NCDOT Vessel Height Survey Flawed
NCDOT has just completed a second vessel survey on
Gallants Channel and is currently compiling the data for a second Vessel Height
Survey Report to be presented to the Coast Guard. NCDOT is using this report to
“negotiate” with the Coast Guard to allow them to build a 65 foot fixed span
bridge. This report is being generated more than 5 years after the Coast Guard
first informed NCDOT that a 65 foot fixed span bridge would not meet the current
and future navigation requirements for Gallants Channel as required by federal
The recent 5 month survey was required by the Coast Guard
to increase the sample period from the previous, grossly inadequate, 28 day
sample period used in NCDOT’s first Vessel Height Survey Report (Gallants Channel Bridge Replacement Project Vessel Height
Survey Report FINAL December 2012).
Unfortunately, this recent data collected in NCDOT’s 5
month survey is also insufficient to be used for a valid Coast Guard Vessel
Height Survey Report for the following reasons:
The authorized navigation clearance for Gallants Channel was erroneously and
illegally restricted to 67 feet during most of NCDOT’s 5 month sample period.
The sample period of 6 months is still insufficient to accurately measure the
reasonable needs of navigation for Gallants Channel.
The method used for measuring mast
heights is flawed – there is a gross margin of error in NCDOT’s calculation for
The report does not meet the
requirements for Navigational Evaluation put forth by the USCG BRIDGE PROGRAM
REASONABLE NEEDS OF NAVIGATION WHITE PAPER Version 1.1, October 5, 2012
Illegal Authorized Navigation Clearance Restriction
In November 2012 the Army
Core of Engineers abruptly changed the Authorized Navigation Clearance for
Gallants Channel on all applicable navigation charts (charts
and 11547). This decision was
based on an erroneous interpretation of federal regulation
CFR 33 322.5.
After several communications that ultimately involved
Secretary of the Army John McHugh, it was determined that the Army Core of Engineers
misinterpreted the regulation. On March 4th 2013, Secretary McHugh
directed the Army Core of Engineers to withdraw the changes to the authorized
Click here to see Sec. Army Letter
In subsequent meetings with the Army Core of Engineers, it
was determined that not only did the Army Core of Engineers misinterpret the
regulation; they did not have authorization to change the Authorized Navigation
Clearance in the first place. This apparently caused a “Catch 22” situation and
the charts were not officially corrected until May 21st 2013 (Coast
Guard 5th district - Local Notice to Mariners – Week 21/13).
vessel survey data collected during the period of December 2012 and May 21st
2013 is inadequate because vessels with heights 67 feet or more were illegally
restricted from passing through Gallants Channel.
Navigation Survey Sample Period
The 5 month sample
period to be used by NCDOT for their report is still inadequate for a proper
order to make one small change to a bridge opening schedule, the Coast Guard
requires a detailed survey including 3 years of automotive traffic data.
The purpose of this requirement is to protect the current needs of navigation.
NCDOT is requesting to get a Coast Guard bridge permit for a fixed span bridge
which will change the vertical clearance from unlimited to 65 feet and will
permanently seal off a federal waterway for current and future maritime traffic.
This drastic change should at least have the same 3 year waterway survey
requirement as changing a single scheduled bridge opening.
times for tall masted vessels transiting Gallants Channel are spring, fall, and
right before named storm events, at minimum, a maritime survey should include
these sample periods.
Navigation Survey Data Flawed
The first survey
report from NCDOT goes into great detail on the methodology and high tech
equipment used to measure mast height. It all boils down to basic geometry. In
order to accurately measure the mast height above the water, they need two very
precise measurements, the angle from a fixed point to the top of the mast, and
the distance from this point to the mast.
Click here to see NCDOT survey report
The NCDOT Vessel
Height Survey Report states that the Horizontal Distance used in the calculation
was measured for each vessel that required a bridge opening. This is not true.
talked to the engineer taking the samples and was told that
they chose a fixed horizontal distance measured to the middle of the channel. I
verified this with Kristine O’Connor, Project Manager for the Gallants Channel
Bridge project. She stated that the horizontal distance could not be measured so
they picked a point to the center of the railway piers.
Click Here to see email from Project Manager
By using a fixed horizontal distance in
the calculation, NCDOT is making an erroneous assumption that the mast of the
vessel being measured is always in the center of the channel. Using a GIS map, I
measured the distance between the railway piers as roughly 82 feet, so the
midpoint would be 41 feet. It is not a reasonable assumption that a vessel’s mast
would always be at the midpoint of the channel. Considering 2 way
traffic and the fact that the channel does a dog-leg left at this point, it is
conceivable that a vessel’s position would be off the midpoint of the channel by
as much as +-20 feet or even +-25 feet. Using
NCDOT’s own calculations and varying the horizontal distance by 10, 20 and 25
feet you get substantial vessel height differences:
At an offset of +- 10 feet there is a
difference of over +-2 feet in Vessel Elevation
At an offset of +- 20 feet there is a
difference of over +-4 feet in Vessel Elevation
At an offset of +- 25 feet there is a
difference of over +-5 feet in Vessel Elevation.
A good example of the probable error is
SV Sans-Souci that transited Gallants Channel on November 13th 2012. NCDOT calculated the mast
height at 64.8 feet and did not include it in their list of vessels that could
not get under a 65 foot fixed span bridge. If this vessel was just 2 feet right
of the center the calculated height jumps to 65.2 feet. There is no way to
verify it because NCDOT did not include the owners name and contact information
as required by the Coast Guard for vessel survey data.
For a more glaring example of the
flawed method that NCDOT used to measure vertical vessel heights – just look at
the NCDOT sample data for the Crystal Coast Lady
in their first
report. The Crystal
Coast Lady was measured 28 times during NCDOT’s
August 2012 sample period, the vertical heights reported using NCDOT’s
measurements and calculation ranged from 29.23 feet to 45.81 feet
– a variation of 16.58
It appears that the method used by NCDOT
to measure mast height is not valid. Without an accurate horizontal distance
measurement the data obtained from the calculation is meaningless.
Navigation Survey Does not meet USCG
Navigational Evaluation Requirements
The data vessel
survey data collected by NCDOT does not appear to meet the requirements for
Navigational Evaluation put forth by the USCG BRIDGE PROGRAM REASONABLE NEEDS OF
NAVIGATION WHITE PAPER Version 1.1, October 5, 2012. Specifically, the NCDOT
Survey does not comply with most of the requirements of the section defining
Navigational Evaluations.Click Here to See USCG White Paper
In conclusion: This vessel survey being hastily done by NCDOT is a last minute
attempt to change the prevailing decision of the Coast Guard on the bridge
height requirements. The Coast Guard gave NCDOT a preliminary decision of 77
feet in May of 2012, based on over 4 years of investigation and data collection.
The data currently being compiled by NCDOT was taken with illegal height
restrictions imposed on Gallants Channel, an inadequate sample period, a flawed
method to determine mast height, and the data not meet the Coast Guard
requirements for a Navigational Survey.
Gallants Channel Coalition