As part of a major infrastructure project at the Schoharie Reservoir in Gilboa, New York, Stiver Engineering provided a variety of services for a low-level outlet designed to release water downstream into Schoharie Creek to facilitate dam maintenance and emergency response, mitigate flood risk, and enhance downstream habitat for fish and wildlife. The work includes construction of a 9.5-foot diameter micro-tunnel at a depth of 160 feet. Stiver provided designs for the gate shaft as well as analysis of the steel jacking frame for the tunnel machine and steel pipe. We also provided trench safety designs, thrust block designs, steel pipe casing designs, anchor bolt attachment designs, and a structural review of the Herrenknecht tunnel launch seal and pipe break frames, among other services.
Stiver Engineering performed analysis and design work for rock anchors and HSS steel frames for a 44.5-inch diameter pipe support inside a 96-inch diameter tunnel. The supports were designed for critical load combinations generated from buoyant forces and self-weight of the pipe.
The Mill Creek Drainage Relief Tunnel is a construction project that will bring needed infrastructure improvement to east Dallas, Texas. It will include 26,385 linear feet of tunneling at a 30-foot finished diameter with eight intake shafts and six lateral tunnels excavated by roadheader or excavators/breakers. The tunnel is being driven through Austin chalk by a Main Beam Robbins tunnel boring machine (TBM).
Stiver Engineering provided construction consulting services for the contractor prior to and during the tunnel construction. Our services included several trench safety plan designs, a sound wall design using steel soldier piles and acoustic panels, and a removable shaft cover and rigging details for several liner plate shafts. We also created a design for attaching the access cage ladder and landings on the ring beams of the liner plate shaft and on the vertical rock face. Other work included traffic control plans and shoring designs for access shafts, shotcrete trolley system for lining the tunnel, concrete collars, steel bulkheads, supporting existing utility lines, and a starter tunnel/gripper wall for the TBM.
The tunnel, which stretches from the State-Thomas District in Uptown Dallas, through Mill Creek and Peaks Branch, will be constructed mostly underground with little impact to neighborhoods. Once complete, the approximately 5-mile-long tunnel will sit 70 to 100 feet below ground to provide flood relief.
The Mill Creek Drainage Relief Tunnel is a five-mile underground tunnel that will provide 100- year flood protection for nearly 6,000 commercial and residential properties in the east Dallas area, including Baylor Medical Center. The current drainage system in these areas was constructed 50 to 70 years ago, and only provides a two- to five-year flood protection. Major flooding that occurred in 1995, 2003, 2006 and 2009 crippled these areas and showed dire need for the construction of this drainage relief tunnel. The Mill Creek/Peaks Branch/State-Thomas Drainage Relief Tunnel will improve stormwater management resulting in saved lives, protection of schools, medical facilities, residents and streets. Prior to construction beginning, a TBM will be constructed on site. By using a TBM, there will be minimal utility relocation, as well as minimal street and traffic impacts. Once complete, the tunnel will be approximately 30 feet in diameter, and will be designed to carry a maximum flow of nine million gallons per minute. This provides exponential relief of flooding during large rain events. The tunnel will have six intake sites along the alignment. These include:
- Woodall Rodgers Intake – Intersection of Woodall Rodgers Freeway and Maple-Routh Connection
- Mill Creek Intake – Intersection of San Jacinto Street and Apple Street
- Peaks Branch Intake – Intersection of North Carroll Avenue and Victor Street
- Peaks Branch 2 Intake – Intersection of E R L Thornton Freeway (I-30) and South Hill Avenue
- East Peaks Branch Intake – Intersection of Bank Street and Herndon Drive
- Outfall – White Rock Creek at Barber Avenue
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.
The Waterloo Park project, Austin, Texas, specified that the flood waters stretching from Waterloo Park to Lady Bird Lake be diverted 70 feet below ground through a concrete shaft and tunnel to be discharged into Lady Bird Lake 1 mile downstream. The project removed an estimated 50 acres from the floodplain in Downtown Austin.
Stiver Engineering provided construction consulting by designing the cut through the topsoil and limestone at the headworks facility in Waterloo Park. We also designed the cast-in-place reinforced concrete for the first section of the tunnel, the reinforced concrete and rock bolt retaining walls upstream of the intake structure, and a reinforced concrete temporary bulkhead within the tunnel.