This $12.4 million project for the North Texas Municipal Water District involves 2,534 linear feet of 118-inch excavated diameter tunneling. The tunnel will consist of 4-flange liner plate and will house 84-inch steel carrier pipe. It will be driven through Austin chalk with a double-shielded, open-faced, gripper-type machine with articulated steering.

Tunneling was completed on Jan. 6, 2021. Stiver Engineering provided tunnel design services for the project. We performed analysis and design of launching and receiving shafts and the tunnel liner. The shafts were designed to extend through the transition between the soil and rock layers. The top 30 feet of the shaft was designed using ring beam and liner plate. Rock anchors and shotcrete were used in the bottom portion of the shaft in the limestone.

The Integrated Pipeline is a $48.5 million joint water supply project between Dallas Water Utilities and Tarrant Regional Water District. It involves building 150 miles of pipeline to transport up to 350 million gallons water daily from three East Texas Reservoirs into the Metroplex to increase reliable water access. Crews are installing 4,400 linear feet of pipe using an open face tunnel boring machine with hydraulic jacks and concrete segmental lining. The project recently reached a new milestone when the new tunnel under Trinity River was completed. Workers are now beginning to add 50‐foot sections of 108‐inch diameter steel pipe.

Stiver Engineering performed full design work for the IPL tunnel. Our work included several trench safety plan designs, pipe buoyancy and support calculations, shoring design, a design for a CMU bulkhead, and an alternative design using steel plates and members for grouting abandoned tunnel. We also created a plan and profile drawing set for a new tunnel profile including new geotechnical data, as well as analysis and design for increasing the depth of an existing liner plate and ring beam shaft, among other services.

The design/build project scope included construction of approximately 3,802 linear feet of 108‐inch water line including 2,614 linear feet of tunnel under the Trinity River and the remainder in deep open cut segments along the proposed alignment of Section 17. Other aspects include tunnel launch and retrieval portals/shafts, deep open cut approach ramps with temporary shoring at approximately 12:1 slope, pipe laying within approach ramps and tunnel initial support, pipe encasement with flowable fill and reinforced concrete, tunnel grouting, a 15.6‐foot diameter custom designed tunnel boring machine, and precast segmental tunnel lining.

The $142 million Schoharie Reservoir Project in Gilboa, New York – which is expected to be complete in the year 2020 – includes the construction of an intake structure at the bottom of Schoharie Reservoir, more than 2,000 feet of subsurface tunnels, and a valve chamber along Schoharie Creek. Once completed, the tunnel and valves will provide New York City’s Department of Environmental Protection with the capability to release water from the reservoir into Schoharie Creek to facilitate dam maintenance, respond to potential emergencies, mitigate flood risk for downstream communities, and enhance downstream habitats for fish and wildlife.

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Stiver Engineering often provides clients with construction consulting through liner plate shaft, ring beam, and timber lagging shaft designs. Depending on the project, these services can also include portal designs and thrust block designs.