approved continuous runoff model. Eastern Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using one of the three methods described in Chapter 2.2.5 of the Stormwater Management Manual for Eastern Washington (SWMMEW) or local manual. Entire State: For treatment installed downstream of detention, the water quality design flow rate is the full 2-year release rate of the detention facility. 3. The GULD has no expiration date, but may be amended or revoked by Ecology. Ecology’s Conditions of Use: The BioPod shall comply with these conditions: 1) Applicants shall design, assemble, install, operate, and maintain the BioPod installations in accordance with Oldcastle Infrastructure, Inc.’s applicable manuals and the Ecology Decision. 2) BioPod media shall conform to the specifications submitted to and approved by Ecology 3) Maintenance: The required inspection/maintenance interval for stormwater treatment devices is often dependent on the efficiency of the device and the degree of pollutant loading from a particular drainage basin. Therefore, Ecology does not endorse or recommend a “one size fits all” maintenance cycle for a particular model/size of manufactured filter treatment device. The BioPod is designed for a target maintenance interval of 1 year. Maintenance includes replacing the mulch, assessing plant health, removal of trash, and raking the top few inches of engineered media. A BioPod system tested at the Lake Union Ship Canal Test Facility in Seattle, WA required maintenance after 1.5 months, or 6.3% of a water year. Monitoring personnel observed similar maintenance issues with other systems evaluated at the Test Facility. The runoff from the Test Facility may be unusual and maintenance requirements of systems installed at the Test Facility may not be indicative of maintenance requirements for all sites. Test results provided to Ecology from a BioPod System evaluated in a lab following New Jersey Department of Environmental Protection Laboratory Protocol for Filtration MTDs have indicated the BioPod System is capable of longer maintenance intervals. Owners/operators must inspect BioPod systems for a minimum of twelve months from the start of post-construction operation to determine site-specific inspection/maintenance schedules and requirements. Owners/operators must conduct inspections monthly during the wet season, and every other month during the dry season. (According to the SWMMWW, the wet season in western Washington is October 1 to April 30. According to the SWMMEW, the wet season in eastern Washington is October 1 to June 30.) After the first year of operation, owners/operators must conduct inspections based on the findings during the first year of inspections. Conduct inspections by qualified personnel, follow manufacturer’s guidelines, and use methods capable of determining either a decrease in treated effluent flow rate and/or a decrease in pollutant removal ability. 4) Install the BioPod in such a manner that you bypass flows exceeding the maximum operating rate and you will not resuspend captured sediment. 5) Discharges from the BioPod shall not cause or contribute to water quality standards violations in receiving waters. Applicant: Oldcastle Infrastructure, Inc. Applicant’s Address: 7100 Longe St, Suite 100 Stockton, CA 95206 Application Documents: Technical Evaluation Report TreePod™ BioFilter System Performance Certification Project, Prepared for Oldcastle, Inc., Prepared by Herrera Environmental Consultants, Inc. February 2018 Technical Memorandum: Response to Board of External Reviewers’ Comments on the Technical Evaluation Report for the TreePod™ Biofilter System Performance Certification Project, Oldcastle, Inc. and Herrera Environmental Consultants, Inc., February 2018 Technical Memorandum: Response to Board of External Reviewers’ Comments on the Technical Evaluation Report for the TreePod™ Biofilter System Performance Certification Project, Oldcastle, Inc. and Herrera Environmental Consultants, Inc., January 2018 Application for Pilot Use Level Designation, TreePod™ Biofilter – Stormwater Treatment System, Oldcastle Stormwater Solutions, May 2016 Emerging Stormwater Treatment Technologies Application for Certification: The TreePod™ Biofilter, Oldcastle Stormwater Solutions, April 2016 Applicant’s Use Level Request: General Use Level Designation as a Basic, Enhanced, and Phosphorus Treatment device in accordance with Ecology’s Stormwater Management Manual for Western Washington Applicant’s Performance Claims: Based on results from laboratory and field-testing, the applicant claims the BioPod™ Biofilter operating at a hydraulic loading rate of 153 inches per hour is able to remove: 80% of Total Suspended Solids (TSS) for influent concentrations greater than 100 mg/L and achieve a 20 mg/L effluent for influent concentrations less than 100 mg/L. 60% dissolved zinc for influent concentrations 0.02 to 0.3 mg/L. 30% dissolved copper for influent concentrations 0.005 to 0.02 mg/L. 50% or greater total phosphorus for influent concentrations 0.1 to 0.5 mg/L. Ecology’s Recommendations: Ecology finds that: Oldcastle Infrastructure, Inc. has shown Ecology, through laboratory and field testing, that the BioPod™ Biofilter is capable of attaining Ecology’s Basic, Total Phosphorus, and Enhanced treatment goals. Findings of Fact: Field Testing 1. Herrera Environmental Consultants, Inc. conducted monitoring of the BioPod™ Biofilter at the Lake Union Ship Canal Test Facility in Seattle Washington between November 2016 and April 2018. Herrera collected flow-weight composite samples during 14 separate storm events and peak flow grab samples during 3 separate storm events. The system was sized at an infiltration rate of 153 inches per hour or a hydraulic loading rate of 1.6 gpm/ft2. 2. The D50 of the influent PSD ranged from 3 to 292 microns, with an average D50 of 28 microns. 3. Influent TSS concentrations ranged from 17 mg/L to 666 mg/L, with a mean concentration of 98 mg/L. For all samples (influent concentrations above and below 100 mg/L) the bootstrap estimate of the lower 95 percent confidence limit (LCL 95) of the mean TSS reduction was 84% and the bootstrap estimate of the upper 95 percent confidence limit (UCL95) of the mean TSS effluent concentration was 8.2 mg/L. 4. Dissolved copper influent concentrations from the 17 events ranged from 9.0 µg/L to 21.1 µg/L. The 21.1 µg/L data point was reduced to 20.0 µg/L, the upper limit to the TAPE allowed influent concentration range, prior to calculating the pollutant removal. A bootstrap estimate of the LCL95 of the mean dissolved copper reduction was 35%. 5. Dissolved zinc influent concentrations from the 17 events ranged from 26.1 µg/L to 43.3 µg/L. A bootstrap estimate of the LCL95 of the mean dissolved zinc reduction was 71%. 6. Total phosphorus influent concentrations from the 17 events ranged from 0.064 mg/L to 1.56 mg/L. All influent data greater than 0.5 mg/L were reduced to 0.5 mg/L, the upper limit to the TAPE allowed influent concentration range, prior to calculating the pollutant removal. A bootstrap estimate of the LCL95 of the mean total phosphorus reduction was 64%. 7. The system experienced rapid sediment loading and needed to be maintained after 1.5 months. Monitoring personnel observed similar sediment loading issues with other systems evaluated at the Test Facility. The runoff from the Test Facility may not be indicative of maintenance requirements for all sites. Laboratory Testing 1. Good Harbour Laboratories (GHL) conducted laboratory testing at their site in Mississauga, Ontario in October 2017 following the New Jersey Department of Environmental Protection Laboratory Protocol for Filtration MTDs. The testing evaluated a 4-foot by 6-foot standard biofiltration chamber and inlet contour rack with bypass weir. The test sediment used during the testing was custom blended by GHL using various commercially available silica sands, which had an average d50 of 69 µm. Based on the lab test results: a. GHL evaluated removal efficiency over 15 events at a Maximum Treatment Flow Rate (MTFR) of 37.6 gpm, which corresponds to a MTFR to effective filtration treatment area ratio of 1.80 gpm/ft2. The system, operating at 100% of the MTFR with an average influent concentration of 201.3 mg/L, had an average removal efficiency of 99 percent. b. GHL evaluated sediment mass loading capacity over an additional 16 events using an influent SSC concentration of 400 mg/L. The first 11 runs were evaluated at 100% of the MTFR. The BioPod began to bypass, so the remaining 5 runs were evaluated at 90% of the MTFR. The total mass of the sediment captured was 245.0 lbs and the cumulative mass removal efficiency was 96.3%. 2. Herrera Environmental Consultants Inc. conducted laboratory testing in September 2014 at the Seattle University Engineering Laboratory. The testing evaluated the flushing characteristics, hydraulic conductivity, and pollutant removal ability of twelve different media blends. Based on this testing, Oldcastle Infrastructure, Inc. selected one media blend, Mix 8, for inclusion in their TAPE evaluation of the BioPod™ Biofilter. a. Herrera evaluated Mix 8 in an 8-inch diameter by 36-inch tall polyvinyl chloride (PVC) column. The column contained 18-inches of Mix 8 on top of 6-inches of pea gravel. The BioPod will normally include a 3-inch mulch layer on top of the media layer; however, this was not included in the laboratory testing. b. Mix 8 has a hydraulic conductivity of 218 inches per hour; however, evaluation of the pollutant removal ability of the media was based on an infiltration rate of 115 inches per hour. The media was tested at 75%, 100%, and 125% of the infiltration rate. Based on the lab test results: The system was evaluated using natural stormwater. The dissolved copper and dissolved zinc concentrations in the natural stormwater were lower than the TAPE influent standards; therefore, the stormwater was spiked with 66.4 mL of 100 mg/L Cu solution and 113.6 mL of 1,000 mg/L Zn solution. The BioPod removed an average of 81% of TSS, with a mean influent concentration of 48.4 mg/L and a mean effluent concentration of 9.8 mg/L. The BioPod removed an average of 94% of dissolved copper, with a mean influent concentration of 10.6 µg/L and a mean effluent concentration of 0.6 µg/L. The BioPod removed an average of 97% of dissolved zinc, with a mean influent concentration of 117 µg/L and a mean effluent concentration of 4 µg/L. The BioPod removed an average of 97% of total phosphorus, with a mean influent concentration of 2.52 mg/L and a mean effluent concentration of 0.066 mg/L. When total phosphorus influent concentrations were capped at the TAPE upper limit of 0.5 mg/L, calculations showed an average removal of 87%. Other BioPod Related Issues to be Addressed By the Company: 1. Conduct hydraulic testing to obtain information about maintenance requirements on a site with runoff that is more typical of the Pacific Northwest. Technology Description: Download at https://oldcastleprecast.com/stormwater/bioretention- biofiltration-applications/bioretention-biofiltration- solutions/ Contact Information: Applicant: Chris Demarest Oldcastle Infrastructure, Inc. (925) 667-7100 Chris.demarest@oldcastle.com Applicant website: https://oldcastleprecast.com/stormwater/ Ecology web link: https://ecology.wa.gov/Regulations-Permits/Guidance-technical- assistance/Stormwater-permittee-guidance-resources/Emerging-stormwater-treatment- technologies Ecology: Douglas C. Howie, P.E. Department of Ecology Water Quality Program (360) 407-6444 douglas.howie@ecy.wa.gov Revision History Date Revision March 2018 GULD granted for Basic Treatment March 2018 Provisional GULD granted for Enhanced and Phosphorus Treatment June 2016 PULD Granted April 2018 GULD for Basic and Provisional GULD for Enhanced and Phosphorus granted, changed name to BioPod from TreePod July 2018 GULD for Enhanced and Phosphorus granted September 2018 Changed Address for Oldcastle December 2018 Added minimum media thickness requirement May 2019 Changed language on who must Install and maintain the device from Oldcastle to Applicants SECTION 3 INSPECTION & MAINTENANCE Maintenance Specifications BIOMOD®DRAINA G E P R OTECTION SY ST E MSA division of Oldcastle Infrastructure MODULAR BIORETENTION SYSTEM Scope Federal, State and Local Clean Water Act regulations and those of insurance carriers require that post- construction stormwater Best Management Practices (BMPs) be performed on a recurring basis. The intent of the regulations is to ensure that the BMPs, on a continuing basis, efficiently remove pollutants from stormwater runoff, thereby preventing pollution of the nation’s water resources. These requirements apply to the BioMod Modular Bioretention System. Recommended Frequency of Service Properly designed and installed bioretention cells require some regular maintenance, most frequently during the first year or two of establishment. Oldcastle Infrastructure recommends that installed BioMod units be inspected and serviced on a recurring basis for sediment buildup, trash removal, erosion, and to evaluate the health of the vegetation. Ultimately, the frequency depends on the amount of runoff, pollutant loading and interference from debris and litter; however, it is recommended that each installation be serviced at least two times per year. Drainage Protection Systems (DPS), a division of Oldcastle Infrastructure, is available to do an onsite evaluation upon request. Recommended Timing of Service Guidelines for the timing of service are as follows: 1. For areas with a definitive rainy season: Prior to and following the rainy season. 