Key phrase is "some will be unable" which infers that some will be able to transit. However I don't know how many "some" is nor do I know how many ULCC's there are or how many there are relative to other tankers
I like the EIA as a petroleum information source.
But without dimensions to reference, I have doubts about those very general statements.
Cheers.
Can you find a tanker with 100,000 DWT or larger with a draft at 15.2 or less meters?
It seems they are all in the +20 meter range.
As for ULCC, there are not very many in the world. None of them will fit through the new Panama Locks.
http://www.aukevisser.nl/supertankers/id364.htm
On the list above of the world’s supertankers, including those now out of service, the smallest is the S.R Long Beach at 214,862 dwt. It had a draft of 19.7 meters.
http://vessel-ship.findthedata.org/l/35222/S-r-Long-Beach
I found the Prince William Sound with one of the shallowest drafts of 16.8 meters for 125,925 dwt.
http://vessel-ship.findthedata.org/l/25517/Prince-William-Sound
Can you find any supertanker, or any tanker of at least 100,000 dwt, that has a draft at 15.2 m or less?
http://vessel-ship.findthedata.org/