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Home My WebLink AboutRS_TIR_Preliminary_Sierra_Homes_SP_221206_v1.pdf Western Washington Division Eastern Washington Division 165 NE Juniper St., Ste 201, Issaquah, WA 98027 407 Swiftwater Blvd, Cle Elum, WA 98922 Phone: (425) 392-0250 Fax: (425) 391-3055 Phone: (509) 674-7433 Fax: (509) 674-7419 www.EncompassES.net PRELIMINARY TECHNICAL INFORMATION REPORT For 702 Nile Avenue Short Plat 702 Nile Avenue NE Renton, WA 98059 November 2, 2022 Prepared by: Gabe Garner Encompass Engineering Job No. 21706 Prepared For: Dan Finkbeiner Sierra Homes PO Box 3069 Issaquah, WA 98027 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | i Table of Contents I. PROJECT OVERVIEW ................................................................................................................ 1 II. CONDITIONS AND REQUIREMENTS SUMMARY ...................................................................... 6 III. OFFSITE ANALYSIS .................................................................................................................. 10 IV. FLOW CONTROL, LOW IMPACT DEVELOPMENT AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ........................................................................................................................... 17 V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN ..................................................................... 20 VI. SPECIAL REPORTS AND STUDIES ............................................................................................ 20 VII. OTHER PERMITS ..................................................................................................................... 20 VIII. CSWPP ANALYSIS AND DESIGN .............................................................................................. 20 IX. BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION of COVENANT ................... 20 X. OPERATION AND MAINTENANCE MANUAL .......................................................................... 20 List of Figures Figure 1 – TIR Worksheet Figure 2 – Vicinity Map Figure 3 – Soils Map and Legend Figure 4 – Existing Conditions Map Figure 5 – Developed Conditions Map Figure 6 – Drainage Review Flow Chart Figure 7 – Downstream Map Appendix A Geotechnical Evaluation by Cobalt Geosciences dated October 4, 2021 Appendix B Wetland Reconnaissance for 702 Nile Ave, Renton WA by Altmann Oliver Associates, LLC dates December 10, 2021 Appendix C Arborist Report by Layton Tree Consulting, LLC dated October 26, 2022 Appendix D WWHM Output CITY OF RENTON SURFACE WATER DESIGN MANUAL 2022 City of Renton Surface Water Design Manual 6/22/2022 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 __________________ __________________ __________________ REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 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 ______________________  _____________________________________ REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2022 City of Renton Surface Water Design Manual 6/22/2022 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 9 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: ____________ Conveyance System Spill containment located at: _____________________________ Erosion and Sediment Control / Construction Stormwater Pollution Prevention CSWPP/CESCL/ESC Site Supervisor: _____________________ Contact Phone: _________________________ After Hours Phone: _________________________ Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-4 Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Water Quality (include facility summary sheet) Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog or Exemption No. _______________________ On-site BMPs Describe: 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: REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2022 City of Renton Surface Water Design Manual 6/22/2022 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 Description Water Quality Description On-site BMPs Description  Detention  Infiltration  Regional Facility  Shared Facility  Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________  Vegetated Flowpath  Wetpool  Filtration  Oil Control  Spill Control  Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________  Full Dispersion  Full Infiltration  Limited Infiltration  Rain Gardens  Bioretention  Permeable Pavement  Basic Dispersion  Soil Amendment  Perforated Pipe Connection  Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-6 Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS  Drainage Easement  Covenant  Native Growth Protection Covenant  Tract  Other ____________________________  Cast in Place Vault  Retaining Wall  Rockery > 4′ High  Structural on Steep Slope  Other _______________________________ Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate. ____________________________________________________________________________________ Signed/Date 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 1 I. PROJECT OVERVIEW Project: 702 Nile Avenue Short Plat Site Address: 702 Nile Avenue NE, Renton, WA 98059 (See Vicinity Map) Tax Parcel #: 112305-9002 Zoning District: R-4 (Single Family Residential) Site Area: 31,998 SF (0.73 AC) Site Location: The site is in the City of Renton within the SW quarter of Section 11, Township 23 North, Range 5 East, W.M, King County, Washington. The site is located on the south side of NE 7th Place, and on the east side of Nile Ave NE. Figure 2: Vicinity Map Pre-developed Site Conditions: The project site is located in the City of Renton on a 31,998 SF (0.73 AC) lot that is zoned R-4 (single-family residential). The site is accessed from Nile Avenue NE, south of the intersection of Nile Avenue NE and NE 7th Place. The site is bordered to the west by Nile Avenue NE, to the north by NE 7th Place, and to the east and south by single family residences. Additionally, there is a Category III Wetland bordering the southeastern corner of the site. The site is currently developed with a single-family residence accessed from Nile Avenue NE via a gravel driveway on the western side of the site. The property is located within the Lower Cedar River and May Creek drainage basin, within the Cedar River/Lake Washington watershed. Runoff exits the site from two separate natural discharge areas (NDA’s: A & B). NDA A is on the western portion of the site, where runoff sheet flows towards Nile Ave NE and enters the City of Renton storm system. NDA B is located in the southeastern portion of the site where runoff sheet flows offsite towards an adjacent wetland. 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 2 Stormwater is ultimately discharged to Lake Washington, located approximately 3 miles west of the site. See full downstream analysis in Section III of this Technical Information Report (TIR). An Existing Conditions Map is included as Figure 4 at the end of this Section. Critical Areas: Per the Wetland Reconnaissance report by Altmann Oliver Associates, included as Appendix B, a Category III Wetland borders the southeastern corner of the site, but its enhanced buffer does not encroach on the property. No other critical areas have been identified on or adjacent to the site. Soils: Per the US Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS) Web Soil Survey (WSS) information, the entire project site is underlain with Alderwood gravelly sandy loam, 8 to 15 percent slopes (See Figure 3 below). A Geotechnical Evaluation prepared by Cobalt Geosciences (Appendix A) confirms this soil classification across the site, with the discovery of weathered and unweathered glacial till. According to the Geotechnical Evaluation, full infiltration of stormwater is infeasible, however limited infiltration is feasible with the soil classification of “Loamy Sand.” Figure 3: Soil Map and Legend 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 3 Developed Site Conditions The project proposes the development of three (3) single-family lots within the 31,998 SF (0.73 AC) parcel. Lot 1 is 9,214 SF (0.21 Acres) and is proposed along the eastern portion of the site, Lot 2 is 10,149 SF (0.23 AC) and is proposed in the central portion of the site, and Lot 3 is 12,634 SF (0.29 AC) and is proposed along the western portion of the site. All three lots will have driveway access off NE 7th Place. The parcel is zoned R-4, which allows for a maximum building coverage of 35% and a maximum impervious surface coverage of 50%. For the preliminary design of the lots, an impervious building coverage of 1,960 SF, will be used and recorded for each lot. An additional 1,611 SF of on-site driveway, 820 SF of off-site driveway, and 215 SF of walkway are proposed, bringing the total proposed new/replaced impervious for the site to 8,533 SF. Stormwater runoff from the Lots 1-3 will utilize basic dispersion to mitigate stormwater runoff from impervious areas. Please refer to Core Requirement # 9 in Section II and Section IV of this TIR for additional discussion on stormwater BMPs. A Developed Conditions Map is provided as Figure 5 at this end of this Section. NE 7TH PLACENILE AVENUE NE SIERRA HOMESPRELIMINARY UTILITY AND GRADING PLANSIERRA HOMES5 SIERRA HOMES IN COMPLIANCE WITH CITY OF RENTON STANDARDSKnow what'sCallbelow.before you dig.REastern Washington Division407 Swiftwater Blvd. ▪ Cle Elum, WA 98922 ▪ Phone: (509) 674-7433Western Washington Division165 NE Juniper Street, Suite 201 ▪ Issaquah, WA 98027 ▪ Phone: (425) 392-0250NORTH ΔΔSIERRA HOMESFIGURE 4- EXISTING CONDITIONS MAPSIERRA HOMES5 SIERRA HOMES NORTH EXISTING CONDITIONS AREAS IN COMPLIANCE WITH CITY OF RENTON STANDARDSKnow what'sCallbelow.before you dig.REastern Washington Division407 Swiftwater Blvd. ▪ Cle Elum, WA 98922 ▪ Phone: (509) 674-7433Western Washington Division165 NE Juniper Street, Suite 201 ▪ Issaquah, WA 98027 ▪ Phone: (425) 392-0250 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 6 II. CONDITIONS AND REQUIREMENTS SUMMARY The 2022 City of Renton Surface Water Design Manual (RSWDM) was utilized to determine and address all core and special requirements. Based on the criteria specified in Figure 1.1.2.A of the RSWDM, the project falls under Full Drainage Review. Per Section 1.1.2.4 of the RSWDM, the project must meet all nine (9) core and all six (6) special requirements. See Figure 6 below for more information on how the type of drainage review was determined. Figure 6: Drainage Review Flow Chart 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 7 Core Requirements Core Requirement #1: Discharge at the Natural Location The proposed development runoff will follow existing drainage patterns that flow to the southwest into the City of Renton storm system on Nile Avenue NE as well as southeast towards the adjacent offsite wetland. Refer to the Level 1 Downstream Analysis in Section III of this TIR for a complete description of the existing drainage paths. Core Requirement #2: Downstream Analysis A Level 1 Downstream analysis has been completed for the site and no existing or potential problems have been identified. This analysis is included in Section III of this TIR. Core Requirement #3: Flow Control Facilities Based on the City of Renton’s flow control application map, the project site is located within the Duration Flow Control Standard (Forested Conditions). Flow control facilities are required to match the developed peak discharge rates to historical (forested) site conditions over the range of flows extending form 50% of the 2-year up to the full 50-year flow and match the peaks for the 2- and 10-year return periods. The proposed stormwater BMPs result in a 0.0977 CFS increase in the 100-year flow using 1-hour time steps. This is below the allowable threshold of a 0.10 CFS maximum increase per Section 1.2.3.1.A of the RSWDM; therefore, the project meets flow control exemption 2. No formal flow control facilities are proposed at this time; however, flow control BMPs will be implemented as described in Core Requirement #9. Please refer to Section IV of this TIR for additional discussion. Core Requirement #4: Conveyance System Conveyance in compliance with the requirements detailed in Section 1.2.4.1 of the City of Renton 2022 SWDM will be provided with final engineering. Core Requirement #5: Construction Stormwater Pollution Prevention The limits of construction for the project are less than 1 acre. A temporary erosion and sediment control (TESC) plan providing details on best management practices (BMPs) to be implemented during construction is included in the engineering plan set. A Construction Stormwater Pollution Prevention Plan (CSWPPP) will be provided with final engineering. Please refer to Section VIII of this TIR for additional discussion. Core Requirement #6: Maintenance and Operations An Operation and Maintenance Manual will be provided with final engineering. Core Requirement #7: Financial Guarantees and Liability The owner will arrange for any financial guarantees and liabilities required by the permit. Core Requirement #8: Water Quality Facilities In accordance with Section 1.2.8.1.A of the RSWDM, Basic Water Quality Treatment is not required for this project as new plus replaced pollution generating impervious surfaces (PGIS) do not exceed 5,000 SF, meeting exemption 1. This preliminary design accounts for a total of approximately 2,431 SF of driveway area, which is below the 5,000 SF threshold. 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 8 Core Requirement #9: Flow Control BMPs This project is classified as a small subdivision; therefore, it is subject to the Small Subdivision Project BMP Requirements detailed in Section 1.2.9.3.1 in the RSWDM. Although implementation of individual lot BMPs is not required until building permit application, BMPs have been considered for the future improvements on Lots 1-3 based on Section 1.2.9.2 and of the RSWDM. See Section IV of this TIR for further discussion and flow control analysis. Impervious Surface BMPs Full Dispersion: Infeasible for Lots 1-3. An 100-foot native vegetated flowpath segment is not available on these sites. Full Infiltration: Infeasible for Lots 1-3. The Geotechnical Evaluation by Cobalt Geosciences dated October 4, 2021 (Appendix A) states that the site is underlain by weathered and unweathered glacial till that becomes denser with depth. Limited Infiltration: The Geotechnical Evaluation by Cobalt Geosciences dated October 4, 2021 (Appendix A) states that limited infiltration is feasible, with the stipulation that an overflow system is provided. Due to the flat nature of this site, an infiltration trench overflow system is not feasible without connecting into the city storm system. It is our opinion that a basic dispersion trench would be better suited for this site. Rain Gardens/Bioretention: Infeasible for Lots 1 and 2. BMP’s relying on infiltration are not feasible as described above. Permeable Pavement: Infeasible for Lots 1 and 2. BMP’s relying on infiltration are not feasible as described above. Basic Dispersion: Basic Dispersion is proposed for Lots 1-3. All lots will use a 30-foot gravel filled dispersion trench with a 25-foot flow path. These trenches can mitigate up to 2,100 SF of impervious surfaces per sizing in Section C.2.4 of the 2022 RSWDM. For projects that will result in an impervious surface coverage on the buildable portion of the site/lot of less than 45%, on-site BMPs must be applied to 50% of target impervious surfaces. 8,955 SF of impervious area is anticipated to be constructed on-site. This is 8,955/31,998=28.0% of the buildable area on the site. BMPs have been sized to mitigate up to 5,880 SF. This accounts for 5,880/8,955= 65.7% of target impervious surfaces. Therefore, this requirement has been met. Reduced Impervious Surface Credit: To ensure this site meets exemption #2 to Core Requirement #3, a building footprint of 1,960 SF is proposed on each lot. This building footprint has been used in stormwater modeling. 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 9 Special Requirements Special Requirement #1: Other Adopted Area-Specific Requirements Critical Drainage Area – N/A Master Drainage Plan – N/A Basin Plan – N/A Lake management Plan – N/A Shared Facility Drainage Plan – N/A Special Requirement #2: Flood Hazard Area Delineation The limits of this project do not lie within a delineated FEMA 100-year floodplain. Special Requirement #3: Flood Protection Facilities This project does not rely on or propose to modify/construct a new flood protection facility. Special Requirement #4: Source controls The project is a single-family residential development; therefore, this requirement is not applicable. Special Requirement #5: Oil Control This project is not considered high-use in need of oil control. Special Requirement #6: Aquifer Protection Area The site is not located within an Aquifer Protection Area per the Groundwater Protection Areas Map in the RSWDM. 