2. For areas subject to year-round rainfall: On a recurring basis (at least two times per year). 3. For areas with winter snow and summer rain: Prior to and after the snow season. 4. For installed devices not subject to the elements (wash racks, parking garages, etc.): On a recurring basis (no less than two times per year). Service Procedures 1. Bioretention cells will require supplemental irrigation during the first 2-3 years after planting. Drought tolerant species may need little additional water after this period, except during prolonged drought, when supplemental irrigation may become necessary for plant survival. Verify that the maintenance plan includes a watering schedule for the establishment period and in times of extreme drought after plants have been established. 2. Inspect the inlet surface adjacent to the BioMod unit and the inlet opening for trash and debris accumulation. Remove and dispose as required. 3. For units with pre-filtration, open the access cover of the pre-filtration chamber and inspect for collected pollutants. Remove and dispose of all materials. (Pre-filtration chamber allows for the use of industrial vacuum equipment if available). Close pre-filter access cover. 4. For units with internal bypass overflow screens, check for any blockage or obstructions to the flow path and remove as necessary. Check for any potential future blockage or obstruction beneath and around the overflow screens. Remove and dispose of all materials. 5. Inspect the area beneath the tree grate (when applicable), and if necessary, remove the tree grate and dispose of any collected trash or debris. 6. For units without pre-filtration, remove and replace the mulch layer as necessary, taking care to disturb the plant’s roots as little as possible. Units without pre-filtration may see more sediment enter the system. If sediment buildup reaches 25% of the ponding depth, it should be removed, taking care to minimize soil disturbance. 2 Maintenance SpecificationS 3 7. Inspect for standing water. If present, or if soil media is appreciably moist more than 72 hours following a rain event, carefully remove and replace the top 4-6 inches of soil media (as well as the mulch layer) taking care to disturb the plant’s roots as little as possible. Mulch should be re-applied when erosion is evident. In areas expected to have low metal loads in the runoff, mulch is needed to maintain a 2-3 inch depth. In areas with relatively high metal loads, replace the mulch once per year. 8. While vegetation is being established, remove weeds by hand (weeding frequency should decrease over time, as the vegetation grows). Inspect and prune the plants as needed to maintain adequate shape and health. If vegetation appears to be in poor health with no obvious cause, a landscape specialist should be consulted. Although occasional pruning or trimming might be needed, bioretention cells should generally not be mowed on a regular basis. In some instances where it is desired to maintain fast-growing, annual herbaceous plant cover, annual mowing may be appropriate. 9. Replace dead plants. If a particular species proves to be prone to mortality, it may need to be replaced with a different species that is more likely to succeed on the particular site. Disposal of Collected Debris, Hydrocarbons and Sediment The collected debris, hydrocarbons and sediment shall be disposed of in accordance with local, state and federal agency requirements. Where hazardous materials are encountered, these standard maintenance procedures will be ceased immediately and the property owner notified for further work authorization. DPS also has the capability of servicing all manner of catch basin inserts and catch basins with or without inserts, underground oil/water separators, stormwater interceptors and other such devices. All DPS personnel are highly qualified technicians and are confined-space trained and certified. Call us at (888) 950-8826 for further information and assistance. BUILDINGSTRUCTURES OUR MARKETS TRANSPORTATION WATER ENERGYCOMMUNICATIONS December 2018 v.1 www.oldcastleinfrastructure.com 800-579-8819 BIOMOD® MODULAR BIORETENTION SYSTEM Appendix I Special Reports and Studies REVISED GEOTECHNICAL ENGINEERING REPORT HARRINGTON AVE APARTMENTS NE 10TH STREET AND HARRINGTON AVENUE NE RENTON, WASHINGTON PROJECT NO. 2072.01 November 5, 2019 Prepared for: Renton Housing Authority Prepared by: 19019 36th Avenue W., Suite E Lynnwood, WA 98036 19019 36th Avenue West, Suite E Lynnwood, WA 98036 (425) 582-9928 Project No. 2072.01 November 5, 2019 Renton Housing Authority P.O. Box 2316 Renton, Washington 98056-0316 Attn: Mr. Mark Gropper Subject: Revised Geotechnical Engineering Report Harrington Ave Apartments NE 10th Street and Harrington Avenue NE Renton, Washington Dear Mr. Gropper, In accordance with your request and written authorization, Zipper Geo Associates, LLC (ZGA) has completed the subsurface exploration and geotechnical engineering evaluation for the Harrington Ave Apartments project. This report presents the results of the subsurface exploration, as well as our geotechnical engineering recommendations for the project. Our services were completed in general accordance with our Proposal for Geotechnical Engineering Services (Proposal No. P18283) dated August 23, 2018. Written authorization to proceed on our proposed scope of services was provided by Renton Housing Authority on August 27, 2018. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report, or if we may be of further service, please contact us. Sincerely, Zipper Geo Associates, LLC Robert A. Ross, P.E. Principal 11/5/19 TABLE OF CONTENTS Page INTRODUCTION ........................................................................................................................................... 1 PROJECT UNDERSTANDING .................................................................................................................... 1 SITE CONDITIONS ....................................................................................................................................... 1 Surface Conditions .......................................................................................................................................... 1 Subsurface Conditions ..................................................................................................................................... 2 Groundwater Conditions ................................................................................................................................. 2 LABORATORY TESTING ............................................................................................................................ 3 CONCLUSIONS AND RECOMMENDATIONS ............................................................................................ 3 General Considerations ................................................................................................................................... 3 Geologically Hazardous Areas ......................................................................................................................... 3 Seismic Design Considerations ........................................................................................................................ 4 Site Preparation ............................................................................................................................................... 5 Structural Fill Materials, Placement, and Compaction .................................................................................... 7 Utility Trenching and Backfilling ...................................................................................................................... 8 Construction Dewatering ................................................................................................................................ 9 Shallow Foundation Recommendations .......................................................................................................... 9 On-Grade Concrete Slabs .............................................................................................................................. 10 Permanent Drainage Considerations ............................................................................................................ 11 Retaining Wall ............................................................................................................................................... 11 Stormwater Infiltration Feasibility ................................................................................................................ 12 Pavements ..................................................................................................................................................... 13 CLOSURE ................................................................................................................................................... 14 FIGURES Figure 1 – Site and Exploration Plan APPENDICES Appendix A – Subsurface Exploration Procedures and Logs Appendix B – Laboratory Testing Procedures and Results Cover Page Photo Credit: Google Earth Pro, 2018 Aerial Photo Page 1 REVISED GEOTECHNICAL ENGINEERING REPORT HARRINGTON AVE APARTMENTS RENTON, WASHINGTON Project No. 2072.01 November 5, 2019 INTRODUCTION This report documents the surface and subsurface conditions encountered at the project site and our geotechnical engineering recommendations for the current proposed Harrington Ave Apartments in Renton, Washington. Our geotechnical engineering scope of services for the project included subsurface explorations, laboratory testing, geotechnical engineering analysis, and preparation of this report. The observations and conclusions summarized herein are based in part upon conditions observed in our subsurface explorations and site observations. In the event that site conditions change, it may be necessary to modify the conclusions and recommendations presented in this report. This report is an instrument of service and has been prepared in general accordance with locally accepted geotechnical engineering practice. This report has been prepared for the exclusive use of the Renton Housing Authority, and its agents, for specific application to the subject property and stated purpose. PROJECT UNDERSTANDING The project site consists of five undeveloped parcels zoned as R-14 and located at the northwest corner of the intersection of NE 10th Street and Harrington Ave NE in Renton, Washington. The project site was previously developed with single-family homes that were demolished. We understand the project will consists of developing the site with a 62 unit, 3-story, wood-framed apartment building and related site improvements including underground utilities, pavements, and stormwater management facilities. We expect that the finished floor elevation of the building will be near existing site grades. Grading for the project is expected to consist of cuts and fills with a maximum anticipated depth/thickness of about 5 feet. However, deeper cuts may be required for underground utilities and stormwater management facilities. Design drawings for the proposed apartment building and associated site improvements were not available at the time this report was prepared. Once details regarding the proposed apartment building and additional