The URL can be used to link to this page

Home My WebLink AboutApproved TIR 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 TECHNICAL INFORMATION REPORT For Sierra Homes Short Plat 702 Nile Avenue NE Renton, WA 98059 March 8th, 2024 Revised June 19th, 2024 Prepared by: Gabe Garner Encompass Engineering Job No. 21706 Prepared For: Dan Finkbeiner Sierra Homes PO Box 3069 Issaquah, WA 98027 Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | i Table of Contents I. PROJECT OVERVIEW ................................................................................................................ 1 II. CONDITIONS AND REQUIREMENTS SUMMARY ...................................................................... 6 III. OFFSITE ANALYSIS .................................................................................................................. 12 IV. FLOW CONTROL, LOW IMPACT DEVELOPMENT AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ........................................................................................................................... 19 V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN ..................................................................... 22 VI. SPECIAL REPORTS AND STUDIES ............................................................................................ 23 VII. OTHER PERMITS ..................................................................................................................... 23 VIII. CSWPP ANALYSIS AND DESIGN .............................................................................................. 23 IX. BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION of COVENANT ................... 23 X. OPERATION AND MAINTENANCE MANUAL .......................................................................... 23 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 April 14, 2022, Updated September 22, 2023 Tree & Construction Memo by Layton Tree Consulting, LLC dated February 21, 2023 Appendix D WWHM Output Appendix E Operation & Maintenance Manual 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 Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 1 I. PROJECT OVERVIEW Project: Sierra Homes 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. Sierra Homes Short Plat Technical Information Report 06/19/2024 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 Sierra Homes Short Plat Technical Information Report 06/19/2024 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 and is proposed along the eastern portion of the site, Lot 2 is 10,165 SF and is proposed in the central portion of the site, and Lot 3 is 10,306 SF and is proposed along the western portion of the site. A 2,312 SF stormwater tract is proposed in the southwest corner of the site. Lots 1 & 2 will have driveway access off NE 7th Place, while Lot 3 will have driveway access to Nile Ave NE via the existing driveway entrance to the site. 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, the maximum impervious surface coverage was assumed. • Lot 1: The maximum allowable impervious surface coverage for Lot 1 is 9,214 SF * 0.50 = 4,607 SF. The final site layout of Lot 1 has not been determined at this stage; therefore, this report assumes that the future impervious surfaces required to construct the residence on Lot 1 will use the maximum coverage stated above (4,607 SF). • Lot 2: The maximum allowable impervious surface coverage for Lot 2 is 10,165 SF * 0.50 = 5,083 SF. The final site layout of Lot 2 has not been determined at this stage; therefore, this report assumes that the future impervious surfaces required to construct the residence on Lot 2 will use the maximum coverage stated above (5,083 SF). • Lot 3: The maximum allowable impervious surface coverage for Lot 3 is 10,306 SF * 0.50 = 5,153 SF. The final site layout of Lot 3 has not been determined at this stage; therefore, this report assumes that the future impervious surfaces required to construct the residence on Lot 3 will use the maximum coverage stated above (5,153 SF). • Stormwater Tract: Tract A is the 2,312 SF stormwater tract, which is proposed to include 710 SF of gravel maintenance driveway. Additionally, 11 SF of gravel maintenance driveway and 540 SF of concrete driveway apron are proposed off-site in the public right-of-way (ROW). Stormwater runoff from Lots 1-3 will be collected and conveyed to three (3) limited infiltration trenches (1 per lot). See Core Requirement #9 for the sizing information on the limited infiltration trenches. The trenches will have an overflow system which connects to a 54’ x 15’ CMP Detention Tank, located within the stormwater tract in the southwest corner of the site. To maintain the existing downstream drainage patterns to the off-site wetland, an area of lawn within Lot 1 in the developed condition will be graded towards the southeast corner of the site. Please refer to Core Requirement # 9 in Section II and Section IV of this TIR for additional discussion on stormwater BMPs and flow control. A Developed Conditions Map is provided as Figure 5 at this end of this Section. ΔΔNE 7TH PLACENILE AVENUE NE SIERRA HOMES SHORT PLATLUA22-000315FIGURE 4- EXISTING CONDITIONS MAPSIERRA HOMES SHORT PLAT---- SIERRA HOMES SHORT PLAT 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) 392-0250LUA22-000427 C23005223 PR22-000352 TED-40-4283 NE 7TH PLACENILE AVENUE NE SIERRA HOMES SHORT PLATLUA22-000315FIGURE 5- DEVELOPED CONDITIONS MAPSIERRA HOMES SHORT PLAT---- SIERRA HOMES SHORT PLATIN 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) 392-0250LUA22-000427 C23005223 PR22-000352 TED-40-4283 NORTHIMPERVIOUS AREAS: Sierra Homes Short Plat Technical Information Report 06/19/2024 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 Sierra Homes Short Plat Technical Information Report 06/19/2024 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 towards the City of Renton storm system on Nile Avenue NE and NE 7th Place as well as southeast towards the adjacent offsite wetland. In order to avoid downstream impact to the wetland, the existing site was evaluated to quantify the amount of runoff tributary to the wetland. Based on the topographic survey, approximately 2,800 SF of lawn area was found to drain to the wetland southeast of the site. In the post-developed condition, approximately 2,800 SF of lawn area will be graded to drain towards the wetland. The runoff produced from the regraded lawn area will sufficiently hydrate the wetland in order to retain the same downstream drainage conditions. Please refer to hydrologic WWHM model within Appendix D for more information. See Figure 4 - Existing Conditions Map as well as 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. A 54’x15’ CMP Detention Tank with an 84” diameter is proposed to meet stormwater requirements. This stormwater facility will be located in the southwest corner of the site within a stormwater tract. 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 is provided in Section V of this report. 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 is provided in Appendix E. Core Requirement #7: Financial Guarantees and Liability The owner will arrange for any financial guarantees and liabilities required by the permit. Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 8 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. 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 The maximum impervious surface coverage allowed per zoning is 50%. For the design of the lots, the maximum impervious surface coverage was assumed while evaluating future stormwater BMPs. Their final location and design shall be determined under the single-family building permit process. Full Dispersion: Infeasible for Lots 1-3. A 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 classification of loamy sand, with the stipulation that an overflow system is provided. For rainfall regions greater than SeaTac 1.0, a 2 FT wide gravel trench must be 48.3 feet in length in loamy sand soils to mitigate 1,000 SF of impervious surface. See sizing for limited infiltrations trenches below: • Lot 1: (4.607) * (48.3 LF) = 223 LF of 2 FT wide trench is required (223 LF) * (2 FT) = 446 SF of infiltrating surface area is required A 30 FT x 18 FT limited infiltration trench is feasible (30 FT * 18 FT = 540 SF ≥ 446 SF). • Lot 2: (5.083) * (48.3 LF) = 246 LF of 2 FT wide trench is required (246 LF) * (2 FT) = 492 SF of infiltrating surface area is required A 30 FT x 18 FT limited infiltration trench is feasible (30 FT * 18 FT = 540 SF > 492 SF) • Lot 3: (5.153) * (48.3 LF) = 249 LF of 2 FT wide trench is required (249 LF) * (2 FT) = 498 SF of infiltrating surface area is required A 30 FT x 18 FT limited infiltration trench is feasible (30 FT * 18 FT = 540 SF > 498 SF). The limited infiltration trenches will include an overflow system that connects to the proposed Contech CMP Detention Tank. Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 9 Rain Gardens/Bioretention: Infeasible for Lots 1-3. BMP’s relying on full infiltration are not feasible as described above. Permeable Pavement: Infeasible for Lots 1-3. BMP’s relying on full infiltration are not feasible as described above. Basic Dispersion: Basic Dispersion is infeasible. Directing rooftop runoff towards the backyard lawn areas will increase runoff towards the off-site wetland, which is prohibited per Section 1.2.2.1.1 of the RSWDM. 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 short plat 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. Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 10 City of Renton Department of Community & Economic Development: Conditions of Approval CITY OF RENTON DEPARTMENT OF COMMUNITY & ECONOMIC DEVELOPMENT: CONDITIONS OF APPROVAL The proposed short plat application was deemed complete on August 7, 2023. The Sierra Homes Short Plat, File No. LUA22-000427, SHPL-A, MOD, as depicted in Exhibit 2, is approved and is subject to the following conditions: 1. The applicant shall obtain a demolition permit and complete a final inspection from the city for the removal of the residence and garage on future lots 1, 2, and 3 in order to comply with residential-4 (r-4) setbacks of the zone prior to final plat approval. A demolition plan will be submitted to the City of Renton prior to final plat approval and removal of existing on-site structures. 2. The applicant shall install one new street in the row adjacent to proposed lot 1. The tree species shall be selected from the City of Renton's approved street tree list and be approved by the current planning project manager at the time of civil construction permit review. Alternatively, the applicant may retain the existing street tree located in front of proposed lot 1. One new street tree will be added in the ROW north of Lot 1. 