The US Army Corps of Engineers (USACE) is responsible for maintaining and improving nearly 12,000 miles of shallow-draft (9'-14') inland and intracoastal waterways and 13,000 miles of deep-draft (14' and greater) coastal channels throughout the United States as well as numerous anchorages, breakwaters, harbors, locks and dams, protective jetties, and turning basins. To provide safe navigation and mooring for military, commercial, and private maritime vessels, USACE keeps each of these areas at a specified depth by dredging over 200 million cubic yards of material annually.
To determine where to dredge and how much material needs to be removed, USACE conducts regular hydrographic surveys to monitor channel conditions. Survey data is collected through single-beam or multi-beam sonar from small craft, large ships, and airplanes. This data is plotted on maps to identify “shoaled” areas—areas that have become shallower than the required depth and, therefore, require dredging. The results are printed for use by dredge operators and inspectors and compiled into various USACE reports, including Channel Condition Reports (CCRs), which identify the minimum depth of each channel quarter of the navigation channel, and Channel Condition Indices (CCIs), which identify the percentage of time a navigation channel has met its Congressionally authorized project dimensions. USACE is also required by law (33 CFR § 209.325) to supply channel condition information to the National Oceanic and Atmospheric Administration (NOAA), so channel depth information can be included on its nautical charts. (See “Appendix B—33 CFR § 209.325 – Navigation Lights, Aids to Navigation, Navigation Charts, and Related Data Policy, Practices and Procedures” for details).