site improvements are known, we should be consulted to review the details and revise this report if necessary. SITE CONDITIONS Surface Conditions The project site consists of five parcels with a total area of slightly above one acre. The site is bordered to the north by single-family residences, to the east by Harrington Ave NE, to the south by the new extension of NE 10th Street, and to the west by Glennwood Ave NE. Parcel number 7227801305 overlaps with the new construction of the NE 10th Street extension with a portion remaining to the north of the road construction. We anticipate that this portion will be included in the project area. Harrington Ave Apartments ZGA Project No. 2072.01 November 5, 2019 Page 2 Topographically, the site is relatively flat. Ground cover consists primarily of grass with a few scattered large deciduous and coniferous trees. The northwest corner of the project site was used as a staging area for construction equipment associated with the extension of NE 10th Street and is covered with medium gravel. A plan view of the project site is shown on the attached Figure 1, Site and Exploration Plan. Subsurface Conditions Mapped Geology: We reviewed published geologic mapping of the site vicinity through the Washington State Department of Natural Resource’s web-based mapping application Washington Geologic Information Portal (https://geologyportal.dnr.wa.gov/). The published mapping indicates the site is underlain by Vashon glacial till (Qgt). The mapping describes this soil as mostly thin ablation till over lodgment till, deposited by the Puget glacial lobe consisting of a generally compact, coherent unsorted mixture of sand, silt clay and gravel. The mapping notes that north of the Cedar River, where the project site is located, the till is mostly sand. Subsurface Exploration: The subsurface evaluation for this project included advancement of five borings (B-1 through B-5) completed throughout the area of the project site. The borings were extended to depths of about 16 to 26½ feet below the existing ground surface (bgs) and their approximate locations are shown on Figure 1, Site and Exploration Plan. Soils were visually classified in general accordance with the Unified Soil Classification System. Descriptive logs of the subsurface explorations and the procedures utilized in the subsurface exploration program are presented in Appendix A. A generalized description of soil conditions encountered in the explorations is presented below. Please refer to the exploration logs in Appendix A for a more detailed description of the conditions encountered at each exploration location. Soil conditions observed in the borings generally consisted of three to twelve feet of medium dense to dense sand with variable silt and gravel contents. Below this layer we encountered very dense sand with variable silt and gravel contents that we interpret to be glacial till. All the explorations terminated within the glacial till. The upper 4 to 5 feet of soils observed in our explorations was interpreted to be possibly undocumented fill associated with previous development of the site and possibly demolition of the previously existing homes. Groundwater Conditions Groundwater was not encountered within our explorations. Fluctuations in groundwater levels will likely occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the exploration was performed. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher than indicated on the logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project. Harrington Ave Apartments ZGA Project No. 2072.01 November 5, 2019 Page 3 LABORATORY TESTING Laboratory testing included soil moisture content, grain size distribution, and modified proctor tests on selected samples obtained from our explorations. The results of the moisture content tests are presented on the boring logs in Appendix A and the grain size distribution and modified proctor test results are presented in Appendix B. In general, moisture content testing indicates the sands within the upper 10 feet of existing site grade had moisture contents ranging from about 4 to 12 percent with an average of about 9 percent. Grain size distribution testing indicates the sands within the upper 7 feet of existing site grade had fines contents ranging from about 19 to 30 percent. We collected cuttings from the auger and performed a modified proctor test on the material. The modified proctor test yielded a maximum dry density of 136.2 pcf and an optimum moisture content of 8.3 percent. CONCLUSIONS AND RECOMMENDATIONS General Considerations Based on the results of our subsurface investigation as described in previous sections, it is our opinion the proposed building can be supported on conventional shallow foundations bearing on medium dense to very dense native soil or structural fill placed on properly prepared native soils, contingent on proper design and construction practices and implementation of the recommendations presented in this report. Geotechnical engineering recommendations for conventional shallow foundations and other earthwork related phases of the project are presented below. The recommendations contained in this report are based upon the results of field and laboratory testing (which are presented in Appendices A and B), engineering analyses, and our current understanding of the proposed project. ASTM and Washington State Department of Transportation (WSDOT) specification codes cited herein respectively refer to the current manual published by the American Society for Testing & Materials and the 2016 edition of the Standard Specifications for Road, Bridge, and Municipal Construction (M41-10). Geologically Hazardous Areas As part of our services, we evaluated the presence of regulated geologically hazardous areas (GHAs) at the site. Chapter 4-3-050 of the Renton Municipal Code (the Code) designates GHAs as Erosion, Landslide, Seismic, and Coal Mine Hazard Areas. Steep Slope Hazard Areas: The code defines steep slope hazard areas as areas with an average slope of 25 percent or greater with a total relief of 15 feet or greater, or having an average slope of 40 percent or greater. The project site does not meet the definition of a steep slope area. Landslide Hazard Areas: The code defines a low landslide hazard area as an area with slopes less than fifteen percent. Based on the relative flat topography, the site classifies as having a “low landslide hazard”, based on the code definition. Harrington Ave Apartments ZGA Project No. 2072.01 November 5, 2019 Page 4 Erosion Hazard Areas: The code characterizes sites as having a low or high erosion hazard based on information available through the Natural Resource Conservation Service (NRCS). The NRCS maps the site as being 70% Arents, Alderwood material (AmC) and 30% Ragnar-Indianola association both with a slope less than 15 percent. Therefore, the site classifies as having a “low erosion hazard”, based on the code definition. Seismic Hazard Areas: The code characterizes sites as having either “low seismic hazard” or “high seismic hazard” based on the subsurface conditions. A low seismic hazard area is defined as an area underlain by dense soils or bedrock, generally having site classifications of A through D, as defined in the International Building Code, 2012. It is our opinion that the project site classifies as having a “low seismic hazard”, based on the code definition. More detailed information regarding seismic hazards is provided in the seismic design considerations section of this report. Coal Mine Hazard Areas: The code defines areas with low coal mine hazards as areas with no known mine workings and no predicted subsidence. We reviewed the King County iMap for coal mine hazard mapping as well as the Coal Mine Map Database located within the Washington State Department of Natural Resources online Washington Geologic Information Portal. Based on a review of the readily available information provided by these sources, no coal mine workings are documented within close vicinity of the project site. Therefore, in our opinion the project site classifies as having a “low coal mine hazard”, based on the code definition. Seismic Design Considerations The tectonic setting of western Washington is dominated by the Cascadia Subduction Zone formed by the Juan de Fuca plate subducting beneath the North American Plate. This setting leads to intraplate, crustal, and interplate earthquake sources. Seismic hazards relate to risks of injury to people and damage to property resulting from these three principle earthquake sources. Ground Surface Rupture: Based on our review of the USGS Quaternary age fault database for Washington State, an inferred fault trace of the Seattle Fault Zone is located approximately 1 ½-miles to the north and northwest of the project site. As the fault does not appear to cross the site, it is our opinion that the risk of ground surface rupture at the site is low. Landsliding: Based on the relatively flat topography of the site and surrounding vicinity, it is our opinion that the risk of earthquake-induced landsliding is low. Soil Liquefaction: Liquefaction is a phenomenon wherein cohesionless soils below the groundwater table build up excess pore water pressures during earthquake loading. Liquefaction typically occurs in loose, cohesionless soils, but may occur in denser soils if the ground shaking is sufficiently strong. The potential hazardous impacts of liquefaction include liquefaction-induced settlement and lateral spreading. Soil conditions observed in our explorations consisted of dense to very dense sands with variable silt/gravel Harrington Ave Apartments ZGA Project No. 2072.01 November 5, 2019 Page 5 contents. We did not encounter groundwater within our explorations. Based on the subsurface conditions we encountered on the site, it is our opinion that the risk of liquefaction is low. IBC Seismic Design Parameters: Based on site location and soil conditions, the values provided below are recommended for seismic design. The values provided below are based on the 2015 IBC as the building code reference document. Site Preparation Erosion Control Measures: Stripped surfaces and soil stockpiles are typically a source of runoff sediments. We recommend that silt fences, berms, and/or swales be installed around the downslope side of stripped areas and stockpiles in order to capture runoff water and sediment. If earthwork occurs during wet weather, we recommend that all stripped surfaces be covered with straw to reduce runoff erosion, whereas soil stockpiles should be protected with anchored plastic sheeting. Temporary Drainage: Stripping, excavation, grading, and subgrade preparation should be performed in a manner and sequence that will provide drainage at all times and provide proper control of erosion. The site should be graded to prevent water from ponding in construction areas and/or flowing into and/or over excavations. Exposed grades should be crowned, sloped, and smooth-drum rolled at the end of each day to facilitate drainage if inclement weather is forecasted. Accumulated water must be removed from subgrades and work areas immediately and prior to performing further work in the area. Equipment access may be limited and the amount of soil rendered unfit for use as structural fill may be greatly increased if drainage efforts are not accomplished in a timely manner. Description Value 2015 IBC Site Classification 1 C Ss Spectral Acceleration for a Short Period 1.430 g (Site Class B) S1 Spectral Acceleration for a 1-Second Period 0.537 g (site Class B) SMS Maximum considered spectral response acceleration for a Short Period 1.430 g (Site Class C) SM1 Maximum considered spectral response acceleration for a 1-Second Period 0.699 g (Site Class C) SDS Five-percent damped design spectral response acceleration for a Short Period 0.953 g (Site Class C) SD1 Five-percent damped design spectral response acceleration for a 1-Second Period 0.466 g (Site Class C) 1. In general accordance with the 2015 International Building Code, Table 1613.5.2. IBC Site Class is based on the average characteristics of the upper 100 feet of the subsurface profile. The borings completed for this study extended to a maximum depth of 26½ feet below grade. ZGA therefore determined the Site Class assuming that similar density soils extend to 100 feet as suggested by published geologic maps for the project area. Harrington Ave Apartments ZGA Project No. 2072.01 November 5, 2019 Page 6 Clearing and Stripping: