Brown and Caldwell, Inc. 9/20/2023

PGSF WMVD Storm and Combined Sewer Design Scope of Work 08-25-2023 30 of 41 Category 2: Sensitive information Category 2: For official use only / disclosure permissible by law. Task Assumptions • None Everett Responsibilities • Provide comments on BODR. Meetings • None Work Products: • Draft and Final BODR. BNSF Trenchless Crossing The trenchless work and BNSF crossing work for both CO-3 and CO-8 is being led by Staheli Trenchless Consultants (STC). Phase 510 – Trenchless Installation Method TM and Workshop – New BNSF Railroad Crossing Objective: The objective of the trenchless feasibility study is to select a trenchless method for the installation of a new casing that will cross beneath the BNSF Railroad Track. The selection of the trenchless method will be based on the cost-risk weighted profile for the trenchless method that will be developed in a technical memorandum as well as the conclusions of a trenchless methods workshop that will be held with the City of Everett. Activities/Approach: STC will perform a trenchless feasibility study to select the trenchless ins tallation method for the installation of a casing beneath the BNSF Railroad. The analysis will include the following: • Review of existing geotechnical information and local groundwater elevation. • Determining trenchless methods that are feasible for casing installation, based on pipe size, length, depth, geotechnical conditions, and groundwater regime. The scope assumes that 2 to 3 trenchless methods will be deemed feasible for comparison. • Work in conjunction with B&C to develop a feasible location for the BNSF crossing, based on the required temporary construction area that is needed to install the pipe and meet BNSF permitting standards. • Perform a risk evaluation for the crossing, identifying specific risks that could occur with each method, the measures that would be required if the risk were to occur during construction, and the cost of risk mitigation. Risks for each of the trenchless methods will be given a weighted score according to a probability of occurrence and the cost of mitigation measures to overcome the risk. • Develop comparison-level cost estimates and construction schedule durations for each trenchless method under consideration. • Perform a cost-weighted risk analysis to determine the most favorable trenchless alternative that is based on anticipated bid price and risk profile. • Recommend trenchless method for design. The Draft Trenchless Methods TM will be sent to the City of Everett for Review prior to a Trenchless Methods Workshop.