February 2013 - Infrastructure Digest

Tunnel Beneath the Bay

“The new pipe will be installed in a dedicated tunnel constructed roughly 100 feet below the bay floor. Known simply as the “Bay Tunnel,” the new conduit is 15 feet in diameter and more than five miles long. The digging is done by an earth pressure balance tunnel-boring machine (TBM), a type of tunneling system well suited to the dense clays that make up much of the bay floor. To launch the TBM, the project’s tunnel contractor, Michels/Jay Dee/Coluccio Joint Venture (MJC) excavated a shaft 58 feet in diameter and 124 feet deep in East Menlo Park on the west side of San Francisco Bay.

According to MJC Project Engineer Ed Whitman, the TBM and launch shaft are normal parts of a major tunneling project. But the Bay Tunnel contains an important distinction from Whitman’s past projects. In other TBM-built tunnels, several vertical access shafts (Whitman calls them “manholes”) are built at intervals along the tunnel. In a similar sized-tunnel that Whitman worked on in Ohio and California, manholes were spaced roughly 1,000 to 1,500 feet apart. Among other functions, the shafts enable project surveyors to connect geodetic control points on the surface to the control points in the tunnel, making adjustments and corrections as the TBM moves ahead. Because the Bay Tunnel is under a body of water, manholes aren’t possible. As a result, all the survey control (essential to steering the TBM) is tied to one end of the tunnel. “It’s like taking a five-mile shot off a 50-foot backsight,” says Whitman. “From the survey perspective, it’s not for the faint of heart.””

Why should you read this? If tunneling 100 feet under San Francisco Bay doesn’t get you interested… maybe you shouldn’t be in infrastructure? POB, January 2013

Sediment Mapping by Air

“Paradoxically, the effectiveness of the dam for sediment control has led to a serious issue confronting the reservoir: sediment deposition is reducing reservoir storage capacity and causing significant aggradation upstream within the Rio Grande channel. Monitoring sediment volume, spatial distribution, and rate of deposition is of paramount concern to the Corps of Engineers. Consequences for the operation and life expectancy of Cochiti Dam and Reservoir are at stake.”

Why should you read this? An interesting survey niche, and a look at an infrastructure peril you may not know much about. Aerial Mapping 2012

Crucial Post-tornado Imagery

“As we waited for the weather to clear, our crews began planning their flight lines. During this process, we made a decision that proved critical to the success of the project. We put word out to the Missouri GIS Advisory Committee (MGISAC) listserv about our plans and asked if anyone had a map of the tornado path. The response was remarkable. Within minutes, the Missouri National Guard and the State Emergency Management Agency (SEMA), both with boots on the ground, delivered remarkably detailed shapefiles delineating the path of destruction…

Working with a combination of Z/I Imaging DMC processing software and our own proprietary systems, the production team orthorectified the one-foot images first using the natural color bands and existing elevation data. Once the 40 one-foot exposures had been orthorectified, they were used to filter out some of the three-inch exposures that contained no damage as a means of expediting the remaining processing.”

Why should you read this? Weather events keep happening, and surveyors are often first responders, at least in terms of infrastructure. This is a good case study on rapidly gathered aerial data used to assess damage and plan reconstruction. Professional Surveyor, 2012

Reduce, reuse, recycle: Turning wastewater into energy

“The False Creek Energy Centre in Vancouver, B.C., is the first application of localized sewer heat recovery in North America — and the only one to use untreated sewage. For about two years, the plant has provided hot water and heating for the Neighborhood Energy Utility (NEU) in Vancouver, a city of about 650,000.

The $30 million False Creek Energy Centre services a portion of the city seeing significant new building development — about 2.7 million square feet, which is expected to grow to about 7 million square feet.

The plant supplies 100 percent of the heating and hot water demand — 70 percent from sewage heat recovery and 30 percent from natural gas boilers, according to Chris Baber, Vancouver’s NEU manager.”

Why should you read this? It’s a successful, locally popular biomass facility, and a wastewater treatment plant. Fascinating. TPO, January 2013

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