First U.S. federal channel using USACE survey data receives improved quality classification from NOAA

By Rachel Medley

The U.S. federal channel in the Delaware Bay is vital to maritime commerce, leading deep draft vessel traffic to and from the major ports of Wilmington, Delaware,  Philadelphia, Pennsylvania, and Camden, New Jersey. To navigate this federally maintained waterway safely and efficiently, mariners rely on the surveyed depths displayed on nautical charts. The U.S. Army Corps of Engineers (USACE) Philadelphia District regularly surveys this area, utilizing sophisticated techniques and equipment to map the depths of the seafloor. NOAA’s Office of Coast Survey, in turn, adds quality classifications to these channel depths and displays them on the nautical chart.

The portion of the federal channel from Newbold Channel Range down to the mouth of the Delaware Bay is the first waterway in the U.S. to have an improved quality classification assigned to USACE survey data—category of zone of confidence (CATZOC)  A2. Improving survey quality and upgrading the CATZOC classification allows operators to accommodate smaller margins of error while still ensuring that navigating maritime approaches and constrained environments remain safe. These decreased tolerances allow ships to maximize their loads, ultimately increasing inbound and outbound cargoes.

“This is a huge leap forward toward the sophistication of nautical charts, and will help the maritime sector along the Delaware River. I want to commend the men and women at NOAA’s Office of Coast Survey and the Army Corps of Engineers District Philadelphia for working together to provide safer timely high-quality data for maritime commerce. I applaud Commerce Secretary Ross for recognizing the vital role that NOAA’s Coast Survey provides to the maritime industry and thank him for this outcome. This synergy between NOAA and the Army Corps is exciting to see, and I support efforts to replicate this pilot project in other ports and waterways around the country.”

  • U.S. Senator Chris Coons (D-DE)
View of the Delaware River from MSC Gayane outbound off Fort Miffilin Range.
View of the Delaware River from MSC Gayane outbound off Fort Mifflin Range. Credit: Captain J. Stuart Griffin, Mariners’ Advisory Committee Chairman (MAC) and Delaware River and Bay Pilot.

Allowing additional draft. What’s it worth?

Upgrading how NOAA encodes USACE channel depth data reduces additional safety margins applied to the draft of large ships during transit and berthing operations. The USACE District Philadelphia is in the process of deepening the Delaware River from Philadelphia to the sea, with a controlling depth in the federal channel from 40 feet to 45 feet (from Beckett Street Terminal north the channel remains authorized at 40 feet). Every foot of draft represents a significant dollar amount in the shipping industry depending on the type of cargo the ship is carrying. For instance in Long Beach, California, for every extra foot of draft allowed by the port, tank vessels can add $2 million of extra product. As ships load cargo, the draft of the ship increases—in the case of the Delaware River, the draft cannot exceed the 45-foot controlling depth (once USACE completes dredging) or the ship will run aground.

Shipping companies and insurance underwriters determine the maximum draft allowed for a vessel during transits of waterways in U.S. ports, adding a margin of error to the draft for safety. In some cases a safety margin of 25-30% may be added, ultimately resulting in dollars lost for the shipping and terminal operators. Not to mention, negating the expense and time involved in dredging a channel. The navigational tolerances are determined using guidelines that include the known quality of survey data in a particular waterway. The better the quality of the survey, the lower the risk associated with the ship transit, resulting in additional cargo loading per transit.

What is CATZOC?

Survey data within an electronic navigation chart (ENC) is encoded with a data quality indication known as CATZOC. CATZOC quality helps the mariner determine the accuracy of charted conditions on the seafloor at the time of the last survey. In particular, the mariner should understand that nautical chart data, especially when displayed on navigation systems and mobile apps, possess inherent accuracy limitations. CATZOC quality designations, A1-D, are the specifications that were met at the time of the survey.

Currently all federal channels are designated as a CATZOC B if the USACE has collected the data. This a recent development as previously all federal channels were designated as a CATZOC ‘U’ for Unassessed. Rear Adm. Shep Smith, Director of NOAA’s Office of Coast Survey, was asked by Intertanko, a maritime association that represents the interests of the tanker industry, to remove the ‘U’ designation on ENCs as it was impeding the industry’s ability to do a proper risk model assessment of ships entering U.S. ports. Nationwide, the USACE is the federal authority for maintaining federal channels; NOAA does not normally assess USACE surveys and as such designated all surveys as a CATZOC B.

