Tetra Tech INCA as part of the design team developed structural designs for the University Street Underground Transit Station. The station is located approximately 70 feet below-ground and includes ancillary structures such as station entrances, vent structures, traction power substation, and underpinning of existing buildings. INCA prepared the preliminary and final plans for this underground station, approximately 573 feet in length.

Tetra Tech INCA designed and evaluated multiple approach wall alternatives, including fixed, floating, and float-in designs. An alternative was selected and INCA is now moving forward with final design elements for approach walls for the lock. The walls are designed for anticipated environmental loads, barge impact, earthquake, and construction loads. Nose Piers are provided at the end of the approach walls to protect them from head-on barge collisions.

Tetra Tech INCA worked directly with the Pittsburgh District and their contractor to optimize the design of a new floating guard wall for a new lock at Charleroi. Improvements in design are anticipated to provide a lower cost and a better performing structure. Some of these improvements included changes to rebar details to reduce installation time, changes in the concrete mix design to improve placement, revised ladder design, elimination of an intermediate joint to improve flotation and reduce cost, and simplification of wall armor embedments.

Tetra Tech INCA performed design computations, finite element stress analyses, and detail design for Swift No. 2 surge arresting pipeline and structures.

The effort comprised:

• One 15’10” square to round intake transition
• Two 15’10” diameter bends
• One 15’10” diameter pipeline (penstock) on a 19 degree slope
• One 15’10” x 11’4” bifurcation
• Two 11’4” diameter pipelines each with a bend and a 11’4” x 6’0” reducer

The design and analyses included the design of all site handling, supports and erection devices, internal temporary stulling rings to resist concrete embedment loads, as well as hold down ties / supports for concreting.

USACE, Walla Walla District retained the Tetra Tech INCA, as part of a joint venture, to develop final designs and plans and specifications for the repair and refurbishment of clarifiers on the System 1 reuse treatment facilities and for the retrofitting of the existing fluidized bed sand filters at the Dworshak National Fish Hatchery near Orofino.

The plans modified five existing sand bioreacters to incorporate a continuous cleaning biofilter (CCBF) system using plastic bead media; modified the piping; and repaired the clarifiers and associated systems. The design included repair of the clarifier system in all eight of the clarifiers, cleaning of the clarifier ponds, replacement of the sludge pumps, and electrical connections and controls for the replaced equipment.