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Page 42 of 59 <br /> <br />City of Everett Merrill & Ring Bridge Replacement <br />WORK ELEMENT 12 CIVIL, ROADWAY, WATER & DRAINAGE DESIGN <br /> <br />This work element is performed by Perteet to provide design for the TS&L phase and civil, <br />roadway, water, and drainage design of the bridge’s alternative of choice approaches at 30%, <br />60%, 90%, 100%and Ad-Ready PS&E levels. <br />12.1 – Stormwater Design <br /> <br />The stormwater task consists of the following work elements: <br /> <br />12.1.1 Design Criteria <br />The 2019 Stormwater Management Manual for Western Washington, (SWMMWW), the City of <br />Everett 2023 Design and Construction Standards and Specifications (DCSS), and Everett <br />Municipal Code Chapter 14.28, will be used as the stormwater regulatory guidance for this <br />project. When the 2024 SWMMWW and DCSS are released, the project will update to the latest <br />guidance. The 2012 LID Manual may also be used as guidance. Prior to beginning project <br />stormwater design, a stormwater design criteria matrix will be prepared summarizing all <br />stormwater related requirements and standards. The design criteria matrix will be provided to the <br />City of Everett for review and concurrence prior to beginning design work. <br /> <br />Deliverables: <br />x Stormwater Design Criteria Matrix (to be included with the TS&L deliverables and <br />drainage report) <br /> <br />12.1.2 Off-Site Analysis <br />Perteet will conduct a downstream analysis extending ¼ mile downstream/down-gradient of the <br />project right-of-way limits for the single Threshold Discharge Area (TDA) associated with the <br />project site. The downstream analysis will include a review of City GIS maps, recent drainage <br />complaint documentation provided by the City (if it exists), and an assessment of downstream <br />routes to identify evidence of erosion, flooding, sedimentation, or flow constriction points. A <br />limited visual above-ground inspection will be conducted given the very steep slopes and dense <br />forest present along the downstream route. The assessment of the downstream effects is to be a <br />qualitative evaluation based upon engineering judgment and any information on the downstream <br />system that the City can provide. Perteet will prepare a written description of the downstream <br />system conditions and provide a map showing the downstream drainage route. <br /> <br />Perteet will perform a visual inspection of the upstream contributing basin area of the site and <br />provide an estimate of the area draining to the site based on available mapping data and site visit <br />observation. <br /> <br />This task does not include a detailed review of upstream basin boundary or land use assessment <br />or any detailed hydraulic analysis or computations associated with the upstream or downstream <br />basins. <br /> <br />Assumptions: