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PGSF WMVD Storm and Combined Sewer Design Scope of Work 08-25-2023 <br /> <br />32 of 41 <br /> <br />Category 2: Sensitive information <br />Category 2: For official use only / disclosure permissible by law. <br />• Considerations for items that could be implemented during Design of the project to lower the <br />trenchless crossing risk. <br />Phase 515 – Rehabilitation Method and TM for Existing BNSF Crossing <br />Objective: Investigate trenchless rehabilitation methods for the casing (30-inch pipe that will host the <br />LS46 discharge sanitary sewer force main (CO3)) that is currently installed beneath the BNSF <br />railroad tracks. STC will evaluate the condition of the existing crossing and provide a number of <br />methods that could be used to rehabilitate the crossing based on information and design <br />parameters provided by B&C. <br />Activities/Approach: Feasible rehabilitation alternatives will be developed with B&C. STC will work <br />collaboratively with B&C to identify rehabilitation methods(s) to be further developed for <br />consideration. Selection of the preferred rehabilitation method most suited to the project will be <br />based on defined project constraints, prepared by others. A number of rehabilitation methods will be <br />evaluated based on project design criteria. A technical meeting will be held to go over the <br />rehabilitation findings and to collaboratively select the rehabilitation method that is best suited to <br />the project. <br />Task Assumptions <br />• Information on the condition of the existing casing will be provided to STC by others. <br />• B&C will provide regular updates to STC regarding the status of the conveyance pipeline (s) <br />at the location of the existing casing to ensure that any changes to the conveyance pipeline <br />(s) do not impact the design of the rehabilitation. <br />Everett Responsibilities <br />• Review and provide comments on TM <br />Meetings <br />• Coordination meetings as needed <br />Work Products: <br />A trenchless rehabilitation memo will be prepared that presents the rehabilitation methods that were <br />considered, the recommended rehabilitation method(s), and the reasoning behind the method <br />selection. This memo is envisioned to be stand-alone; however, it will be in support of engineering <br />performed by B&C. The TM will outline project footprints and any excavations that may be needed to <br />perform the rehabilitation. Comparative costs will be presented in consideration of the method <br />selection. The TM will be subject to internal QA/QC prior to delivering the Draft memo to B&C. STC <br />will resolve any B&C review comments prior to submitting the final TM. A comment and resolution log <br />will be maintained to document incorporation of changes to the TM. <br />Phase 520 – Preliminary, 60%, and Final Design of Trenchless Construction <br />Objective: STC will design the installation of the new crossing beneath BNSF as well as the <br />rehabilitation of the existing BNSF crossing. The design will include all calculations and analyses <br />necessary to develop bid-ready plans and specifications. The trenchless method that will be <br />designed will be based on the findings in the Final Trenchless Feasibility TM and the Trenchless <br />Rehabilitation TM. For the new casing installation, STC will determine appropriate casing diameter <br />and design wall thickness, make engineering recommendations on the installation elevation of the <br />pipeline based on AREMA standards and ease of permitting, identify work areas and the need for