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 10 III. DOWNSTREAM ANALYSIS A Level 1 Downstream analysis has been conducted per the requirements in Section 1.2.2.1 of the RSWDM. Please see Tasks 1 through 4 below for a summary of the results. Task 1: Define and Map the Study Area The area of analysis extends approximately a quarter-mile downstream from the natural discharge areas. This site includes two NDA’s – one being on the western side of the side, and the other being near the southeastern corner of the site. These two NDA’s converge in under a quarter-mile, therefore creating one threshold discharge area. A Downstream Map is provided in Figure 7 below. Figure 7: Downstream Map 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 11 Task 2: Review All Available Information on the Study Area Per King County resources, there have been no significant drainage complaints within a quarter-mile downstream of the site. Task 3: Field Inspect the Study Area A field inspection was performed by Encompass Engineering & Surveying on March 16, 2022. Please refer to Task 4 for a detailed description of the downstream drainage system and analysis. Task 4: Describe the Drainage System Runoff from the site is split into two Natural Discharge Areas (A & B), however these flowpaths converge within a ¼ mile downstream of the site, creating one Threshold Discharge Area for the site. NDA A is located on the western side of the site, where runoff sheet flows off the driveway towards Nile Ave NE (A1). Before reaching Nile Ave, the runoff enters a private area drain that conveys the runoff to the catch basin located on the intersection of NE 7th Place and Nile Ave NE (A2). Once entering the City of Renton public stormwater system, the runoff starts being conveyed parallel with Nile Ave NE to the south. After about 400 FT, the runoff passes by NE 7th Court and continues running to the south (A3). After another 400 FT, the public stormwater system intersects with NE 6th Street (A4/B5) which is also where NDA B converges with NDA A. NDA B is located in the southeastern portion of the site, and runoff generally sheet flows off-site to the south in this area (B1). Once exiting the site, the runoff begins to converge into the wetland located just southeast of the site (B2). The runoff travels through the wetland for approximately 500 FT to the south before entering a catch basin at the southern edge of the wetland (B3). This catch basin conveys the runoff into the City of Renton public stormwater system where it begins to travel southwest along Orcas Ave NE. After 200 FT along Orcas Ave NE, the runoff enters a stormwater detention pond (B4). The outlet is on the western side of the pond, where it then gets conveyed back into the City of Renton public stormwater system and converges with NDA A on Nile Ave NE (A4/B5). After NDA A and NDA B converge, the runoff continues running parallel with Nile Ave NE to the south for around 300 FT before passing by the intersection of NE 5th Place and Nile Ave NE (A5/B6). Approximately 300 FT past NE 5th Place the downstream analysis was completed, just over ¼ mile downstream of the site (A6/B7). Please refer to Figure 7 above, for the approximate location of identified drainage features. Photographs from the site visit are included below. 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 12 Element A1 – Runoff sheet flows towards the western edge of the site Element A2 – Type 2 CB located just northwest of property corner 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 13 Element A3 – Type 1 CB conveying stormwater south along Nile Ave NE Element A4/B5 – Type 1 CBs at NE 6th St. & Nile Ave NE (convergence point) 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 14 Element B1 – Runoff sheet flows southeast through lawn towards property edge Element B2 – Runoff converges into the offsite wetland located just southeast of the site 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 15 Element B3 – Runoff enters CB at southern end of wetland Element B4 – Stormwater detention pond located southwest of the wetland 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 16 Element A5/B6 – Stormwater passes by NE 5th Place/continues flowing south on Nile Ave NE Element A6/B7 – 12” concrete culvert along eastern side of Nile Ave NE (1/4 mile limit) 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 17 IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN Part A: Existing Site Hydrology This property is located within the Lower Cedar River and May Creek drainage basin, within the Cedar River/Lake Washington watershed. The 31,998 SF (0.73 AC) site is currently developed with a single-family residence accessed from Nile Ave NE via a gravel driveway on the western side of the site. Stormwater runoff from the site sheet flows off site from two different NDA’s (NDA A & B). NDA A is on the western portion of the site, where runoff sheet flows towards Nile Ave NE and enters the City of Renton st orm system. NDA B is located in the southeastern portion of the site where runoff sheet flows offsite towards an adjacent wetland. Stormwater is ultimately discharged to Lake Washington, located approximately 3 miles west of the site. See full downstream analysis in Section III of this Technical Information Report (TIR). The Geotechnical Evaluation prepared by Cobalt Geosciences (Appendix A) confirms the NRCS Alderwood gravelly sandy loam soil classification and has determined that the site is only feasible for limited infiltration due to the presence of glacial till. WWHM 2012 was used to model the existing condition using target surfaces per Section 1.2.3 of the 2017 RSWDM. Part B: Developed Site Hydrology The project proposes the development of three (3) single-family lots within the 31,998 SF (0.73 AC) parcel. Lot 1 is 9,214 SF (0.21 Acres) and is proposed along the eastern portion of the site, Lot 2 is 10,149 SF (0.23 AC) and is proposed in the central portion of the site, and Lot 3 is 12,634 SF (0.29 AC) and is proposed along the western portion of the site. All three lots will have driveway access off NE 7th Place. 1,960 SF of building coverage is proposed on each lot. An additional 1,611 SF of on-site driveway, 820 SF of off-site driveway, and 215 SF of walkway are proposed, bringing the total proposed new/replaced impervious for the site to 8,533 SF. Basic Dispersion is proposed for Lots 1-3. All lots will use a 30-foot gravel filled dispersion trench located in the southern portion of the lots with a 25-foot flow path. These trenches can mitigate up to 2,100 SF of impervious surfaces per sizing in Section C.2.4 of the 2022 RSWDM. The remainder of impervious areas will sheet flow towards the existing storm system on NE 7th Pl. All disturbed pervious areas will meet soil amendment requirement as detailed in Section C.2.13 of the RSWDM WWHM 2012 was used to model the proposed condition using target surfaces per Section 1.2.3 of the 2022 RSWDM. No modeling credit was given as the on-site BMPs will be privately maintained. A summary of the existing and developed analyses is provided in the table below: 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 18 Existing Conditions Areas Measured Modeled Condition Area (AC) Area (AC) Lawn: 0.125 Forest: 0.195 Driveway 0.05 Roof 0.02 Total Area: 0.195 0.195 Table 2: Existing Conditions Model Developed Conditions Areas Measured Modeled Condition Area (AC) Area (AC) Roof: 0.13 0.13 Walkway/Patio: 0.005 0.005 Driveway: 0.06 0.06 Total Area: 0.195 0.195 Table 3: Developed Conditions Model Part C: Performance Standards Based on the City of Renton’s flow control application map, the project site is located within the Duration Flow Control Standard (Forested Conditions). Flow control facilities are required to match the developed peak discharge rates to historical (forested) site conditions over the range of flows extending form 50% of the 2-year up to the full 50-year flow and match the peaks for the 2- and 10-year return periods. However, the site meets flow control exemption 2 per Section 1.2.3.1.A of the RSWDM, and flow control facilities are not required. This project is classified as a small subdivision; therefore, it is subject to the Small Subdivision Project BMP Requirements detailed in Section 1.2.9.3.1 in the RSWDM. Although implementation of individual lot BMPs is not required until building permit application, BMPs have been considered for the future improvements on Lots 1 and 2 based on Section 1.2.9.2 and of the RSWDM. The site falls within a Basic Water Quality treatment area in accordance with Section 1.2.8.1.A of the RSWDM, however new plus replaced impervious pollution generating areas within the project site is under 5,000 SF and therefore water quality treatment is not required. Part D: Flow Control System As shown in the table on the following page, the proposed stormwater BMPs result in a 0.0977 CFS increase in the 100-year flow using one-hour timesteps. This is below the allowable threshold of a 0.10 CFS maximum increase per Section 1.2.3.1.B of the RSWDM; therefore, the project meets flow control Exemption 2. No formal flow control facilities are proposed at this time; however, flow control BMPs will be implemented as described in Core Requirement #9 in Section II of this TIR. Please refer to Appendix B for a copy of the full WWHM data output. 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 19 WWHM Output Part E: Water Quality System In accordance with Section 1.2.8.1.A of the RSWDM, Basic Water Quality Treatment is not required for this project as new plus replaced pollution generating impervious surfaces (PGIS) do not exceed 5,000 SF, meeting exemption 1. 2,431 SF of driveway is proposed on this project. 702 Nile Avenue Short Plat Preliminary Technical Information Report 11/2/2022 P a g e | 20 V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN A conveyance system analysis will be provided with final engineering VI. SPECIAL REPORTS AND STUDIES • Geotechnical Evaluation by Cobalt Geosciences dated October 4, 2021 • Wetland Reconnaissance for 702 Nile Ave, Renton WA by Altmann Oliver Associates, LLC dates December 10, 2021 • Arborist Report by Layton Tree Consulting, LLC dated October 26, 2022 VII. OTHER PERMITS • Civil Construction Permit • Final Short Plat • Building Permits • Right-of-Way Use Permit VIII. CSWPP ANALYSIS AND DESIGN A CSWPPP will be provided with final engineering. IX. BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION of COVENANT Bond Quantities, Facility Summary and Declaration of Covenant to be provided with Final Engineering. X. OPERATION AND MAINTENANCE MANUAL An Operation and Maintenance Manual to be provided with Final Engineering. Appendix A Geotechnical Evaluation by Cobalt Geosciences dated October 4, 2021 Cobalt Geosciences, LLC P.O. Box 82243 Kenmore, Washington 98028 www.cobaltgeo.com (206) 331-1097 October 4, 2021 Dan Finkbeiner danfinkbeiner@comcast.net RE: Geotechnical Evaluation Proposed Residential Development 702 Nile Avenue Renton, Washington In accordance with your authorization, Cobalt Geosciences, LLC has prepared this letter to discuss the results of our geotechnical evaluation at the referenced site. The purpose of our evaluation was to provide recommendations for foundation design, grading, and earthwork. Site Description The site is located at 702 Nile Avenue NE in Renton, Washington. The site consists of one irregularly shaped parcel (No. 1123059002) with a total area of 31,996 square feet. The property is developed with a residence and large accessory building and gravel driveway. The remainder of the property is undeveloped and vegetated with grasses, bushes, blackberry vines, and sparse trees. The site slopes gently downward to the south at minimal magnitudes and relief. The site is bordered to the north by NE 7th Place, to the east and south by residential properties, and to the west by Nile Avenue NE. The proposed development includes up to three new residences and driveways. Stormwater will include infiltration or other systems depending on feasibility. Site grading may include cuts and fills of 3 feet or less and foundation loads are expected to be light. We should be provided with the final plans to verify that our recommendations remain valid and do not require updating. Area Geology The Geologic Map of King County, indicates that the site is underlain by Vashon Glacial Till. Vashon Glacial Till includes dense mixtures of silt, sand, clay, and gravel. These deposits become denser with depth and are nearly impermeable. Soil & Groundwater Conditions As part of our evaluation, we excavated one test pit and two hand borings, where accessible. There were numerous utilities that limited access to all areas with an excavator. The explorations encountered approximately 6 inches of topsoil and vegetation underlain by about 1 to 2 feet of medium dense, silty-fine to medium grained sand with debris (Fill). This layer was underlain by 2 to 3 feet of loose to medium dense, silty-fine to medium grained sand with gravel (Weathered Glacial Till). These materials were underlain by dense, silty-fine to medium grained sand with gravel and cobbles (Glacial Till), which continued to the termination depths of the explorations. October 4, 2021 Page 2 of 10 Geotechnical Evaluation www.cobaltgeo.com (206) 331-1097 Groundwater was not encountered in the explorations. The soils became dense and mottled approximately 4.5 to 5.5 feet below grade. Groundwater could be present 4 to 5 feet below grade during the wet season. Water table elevations often fluctuate over time. The groundwater level will depend on a variety of factors that may include seasonal precipitation, irrigation, land use, climatic conditions and soil permeability. Water levels at the time of the field investigation may be different from those encountered during the construction phase of the project. Erosion Hazard The Natural Resources Conservation Services (NRCS) maps for King County indicate that the site is underlain by Alderwood gravelly sandy loam (8 to 15 percent slopes). These soils would have a slight to moderate erosion potential in a disturbed state depending on the slope magnitude. It is our opinion that soil erosion potential at this project site can be reduced through landscaping and surface water runoff control. Typically, erosion of exposed soils will be most noticeable during periods of rainfall and may be controlled by the use of normal temporary erosion control measures, such as silt fences, hay bales, mulching, control ditches and diversion trenches. The typical wet weather season, with regard to site grading, is from October 31st to April 1st. Erosion control measures should be in place before the onset of wet weather. Seismic Hazard The overall subsurface profile corresponds to a Site Class D as defined by Table 1613.5.2 of the International Building Code (IBC). A Site Class D applies to an overall profile consisting of stiff/medium dense soils within the upper 100 feet. We referenced the U.S. Geological Survey (USGS) Earthquake Hazards Program Website to obtain values for SS, S1, Fa, and Fv. The USGS website includes the most updated published data on seismic conditions. The following tables provide seismic parameters from the USGS web site with referenced parameters from ASCE 7-10 and 7-16. Seismic Design Parameters (ASCE 7-10) Site Class Spectral Acceleration at 0.2 sec. (g) Spectral Acceleration at 1.0 sec. (g) Site Coefficients Design Spectral Response Parameters Design PGA Fa Fv SDS SD1 D 1.387 0.521 1.0 1.5 0.925 0.521 0.569 October 4, 2021 Page 3 of 10 Geotechnical Evaluation www.cobaltgeo.com (206) 331-1097 Seismic Design Parameters (ASCE 7-16) Site Class Spectral Acceleration at 0.2 sec. (g) Spectral Acceleration at 1.0 sec. (g) Site Coefficients Design Spectral Response Parameters Design PGA Fa Fv SDS SD1 D 1.387 0.475 1.0 Null 0.925 Null 0.591 Additional seismic considerations include liquefaction potential and amplification of ground motions by soft/loose soil deposits. The liquefaction potential is highest for loose sand with a high groundwater table. The site has a relatively low likelihood of liquefaction. For items listed as “Null” see Section 11.4.8 of the ASCE. Conclusions and Recommendations General The site is underlain by fill and at depth by weathered and unweathered glacial till that becomes denser with depth. The proposed residential structures may be supported on shallow foundation systems bearing on medium dense or firmer native soils or on structural fill placed on the native soils. Local overexcavation or recompaction of loose weathered native soils and fill may be necessary depending on the proposed elevations and locations of the new footings. Infiltration is generally feasible in the weathered glacial till. Any system should have overflow to an suitable discharge point or dispersion location. We should be provided with the plans for review. Site Preparation Trees, shrubs and other vegetation should be removed prior to stripping of surficial organic-rich soil and fill. Based on observations from the site investigation program, it is anticipated that the stripping depth will be 6 to 18 inches. Deeper excavations will be necessary below large trees and in any areas underlain by undocumented fill. The native soils consist of silty-sand with gravel. Most of the native soils may be used as structural fill provided they achieve compaction requirements and are within 3 percent of the optimum moisture. Some of these soils may only be suitable for use as fill during the summer months, as they will be above the optimum moisture levels in their current state. These soils are variably moisture sensitive and may degrade during periods of wet weather and under equipment traffic. Imported structural fill should consist of a sand and gravel mixture with a maximum grain size of 3 inches and less than 5 percent fines (material passing the U.S. Standard No. 200 Sieve). Structural fill should be placed in maximum lift thicknesses of 12 inches and should be compacted to a minimum of 95 percent of the modified proctor maximum dry density, as determined by the ASTM D 1557 test method. October 4, 2021 Page 4 of 10 Geotechnical Evaluation www.cobaltgeo.com (206) 331-1097 Temporary Excavations Based