The main tunnel used to access the base of the Verdon Gorge from the parking at Couloir Sampson (Sentier Martel) is closed for restoration work. The dates given for the work are 5 September to 31 December. French news report is here.
This affects the approach to the full-height routes like Voie ULA and La demande described on pages 246 and 247 of the guidebook. These routes could still be accessed by abseil from above but then you need to be sure you can climb back out since retreat would be awkward without the tunnels to walk out.
Alan Carne comments on the UKC Forum thread here:
“You will be able to access from the right bank of the Verdon via the ‘Pont de Tusset’ and the path that leads behind the ‘Duc’ (about 1.30hr uphill walk) but will not be able to park on the road that leads down to ‘Couloir Samson’. The ‘Sentier Martel’ access at Couloir Samson and the tunnels will be closed.”
The news also states that the tunnels will be opened again in January but the plan is to close them next September (2012) although this appears to be the middle tunnel which isn’t used much by climbers.