The second of two major sediment diversion projects in Plaquemines Parish, La., is closer to construction following the naming of a contractor to build the $700-million structure that will use mud from the bottom of the Mississippi River to help rebuild the state’s disappearing wetlands.

Louisiana’s Coastal Protection and Restoration Authority (CPRA) on April 8 awarded a construction manager at risk (CMAR) contract to the Louisiana Diversion Co. (LDC), a joint venture of Brown and Root, Massman Construction Co., Parsons Construction Group and Traylor Bros Inc. for the Mid-Breton Sediment Diversion.

The diversion is part of a $2-billion Mississippi River Mid-Basin Sediment Diversion Program planned for the lower Mississippi River. The first diversion, Mid-Barataria (ENR 8/6-13/18 p. 27), 7 miles north of Mid-Breton on the west bank of the river, is already under design by AECOM. Archer Western-Alberici JV was selected last year as contractor for the diversion.

The 75,000-cu-ft-per-second Mid-Breton project, like the Mid-Barataria, will use CMAR delivery, the first such CMAR projects in state history.

“A project delivery analysis was performed in 2016 that looked at design-bid-build, multiple forms of design-build and CMAR,” explains Mid-Basin Sediment Diversion Program Manager Brad Barth. “Because of the complexity of the project, the nature of the permitting process and high-risk nature of marine construction at the project sites, the CMAR delivery model was chosen for both the Mid-Barataria and Mid-Breton projects.”

The CMAR model will allow LDC to provide input on cost, scheduling and constructability, which will help the project team lower costs and speed construction. The LDC team will work closely with Stantec, which was chosen as the project’s designer in February 2018.

“We’re in a race against time, and CPRA is committed to finding innovative and ambitious solutions to address Louisiana’s coastal crisis,” said CPRA Chairman Chip Kline said in a statement.

The pre-construction phase contract is estimated at $12.4 million, with the scope including design of temporary works, constructibility reviews and project cost estimating throughout the design process of the project. Steve Mathies, who is leading the design team for Stantec, last year said the design of the two diversions will not be the same, but the teams working on the diversions will be working together. “If it’s good for our project, it’s good for their project.”

The Louisiana CMAR model includes a second contract for the construction phase.

The estimated construction cost is about $700 million, Barth says. CPRA is expected to begin negotiations with LDC on guaranteed maximum price when the project nears the 95% design phase.

The team recently wrapped up a 5% design package, which has allowed the team to site the project’s location on the river, Barth explains. “We’ll be back out in the river looking at more sediment data collection at both sites, Breton and Barataria, this year for different river events to capture what that sediment looks like at the specific project location,” Barth says.

Immediate next steps include negotiating the pre-construction contract with the selected team, Barth says. “The CMAR be providing constructibility reviews on the deliverables submitted by the designer, Stantec,” Barth says. “Additionally, the CMAR will be generating cost estimates at each major design milestone and is responsible for providing designs of the temporary works features.”

The design and environmental/regulatory processes are expected to continue through 2023, when construction is scheduled to begin. Among the construction challenges the project team has already identified on Mid-Breton are soft soil conditions, dewatering near the levee/point bar and a more complex design on the conveyance channel, Barth notes.

The losing bidders were Mid-Breton Constructors, made up of AECOM Energy & Construction Inc. and James Construction Group LLC; and Kiewit.