on our understanding of the project, we anticipate that the grading could include local cuts on the order of approximately 3 feet or less for foundation placement. Temporary excavations should be sloped no steeper than 1.5H:1V (Horizontal:Vertical) in loose native soils and fill and 1H:1V in medium dense native soils. If an excavation is subject to heavy vibration or surcharge loads, we recommend that the excavations be sloped no steeper than 2H:1V, where room permits. Temporary cuts should be in accordance with the Washington Administrative Code (WAC) Part N, Excavation, Trenching, and Shoring. Temporary slopes should be visually inspected daily by a qualified person during construction activities and the inspections should be documented in daily reports. The contractor is responsible for maintaining the stability of the temporary cut slopes and reducing slope erosion during construction. Temporary cut slopes should be covered with visqueen to help reduce erosion during wet weather, and the slopes should be closely monitored until the permanent retaining systems or slope configurations are complete. Materials should not be stored or equipment operated within 10 feet of the top of any temporary cut slope. Soil conditions may not be completely known from the geotechnical investigation. In the case of temporary cuts, the existing soil conditions may not be completely revealed until the excavation work exposes the soil. Typically, as excavation work progresses the maximum inclination of temporary slopes will need to be re-evaluated by the geotechnical engineer so that supplemental recommendations can be made. Soil and groundwater conditions can be highly variable. Scheduling for soil work will need to be adjustable, to deal with unanticipated conditions, so that the project can proceed and required deadlines can be met. If any variations or undesirable conditions are encountered during construction, we should be notified so that supplemental recommendations can be made. If room constraints or groundwater conditions do not permit temporary slopes to be cut to the maximum angles allowed by the WAC, temporary shoring systems may be required. The contractor should be responsible for developing temporary shoring systems, if needed. We recommend that Cobalt Geosciences and the project structural engineer review temporary shoring designs prior to installation, to verify the suitability of the proposed systems. Foundation Design The proposed structures may be supported on shallow spread footing foundation systems bearing on undisturbed dense or firmer native soils or on properly compacted structural fill placed on the suitable native soils. Any undocumented fill and/or loose native soils should be removed and replaced with structural fill below foundation elements. Structural fill below footings should consist of clean angular rock 5/8 to 4 inches in size. We should verify soil conditions during foundation excavation work. For shallow foundation support, we recommend widths of at least 16 and 24 inches, respectively, for continuous wall and isolated column footings supporting the proposed structure. Provided that the footings are supported as recommended above, a net allowable bearing pressure of 2,000 pounds per square foot (psf) may be used for design. A 1/3 increase in the above value may be used for short duration loads, such as those imposed by wind and seismic events. Structural fill placed on bearing, native subgrade should be compacted to at least 95 percent of the maximum dry density based on ASTM Test Method D1557. Footing excavations should be inspected to verify that the foundations will bear on suitable material. October 4, 2021 Page 5 of 10 Geotechnical Evaluation www.cobaltgeo.com (206) 331-1097 Exterior footings should have a minimum depth of 18 inches below pad subgrade (soil grade) or adjacent exterior grade, whichever is lower. Interior footings should have a minimum depth of 12 inches below pad subgrade (soil grade) or adjacent exterior grade, whichever is lower. If constructed as recommended, the total foundation settlement is not expected to exceed 1 inch. Differential settlement, along a 25-foot exterior wall footing, or between adjoining column footings, should be less than ½ inch. This translates to an angular distortion of 0.002. Most settlement is expected to occur during construction, as the loads are applied. However, additional post-construction settlement may occur if the foundation soils are flooded or saturated. All footing excavations should be observed by a qualified geotechnical consultant. Resistance to lateral footing displacement can be determined using an allowable friction factor of 0.40 acting between the base of foundations and the supporting subgrades. Lateral resistance for footings can also be developed using an allowable equivalent fluid passive pressure of 225 pounds per cubic foot (pcf) acting against the appropriate vertical footing faces (neglect the upper 12 inches below grade in exterior areas). The frictional and passive resistance of the soil may be combined without reduction in determining the total lateral resistance. Care should be taken to prevent wetting or drying of the bearing materials during construction. Any extremely wet or dry materials, or any loose or disturbed materials at the bottom of the footing excavations, should be removed prior to placing concrete. The potential for wetting or drying of the bearing materials can be reduced by pouring concrete as soon as possible after completing the footing excavation and evaluating the bearing surface by the geotechnical engineer or his representative. Concrete Retaining Walls The following table, titled Wall Design Criteria, presents the recommended soil related design parameters for retaining walls with a level backslope. Contact Cobalt if an alternate retaining wall system is used. This has been included for new cast in place walls, if proposed. Wall Design Criteria “At-rest” Conditions (Lateral Earth Pressure – EFD+) 55 pcf (Equivalent Fluid Density) “Active” Conditions (Lateral Earth Pressure – EFD+) 35 pcf (Equivalent Fluid Density) Seismic Increase for “At-rest” Conditions (Lateral Earth Pressure) 21H* (Uniform Distribution) 1 in 2,500 year event Seismic Increase for “At-rest” Conditions (Lateral Earth Pressure) 14H* (Uniform Distribution) 1 in 500 year event Seismic Increase for “Active” Conditions (Lateral Earth Pressure) 7H* (Uniform Distribution) Passive Earth Pressure on Low Side of Wall (Allowable, includes F.S. = 1.5) Neglect upper 2 feet, then 275 pcf EFD+ Soil-Footing Coefficient of Sliding Friction (Allowable; includes F.S. = 1.5) 0.40 October 4, 2021 Page 6 of 10 Geotechnical Evaluation www.cobaltgeo.com (206) 331-1097 *H is the height of the wall; Increase based on one in 500 year seismic event (10 percent probability of being exceeded in 50 years), +EFD – Equivalent Fluid Density The stated lateral earth pressures do not include the effects of hydrostatic pressure generated by water accumulation behind the retaining walls. Uniform horizontal lateral active and at-rest pressures on the retaining walls from vertical surcharges behind the wall may be calculated using active and at-rest lateral earth pressure coefficients of 0.3 and 0.5, respectively. A soil unit weight of 125 pcf may be used to calculate vertical earth surcharges. To reduce the potential for the buildup of water pressure against the walls, continuous footing drains (with cleanouts) should be provided at the bases of the walls. The footing drains should consist of a minimum 4-inch diameter perforated pipe, sloped to drain, with perforations placed down and enveloped by a minimum 6 inches of pea gravel in all directions. The backfill adjacent to and extending a lateral distance behind the walls at least 2 feet should consist of free-draining granular material. All free draining backfill should contain less than 3 percent fines (passing the U.S. Standard No. 200 Sieve) based upon the fraction passing the U.S. Standard No. 4 Sieve with at least 30 percent of the material being retained on the U.S. Standard No. 4 Sieve. The primary purpose of the free-draining material is the reduction of hydrostatic pressure. Some potential for the moisture to contact the back face of the wall may exist, even with treatment, which may require that more extensive waterproofing be specified for walls, which require interior moisture sensitive finishes. We recommend that the backfill be compacted to at least 90 percent of the maximum dry density based on ASTM Test Method D1557. In place density tests should be performed to verify adequate compaction. Soil compactors place transient surcharges on the backfill. Consequently, only light hand operated equipment is recommended within 3 feet of walls so that excessive stress is not imposed on the walls. Stormwater Management Feasibility The site is underlain by weathered and unweathered glacial till. These soils become denser with depth. The dense till acts as a restrictive layer on which groundwater can seasonally develop. The site is also underlain by areas of fill. The fill and dense till are not suitable for infiltration; however, the weathered till can be suitable for some infiltration. We performed a small scale pilot infiltration test (PIT) in TP-1. The test was performed in general accordance with the Washington State Department of Ecology stormwater manual. The results are as follows: Test Number Test Depth (ft) Measured Infiltration Rate (in/hr) Correction Factors Design Infiltration Rate (in/hr) CFV CFT CFM TP-1 3.0 1.0 0.8 0.5 0.9 0.35 The design infiltration rate was determined by applying correction factors to the measured infiltration rate as prescribed in Volume III, Section 3.3.6 of the DOE. The measured rate must be reduced through appropriate correction factors for site variability (CFV), uncertainty of test method (CFT), and degree of influent control (CFM) to prevent siltation and bio-buildup. October 4, 2021 Page 7 of 10 Geotechnical Evaluation www.cobaltgeo.com (206) 331-1097 Systems should consist of shallow trenches located downgradient of any residences. Any system should penetrate into the weathered till but have at least 12 inches of clearance above mottled soils and dense till. Systems should have adequate overflow for seasonal fluctuations in storm events. We can provide additional input once the site plans have been prepared. We must be on site to verify soil conditions at trench locations. The soils are consistent with the Loamy Sand designation from the King County Surface Water Design Manual We should be provided with final plans for review to determine if the intent of our recommendations has been incorporated or if additional modifications are needed. Slab-on-Grade We recommend that the upper 12 inches of the native soils within slab areas be re-compacted to at least 95 percent of the modified proctor (ASTM D1557 Test Method). Often, a vapor barrier is considered below concrete slab areas. However, the usage of a vapor barrier could result in curling of the concrete slab at joints. Floor covers sensitive to moisture typically requires the usage of a vapor barrier. A materials or structural engineer should be consulted regarding the detailing of the vapor barrier below concrete slabs. Exterior slabs typically do not utilize vapor barriers. The American Concrete Institutes ACI 360R-06 Design of Slabs on Grade and ACI 302.1R-04 Guide for Concrete Floor and Slab Construction are recommended references for vapor barrier selection and floor slab detailing. Slabs on grade may be designed using a coefficient of subgrade reaction of 210 pounds per cubic inch (pci) assuming the slab-on-grade base course is underlain by structural fill placed and compacted as outlined in Section 8.1. A 4- to 6-inch-thick capillary break layer should be placed over the prepared subgrade. This material should consist of pea gravel or 5/8 inch clean angular rock. A perimeter drainage system is recommended unless interior slab areas are elevated a minimum of 12 inches above adjacent exterior grades. If installed, a perimeter drainage system should consist of a 4-inch diameter perforated drain pipe surrounded by a minimum 6 inches of drain rock wrapped in a non-woven geosynthetic filter fabric to reduce migration of soil particles into the drainage system. The perimeter drainage system should discharge by gravity flow to a suitable stormwater system. Exterior grades surrounding buildings should be sloped at a minimum of one percent to facilitate surface water flow away from the building and preferably with a relatively impermeable surface cover immediately adjacent to the building. Erosion and Sediment Control Erosion and sediment control (ESC) is used to reduce the transportation of eroded sediment to wetlands, streams, lakes, drainage systems, and adjacent properties. Erosion and sediment control measures should be implemented, and these measures should be in general accordance with local regulations. At a minimum, the following basic recommendations should be incorporated into the design of the erosion and sediment control features for the site: Schedule the soil, foundation, utility, and other work requiring excavation or the disturbance of the site soils, to take place during the dry season (generally May through September). October 4, 2021 Page 8 of 10 Geotechnical Evaluation www.cobaltgeo.com (206) 331-1097 However, provided precautions are taken using Best Management Practices (BMP’s), grading activities can be completed during the wet season (generally October through April). All site work should be completed and stabilized as quickly as possible. Additional perimeter erosion and sediment control features may be required to reduce the possibility of sediment entering the surface water. This may include additional silt fences, silt fences with a higher Apparent Opening Size (AOS), construction of a berm, or other filtration systems. Any runoff generated by dewatering discharge should be treated through construction of a sediment trap if there is sufficient space. If space is limited other filtration methods will need to be incorporated. Utilities Utility trenches should be excavated according to accepted engineering practices following OSHA (Occupational Safety and Health Administration) standards, by a contractor experienced in such work. The contractor is responsible for the safety of open trenches. Traffic and vibration adjacent to trench walls should be reduced; cyclic wetting and drying of excavation side slopes should be avoided. Depending upon the location and depth of some utility trenches, groundwater flow into open excavations could be experienced, especially during or shortly following periods of precipitation. In general, silty and sandy soils were encountered at shallow depths in the explorations at this site. These soils have low cohesion and density and will have a tendency to cave or slough in excavations. Shoring or sloping back trench sidewalls is required within these soils in excavations greater than 4 feet deep. All utility trench backfill should consist of imported structural fill or suitable on site soils. Utility trench backfill placed in or adjacent to buildings and exterior slabs should be compacted to at least 95 percent of the maximum dry density based on ASTM Test Method D1557. The upper 5 feet of utility trench backfill placed in pavement areas should be compacted to at least 95 percent of the maximum dry density based on ASTM Test Method D1557. Below 5 feet, utility trench backfill in pavement areas should be compacted to at least 90 percent of the maximum dry density based on ASTM Test Method D1557. Pipe bedding should be in accordance with the pipe manufacturer's recommendations. The contractor is responsible for removing all water-sensitive soils from the trenches regardless of the backfill location and compaction requirements. Depending on the depth and location of the proposed utilities, we anticipate the need to re-compact existing fill soils below the utility structures and pipes. The contractor should use appropriate equipment and methods to avoid damage to the utilities and/or structures during fill placement and compaction procedures. CONSTRUCTION FIELD REVIEWS Cobalt Geosciences should be retained to provide part time field review during construction in order to verify that the soil conditions encountered are consistent with our design assumptions and that the intent of our recommendations is being met. This will require field and engineering review to: Monitor and test structural fill placement and soil compaction Observe bearing capacity at foundation locations October 4, 2021 Page 9 of 10 Geotechnical Evaluation www.cobaltgeo.com (206) 331-1097 Observe slab-on-grade preparation Monitor foundation drainage placement Observe excavation stability Geotechnical design services should also be anticipated during the subsequent final design phase to support the structural design and address specific issues arising during this phase. Field and engineering review services will also be required during the construction phase in order to provide a Final Letter for the project. CLOSURE This report was prepared for the exclusive use of Dan Finkbeiner and his appointed consultants. Any use of this report or the material contained herein by third parties, or for other than the intended purpose, should first be approved in writing by Cobalt Geosciences, LLC. The recommendations contained in this report are based on assumed continuity of soils with those of our test holes and assumed structural loads. Cobalt