Once TESC measures are installed, we expect site preparation to continue with clearing and grubbing brush and trees, and stripping of organic rich topsoil. We recommend all tree stumps and roots larger than ½ inch in diameter be cleared and grubbed from the areas planned for improvement. Based on our explorations, stripping depths to remove topsoil is estimated to be about 6 inches. Stripping depths may be greater near trees and brush to fully remove root systems. All clearing and stripping debris should be wasted off site or, if approved, used for topsoil in landscape areas. Subgrade Preparation: Once site preparation is complete, all areas that are at design subgrade elevation or areas that will receive new structural fill should be moisture conditioned to a moisture content within plus or minus two percent of optimum moisture content for compaction. The subgrade should then be compacted to a firm and unyielding condition. The existing near-surface site soils consist of loose to dense silty sand or sand with silt at or generally somewhat above optimum moisture content for compaction. During wet weather, achieving a moisture content adequate for compaction will be impossible. Therefore, we recommend subgrade preparation and earthwork, in general, be completed during drier periods of the year when the soil moisture content can be controlled by aeration and drying. If earthwork or construction activities take place during extended periods of wet weather, or if the in situ moisture conditions are elevated above the optimum moisture content, the soils will become unstable and not compactable. In the event the exposed subgrade becomes unstable, yielding, or unable to be compacted due to high moisture conditions, we recommend that the materials be removed to a sufficient depth in order to develop stable subgrade soils that can be compacted to the minimum recommended levels. The severity of construction problems will be dependent, in part, on the precautions that are taken by the contractor to protect the subgrade soils. Once compacted, subgrades should be evaluated through density testing and proof rolling with a loaded dump truck or heavy rubber-tired construction equipment weighing at least 20 tons to assess the subgrade adequacy and to detect soft and/or yielding soils. In the event that compaction fails to meet the specified criteria, the upper 12 inches of subgrade should be scarified and moisture conditioned as necessary to obtain at least 95 percent of the maximum laboratory density (per ASTM D1557). Those soils which are soft, yielding, or unable to be compacted to the specified criteria should be over-excavated and replaced with suitable material as recommended in the Structural Fill section of this report. As an alternate to subgrade compaction during wet site conditions or wet weather, the upper 12 inches of subgrade should be overexcavated to a firm, non-yielding and undisturbed condition and backfilled with compacted imported structural fill consisting of free-draining Gravel Borrow or crushed rock. Freezing Conditions: If earthwork takes place during freezing conditions, exposed subgrades should be allowed to thaw and then be compacted prior to placing subsequent lifts of structural fill. Alternatively, the frozen material could be stripped from the subgrade to expose unfrozen soil prior to placing subsequent lifts of fill or foundation components. The frozen soil should not be reused as structural fill until allowed to thaw and adjusted to the proper moisture content, which may not be possible during winter months. Harrington Ave Apartments ZGA Project No. 2072.01 November 5, 2019 Page 7 Structural Fill Materials, Placement, and Compaction Structural fill includes any material placed below or adjacent to foundations, below concrete slabs, within utility trenches, or other areas to support settlement-sensitive site improvements. Prior to the placement of structural fill, all surfaces to receive fill should be prepared as previously recommended in the Site Preparation section of this report. Laboratory Testing: Representative samples of on-site and imported soils to be used as structural fill should be submitted for laboratory testing at least 4 days in advance of its intended use in order to complete the necessary Proctor tests. Reuse of Site Soils as Structural Fill: We expect that the finished grade will stay very close to the existing grade and therefore no substantial fill placement will be required. However, we expect the reuse of site soils as structural fill will be desirable for underground utilities. The suitability for reuse of site soils as structural fill depends on the composition and moisture content of the soil. Soils encountered in excavations at the site are expected to consist of silty sand or sand with silt. As the amount of fines increases, the soil becomes increasingly sensitive to small changes in moisture content. Soils containing more than about 5 percent fines cannot be consistently compacted to the appropriate levels when the moisture content is more than approximately 2 percent above or below the optimum moisture content (per ASTM D1557). Optimum moisture content is the moisture content which results in the greatest compacted dry density with a specified compactive effort. Laboratory testing of select soil samples indicates the in-place moisture content of site soils ranges from about 4 to 12 percent. Based on the results of the modified proctor test, the optimum moisture content of site soils is 8.3 percent. Therefore, site soils appear near the optimum moisture content for compaction. Site soils should be suitable for structural fill during periods of dry weather with some slight moisture conditioning. However, during wet weather, site soils will quickly become too wet for reuse as structural fill. Therefore, we recommend earth work for the project be scheduled for the drier summer months. Imported Structural Fill: The appropriate type of imported structural fill will depend on weather conditions. During extended periods of dry weather, we recommend imported fill, at a minimum, meet the requirements of Common Borrow as specified in Section 9-03.14(3) of the 2016 Washington State Department of Transportation, Standard Specifications for Road, Bridge, and Municipal Construction (WSDOT Standard Specifications). During wet weather and/or wet site conditions, higher-quality structural fill might be required, as Common Borrow may contain sufficient fines to be moisture-sensitive. During wet conditions, we recommend that imported structural fill consist of a “clean”, free-draining pit- run sand and gravel. Such material should generally contain less than 5 percent fines, based on that soil fraction passing the U.S. No. 4 sieve, and not contain discrete particles greater than 3 inches in maximum dimension. Alternatively, Crushed Surfacing Base Course or Gravel Borrow conforming to Sections 9- 03.9(3) and 9-03.14(1), respectively, of the WSDOT Standard Specifications could be used during wet Harrington Ave Apartments ZGA Project No. 2072.01 November 5, 2019 Page 8 weather. It should be noted that the placement of structural fill is, in many cases, is weather-dependent. Delays due to inclement weather are common, even when using select granular fill. We recommend that site grading and earthwork be scheduled for the drier months, if possible. Fill Placement and Compaction: Structural fill should be placed in horizontal lifts of a thickness adequate for adequate compaction throughout the entire lift thickness with the compaction equipment used. Typically, the maximum loose lift thickness that can be adequately compacted with typical compaction equipment is 12 inches. However, in cases where large vibratory rollers and imported fill with less than 5% fines are used, the lift thickness can be increased. Increasing the loose lift thickness beyond 12 inches should be based on field performance testing during construction prior to placement of production fills. Thinner lifts may be necessary, depending on the size and weight of the compaction equipment. Each lift of fill should be compacted to the minimum levels recommended in the table below based on the maximum laboratory dry density as determined by the ASTM D 1557 Modified Proctor Compaction Test. Structural fill placed in municipal rights-of-way should be placed and compacted in accordance with the jurisdiction codes and standards. We recommend that a geotechnical engineer be present during grading so that an adequate number of density tests may be conducted as structural fill placement occurs. In this way, the adequacy of the earthwork may be evaluated as it proceeds. Recommended Soil Compaction Levels Location Minimum Percent Compaction* Stripped native subgrade soils, prior to fill placement (upper 12 inches) 95 All fill below building floor slabs and foundations 95 Upper two feet of fill below pavement finished grade 95 Pavement fill below two feet from finished grade 92 Utility trench backfill greater than two feet from finished grade 92 Upper two feet of trench backfill from finished grade 95 Landscape Areas 90 * ASTM D 1557 Modified Proctor Maximum Dry Density Utility Trenching and Backfilling We recommend that utility trenching conform to all applicable federal, state, and local regulations, such as OSHA and WISHA, for open excavations. Trench excavation safety guidelines are presented in WAC Chapter 296-155 and WISHA RCW Chapter 49.17. Utility Subgrade Preparation: We recommend that all utility subgrades be firm and unyielding and free of soils that are loose, disturbed, or pumping. Soils that pump or yield should be removed and replaced. All structural fill used to replace over-excavated soils should be compacted as recommended in the Structural Fill section of this report. Bedding and Initial Backfill: We recommend that a minimum of 4 inches of bedding material be placed below and at least 12 inches above all utilities or in general accordance with the utility manufacturer’s Harrington Ave Apartments ZGA Project No. 2072.01 November 5, 2019 Page 9 recommendations and local ordinances. We recommend the bedding consist of granular material free from particles greater than 3 inches. All trenches should be wide enough to allow for compaction around the haunches of the pipe, or material such as pea gravel should be used below the spring line of the pipes to eliminate the need for mechanical compaction in this portion of the trenches. If water is encountered in the excavations, it should be removed prior to fill placement. Trench Backfill: Materials, placement and compaction of utility trench backfill should be in accordance with the recommendations presented in the Structural Fill section of this report. In our opinion, the initial lift thickness should not exceed 1 foot unless recommended by the manufacturer to protect utilities from damage by compacting equipment. Light, hand operated compaction equipment may be utilized directly above utilities if damage resulting from heavier compaction equipment is of concern. Construction Dewatering Groundwater was not encountered in our explorations. If groundwater is encountered during construction, some form of temporary dewatering may be required. Conventional dewatering methods, such as pumping from sump pits, should likely be adequate for temporary removal of groundwater encountered during shallow excavation at the site. Construction dewatering systems should be designed, maintained, and permitted by the contractor. Shallow Foundation Recommendations We recommend the building foundations be supported on the medium dense to very dense soils encountered in our explorations at a depth of 2.5 to 4 feet below existing site grades. Based on the results of our explorations, some loose, undocumented fill may be encountered at footing subgrade elevations. As such, some over-excavation and replacement of loose, undocumented fill with structural fill may be required. The need for over-excavation and replacement of loose, undocumented fill should be evaluated by a representative from Zipper Geo Associates during construction. Where over-excavation is required, the width of the over-excavation beyond footing edges should be equal to the required over-excavation depth. For example, if the footing width is 12 inches and an over-excavation depth of two feet is required, the total width of the over-excavation should be five feet. As an alternative, the width of over-excavations can be limited to the footing width provided