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City of Everett Edgewater Creek Bridge Replacement <br /> WORK ELEMENT 11 CIVIL, ROADWAY & DRAINAGE DESIGN: <br /> This work element is performed by Perteet to provide design the TS&L phase and civil, roadway <br /> and drainage design of the bridge's alternative of choice approaches at 30%,60%, 90%and 100% <br /> levels. <br /> 11.1 —Stormwater <br /> The stormwater task consists of the following work elements: <br /> 11.1.1 Design Criteria <br /> The 2012 Stormwater Management Manual for Western Washington, as amended in 2014 <br /> (SWMMWW),the City of Everett 2020 Design and Construction Standards, and City of Everett <br /> 2016 Ordinance to Update EMC 14.28, Stormwater and Drainage (EMC Ord.)will be used as <br /> the stormwater regulatory manuals for this project. The 2012 LID Manual may also be used as <br /> guidance. Prior to beginning project stormwater design, a stormwater design criteria matrix will <br /> be prepared summarizing all stormwater related requirements and standards. The design criteria <br /> matrix will be provided to the City of Everett for review and concurrence prior to beginning <br /> design work. <br /> Deliverables: <br /> • Stormwater Design Criteria Matrix(to be included with the drainage report) <br /> 11.1.2 Off-Site Analysis <br /> Consultant will conduct a downstream analysis extending 1/4 mile downstream/down-gradient of <br /> the project right-of-way limits for the single Threshold Discharge Area(TDA)associated with <br /> the project site. The downstream analysis will include a review of City GIS maps, recent <br /> drainage complaint documentation provided by the City(if it exists), and an assessment of <br /> downstream routes to identify evidence of erosion, flooding, sedimentation, or flow constriction <br /> points. A visual above-ground inspection will not be conducted given the very steep slopes and <br /> highly dense forest present along the downstream route. The assessment of the downstream <br /> effects is to be a qualitative evaluation based upon engineering judgment and any information on <br /> the downstream system that the City can provide. Consultant will prepare a written description of <br /> the downstream system conditions and provide a map showing the downstream drainage route. <br /> Consultant will perform a visual inspection of the upstream contributing basin area of the site <br /> and provide an estimate of the area draining to the site based on available mapping data and site <br /> visit observation. <br /> This task does not include a detailed review of upstream basin boundary or land use assessment <br /> and any detailed hydraulic analysis or computations associated with the upstream or downstream <br /> basins. <br /> Assumptions: <br /> • The site lies within one(1)distinct TDA. Therefore, only one(1)downstream analysis is <br /> assumed. <br /> Page 31 of 42 <br />