What is dredging?

Published May 1, 2012

Q: What is dredging?

A. Dredging is essentially the underwater excavation of a channel.  Throughout the year, sediments within the water column will settle and accumulate within the channel, a process that is known as shoaling.  The shoaled material is removed to the authorized project depth (plus advance maintenance and allowable overdepth) to allow for safe navigation between dredging cycles, a process known as maintenance dredging.

Q:  Why is dredging important and necessary along the Texas coast?

A. If the material is not removed from the channels at the end of the shoaling cycle, the channel will be draft or width restricted resulting in economic losses to the nation and unsafe passage of vessels accessing deep and shallow draft ports along the Texas Coast.  Severe shoaling in the Brazos Island Harbor Channel Jetty Channel and Sabine Pass Channel have impacted the steel and liquid natural gas industries and have resulted in loads being diverted to other domestic and foreign ports.  In addition, natural habitats along the coastline such as the Laguna Madre can be greatly altered by the reduction of saline flow in and out of our estuaries and bays. 

Q:  How does dredging contribute to strengthening our economy?

A. Nearly 30 ports along the Texas Coast handle more than 500 million tons of commerce annually.  According to the USACE Navigation Data Center (2010), Texas is home to four of the top 10 U.S. leading ports including Houston, Beaumont, Corpus Christi and Texas City (in millions of short tons).  Without regularly scheduled maintenance dredging, channels will shoal to critical depths resulting in a significant loss of ship and barge payload capabilities and consequently a substantial reduction in local, state and national economic benefits.  Texas ports and waterways handle 42 percent of foreign crude oil that is imported into America.

Q: What is the dollar value of dredging contracts for the fiscal year 2010?

A. The U.S. Army Corps of Engineers, Galveston District, awarded a total of 17 maintenance dredging contracts and obligated more than $200 million toward dredging efforts in fiscal year 2010 (from Oct. 1, 2009, through Sept. 30, 2010), including both new work, routine critical maintenance, dredge placement area work, gate maintenance at the Brazos River floodgates and dredge channels to restore pre-storm conditions.  Approximately 33 million cubic yards of material was removed from the channels, with over 1.8 million cubic yards used beneficially to nourish beaches and construct wildlife habitats.

Q:  What is done with the dredge material?

A. There are several options for the disposal of dredged material but each project has special requirements or conditions that will dictate which type of placement area is best suited.  The most common placement options are ocean placement or open water, beach nourishment, and confined disposal facilities.  When considering the placement method, the Corps actively seeks disposal methods with beneficial uses including habitat development, beach nourishment, and erosion control.  Beneficial use projects such as the recent beach renourishment project at Padre Island allows the Corps to improve eroded coastlines through the placement of this dredged material while saving taxpayers hundreds of thousands of dollars annually.

Q:  What precautions are taken to ensure that dredging is done with minimal impact on the environment?

A. The Corps keeps environmental considerations at the forefront when it undertakes the design, construction and execution of projects that are crucial to keeping the nation’s waterways safe for navigation.   Maintaining a balance between development and minimizing the impact on our environment is in keeping with our commitment to remain good stewards of our environment. 

One of the ways the Corps prevents damage to the environment is avoiding work during critical ecological seasons.  Sea Turtle nesting season runs from March 15 until Oct. 15 and during this time, contractors stop placing material in critical habitats.  Additionally, the Gulf Coast is known for its migratory bird species and their habitats.  The Corps halts work that may cause impacts during seasons in which certain species make our coast their home and protects our seagrass habitats by avoiding placing any material during the growing season.

For more information about dredging along the Texas coast, contact swa.pao@usace.army.mil.  For more news and information, find us on Facebook, www.facebook.com/GalvestonDistrict, or follow us on Twitter, www.twitter.com/USACEgalveston.