Geosciences should be provided with final architectural and civil drawings when they become available in order that we may review our design recommendations and advise of any revisions, if necessary. Use of this report is subject to the Statement of General Conditions provided in Appendix A. It is the responsibility of Dan Finkbeiner who is identified as “the Client” within the Statement of General Conditions, and its agents to review the conditions and to notify Cobalt Geosciences should any of these not be satisfied. Sincerely, Cobalt Geosciences, LLC 10/4/2021 Phil Haberman, PE, LG, LEG Principal October 4, 2021 Page 10 of 10 Geotechnical Evaluation www.cobaltgeo.com (206) 331-1097 Statement of General Conditions USE OF THIS REPORT: This report has been prepared for the sole benefit of the Client or its agent and may not be used by any third party without the express written consent of Cobalt Geosciences and the Client. Any use which a third party makes of this report is the responsibility of such third party. BASIS OF THE REPORT: The information, opinions, and/or recommendations made in this report are in accordance with Cobalt Geosciences present understanding of the site specific project as described by the Client. The applicability of these is restricted to the site conditions encountered at the time of the investigation or study. If the proposed site specific project differs or is modified from what is described in this report or if the site conditions are altered, this report is no longer valid unless Cobalt Geosciences is requested by the Client to review and revise the report to reflect the differing or modified project specifics and/or the altered site conditions. STANDARD OF CARE: Preparation of this report, and all associated work, was carried out in accordance with the normally accepted standard of care in the state of execution for the specific professional service provided to the Client. No other warranty is made. INTERPRETATION OF SITE CONDITIONS: Soil, rock, or other material descriptions, and statements regarding their condition, made in this report are based on site conditions encountered by Cobalt Geosciences at the time of the work and at the specific testing and/or sampling locations. Classifications and statements of condition have been made in accordance with normally accepted practices which are judgmental in nature; no specific description should be considered exact, but rather reflective of the anticipated material behavior. Extrapolation of in situ conditions can only be made to some limited extent beyond the sampling or test points. The extent depends on variability of the soil, rock and groundwater conditions as influenced by geological processes, construction activity, and site use. VARYING OR UNEXPECTED CONDITIONS: Should any site or subsurface conditions be encountered that are different from those described in this report or encountered at the test locations, Cobalt Geosciences must be notified immediately to assess if the varying or unexpected conditions are substantial and if reassessments of the report conclusions or recommendations are required. Cobalt Geosciences will not be responsible to any party for damages incurred as a result of failing to notify Cobalt Geosciences that differing site or sub-surface conditions are present upon becoming aware of such conditions. PLANNING, DESIGN, OR CONSTRUCTION: Development or design plans and specifications should be reviewed by Cobalt Geosciences, sufficiently ahead of initiating the next project stage (property acquisition, tender, construction, etc), to confirm that this report completely addresses the elaborated project specifics and that the contents of this report have been properly interpreted. Specialty quality assurance services (field observations and testing) during construction are a necessary part of the evaluation of sub-subsurface conditions and site preparation works. Site work relating to the recommendations included in this report should only be carried out in the presence of a qualified geotechnical engineer; Cobalt Geosciences cannot be responsible for site work carried out without being present. Cobalt Geosciences, LLC P.O. Box 82243 Kenmore, WA 98028 (206) 331-1097 www.cobaltgeo.com cobaltgeo@gmail.com SITE PLAN FIGURE 1 N Proposed Three Lot Development 702 Nile Avenue NE Renton, Washington TP-1 Subject Property HB-1 HB-2 Subject Property TP-1 PT Well-graded gravels, gravels, gravel-sand mixtures, little or no fines Poorly graded gravels, gravel-sand mixtures, little or no fines Silty gravels, gravel-sand-silt mixtures Clayey gravels, gravel-sand-clay mixtures Well-graded sands, gravelly sands, little or no fines COARSE GRAINED SOILS (more than 50% retained on No. 200 sieve) Primarily organic matter, dark in color, and organic odor Peat, humus, swamp soils with high organic content (ASTM D4427)HIGHLY ORGANIC SOILS FINE GRAINED SOILS (50% or more passes the No. 200 sieve) MAJOR DIVISIONS SYMBOL TYPICAL DESCRIPTION Gravels (more than 50% of coarse fraction retained on No. 4 sieve) Sands (50% or more of coarse fraction passes the No. 4 sieve) Silts and Clays (liquid limit less than 50) Silts and Clays (liquid limit 50 or more) Organic Inorganic Organic Inorganic Sands with Fines (more than 12% fines) Clean Sands (less than 5% fines) Gravels with Fines (more than 12% fines) Clean Gravels (less than 5% fines) Unified Soil Classification System (USCS) Poorly graded sand, gravelly sands, little or no fines Silty sands, sand-silt mixtures Clayey sands, sand-clay mixtures Inorganic silts of low to medium plasticity, sandy silts, gravelly silts, or clayey silts with slight plasticity Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays Organic silts and organic silty clays of low plasticity Inorganic silts, micaceous or diatomaceous fine sands or silty soils, elastic silt Inorganic clays of medium to high plasticity, sandy fat clay, or gravelly fat clay Organic clays of medium to high plasticity, organic silts Moisture Content Definitions Grain Size Definitions Dry Absence of moisture, dusty, dry to the touch Moist Damp but no visible water Wet Visible free water, from below water table Grain Size Definitions Description Sieve Number and/or Size Fines <#200 (0.08 mm) Sand -Fine -Medium -Coarse Gravel -Fine -Coarse Cobbles Boulders #200 to #40 (0.08 to 0.4 mm) #40 to #10 (0.4 to 2 mm) #10 to #4 (2 to 5 mm) #4 to 3/4 inch (5 to 19 mm) 3/4 to 3 inches (19 to 76 mm) 3 to 12 inches (75 to 305 mm) >12 inches (305 mm) Classification of Soil Constituents MAJOR constituents compose more than 50 percent, by weight, of the soil. Major constituents are capitalized (i.e., SAND). Minor constituents compose 12 to 50 percent of the soil and precede the major constituents (i.e., silty SAND). Minor constituents preceded by “slightly” compose 5 to 12 percent of the soil (i.e., slightly silty SAND). Trace constituents compose 0 to 5 percent of the soil (i.e., slightly silty SAND, trace gravel). Relative Density Consistency (Coarse Grained Soils) (Fine Grained Soils) N, SPT, Relative Blows/FT Density 0 - 4 Very loose 4 - 10 Loose 10 - 30 Medium dense 30 - 50 Dense Over 50 Very dense N, SPT, Relative Blows/FT Consistency Under 2 Very soft 2 - 4 Soft 4 - 8 Medium stiff 8 - 15 Stiff 15 - 30 Very stiff Over 30 Hard Cobalt Geosciences, LLC P.O. Box 82243 Kenmore, WA 98028 (206) 331-1097 www.cobaltgeo.com cobaltgeo@gmail.com Soil Classification Chart Figure C1 Test Pit & Hand Boring Logs Cobalt Geosciences, LLC P.O. Box 82243 Kenmore, WA 98028 (206) 331-1097 www.cobaltgeo.com cobaltgeo@gmail.com Test Pit TP-1 Date: September, 2021 Contractor: Jim Depth: 10’ Elevation: Logged By: PH Checked By: SC Groundwater: None Material Description Moisture Content (%)Plastic Limit Liquid Limit 10 20 30 400 50 1 2 3 4 5 6 DCP Equivalent N-Value 7 8 9 10 SM Dense to very dense, silty-fine to medium grained sand with gravel, mottled yellowish brown to grayish brown, moist. (Glacial Till) End of Test Pit 10’ Topsoil/Grass Proposed Residences 702 Nile Avenue NE Renton, Washington Hand Boring HB-1 Date: September, 2021 Contractor: Cobalt Depth: 6’ Elevation: Logged By: PH Checked By: SC Groundwater: None Material Description Moisture Content (%)Plastic Limit Liquid Limit 10 20 30 400 50 1 2 3 4 5 6 DCP Equivalent N-Value 7 8 9 10 Dense to very dense, silty-fine to medium grained sand with gravel, mottled yellowish brown to grayish brown, moist. (Glacial Till) SM End of Hand Boring 6’ Topsoil/Vegetation SM Loose to medium dense, silty-fine to medium grained sand with gravel, dark yellowish brown, dry to moist. (Weathered Glacial Till) Loose to medium dense, silty-fine to medium grained sand with gravel, dark yellowish brown, dry to moist. (Weathered Glacial Till) SM SM Loose to medium dense, silty-fine to medium grained sand with gravel and debris, dark yellowish brown, dry to moist. (Fill) Loose to medium dense, silty-fine to medium grained sand with gravel and debris, dark yellowish brown, dry to moist. (Fill) SM Test Pit & Hand Boring Logs Cobalt Geosciences, LLC P.O. Box 82243 Kenmore, WA 98028 (206) 331-1097 www.cobaltgeo.com cobaltgeo@gmail.com Proposed Development 16127 Cascadian Way Bothell, Washington Hand Boring HB-2 Date: September, 2021 Contractor: Cobalt Depth: 6’ Elevation: Logged By: PH Checked By: SC Groundwater: None Material Description Moisture Content (%)Plastic Limit Liquid Limit 10 20 30 400 50 1 2 3 4 5 6 DCP Equivalent N-Value 7 8 9 10 Dense to very dense, silty-fine to medium grained sand with gravel, mottled yellowish brown to grayish brown, moist. (Glacial Till) SM End of Hand Boring 6’ Topsoil/Vegetation SM Loose to medium dense, silty-fine to medium grained sand with gravel, dark yellowish brown, dry to moist. (Weathered Glacial Till) Loose to medium dense, silty-fine to medium grained sand with gravel and debris, dark yellowish brown, dry to moist. (Fill) SM Attachment Cobalt Geosciences, LLC PO Box 1792 North Bend, WA 98045 (206) 331-1097 www.cobaltgeo.com phil@cobaltgeo.com Appendix B Wetland Reconnaissance for 702 Nile Ave, Renton WA by Altmann Oliver Associates, LLC dates December 10, 2021 December 10, 2021 AOA-6482 Dan Finkbeiner danfinkbeiner@comcast.net SUBJECT: Wetland Reconnaissance for 702 Nile Ave, Renton, WA Parcel 112305-9002 (PRE21-000056) Dear Dan: On November 16, 2021, I conducted a wetland reconnaissance on and adjacent to the subject property utilizing the methodology outlined in the May 2010 Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region (Version 2.0). The focus of the reconnaissance was to: 1) confirm no wetlands or streams on the subject property, 2) verify that the previously delineated and surveyed boundary of the off-site wetland to the southeast (Wetland A) had not changed, and 3) rate Wetland A per current conditions to determine the current buffer requirement. 1.0 EXISTING ON-SITE CONDITIONS The site is currently developed with a single-family residence/church and associated storage building and mowed yard. No native or hydrophytic plant communities were observed on the property. Borings taken throughout the site revealed high chroma non-hydric soils and there was no evidence of ponding or prolonged soil saturation anywhere on the property. Based on the site review there are no wetlands or streams located on the property. 2.0 WETLAND A Wetland A is a forested Depressional Hydrogeomorphic (HGM) wetland located off-site to the southeast. The wetland was delineated and surveyed as part of the adjacent Weston North residential development. Off-site conditions do not appear to have significantly changed and the previously surveyed wetland boundary appears to remain accurate. Dan Finkbeiner December 10, 2021 Page 2 of 2 Wetland A previously met the criteria for a Category III wetland with 3 Habitat Points and this rating has not changed (Attachment A). Category III wetlands with 3 Habitat Points currently require a standard 75-foot buffer adjacent non low impact land uses per RMC 4-3-050.G.2. As part of the Weston North development, a shed located in the buffer was removed and the degraded buffer enhanced with native plantings and placed within a protective tract (Tract A). The enhanced buffer does not encroach into the subject property (Attachment B). If you have any questions regarding the wetland reconnaissance, please give me a call. Sincerely, ALTMANN OLIVER ASSOCIATES, LLC John Altmann Ecologist Attachments Wetland name or number A Name of wetland (or ID #):Date of site visit:11/16/2021 Rated by Trained by Ecology? Yes No Date of training 03/08 & 03/15 HGM Class used for rating Wetland has multiple HGM classes? Yes No NOTE: Form is not complete with out the figures requested (figures can be combined ). Source of base aerial photo/map OVERALL WETLAND CATEGORY III (based on functions or special characteristics ) 1. Category of wetland based on FUNCTIONS Category I - Total score = 23 - 27 Score for each Category II - Total score = 20 - 22 function based X Category III - Total score = 16 - 19 on three Category IV - Total score = 9 - 15 ratings (order of ratings is not important ) M L 9 = H, H, H H L 8 = H, H, M M L Total 7 = H, H, L 7 = H, M, M 6 = H, M, L 6 = M, M, M 5 = H, L, L 5 = M, M, L 4 = M, L, L 3 = L, L, L 2. Category based on SPECIAL CHARACTERISTICS of wetland X Depressional & Flats RATING SUMMARY – Western Washington List appropriate rating (H, M, L) HydrologicImproving Water Quality MSite Potential Landscape Potential Habitat H FUNCTION Parcel 112305-9002 Altmann King County iMAP Coastal Lagoon Interdunal Value Score Based on Ratings 7 7 3 17 M CHARACTERISTIC Category Estuarine Wetland of High Conservation Value Bog Mature Forest Old Growth Forest None of the above Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1, 2015 1 WSDOT Adapted Form - March 2, 2015 Wetland name or number A Maps and Figures required to answer questions correctly for Western Washington Depressional Wetlands Map of: Figure # Cowardin plant classes Previous Hydroperiods Previous Location of outlet (can be added to map of hydroperiods )Previous Boundary of area within 150 ft of the wetland (can be added to another figure )B Map of the contributing basin Previous 1 km Polygon: Area that extends 1 km from entire wetland edge - including polygons for accessible habitat and undisturbed habitat Screen capture of map of 303(d) listed waters in basin (from Ecology website)C Screen capture of list of TMDLs for WRIA in which unit is found (from web)D Riverine Wetlands Map of: Figure # Cowardin plant classes Hydroperiods Ponded depressions Boundary of area within 150 ft of the wetland (can be added to another figure ) Plant cover of trees, shrubs, and herbaceous plants Width of unit vs. width of stream (can be added to another figure ) Map of the contributing basin 1 km Polygon: Area that extends 1 km from entire wetland edge - including polygons for accessible habitat and undisturbed habitat Screen capture of map of 303(d) listed waters in basin (from Ecology website) Screen capture of list of TMDLs for WRIA in which unit is found (from web) Lake Fringe Wetlands Map of: Figure # Cowardin plant classes Plant cover of trees, shrubs, and herbaceous plants Boundary of area within 150 ft of the wetland (can be added to another figure ) 1 km Polygon: Area that extends 1 km from entire wetland edge - including polygons for accessible habitat and undisturbed habitat Screen capture of map of 303(d) listed waters in basin (from Ecology website) Screen capture of list of TMDLs for WRIA in which unit is found (from web) Slope Wetlands Map of: Figure # Cowardin plant classes Hydroperiods Plant cover of dense trees, shrubs, and herbaceous plants Plant cover of dense, rigid trees, shrubs, and herbaceous plants (can be added to another figure ) Boundary of area within 150 ft of the wetland (can be added to another figure ) 1 km Polygon: Area that extends 1 km from entire wetland edge - including polygons for accessible habitat and undisturbed habitat Screen capture of map of 303(d) listed waters in basin (from Ecology website) Screen capture of list of TMDLs for WRIA in which unit is found (from web) A S 3.1, S 3.2 S 3.3 S 4.1 S 2.1, S 5.1 To answer questions: H 1.1, H 1.4 H 1.2 S 1.3 H 2.1, H 2.2, H 2.3 L 3.1, L 3.2 L 3.3 H 2.1, H 2.2, H 2.3 R 3.1 R 3.2, R 3.3 To answer questions: L 1.1, L 4.1, H 1.1, H 1.4 H 1.2 R 1.1 R 2.4 R 1.2, R 4.2 R 4.1 R 2.2, R 2.3, R 5.2 H 2.1, H 2.2, H 2.3 L 1.2 L 2.2 D 1.1, D 4.1 D 2.2, D 5.2 D 4.3, D 5.3 H 2.1, H 2.2, H 2.3 D 3.1, D 3.2 D 3.3 To answer questions: H 1.1, H 1.4 To answer questions: D 1.3, H 1.1, H 1.4 D 1.4, H 1.2 Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1, 2015 2 WSDOT Adapted Form - March 2, 2015 Wetland name or number A For questions 1 -7, the criteria described must apply to the entire unit being rated. 1. Are the water levels in the entire unit usually controlled by tides except during floods? NO - go to 2 YES - the wetland class is Tidal Fringe - go to 1.1 1.1 Is the salinity of the water during periods of annual low flow below 0.5 ppt (parts per thousand)? NO - Saltwater Tidal Fringe (Estuarine)YES - Freshwater Tidal Fringe NO - go to 3 YES - The wetland class is Flats If your wetland can be classified as a Flats wetland, use the form for Depressional wetlands. 