Drilling for mustard gas

Today Gareth Hughes was asking about deep sea drilling off Wellington in Parliament. His concern was the risk of an oil spill, but there's a worse one: chemical weapons. According to Owen Wilkes' History of New Zealand Chemical Warfare 1845 - 1945 [PDF], New Zealand maintained a large stockpile of mustard gas during WWII, primarily in the form of 25-pounder gas shells. These were stored in Auckland, and in Wellington at the Belmont Magazines. At the end of the war, they were dumped:

In April 1946 the hulk Rosomund was towed out to the l00 fathom line in Hauraki Gulf by the tug Maui Pomare from Auckland and scuttled. It was carrying 200 tons of chemical shell

In October 1946 some 1500 tons of 25 pdr chemical shell and 20 tons of bombs221 were dumped off Wellington by the Marine Department steamer Matai (normally used for lighthouse replenishment etc).

The location for the latter dumping was described as lying 50 nautical miles off Pencarrow Light on a bearing of l34 degrees.222 Assuming this is correct then the munitions are at about 175 deg 40' E, 41 deg 55' S, or about 45 km SE of Palliser Head, and well to the east of Cook Strait. Water depths here are of the order of 2800 metres, well beyond trawling depth.

According to the coordinates in the invitation for bids, that area is bang in the middle of exploration block 12PEG2. I wonder if the bidders have been informed they'll be drilling into a chemical weapons dump?

And yes, this is a problem and a potential risk to human health:

At least 21 and possibly as many as 50 ships loaded with 303 000 munition tons of allied mustard and German nerve gas weapons were scuttled off the coasts of Norway, Sweden and Denmark at the end of World War 2. The Soviet Union also dumped something like 50 000 tons of chemical munitions into the Baltic after World War II. Most of this was in fairly deep water but some is in quite shallow water only a few miles off shore. The munitions have been corroding steadily since, and mustard gas has leaked from them, in the form of’a jelly like substance which lies around on the sea floor without mixing in the seawater. Danish and Swedish fishermen often find soap-like lumps of mustard gas jelly attached to trawl nets, and on occasion Danish fishermen have been badly burnt by handling such nets.

(There's an example of such an incident here)

With drilling, the problem is going to be contamination of drilling equipment, but its still a risk, and one bidders need to be aware of.