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.
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.
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.”
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.
The slurry that is pumped into DAMP sites resembles a shallow lake. When the sediment settles, the excess water is carefully drained off. A continuous cycle of ditching, draining, and drying is needed to remove water from the sediment and maintain capacity of the site.
With the larger footprint and lower ground pressure, amphibious excavators provide a simple, cost effective solution with increased mobility in wet work sites. An excavator with a standard steel undercarriage would be unable to maintain flotation in these wet underfoot conditions, CAT reports on its blog.
Steve, an operator with 25 years of experience, has been using a Cat® 324E with an EIK AM250 amphibious undercarriage and a 60 foot (18.5 m) EIK long reach front to maintain one of the DAMP sites near the Houston Ship Channel.
“The best feature is that this machine does not get stuck. There is plenty of power with the 4 motor multi-synchronous hydraulic motor direct drive system, and with the enclosed hydraulic drive there is not an exposed rusty drive chain to seize up like most other machines.”
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.