3. The applicant shall install replacement trees within the tract if feasible, and shall plant shrubs and other ground cover around the perimeter of the tract where feasible. An updated landscape plan incorporating the additional vegetation shall be submitted with the civil construction permit application for review and approval by the current project manager. An updated landscape plan will be submitted that details tree replacement and other landscaping planting on the site. 4. The applicant shall submit an updated tree retention plan, arborist report, and tree retention worksheet that correctly identify the number of existing trees on site and demonstrate compliance with the tree retention and land clearing regulations in RMC 4-4-130. The applicant shall utilize the tree preservation priority tiers outlined in RMC 4-4-130.H.2.A to identify the specific trees to be retained. The applicant shall submit a narrative describing how all reasonable efforts have been taken to preserve trees utilizing the highest priority tier possible. The updated documents and narrative shall be reviewed and approved by the current planning project manager prior to issuance of the civil construction permit. The landscape plan and arborist report have been updated to correctly identify the existing trees and provide a narrative on efforts to preserve trees. 5. The applicant shall submit an updated tree retention plan, arborist report, and tree retention worksheet that clearly identifies the trees proposed for retention and demonstrates compliance with the minimum tree density requirement for residentially zoned lots. The updated Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 11 documents shall be reviewed and approved by the current planning project manager prior to issuance of the civil construction permit. An updated tree retention plan, arborist report and tree retention worksheet will be submitted. 6. The applicant shall utilize the existing curb cut off of Nile Ave. NE to access the single-family home on proposed lot 3. The existing curb cut on the west side of Lot 3 (Nile Ave) will be utilized for access to this lot. Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 12 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 Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 13 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. Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 14 Element A1 – Runoff sheet flows towards the western edge of the site Element A2 – Type 2 CB located just northwest of property corner Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 15 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) Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 16 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 Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 17 Element B3 – Runoff enters CB at southern end of wetland Element B4 – Stormwater detention pond located southwest of the wetland Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 18 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) Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 19 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 storm 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 2022 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 and is proposed along the eastern portion of the site, Lot 2 is 10,165 SF and is proposed in the central portion of the site, and Lot 3 is 10,306 SF and is proposed along the western portion of the site. A 2,312 SF stormwater tract is proposed in the southwest corner of the site. Lots 1 & 2 will have driveway access off NE 7th Place, while Lot 3 will have driveway access to Nile Ave NE via the existing driveway entrance to the site. Using the maximum impervious coverage of 50%, the total impervious surface areas were calculated. Lot 1 may have 4,607 SF, Lot 2 may have 5,083 SF, and Lot 3 may have 5,153 SF. An additional 1,261 SF of driveway (driveway aprons/gravel access road) is proposed. The total proposed new/replaced impervious is 16,104 SF. Stormwater runoff from Lots 1-3 will be collected and conveyed to three (3) limited infiltration trenches (1 per lot). See Core Requirement #9 for the sizing information on the limited infiltration trenches. The trenches will have an overflow system which connects to a 54’ x 15’ CMP Detention Tank, located within the stormwater tract in the southwest corner of the site. To maintain the existing downstream drainage patterns to the off-site wetland, an area of lawn within Lot 1 in the developed condition will be graded towards the southeast corner of the site. 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 on the following page. Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 20 Existing Developed Condition Measured Modeled Measured Modeled C, Forest, Flat: 30,367 SF (0.70 AC) 30,367 SF (0.70 AC) C, Lawn, Flat: 14,263 SF (0.33 AC) 14,263 SF (0.33 AC) Roof Tops, Flat: 14,843 SF (0.34 AC) 14,843 SF (0.34 AC) Driveway, Flat: 1,261 SF (0.03 AC) 1,261 SF (0.03 AC) Total Area: 30,367 SF (0.70 AC) 30,367 SF (0.70 AC) 30,367 SF (0.70 AC) 30,367 SF (0.70 AC) WWHM Conditions Model Wetland Recharge Information: There is a Category III wetland with an associated 75-foot adjacent buffer located just southeast of the site. The project proposes to discharge approximately 2,800 SF of proposed lawn area to towards the wetland for recharge. Please refer to the Wetland Reconnaissance for 702 Nile Ave, Renton WA by Altmann Oliver Associates, LLC in Appendix B of this Report for additional information on the wetland classification. Based on the wetland being Category III, Method 2 of analysis within Reference Section 5 of the KCSWDM is required. This requires analysis of both mean daily total discharge volumes and mean monthly total discharge volumes from the site. The total volume of water into a wetland on a daily basis should not be more than 20% higher or lower than the pre-project volumes. The proposed design meets this criteria. The total volume of water into a wetland on a monthly basis should not be more than 15% higher or lower than the pre-project volumes. The proposes design meets this criteria. Please refer to hydrologic WWHM model within Appendix D for more information. 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. 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. 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 Flow control will be provided by a Contech 54’x15’ CMP Detention Tank, with an 84” diameter. An extra 6” of sediment storage will be provided at the bottom of the tank, and an extra 6” of dead storage at the Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 21 top will be provided. Therefore, the provided volume of this system will be that of a 72” diameter system. This stormwater facility will be located in the southwest corner of the site within a stormwater tract, and discharge via a control structure to a proposed manhole located on Nile Ave NE. Per WWHM modeling, the required storage of the system is 4,095 CF. 4,168 CF of storage is provided with this system. Please refer to Appendix B for a copy of the full WWHM data output. See WWHM data inputs for detention system below: 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. Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 22 V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN According to the WWHM analysis in Appendix D, the 100-yr mitigated flow rate produced from the site is 0.070007 CFS. This represents the highest possible flow through any component of the proposed stormwater system. WWHM Conveyance Analysis Conveyance analysis has been completed for the proposed storm. The pipe which is assumed to endure the highest flows is a 12” PVC pipe sloped at 0.50% located after the detention system. This pipe was analyzed to see if it can support the 100-yr unmitigated flow rate of 0.070007 CFS (worst case scenario). Using Manning’s Equation (see table below), a 12” storm pipe sloped at 0.50% can support a flow rate of 2.60 CFS, which greatly exceeds the 100-year flow rate into the storm system (2.60 CFS > 0.070007 CFS). In addition, the velocity at full flow is 3.663 ft/s, which meets the minimum velocity requirement per Section 4.2.1.1 of the 2021 KCSWDM. Conveyance Capacity for 12” PVC @ 0.50% Slope F2,80 Sierra Homes Short Plat Technical Information Report 06/19/2024 P a g e | 23 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 April 14, 2022, Updated September 22, 2023 • Trees & Construction Memo by Layton Tree Consulting, dated February 21, 2023 VII. OTHER PERMITS • Civil Construction Permit • Building Permits • Right-of-Way Use Permit VIII. CSWPP ANALYSIS AND DESIGN A CSWPPP has been provided under separate cover. IX. BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION of COVENANT Bond Quantities, Facility Summary and Declaration of Covenant have been provided under separate cover. X. OPERATION AND MAINTENANCE MANUAL An Operation and Maintenance Manual has been provided as Appendix E. 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, LLCP.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 lessthan 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 Soft4 - 8 Medium stiff8 - 15 Stiff15 - 30 Very stiff Over 30 Hard Cobalt Geosciences, LLCP.O. Box 82243Kenmore, WA 98028(206) 331-1097 www.cobaltgeo.com cobaltgeo@gmail.com Soil Classification Chart Figure C1 Test Pit & Hand Boring Logs Cobalt Geosciences, LLCP.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 (%)PlasticLimit 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 (%)PlasticLimit 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 withgravel, dark yellowish brown, dry to moist. (Weathered Glacial Till) SM SM Loose to medium dense, silty-fine to medium grained sand withgravel 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, LLCP.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 (%)PlasticLimit 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 withgravel, 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, LLCPO Box 1792North Bend, WA 98045 (206) 331-1097 www.cobaltgeo.com phil@cobaltgeo.com Cobalt Geosciences, LLC P.O. Box 1792 North Bend, WA 98045 www.cobaltgeo.com (206) 331-1097 February 14, 2024 Dan Finkbeiner danfinkbeiner@comcast.net RE: Plan Review Proposed Residential Development 702 Nile Avenue Renton, Washington In accordance with your authorization, Cobalt Geosciences, LLC has prepared this letter to discuss our plan review of the proposed project. In preparation of this letter, we have reviewed the civil plans by Encompass Engineering and Surveying dated August 21, 203 and updated January 26, 2024. We have no comments at this time. We understand that the shallow limited infiltration systems will have suitable overflow and that detention systems will not allow any intrusion of interflow/groundwater if present. We should verify/confirm suitable soils are present at infiltration system locations, including minimum 12 inch clearance above the restrictive layer. Sincerely, Cobalt Geosciences, LLC 2/14/2024 Phil Haberman, PE, LG, LEG Principal 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 UpdateRating 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 UpdateRating 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 UpdateRating 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 UpdateRating 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 UpdateRating 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 UpdateRating 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 = 3Seasonally flooded or inundated 3 types present: points = 2Occasionally flooded or inundated 2 types present: points = 1Saturated only 1 types present: points = 0Permanently flowing stream or river in, or adjacent to, the wetlandSeasonally 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 UpdateRating 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 UpdateRating 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 UpdateRating Form - Effective January 1, 2015 9 WSDOT Adapted Form - March 2, 2015 EagleView Technologies, Inc. 0 1,000 2,000 3,000 4,000500US 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/SedimentWaterCategory 5 - 303dCategory 4CCategory 4BCategory 4ACategory 2Category 1 SedimentCategory 5 - 303dCategory 4CCategory 4BCategory 4ACategory 2Category 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/SedimentWaterCategory 5 - 303dCategory 4CCategory 4BCategory 4ACategory 2Category 1 SedimentCategory 5 - 303dCategory 4CCategory 4BCategory 4ACategory 2Category 1 WQ Improvement ProjectsApprovedIn Development Appendix C • Arborist Report by Layton Tree Consulting, LLC dated April 14, 2022, Updated September 22, 2023 • Trees & Construction Memo by Layton Tree Consulting, LLC dated February 21, 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 September 22, 2023 Arborist Report – 702 Nile Ave NE Page 2 Layton Tree Consulting LLC April 14, 2022 Updated September 22, 2023 Table of Contents Assignment.................................................................................................................................................... 