the over-excavation is backfilled with controlled density fill or lean mix concrete having a minimum 28 day compressive strength of 100 psi. Over-excavation and replacement with structural fill shall be in accordance with the recommendations provided in the Structural Fill Materials, Placement and Compaction section of this report. Recommendations for shallow spread footings are provided below. Subgrade Preparation: Where loose, undocumented fill is not encountered at footing subgrade elevation, we recommend that the subgrade exposed at the bottom of foundation excavations be compacted to a firm and non-yielding condition and to at least 95 percent of the modified Proctor maximum dry density determined in accordance with ASTM D 1557. If the exposed subgrade cannot be compacted to the required density, we recommend that it be removed to an adequate depth as recommended by a representative from ZGA and replaced with compacted structural fill placed in accordance with this report. Harrington Ave Apartments ZGA Project No. 2072.01 November 5, 2019 Page 10 Allowable Bearing Pressure: Continuous and isolated column footings bearing on subgrades prepared as recommended above may be designed for a maximum allowable, net, bearing pressure of 3,000 psf if supported as recommended in this report. A one-third increase of the bearing pressure may be used for short-term transient loads such as wind and seismic forces. Shallow Foundation Depth and Width: For frost protection, the bottom of all exterior footings should bear at least 18 inches below the lowest adjacent outside grade, whereas the bottoms of interior footings should bear at least 12 inches below the surrounding slab surface level. We recommend that all continuous wall and isolated column footings be at least 12 and 24 inches wide, respectively. Lateral Resistance: Resistance to lateral loads can be calculated assuming a ultimate passive resistance of 405 pcf equivalent fluid pressure (triangular distribution) for footings backfilled with structural fill as recommended in this report. We recommend an ultimate base friction coefficient of 0.50. If allowable stress design is used, we recommend a minimum safety factor of 1.5 be used for lateral resistance calculations. We recommend that passive resistance be neglected in the upper 18 inches of embedment. Estimated Settlement: Assuming the foundation subgrade soils and structural fill compaction are completed in accordance with recommendations presented herein, we estimate that total static footing settlements will be 1 inch or less. We estimate that differential footing settlement will be ½ inch or less in 40 feet. Subsurface Drainage: Although no groundwater was encountered in our explorations, as a precautionary measure, we recommend a perimeter footing drain be installed around the building to collect surface water infiltration if impermeable hard surfacing, such as asphalt pavement, is not extended to the foundation walls of the building. The perimeter footing drain should consist of a 4-inch-diameter perforated pipe within an envelope of pea gravel or washed rock, extending at least 6 inches on all sides of the pipe. The gravel envelope should be wrapped with filter fabric (such as Mirafi 140N) to reduce the migration of fines from the surrounding soil. The invert of the footing drain should be placed no higher than the bottom of the footing. The perforations should be placed down. The perimeter foundation drain with cleanouts should not be connected to roof downspout drains and should be constructed to discharge into the site storm water system or other appropriate outlet. On-Grade Concrete Slabs Subgrade Preparation: Subgrades for on-grade slabs should be prepared in accordance with the Site Preparation and Structural Fill sections of this report. Slab Base: To provide a uniform slab bearing surface, capillary break, and even working surface, we recommend that on-grade slabs be underlain by a 6-inch thick layer of clean, compacted crushed rock meeting the requirements of Crushed Surfacing Top Course as specified in Section 9-03.9(3) of the WSDOT Standard Specifications with the modification that a maximum of 7.5 percent of the material passes the U.S. No 200 sieve. Harrington Ave Apartments ZGA Project No. 2072.01 November 5, 2019 Page 11 Vapor Barrier: From a geotechnical perspective, a vapor barrier is not considered necessary beneath the slab on grade floor unless moisture sensitive floor coverings and/or adhesives are used. If a vapor barrier is used, we recommend using a 10-mil (minimum), puncture-resistant proprietary product such as Stego Wrap, or an approved equivalent that is classified as a Class A vapor retarder in accordance with ASTM E 1745. Overlap lengths and the appropriate tape used to seal the laps should be in accordance the vapor retarder manufacturer’s recommendations. When conditions warrant the use of a vapor retarder, the slab designer and slab contractor should refer to ACI 302 and ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder/barrier. Permanent Drainage Considerations Surface Drainage: Final site grades should be sloped to carry surface water away from buildings and other drainage-sensitive areas. Additionally, site grades should be designed such that concentrated runoff on softscape surfaces is avoided. Any surface runoff directed towards softscaped slopes should be collected at the top of the slope and routed to the bottom of the slope and discharged in a manner that prevents erosion. Retaining Wall Lateral Earth Pressures: The lateral soil pressures acting on backfilled retaining walls will depend on the nature and density of the soil behind the wall, and the ability of the wall to yield in response to the earth loads. Yielding walls (i.e. walls that are free to translate or rotate) that are able to displace laterally at least 0.001H, where H is the height of the wall, may be designed for active earth pressures. Non-yielding walls (i.e. walls that are not free to translate or rotate) should be designed for at-rest earth pressures. Non-yielding walls include walls that are braced to another wall or structure, and wall corners. Assuming that walls are backfilled and drained as described in the following paragraphs, we recommend that yielding walls supporting horizontal backfill be designed using an equivalent fluid density of 35 pcf (active earth pressure). Non-yielding walls should be designed using an equivalent fluid density of 50 pcf (at-rest earth pressure). Surcharge pressures due to sloping backfill, adjacent footings, vehicles, construction equipment, etc. must be added to these lateral earth pressure values. For traffic loads, we recommend using an equivalent two-foot soil surcharge of about 250 psf. For yielding and non-yielding walls with level backfill conditions, we recommend that a uniformly distributed seismic pressure of 7H psf for the active case and 12H psf for the at-rest case, where H is the height of the wall, be applied to the walls. The above equivalent fluid pressures are based on the assumption of no buildup of hydrostatic pressure behind the wall. If groundwater is allowed to saturate the backfill soils, hydrostatic pressures will act against a retaining wall; however, if the recommended drainage system is included with each retaining wall, we do not expect that hydrostatic pressures will develop. Harrington Ave Apartments ZGA Project No. 2072.01 November 5, 2019 Page 12 Adequate drainage measures must be installed to collect and direct subsurface water away from subgrade walls. All backfilled walls should include a drainage aggregate zone extending a minimum of two feet from the back of wall for the full height of the wall and wide enough at the base of the wall to allow seepage to flow to the footing drain. The drainage aggregate should consist of material meeting the requirements of WSDOT 9-03.12(2), Gravel Backfill for Walls. A minimum 4-inch diameter, perforated PVC drain pipe should be provided at the base of backfilled walls to collect and direct subsurface water to an appropriate discharge point. We recommend placing a non-woven geotextile, such as Mirafi 140N, or equivalent, around the free draining backfill material. Stormwater Infiltration Feasibility Stormwater design in the City of Renton is regulated by the 2017 Renton Stormwater Design Manual (SWDM). The SWDM requires evaluation of design criteria for determination of infiltration feasibility for available infiltration BMPs including full infiltration, limited infiltration, bioretention, and permeable pavements. The purpose of this section is to evaluate the design criteria applicable to geotechnical elements and provide our opinion on feasibility. For purposes of evaluating design criteria, we recommend assuming the depth to an impermeable layer (i.e. hardpan) at this site is 3 feet below existing site grade. • Full Infiltration: The SWDM requires existing soils to be coarse sands, cobbles, or medium sands where the infiltration device will be located. Site soils are gravelly sandy loams and therefore, full infiltration is not feasible. • Limited Infiltration: The SWDM requires that the measured distance (separation) between the bottom of the infiltration device and top of an impermeable layer be at least 3 feet. The recommended depth to hardpan at this site is 3 feet below existing site grade. The bottom of an infiltration device at this site would be located below existing site grades and therefore the minimum separation distance is not achievable. As such, limited infiltration is not feasible. • Bioretention: The SWDM requires a minimum separation of 1 foot between the bottom of a bioretention facility and the top of an impermeable layer. Based on our conversations with the project civil engineer, the bottom of a bioretention facility at this site would be 2.5. to 3.5 feet below existing site grade. The required separation distance to an impermeable layer cannot be achieved with the proposed bottom of facility elevations and therefore bioretention is not feasible. • Permeable Pavements: We found no geotechnical criteria that would result in permeable pavement infeasibility. However, the following comments regarding the SWDM design criteria should be reviewed for permeable pavement design: o Pollution Generating Soils Criteria for Groundwater Protection: The organic matter content and cation exchange capacity of the receptor soils is unknown. Therefore, a 6 inch layer of sand beneath the permeable pavement should be utilized as recommended in the SWDM. Harrington Ave Apartments ZGA Project No. 2072.01 November 5, 2019 Page 13 o Underdrain: The project civil engineer should evaluate the need for an underdrain based on proposed finished grades, permeable pavement section thickness, and our recommendation to assume that an impermiable layer exists at 3 feet below existing site grades for determination of the need for an underdrain as outlined in the SWDM. Pavements Pavement Life and Maintenance: It should be realized that asphaltic pavements are not maintenance- free. The following pavement sections represent our minimum recommendations for an average level of performance during a 20-year design life; therefore, an average level of maintenance will likely be required. A 20-year pavement life typically assumes that an overlay will be placed after about 12 years. Thicker asphalt, base, and subbase courses would offer better ling-term performance, but would cost more initially. Conversely, thinner courses would be more susceptible to “alligator” cracking and other failure modes. As such, pavement design can be considered a compromise between a high initial cost and low maintenance costs versus a low initial cost and higher maintenance costs. The recommendations presented below are based on AASHTO Low-Volume Road Design methodologies as presented in the 1993 AASHTO Guide for Design of Pavement Structures. Traffic and Reliability: Our design assumes 100,000, 18-kip equivalent single axle loads over the life of the pavement along the main access roads and a 75% reliability. Soil Design Values: Pavement subgrade soils are anticipated to consist of the medium stiff silt deposit we encountered in our explorations. Our analysis assumes a minimum California Bearing Ration (CBR) value of 10 is appropriate for this material. Recommended Pavement Sections: For light duty pavements (parking stalls), we recommend 2 inches of asphalt concrete over 4 inches of crushed rock base course. For heavy duty pavements (main access