Photo by Jeff Rubenstone/ENR

Several barges at the Tappan Zee Bridge project site have come unmoored recently.

The New York State Thruway Authority said on March 31 that it will withhold up to $1 million per month in progress payments to Tappan Zee Constructors LLC due to repeated incidents of construction barges at the site of the new Tappan Zee Bridge coming unmoored and drifting down the Hudson River. The most recent incident took place on March 30, when a material-laden barge drifted three miles down river before it was recovered.

Thruway Authority spokesman Brian Conybeare called the incident "unacceptable" and said project leaders are investigating. Peter Sanderson, Thruway Authority project director, said in a statement that portions of the payments would be withheld "until TZC delivers a contractually required corrective action plan."

TZC, a joint venture of Fluor, American Bridge, Granite Construction and Traylor Bros., is building a $3.9-billion replacement for the aging Tappan Zee Bridge, north of New York City. The design-build project calls for a pair of cable-stayed spans that will carry the New York State Thruway over the Hudson River.

In a press statement on April 1, Carla Julian, TZC community outreach manager, said an investigation into the March 30 incident found that "high winds and rough seas caused two, three-inch lines from the mooring buoy to the barge to fail from severe abrasion and high heat created from friction."  Julian says TZC is making changes to the way project barges are secured, including switching to stronger mooring lines with abrasion-resistant sleeves.

This isn't the first time a barge associated with the Tappan Zee Bridge project has caused problems. In January, two barges came unmoored, with one drifting 13 miles downstream before being recovered. Another barge broke loose in September. TZC said in their April 1 statement that the barge problems in those incidents were due to a different issue, as they were tied not to mooring buoys but only to other barges. Since then, TZC has changed the orientation of barges on the river to reduce stress on the lines.

The most serious incident at the site happened on the evening of July 26, 2013, when two people were killed when their boat collided with a barge near the bridge. A U.S. Coast Guard investigation found the barge was moored and adequately lit, but TZC added more lighting to their barges in the weeks after the incident.

Ongoing issues with barges and river traffic are a major concern for the project. TZC estimates there will be more than 100 barges operating simultaneously in the Hudson River during the peak of construction, including several massive barge-based cranes.

The Thruway Authority announced at public meetings on March 26 and 27 that TZC will be deploying GPS tracking equipment on all barges and boats operating in the construction zone around the bridge. According to Conybeare, this tracking information will be available in real time on the project's website, www.newnybridge.com.

The barges are being used in the installation of permanent piles for the new bridge. The bridge design demands nearly 1,000 piles, including hundreds of 330-ft friction piles. "There's about 100 piles installed now, and we're also doing sitework on the approaches," says Walter Reichert, TZC vice president and project manager. "We're 80% to 85% complete on the final design, but we're still fine-tuning."

"The design is largely complete," says Sanderson. "Within two months, they'll be starting work on the foundations for the main piers. Precast segments for the approach spans will be arriving in June."

"But the No. 1 thing on this project is safety," Sanderson told ENR. "Whatever's done, it has to be done safely."