3 Description .................................................................................................................................................... 3 Methodology ................................................................................................................................................. 3 Judging Condition...................................................................................................................................... 4 Observations ................................................................................................................................................. 4 Discussion/Recommendations ...................................................................................................................... 5 Tree Protection Recommendations .............................................................................................................. 5 Tree Protection Measures ............................................................................................................................ 6 Tree Density-Tree Replacement ................................................................................................................... 6 Arborist Disclosure Statement ...................................................................................................................... 7 Attachments Photos, pages 8 - 11 Tree Summary Table Tree Plan Map Arborist Report – 702 Nile Ave NE Page 3 Layton Tree Consulting LLC April 14, 2022 Updated September 22, 2023 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. 13 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 five subject trees at the back of the property are all fruit trees. There are eight small or young trees on the north and west perimeters of the property that were planted to meet the tree density and replacement requirements for the adjacent Weston Heights Subdivision. These are considered ‘significant’ trees by the city and are part of this report. 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 Arborist Report – 702 Nile Ave NE Page 4 Layton Tree Consulting LLC April 14, 2022 Updated September 22, 2023 include but are not limited to excessive or unnatural leans, crooks, forks with V-shaped crotches, multiple attachments. • 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 at the back of the property 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’. Trees #3 > #10 are young Austrian or black pine trees. These were planted roughly 5 to 6 years ago. All have developed good structural form thus far and are of good vigor. These are in good condition. 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. Arborist Report – 702 Nile Ave NE Page 5 Layton Tree Consulting LLC April 14, 2022 Updated September 22, 2023 There are several recently planted trees within the adjacent street rights-of-way. These include a cultivated variety of red maple and more Austrian pines. These are in good condition. Discussion/Recommendations Several of the property trees will be compromised by new construction and need to be removed. The proposal is to retain four of the Austrian pines on the north and west perimeters to satisfy the tree retention requirement. These are well-positioned for successful retention. Tree #10 will be compromised by the new storm water utility and need to be removed. The attached map shows the extent of driplines of subject trees to be retained. Position a tree protection barrier just beyond the driplines as shown on the map. Follow the tree protection recommendations and measures as outlined below. In order to adequately protect the off-site apple trees, provide a ‘no-disturbance’ or protection zone of 6-feet from the property line. There will be some impacts to outer dripline areas on the north side for the new detention tank but these are not expected to have any adverse impacts on tree health. Apple trees are quite hardy and have good relative tolerance to construction impacts. The condition of the subject trees is expected to remain unchanged so long as the following protection measures are adhered to. Off-site 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. Several of the small street trees (five red maple and one pine) will need to be removed for new lot access and/or utility installations. Four of the red maple trees are small enough to be dug, balled and bur lapped; and transplanted to a new location on site post construction. The other two trees will need to be replaced. 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. Arborist Report – 702 Nile Ave NE Page 6 Layton Tree Consulting LLC April 14, 2022 Updated September 22, 2023 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 (away from tree trunks) 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. • 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 30% retention of significant trees is required for the project. There are 13 significant trees on the property, requiring the retention of a minimum of 4 trees. The proposal is to retain four trees or 31% of the significant trees to satisfy the tree retention requirement. Consult with your Landscape Architect and/or City planner on any tree replacement/landscape code requirements for the project. Arborist Report – 702 Nile Ave NE Page 7 Layton Tree Consulting LLC April 14, 2022 Updated September 22, 2023 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 8 Layton Tree Consulting LLC April 14, 2022 Updated September 22, 2023 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 9 Layton Tree Consulting LLC April 14, 2022 Updated September 22, 2023 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 10 Layton Tree Consulting LLC April 14, 2022 Updated September 22, 2023 Tree #951 – lower trunk, extensive decay Tree #953 – lower trunk, extensive decay Arborist Report – 702 Nile Ave NE Page 11 Layton Tree Consulting LLC April 14, 2022 Updated September 22, 2023 NE 7th PL ROW adjacent to subject property Nile Ave NE ROW, Austrian pines on west perimeter of the property Layton Tree Consulting LLC For:Sierra Homes Site:702 Nile Ave NE - Renton Tree Summary Table Date: Updated 9-19-2023 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 3 Austrian pine 4 12 4 4 4 4 Good young specimen, good vigor Retain 4 Austrian pine 4 12 4 4 4 4 Good young specimen, good vigor Remove 5 Austrian pine 4 12 4 4 4 4 Good young specimen, good vigor Remove 6 Austrian pine 4 12 4 4 4 4 Good young specimen, good vigor Remove 7 Austrian pine 4 12 4 4 4 4 Good young specimen, good vigor Retain 8 Austrian pine 4 14 4 4 4 4 Good young specimen, good vigor Retain 9 Austrian pine 4 12 4 4 4 4 Good young specimen, good vigor Retain 10 Austrian pine 4 12 4 4 4 4 Good young specimen, good vigor 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 LAYTON TREE CONSULTING, LLC It’s all about trees…… PO BOX 572, SNOHOMISH, WA 98291-0572 * 425-220-5711 * bob@laytontreeconsulting.com TREES & CONSTRUCTION MEMO To: Ian Dahl, Encompass Engineering From: Bob Layton CC: Dan Finkbeiner, Sierra Homes Date: February 21, 2023 Re: 702 Nile Ave NE – Off-Site Tree Retention/Protection Memo Dear Mr. Dahl, I have reviewed the final site plan for the 702 Nile Avenue NE project and the city comments regarding impacts to off-site apple Trees #946, #948 and #950. A snap-shot of the site plan is attached. In order to adequately protect the off-site apple trees, the detention tank will need to be shifted 3-feet north to provide a ‘no-disturbance’ or protection zone of 6-feet from the property line. There will be some impacts to outer dripline areas on the north side but these are not expected to have any adverse impacts on tree health. Apple trees are quite hardy and have good relative tolerance to construction impacts. The condition of the subject trees is expected to remain unchanged so long as the following protection measures are adhered to. Protection Measures Tree protection fencing shall be positioned around protected trees per the attached map 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. Soils shall be cut and pulled back away from the trees to avoid tearing and shredding roots inside the protection area. Any roots from protected trees damaged during site work outside of the tree protection areas 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 February 21, 2023 702 Nile Ave NE – Tree Protection Page 2 LAYTON TREE CONSULTING, LLC disturbed areas near protected trees shall be watered weekly during the dry season of mid-May through mid-October. Thoroughly water the outer dripline areas every 7 to 10 days to maintain a favorable environment for new root growth and to reduce the degree of stress associated with the site changes. Equipment shall be kept outside of tree protection areas at all times. Any branches that are damaged during site work shall be properly pruned. Maintain the existing grades with the protection areas. Finish the landscape within the driplines of protected trees by simply maintaining the existing lawn or covering the area within the dripline with a +/- 4-inch layer of organic mulch. Keep irrigation trenches, large plantings or other improvements outside of the tree protection areas. Please let me know if you have any questions or need further assistance. Sincerely, Bob Layton Registered Consulting Arborist #670 ISA Certified Arborist #PN-2714A ISA Tree Risk Assessment Qualified Attachments: Snap-shot of Site Plan/Tree Plan Map February 21, 2023 702 Nile Ave NE – Tree Protection Page 3 LAYTON TREE CONSULTING, LLC 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. Appendix D WWHM Output WWHM2012 PROJECT REPORT FINAL 6/19/2024 10:37:56 AM Page 2 General Model Information Project Name:FINAL Site Name: Site Address: City: Report Date:6/19/2024 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.167 Version Date:2019/09/13 Version:4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year FINAL 6/19/2024 10:37:56 