Opportunity
The Port of Corpus Christi on the Texas coast in the western Gulf of Mexico is the third largest port in the US by tonnage, handling more than 6000 vessels each year.
To accommodate the new generation of megaships at the port’s La Quinta terminal, the sea channel on the north side of Corpus Christi Bay had to be made deeper, longer, and wider.
As part of agreeing to a permit, the US Army Corps of Engineers, the federal agency that oversees shipping channels, requires compensatory mitigation to offset the effects of port expansions. In this case, the Port of Corpus Christi Authority was required to create a new estuarine habitat using dredged material, making best use of large quantities of valuable sediment deposits.
Solution
Our design created a seagrass and wetland habitat that exceeds regulatory requirements. The berm covers over 207 acres and is planted with more than 10 acres of smooth cordgrass and over 24 acres of shoal grass.
Both species help stabilize habitats, reduce water turbidity, and are a source of food for fish and invertebrates. Large fields of cordgrass are common near the heads of tidal creeks in the area and our design of the mitigation berm was optimized to enable similar extension growth.
Forecast sea-level rise and wave conditions were evaluated as part of the design process. Dredged material is valuable and has vast potential for beneficial use, including beach restoration, shore protection, and habitat enhancement. More than 11 tons was used to create the 200-acre seagrass and wetland habitat at La Quinta.
Outcome
The first phase of the mitigation project was completed in 2016. An additional 1,500-foot-long section, made from material previously recovered during routine maintenance dredging, was completed in 2017, adding 19 acres of shoal grass.
The vegetation acts an incubator for young fish by providing protection from predators. Common near-shore fish include spotted sea trout, red drum, southern flounder, striped mullet, shrimp, and blue crab, while the berm is a nesting area for seabirds. The project also reduces basin siltation, cutting the frequency of maintenance dredging.
The berm also protects the port and surrounding area from storm surges and erosion. Its protective power was demonstrated in August 2017 when Hurricane Harvey, a Category 4 hurricane, hit the Texas coast, bringing dramatically increased water and tide levels. Wind speeds topped 100 miles per hour and storm surges were in excess of 4.5 feet. The berm dissipated storm waves and there was little damage to the aquatic habitat.