3. Does the entire wetland unit meet all of the following criteria? NO - go to 4 YES - The wetland class is Lake Fringe (Lacustrine Fringe) 4. Does the entire wetland unit meet all of the following criteria? The wetland is on a slope (slope can be very gradual ), The water leaves the wetland without being impounded. NO - go to 5 YES - The wetland class is Slope 5. Does the entire wetland unit meet all of the following criteria? The overbank flooding occurs at least once every 2 years. NO - go to 6 YES - The wetland class is Riverine NOTE: The Riverine unit can contain depressions that are filled with water when the river is not flooding. If your wetland can be classified as a Freshwater Tidal Fringe use the forms for Riverine wetlands. If it is Saltwater Tidal Fringe it is an Estuarine wetland and is not scored. This method cannot be used to score functions for estuarine wetlands. The vegetated part of the wetland is on the shores of a body of permanent open water (without any plants on the surface at any time of the year) at least 20 ac (8 ha) in size; The water flows through the wetland in one direction (unidirectional) and usually comes from seeps. It may flow subsurface, as sheetflow, or in a swale without distinct banks. NOTE: Surface water does not pond in these type of wetlands except occasionally in very small and shallow depressions or behind hummocks (depressions are usually <3 ft diameter and less than 1 ft deep). The unit is in a valley, or stream channel, where it gets inundated by overbank flooding from that stream or river, 2. The entire wetland unit is flat and precipitation is the only source (>90%) of water to it. Groundwater and surface water runoff are NOT sources of water to the unit. HGM Classification of Wetland in Western Washington If hydrologic criteria listed in each question do not apply to the entire unit being rated, you probably have a unit with multiple HGM classes. In this case, identify which hydrologic criteria in questions 1 - 7 apply, and go to Question 8. At least 30% of the open water area is deeper than 6.6 ft (2 m). Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1, 2015 3 WSDOT Adapted Form - March 2, 2015 Wetland name or number A NO - go to 7 YES - The wetland class is Depressional NO - go to 8 YES - The wetland class is Depressional NOTES and FIELD OBSERVATIONS: Salt Water Tidal Fringe and any other class of freshwater wetland HGM class to use in rating Riverine Depressional Lake Fringe If you are still unable to determine which of the above criteria apply to your wetland, or if you have more than 2 HGM classes within a wetland boundary, classify the wetland as Depressional for the rating. Riverine Treat as ESTUARINE Slope + Lake Fringe Depressional + Riverine along stream within boundary of depression Depressional + Lake Fringe Riverine + Lake Fringe NOTE: Use this table only if the class that is recommended in the second column represents 10% or more of the total area of the wetland unit being rated. If the area of the HGM class listed in column 2 is less than 10% of the unit; classify the wetland using the class that represents more than 90% of the total area. HGM classes within the wetland unit being rated Slope + Riverine Slope + Depressional Depressional Depressional 7. Is the entire wetland unit located in a very flat area with no obvious depression and no overbank flooding? The unit does not pond surface water more than a few inches. The unit seems to be maintained by high groundwater in the area. The wetland may be ditched, but has no obvious natural outlet. 8. Your wetland unit seems to be difficult to classify and probably contains several different HGM classes. For example, seeps at the base of a slope may grade into a riverine floodplain, or a small stream within a Depressional wetland has a zone of flooding along its sides. GO BACK AND IDENTIFY WHICH OF THE HYDROLOGIC REGIMES DESCRIBED IN QUESTIONS 1-7 APPLY TO DIFFERENT AREAS IN THE UNIT (make a rough sketch to help you decide). Use the following table to identify the appropriate class to use for the rating system if you have several HGM classes present within the wetland unit being scored. 6. Is the entire wetland unit in a topographic depression in which water ponds, or is saturated to the surface, at some time during the year? This means that any outlet, if present, is higher than the interior of the wetland. Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1, 2015 4 WSDOT Adapted Form - March 2, 2015 Wetland name or number A D 1.1. Characteristics of surface water outflows from the wetland: points = 3 points = 2 points = 1 points = 1 Yes = 4 No = 0 Wetland has persistent, ungrazed, plants > 95% of area points = 5 Wetland has persistent, ungrazed, plants > ½ of area points = 3 Wetland has persistent, ungrazed plants > 1/10 of area points = 1 Wetland has persistent, ungrazed plants < 1/10 of area points = 0 D 1.4. Characteristics of seasonal ponding or inundation: This is the area that is ponded for at least 2 months. See description in manual. Area seasonally ponded is > ½ total area of wetland points = 4 Area seasonally ponded is > ¼ total area of wetland points = 2 Area seasonally ponded is < ¼ total area of wetland points = 0 Total for D 1 Add the points in the boxes above 9 Rating of Site Potential If score is: 12 - 16 = H 6 - 11 = M 0 - 5 = L Record the rating on the first page D 2.1. Does the wetland unit receive stormwater discharges?Yes = 1 No = 0 1 Yes = 1 No = 0 D 2.3. Are there septic systems within 250 ft of the wetland?Yes = 1 No = 0 1 Source Yes = 1 No = 0 Total for D 2 Add the points in the boxes above 3 Rating of Landscape Potential If score is: 3 or 4 = H 1 or 2 = M 0 = L Record the rating on the first page Yes = 1 No = 0 Yes = 1 No = 0 Yes = 2 No = 0 Total for D 3 Add the points in the boxes above 1 Rating of Value If score is: 2 - 4 = H 1 = M 0 = L Record the rating on the first page 1 0 Water Quality Functions - Indicators that the site functions to improve water quality D 1.0. Does the site have the potential to improve water quality? 2 Wetland has an unconstricted, or slightly constricted, surface outlet that is permanently flowing Wetland has an intermittently flowing stream or ditch, OR highly constricted permanently flowing outlet. Wetland is a depression or flat depression (QUESTION 7 on key) with no surface water leaving it (no outlet). Wetland is a flat depression (QUESTION 7 on key), whose outlet is a permanently flowing ditch. 2 D 2.0. Does the landscape have the potential to support the water quality function of the site? DEPRESSIONAL AND FLATS WETLANDS D 3.3. Has the site been identified in a watershed or local plan as important for maintaining water quality (answer YES if there is a TMDL for the basin in which the unit is found )? D 1.2. The soil 2 in below the surface (or duff layer) is true clay or true organic (use NRCS definitions ). D 1.3. Characteristics and distribution of persistent plants (Emergent, Scrub-shrub, and/or Forested Cowardin classes): D 2.4. Are there other sources of pollutants coming into the wetland that are not listed in questions D 2.1 - D 2.3? D 3.1. Does the wetland discharge directly (i.e., within 1 mi) to a stream, river, lake, or marine water that is on the 303(d) list? D 2.2. Is > 10% of the area within 150 ft of the wetland in land uses that generate pollutants? D 3.2. Is the wetland in a basin or sub-basin where an aquatic resource is on the 303(d) list? D 3.0. Is the water quality improvement provided by the site valuable to society? 1 0 0 0 5 Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1, 2015 5 WSDOT Adapted Form - March 2, 2015 Wetland name or number A D 4.1. Characteristics of surface water outflows from the wetland: points = 4 points = 2 points = 1 points = 0 Marks of ponding are 3 ft or more above the surface or bottom of outlet points = 7 Marks of ponding between 2 ft to < 3 ft from surface or bottom of outlet points = 5 Marks are at least 0.5 ft to < 2 ft from surface or bottom of outlet points = 3 The wetland is a “headwater” wetland points = 3 Wetland is flat but has small depressions on the surface that trap water points = 1 Marks of ponding less than 0.5 ft (6 in)points = 0 The area of the basin is less than 10 times the area of the unit points = 5 The area of the basin is 10 to 100 times the area of the unit points = 3 The area of the basin is more than 100 times the area of the unit points = 0 Entire wetland is in the Flats class points = 5 Total for D 4 Add the points in the boxes above 8 Rating of Site Potential If score is: 12 - 16 = H 6 - 11 = M 0 - 5 = L Record the rating on the first page D 5.1. Does the wetland unit receive stormwater discharges?Yes = 1 No = 0 1 D 5.2. Is > 10% of the area within 150 ft of the wetland in land uses that generate excess runoff? Yes = 1 No = 0 Yes = 1 No = 0 Total for D 5 Add the points in the boxes above 3 Rating of Landscape Potential If score is: 3 = H 1 or 2 = M 0 = L Record the rating on the first page points = 2 points = 1 Flooding from groundwater is an issue in the sub-basin.points = 1 points = 0 There are no problems with flooding downstream of the wetland.points = 0 Yes = 2 No = 0 Total for D 6 Add the points in the boxes above 1 Rating of Value If score is: 2 - 4 = H 1 = M 0 = L Record the rating on the first page DEPRESSIONAL AND FLATS WETLANDS D 6.0. Are the hydrologic functions provided by the site valuable to society? The wetland captures surface water that would otherwise flow down-gradient into areas where flooding has damaged human or natural resources (e.g., houses or salmon redds): Flooding occurs in a sub-basin that is immediately down- gradient of unit. Surface flooding problems are in a sub-basin farther down- gradient. Hydrologic Functions - Indicators that the site functions to reduce flooding and stream degradation D 4.0. Does the site have the potential to reduce flooding and erosion? 2 Wetland is a depression or flat depression with no surface water leaving it (no outlet) Wetland has an unconstricted, or slightly constricted, surface outlet that is permanently flowing Wetland has an intermittently flowing stream or ditch, OR highly constricted permanently flowing outlet Wetland is a flat depression (QUESTION 7 on key), whose outlet is a permanently flowing ditch 3 D 5.0. Does the landscape have the potential to support hydrologic function of the site? 1 1 D 5.3. Is more than 25% of the contributing basin of the wetland covered with intensive human land uses (residential at >1 residence/ac, urban, commercial, agriculture, etc.)? The existing or potential outflow from the wetland is so constrained by human or natural conditions that the water stored by the wetland cannot reach areas that flood. Explain why 1 0 3 D 4.2. Depth of storage during wet periods: Estimate the height of ponding above the bottom of the outlet. For wetlands with no outlet, measure from the surface of permanent water or if dry, the deepest part. D 4.3. Contribution of the wetland to storage in the watershed: Estimate the ratio of the area of upstream basin contributing surface water to the wetland to the area of the wetland unit itself. D 6.1. The unit is in a landscape that has flooding problems. Choose the description that best matches conditions around the wetland unit being rated. Do not add points. Choose the highest score if more than one condition is met. D 6.2. Has the site been identified as important for flood storage or flood conveyance in a regional flood control plan? Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1, 2015 6 WSDOT Adapted Form - March 2, 2015 Wetland name or number A HABITAT FUNCTIONS - Indicators that site functions to provide important habitat H 1.0. Does the site have the potential to provide habitat? Aquatic bed 4 structures or more: points = 4 Emergent 3 structures: points = 2 Scrub-shrub (areas where shrubs have > 30% cover)2 structures: points - 1 Forested (areas where trees have > 30% cover)1 structure: points = 0 If the unit has a Forested class, check if : H 1.2. Hydroperiods Permanently flooded or inundated 4 or more types present: points = 3 Seasonally flooded or inundated 3 types present: points = 2 Occasionally flooded or inundated 2 types present: points = 1 Saturated only 1 types present: points = 0 Permanently flowing stream or river in, or adjacent to, the wetland Seasonally flowing stream in, or adjacent to, the wetland Lake Fringe wetland 2 points Freshwater tidal wetland 2 points H 1.3. Richness of plant species If you counted:> 19 species points = 2 5 - 19 species points = 1 < 5 species points = 0 H 1.4. Interspersion of habitats These questions apply to wetlands of all HGM classes. The Forested class has 3 out of 5 strata (canopy, sub-canopy, shrubs, herbaceous, moss/ground-cover) that each cover 20% within the Forested polygon 1 H 1.1. Structure of plant community: Indicators are Cowardin classes and strata within the Forested class. Check the Cowardin plant classes in the wetland. Up to 10 patches may be combined for each class to meet the threshold of ¼ ac or more than 10% of the unit if it is smaller than 2.5 ac. Add the number of structures checked. None = 0 points Low = 1 point Moderate = 2 points All three diagrams in this row are HIGH = 3 points 0 Check the types of water regimes (hydroperiods) present within the wetland. The water regime has to cover more than 10% of the wetland or ¼ ac to count (see text for descriptions of hydroperiods ). 0 Count the number of plant species in the wetland that cover at least 10 ft2.Different patches of the same species can be combined to meet the size threshold and you do not have to name the species. Do not include Eurasian milfoil, reed canarygrass, purple loosestrife, Canadian thistle 1 Decide from the diagrams below whether interspersion among Cowardin plants classes (described in H 1.1), or the classes and unvegetated areas (can include open water or mudflats) is high, moderate, low, or none. If you have four or more plant classes or three classes and open water, the rating is always high. Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1, 2015 7 WSDOT Adapted Form - March 2, 2015 Wetland name or number A H 1.5. Special habitat features: Large, downed, woody debris within the wetland (> 4 in diameter and 6 ft long) Standing snags (dbh > 4 in) within the wetland Total for H 1 Add the points in the boxes above 5 Rating of Site Potential If Score is: 15 - 18 = H 7 - 14 = M 0 - 6 = L Record the rating on the first page H 2.0. Does the landscape have the potential to support the habitat function of the site? H 2.1 Accessible habitat (include only habitat that directly abuts wetland unit ). Calculate: 0.9 % undisturbed habitat + (0 % moderate & low intensity land uses / 2 ) = 0.9% If total accessible habitat is: > 1/3 (33.3%) of 1 km Polygon points = 3 20 - 33% of 1 km Polygon points = 2 10 - 19% of 1 km Polygon points = 1 < 10 % of 1 km Polygon points = 0 H 2.2. Undisturbed habitat in 1 km Polygon around the wetland. Calculate: 14.4 % undisturbed habitat + (11.2 % moderate & low intensity land uses / 2 ) = 20% Undisturbed habitat > 50% of Polygon points = 3 Undisturbed habitat 10 - 50% and in 1-3 patches points = 2 Undisturbed habitat 10 - 50% and > 3 patches points = 1 Undisturbed habitat < 10% of 1 km Polygon points = 0 H 2.3 Land use intensity in 1 km Polygon: If > 50% of 1 km Polygon is high intensity land use points = (-2) ≤ 50% of 1km Polygon is high intensity points = 0 Total for H 2 Add the points in the boxes above -1 Rating of Landscape Potential If Score is: 4 - 6 = H 1 - 3 = M < 1 = L Record the rating on the first page Site meets ANY of the following criteria:points = 2 It has 3 or more priority habitats within 100 m (see next page) It is mapped as a location for an individual WDFW priority species Site has 1 or 2 priority habitats (listed on next page) with in 100m points = 1 Site does not meet any of the criteria above points = 0 Rating of Value If Score is: 2 = H 1 = M 0 = L Record the rating on the first page 0 1 -2 H 3.0. Is the habitat provided by the site valuable to society? H 3.1. Does the site provide habitat for species valued in laws, regulations, or policies? Choose only the highest score that applies to the wetland being rated . It provides habitat for Threatened or Endangered species (any plant or animal on the state or federal lists) It is a Wetland of High Conservation Value as determined by the Department of Natural Resources 0 Invasive plants cover less than 25% of the wetland area in every stratum of plants (see H 1.1 for list of strata ) Undercut banks are present for at least 6.6 ft (2 m) and/or overhanging plants extends at least 3.3 ft (1 m) over a stream (or ditch) in, or contiguous with the wetland, for at least 33 ft (10 m) Stable steep banks of fine material that might be used by beaver or muskrat for denning (> 30 degree slope) OR signs of recent beaver activity are present (cut shrubs or trees that have not yet weathered where wood is exposed ) At least ¼ ac of thin-stemmed persistent plants or woody branches are present in areas that are permanently or seasonally inundated (structures for egg-laying by amphibians ) 3 Check the habitat features that are present in the wetland. The number of checks is the number of points. It has been categorized as an important habitat site in a local or regional comprehensive plan, in a Shoreline Master Plan, or in a watershed plan Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1, 2015 8 WSDOT Adapted Form - March 2, 2015 Wetland name or number A Aspen Stands: Pure or mixed stands of aspen greater than 1 ac (0.4 ha). Herbaceous Balds: Variable size patches of grass and forbs on shallow soils over bedrock. Cliffs: Greater than 25 ft (7.6 m) high and occurring below 5000 ft elevation. http://wdfw.wa.gov/publications/00165/wdfw00165.pdf or access the list from here: http://wdfw.wa.gov/conservation/phs/list/ Caves: A naturally occurring cavity, recess, void, or system of interconnected passages under the earth in soils, rock, ice, or other geological formations and is large enough to contain a human. Note: All vegetated wetlands are by definition a priority habitat but are not included in this list because they are addressed elsewhere. WDFW Priority Habitats Count how many of the following priority habitats are within 330 ft (100 m) of the wetland unit: NOTE : This question is independent of the land use between the wetland unit and the priority habitat. Biodiversity Areas and Corridors: Areas of habitat that are relatively important to various species of native fish and wildlife (full descriptions in WDFW PHS report ). Old-growth/Mature forests: Old-growth west of Cascade crest – Stands of at least 2 tree species, forming a multi-layered canopy with occasional small openings; with at least 8 trees/ac (20 trees/ha) > 32 in (81 cm) dbh or > 200 years of age. Mature forests – Stands with average diameters exceeding 21 in (53 cm) dbh; crown cover may be less than 100%; decay, decadence, numbers of snags, and quantity of large downed material is generally less than that found in old-growth; 80-200 years old west of the Cascade crest. Priority habitats listed by WDFW (see complete descriptions of WDFW priority habitats, and the counties in which they can be found, in: Washington Department of Fish and Wildlife. 