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 0.7 Pervious Total 0.7 Impervious Land Use acre Impervious Total 0 Basin Total 0.7 Element Flows To: Surface Interflow Groundwater FINAL 6/19/2024 10:37:56 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.1 Pervious Total 0.1 Impervious Land Use acre ROOF TOPS FLAT 0.11 Impervious Total 0.11 Basin Total 0.21 Element Flows To: Surface Interflow Groundwater Gravel Trench Bed 1 Gravel Trench Bed 1 FINAL 6/19/2024 10:37:56 AM Page 5 Basin 2 Bypass:Yes GroundWater:No Pervious Land Use acre Pervious Total 0 Impervious Land Use acre DRIVEWAYS FLAT 0.03 Impervious Total 0.03 Basin Total 0.03 Element Flows To: Surface Interflow Groundwater FINAL 6/19/2024 10:37:56 AM Page 6 Basin 3 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.11 Pervious Total 0.11 Impervious Land Use acre ROOF TOPS FLAT 0.12 Impervious Total 0.12 Basin Total 0.23 Element Flows To: Surface Interflow Groundwater Gravel Trench Bed 2 Gravel Trench Bed 2 FINAL 6/19/2024 10:37:56 AM Page 7 Basin 4 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.11 Pervious Total 0.11 Impervious Land Use acre ROOF TOPS FLAT 0.12 Impervious Total 0.12 Basin Total 0.23 Element Flows To: Surface Interflow Groundwater Gravel Trench Bed 3 Gravel Trench Bed 3 FINAL 6/19/2024 10:37:56 AM Page 8 Routing Elements Predeveloped Routing FINAL 6/19/2024 10:37:56 AM Page 9 Mitigated Routing Contech CMP 1 Element Flows To: Outlet 1 Outlet 2 FINAL 6/19/2024 10:37:56 AM Page 10 Gravel Trench Bed 1 Bottom Length:30.00 ft. Bottom Width:18.00 ft. Trench bottom slope 1:0 To 1 Trench Left side slope 0:0 To 1 Trench right side slope 2:0 To 1 Material thickness of first layer:1 Pour Space of material for first layer:0.35 Material thickness of second layer:0.5 Pour Space of material for second layer:0.39 Material thickness of third layer:0.5 Pour Space of material for third layer:0.35 Infiltration On Infiltration rate:0.35 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):29.094 Total Volume Through Riser (ac-ft.):2.19 Total Volume Through Facility (ac-ft.):31.284 Percent Infiltrated:93 Total Precip Applied to Facility:0 Total Evap From Facility:0 Discharge Structure Riser Height:2 ft. Riser Diameter:6 in. Element Flows To: Outlet 1 Outlet 2 Contech CMP 1 Gravel Trench Bed Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.012 0.000 0.000 0.000 0.0333 0.012 0.000 0.000 0.004 0.0667 0.012 0.000 0.000 0.004 0.1000 0.012 0.000 0.000 0.004 0.1333 0.012 0.000 0.000 0.004 0.1667 0.012 0.000 0.000 0.004 0.2000 0.012 0.000 0.000 0.004 0.2333 0.012 0.001 0.000 0.004 0.2667 0.012 0.001 0.000 0.004 0.3000 0.012 0.001 0.000 0.004 0.3333 0.012 0.001 0.000 0.004 0.3667 0.012 0.001 0.000 0.004 0.4000 0.012 0.001 0.000 0.004 0.4333 0.012 0.001 0.000 0.004 0.4667 0.012 0.002 0.000 0.004 0.5000 0.012 0.002 0.000 0.004 0.5333 0.012 0.002 0.000 0.004 0.5667 0.012 0.002 0.000 0.004 0.6000 0.012 0.002 0.000 0.004 0.6333 0.012 0.002 0.000 0.004 0.6667 0.012 0.002 0.000 0.004 0.7000 0.012 0.003 0.000 0.004 0.7333 0.012 0.003 0.000 0.004 0.7667 0.012 0.003 0.000 0.004 0.8000 0.012 0.003 0.000 0.004 FINAL 6/19/2024 10:37:56 AM Page 11 0.8333 0.012 0.003 0.000 0.004 0.8667 0.012 0.003 0.000 0.004 0.9000 0.012 0.003 0.000 0.004 0.9333 0.012 0.004 0.000 0.004 0.9667 0.012 0.004 0.000 0.004 1.0000 0.012 0.004 0.000 0.004 1.0333 0.012 0.004 0.000 0.004 1.0667 0.012 0.004 0.000 0.004 1.1000 0.012 0.004 0.000 0.004 1.1333 0.012 0.005 0.000 0.004 1.1667 0.012 0.005 0.000 0.004 1.2000 0.012 0.005 0.000 0.004 1.2333 0.012 0.005 0.000 0.004 1.2667 0.012 0.005 0.000 0.004 1.3000 0.012 0.005 0.000 0.004 1.3333 0.012 0.006 0.000 0.004 1.3667 0.012 0.006 0.000 0.004 1.4000 0.012 0.006 0.000 0.004 1.4333 0.012 0.006 0.000 0.004 1.4667 0.012 0.006 0.000 0.004 1.5000 0.012 0.006 0.000 0.004 1.5333 0.012 0.006 0.000 0.004 1.5667 0.012 0.007 0.000 0.004 1.6000 0.012 0.007 0.000 0.004 1.6333 0.012 0.007 0.000 0.004 1.6667 0.012 0.007 0.000 0.004 1.7000 0.012 0.007 0.000 0.004 1.7333 0.012 0.007 0.000 0.004 1.7667 0.012 0.007 0.000 0.004 1.8000 0.012 0.008 0.000 0.004 1.8333 0.012 0.008 0.000 0.004 1.8667 0.012 0.008 0.000 0.004 1.9000 0.012 0.008 0.000 0.004 1.9333 0.012 0.008 0.000 0.004 1.9667 0.012 0.008 0.000 0.004 2.0000 0.012 0.009 0.000 0.004 2.0333 0.012 0.009 0.032 0.004 2.0667 0.012 0.010 0.090 0.004 2.1000 0.012 0.010 0.160 0.004 2.1333 0.012 0.010 0.233 0.004 2.1667 0.012 0.011 0.297 0.004 2.2000 0.012 0.011 0.346 0.004 2.2333 0.012 0.012 0.378 0.004 2.2667 0.012 0.012 0.406 0.004 2.3000 0.012 0.012 0.431 0.004 2.3333 0.012 0.013 0.454 0.004 2.3667 0.012 0.013 0.476 0.004 2.4000 0.012 0.014 0.498 0.004 2.4333 0.012 0.014 0.518 0.004 2.4667 0.012 0.015 0.537 0.004 2.5000 0.012 0.015 0.556 0.004 2.5333 0.012 0.015 0.575 0.004 2.5667 0.012 0.016 0.592 0.004 2.6000 0.012 0.016 0.609 0.004 2.6333 0.012 0.017 0.626 0.004 2.6667 0.012 0.017 0.642 0.004 2.7000 0.012 0.017 0.658 0.004 2.7333 0.012 0.018 0.674 0.004 FINAL 6/19/2024 10:37:56 AM Page 12 2.7667 0.012 0.018 0.689 0.004 2.8000 0.012 0.019 0.704 0.004 2.8333 0.012 0.019 0.718 0.004 2.8667 0.012 0.019 0.733 0.004 2.9000 0.012 0.020 0.747 0.004 2.9333 0.012 0.020 0.760 0.004 2.9667 0.012 0.021 0.774 0.004 3.0000 0.012 0.021 0.787 0.004 FINAL 6/19/2024 10:37:56 AM Page 13 Gravel Trench Bed 2 Bottom Length:30.00 ft. Bottom Width:18.00 ft. Trench bottom slope 1:0 To 1 Trench Left side slope 0:0 To 1 Trench right side slope 2:0 To 1 Material thickness of first layer:1 Pour Space of material for first layer:0.35 Material thickness of second layer:0.5 Pour Space of material for second layer:0.39 Material thickness of third layer:0.5 Pour Space of material for third layer:0.35 Infiltration On Infiltration rate:0.35 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):31.281 Total Volume Through Riser (ac-ft.):2.943 Total Volume Through Facility (ac-ft.):34.225 Percent Infiltrated:91.4 Total Precip Applied to Facility:0 Total Evap From Facility:0 Discharge Structure Riser Height:2 ft. Riser Diameter:6 in. Element Flows To: Outlet 1 Outlet 2 Contech CMP 1 Gravel Trench Bed Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.012 0.000 0.000 0.000 0.0333 0.012 0.000 0.000 0.004 0.0667 0.012 0.000 0.000 0.004 0.1000 0.012 0.000 0.000 0.004 0.1333 0.012 0.000 0.000 0.004 0.1667 0.012 0.000 0.000 0.004 0.2000 0.012 0.000 0.000 0.004 0.2333 0.012 0.001 0.000 0.004 0.2667 0.012 0.001 0.000 0.004 0.3000 0.012 0.001 0.000 0.004 0.3333 0.012 0.001 0.000 0.004 0.3667 0.012 0.001 0.000 0.004 0.4000 0.012 0.001 0.000 0.004 0.4333 0.012 0.001 0.000 0.004 0.4667 0.012 0.002 0.000 0.004 0.5000 0.012 0.002 0.000 0.004 0.5333 0.012 0.002 0.000 0.004 0.5667 0.012 0.002 0.000 0.004 0.6000 0.012 0.002 0.000 0.004 0.6333 0.012 0.002 0.000 0.004 0.6667 0.012 0.002 0.000 0.004 0.7000 0.012 0.003 0.000 0.004 0.7333 0.012 0.003 0.000 0.004 0.7667 0.012 0.003 0.000 0.004 0.8000 0.012 0.003 0.000 0.004 FINAL 6/19/2024 10:37:56 AM Page 14 0.8333 0.012 0.003 0.000 0.004 0.8667 0.012 0.003 0.000 0.004 0.9000 0.012 0.003 0.000 0.004 0.9333 0.012 0.004 0.000 0.004 0.9667 0.012 0.004 0.000 0.004 1.0000 0.012 0.004 0.000 0.004 1.0333 0.012 0.004 0.000 0.004 1.0667 0.012 0.004 0.000 0.004 1.1000 0.012 0.004 0.000 0.004 1.1333 0.012 0.005 0.000 0.004 1.1667 0.012 0.005 0.000 0.004 1.2000 0.012 0.005 0.000 0.004 1.2333 0.012 0.005 0.000 0.004 1.2667 0.012 0.005 0.000 0.004 1.3000 0.012 0.005 0.000 0.004 1.3333 0.012 0.006 0.000 0.004 1.3667 0.012 0.006 0.000 0.004 1.4000 0.012 0.006 0.000 0.004 1.4333 0.012 0.006 0.000 0.004 1.4667 0.012 0.006 0.000 0.004 1.5000 0.012 0.006 0.000 0.004 1.5333 0.012 0.006 0.000 0.004 1.5667 0.012 0.007 0.000 0.004 1.6000 0.012 0.007 0.000 0.004 1.6333 0.012 0.007 0.000 0.004 1.6667 0.012 0.007 0.000 0.004 1.7000 0.012 0.007 0.000 0.004 1.7333 0.012 0.007 0.000 0.004 1.7667 0.012 0.007 0.000 0.004 1.8000 0.012 0.008 0.000 0.004 1.8333 0.012 0.008 0.000 0.004 1.8667 0.012 0.008 0.000 0.004 1.9000 0.012 0.008 0.000 0.004 1.9333 0.012 0.008 0.000 0.004 1.9667 0.012 0.008 0.000 0.004 2.0000 0.012 0.009 0.000 0.004 2.0333 0.012 0.009 0.032 0.004 2.0667 0.012 0.010 0.090 0.004 2.1000 0.012 0.010 0.160 0.004 2.1333 0.012 0.010 0.233 0.004 2.1667 0.012 0.011 0.297 0.004 2.2000 0.012 0.011 0.346 0.004 2.2333 0.012 0.012 0.378 0.004 2.2667 0.012 0.012 0.406 0.004 2.3000 0.012 0.012 0.431 0.004 2.3333 0.012 0.013 0.454 0.004 2.3667 0.012 0.013 0.476 0.004 2.4000 0.012 0.014 0.498 0.004 2.4333 0.012 0.014 0.518 0.004 2.4667 0.012 0.015 0.537 0.004 2.5000 0.012 0.015 0.556 0.004 2.5333 0.012 0.015 0.575 0.004 2.5667 0.012 0.016 0.592 0.004 2.6000 0.012 0.016 0.609 0.004 2.6333 0.012 0.017 0.626 0.004 2.6667 0.012 0.017 0.642 0.004 2.7000 0.012 0.017 0.658 0.004 2.7333 0.012 0.018 0.674 0.004 FINAL 6/19/2024 10:37:56 AM Page 15 2.7667 0.012 0.018 0.689 0.004 2.8000 0.012 0.019 0.704 0.004 2.8333 0.012 0.019 0.718 0.004 2.8667 0.012 0.019 0.733 0.004 2.9000 0.012 0.020 0.747 0.004 2.9333 0.012 0.020 0.760 0.004 2.9667 0.012 0.021 0.774 0.004 3.0000 0.012 0.021 0.787 0.004 FINAL 6/19/2024 10:37:56 AM Page 16 Gravel Trench Bed 3 Bottom Length:30.00 ft. Bottom Width:18.00 ft. Trench bottom slope 1:0 To 1 Trench Left side slope 0:0 To 1 Trench right side slope 2:0 To 1 Material thickness of first layer:1 Pour Space of material for first layer:0.35 Material thickness of second layer:0.5 Pour Space of material for second layer:0.39 Material thickness of third layer:0.5 Pour Space of material for third layer:0.35 Infiltration On Infiltration rate:0.35 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):31.281 Total Volume Through Riser (ac-ft.):2.943 Total Volume Through Facility (ac-ft.):34.225 Percent Infiltrated:91.4 Total Precip Applied to Facility:0 Total Evap From Facility:0 Discharge Structure Riser Height:2 ft. Riser Diameter:6 in. Element Flows To: Outlet 1 Outlet 2 Contech CMP 1 Gravel Trench Bed Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.012 0.000 0.000 0.000 0.0333 0.012 0.000 0.000 0.004 0.0667 0.012 0.000 0.000 0.004 0.1000 0.012 0.000 0.000 0.004 0.1333 0.012 0.000 0.000 0.004 0.1667 0.012 0.000 0.000 0.004 0.2000 0.012 0.000 0.000 0.004 0.2333 0.012 0.001 0.000 0.004 0.2667 0.012 0.001 0.000 0.004 0.3000 0.012 0.001 0.000 0.004 0.3333 0.012 0.001 0.000 0.004 0.3667 0.012 0.001 0.000 0.004 0.4000 0.012 0.001 0.000 0.004 0.4333 0.012 0.001 0.000 0.004 0.4667 0.012 0.002 0.000 0.004 0.5000 0.012 0.002 0.000 0.004 0.5333 0.012 0.002 0.000 0.004 0.5667 0.012 0.002 0.000 0.004 0.6000 0.012 0.002 0.000 0.004 0.6333 0.012 0.002 0.000 0.004 0.6667 0.012 0.002 0.000 0.004 0.7000 0.012 0.003 0.000 0.004 0.7333 0.012 0.003 0.000 0.004 0.7667 0.012 0.003 0.000 0.004 0.8000 0.012 0.003 0.000 0.004 FINAL 6/19/2024 10:37:56 AM Page 17 0.8333 0.012 0.003 0.000 0.004 0.8667 0.012 0.003 0.000 0.004 0.9000 0.012 0.003 0.000 0.004 0.9333 0.012 0.004 0.000 0.004 0.9667 0.012 0.004 0.000 0.004 1.0000 0.012 0.004 0.000 0.004 1.0333 0.012 0.004 0.000 0.004 1.0667 0.012 0.004 0.000 0.004 1.1000 0.012 0.004 0.000 0.004 1.1333 0.012 0.005 0.000 0.004 1.1667 0.012 0.005 0.000 0.004 1.2000 0.012 0.005 0.000 0.004 1.2333 0.012 0.005 0.000 0.004 1.2667 0.012 0.005 0.000 0.004 1.3000 0.012 0.005 0.000 0.004 1.3333 0.012 0.006 0.000 0.004 1.3667 0.012 0.006 0.000 0.004 1.4000 0.012 0.006 0.000 0.004 1.4333 0.012 0.006 0.000 0.004 1.4667 0.012 0.006 0.000 0.004 1.5000 0.012 0.006 