Brown and Caldwell Inc. 3/9/2022 Amendment 1

Portal 4 Improvements Geotechnical Services Scope of Work Valve Vaults • Modulus of sub-grade reaction. • Buoyant-uplift risks associated with groundwater. • Capillary break material recommendations. Spread Footings and Soil-Retaining Structures • Settlement values (total and differential). • Minimum depth to bottom of footing. • Backfill and compaction recommendations. • Temporary shoring wall design parameters for the construction phase and final sheet pile wall design criteria for permanent sheet piles as appropriate to the project and site. Seismic Design • Seismic soil profile and Site Class per International Building Code (IBC) (governing edition or other governing code for the site location). Defer to the more stringent code. • Description of seismic setting, historical seismicity, and location of closest seismic records used in the site evaluation. • Soil pressures on walls due to seismic loads, including recommendations as to whether these soil seismic pressures are to be combined with active or at-rest static soil lateral pressures. • For Seismic Design Category (SDC) C, D, E, or F, the geotechnical report shall include an evaluation of slope instability, liquefaction, total and differential settlement, and surface displacement due to faulting or seismically induced lateral spread or flow.The report shall contain recommendations for appropriate foundation designs or other measures to mitigate the effects of these hazards, where approved by the authority having jurisdiction. • For SDC D, E, or F, additional geotechnical report requirements shall be addressed per American Society of Civil Engineers (ASCE) 7-16. • The geotechnical consultant shall review seismic specifics with the BC structural engineer for clarity of final needs and concerns. Other • Rock or soil anchors, sheet piling, shoring, rolling surcharge, etc.,that may be appropriate based on the project and site. • Recommendations for road improvements/replacement of the gravel road sections for the case that the valve vaults for transmission line 2 and 3 are installed at the location of the existing roadway at the bottom of the Portal 4 slope (see Exhibit A, page 3). • Recommendations and design parameters for contractor designs related to means and methods shall be provided—including, but not limited to, dewatering, temporary excavations and shoring systems, etc. However, the geotechnical consultant shall avoid defining or designing means and methods for the contractor and present their directions as recommendations/suggestions to the contractor. Ultimately, the contractor shall own their choices for means and methods. IBrown Am Caldwell 3 Attachment A Geotech Services SOW