The Big River Coalition recently shared the attached document with the National Transportation Safety Board (NTSB) detailing the vertical clearance of the seven bridges that cross the Mississippi River Ship Channel (MRSC) to respond and support the findings noted in the NTSB Marine Accident Brief issued bearing number DCA19FM003 (July 16, 2020).  DCA19FM003 detailed the allision at the Sunshine Bridge (Mile 167.4 Above Head of Passes [AHP]) on the Mississippi River (Burnside, LA) and a crane barge on October 12, 2018.  DCA19FM003 is available for download at the following link:

The Coalition expanded on the “air gap” disparities noted in DCA19FM003 which documented the confusing process that mariners are expected to utilize to calculate the vertical clearances of bridges crossing the MRSC.  DCA19FM003 documented the vertical clearance formula that mariners are expected to utilize to safely navigate under the Sunshine Bridge, while the BRC documented the same information for all seven of the bridges crossing the Mississippi River Ship Channel.

The Coalition felt it was important to expand on the findings in the NTSB report and to manifest the methods utilized to calculate the vertical clearance at these bridges while documenting sources of inaccuracy and challenges in performing the vertical clearance calculations. As the information was being prepared it was discovered that the U.S. Army Corps of Engineers (USACE) had documented the use of the wrong river gage in the calculation formula for the Baton Rouge I-10 Bridge vertical clearance formula. The USACE promptly agreed that it had documented the use of the wrong river gage in their calculation formula and responded quickly to update the formula and align it with the proper river gage.  The previous calculation formula was listed as, 174 feet minus the Port Allen Gage.  The corrected formula is 174 feet minus the Baton Rouge Gage, this adjustment has been made and was also adopted by the U.S. Coast Guard.

The first attachment details the vertical clearance formula of the seven bridges crossing the MRSC and also reproduces the efforts of the USACE to update the vertical clearance formula for the Baton Rouge I-10 Bridge.  The second attachment requests expanding the National Oceanic and Atmospheric Administration’s (NOAA) Lower Mississippi River Physical Oceanographic Real-Time System (LMR PORTS®) program to include air gap sensors at six of the seven bridges that cross the MRSC.  The Big River Coalition has also worked with NOAA to make adjustments and increase the LMR PORTS®  program.  The document also details the adjustments made to the two current air gap sensor display pages (Crescent City Connection and the Huey P. Long Bridge), this new template standard will be followed as additional air gap sensors are added to the LMR system.  The Baton Rouge I-10 Bridge is set to be outfitted with a new air gap sensor in the LMR PORTS®  suite of sensors over the next few months and the Coalition will continue to advocate for an additional three air gap sensors to be added to LMR PORTS®.  There are other adjustments to the LMR PORTS®  sensors in the works that will be detailed at a later date, including changes to the two current meters presently included in the LMR PORTS®suite.

The Big River Coalition continues to request additional federal funding to increase both the NOAA PORTS®  program to promote navigational safety and for the USACE to increase navigational safety by maintaining authorized channel dimensions to avoid disruptions to our fragile supply chain.