0.000 0.004 1.5333 0.012 0.006 0.000 0.004 1.5667 0.012 0.007 0.000 0.004 1.6000 0.012 0.007 0.000 0.004 1.6333 0.012 0.007 0.000 0.004 1.6667 0.012 0.007 0.000 0.004 1.7000 0.012 0.007 0.000 0.004 1.7333 0.012 0.007 0.000 0.004 1.7667 0.012 0.007 0.000 0.004 1.8000 0.012 0.008 0.000 0.004 1.8333 0.012 0.008 0.000 0.004 1.8667 0.012 0.008 0.000 0.004 1.9000 0.012 0.008 0.000 0.004 1.9333 0.012 0.008 0.000 0.004 1.9667 0.012 0.008 0.000 0.004 2.0000 0.012 0.009 0.000 0.004 2.0333 0.012 0.009 0.032 0.004 2.0667 0.012 0.010 0.090 0.004 2.1000 0.012 0.010 0.160 0.004 2.1333 0.012 0.010 0.233 0.004 2.1667 0.012 0.011 0.297 0.004 2.2000 0.012 0.011 0.346 0.004 2.2333 0.012 0.012 0.378 0.004 2.2667 0.012 0.012 0.406 0.004 2.3000 0.012 0.012 0.431 0.004 2.3333 0.012 0.013 0.454 0.004 2.3667 0.012 0.013 0.476 0.004 2.4000 0.012 0.014 0.498 0.004 2.4333 0.012 0.014 0.518 0.004 2.4667 0.012 0.015 0.537 0.004 2.5000 0.012 0.015 0.556 0.004 2.5333 0.012 0.015 0.575 0.004 2.5667 0.012 0.016 0.592 0.004 2.6000 0.012 0.016 0.609 0.004 2.6333 0.012 0.017 0.626 0.004 2.6667 0.012 0.017 0.642 0.004 2.7000 0.012 0.017 0.658 0.004 2.7333 0.012 0.018 0.674 0.004 FINAL 6/19/2024 10:37:56 AM Page 18 2.7667 0.012 0.018 0.689 0.004 2.8000 0.012 0.019 0.704 0.004 2.8333 0.012 0.019 0.718 0.004 2.8667 0.012 0.019 0.733 0.004 2.9000 0.012 0.020 0.747 0.004 2.9333 0.012 0.020 0.760 0.004 2.9667 0.012 0.021 0.774 0.004 3.0000 0.012 0.021 0.787 0.004 FINAL 6/19/2024 10:37:56 AM Page 19 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.7 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.32 Total Impervious Area:0.38 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.027346 5 year 0.045084 10 year 0.058549 25 year 0.077367 50 year 0.092629 100 year 0.108912 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.020322 5 year 0.030535 10 year 0.038461 25 year 0.049879 50 year 0.05946 100 year 0.070007 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.033 0.020 1950 0.039 0.025 1951 0.056 0.038 1952 0.019 0.015 1953 0.016 0.013 1954 0.023 0.013 1955 0.035 0.024 1956 0.029 0.022 1957 0.026 0.025 1958 0.026 0.018 FINAL 6/19/2024 10:38:33 AM Page 20 1959 0.023 0.015 1960 0.044 0.033 1961 0.022 0.021 1962 0.015 0.010 1963 0.021 0.014 1964 0.027 0.013 1965 0.020 0.015 1966 0.018 0.012 1967 0.042 0.027 1968 0.024 0.019 1969 0.023 0.019 1970 0.020 0.017 1971 0.025 0.021 1972 0.043 0.027 1973 0.020 0.013 1974 0.023 0.014 1975 0.033 0.028 1976 0.023 0.018 1977 0.008 0.012 1978 0.019 0.018 1979 0.012 0.020 1980 0.061 0.027 1981 0.018 0.018 1982 0.042 0.043 1983 0.029 0.017 1984 0.018 0.011 1985 0.011 0.014 1986 0.046 0.033 1987 0.042 0.032 1988 0.018 0.013 1989 0.011 0.016 1990 0.117 0.054 1991 0.053 0.045 1992 0.022 0.013 1993 0.021 0.013 1994 0.009 0.010 1995 0.028 0.020 1996 0.067 0.034 1997 0.053 0.039 1998 0.019 0.020 1999 0.073 0.027 2000 0.020 0.016 2001 0.005 0.015 2002 0.028 0.033 2003 0.039 0.014 2004 0.045 0.063 2005 0.030 0.026 2006 0.031 0.021 2007 0.087 0.051 2008 0.092 0.065 2009 0.041 0.030 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1171 0.0651 2 0.0921 0.0633 3 0.0866 0.0537 FINAL 6/19/2024 10:38:33 AM Page 21 4 0.0729 0.0513 5 0.0668 0.0451 6 0.0612 0.0432 7 0.0562 0.0393 8 0.0528 0.0376 9 0.0527 0.0340 10 0.0457 0.0330 11 0.0451 0.0329 12 0.0436 0.0326 13 0.0429 0.0317 14 0.0425 0.0299 15 0.0420 0.0277 16 0.0416 0.0272 17 0.0414 0.0271 18 0.0391 0.0270 19 0.0389 0.0265 20 0.0355 0.0260 21 0.0335 0.0250 22 0.0326 0.0246 23 0.0307 0.0241 24 0.0296 0.0220 25 0.0292 0.0211 26 0.0289 0.0210 27 0.0284 0.0208 28 0.0284 0.0204 29 0.0268 0.0204 30 0.0265 0.0200 31 0.0261 0.0197 32 0.0249 0.0193 33 0.0243 0.0193 34 0.0234 0.0179 35 0.0232 0.0179 36 0.0230 0.0179 37 0.0229 0.0179 38 0.0225 0.0173 39 0.0220 0.0166 40 0.0218 0.0161 41 0.0214 0.0156 42 0.0213 0.0154 43 0.0204 0.0152 44 0.0203 0.0150 45 0.0199 0.0150 46 0.0197 0.0141 47 0.0195 0.0140 48 0.0188 0.0139 49 0.0188 0.0138 50 0.0184 0.0135 51 0.0181 0.0132 52 0.0178 0.0131 53 0.0177 0.0130 54 0.0159 0.0128 55 0.0148 0.0127 56 0.0121 0.0125 57 0.0113 0.0125 58 0.0108 0.0117 59 0.0087 0.0111 60 0.0080 0.0104 61 0.0053 0.0100 FINAL 6/19/2024 10:38:33 AM Page 22 FINAL 6/19/2024 10:38:33 AM Page 23 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0137 18450 3559 19 Pass 0.0145 16091 3189 19 Pass 0.0153 14328 2851 19 Pass 0.0161 12694 2545 20 Pass 0.0169 11182 2254 20 Pass 0.0177 9882 1966 19 Pass 0.0185 8825 1729 19 Pass 0.0193 7843 1561 19 Pass 0.0201 7005 1399 19 Pass 0.0209 6288 1270 20 Pass 0.0216 5679 1156 20 Pass 0.0224 5172 1029 19 Pass 0.0232 4697 927 19 Pass 0.0240 4278 843 19 Pass 0.0248 3910 759 19 Pass 0.0256 3527 699 19 Pass 0.0264 3183 629 19 Pass 0.0272 2862 570 19 Pass 0.0280 2594 521 20 Pass 0.0288 2353 482 20 Pass 0.0296 2138 452 21 Pass 0.0304 1951 416 21 Pass 0.0312 1796 396 22 Pass 0.0320 1669 369 22 Pass 0.0328 1514 349 23 Pass 0.0336 1343 326 24 Pass 0.0344 1223 306 25 Pass 0.0352 1123 287 25 Pass 0.0360 1042 268 25 Pass 0.0368 969 250 25 Pass 0.0376 910 232 25 Pass 0.0384 838 213 25 Pass 0.0392 766 194 25 Pass 0.0400 704 181 25 Pass 0.0408 635 171 26 Pass 0.0416 570 155 27 Pass 0.0424 488 144 29 Pass 0.0432 425 131 30 Pass 0.0440 376 127 33 Pass 0.0448 341 119 34 Pass 0.0456 307 112 36 Pass 0.0464 270 103 38 Pass 0.0472 235 93 39 Pass 0.0480 196 88 44 Pass 0.0488 171 77 45 Pass 0.0496 145 73 50 Pass 0.0504 125 68 54 Pass 0.0512 107 63 58 Pass 0.0520 95 57 60 Pass 0.0528 84 56 66 Pass 0.0535 71 49 69 Pass 0.0543 61 45 73 Pass 0.0551 55 36 65 Pass FINAL 6/19/2024 10:38:33 AM Page 24 0.0559 45 28 62 Pass 0.0567 40 27 67 Pass 0.0575 37 23 62 Pass 0.0583 35 22 62 Pass 0.0591 29 17 58 Pass 0.0599 25 11 44 Pass 0.0607 22 6 27 Pass 0.0615 17 3 17 Pass 0.0623 15 3 20 Pass 0.0631 11 2 18 Pass 0.0639 9 1 11 Pass 0.0647 8 1 12 Pass 0.0655 8 0 0 Pass 0.0663 8 0 0 Pass 0.0671 7 0 0 Pass 0.0679 7 0 0 Pass 0.0687 7 0 0 Pass 0.0695 7 0 0 Pass 0.0703 7 0 0 Pass 0.0711 7 0 0 Pass 0.0719 7 0 0 Pass 0.0727 6 0 0 Pass 0.0735 5 0 0 Pass 0.0743 5 0 0 Pass 0.0751 5 0 0 Pass 0.0759 4 0 0 Pass 0.0767 4 0 0 Pass 0.0775 4 0 0 Pass 0.0783 4 0 0 Pass 0.0791 4 0 0 Pass 0.0799 4 0 0 Pass 0.0807 4 0 0 Pass 0.0815 4 0 0 Pass 0.0823 4 0 0 Pass 0.0831 4 0 0 Pass 0.0839 3 0 0 Pass 0.0847 3 0 0 Pass 0.0855 3 0 0 Pass 0.0862 3 0 0 Pass 0.0870 2 0 0 Pass 0.0878 2 0 0 Pass 0.0886 2 0 0 Pass 0.0894 2 0 0 Pass 0.0902 2 0 0 Pass 0.0910 2 0 0 Pass 0.0918 2 0 0 Pass 0.0926 1 0 0 Pass FINAL 6/19/2024 10:38:33 AM Page 25 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. FINAL 6/19/2024 10:38:33 AM Page 26 LID Report FINAL 6/19/2024 10:39:00 AM Page 27 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. FINAL 6/19/2024 10:39:00 AM Page 28 Appendix Predeveloped Schematic FINAL 6/19/2024 10:39:02 AM Page 29 Mitigated Schematic WWHM2012 PROJECT REPORT Wetland Hydration 6/19/2024 11:57:47 AM Page 2 General Model Information Project Name:Wetland Hydration Site Name: Site Address: City: Report Date:6/19/2024 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.167 Version Date:2019/09/13 Version:4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year Wetland Hydration 6/19/2024 11:57:47 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.064 Pervious Total 0.064 Impervious Land Use acre Impervious Total 0 Basin Total 0.064 Element Flows To: Surface Interflow Groundwater Wetland Hydration 6/19/2024 11:57:47 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.064 Pervious Total 0.064 Impervious Land Use acre Impervious Total 0 Basin Total 0.064 Element Flows To: Surface Interflow Groundwater Wetland Hydration 6/19/2024 11:57:48 AM Page 5 Routing Elements Predeveloped Routing Wetland Hydration 6/19/2024 11:57:48 AM Page 6 Mitigated Routing Wetland Hydration 6/19/2024 11:57:48 AM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.064 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.064 Total Impervious Area:0 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.008296 5 year 0.014258 10 year 0.018808 25 year 0.025156 50 year 0.030279 100 year 0.035714 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.008296 5 year 0.014258 10 year 0.018808 25 year 0.025156 50 year 0.030279 100 year 0.035714 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.016 0.016 1950 0.017 0.017 1951 0.009 0.009 1952 0.004 0.004 1953 0.003 0.003 1954 0.007 0.007 1955 0.006 0.006 1956 0.007 0.007 1957 0.010 0.010 1958 0.005 0.005 Wetland Hydration 6/19/2024 11:58:27 AM Page 8 1959 0.004 0.004 1960 0.009 0.009 1961 0.008 0.008 1962 0.002 0.002 1963 0.009 0.009 1964 0.007 0.007 1965 0.011 0.011 1966 0.005 0.005 1967 0.017 0.017 1968 0.010 0.010 1969 0.011 0.011 1970 0.008 0.008 1971 0.010 0.010 1972 0.016 0.016 1973 0.003 0.003 1974 0.009 0.009 1975 0.011 0.011 1976 0.007 0.007 1977 0.008 0.008 1978 0.007 0.007 1979 0.004 0.004 1980 0.019 0.019 1981 0.008 0.008 1982 0.018 0.018 1983 0.008 0.008 1984 0.006 0.006 1985 0.008 0.008 1986 0.008 0.008 1987 0.007 0.007 1988 0.002 0.002 1989 0.002 0.002 1990 0.032 0.032 1991 0.023 0.023 1992 0.005 0.005 1993 0.003 0.003 1994 0.002 0.002 1995 0.005 0.005 1996 0.014 0.014 1997 0.010 0.010 1998 0.007 0.007 1999 0.024 0.024 2000 0.009 0.009 2001 0.004 0.004 2002 0.015 0.015 2003 0.012 0.012 2004 0.020 0.020 2005 0.008 0.008 2006 0.008 0.008 2007 0.030 0.030 2008 0.022 0.022 2009 0.012 0.012 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0324 0.0324 2 0.0301 0.0301 3 0.0238 0.0238 Wetland Hydration 6/19/2024 11:58:27 AM Page 9 4 0.0228 0.0228 5 0.0225 0.0225 6 0.0202 0.0202 7 0.0187 0.0187 8 0.0183 0.0183 9 0.0168 0.0168 10 0.0168 0.0168 11 0.0165 0.0165 12 0.0164 0.0164 13 0.0154 0.0154 14 0.0140 0.0140 15 0.0121 0.0121 16 0.0121 0.0121 17 0.0110 0.0110 18 0.0107 0.0107 19 0.0105 0.0105 20 0.0104 0.0104 21 0.0102 0.0102 22 0.0101 0.0101 23 0.0100 0.0100 24 0.0092 0.0092 25 0.0091 0.0091 26 0.0089 0.0089 27 0.0087 0.0087 28 0.0087 0.0087 29 0.0083 0.0083 30 0.0083 0.0083 31 0.0082 0.0082 32 0.0080 0.0080 33 0.0078 0.0078 34 0.0078 0.0078 35 0.0078 0.0078 36 0.0077 0.0077 37 0.0075 0.0075 38 0.0074 0.0074 39 0.0074 0.0074 40 0.0073 0.0073 41 0.0071 0.0071 42 0.0067 0.0067 43 0.0066 0.0066 44 0.0065 0.0065 45 0.0064 0.0064 46 0.0055 0.0055 47 0.0055 0.0055 48 0.0055 0.0055 49 0.0049 0.0049 50 0.0047 0.0047 51 0.0042 0.0042 52 0.0039 0.0039 53 0.0037 0.0037 54 0.0036 0.0036 55 0.0031 0.0031 56 0.0030 0.0030 57 0.0029 0.0029 58 0.0025 0.0025 59 0.0024 0.0024 60 0.0022 0.0022 61 0.0021 0.0021 Wetland Hydration 6/19/2024 11:58:27 AM Page 10 Wetland Hydration 6/19/2024 11:58:27 AM Page 11 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0041 1421 1421 100 Pass 0.0044 1138 1138 100 Pass 0.0047 904 904 100 Pass 0.0049 706 706 100 Pass 0.0052 581 581 100 Pass 0.0055 486 486 100 Pass 0.0057 412 412 100 Pass 0.0060 365 365 100 Pass 0.0063 323 323 100 Pass 0.0065 292 292 100 Pass 0.0068 266 266 100 Pass 0.0071 242 242 100 Pass 0.0073 222 222 100 Pass 0.0076 209 209 100 Pass 0.0078 198 198 100 Pass 0.0081 183 183 100 Pass 0.0084 163 163 100 Pass 0.0086 149 149 100 Pass 0.0089 143 143 100 Pass 0.0092 129 129 100 Pass 0.0094 121 121 100 Pass 0.0097 113 113 100 Pass 0.0100 109 109 100 Pass 0.0102 100 100 100 Pass 0.0105 95 95 100 Pass 0.0107 90 90 100 Pass 0.0110 83 83 100 Pass 0.0113 82 82 100 Pass 0.0115 79 79 100 Pass 0.0118 75 75 100 Pass 0.0121 74 74 100 Pass 0.0123 65 65 100 Pass 0.0126 62 