roads, truck delivery routes, etc.), we recommend 3 inches of asphalt concrete over 6 inches of crushed rock base course. A thicker asphalt section or concrete pavements should be considered in front of dumpster enclosures. Materials and Construction: We recommend the following regarding asphalt pavement materials and pavement construction. • Subgrade Preparation: Upper 24 inches of pavement subgrade should be prepared in accordance with the recommendations presented in the Subgrade Preparation section of this report. • Asphalt Concrete: We recommend that the asphalt concrete conform to Section 9-02.1(4) for PG 58-22 or PG 64-22 Performance Graded Asphalt Binder as presented in the WSDOT Standard Specifications. We also recommend that the gradation of the asphalt aggregate conform to the Harrington Ave Apartments ZGA Project No. 2072.01 November 5, 2019 Page 14 aggregate gradation control points for ½-inch mixes as presented in Section 9-03.8(6), HMA Proportions of Materials. • Base Course: We recommend that the crushed aggregate base course conform to Section 9-03.9(3) of the WSDOT Standard Specifications. • Compaction: All base material should be compacted to at least 95 percent of the maximum dry density determined in accordance with ASTM D1557. We recommend that asphalt be compacted to a minimum of 92 percent of the Rice (theoretical maximum) density or 96 percent of Marshall (Maximum laboratory) density. We recommend that a Portland cement concrete pavement (CCP) be utilized in entrance and exit sections, dumpster pads, loading dock areas, drive-thru areas or other areas where extensive wheel maneuvering or repeated loading are expected. The dumpster pad should be large enough to support the wheels of the truck which will bear the load of the dumpster. We recommend a minimum of 6 inches of CCP underlain by 4 inches of crushed aggregate base. Although not required for structural support, the base course layer is recommended to help reduce potentials for slab curl, shrinkage cracking, and subgrade “pumping” through joints. Proper joint spacing will also be required to prevent excessive slab curling and shrinkage cracking. All joints should be sealed to prevent entry of foreign material and dowelled where necessary for load transfer. Portland cement concrete should be designed with proper air-entrainment and have a minimum compressive strength of 4,000 psi after 28 days of laboratory curing. Adequate reinforcement and number of longitudinal and transverse control joints should be placed in the rigid pavement in accordance with ACI requirements. The joints should be sealed as soon as possible (in accordance with sealant manufacturer’s instructions) to minimize water infiltration into the soil. CLOSURE The analysis and recommendations presented in this report are based, in part, on the explorations completed for this study. The number, location, and depth of the explorations for the current phase of the project were completed within the constraints of budget and site access so as to yield the information to formulate our recommendations. Project plans were not available at the time this report was prepared. We therefore recommend Zipper Geo Associates, LLC be provided an opportunity to review the final plans and specifications when they become available in order to assess that the recommendations and design considerations presented in this report have been properly interpreted and implemented into the project design. The performance of shallow foundations and slabs on grade depend greatly on proper site preparation and construction procedures. We recommend that Zipper Geo Associates, LLC be retained to provide Harrington Ave Apartments ZGA Project No. 2072.01 November 5, 2019 Page 15 geotechnical engineering services during the site preparation and foundation construction phases of the project. If variations in subsurface conditions are observed at that time, a qualified geotechnical engineer could provide additional geotechnical recommendations to the contractor and design team in a timely manner as the project construction progresses. This report has been prepared for the exclusive use of Renton Housing Authority, and its agents, for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, express or implied, are intended or made. Site safety, excavation support, and dewatering requirements are the responsibility of others. In the event that changes in the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Zipper Geo Associates, LLC reviews the changes and either verifies or modifies the conclusions of this report in writing. B-4GLENNWOOD AVE NE HARRINGTON AVE NENE 10TH STB-1B-2B-3B-5FIGUREJob No.Zipper Geo Associates, LLC19019 36th Ave. W.,Suite ELynnwood, WASHT. of11SITE AND EXPLORATION PLAN2072.01SEPTEMBER 20181HARRINTON APARTMENTSNE 10TH ST AND HARRINGTON AVE NERENTON, WASHINGTONAPPROXIMATE SCALE IN FEET0808040LEGENDB-1BORING NUMBER ANDAPPROXIMATE LOCATIONAPPROXIMATE PROPERTY LINEREFERENCE: GOOGLE MAPS 2018. APPENDIX A SUBSURFACE EXPLORATION PROCEDURES AND LOGS APPENDIX A SUBSURFACE EXPLORATION PROCEDURES AND LOGS Field Exploration Description Our field exploration for this project included advancing five borings across the proposed site of the project on September 12, 2018. The approximate locations of the explorations are presented on Figure 1, the Site and Exploration Plan. Exploration locations were determined in the field based on hand measurements from existing site features. As such, the exploration locations should be considered accurate only to the degree implied by the measurement method. Descriptive logs of the borings are enclosed in this appendix. A current topographic survey of the site was not available at the time of this report. Therefore, ground surface elevations of the explorations were not determined. The borings were advanced using a truck-mounted drill rig operated by an independent drilling company (Holocene Drilling Inc.) working under subcontract to ZGA. The borings were advanced using the hollow- stem auger drilling method. An engineer from our firm continuously observed the borings, logged the subsurface conditions encountered, and obtained representative soil samples. All samples were stored in moisture-tight containers and transported to our laboratory for further evaluation and testing. Samples were obtained by means of the Standard Penetration Test at 2.5- to 5-foot intervals throughout the drilling operation. The Standard Penetration Test (ASTM D 1586) procedure consists of driving a standard 2-inch outside diameter steel split spoon sampler 18 inches into the soil with a 140-pound hammer free falling 30 inches. The number of blows required to drive the sampler through each 6-inch interval is recorded, and the total number of blows struck during the final 12 inches is recorded as the Standard Penetration Resistance, or “blow count” (N value). If a total of 50 blows is struck within any 6-inch interval, the driving is stopped and the blow count is recorded as 50 blows for the actual penetration distance. The resulting Standard Penetration Resistance values indicate the relative density of granular soils and the relative consistency of cohesive soils. The enclosed boring logs describe the vertical sequence of soils and materials encountered in the borings, based primarily upon our field classifications. Where a soil contact was observed to be gradational, our log indicates the average contact depth. Where a soil type changed between sample intervals, we inferred the contact depth. Our logs also graphically indicate the blow count, sample type, sample number, and approximate depth of each soil sample obtained from the borings. If groundwater was encountered, the approximate groundwater depth, and date of observation, are depicted on the logs. Drilling Company:Bore Hole Dia.: Top Elevation:Drilling Method:Hammer Type: Drill Rig:Logged by: Standard Penetration Test Hammer Weight and Drop: 0 5 10 15 20 25 SAMPLE LEGEND % Fines (<0.075 mm) 2-inch O.D. Split spoon Clean Sand % Water (Moisture) Content 3-inch I.D. Shelby tube Bentonite Plastic Limit Liquid Limit Grout/Concrete Natural Water Content Screened Casing Blank Casing GSA = Grain Size Analysis Date:Project No.: 200W = 200 Wash Analysis Cons. = Consolidation Test Att. = Atterberg Limits NE 10th St & Harrington Ave NE TESTING KEY Groundwater level at time of drilling (ATD) or on date of measurement. Renton, WA Sep-18 2072.01 19019 36th Ave. W, Suite E Lynnwood, WA BORING LOG:B-1 Page 1 of 2 GROUNDWATER LEGEND Harrington Ave Apartments The stratification lines represent the approximate boundaries between soil types. The transition may be gradual. Refer to report text and appendices for additional information. Boring Location: B-1 Date Drilled:Depth (ft)SOIL DESCRIPTION Sample Number SAMPLES Recovery (Inches)Ground WaterPENETRATION RESISTANCE (blows/foot)Blow CountsSoil TestingSee Site and Exploration Plan N/A September 12, 2018 Holocene H.S.A. D90 Truck Rig 8 in. Auto SNM 11/2/120 602040 S-1 18 S-2 18 S-3 0 S-4 8 S-5 18 S-6 18 47 30 20 20 76 72 GSA MC MC 5 inches of organics Dense, damp, light brown, Silty SAND, with gravel (Possible fill) Medium dense, moist, brown, SAND, with silt, trace gravel No Recovery Medium dense, moist, brown-gray, SAND, with silt, some gravel, slight mottling (Weathered Glacial Till) Grades to very dense Very dense, moist, tan, SAND, some silt (Glacial till) Drilling Company:Bore Hole Dia.: Top Elevation:Drilling Method:Hammer Type: Drill Rig:Logged by: Standard Penetration Test Hammer Weight and Drop: 25 30 35 40 45 50 SAMPLE LEGEND % Fines (<0.075 mm) 2-inch O.D. Split spoon Clean Sand % Water (Moisture) Content 3-inch I.D. Shelby tube Bentonite Plastic Limit Liquid Limit Grout/Concrete Natural Water Content Screened Casing Blank Casing GSA = Grain Size Analysis Date:Project No.: 200W = 200 Wash Analysis Cons. = Consolidation Test Att. = Atterberg Limits NE 10th St & Harrington Ave NE TESTING KEY Groundwater level at time of drilling (ATD) or on date of measurement. Renton, WA Sep-18 2072.01 19019 36th Ave. W, Suite E Lynnwood, WA BORING LOG:B-1 Page 2 of 2 GROUNDWATER LEGEND Harrington Ave Apartments The stratification lines represent the approximate boundaries between soil types. The transition may be gradual. Refer to report text and appendices for additional information. Boring Location: B-1 Date Drilled:Depth (ft)SOIL DESCRIPTION Sample Number SAMPLES Recovery (Inches)Ground WaterPENETRATION RESISTANCE (blows/foot)Blow CountsSoil TestingSee Site and Exploration Plan N/A September 12, 2018 Holocene H.S.A. D90 Truck Rig 8 in. Auto SNM 11/2/120 602040 S-7 18 65 GSAVery dense, moist, gray, SAND, with silt, some gravel (Glacial till) Boring terminated at approximately 26 1/2 feet. No groundwater observed during exploration. Drilling Company:Bore Hole Dia.: Top Elevation:Drilling Method:Hammer Type: Drill Rig:Logged by: Standard Penetration Test Hammer Weight and Drop: 0 5 10 15 20 25 SAMPLE LEGEND % Fines (<0.075 mm) 2-inch O.D. Split spoon Clean Sand % Water (Moisture) Content 3-inch I.D. Shelby tube Bentonite Plastic Limit Liquid Limit Grout/Concrete Natural Water Content Screened Casing Blank Casing GSA = Grain Size Analysis Date:Project No.: 200W = 200 Wash Analysis Cons. = Consolidation Test Att. = Atterberg Limits NE 10th St & Harrington Ave NE TESTING KEY Groundwater level at time of drilling (ATD) or on date of measurement. Renton, WA Sep-18 2072.01 19019 36th Ave. W, Suite E Lynnwood, WA BORING LOG:B-2 Page 1 of 1 GROUNDWATER LEGEND Harrington Ave Apartments The stratification lines represent the approximate boundaries between soil types. The transition may be gradual. Refer to report text and appendices for additional information. Boring Location: B-2 Date Drilled:Depth (ft)SOIL DESCRIPTION Sample Number SAMPLES Recovery (Inches)Ground WaterPENETRATION RESISTANCE (blows/foot)Blow CountsSoil TestingSee Site and Exploration Plan N/A September 12, 2018 Holocene H.S.A. D90 Truck Rig 8 inches Auto SNM 11/2/120 602040 S-1 12 S-2 12 S-3 16 S-4 18 S-5 11 49 60 63 73 50/5 MC MC MC MC 6 inches of organics Dense, damp, brown, Silty SAND, with gravel slight mottling (Possible fill) Dense, damp, gray, SAND, with silt and gravel (Weathered Glacial Till) Very dense, moist, gray, SAND, with silt, trace gravel (Glacial Till) Very dense, moist, gray, SAND, with silt, some gravel, slight mottling (Glacial till) Boring terminated at approximately 16 ft. No groundwater observed during time of drilling. Drilling Company:Bore Hole