By Janet Kirkton, Dredging Industry Steward and
Caitlin Maddock-Bahr, Marketing Consultant
Keeping the Houston Economy Flowing with Amphibious Excavators
After Hurricane Harvey, the shutdown of air, rail, and port operations had an impact well outside the region due to Houston being a multi-modal interchange point. These disruptions are common following natural disasters such as hurricanes, snowstorms, etc., and typically result in high freight costs once commerce resumes in the area. Add to that the fact that two-thirds of the nation’s petrochemical traffic, along with general cargo and container ships, comes through the Port of Houston, one of America’s largest seaports, and we have a problem. The Port of Houston handles about 13 million tons of cargo each year, with about 8,300 vessels docking.
Wind damage from Hurricane Harvey to shipping and port infrastructure was minimal, but an enormous influx of water, sediment and debris entered the Houston Ship Channel, meaning it needed to be surveyed for navigational hazards before it was cleared to reopen to limited traffic on September 1, 2017.
Port Commission Chairman of the Port of Houston Authority, Janiece Longoria, recently spoke at the Port Commission monthly meeting, saying, “We are in desperate need of additional relief to properly dredge the channel so that it can accommodate normal commerce at its authorized depth and width.”
Dredging Today reports that Chairman Longoria has noted that ten feet of sediment has collected due to the immense amount of floodwater carrying silt into the channel, and this very seriously limits commerce if not addressed. In fact, a 2010 study conducted by the Texas Transportation Institute reports that a loss of just one foot of depth in the Houston Ship Channel would cost the U.S. economy millions of dollars per year.
Where will all that sediment go?
The sediment that is dredged in order to maintain the channel needs to go somewhere. It’s always preferential to beneficially reuse dredged materials when possible, however the estimated 1.39 million cubic yards of sediment removed from the Houston channel is destined for upland disposal in a Dredged Area Management Program (DAMP) placement site. Over time, the sediment naturally dewaters and can later be harvested.
DAMP sites are areas enclosed by a levee that accept sediments that have been dredged from nearby ship channels. A few islands also serve this purpose. The sediment is hydraulically dredged and transported as a slurry to the site by a pipeline and spread out in layers approximately a foot deep.
Maintenance dredging is typically an ongoing process required to keep the ship channel at a minimum depth of 45 feet to allow large ships access. Without the port and ship channel being fully operational, petrochemical tanker ships’ routes have been cut off, restricting their ability to reach refineries and chemical docks in the upper portions of the channel.
Working in the water will become more and more necessary as restoration efforts continue in areas affected by storms such as Harvey, and equipment that is built to withstand those conditions is essential not only from a maintenance standpoint but also from a safety perspective. Specialty equipment, such as these amphibious excavators, are an essential part of recovery and restoration efforts, just as they have been essential for the maintenance of DAMP sites for a long time.