62 100 Pass 0.0129 59 59 100 Pass 0.0131 58 58 100 Pass 0.0134 55 55 100 Pass 0.0137 51 51 100 Pass 0.0139 50 50 100 Pass 0.0142 46 46 100 Pass 0.0144 46 46 100 Pass 0.0147 45 45 100 Pass 0.0150 42 42 100 Pass 0.0152 40 40 100 Pass 0.0155 36 36 100 Pass 0.0158 35 35 100 Pass 0.0160 35 35 100 Pass 0.0163 35 35 100 Pass 0.0166 31 31 100 Pass 0.0168 29 29 100 Pass 0.0171 27 27 100 Pass 0.0173 25 25 100 Pass 0.0176 24 24 100 Pass 0.0179 23 23 100 Pass Wetland Hydration 6/19/2024 11:58:27 AM Page 12 0.0181 22 22 100 Pass 0.0184 18 18 100 Pass 0.0187 17 17 100 Pass 0.0189 14 14 100 Pass 0.0192 13 13 100 Pass 0.0195 13 13 100 Pass 0.0197 13 13 100 Pass 0.0200 13 13 100 Pass 0.0202 11 11 100 Pass 0.0205 9 9 100 Pass 0.0208 9 9 100 Pass 0.0210 9 9 100 Pass 0.0213 9 9 100 Pass 0.0216 9 9 100 Pass 0.0218 8 8 100 Pass 0.0221 8 8 100 Pass 0.0224 7 7 100 Pass 0.0226 5 5 100 Pass 0.0229 4 4 100 Pass 0.0232 4 4 100 Pass 0.0234 4 4 100 Pass 0.0237 4 4 100 Pass 0.0239 2 2 100 Pass 0.0242 2 2 100 Pass 0.0245 2 2 100 Pass 0.0247 2 2 100 Pass 0.0250 2 2 100 Pass 0.0253 2 2 100 Pass 0.0255 2 2 100 Pass 0.0258 2 2 100 Pass 0.0261 2 2 100 Pass 0.0263 2 2 100 Pass 0.0266 2 2 100 Pass 0.0268 2 2 100 Pass 0.0271 2 2 100 Pass 0.0274 2 2 100 Pass 0.0276 2 2 100 Pass 0.0279 2 2 100 Pass 0.0282 2 2 100 Pass 0.0284 2 2 100 Pass 0.0287 2 2 100 Pass 0.0290 2 2 100 Pass 0.0292 2 2 100 Pass 0.0295 2 2 100 Pass 0.0298 2 2 100 Pass 0.0300 2 2 100 Pass 0.0303 1 1 100 Pass Wetland Hydration 6/19/2024 11:58:27 AM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Wetland Hydration 6/19/2024 11:58:27 AM Page 14 Wetland Input Volumes - Percent - Predeveloped - Mitigated Wetlands Input Volume for POC 1 Average Annual Volume (acft) Series 1: 501 POC 1 Predeveloped flow Series 2: 801 POC 1 Mitigated flow Month Series 1 Series 2 Percent Pass/Fail Jan 0.0226 0.0226 100.0 Pass Feb 0.0153 0.0153 100.0 Pass Mar 0.0120 0.0120 100.0 Pass Apr 0.0061 0.0061 100.0 Pass May 0.0020 0.0020 100.0 Pass Jun 0.0016 0.0016 100.0 Pass Jul 0.0003 0.0003 100.0 Pass Aug 0.0008 0.0008 100.0 Pass Sep 0.0014 0.0014 100.0 Pass Oct 0.0063 0.0063 100.0 Pass Nov 0.0198 0.0198 100.0 Pass Dec 0.0225 0.0225 100.0 Pass Day Predevel Mitigated Percent Pass/Fail Jan1 0.0008 0.0008 100.0 Pass 2 0.0008 0.0008 100.0 Pass 3 0.0007 0.0007 100.0 Pass 4 0.0008 0.0008 100.0 Pass 5 0.0008 0.0008 100.0 Pass 6 0.0009 0.0009 100.0 Pass 7 0.0008 0.0008 100.0 Pass 8 0.0008 0.0008 100.0 Pass 9 0.0006 0.0006 100.0 Pass 10 0.0006 0.0006 100.0 Pass 11 0.0006 0.0006 100.0 Pass 12 0.0007 0.0007 100.0 Pass 13 0.0008 0.0008 100.0 Pass 14 0.0009 0.0009 100.0 Pass Wetland Hydration 6/19/2024 11:58:33 AM Page 15 15 0.0008 0.0008 100.0 Pass 16 0.0008 0.0008 100.0 Pass 17 0.0007 0.0007 100.0 Pass 18 0.0008 0.0008 100.0 Pass 19 0.0008 0.0008 100.0 Pass 20 0.0007 0.0007 100.0 Pass 21 0.0006 0.0006 100.0 Pass 22 0.0007 0.0007 100.0 Pass 23 0.0008 0.0008 100.0 Pass 24 0.0008 0.0008 100.0 Pass 25 0.0006 0.0006 100.0 Pass 26 0.0006 0.0006 100.0 Pass 27 0.0006 0.0006 100.0 Pass 28 0.0006 0.0006 100.0 Pass 29 0.0007 0.0007 100.0 Pass 30 0.0007 0.0007 100.0 Pass 31 0.0007 0.0007 100.0 Pass Feb1 0.0006 0.0006 100.0 Pass 2 0.0005 0.0005 100.0 Pass 3 0.0005 0.0005 100.0 Pass 4 0.0004 0.0004 100.0 Pass 5 0.0005 0.0005 100.0 Pass 6 0.0005 0.0005 100.0 Pass 7 0.0007 0.0007 100.0 Pass 8 0.0007 0.0007 100.0 Pass 9 0.0005 0.0005 100.0 Pass 10 0.0004 0.0004 100.0 Pass 11 0.0005 0.0005 100.0 Pass 12 0.0005 0.0005 100.0 Pass 13 0.0005 0.0005 100.0 Pass 14 0.0005 0.0005 100.0 Pass 15 0.0006 0.0006 100.0 Pass 16 0.0006 0.0006 100.0 Pass 17 0.0006 0.0006 100.0 Pass 18 0.0007 0.0007 100.0 Pass 19 0.0006 0.0006 100.0 Pass 20 0.0005 0.0005 100.0 Pass 21 0.0005 0.0005 100.0 Pass 22 0.0005 0.0005 100.0 Pass 23 0.0005 0.0005 100.0 Pass 24 0.0005 0.0005 100.0 Pass 25 0.0005 0.0005 100.0 Pass 26 0.0005 0.0005 100.0 Pass 27 0.0005 0.0005 100.0 Pass 28 0.0005 0.0005 100.0 Pass 29 0.0004 0.0004 100.0 Pass Mar1 0.0004 0.0004 100.0 Pass 2 0.0005 0.0005 100.0 Pass 3 0.0005 0.0005 100.0 Pass 4 0.0005 0.0005 100.0 Pass 5 0.0004 0.0004 100.0 Pass 6 0.0004 0.0004 100.0 Pass 7 0.0003 0.0003 100.0 Pass 8 0.0004 0.0004 100.0 Pass 9 0.0005 0.0005 100.0 Pass 10 0.0005 0.0005 100.0 Pass 11 0.0005 0.0005 100.0 Pass 12 0.0005 0.0005 100.0 Pass Wetland Hydration 6/19/2024 11:58:33 AM Page 16 13 0.0004 0.0004 100.0 Pass 14 0.0004 0.0004 100.0 Pass 15 0.0004 0.0004 100.0 Pass 16 0.0004 0.0004 100.0 Pass 17 0.0004 0.0004 100.0 Pass 18 0.0004 0.0004 100.0 Pass 19 0.0003 0.0003 100.0 Pass 20 0.0003 0.0003 100.0 Pass 21 0.0003 0.0003 100.0 Pass 22 0.0004 0.0004 100.0 Pass 23 0.0004 0.0004 100.0 Pass 24 0.0004 0.0004 100.0 Pass 25 0.0003 0.0003 100.0 Pass 26 0.0003 0.0003 100.0 Pass 27 0.0003 0.0003 100.0 Pass 28 0.0003 0.0003 100.0 Pass 29 0.0003 0.0003 100.0 Pass 30 0.0003 0.0003 100.0 Pass 31 0.0002 0.0002 100.0 Pass Apr1 0.0002 0.0002 100.0 Pass 2 0.0002 0.0002 100.0 Pass 3 0.0003 0.0003 100.0 Pass 4 0.0003 0.0003 100.0 Pass 5 0.0003 0.0003 100.0 Pass 6 0.0002 0.0002 100.0 Pass 7 0.0002 0.0002 100.0 Pass 8 0.0003 0.0003 100.0 Pass 9 0.0002 0.0002 100.0 Pass 10 0.0002 0.0002 100.0 Pass 11 0.0002 0.0002 100.0 Pass 12 0.0002 0.0002 100.0 Pass 13 0.0002 0.0002 100.0 Pass 14 0.0002 0.0002 100.0 Pass 15 0.0002 0.0002 100.0 Pass 16 0.0003 0.0003 100.0 Pass 17 0.0002 0.0002 100.0 Pass 18 0.0002 0.0002 100.0 Pass 19 0.0003 0.0003 100.0 Pass 20 0.0002 0.0002 100.0 Pass 21 0.0001 0.0001 100.0 Pass 22 0.0002 0.0002 100.0 Pass 23 0.0002 0.0002 100.0 Pass 24 0.0001 0.0001 100.0 Pass 25 0.0001 0.0001 100.0 Pass 26 0.0001 0.0001 100.0 Pass 27 0.0001 0.0001 100.0 Pass 28 0.0001 0.0001 100.0 Pass 29 0.0002 0.0002 100.0 Pass 30 0.0001 0.0001 100.0 Pass May1 0.0001 0.0001 100.0 Pass 2 0.0001 0.0001 100.0 Pass 3 0.0001 0.0001 100.0 Pass 4 0.0001 0.0001 100.0 Pass 5 0.0001 0.0001 100.0 Pass 6 0.0001 0.0001 100.0 Pass 7 0.0001 0.0001 100.0 Pass 8 0.0001 0.0001 100.0 Pass 9 0.0001 0.0001 100.0 Pass Wetland Hydration 6/19/2024 11:58:33 AM Page 17 10 0.0001 0.0001 100.0 Pass 11 0.0000 0.0000 100.0 Pass 12 0.0001 0.0001 100.0 Pass 13 0.0001 0.0001 100.0 Pass 14 0.0001 0.0001 100.0 Pass 15 0.0001 0.0001 100.0 Pass 16 0.0000 0.0000 100.0 Pass 17 0.0000 0.0000 100.0 Pass 18 0.0001 0.0001 100.0 Pass 19 0.0001 0.0001 100.0 Pass 20 0.0000 0.0000 100.0 Pass 21 0.0000 0.0000 100.0 Pass 22 0.0000 0.0000 100.0 Pass 23 0.0000 0.0000 100.0 Pass 24 0.0000 0.0000 100.0 Pass 25 0.0000 0.0000 100.0 Pass 26 0.0000 0.0000 100.0 Pass 27 0.0001 0.0001 100.0 Pass 28 0.0001 0.0001 100.0 Pass 29 0.0001 0.0001 100.0 Pass 30 0.0001 0.0001 100.0 Pass 31 0.0001 0.0001 100.0 Pass Jun1 0.0001 0.0001 100.0 Pass 2 0.0001 0.0001 100.0 Pass 3 0.0001 0.0001 100.0 Pass 4 0.0001 0.0001 100.0 Pass 5 0.0001 0.0001 100.0 Pass 6 0.0001 0.0001 100.0 Pass 7 0.0001 0.0001 100.0 Pass 8 0.0001 0.0001 100.0 Pass 9 0.0001 0.0001 100.0 Pass 10 0.0001 0.0001 100.0 Pass 11 0.0001 0.0001 100.0 Pass 12 0.0000 0.0000 100.0 Pass 13 0.0000 0.0000 100.0 Pass 14 0.0000 0.0000 100.0 Pass 15 0.0000 0.0000 100.0 Pass 16 0.0000 0.0000 100.0 Pass 17 0.0000 0.0000 100.0 Pass 18 0.0000 0.0000 100.0 Pass 19 0.0000 0.0000 100.0 Pass 20 0.0000 0.0000 100.0 Pass 21 0.0001 0.0001 100.0 Pass 22 0.0000 0.0000 100.0 Pass 23 0.0001 0.0001 100.0 Pass 24 0.0001 0.0001 100.0 Pass 25 0.0000 0.0000 100.0 Pass 26 0.0000 0.0000 100.0 Pass 27 0.0000 0.0000 100.0 Pass 28 0.0000 0.0000 100.0 Pass 29 0.0000 0.0000 100.0 Pass 30 0.0000 0.0000 100.0 Pass Jul1 0.0000 0.0000 100.0 Pass 2 0.0000 0.0000 100.0 Pass 3 0.0000 0.0000 100.0 Pass 4 0.0000 0.0000 100.0 Pass 5 0.0000 0.0000 100.0 Pass 6 0.0000 0.0000 100.0 Pass Wetland Hydration 6/19/2024 11:58:33 AM Page 18 7 0.0000 0.0000 100.0 Pass 8 0.0000 0.0000 100.0 Pass 9 0.0000 0.0000 100.0 Pass 10 0.0000 0.0000 100.0 Pass 11 0.0000 0.0000 100.0 Pass 12 0.0000 0.0000 100.0 Pass 13 0.0000 0.0000 100.0 Pass 14 0.0000 0.0000 100.0 Pass 15 0.0000 0.0000 100.0 Pass 16 0.0000 0.0000 100.0 Pass 17 0.0000 0.0000 100.0 Pass 18 0.0000 0.0000 100.0 Pass 19 0.0000 0.0000 100.0 Pass 20 0.0000 0.0000 100.0 Pass 21 0.0000 0.0000 100.0 Pass 22 0.0000 0.0000 100.0 Pass 23 0.0000 0.0000 100.0 Pass 24 0.0000 0.0000 100.0 Pass 25 0.0000 0.0000 100.0 Pass 26 0.0000 0.0000 100.0 Pass 27 0.0000 0.0000 100.0 Pass 28 0.0000 0.0000 100.0 Pass 29 0.0000 0.0000 100.0 Pass 30 0.0000 0.0000 100.0 Pass 31 0.0000 0.0000 100.0 Pass Aug1 0.0000 0.0000 100.0 Pass 2 0.0000 0.0000 100.0 Pass 3 0.0000 0.0000 100.0 Pass 4 0.0000 0.0000 100.0 Pass 5 0.0000 0.0000 100.0 Pass 6 0.0000 0.0000 100.0 Pass 7 0.0000 0.0000 100.0 Pass 8 0.0000 0.0000 100.0 Pass 9 0.0000 0.0000 100.0 Pass 10 0.0000 0.0000 100.0 Pass 11 0.0000 0.0000 100.0 Pass 12 0.0000 0.0000 100.0 Pass 13 0.0000 0.0000 100.0 Pass 14 0.0000 0.0000 100.0 Pass 15 0.0000 0.0000 100.0 Pass 16 0.0000 0.0000 100.0 Pass 17 0.0000 0.0000 100.0 Pass 18 0.0000 0.0000 100.0 Pass 19 0.0000 0.0000 100.0 Pass 20 0.0000 0.0000 100.0 Pass 21 0.0000 0.0000 100.0 Pass 22 0.0001 0.0001 100.0 Pass 23 0.0001 0.0001 100.0 Pass 24 0.0001 0.0001 100.0 Pass 25 0.0001 0.0001 100.0 Pass 26 0.0001 0.0001 100.0 Pass 27 0.0000 0.0000 100.0 Pass 28 0.0000 0.0000 100.0 Pass 29 0.0001 0.0001 100.0 Pass 30 0.0000 0.0000 100.0 Pass 31 0.0000 0.0000 100.0 Pass Sep1 0.0000 0.0000 100.0 Pass 2 0.0000 0.0000 100.0 Pass Wetland Hydration 6/19/2024 11:58:33 AM Page 19 3 0.0000 0.0000 100.0 Pass 4 0.0000 0.0000 100.0 Pass 5 0.0000 0.0000 100.0 Pass 6 0.0000 0.0000 100.0 Pass 7 0.0000 0.0000 100.0 Pass 8 0.0000 0.0000 100.0 Pass 9 0.0000 0.0000 100.0 Pass 10 0.0000 0.0000 100.0 Pass 11 0.0000 0.0000 100.0 Pass 12 0.0000 0.0000 100.0 Pass 13 0.0000 0.0000 100.0 Pass 14 0.0000 0.0000 100.0 Pass 15 0.0000 0.0000 100.0 Pass 16 0.0001 0.0001 100.0 Pass 17 0.0001 0.0001 100.0 Pass 18 0.0001 0.0001 100.0 Pass 19 0.0001 0.0001 100.0 Pass 20 0.0001 0.0001 100.0 Pass 21 0.0001 0.0001 100.0 Pass 22 0.0001 0.0001 100.0 Pass 23 0.0001 0.0001 100.0 Pass 24 0.0001 0.0001 100.0 Pass 25 0.0001 0.0001 100.0 Pass 26 0.0000 0.0000 100.0 Pass 27 0.0001 0.0001 100.0 Pass 28 0.0001 0.0001 100.0 Pass 29 0.0001 0.0001 100.0 Pass 30 0.0001 0.0001 100.0 Pass Oct1 0.0001 0.0001 100.0 Pass 2 0.0001 0.0001 100.0 Pass 3 0.0001 0.0001 100.0 Pass 4 0.0001 0.0001 100.0 Pass 5 0.0002 0.0002 100.0 Pass 6 0.0002 0.0002 100.0 Pass 7 0.0002 0.0002 100.0 Pass 8 0.0002 0.0002 100.0 Pass 9 0.0002 0.0002 100.0 Pass 10 0.0002 0.0002 100.0 Pass 11 0.0001 0.0001 100.0 Pass 12 0.0001 0.0001 100.0 Pass 13 0.0001 0.0001 100.0 Pass 14 0.0001 0.0001 100.0 Pass 15 0.0001 0.0001 100.0 Pass 16 0.0001 0.0001 100.0 Pass 17 0.0002 0.0002 100.0 Pass 18 0.0002 0.0002 100.0 Pass 19 0.0004 0.0004 100.0 Pass 20 0.0004 0.0004 100.0 Pass 21 0.0003 0.0003 100.0 Pass 22 0.0003 0.0003 100.0 Pass 23 0.0002 0.0002 100.0 Pass 24 0.0002 0.0002 100.0 Pass 25 0.0003 0.0003 100.0 Pass 26 0.0003 0.0003 100.0 Pass 27 0.0003 0.0003 100.0 Pass 28 0.0003 0.0003 100.0 Pass 29 0.0003 0.0003 100.0 Pass 30 0.0003 0.0003 100.0 Pass Wetland Hydration 6/19/2024 11:58:33 AM Page 20 31 0.0003 0.0003 100.0 Pass Nov1 0.0003 0.0003 100.0 Pass 2 0.0005 0.0005 100.0 Pass 3 0.0006 0.0006 100.0 Pass 4 0.0005 0.0005 100.0 Pass 5 0.0006 0.0006 100.0 Pass 6 0.0006 0.0006 100.0 Pass 7 0.0005 0.0005 100.0 Pass 8 0.0005 0.0005 100.0 Pass 9 0.0006 0.0006 100.0 Pass 10 0.0007 0.0007 100.0 Pass 11 0.0008 0.0008 100.0 Pass 12 0.0007 0.0007 100.0 Pass 13 0.0008 0.0008 100.0 Pass 