Dia.: Top Elevation:Drilling Method:Hammer Type: Drill Rig:Logged by: Standard Penetration Test Hammer Weight and Drop: 0 5 10 15 20 25 SAMPLE LEGEND % Fines (<0.075 mm) 2-inch O.D. Split spoon Clean Sand % Water (Moisture) Content 3-inch I.D. Shelby tube Bentonite Plastic Limit Liquid Limit Grout/Concrete Natural Water Content Screened Casing Blank Casing GSA = Grain Size Analysis Date:Project No.: 200W = 200 Wash Analysis Cons. = Consolidation Test Att. = Atterberg Limits NE 10th St & Harrington Ave NE TESTING KEY Groundwater level at time of drilling (ATD) or on date of measurement. Renton, WA Sep-18 2072.01 19019 36th Ave. W, Suite E Lynnwood, WA BORING LOG:B-3 Page 1 of 1 GROUNDWATER LEGEND Harrington Apartments The stratification lines represent the approximate boundaries between soil types. The transition may be gradual. Refer to report text and appendices for additional information. Boring Location: B-3 Date Drilled:Depth (ft)SOIL DESCRIPTION Sample Number SAMPLES Recovery (Inches)Ground WaterPENETRATION RESISTANCE (blows/foot)Blow CountsSoil TestingSee Site and Exploration Plan N/A September 12, 2018 Holocene H.S.A. D90 Truck Rig 8 in. Auto SNM 11/2/120 602040 S-1 0 S-2 6 S-3 18 S-4 9 S-5 11 S-6 10 50/2 23 74 50/3 50/5 50/4 GSA MC MC 4 inches of organics Light brown, silty SAND, some gravel (Possible fill) No recovery (Blow counts overstated) Medium dense, moist, gray-tan, SAND, with silt, some gravel (Weathered glacial till) Very dense, moist, gray, silty SAND, some gravel (Glacial till) Grades to with silt and gravel Grades to trace gravel Grades to some silt and gravel Boring terminated at approximately 21 ft. No groundwater observed at the time of drilling. Drilling Company:Bore Hole Dia.: Top Elevation:Drilling Method:Hammer Type: Drill Rig:Logged by: Standard Penetration Test Hammer Weight and Drop: 0 5 10 15 20 25 SAMPLE LEGEND % Fines (<0.075 mm) 2-inch O.D. Split spoon Clean Sand % Water (Moisture) Content 3-inch I.D. Shelby tube Bentonite Plastic Limit Liquid Limit Grout/Concrete Natural Water Content Screened Casing Blank Casing GSA = Grain Size Analysis Date:Project No.: 200W = 200 Wash Analysis Cons. = Consolidation Test Att. = Atterberg Limits NE 10th St & Harrington Ave NE TESTING KEY Groundwater level at time of drilling (ATD) or on date of measurement. Renton, WA Sep-18 2072.01 19019 36th Ave. W, Suite E Lynnwood, WA BORING LOG:B-4 Page 1 of 1 GROUNDWATER LEGEND Harrington Ave Apartments The stratification lines represent the approximate boundaries between soil types. The transition may be gradual. Refer to report text and appendices for additional information. Boring Location: B-4 Date Drilled:Depth (ft)SOIL DESCRIPTION Sample Number SAMPLES Recovery (Inches)Ground WaterPENETRATION RESISTANCE (blows/foot)Blow CountsSoil TestingSee Site and Exploration Plan N/A September 12, 2018 Holocene H.S.A. D90 Truck Rig 8 inches Auto SNM 11/2/120 602040 S-1 6 S-2 18 S-3 12 S-4 0 S-5 8 S-6 4 7 26 50/6 50/3 50/2 50/3 GSA MC MC 2 inches of organics Loose, damp, orange-brown, Gravelly SAND, with silt, trace organics (Possible fill) Medium dense, moist, gray, SAND, with silt, some gravel (Weathered glacial till Very dense, moist, gray-brown, SAND, with silt and gravel (Glacial till) No recovery (Blow counts overstated) Grades to gray, some gravel Grades to with gravel, some silt Boring terminated at approximately 20 1/2 feet. No groundwater observed at the time of drilling. Drilling Company:Bore Hole Dia.: Top Elevation:Drilling Method:Hammer Type: Drill Rig:Logged by: Standard Penetration Test Hammer Weight and Drop: 0 5 10 15 20 25 SAMPLE LEGEND % Fines (<0.075 mm) 2-inch O.D. Split spoon Clean Sand % Water (Moisture) Content 3-inch I.D. Shelby tube Bentonite Plastic Limit Liquid Limit Grout/Concrete Natural Water Content Screened Casing Blank Casing GSA = Grain Size Analysis Date:Project No.: 200W = 200 Wash Analysis Cons. = Consolidation Test Att. = Atterberg Limits NE 10th St & Harrington Ave NE TESTING KEY Groundwater level at time of drilling (ATD) or on date of measurement. Renton, WA Sep-18 2072.01 19019 36th Ave. W, Suite E Lynnwood, WA BORING LOG:B-5 Page 1 of 1 GROUNDWATER LEGEND Harrington Ave Apartments The stratification lines represent the approximate boundaries between soil types. The transition may be gradual. Refer to report text and appendices for additional information. Boring Location: B-5 Date Drilled:Depth (ft)SOIL DESCRIPTION Sample Number SAMPLES Recovery (Inches)Ground WaterPENETRATION RESISTANCE (blows/foot)Blow CountsSoil TestingSee Site and Exploration Plan N/A September 12, 2018 Holocene H.S.A. D90 Truck Rig 8 in. Auto SNM 11/2/120 602040 S-1 9 S-2 10 S-3 9 S-4 6 S-5 14 S-6 6 32 25 50/3 50/6 50/6 50/6 MC MC MC MC 6 inches of organics Dense, moist, tan, SAND, with silt, some gravel (Possible fill) Medium dense, moist, gray, SAND, with silt, some gravel (Weathered glacial till) Very dense, moist, gray, SAND, with silt, trace gravel (Glacial till) Grades to some gravel Grades to some silt Boring terminated at approximately 20 1/2 feet. No groundwater observed at the time of drilling. APPENDIX B LABORATORY TESTING PROCEDURES AND RESULTS APPENDIX B LABORATORY TESTING PROCEDURES AND RESULTS A series of laboratory tests were performed by ZGA during the course of this study to evaluate the index and geotechnical engineering properties of the subsurface soils. Descriptions of the types of tests performed are given below. Visual Classification Samples recovered from the exploration locations were visually classified in the field during the exploration program. Representative portions of the samples were carefully packaged in moisture tight containers and transported to our laboratory where the field classifications were verified or modified as required. Visual classification was generally done in accordance with ASTM D 2488. Visual soil classification includes evaluation of color, relative moisture content, soil type based upon grain size, and accessory soil types included in the sample. Soil classifications are presented on the exploration logs in Appendix A. Moisture Content Determinations Moisture content determinations were performed on representative samples obtained from the explorations to aid in identification and correlation of soil types. The determinations were made in general accordance with the test procedures described in ASTM D 2216. Moisture contents are presented on the exploration logs in Appendix A. Grain Size Distributions A grain size analysis determines the range in diameter of soil particles included in a particular sample. Grain size analyses were performed on representative samples in general accordance with ASTM D 422. The results of the grain size determinations for the samples were used in classification of the soils, and are presented in this appendix. Modified Proctor A modified proctor test determines the maximum dry density and optimum moisture to obtain a maximum density under a certain compaction effort. The modified proctor test was performed on representative samples in general accordance with ASTM D1557. The results of the modified proctor test are presented in Appendix B. 0 10 20 30 40 50 60 70 80 90 100 0.0010.0100.1001.00010.000100.0001000.000PERCENT FINER BY WEIGHTPARTICLE SIZE IN MILLIMETERS GRAIN SIZE ANALYSIS Comments: 36"12"6"3"1 1/2"3/4"3/8"4 10 20 40 60 140 200 Coarse Medium Fine Silt ClayFineCoarse COBBLESBOULDERS GRAVEL SAND FINE GRAINED SIZE OF OPENING IN INCHES U.S. STANDARD SIEVE SIZE HYDROMETER Project No.:PROJECT NAME: Harrington Ave Apartment DATE OF TESTING: Exploration Sample Depth (feet) Moisture (%)Fines (%) Description B-1 2 1/2-4 9.3 Silty SAND, with gravelS-1 30.5 2072.01 9/13/2018 ASTM D 422Test Results Summary Zipper Geo Associates, LLC Geotechnical and Environmental Consultants 0 10 20 30 40 50 60 70 80 90 100 0.0010.0100.1001.00010.000100.0001000.000PERCENT FINER BY WEIGHTPARTICLE SIZE IN MILLIMETERS GRAIN SIZE ANALYSIS Comments: 36"12"6"3"1 1/2"3/4"3/8"4 10 20 40 60 140 200 Coarse Medium Fine Silt ClayFineCoarse COBBLESBOULDERS GRAVEL SAND FINE GRAINED SIZE OF OPENING IN INCHES U.S. STANDARD SIEVE SIZE HYDROMETER Project No.:PROJECT NAME: Harrington Ave Apartments DATE OF TESTING: Exploration Sample Depth (feet) Moisture (%)Fines (%) Description B-1 25-26 1/2 8.3 SAND, with silt, some gravelS-7 12.7 2072.01 9/13/2018 ASTM D 422Test Results Summary Zipper Geo Associates, LLC Geotechnical and Environmental Consultants 0 10 20 30 40 50 60 70 80 90 100 0.0010.0100.1001.00010.000100.0001000.000PERCENT FINER BY WEIGHTPARTICLE SIZE IN MILLIMETERS GRAIN SIZE ANALYSIS Comments: 36"12"6"3"1 1/2"3/4"3/8"4 10 20 40 60 140 200 Coarse Medium Fine Silt ClayFineCoarse COBBLESBOULDERS GRAVEL SAND FINE GRAINED SIZE OF OPENING IN INCHES U.S. STANDARD SIEVE SIZE HYDROMETER Project No.:PROJECT NAME: Harrington Ave Apartments DATE OF TESTING: Exploration Sample Depth (feet) Moisture (%)Fines (%) Description B-3 5-6 1/2 7.3 SAND, with silt, some gravelS-2 27.6 2072.01 9/13/2018 ASTM D 422Test Results Summary Zipper Geo Associates, LLC Geotechnical and Environmental Consultants 0 10 20 30 40 50 60 70 80 90 100 0.0010.0100.1001.00010.000100.0001000.000PERCENT FINER BY WEIGHTPARTICLE SIZE IN MILLIMETERS GRAIN SIZE ANALYSIS Comments: 36"12"6"3"1 1/2"3/4"3/8"4 10 20 40 60 140 200 Coarse Medium Fine Silt ClayFineCoarse COBBLESBOULDERS GRAVEL SAND FINE GRAINED SIZE OF OPENING IN INCHES U.S. STANDARD SIEVE SIZE HYDROMETER Project No.:PROJECT NAME: Harrington Ave Apartments DATE OF TESTING: Exploration Sample Depth (feet) Moisture (%)Fines (%) Description B-4 2 1/2-4 9.1 Gravelly SAND, with siltS-1 19.3 2072.01 9/13/2018 ASTM D 422Test Results Summary Zipper Geo Associates, LLC Geotechnical and Environmental Consultants 90 95 100 105 110 115 120 125 130 135 140 145 150 0 5 10 15 20 25 30 35 40 45Dry Unit Weight (pcf)Moisture Content (%) LABORATORY COMPACTION CURVE Compaction Size Test Standard Mold Harrington Ave Apartments Job No. Job Name Date Tested Sample No. Location Test Results Zipper Geo Associates, LLC 19023 36th Avenue West, Suite D Lynnwood, Washington 98036 (425) 582-9928 Test No.Field Moist.2 3 4 Dry Density (lbs/cu.ft.)132.9 129.4 130.4 #DIV/0! Moisture Content (%)9.3 10.1 6.5 #DIV/0! 1557-B 4-inch 2.80 2.70 2.60 2.50 2.40 Zero Air Voids Curves For Various Specific Gravities 2072.01 Depth / Elevation9/14/2018 09122018 Cuttings 5-7 1/2 ft 134.0 136.2 8.38.3 Maximum Dry Density / Oversize Corrected (pcf) Opt. Moisture Content / Oversize Corrected (%) Sample Description: Comments: Oversize Fraction (%) / Sieve Used 3/49 13110 NE 177th Place #304 * Woodinville, WA 98072 * Anthony@SuperiorNW.com 206-930-5724 July 23, 2019 Project: Pre-construction assessment for property re-development at 1073 Harrington Ave NE, Renton, WA. Parcel numbers 7227801315, 1310, and 1290. Contact: Brent Chastain - Third Place Design 341 NE 91st Street Seattle, WA 98115 Phone – 206 920 9996 Email – Brent@thirdplacedesigncoop.com Objectives: Evaluate health of existing trees and establish criteria for the preservation of those to be retained. Description: The proposed development is formed from a modified combination of six previous lots which the Renton Housing Authority purchased between 2011 and 2014 (Figures 1 and 2). Until 2015 five properties had numerous trees present, mainly along the lot lines (see Figure 2). The same canopy configuration goes back at least twenty years as shown in Figure 3. The City of Renton had the existing houses demolished in 2016. Post demolition the tree cover was reduced by roughly sixty percent and the area bulldozed where the houses had been (Figure 4). The RHA is now ready to proceed with developing the site and contracted with Third Place Design. Their proposed site plan is shown in Figure 5. They in turn contacted Superior NW and asked that a formal assessment of the remaining tree be made. The provided plan shows a large evergreen in the center of the development and four others on the west side that currently exist. There are a number of trees shown which will be installed post construction. The following itemized list begins in the northwest corner of the property. It includes the trees currently on the property and those within 10’ of the borders. The numeric designations are reflected in the tree plot shown in Figure 6. The diameters measured were taken at the standard height of 54” above grade (DSH) and the trees were tagged with 1” green circular markers. 