Stoppage/Slowdown Codes
A stoppage is when navigation would be halted whether or not there are vessels to serve. A stoppage must be either scheduled or unscheduled. Scheduled stoppages are announced via Navigation Notices (via mail, email, web posting), Broadcasts to Mariners etc.Unscheduled stoppages are events that force navigation to cease and are not planned. A slowdown/stall is when navigation is only slowed but continues. The Stoppage/Slowdown Codes are used to indicate the reason why the stoppage/slowdown occurred. Stoppage/Slowdown Event Codes - associated with a stoppage indicates where the stoppage occurred prior to what event during lockage.
Code	Description
A	A - Weather - fog
B	B - Weather - rain
C	C - Weather - sleet or hail
D	D - Weather - snow
E	E - Weather - wind
F	F - Weather - lightning
G	G - Surface - low water
H	H - Surface - ice on or around tow
I	I - Surface - river current or outdraft
J	J - Surface - flood
O	O - Surface - debris
N	N - Surface - operations (run-spill-divert water; flush seals-reserve, etc)
K	K - Tow - interference by other vessel(s)
L	L - Tow - tow malfunction or breakdown
M	M - Tow - tow staff occupied with other duties
P	P - Tow - tow accident or collision
Q	Q - Lock - debris in lock recess or lock chamber
U	U - Lock - ice on lock or lock equipment
R	R - Lock - lock hardware or equipment malfunction
S	S - Lock - lock staff occupied with other duties
T	T - Lock - maintaining lock or lock equipment
Y	Y - Lock - inspection or testing lock
AA	AA - Lock - accident or collision in lock
BB	BB - Lock - closed (unmanned shift)
EE	EE - Lock - repair lock or lock hardware
V	V - Other - tow detained by Corps or Coast Guard
W	W - Other - collision or accident (not tow or not in lock; see P, AA)
X	X - Other - bridge or other structure (railway or vehicular bridge)
CC	CC - Other - grounding
DD	DD - Other - environmental conditions (fish, animals, oil spills, hydrilla etc.)
FF	FF – Other – lock okay; unused for other reason (CG river closing etc)
Z	Z - Other (Remarks)