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Seattle, WA 98168 Tel: 206.241.6000 NHC Reference No. 2008118 January 2, 2026 City of Renton 1055 S Grady Way Renton, WA 98057 Attention:Chester Bennett, Public Works Surface Water Engineer Re: Cedar River Post-flood Survey and Reconnaissance Scope and Budget Dear Chester: Following are a scope of work, cost estimate, and approximate schedule for NHC to conduct several post-flood reconnaissance and survey tasks on the lower Cedar River. Our understanding is that this will be performed under an amendment to the Annual Sediment Survey (City of Renton CAG-23-124, NHC ref no. 2008118). These are provided following our discussion regarding the City of Renton’s intent to identify channel changes that occurred in the December 2025 flooding sooner than the annual Cedar River survey typically conducted in the fall. This will facilitate potential flood mitigation efforts, including dredge planning. PROJECT TASKS The project is divided into three separate but related tasks: Bathymetric Survey, Sediment Source Cataloging, and a Transport Distance Analysis. Each of these tasks can be carried out independently, as directed by the City. All three characterize changes to the Cedar River from the most recent events and will be useful for understanding additional risk factors that may exist in the next high flow event; specifically, if current bed levels in the Cedar River exceed identified risk thresholds.7RWDOIHHIRUDOOWKUHHWDVNVLVHVWLPDWHGQRWWRH[FHHG Task 1: Bathymetric Survey After notice to proceed and identification of suitable flow conditions, NHC will re-survey selected annual repeat cross sections (25-50% of the full set) as well as some additional bathymetric data collection. This information will be compared with the annual survey results in order to assess the extent and magnitude of post-flood channel change. Collection may be performed by boat, wading, from bridges, or other methods based on flow conditions. This task includes up to two (2) days of time for a 2-person field crew to complete the survey as well as Exhibit A Rev 1 January 2026 Cedar River Post-flood Survey and Reconnaissance 2 Scope and Budget necessary post-processing, analysis, and preparation of a brief report. The budgeted cost for this task is $12,713 and additional details can be found in the attached fee estimate. Task 2: Sediment Source Cataloging This task includes a more qualitative evaluation of the lower Cedar River, from approximately Ron Regis park through the City reach to identify and catalog existing and ongoing sources of sediment. River-based observations of bank conditions, landslide failure size estimation, and bar material compositions will be used to map and catalog known and likely sources of material that may make its way into the City reach soon. This will include 1 day for a 2-person field crew to complete the float and additional time for cataloging acquired data. Specific observations to be collected include (as applicable): rough dimensions of slide areas, pebble counts/grain size characterization, as well as mapped qualitative bank stability. Deliverables include a reach map, catalog photographs, and a brief report. The budgeted cost for this task is $10,862 and additional details can be found in the attached fee estimate. Task 3: Transport Distance Analysis This task will assess the distance that sediment of various sizes from cobbles to silts could be expected to travel based on the observed flow hydrograph in the December 2025 event. This will be conducted using USGS gage records, existing hydraulic modeling, and standard sediment transport analyses. Specifically, the analysis is intended help understand if recent restoration work or known sediment sources on the upper Cedar River could contribute to deposition within the City. In addition to informing the City how much of the added sediment supply would deposit in the lower reach. This task includes literature review, geomorphic and hydraulic analyses, and preparation of a brief report. The budgeted cost for this task is $11,786 and additional details can be found in the attached fee estimate. SCHEDULE NHC will begin each task upon contract amendment and specific written notice to proceed. We anticipate survey for Tast 1 occurring in early February 2026 with post-processing and analysis complete by the end of February. Work for Tasks 2 and 3 will largely be completed in February with some portions likely extending into March 2026. NHC and the City will coordinate throughout the project, please contact me if you need any further information. Sincerely, Northwest Hydraulic Consultants Inc. Peter Brooks, P.E. Principal Task 1 Northwest Hydraulic Consultants Inc. Prepared for: City of Renton 12787 Gateway Drive S. Project: 2026 Post-flood Survey Seattle, WA 98168 Date: Tel. (206) 241-6000 Prepared By: E. McMeen/P. Brooks Fax (206) 439-2420 Principal Eng./ Sci. 1 Eng./ Sci. 2 Eng. Tech 1 GIS Analyst 1 Total Hours NHC Labor Task Total Field Survey 22424507,416$ 7,416$ Analysis and Documentation 4 12 4 20 3,497$ 3,497$ Total Hours and Direct Labor Cost (DL)6.0 0.0 36.0 28.0 0.0 $10,913 Total Labor Rate ($/hr) 292.42$ 170.50$ 148.62$ $136.00 $153.23 2025 Renton rates Direct Expense Detail Task Units Rate Cost Boat 2 400$ $800 Bathymetric survey package 2 500$ $1,000 DIRECT EXPENSE TOTAL $1,800 Total Fee $12,713 NHC Staff Hours Totals TASK DESCRIPTION 1/20/2026 Task 2 Northwest Hydraulic Consultants Inc. Prepared for: City of Renton 12787 Gateway Drive S. Project: 2026 Post-flood Survey Seattle, WA 98168 Date: Tel. (206) 241-6000 Prepared By: E. McMeen/P. Brooks Fax (206) 439-2420 Principal Eng./ Sci. 1 Eng./ Sci. 2 Eng. Tech 1 GIS Analyst 1 Total Hours NHC Labor Task Total Reach Float 21414 305,053$ 5,053$ Follow up Analysis & Reporting 4168 4325,700$ 5,700$ Total Hours and Direct Labor Cost (DL)6.0 30.0 22.0 0.0 4.0 $10,752 Total Labor Rate ($/hr) 292.42$ 170.50$ 148.62$ $136.00 $153.23 2025 Renton rates Direct Expense Detail Task Units Rate Cost 2p pontoon 1 110$ $110 DIRECT EXPENSE TOTAL $110 Total Fee $10,862 NHC Staff Hours Totals TASK DESCRIPTION 1/20/2026 Task 3 Northwest Hydraulic Consultants Inc. Prepared for: City of Renton 12787 Gateway Drive S. Project: 2026 Post-flood Survey Seattle, WA 98168 Date: Tel. (206) 241-6000 Prepared By: E. McMeen/P. Brooks Fax (206) 439-2420 Principal Eng./ Sci. 1 Eng./ Sci. 2 Eng. Tech 1 GIS Analyst 1 Total Hours NHC Labor Task Total Literature and Data Review 162 91,613$ 1,613$ Analysis 42412 407,045$ 7,045$ Reporting 4 8 4 16 3,128$ 3,128$ Total Hours and Direct Labor Cost (DL)9.0 38.0 18.0 0.0 0.0 $11,786 Total Labor Rate ($/hr) 292.42$ 170.50$ 148.62$ $136.00 $153.23 2025 Renton rates Direct Expense Detail Task Units Rate Cost None anticipated DIRECT EXPENSE TOTAL $0 Total Fee $11,786 NHC Staff Hours Totals TASK DESCRIPTION 1/20/2026