2008. Priority Habitat and Species List. Olympia, Washington. 177 pp. Oregon White Oak: Woodland stands of pure oak or oak/conifer associations where canopy coverage of the oak component is important (full descriptions in WDFW PHS report p. 158 – see web link above ). Riparian: The area adjacent to aquatic systems with flowing water that contains elements of both aquatic and terrestrial ecosystems which mutually influence each other. Westside Prairies: Herbaceous, non-forested plant communities that can either take the form of a dry prairie or a wet prairie (full descriptions in WDFW PHS report p. 161 – see web link above ). Instream: The combination of physical, biological, and chemical processes and conditions that interact to provide functional life history requirements for instream fish and wildlife resources. Nearshore: Relatively undisturbed nearshore habitats. These include Coastal Nearshore, Open Coast Nearshore, and Puget Sound Nearshore. (full descriptions of habitats and the definition of relatively undisturbed are in WDFW report – see web link on previous page ). Snags and Logs: Trees are considered snags if they are dead or dying and exhibit sufficient decay characteristics to enable cavity excavation/use by wildlife. Priority snags have a diameter at breast height of > 20 in (51 cm) in western Washington and are > 6.5 ft (2 m) in height. Priority logs are > 12 in (30 cm) in diameter at the largest end, and > 20 ft (6 m) long. Talus: Homogenous areas of rock rubble ranging in average size 0.5 - 6.5 ft (0.15 - 2.0 m), composed of basalt, andesite, and/or sedimentary rock, including riprap slides and mine tailings. May be associated with cliffs. Wetland Rating System for Western WA: 2014 Update Rating Form - Effective January 1, 2015 9 WSDOT Adapted Form - March 2, 2015 EagleView Technologies, Inc. 0 1,000 2,000 3,000 4,000500 US Feet Subject Property Parcel: 112305-9002 Approximate Wetland A Rating Unit 1 Km Habitat Classification Polygon Accessible Relatively Undisturbed Habitat 0.9%% Accessible Low_Moderate Intensity Habitat 0.0% Relativley Undisturbed Habitat 13.5% Low_Moderate Intensity Habitat 11.2% High Intensity Habitat 74.4% Figure A AOA - 6482City of Renton Parcel 112305-9002 King County, EagleView Technologies, Inc. 0 125 250 375 50062.5 US Feet Subject Property Parcel: 112305-9002 Approximate Wetland A Rating Unit 150' Pollution Assessment Polygon Pollution Generating Surfaces 77.3% Figure B AOA - 6482City of Renton Parcel 112305-9002 Figure C Sources: Esri, HERE, Garmin, Intermap, increment P Corp., GEBCO, USGS,FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, EsriJapan, METI, Esri China (Hong Kong), (c) OpenStreetMap contributors, and December 10, 2021 0 0.5 10.25Miles K Assessed Water/SedimentWater Category 5 - 303d Category 4C Category 4B Category 4A Category 2 Category 1 Sediment Category 5 - 303d Category 4C Category 4B Category 4A Category 2 Category 1 Figure D Sources: Esri, HERE, Garmin, Intermap, increment P Corp., GEBCO, USGS,FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, EsriJapan, METI, Esri China (Hong Kong), (c) OpenStreetMap contributors, and December 10, 2021 0 0.25 0.50.125Miles K Assessed Water/SedimentWater Category 5 - 303d Category 4C Category 4B Category 4A Category 2 Category 1 Sediment Category 5 - 303d Category 4C Category 4B Category 4A Category 2 Category 1 WQ Improvement ProjectsApproved In Development Appendix C Arborist Report by Layton Tree Consulting, LLC dated October 26, 2022 LAYTON TREE CONSULTING, LLC It’s all about trees…… PO BOX 572, SNOHOMISH, WA 98291-0572 * 425-220-5711 * bob@laytontreeconsulting.com ARBORIST REPORT 702 Nile Avenue NE Renton, WA Report Prepared by: Bob Layton Registered Consulting Arborist #670 Certified Arborist #PN-2714A April 14, 2022 Updated October 26, 2022 Arborist Report – 702 Nile Ave NE Page 2 Layton Tree Consulting LLC April 14, 2022 Updated October 26, 2022 Table of Contents Assignment.................................................................................................................................................... 3 Description .................................................................................................................................................... 3 Methodology ................................................................................................................................................. 3 Judging Condition...................................................................................................................................... 4 Observations ................................................................................................................................................. 4 Discussion/Recommendations ...................................................................................................................... 4 Tree Protection Recommendations .............................................................................................................. 5 Tree Protection Measures ............................................................................................................................ 5 Tree Density-Tree Replacement - Updated .................................................................................................. 6 Arborist Disclosure Statement ...................................................................................................................... 8 Attachments Photos, pages 9 - 12 Tree Summary Table Tree Plan Map City of Renton – Approved Tree List Arborist Report – 702 Nile Ave NE Page 3 Layton Tree Consulting LLC April 14, 2022 Updated October 26, 2022 Assignment Layton Tree Consulting, LLC was asked to compile an Arborist Report for one parcel in Renton. The subject property is located at 702 Nile Avenue NE. The purpose of the report is to satisfy City requirements regarding tree retention regulations associated with the proposed redevelopment of the property. My assignment is to prepare a written report on present tree conditions, and to provide appropriate recommendations for the protection of retained or protected trees during development. This report covers all of the criteria set forth under the City of Renton’s tree regulations, Municipal Code Section 4-4-130 - Tree Retention and Land Clearing Regulations. The property is zoned R4, requiring the retention of 30% of the existing significant trees. Date of Field Examination: April 6, 2022 Description There are few trees on the subject property. The site is mostly open and covered in lawn and gravel. The adjacent rights-of-way of NE 7th Place and Nile Avenue NE have been recently landscaped. Several trees, shrubs and ground covers have been planted in recent years. Five significant trees were identified on the property. A significant tree is any tree with a caliper of at least 6-inches or alder or cottonwood tree at least 8-inches. The subject trees are all fruit trees. Trees have been previously marked with a numbered aluminum tag attached to the lower trunk. These same tag numbers are used for this report. Tree numbers correspond with the numbers on the attached Tree Summary Table and Tree Plan Map. An additional five off-site trees were also assessed. These are all mature apple trees located within a proximity of the south property line. They are located within an access tract. Methodology Each tree in this report was visited. Tree diameters were measured by tape. The tree heights were measured using a Spiegel Relaskop. Each tree was visually examined for defects and vigor. The tree assessment procedure involves the examination of many factors: • The crown or canopy of the tree is examined for current vigor/health by examining the foliage for appropriate color and density, the vegetative buds for color and size, and the branches for structural form and annual shoot growth; and the overall presence of limb dieback and/or any disease issues. • The trunk or main stem of the tree is inspected for decay, which includes cavities, wounds, fruiting bodies of decay (conks or mushrooms), seams, insect pests, bleeding or exudation of sap, callus development, broken or dead tops, structural defects and unnatural leans. Structural defects can include but are not limited to excessive or unnatural leans, crooks, forks with V-shaped crotches, multiple attachments. Arborist Report – 702 Nile Ave NE Page 4 Layton Tree Consulting LLC April 14, 2022 Updated October 26, 2022 • The root collar and exposed surface roots are inspected for the presence of decay, insect damage, as well as if they have been injured or wounded, undermined or exposed, or the original grade has been altered. Judging Condition The three condition categories are described as follows: Good – free of significant structural defects, no disease concerns, minor pest issues, no significant root issues, good structure/form with uniform crown or canopy, foliage of normal color and density, average or normal vigor, will be wind firm if isolated or left as part of a grouping or grove of trees, suitable for its location Fair – minor to moderate structural defects not expected to contribute to a failure in near future, no disease concerns, moderate pest issues, no significant root issues, asymmetric or unbalanced crown or canopy, average or normal vigor, foliage of normal color, moderate foliage density, will be wind firm if left as part of a grouping or grove of trees, cannot be isolated, suitable for its location Poor – major structural defects expected to cause fail in near future, disease or significant pest concerns, decline due to old age, significant root issues, asymmetric or unbalanced crown or canopy, sparse or abnormally small foliage, poor vigor, not suitable for its location The attached Tree Summary Table provides specific information on tree sizes and dripline measurements. Observations The subject trees are all fruit trees. The majority (#947, #949 and #952) are mature apple trees. Most have developed significant trunk decay which is common for the species. Vigor is good. Trees have been well-maintained (pruned) in the past. These are in ‘fair’ condition. Tree #1 is a semi-mature pear. It has been recently heavily pruned/cut back. See pictures below. It has developed typical form and is of fairly good vigor. Condition is ‘fair’. Tree #2 is a young cherry fruit tree variety. It has developed decent structural form and is of good vigor. Condition is ‘fair’. Off-site/Neighboring Trees These are all mature apple trees. #951 and #953 have extensive decay within the trunks. The remainder have developed moderate internal decay. Vigor remains good. These are all low risk due to size. Continued retention is feasible. Tree #953 is a boundary line tree. Discussion/Recommendations The owner desires to remove the five property fruit trees and establish new trees in their place. Fruit trees are of low retention value. A mix of new coniferous and deciduous species will ultimately be much more beneficial to the surrounding area over the long-term. New tree plantings will replace the lost tree canopy within a few years and ultimately surpass the canopy coverage that would have been retained by meeting the 30% retention requirement in a very short time. Arborist Report – 702 Nile Ave NE Page 5 Layton Tree Consulting LLC April 14, 2022 Updated October 26, 2022 The attached map shows the extent of driplines of subject trees. Position a tree protection barrier just beyond the driplines of neighboring trees as shown on the map. Follow the tree protection recommendations and measures as outlined below. Trees #951 and #953 are in poor condition due to extensive trunk decay. However, these can be retained at low risk due to their small size. Tree Protection Recommendations Tree protection fencing shall be positioned around any retained and/or protected trees prior to site demolition or bringing any heavy equipment onto the site. This will help to define clearing limits and protect soils and surface roots. Any roots damaged during site work outside of the tree protection fenced area shall be pruned clean at sound tissue prior to backfilling or finishing areas. Sound tissue is where the root is undamaged and the bark is completely intact with the root. This will help roots to seal off potential decay and allow them to sprout new growth. Any disturbed areas near protected trees shall be watered weekly during the dry season of June through September. This will help to create a favorable environment for new root growth and reduce the overall stress associated with root loss and disturbance. Simply finish the landscape within the driplines by maintaining the existing lawn. Maintain the existing grades inside tree protection areas. Keep large plantings, irrigation trenching and construction of hardscapes outside of tree protection areas. All landscape work within the tree protection zone shall be completed by hand-labor only. Tree Protection Measures The following guidelines are recommended to ensure that the designated space set aside for the retained trees is protected and construction impacts are kept to a minimum. Tree Protection Standards have been set forth under RMC 4-4-130 H. Performance Standards for Land Development/Building Permits; 9. Protection Measures During Construction. Review this code section prior to the start of work. • Tree protection fencing shall be erected per prior to moving any heavy equipment on site. Doing this will set clearing limits and avoid compaction of soils within root zones of retained trees. • Excavation limits shall be laid out in paint on the ground to avoid over excavating. • To establish sub grade for foundations, curbs and pavement sections near the trees, soil should be removed parallel to the roots and not at 90-degree angles to avoid breaking and tearing roots that lead back to the trunk within the drip-line. Any roots damaged during these excavations should be exposed to sound tissue and cut cleanly with a saw. • Areas excavated within the drip-line of retained trees should be thoroughly irrigated weekly during dry periods. Arborist Report – 702 Nile Ave NE Page 6 Layton Tree Consulting LLC April 14, 2022 Updated October 26, 2022 • Preparations for final landscaping shall be accomplished by hand within the drip-lines of retained trees. Large equipment shall be kept outside of the tree protection zones at all times. Tree Density-Tree Replacement - Updated Consult with your City planner on final tree replacement/landscape requirements. Per the following code sections as underlined below. H. PERFORMANCE STANDARDS FOR LAND DEVELOPMENT PERMITS: 1. Protected Trees: Trees required to be retained or planted pursuant to this subsection H1 are considered protected trees, as defined in RMC 4-11-200, Definitions T. Protected trees shall be retained or planted as follows: a. Minimum Tree Retention Requirements: Properties subject to an active land development permit shall retain a minimum of thirty percent (30%) of all significant trees on site. b. Tree Credit Requirements: With the exception of interior remodels not involving any building addition, removal of trees, or alteration of impervious areas, properties subject to an active land development permit shall comply with all of the following minimum tree credit requirements, and apply the tree credit value table in subsection H1bv of this Section: i. Tree credit requirements shall apply at a minimum rate of thirty (30) credits per net acre. ii. Either tree retention or a combination of tree retention and supplemental tree planting (with new small, medium, or large tree species) shall be provided to meet or exceed the minimum tree credits required for the site. iii. Supplemental tree planting shall consist of new small, medium, or large species trees, as defined in RMC 4-11-200, Definitions T. The supplemental trees shall be planted with a minimum size of two-inch (2") caliper, or evergreen trees with a minimum size of six feet (6') tall. The Administrator shall have the authority to approve, deny, or restrict the tree species for proposed supplemental trees. iv. Within subdivisions, location of supplemental tree replanting shall be prioritized within tree tract(s) versus individual lots. v. Tree