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le-WWATERSHED SCIENCE & ENGINEERING April 30, 2024 Scope of Work Ellensburg Urban Flooding Hydraulic Analysis Kittitas County, WA Background The City of Ellensburg (City) is conducting an in-depth analysis within the Ellensburg Urban Growth Area (UGA) and city limits to support an updated stormwater model for the current floodplain map update process led by Kittitas County, focused on urban flooding caused by Whiskey and Mercer Creeks. The modeling will also support future flood map updates proposed for Wilson Creek, increase understanding of flooding in the city, and identify mitigation actions. With this knowledge, the City will be more prepared for flood events, and residents within the City and its UGA--especially those in areas with a high probability of flooding during a 1%annual chance flood --will be better equipped to take additional precautions or mitigate against the risk of flooding. The consultant team is led by Perteet with support from Evergreen H2O and Watershed Science & Engineering (WSE). The following tasks will be completed by WSE under a contract with Kittitas County Public Works (County) and are structured to be consistent with tasks contracted between the City and Perteet. Task 2. Data Collection and Modeling The goal of Task 2 is to gather all information required to increase the City's and County's understanding of flooding within the UGA, prepare the stormwater model, and increase the accuracy of the hydraulic model and/or increase the City's level of certainty in the hydraulic model, which can be used to support a Letter of Map Revision (LOMR). Task 2.1. Core Planning Team and Project Management This task is dedicated to the overall management of the project. WSE's work elements include: • Attending up to 20 Core Planning Team (CPT) meetings • Preparing monthly progress reports for the County Assumptions: • CPT meetings with be virtual • WSE's staff engineer will attend all 20 meetings. WSE's senior engineer will attend up to 10 of the meetings as needed. • The project duration will be 14 months Deliverables: • Monthly progress reports Task 2.2. Data Collection This task will provide the data necessary to evaluate the stormwater system and flooding in the Ellensburg UGA to support the development of current baseline conditions updates to the flood model, development of the stormwater model, and define the projected climate change scenario for precipitation and flooding that will be used in this project. The consultant team will review existing data and determine what additional data must be collected to inform the project and document current baseline conditions. Data to be collected may include