TIC 2017-11-14 Item 2D - Contract Amendment #1 - Riverton Creek Flapgate Removal Design with OTAK Inc

Browse Search

Exhibit A-1 Scope of Work Continued maps. We assume Otak, Inc. (Otak) and the City of Tukwila (City) will provide as -built information for the existing bridge and wall. 2. Review preliminary drawings for the planned project including trail improvements, flapgate removal and culvert modifications, and upgrades to the bulkhead. 3. Complete a site reconnaissance to observe the existing surficial conditions of the site. 4. Develop approach for tie -back and sheet pile wall analyses. 5. Explore subsurface conditions at each end of the planned pedestrian bridge by completing two geotechnical borings to depths of about 50 to 60 feet. The preliminary depths were estimated to determine the contact elevation between the anticipated sand layer and lower very soft organic silt layer. It may be necessary to drill deeper borings through the lower organic silt layer, depending on the foundation loads and seismic requirements of the bridge structure. The drilling services will be subcontracted to GeoEngineers and will be completed using hollow -stem auger or mud rotary drilling equipment. We will contact the Washington State One -call service to locate the explorations in areas that are clear of underground utilities. We will also use a subcontract a private utility locate service, to locate utilities not covered by the one -call service. The drilling will generate excess soil that will not be replaced in the borehole. Our scope and fee estimate assumes that the soil cuttings will be left on site and that the site restoration, is not necessary. If the soil cuttings will need to be hauled off- site, then additional expenses will be needed. The borings will be backfilled in accordance with the Department of Ecology's requirements. 6. Evaluate pertinent physical and engineering characteristics of the site soils based on laboratory tests from the borings. The laboratory tests will include moisture content, grain - size distribution, Atterberg limit determination, and percent fine contents, as appropriate. 7. Prepare a draft and final geotechnical design report. Our specific scope of services for the design -level report will include the following: • Project vicinity map and site plan showing the location of the geotechnical exploration with • respect to the proposed development including new or previously completed explorations. • Previous boring logs and boring logs and laboratory test results completed for this study (if • completed). • Summary of subsurface soil and groundwater conditions. • Seismic design recommendations based on the current International Building Code (IBC). • Foundation design recommendations (axial and lateral pile capacity) for the proposed • pedestrian bridge. We have assumed the foundations will consist of deep piles. • Anchor recommendations for stabilization of the existing sheet pile wall. • Recommendations for stability of site slopes, including stability evaluations and • recommendations for the existing steep slopes in front of the sheet pile wall where tie -backs • may be needed for the planned project. W:APW Eng\PROJECTS\A- DR Projects\Riverton Flap Gate Removal (99830103 98-DR03)\Consultant Selection\Phase 2\contract\Amendment #1\Riverton SOW_Amend 1_17_1027.docx 5 95