credit value for each tree, existing or new, is assigned as shown in the following table: e. Replacement Requirements: As an alternative to retaining trees, the Administrator may authorize the planting of replacement trees on the site if it can be demonstrated to the Administrator’s satisfaction that an insufficient number of trees can be retained. i. Replacement Criteria: Replacement planting in lieu of minimum tree retention may be granted for situations where: Arborist Report – 702 Nile Ave NE Page 7 Layton Tree Consulting LLC April 14, 2022 Updated October 26, 2022 (a) There are special circumstances related to the size, shape, topography, location, or surroundings of the subject property; or (b) The strict application of the code would prevent reasonable use of property; or (c) The strict application of the code would prevent compliance with minimum density requirements of the zone; or (d) The project is a short plat with four (4) or fewer lots. ii. Replacement Quantity and Standards: When the minimum number of protected trees cannot be retained, replacement trees with at least a two-inch (2") caliper, or evergreen trees at least six feet (6') tall, shall be planted based on the tree credit value of each protected tree removed pursuant to the table shown in subsection H1b of this Section. The protected trees used for calculating required credit replacement shall be determined based on the priority order of the significant trees proposed for removal on site. Replacement trees shall not contribute to the total credits required pursuant to subsection H1b of this Section. The City may require a surety or bond to ensure the survival of replacement trees. iii. Replacement Tree Species: The Administrator shall have the authority to approve, deny, or restrict the tree species for proposed replacement trees. f. Fee in Lieu: When the Administrator determines that it is infeasible to replace or supplement trees on the site, payment into the City’s Urban Forestry Program fund may be approved in an amount of money approximating the current market value of the replacement trees and the labor to install them. The City shall determine the value of replacement trees. Minimum Tree Density is 30 tree credits per net acre. The property is 31,996 sq.ft. requiring a minimum of 22 tree credits. To satisfy the tree density requirement, the planting of 10 new medium species (worth 1 tree credit each) and 6 new large species (worth 2 tree credits each) is recommended. The City’s approved tree list is attached. Replacement tree species shall be chosen from this list. Plant new trees in areas where they can fully mature without conflicting with new improvements. Work with a landscape architect to select species and locations appropriate for the site. Consult with your city planner on final tree replacement requirements and species selections. Arborist Report – 702 Nile Ave NE Page 8 Layton Tree Consulting LLC April 14, 2022 Updated October 26, 2022 Arborist Disclosure Statement Arborists are tree specialists who use their education, knowledge, training and experience to examine and assess trees, recommend measures to enhance the beauty and health of trees, and attempt to reduce the risks associated with living near trees. Clients may choose to accept or disregard the recommendations of the arborist, or to seek additional advice. Arborists cannot detect every condition that could possibly lead to the structural failure of a tree. Trees are living organisms that grow, respond to their environment, mature, decline and sometimes fail in ways we do not fully understand. Conditions are often hidden within trees and below ground. Arborists cannot guarantee that a tree will be healthy and/or safe under all circumstances, or for a specified period of time. Likewise, remedial treatments, like any medicine, cannot be guaranteed. Treatment, pruning and removal of trees may involve considerations beyond the scope of the arborist’s services such as property boundaries, property ownership, site lines, disputes between neighbors, and other issues. Arborists cannot take such considerations into account unless complete and accurate information is disclosed to the arborist. An arborist should then be expected to reasonably rely upon the completeness and accuracy of the information provided. Trees can be managed, but they cannot be controlled. To live near trees is to accept some degree of risk. The only way to eliminate all risk associated with trees is to eliminate all trees Arborist Report – 702 Nile Ave NE Page 9 Layton Tree Consulting LLC April 14, 2022 Updated October 26, 2022 Photo Documentation Tree #1 on left, #2 on right Looking west across back of property, Tree #952 on immediate left Arborist Report – 702 Nile Ave NE Page 10 Layton Tree Consulting LLC April 14, 2022 Updated October 26, 2022 Looking east across back of property, Tree #947 in foreground Looking east at off-site trees in access tract Arborist Report – 702 Nile Ave NE Page 11 Layton Tree Consulting LLC April 14, 2022 Updated October 26, 2022 Tree #951 – lower trunk, extensive decay Tree #953 – lower trunk, extensive decay Arborist Report – 702 Nile Ave NE Page 12 Layton Tree Consulting LLC April 14, 2022 Updated October 26, 2022 NE 7th PL ROW adjacent to subject property Nile Ave NE ROW adjacent to subject property Layton Tree Consulting LLC For:Sierra Homes Site:702 Nile Ave NE - Renton Tree Summary Table Date: Tree/DBH Height Tag #Species (inches)(feet)Condition Comments Proposal N S E W 1 pear 10 15 4 8 8 4 Fair recently cut back Remove 2 cherry-fruit 6 14 7 5 8 7 Fair decent form Remove 952 apple 17,15 (23)25 15 16 17 18 Fair typical, moderate trunk decay Remove 949 apple *13 18 13 10 10 11 Fair typical, decent form Remove 947 apple *12 21 11 10 12 12 Fair typical, moderate trunk decay Remove Neighboring/Off-site Trees 946 apple 12,9 (15)27 11 15 12 13 Fair typical, moderate trunk decay Protect 948 apple 9 22 5 12 8 4 Fair poor form Protect 950 apple *22 29 13 13 12 15 Fair typical, moderate trunk decay Protect 951 apple *26 31 8 15 17 13 Poor extensive trunk decay, low risk Protect 953 apple 18 25 6 13 12 12 Poor extensive trunk decay, low risk Protect Dripline measurements from face of trunk * - caliper measurement at one-foot above ground Drip-Line / Limits of Disturbance (feet) 4/6/2022 Calculated DBH: the DBH is parenthesis is the square root of the sum of the dbh for each individual stem squared (example with 3 stems: dbh = square root [(stem1)2 +(stem2)2 APPROVED TREE LIST – Small, Medium, and Large H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 1 In the City of Renton there is an overabundance of maple and cherry species. According to the most recent street tree inventory, maples currently comprise 35% and cherry 24% of all species. To reduce a catastrophic loss of species, experts agree that 10% o r less of any species or cultivar exist within a street tree population. Because of this, planting maple or cherry trees within the right -of-way is discouraged. SMALL TREES: 30 feet in height or less Botanical name / Common Name Mature Height in Feet Mature Spread in Feet Fall Color Comments Acer buergeranum / Trident Maple 20 20 yellow orange and red Adaptable to urban environments. Decidiuous: prefers moist, well-drained soils: tolerates infertile sites. Drought tolerant. Acer campestre / Hedge Maple 30 30 yellow Deciduous; prefers moist, rich soils; slow growing tree tolerant of air pollution and soil compaction; yellow fall color; cultivars available including Queen Elizabeth maple (‘Evelyn’) with dark green, glossy foliage. Acer circinatum / Vine Maple 20-25 10 orange and red Deciduous; prefers moist, well-drained soils; tolerates seasonal saturation and varying soil types; drought tolerant once established; bushy shrub or small tree; most often multi-trunked and does well in small groups; white flowers April- June. Acer ginnala 'Flame' / Amur Maple 20 20 red Deciduous; prefers moist, well-drained soils, but is tolerant of drought; is often multi-trunked, but can be pruned to a single stem; rounded form; fragrant, yellowish-white flowers in spring; cultivars are available such as ‘Flame’ and ‘Embers’ with differing fall colors. Select or prune for single stem; can be multi- trunked. Acer grandidentatum 'Schmidt' / Rocky Mt. Glow Maple 25+ 15 intense Acer griseum / Paperback Maple 25 20 scarlet Deciduous; prefers moist, well-drained soils, but is moderately drought tolerant; bronze peeling bark provides year-round visual interest; often multitrunked, but can be trained to a single stem; slow growing; disease and pest resistant. Smooth, peeling, cinnamon colored bark. APPROVED TREE LIST – Small, Medium, and Large H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 2 Botanical name / Common Name Mature Height in Feet Mature Spread in Feet Fall Color Comments Acer palmatum / Japanese Maple 20 24 yellow, orange, red Prefers moist, well-drained soils; deciduous; slow to moderate growth rate; multi-trunked with spreading branches; intolerant of inundation but moderately drought resistant; vibrant fall colors; many cultivars available including ‘Emperor I’, ‘Katsura’, and ‘Osakazuki’. Hundreds of varied cultivars. Can be slow growing. Acer saccharum 'Apollo' 25 10 yellow, orange Prefers well drained soils, but grows in varying soils; hearty. Acer platanoides 'Globosum' / Globe Norway Maple 20 18 yellow Moist soils preferred, but tolerates drought and seasonal inundation; tolerant of urban pollution; dense, compact, round form; slow-growing deciduous tree with brilliant fall color; shallow root system may make mowing under the tree slightly difficult; good selection for locations under power lines; another cultivar well suited for such a location is A. platanoides ‘Almira,’ reaching only 20-25 ft. Rounded top, and compact growth. Acer truncatum / Purpleblow maple 20-25 20-25 Prefers moist, well-drained soil, but drought tolerant; very cold hardy deciduous tree; moderate growth rate; yellow flowers in spring; an additional maple cultivar of interest is 'Pacific sunset'. Acer truncatum x A. platanoides 'Warren's Red' / Pacific Sunset 30 25 yellow- orange/ red Acer Triflorum - Roughbark maple 25-30 20-25 apricot, gold Deciduous; prefers moist soils, but somewhat drought tolerant once established; rough, knobby trunk provides interest in winter; disease and pest resistant; non- aggressive roots do not damage sidewalks or driveways. Amelanchier grandiflora 'Princess Diana' 20 15 bright red Good for limited space. Amelanchier x grandiflora 'Autumn Brilliance' Serviceberry 20 15 red or yellow Moist to dry, well-drained soils; small tree; drought tolerant; white clustered flowers in spring; also try 'Princess Diana' for bright red fall color and the slightly taller 'Robin Hill' (20-30 feet). Reliable bloom. Amelanchier laevis ' lustre' / Luster Serviceberry 25 25 red or yellow Moist to dry, well-drained soils; small tree; drought tolerant; white clustered flowers in spring. APPROVED TREE LIST – Small, Medium, and Large H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 3 Botanical name / Common Name Mature Height in Feet Mature Spread in Feet Fall Color Comments Arbutus 'Marina' 25 15 evergreen Good substitute for Pacific Madrone. May exceed 25' height under some site conditions. Carpinus caroliniana / American hornbeam 20-30 20-20 Deciduous; prefers moist, rich soils; grows near saturated areas but is only weakly tolerant of saturation; blooms March-May; slow growing; deep coarse laterally spreading roots; medium life span; also consider Carpinus japonica (Japanese hornbeam). Cercis canadensis / Eastern Redbud 25 30 yellow Deciduous; prefers moist, rich soils; tolerant of shade; somewhat drought resistant, but not in full sun; purple-lavender flowers; medium longevity; often multi-trunked; shallow, fibrous roots become deeper on drier sites; fairly short- lived; blooms March-May. Blooms before leaves are out. Cornus kousa 'Chinensis' / Chinese Kousa Dogwood 20 20 reddish to scarlet Prefers moist soils; tolerant of varying soil types; moderate growth rate; deciduous; white flowers in June and large red fruits that resemble a raspberry in September; red to maroon fall color; more disease resistant than other dogwoods; many additional cultivars available. Most resistant to disease of the dogwoods. Crataegus crus-galli 'Inermis' / Thornless Cockspur Hawthorn 25 30 orange to scarlet Red persistent fruit. Crataegus x lavalii / Lavalle Hawthorne 28 20 bronze, coppery red Deciduous; prefers moist, well-drained soil, but tolerant of varying soil types; white flowers in spring; fruit can be a bit messy. Thorns on younger trees. Crataegus phaenopyrum / Washington Hawthorn 25 20 scarlet Thorny. Fraxinus pennsylvanica 'Johnson' / Leprechaun Ash 18 16 yellow Prefers moist, well-drained soils; deciduous: slow to moderate growth rate; tolerant of inundation but moderately drought resistant. A miniature in every way. Magnolia x loebneri 20 20 yellow Several cultivars. Magnolia grandiflora 'Little Gem' 15 10 evergreen Useful where larger varieties are inappropriate. Magnolia grandiflora 'Victoria' 25 20 evergreen APPROVED TREE LIST – Small, Medium, and Large H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 4 Botanical name / Common Name Mature Height in Feet Mature Spread in Feet Fall Color Comments Malus spp. / Flowering crabapple 15-25 6-15 Selection should be based on disease resistance to apple scab and fireblight. Tolerant of prolonged soil saturation; short lived; tolerant of drought and seasonally saturated soils; deciduous; white or faintly pink flowers in spring; numerous Malus species and cultivars provide a variety of foliage and flower colors, forms and fruit. Malus 'Adirondack' 18 8 yellow Red fruit. Excellent scab resistance. Malus 'Red Barron' 18 8 yellow Good for narrow spaces. Red berries. Malus 'Golden Raindrops' 18 13 yellow Abundant yellow fruit. Malus 'Tschonoskii' 28 14 scarlet Sparse green fruit, pyramidal. Parrotia persica / Persian Parrotia 30 20 yellow- orange red Moist to dry soils; drought tolerant when established, deciduous tree with moderate growth rate; brilliant fall color; often multi-trunked, but can be trained to have just one; tolerates urban pollution and soil compaction; surface roots do not generally cause problems; virtually disease and pest-free. Pranus 'Frankthrees' / Mt. St. Helens Plum 20 20 Purple foliage. Prunus 'Newport' / Newport Plum 20 20 reddish to scarlet Purple red foliage. Prunus cerasifera 'Krauter Vesuvius' / Flowering Plum 30 15 Upright growth, darkest foliage of the plums. Prunus cerasifera 'Thundercloud' / Plum 20 20 Dark purple foliage. Prunus x hillieri 'Spire' 30 10 orange red Prunus 'Snowgoose' / Snow Goose Cherry 20 20 Upright when young, spreading when older. Prunus serrulata 'Amanogawa' / Flowering Cherry 20 6 bronze Particularly useful for very narrow planting strips. Prunus serrulata 'Shirofugen' / Japanese flowering cherry 25 25 Deciduous flowering tree; moist, well-drained soils; double pink to white blooms in spring; vigorous grower; additional desirable choices include P. serrulata ‘Snowgoose’, ‘Kwanzan’, and ‘Shirotae’. Prunus x yedoensis 'Akebono' / Flowering Cherry 25 25 yellow APPROVED TREE LIST – Small, Medium, and Large H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 5 Botanical name / Common Name Mature Height in Feet Mature Spread in Feet Fall Color Comments Quercus Ilex / Holly Oak 20 20 Prefers moist soils, but grows in varying soils; hearty, slow-growing evergreen tree; light pink flowers May-June; pruning will keep tree small for a hedge, without pruning may grow considerably larger – not appropriate under utility lines; tolerates salt water spray. Prune to keep small, leave it alone to grow large. Styrax japonica / Japanese Snowbell 25 25 yellow Plentiful, green 1/2 inch seeds. Styrax obassia / Fragrant Snowbell 30 25 Prefers moist, well-drained soil but tolerates wide variations; fragrant with flowers; twisting bark. Try other Styrax species. APPROVED TREE LIST – Small, Medium, and Large H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 6 MEDIUM TREES: 30 to 50 feet in height Botanical name / Common Name Mature Height in Feet Mature Spread in Feet Fall Color Comments Acer campestre 'Evelyn' / Queen Elizabeth Maple 35 30 yellow More upright branching than the species. Acer platanoides 'Columnar' / Columnar Norway maple 40 15 yellow Deciduous; adapts to varying soils; upright or columnar in form making this cultivar a better choice for narrow locations; tolerant of drought and seasonal inundation; tolerates urban pollution and displays brilliant fall color; shallow rooting necessitates locating at least 4-6 feet from sidewalks and driveways to prevent heaving of pavement. Good close to buildings. Acer truncatum x A. platanoides 'Klethsform' / Norwegian Sunset 35 25 yellow- orange/ red Acer rubrum 'Bowhall' / Bowhall Maple 40 15 yellow orange Acer rubrum 'Karpick' / Karpick Maple 35-40 20 yellow to orange May work under very high powerlines with arborist's approval. Acer rubrum 'Scarsen' / Scarlet Sentinel Maple 40 20 yellow orange Acer rubrum / Red Maple 35-50 15-40 Deciduous tree known for fall color; prefer wet or moist soils; fast growing with roots that may heave sidewalks or interfere with mowing; many cultivars of varying heights available including: A. rubrum, 'Armstrong', 'Bowhall', 'Karpick', 'Scarsen', and 'Red Sunset'. Betula jacquemontii / Jacquemontii Birch 40 30 yellow White bark makes for good winter interest. Carpinus betulus 'Fastigiati' / Pyramidal European Hornbeam 35 25 yellow Fagus sylvatica 'Dawyck