14 0.0006 0.0006 100.0 Pass 15 0.0006 0.0006 100.0 Pass 16 0.0006 0.0006 100.0 Pass 17 0.0006 0.0006 100.0 Pass 18 0.0007 0.0007 100.0 Pass 19 0.0009 0.0009 100.0 Pass 20 0.0008 0.0008 100.0 Pass 21 0.0007 0.0007 100.0 Pass 22 0.0007 0.0007 100.0 Pass 23 0.0010 0.0010 100.0 Pass 24 0.0010 0.0010 100.0 Pass 25 0.0009 0.0009 100.0 Pass 26 0.0008 0.0008 100.0 Pass 27 0.0006 0.0006 100.0 Pass 28 0.0006 0.0006 100.0 Pass 29 0.0007 0.0007 100.0 Pass 30 0.0007 0.0007 100.0 Pass Dec1 0.0008 0.0008 100.0 Pass 2 0.0010 0.0010 100.0 Pass 3 0.0008 0.0008 100.0 Pass 4 0.0007 0.0007 100.0 Pass 5 0.0007 0.0007 100.0 Pass 6 0.0006 0.0006 100.0 Pass 7 0.0006 0.0006 100.0 Pass 8 0.0006 0.0006 100.0 Pass 9 0.0007 0.0007 100.0 Pass 10 0.0007 0.0007 100.0 Pass 11 0.0008 0.0008 100.0 Pass 12 0.0008 0.0008 100.0 Pass 13 0.0008 0.0008 100.0 Pass 14 0.0009 0.0009 100.0 Pass 15 0.0008 0.0008 100.0 Pass 16 0.0007 0.0007 100.0 Pass 17 0.0006 0.0006 100.0 Pass 18 0.0006 0.0006 100.0 Pass 19 0.0007 0.0007 100.0 Pass 20 0.0007 0.0007 100.0 Pass 21 0.0007 0.0007 100.0 Pass 22 0.0007 0.0007 100.0 Pass 23 0.0006 0.0006 100.0 Pass 24 0.0006 0.0006 100.0 Pass 25 0.0007 0.0007 100.0 Pass 26 0.0009 0.0009 100.0 Pass 27 0.0007 0.0007 100.0 Pass Wetland Hydration 6/19/2024 11:58:33 AM Page 21 28 0.0006 0.0006 100.0 Pass 29 0.0008 0.0008 100.0 Pass 30 0.0007 0.0007 100.0 Pass 31 0.0006 0.0006 100.0 Pass Wetland Hydration 6/19/2024 11:58:33 AM Page 22 LID Report Wetland Hydration 6/19/2024 11:59:01 AM Page 23 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. Wetland Hydration 6/19/2024 11:59:01 AM Page 24 Appendix Predeveloped Schematic Wetland Hydration 6/19/2024 11:59:03 AM Page 25 Mitigated Schematic Appendix E Operation & Maintenance Manual APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-6 NO. 3 – DETENTION TANKS AND VAULTS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Tank or Vault Storage Area Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non- floatables). No trash or debris in vault. Sediment accumulation Accumulated sediment depth exceeds 10% of the diameter of the storage area for ½ length of storage vault or any point depth exceeds 15% of diameter. Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than ½ length of tank. All sediment removed from storage area. Tank Structure Plugged air vent Any blockage of the vent. Tank or vault freely vents. Tank bent out of shape Any part of tank/pipe is bent out of shape more than 10% of its design shape. Tank repaired or replaced to design. Gaps between sections, damaged joints or cracks or tears in wall A gap wider than ½-inch at the joint of any tank sections or any evidence of soil particles entering the tank at a joint or through a wall. No water or soil entering tank through joints or walls. Vault Structure Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. Inlet/Outlet Pipes Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged inlet/outlet pipes Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance. Manhole access covered. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-7 NO. 3 – DETENTION TANKS AND VAULTS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Access Manhole (cont.) Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. Large access doors/plate Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can be opened as designed. Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; covers access opening completely. Lifting rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-8 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Structure Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the structure opening or is blocking capacity of the structure by more than 10%. No Trash or debris blocking or potentially blocking entrance to structure. Trash or debris in the structure that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the structure. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Sediment accumulation Sediment exceeds 60% of the depth from the bottom of the structure to the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section or is within 6 inches of the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section. Sump of structure contains no sediment. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering structure through cracks, or maintenance person judges that structure is unsound. Structure is sealed and structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering structure through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Structure has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Ladder rungs missing or unsafe Ladder is unsafe due to missing rungs, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows maintenance person safe access. FROP-T Section Damaged FROP-T T section is not securely attached to structure wall and outlet pipe structure should support at least 1,000 lbs of up or down pressure. T section securely attached to wall and outlet pipe. Structure is not in upright position (allow up to 10% from plumb). Structure in correct position. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-9 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED FROP-T Section (cont.) Damaged FROP-T (cont.) Connections to outlet pipe are not watertight or show signs of deteriorated grout. Connections to outlet pipe are water tight; structure repaired or replaced and works as designed. Any holes—other than designed holes—in the structure. Structure has no holes other than designed holes. Cleanout Gate Damaged or missing cleanout gate Cleanout gate is missing. Replace cleanout gate. Cleanout gate is not watertight. Gate is watertight and works as designed. Gate cannot be moved up and down by one maintenance person. Gate moves up and down easily and is watertight. Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed. Orifice Plate Damaged or missing orifice plate Control device is not working properly due to missing, out of place, or bent orifice plate. Plate is in place and works as designed. Obstructions to orifice plate Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Overflow Pipe Obstructions to overflow pipe Any trash or debris blocking (or having the potential of blocking) the overflow pipe. Pipe is free of all obstructions and works as designed. Deformed or damaged lip of overflow pipe Lip of overflow pipe is bent or deformed. Overflow pipe does not allow overflow at an elevation lower than design Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged inlet/outlet pipe Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Metal Grates (If applicable) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. Damaged or missing grate Grate missing or broken member(s) of the grate. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-10 NO. 5 – CATCH BASINS AND MANHOLES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Structure Sediment accumulation Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert of the lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin. Sump of catch basin contains no sediment. Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin by more than 10%. No Trash or debris blocking or potentially blocking entrance to catch basin. Trash or debris in the catch basin that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the catch basin. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane). No dead animals or vegetation present within catch basin. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering catch basin through cracks, or maintenance person judges that catch basin is unsound. Catch basin is sealed and is structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-11 NO. 5 – CATCH BASINS AND MANHOLES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Inlet/Outlet Pipe (cont.) Damaged inlet/outlet pipe Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Metal Grates (Catch Basins) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. Damaged or missing grate Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-12 NO. 6 – CONVEYANCE PIPES AND DITCHES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Pipes Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes. Vegetation/root growth in pipe Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Damage to protective coating or corrosion Protective coating is damaged; rust or corrosion is weakening the structural integrity of any part of pipe. Pipe repaired or replaced. Damaged pipes Any dent that decreases the cross section area of pipe by more than 20% or is determined to have weakened structural integrity of the pipe. Pipe repaired or replaced. Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Trash and debris cleared from ditches. Sediment accumulation Accumulated sediment that exceeds 20% of the design depth. Ditch cleaned/flushed of all sediment and debris so that it matches design. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Excessive vegetation growth Vegetation that reduces free movement of water through ditches. Water flows freely through ditches. Erosion damage to slopes Any erosion observed on a ditch slope. Slopes are not eroding. Rock lining out of place or missing (If applicable) One layer or less of rock exists above native soil area 5 square feet or more, any exposed native soil. Replace rocks to design standards. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-15 NO. 9 – FENCING MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Erosion or holes under fence Erosion or holes more than 4 inches high and 12-18 inches wide permitting access through an opening under a fence. No access under the fence. Wood Posts, Boards and Cross Members Missing or damaged parts Missing or broken boards, post out of plumb by more than 6 inches or cross members broken No gaps on fence due to missing or broken boards, post plumb to within 1½ inches, cross members sound. Weakened by rotting or insects Any part showing structural deterioration due to rotting or insect damage All parts of fence are structurally sound. Damaged or failed post foundation Concrete or metal attachments deteriorated or unable to support posts. Post foundation capable of supporting posts even in strong wind. Metal Posts, Rails and Fabric Damaged parts Post out of plumb more than 6 inches. Post plumb to within 1½ inches. Top rails bent more than 6 inches. Top rail free of bends greater than 1 inch. Any part of fence (including post, top rails, and fabric) more than 1 foot out of design alignment. Fence is aligned and meets design standards. Missing or loose tension wire. Tension wire in place and holding fabric. Deteriorated paint or protective coating Part or parts that have a rusting or scaling condition that has affected structural adequacy. Structurally adequate posts or parts with a uniform protective coating. Openings in fabric Openings in fabric are such that an 8-inch diameter ball could fit through. Fabric mesh openings within 50% of grid size. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-17 NO. 11 – GROUNDS (LANDSCAPING) MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Trees and Shrubs Hazard tree identified Any tree or limb of a tree identified as having a potential to fall and cause property damage or threaten human life. A hazard tree identified by a qualified arborist must be removed as soon as possible. No hazard trees in facility. Damaged tree or shrub identified Limbs or parts of trees or shrubs that are split or broken which affect more than 25% of the total foliage of the tree or shrub. Trees and shrubs with less than 5% of total foliage with split or broken limbs. Trees or shrubs that have been blown down or knocked over. No blown down vegetation or knocked over vegetation. Trees or shrubs free of injury. Trees or shrubs which are not adequately supported or are leaning over, causing exposure of the roots. Tree or shrub in place and adequately supported; dead or diseased trees removed. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-38 NO. 25 – DRYWELL BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Preventive Plugging, obstructions Any cause limiting flow into drywell. Drywell able to receive full flow prior to and during wet season. Site Trash and debris Trash or debris that could end up in the drywell is evident. No trash or debris that could get into the drywell can be found. Pipes Plugged inlet The entrance to the pipe is restricted due to sediment, trash, or debris. The entrance to the pipe is not restricted. Vegetation/root growth in pipes Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes. Plugged pipe Sediment or other material prevents free flow of water through the pipe. Water flows freely through pipes. Broken pipe or joint leaks Damage to the pipe or pipe joints allowing water to seep out. Pipe does not allow water to exit other than at the outlet. Structure Basin leaks Holes or breaks in the basin allow water to leave the basin at locations other than per design. Basin is sealed and allows water to exit only where designed. Filter Media Plugged filter media Filter media plugged. Flow through filter media is normal. NO. 26 – GRAVEL FILLED INFILTRATION TRENCH BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Preventive Blocking, obstructions Debris or trash limiting flow to infiltration trench. Infiltration trench able to receive full flow prior to and during wet season. Site Trash and debris Trash or debris that could end up in the infiltration trench is evident. No trash or debris that could get into the infiltration trench can be found. Pipes Plugged inlet The entrance to the pipe is restricted due to sediment, trash, or debris. The entrance to the pipe is not restricted. Vegetation/root growth in pipes Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes. Plugged pipes Sediment or other material prevents free flow of water through the pipe. Water flows freely through pipes. Broken pipe or joint leaks Damage to the pipe or pipe joints allowing water to seep out. Pipe does not allow water to exit other than at the outlet to the trench. Structure Flow not reaching trench Flows are not getting into the trench as designed. Water enters and exits trench as designed. Cleanout/inspection access does not allow cleaning or inspection of trench The cleanout/inspection access is not available. Cleanout/inspection access is available. Filter Media Plugged filter media Filter media plugged. Flow through filter media is normal. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-47 NO. 38 – SOIL AMENDMENT BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Soil Media Unhealthy vegetation Vegetation not fully covering ground surface or vegetation health is poor. Yellowing: possible Nitrogen (N) deficiency. Poor growth: possible Phosphorous (P) deficiency. Poor flowering, spotting or curled leaves, or weak roots or stems: possible Potassium (K) deficiency. Plants are healthy and appropriate for site conditions Inadequate soil nutrients and structure In the fall, return leaf fall and shredded woody materials from the landscape to the site when possible Soil providing plant nutrients and structure Excessive vegetation growth Grass becomes excessively tall (greater than 10 inches); nuisance weeds and other vegetation start to take over. Healthy turf- “grasscycle” (mulch-mow or leave the clippings) to build turf health Weeds Preventive maintenance Avoid use of pesticides (bug and weed killers), like “weed & feed,” which damage the soil Fertilizer needed Where fertilization is needed (mainly turf and annual flower beds), a moderate fertilization program should be used which relies on compost, natural fertilizers or slow-release synthetic balanced fertilizers Integrated Pest Management (IPM) protocols for fertilization followed Bare spots Bare spots on soil No bare spots, area covered with vegetation or mulch mixed into the underlying soil. Compaction Poor infiltration due to soil compaction  To remediate compaction, aerate soil, till to at least 8-inch depth, or further amend soil with compost and re-till  If areas are turf, aerate compacted areas and top dress them with 1/4 to 1/2 inch of compost to renovate them  If drainage is still slow, consider investigating alternative causes (e.g., high wet season groundwater levels, low permeability soils)  Also consider site use and protection from compacting activities No soil compaction Poor infiltration Soils become waterlogged, do not appear to be infiltrating. Facility infiltrating properly Erosion/Scouring Erosion Areas of potential erosion are visible Causes of erosion (e.g., concentrate flow entering area, channelization of runoff) identified and damaged area stabilized (regrade, rock, vegetation, erosion control matting).For deep channels or cuts (over 3 inches in ponding depth), temporary erosion control measures in place until permanent repairs can be made Grass/Vegetation Unhealthy vegetation Less than 75% of planted vegetation is healthy with a generally good appearance. Healthy vegetation. Unhealthy plants removed/replaced. Appropriate vegetation planted in terms of exposure, soil and soil moisture. Noxious Weeds Noxious weeds Listed noxious vegetation is present (refer to current County noxious weed list). No noxious weeds present. Underground stormwater detention and infiltration systems must be inspected and maintained at regular intervals for purposes of performance and longevity. Inspection Inspection is the key to effective maintenance of CMP detention systems and is easily performed. Contech recommends ongoing, quarterly inspections. The rate at which the system collects pollutants will depend more on site specific activities rather than the size or configuration of the system. Inspections should be performed more often in equipment washdown areas, in climates where sanding and/or salting operations take place, and in other various instances in which one would expect higher accumulations of sediment or abrasive/corrosive conditions. A record of each inspection is to be maintained for the life of the system. Maintenance CMP detention systems should be cleaned when an inspection reveals accumulated sediment or trash is clogging the discharge orifice. Accumulated sediment and trash can typically be evacuated through the manhole over the outlet orifice. If maintenance is not performed as recommended, sediment and trash may accumulate in front of the outlet orifice. Manhole covers should be securely seated following cleaning activities. Contech suggests that all systems be designed with an access/inspection manhole situated at or near the inlet and the outlet orifice. Should it be necessary to get inside the system to perform maintenance activities, all appropriate precautions regarding confined space entry and OSHA regulations should be followed. Systems are to be rinsed, including above the spring line, annually soon after the spring thaw, and after any additional use of salting agents, as part of the maintenance program for all systems where salting agents may accumulate inside the pipe. Maintaining an underground detention or infiltration system is easiest when there is no flow entering the system. For this reason, it is a good idea to schedule the cleanout during dry weather. The foregoing inspection and maintenance efforts help ensure underground pipe systems used for stormwater storage continue to function as intended by identifying recommended regular inspection and maintenance practices. Inspection and maintenance related to the structural integrity of the pipe or the soundness of pipe joint connections is beyond the scope of this guide. Contech® CMP Detention Inspection and Maintenance Guide CMP MAINTENANCE GUIDE 2/17 PDF © 2017 Contech Engineered Solutions LLC All rights reserved. Printed in USA. ENGINEERED SOLUTIONS NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION CMP DETENTION SYSTEMS Underground stormwater detention and infiltration systems must be inspected and maintained at regular intervals for purposes of performance and longevity. Inspection Inspection is the key to effective maintenance of CMP detention systems and is easily performed. Contech recommends ongoing, annual inspections. Sites with high trash load or small outlet control orifices may need more frequent inspections. The rate at which the system collects pollutants will depend more on- site specific activities rather than the size or configuration of the system. Inspections should be performed more often in equipment washdown areas, in climates where sanding and/or salting operations take place, and in other various instances in which one would expect higher accumulations of sediment or abrasive/ corrosive conditions. A record of each inspection is to be maintained for the life of the system. NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. CMP MAINTENANCE GUIDE 10/19 PDF © 2019 CONTECH ENGINEERED SOLUTIONS LLC, A QUIKRETE COMPANY ALL RIGHTS RESERVED. PRINTED IN USA. Maintenance CMP detention systems should be cleaned when an inspection reveals accumulated sediment or trash is clogging the discharge orifice. Accumulated sediment and trash can typically be evacuated through the manhole over the outlet orifice. If maintenance is not performed as recommended, sediment and trash may accumulate in front of the outlet orifice. Manhole covers should be securely seated following cleaning activities. Contech suggests that all systems be designed with an access/inspection manhole situated at or near the inlet and the outlet orifice. Should it be necessary to get inside the system to perform maintenance activities, all appropriate precautions regarding confined space entry and OSHA regulations should be followed. Annual inspections are best practice for all underground systems. During this inspection if evidence of salting/de-icing agents is observed within the system, it is best practice for the system to be rinsed, including above the spring line soon after the spring thaw as part of the maintenance program for the system. Maintaining an underground detention or infiltration system is easiest when there is no flow entering the system. For this reason, it is a good idea to schedule the cleanout during dry weather. The foregoing inspection and maintenance efforts help ensure underground pipe systems used for stormwater storage continue to function as intended by identifying recommended regular inspection and maintenance practices. Inspection and maintenance related to the structural integrity of the pipe or the soundness of pipe joint connections is beyond the scope of this guide. Contech® CMP Detention Inspection and Maintenance Guide ENGINEERED SOLUTIONS CMP DETENTION SYSTEMS