1) Douglas Fir (Pseudotsuga menziesii) 26.5” DSH, 25’ tall standing 10’ E of the rough curb line/parking area along Glenwood Avenue and 16’ S of the NW corner marker. The tree has been topped multiple times for power line clearance (Figure 7). It has a full canopy which descends to near the 10’ level. The branches are somewhat overextended and are encroaching on a utility pole in its NW quadrant as shown in Figure 8. It has good new growth and color. Enterprises 13110 NE 177th Place #304 * Woodinville, WA 98072 * Anthony@SuperiorNW.com 206-930-5724 2) Douglas Fir 29” DSH, 70’ tall standing 65’ S of the #1 tree and 8’ E of the rough curb line. It is in fair condition with average new growth and color. There is some deadwood present and it has been pruned multiple times for power line clearance on its west face. Its canopy extends down to the 12’ level. The SW corner of the previous house was less than 15’ away from the base of the tree and the driveway ran fully beneath its canopy as shown in Figure 9. 3) Douglas Fir 24” DSH, 65’ tall standing 36’ S of #2, 8’ E of the rough curb line, and at the north end of a small stand. It is in fair condition and its canopy extends down to the 12’ level although it mainly extends to north and is slightly over extended. There is ivy present in the tree. It has been pruned for wire clearance multiple times. The NW corner of the previous house was around 15’ back from the tree and its driveway ran beneath the tree. 4) Douglas Fir 17.5” DSH, 65’ tall standing 4’ SW of the #3 tree. All its canopy extends to the west except for at the very top. It has somewhat limited new growth and decent color. It has been pruned multiple times for wire clearance. There is ivy present in the tree. 5) Douglas Fir 18” DSH, 60’ tall standing 7’ S of the #4 tree. There is not much canopy on this tree. Most of it is on the east side in a narrow column and then there is a little foliage on the west side starting at the half way point and running nearly in a single branch width. It has noticeably limited new growth and poor color. It has been pruned multiple times for wire clearance. There is ivy present in the tree. A crow’s or hawk’s nest is visible at the very top. 6) Douglas Fir 25” DSH, 65’ tall standing 5’ S of #5, 8’ E of the existing edge of the asphalt for Glenwood Avenue, 24’ N of a set of new water meters, and at the south end of the stand. It has fair color but below average new growth. Its canopy extends down to the 12’ level, almost entirely extends to the south, and is slightly over extended. There is ivy present in the tree. It has been pruned for wire clearance multiple times. The west side of the previous house was close to 20’ back from the tree. 7) Silver Maple (Acer saccharinum) 40” DSH, 55’ tall, 28’ radial spread standing 65’ nearly due east of the #2 fir. The tree is in decline with poor color, stunted new growth, deadwood and die back throughout the canopy, and it is already showing color changes at the extremities. It has a cavity low on the west side with a 7” diameter opening. The previous house was 25’ west of the maple’s base. There had been several smaller trees or quite large shrubs standing between this tree and the #8 fir to its east prior to the demolition event as shown in Figure 2. 8) Douglas Fir 28” DSH, 70’ tall standing 55’ ESE of the #7 maple. The top of the tree was damaged near the 55’mark and it now exhibits multiple stems above that level (see Figure 10). It has average new growth and color. There have been recent breakouts along the SE quadrant probably due to snow loading. 13110 NE 177th Place #304 * Woodinville, WA 98072 * Anthony@SuperiorNW.com 206-930-5724 9) Pacific Dogwood (Cornus nuttalli) 13” DSH, 35’ tall, 9’ spread standing near the center line on the south side of the parcel. The tree is in weak condition with little to no new growth and poor color. An 8” caliper branch cracked out low on the stem and tore into the quick of the tree. Another 6” caliper branch broke out about 18” higher on the stem. The tree is nearly engulfed in English Laurel and holly. 10) Red Alder (Alnus rubra) 36” DSH, 45’ tall, 25’ spread standing 45’ W of the #9 tree at the south end of the parcel. It has advanced decay present along the column and the main scaffolds. The upper half of the canopy is dead. Before the demolition event this tree was surrounded by a dense thicket of other shrubs/small trees. Currently there is nothing around the tree but grass and weeds. Methods: Tree assessment is both an art and a science. To properly perform, an arborist must have an extensive background in biology, tree mechanics, and tree structure that is equal parts academic and field knowledge. It takes years of study to recognize and correctly diagnose the subtle signs trees exhibit before their failure, whether it be partial or total. The process begins with a visual inspection (visual tree assessment, VTA) which is followed up as necessary with soundings, core testing, and/or other detection means. Each tree is examined and evaluated according to several factors including species type, size, vigor, injuries present, root and grade disturbance, deadwood, location and extent of decay, stem taper, exposure, and targets that are at risk. Discussion: Of the ten trees listed only the #3-6 and #8 firs are noted for retention. The other trees currently present are located in areas which will be occupied by structures. The #8 Douglas Fir is shown in Figure 5 with a 20’ radial space (a little more in the NE and SW quadrants) left within which it is to live. Trees can accept some loss of rooting space and still survive but the arboricultural industry accepted threshold is thirty percent. In the given scenario the tree will lose over 50% of its Critical Rooting Area. If the tree is meant to be a long term asset for the campus then this area has to be increased to at least a 23.5’ radial circle. This could be accomplished by making the pathways around the tree fully permeable. Pre-grading and excavation a hard fence will have to be set up around this tree at a distance of 25’ radial feet. The area within the fence should be covered with 6-8” of arbormulch. When it is time to do the improvement work within the fencing (the paths, the parking, the corner of Building B East’s foundation forms) it will have to be overseen by an arborist to document the degree and nature of the impact. The path should be cut and set by hand if in any way possible. All the mulch would be left around the tree once construction is finished. No grass should be planted. The only plants which should be installed would be those commonly found around firs naturally. Salal, evergreen or deciduous huckleberries, rhododendron species, vine maples (native or Japanese varietals), and the like would be acceptable choices. The top of the tree will have to be pruned to create a stronger long term structure. Depending on what the climbing arborist finds it could be that the tree will need ongoing care on a five to seven year basis. The tree would definitely benefit from a deep root feed at the end of the construction process to help it cope with impact stress. 13110 NE 177th Place #304 * Woodinville, WA 98072 * Anthony@SuperiorNW.com 206-930-5724 Based on the historical imagery shown in Figure 2 it is clear that the #3-6 firs incurred root disturbance well within their Critical Root Zones (CRZ). This is the area defined as one radial foot per inch of tree diameter. Trenching type incursion, that is excavation that occurs along only one sector of a tree’s CRZ, can reach significantly into the root growth area without having a detrimental long term effect. What does have to be absolutely protected is a tree’s Structural Root Plate (SRP). This radial area is related to the diameter inches of the tree in question but not quite in such a direct proportion. Figure 11 below illustrates the relationship. Figure 11. Size of the Structural Root Plate in relation to tree stem diameter. Note that the SRP levels off at 10’ for any tree over 24” in diameter (Coder, 1996). In the case of the four firs mentioned above, the excavation of the existing house’s foundation on their east side occurred between 12’ and 17’ from their bases. This would have been well outside any of the fours’ SRP. The proposed walkway to their north is 20’ away; again well outside the SRP for the #3 tree. The new foundation work for Building B West could come as near as 18’ to the base of the trees. This will still not affect the Structural Root Plates of any of the four trees. However, if the City of Renton is going to ask that a sidewalk is installed on the west side of the trees or that any other hardscaping improvement be made which requires a change in grade, these trees will be severely impacted. Installing sidewalk will necessitate the removal of all four due to compromising their structural stability. Any other improvements on the west side will have to be evaluated on a case by case basis. Protection fencing for the stand should be set at the full CRZ distance for the larger two, namely twenty-five radial feet on three sides. On the west it will have to be limited to being at the curb line or just slightly beyond as traffic safety dictates. The area within the protection fencing should be filled with 6-8” of arbormulch and arborist oversite is dictated when work has to occur within the protection zone. 13110 NE 177th Place #304 * Woodinville, WA 98072 * Anthony@SuperiorNW.com 206-930-5724 Waiver of Liability Because the science of tree risk assessment is constantly broadening its understanding, it cannot be said to be an exact science. Every tree is different and performing tree risk assessment is a continual learning process. Many variables beyond the control, or immediate knowledge, of the arborist involved may adversely affect a tree and cause its premature failure. Internal cracks and faults, undetectable root rot, unexposed construction damage, interior decay, and even nutrient deficiencies can be debilitating factors. Changes in circumstance and condition can also lead to a tree’s rapid deterioration and resulting instability. All trees have a risk of failure. As they increase in stature and mass their risk of breakdown also increases, eventual failure is inevitable. While every effort has been taken to provide the most thorough and accurate snapshot of the trees’ health, it is just that, a snapshot, a frozen moment in time. These findings do not guarantee future safety nor are they predictions of imminent events. It is the responsibility of the property owner to adequately care for the tree(s) in question by utilizing the proper professionals and to schedule future assessments in a timely fashion. This report and all attachments, enclosures, and references, are confidential and are for the use of Brent Chastain, Third Place Design, the Renton Housing Authority, and their representatives only. They may not be reproduced, used in any way, or disseminated in any form without the prior consent of the client concerned. Anthony Moran, BS Certified Arborist Qualified Tree Risk Assessor ISA #PN-5847A 13110 NE 177th Place #304 * Woodinville, WA 98072 * Anthony@SuperiorNW.com 206-930-5724 Figure 1. New parcel configuration. Figure 2. Aerial view of the six lots circa 2015 showing prevoius configuration. Note the concentration of trees along the perimeter of the properties. 13110 NE 177th Place #304 * Woodinville, WA 98072 * Anthony@SuperiorNW.com 206-930-5724 Figure 3. Aerial view from 2000 showing nearly the same canopy coverage. Figure 4. Aerial view circa 2017 showing the new parcel post demolition. 13110 NE 177th Place #304 * Woodinville, WA 98072 * Anthony@SuperiorNW.com 206-930-5724 Figure 5. Concept of site redevelopment. 13110 NE 177th Place #304 * Woodinville, WA 98072 * Anthony@SuperiorNW.com 206-930-5724 Figure 6. Current aerial view of subject property. The white numerals correspond to the nomenclature in the description section and show rough placement of the indicated trees. Please refer to the most recent survey for exact locations. 13110 NE 177th Place #304 * Woodinville, WA 98072 * Anthony@SuperiorNW.com 206-930-5724 Figure 7. Photo of the #1 Douglas Fir taken during the July 2019 site visit. Figure 8. Photo of the #1 fir showing encroachment on the utility pole at the NW corner of the parcel. 13110 NE 177th Place #304 * Woodinville, WA 98072 * Anthony@SuperiorNW.com 206-930-5724 Figure 9. Enlargement of the 2015 aerial photo showing driveways running under the #2 and #3 firs. Figure 10. Photo of the top of the #8 fir showing the weak structural formation.