USACE survey techniques factor into CATZOC quality

The maintenance of all federal channels falls under the jurisdiction of the USACE, and as such, Coast Survey recognizes the USACE as the authority for survey data acquired in these active waterways. USACE districts around the country help the flow of commerce in and out of the nation’s busiest ports and Coast Survey applies data from 22 of these districts to nautical charts for safe navigation by deep draft vessels. The USACE districts use sonar equipment to measure sediment movement within the channel to maintain channel-controlling depths and determine dredging needs.

The USACE Philadelphia District is unique in that it is fully utilizing its multibeam sonar equipment, which has the capacity to survey large swaths of the seafloor and detect features and obstructions that might be harmful to deep draft vessels. As vessels in the nation’s waterways continue to grow in size, USACE districts that are utilizing their multibeam systems are helping to ensure that the general bathymetry of the seafloor bottom is well known at the time of the survey. This is particularly important as vessel drafts are nearing the seafloor bottom in port areas across the country, running higher risk of hitting a feature or object in the waterway.

“The Delaware River port community is taking steps to utilize the planned deepening of the main channel.  We are already seeing arrivals of post-Panamax sized vessels that require special transit considerations and planning. Our valued partnerships with USCG, USACE, and NOAA are critical to the safe movement of deep-draft commercial traffic in our waterway. As the USACE nears completion of the project to deepen the main shipping channel, improvements in sounding data quality have enabled NOAA to provide safety assurances to shippers in the form of improved CATZOC designation for the estuary. This has real-world relevance to ship owners and charterers who move vessels on the Delaware and will allow them to more effectively utilize the full channel depth upon completion of the deepening project.”

  • Capt. J. Stuart Griffin, Chair of the Mariners’ Advisory Committee (MAC) and Delaware River & Bay Pilot

Updating NOAA nautical charts

Coast Survey is exploring various ways of changing and improving charted information for the mariner as outlined in the National Charting Plan. Coast Survey is working with USACE Philadelphia District to determine the CATZOC quality of the survey data acquired in the Delaware River. The CATZOC value of the surveys collected over the past year by USACE District Philadelphia have been designated by Coast Survey as meeting a CATZOC A2 standard. There is a significant improvement in survey quality designation from a CATZOC B to a CATZOC A2. CATZOC A2 seafloor coverage indicates that the full area was surveyed and allows for the detection of significant seafloor features. CATZOC B seafloor coverage does not have sufficient quality or resolution, indicating that while hazardous objects are not expected, they may exist and may be undetected because of the survey quality.

Coast Survey has encoded ENCs with the CATZOC A2 quality in portions of the federal channel along the Delaware River that are surveyed by the USACE District Philadelphia utilizing robust multibeam survey methods. There is not a refresh rate or time frame required with international CATZOC standards, however, USACE Philadelphia District typically resurveys the main navigation channel on an annual basis using the same multibeam survey techniques that NOAA used to assess the current CATZOC value.

Potential impact to shipping companies and terminal operators

For the portion of the federal navigation channel from Newbold Channel Range down to the mouth of the Delaware Bay, this designation will decrease the risk margin placed on ships transiting the waterway and make fuller use of the actual controlling depths in this waterway.  Additionally, “this could potentially help to lessen the expense and risk of lightering operations,” reports Eric Clarke, marine operations cargomaster at Philadelphia Energy Solutions.  Commonly, shipping companies whose risk models are calculated using the CATZOC B quality levels mandate lightering operations before transiting to terminals where water depths are more restrictive.

Through coordination efforts between USACE Districts and Coast Survey, federal agencies are working to serve up better data and information to the mariner so they can make more informed decisions to keep commerce moving effectively and safely in the nation’s busiest waterways.


The author, Rachel Medley, is chief of the Customer Affairs Branch at NOAA’s Office of Coast Survey. She also serves as the NOAA liaison to the Delaware River and Bay for navigation issues. For more information, please contact Rachel.Medley@noaa.gov

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