Purple' / Dawyck Purple Beech 40 12 Purple foliage. APPROVED TREE LIST – Small, Medium, and Large H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 7 Botanical name / Common Name Mature Height in Feet Mature Spread in Feet Fall Color Comments Fraxinus americana 'Autumn Applause' / Ash 40 25 purple Deciduous; prefers moist, well-drained soils; dense, wide spreading canopy; long-lived; purple fall color; moderate growth rate; also try F. Americana 'Junginger'. Fraxinus oxycarpa 'Raywood' / Raywood Ash 35 25 reddish purple Pyrus calleryana 'Aristocrat' / Pear 40 45 red Pyrus calleryana 'Chanticleer' / Flowring Pear 40 15 Deciduous tree that grows well in a variety of soil types; orange to reddish fall color; white flowers in spring; additional cultivars of interest include P. calleryana 'Redspire' and 'Aristocrat'. Pyrus calleryana 'Redspire' / Pear 40 45 red Pyrus calleryana 'Autumn Blaze' / Pear 30 25 scarlet Vigorous. Ginko biloba 'Autumn Gold' / Maidenhair tree 45 35 yellow Moist soils; deciduous ornamental tree; fast growing and long-lived; tolerant of urban pollution, summer drought and winter inundation; showy fall color; grows in soils of varying quality; provides dense canopy; additional cultivars available. Ginko biloba 'Princeton Sentry' 40 15 yellow Very narrow growth. Gleditsia triacanthos inermis 'Shademaster' / Shademaster Thornless Honeylocust 45 35 yellow Deciduous; prefers moist, rich soils, but will grow in varying soil types; a thornless cultivar tolerant of drought and seasonal inundation; adapts to urban pollution and displays vigorous growth; deciduous tree with showy yellow fall color; additional cultivars available such as ‘Imperial,’ which grows 30-35 feet, ‘Moraine,’ and ‘Rubylace’. Do not confuse with 'Sunburst'. Koelreuteria paniculata / Goldenrain Tree 20-35 10-30 yellow Deciduous; prefers moist well-drained soils, but is tolerant of poor soils; medium rate of growth and longevity; tolerant of periods of drought and seasonal inundation; tolerates urban pollution; provides a dense, wide-spreading canopy. Midsummer blooming. Oxydendron arboreum / Sourwood 35 12 reddish purple Consistent and brilliant fall color. Prunus sargentii 'Columnarus' 35 15 orange to orange red The cherry with the best fall color. APPROVED TREE LIST – Small, Medium, and Large H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 8 Botanical name / Common Name Mature Height in Feet Mature Spread in Feet Fall Color Comments Quercus 'Crimschmidt' / Crimson Spire Oak 45 15 Hard to find. Robinia x ambigua 'Idahoensis' / Pink Idaho Locust 35 25 yellow Fragrant flowers. Tilia americana 'Redmond' 35 20 yellow Pyramidal, needs water. Tilia cordata 'Chancole' / Chancelor Linden 35 20 yellow Pyramidal. Tilia cordata 'De Groot' / Linden 30-50 20 yellow Compact, suckers less than other Lindens. Tilia cordata 'Greenspire' / Greenspire Linden 40 30 yellowish Symmetrical pyramidal form. Tilia cordata 'Littleleaf' / Littleleaf Linden 30-50 30 Deciduous; prefers moist, well-drained soils, but tolerant of a variety of soil types; tolerant of wind and urban pollution; fast growing and long-lived; tolerates summer drought and seasonal inundation; provides a dense canopy; C. cordata is the hardiest Linden; many forms available including, T. cordata ‘Chancellor’, ‘Corzam’, and ’Greenspire’. APPROVED TREE LIST – Small, Medium, and Large H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 9 LARGE TREES: 50 feet in height or taller Botanical name / Common Name Mature Height in Feet Mature Spread in Feet Fall Color Comments Acer freemanli / Autumn Blaze Maple 50 40 orange Abies grandis / Grand Fir 100 40 Evergreen; tolerant of fluctuating water tables and floods; medium rate of growth; root structure depends on site conditions – shallow in moist areas, deep taproot in drier conditions. Acer nigrum 'Green Colunm' / Green Column Maple 50 20 yellow to orange Good close to buildings. Acer platanoides 'Emerald Queen' 50 40 yellow Deciduous; fast growing with an erect, spreading form; prefers moist soils, but is tolerant of summer drought and seasonal inundation; tolerates urban pollution; avoid locating near structures due to shallow, vigorous rooting; additional cultivars available including A. platanoids ‘Parkway’. Acer pseudoplatanus / Sycamore maple 40-60 25-40 Deciduous; prefers moist, well-drained soils but is adaptable to may soil types; tolerates summer drought and seasonal inundation; tolerant of urban pollution with a moderate growth rate; sturdy, resistant to wind and salt spray; a number of cultivars are available including: A. pseudoplatanus ‘Atropurpureum,’ ‘ Brilliantissimum,’ ‘Cox’ (Lustre), and ‘Puget Pink’. Acer saccharum 'Bonfire' 50 40 bright orange red Fastest growing sugar maple. Acer saccharum 'Commemoration' 50 35 orange to orange- red Resistant to leaf tatter. Acer saccharum 'Green Mountain' 45 35 red to orange Acer saccharum / Sugar maple 60-75 35 yellow, orange Deciduous; prefers moderately moist, well-drained soils; long-lived and tolerant of urban pollutants; slow to medium growth rate; needs large planting area; a variety of cultivars available including Acer saccharum ‘Legacy’. APPROVED TREE LIST – Small, Medium, and Large H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 10 Botanical name / Common Name Mature Height in Feet Mature Spread in Feet Fall Color Comments Calocedrus decurrens / Incense cedar 75-90 10-20 Evergreen; tolerant of poor soils; drought tolerant after established; tolerant of wind and urban conditions; narrow growth habit makes this a good choice for smaller spaces and ideal for screening, fragrant tree; slow growing and long- lived. Carpinus betulus / European Hornbeam 40-60 30-40 Deciduous tree: tolerant of urban pollution and poor soils; cultivars available and suggested include 'Fasigiata' (30-40 ft height) and 'Franz Fontaine' (30-35 ft height). Cedrus deodara / Deodar cedar 40-60 20-40 Evergreen; prefers moist, well-drained soils, but drought tolerant when established; fairly fast growing and long lived; dense, wide spreading canopy; attractive cultivars available. Cercidiphyllum japonicum / Katsura Tree 40-60 20-40 apricot, orange Deciduous; requires moist soil and does not do well on hot dry sites. Leaves are heart-shaped. Cercidiphyllum japonicum / Katsura Tree 40 40 yellow to orange Fagus sylvatica / Green Beech 50 40 bronze Silvery-grey bark. Fraxinus american 'Autumn Purple' / Autumn Purple White Ash 60-80 50-70 to a dark purple Deciduous; prefers moist well-drained soils but tolerates a range of soil types; Also try 'Rosehill'. Fraxinus latifolia / Oregon Ash 40-80 30 Deciduous; saturated, ponded or moist soils; flood tolerant; small green-white flowers; tolerant of poor soils. Fraxinus pennsylvanica / Green Ash 50 40 Deciduous; prefers moist soils; fast growth rate; salt, seasonal drought and urban pollution; numerous cultivars including'Patmore' (50-60 ft. height), 'Summit' (to 45 ft. height), and 'Urbanite' (to 50 ft. height). Fraxinus pennsylvanica 'Patmore' / Patmore Ash 45 35 yellow Extremely hardy, may be seedless. Fraxinus pennsylvanica 'Urbanite' / Ash 50 40 deep bronze Gleditsia triacanthos inermis 'Skyline' / Skyline Thornless Honeylocust 60-70 40 yellow Deciduous; prefers moist soils, but will grow in poor soils; tolerant of drought, seasonal inundation, and urban pollution; occasionally fruit pods can create litter during winter months; thornless. Do not confuse with 'Sunburst'. APPROVED TREE LIST – Small, Medium, and Large H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 11 Botanical name / Common Name Mature Height in Feet Mature Spread in Feet Fall Color Comments Gymnocladus dioicus espresso / Espresso Kentucky Coffeetree 50 35 yellow Deciduous; drought and variable soil tolerant; seedless. Liquidamber styraci fleia / American sweetgum 60-75 40 Deciduous; prefers moist well-drained soils but tolerant of poor soils; drought tolerant after established; avoid major roadways and restricted sites. Many cultivars available. Liriodendron tulipifera / Tulip Tree 60-80 30-60 yellow Deciduous; prefers moist, deep, well-drained soils, but tolerates poor soils; fast growing; needs large growing area, lower growing cultivars available such as 'Columnar'. Fast-growing tree. Metasequoia glyptostoboides / Dawn redwood 70-100 25 Deciduous; prefers moist, deep, well-drained soils, but tolerates compacted and poor soils; long-lived, fast growing conifer; tolerant of seasonal inundation and drought; can grow in standing water; needles turn russet in the fall; needs large growing area; lower growing cultivars available such as M. glyptostroboides ‘Gold Rush’ and ‘Sheridan Spire’. Nothofagus antartica / Southern Beech 50 35 none Rugged twisted branching and petite foliage. Nyssa sylvatica / Tupelo 70+ 20 apricot to bright red Handsomely chunky bark. Picca omorika / Serbian spruce 50-60 20-25 Slow growing; tolerant of varying soils and urban pollution; moderately drought tolerant once established; elegant evergreen spruce, good for narrow locations; lower growing cultivars available. Pseudotsuga menziesii / Douglas fir 75-120 40 Evergreen conifer; moist to dry soils; long-lived with a medium to fast rate of growth; tolerant of summer drought, winter inundation, and poor soils; withstands wind and urban pollution; provides a nice canopy, but potential height will restrict placement. Quercus coccinea / Scarlet oak 50-60 45 brilliant scarlet to red Deciduous; grows in a variety of soil types; long-lived with a moderate growth rate; tolerant of summer drought and urban pollution; does not tolerate saturated soils or shade. APPROVED TREE LIST – Small, Medium, and Large H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 12 Botanical name / Common Name Mature Height in Feet Mature Spread in Feet Fall Color Comments Quercus macrocarpa / Burr oak 70-80 30-40 Prefers moist soils, but is adaptable to varying soils; slow growing and long-lived; rugged looking deciduous tree; tolerant of seasonal drought and inundation; tolerates urban pollution and city conditions; provides a wide-spreading, dense canopy. Quercus phellos / Willow oak 60-70 50 Deciduous; prefers moist, well-drained soils, but grows in a wide range of soils types; long-lived tree with moderate growth rate and fibrous root system; tolerant of seasonal drought and inundation, as well as urban pollution; provides a wide-spreading, dense canopy; small delicate leaves. Quercus palustris 'Crownright' 80 40 More upright form of Pin Oak. Quercus robar / English oak 40-60+ 40 Prefers well-drained soil; slow to moderate growth rate; long-lived deciduous tree; tolerant of seasonal drought and inundation; tolerates urban pollution, poor soils and constrained root space; susceptible to powdery mildew; many varieties and cultivars available including: ‘Concordia,’ ‘Fastigiata,’ ‘Foliis Variegatis, and ’Westminster Globe.’ Quercus rubra / Northern red oak 60-75 50 Prefers moist, well-drained soils, but drought tolerant when established; tolerates seasonal inundation, urban pollution and salt spray; moderate rate of growth and longevity; provides a dense, wide-spreading canopy; susceptible to oak wilt fungus. Quercus shumardii / Shumard's oak to 70 50 Prefers moist, well-drained soils; deciduous, long-lived tree; tolerant of seasonal drought and inundation, urban pollution and poor soils. Taxodium distichum / Bald cypress to 75 40 Deciduous conifer; wet, mucky soils; tolerant of summer drought and seasonal flooding; will grow in poor soils; slow growing; long-lived with a wide-spreading canopy; roots do not appear to lift sidewalks as readily as other species; prune lower branches for sight-lines; cultivars include T. distichum ‘Shawnee Brave’. Thuja plicata / Western red cedar 200+ 60 Moist to swampy soils; evergreen tree tolerant of seasonal flooding and saturated soils; a good tree for screening; long-lived; cultivars ‘Pumilio’ and ‘Cuprea’ are shorter versions, ‘Aurea’ and ‘Atrovirens’ have distinctive foliage. Tilia americana x euchlora 'Redmond' / Redmond Linden 50 35 yellow Prefers moist, rich soils, but tolerant of a variety of soils; tolerant of seasonal drought and inundation, urban pollution and poor soils; deciduous tree resistant; also try 'Sentry' and 'Boulevard'. APPROVED TREE LIST – Small, Medium, and Large H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 13 Botanical name / Common Name Mature Height in Feet Mature Spread in Feet Fall Color Comments Tilia plalyphyllos / Bigleaf linden 60-80 60 Prefers moist, well-drained soils, but grows in a variety of soil types; deciduous tree with medium growth rate; long-lived; tolerant of seasonal drought and inundation; tolerates urban pollutants; provides a wide-spreading, dense canopy; yellowish-white flowers attract bees. Tilia tomentosa / Silver Linden 40-75 25-45 Deciduous; prefers moist, well-drained soils, but drought tolerant when established; urban tolerant. Cultivars include 'sterlay' and 'Green Mountain'. Ulmus ssp. / Elm hybrids 50-60 35-50 yellow Deciduous; prefers moist, well-drained soils, but drought tolerant; rapid grower; a hybrid elm resistant to Dutch elm disease; suggested hybrids include ‘Accolade’, ‘Homestead’ and ‘Pioneer’. Ulmus 'Homestead' / Homestead Elm 60 35 yellow Ulmus parvifolia / Lace Bark Elm 50 40 Deciduous; prefers moist, well drained soils but tolerant of soil types and hot dry conditions. Flaking bark of orange, gray, green and brown color. Several cultivars including 'Allee' and 'Bosque'. Ulmus 'Pioneer' / Pioneer Elm 60 50 yellow Resistant to Dutch elm disease. Umbellularia californica / Oregon myrtle 40-75+ to 50 Prefers moist, well-drained soils; slow growing evergreen tree with aromatic leaves; tolerates seasonal drought and inundation; tolerant of urban pollution; provides a wide spreading, dense canopy; resistant to pests and disease; good for tall hedges or, when trunks are thinned, as a street tree; requires summer watering until established. Appendix D WWHM Output WWHM2012 PROJECT REPORT 21706 WWHM 10/25/2022 1:15:34 PM Page 2 General Model Information Project Name:21706 WWHM Site Name: Site Address: City: Report Date:10/25/2022 Gage:Seatac Data Start:1948/10/01 00:00 Data End:2009/09/30 00:00 Timestep:Hourly Precip Scale:1.167 Version Date:2021/08/18 Version:4.2.18 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year 21706 WWHM 10/25/2022 1:15:34 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 0.195 Pervious Total 0.195 Impervious Land Use acre Impervious Total 0 Basin Total 0.195 Element Flows To: Surface Interflow Groundwater 21706 WWHM 10/25/2022 1:15:34 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre ROOF TOPS FLAT 0.13 DRIVEWAYS FLAT 0.06 SIDEWALKS FLAT 0.005 Impervious Total 0.195 Basin Total 0.195 Element Flows To: Surface Interflow Groundwater 21706 WWHM 10/25/2022 1:15:34 PM Page 5 Routing Elements Predeveloped Routing 21706 WWHM 10/25/2022 1:15:34 PM Page 6 Mitigated Routing 21706 WWHM 10/25/2022 1:15:34 PM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.195 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0 Total Impervious Area:0.195 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.00694 5 year 0.011074 10 year 0.013761 25 year 0.017015 50 year 0.019313 100 year 0.0215 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.059024 5 year 0.074017 10 year 0.084355 25 year 0.097918 50 year 0.108404 100 year 0.119232 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.007 0.058 1950 0.014 0.084 1951 0.015 0.056 1952 0.005 0.051 1953 0.004 0.047 1954 0.006 0.055 1955 0.010 0.058 1956 0.008 0.057 1957 0.007 0.064 1958 0.007 0.058 21706 WWHM 10/25/2022 1:15:45 PM Page 8 1959 0.006 0.044 1960 0.011 0.055 1961 0.006 0.049 1962 0.004 0.051 1963 0.005 0.048 1964 0.006 0.056 1965 0.005 0.051 1966 0.005 0.050 1967 0.010 0.076 1968 0.006 0.086 1969 0.006 0.045 1970 0.005 0.050 1971 0.005 0.049 1972 0.012 0.070 1973 0.005 0.045 1974 0.006 0.052 1975 0.009 0.066 1976 0.006 0.045 1977 0.001 0.059 1978 0.005 0.078 1979 0.003 0.077 1980 0.008 0.062 1981 0.005 0.069 1982 0.011 0.093 1983 0.007 0.070 1984 0.005 0.053 1985 0.003 0.050 1986 0.012 0.060 1987 0.011 0.088 1988 0.004 0.042 1989 0.003 0.056 1990 0.017 0.093 1991 0.014 0.088 1992 0.005 0.052 1993 0.006 0.037 1994 0.002 0.043 1995 0.008 0.054 1996 0.015 0.061 1997 0.014 0.060 1998 0.003 0.067 1999 0.009 0.123 2000 0.006 0.064 2001 0.001 0.056 2002 0.007 0.063 2003 0.005 0.058 2004 0.014 0.109 2005 0.007 0.052 2006 0.009 0.043 2007 0.023 0.097 2008 0.019 0.086 2009 0.010 0.063 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0231 0.1235 2 0.0194 0.1091 3 0.0171 0.0967 21706 WWHM 10/25/2022 1:15:45 PM Page 9 4 0.0153 0.0934 5 0.0147 0.0934 6 0.0144 0.0877 7 0.0142 0.0877 8 0.0140 0.0862 9 0.0138 0.0860 10 0.0122 0.0843 11 0.0119 0.0782 12 0.0112 0.0770 13 0.0112 0.0758 14 0.0106 0.0699 15 0.0104 0.0696 16 0.0096 0.0688 17 0.0096 0.0667 18 0.0091 0.0663 19 0.0090 0.0638 20 0.0087 0.0635 21 0.0084 0.0631 22 0.0083 0.0627 23 0.0076 0.0624 24 0.0074 0.0615 25 0.0073 0.0600 26 0.0073 0.0600 27 0.0071 0.0588 28 0.0071 0.0584 29 0.0070 0.0582 30 0.0060 0.0582 31 0.0058 0.0580 32 0.0058 0.0567 33 0.0058 0.0564 34 0.0057 0.0564 35 0.0057 0.0560 36 0.0057 0.0558 37 0.0057 0.0550 38 0.0057 0.0548 39 0.0056 0.0537 40 0.0055 0.0528 41 0.0053 0.0522 42 0.0053 0.0519 43 0.0053 0.0515 44 0.0052 0.0512 45 0.0052 0.0508 46 0.0052 0.0507 47 0.0051 0.0503 48 0.0050 0.0501 49 0.0048 0.0497 50 0.0046 0.0493 51 0.0045 0.0491 52 0.0044 0.0482 53 0.0041 0.0466 54 0.0037 0.0455 55 0.0035 0.0454 56 0.0030 0.0453 57 0.0027 0.0444 58 0.0026 0.0433 59 0.0019 0.0427 60 0.0012 0.0419 61 0.0011 0.0367