Excavation works are to resume on Tavistock Road today, following a further multi-agency meeting yesterday (Tuesday 17 January).
A detailed plan has been agreed by all agencies involved, including ordnance specialists, with contingencies in place for managing the safe search, extraction and removal of any further similar devices located on site.
It is anticipated that no further road closures will be necessary for this work to take place, but public safety will remain our number one priority at all times.
It must be stressed that risks remain low and we have measures in place to ensure the safety of road users, nearby businesses and workers on site.
We appreciate the public’s patience while we consulted with experts and sought a safe and practical solution.
Anthony Payne, Strategic Director for Place, Plymouth City Council
Chief Superintendent Andy Boulting, Plymouth Commander, Devon and Cornwall Police
Frequently asked questions
Why are you carrying out excavation work on Tavistock Road?
The Council is widening the road to create extra traffic lanes and reduce congestion as part of the Derriford Transport Scheme. It needs to excavate the central reserve to create the extra space needed for these additional lanes.
What are the devices that have been found?
They are called N0.76 self-igniting phosphorous (SIP) grenades. They are not, as their name might suggest, explosive devices but glass jars with a combustible compound.
Items of unexploded ordnance (UXO) are not uncommon in cities that have been subjected to aerial bombardment and military occupation but items such as these are difficult to detect using standard survey techniques.
How dangerous are they?
All items of ordnance can pose a danger if not handled correctly. As with most items of UXO it is highly unlikely they would spontaneously ignite or detonate if left alone. With this particular device, the glass jar would need to be broken to expose the contents to air, resulting in spontaneous combustion.
What happens if one ‘goes off’?
Any devices that remain on site are currently buried within wet mud so this is considered very unlikely. Any that are uncovered as part of the search will be very carefully extracted and removed from the site under specialist supervision. In the very unlikely event of one breaking and combusting it would expel smoke (and possibly some flame).
What would happen to the traffic?
The smoke (and possible flame) would be largely confined to the fenced off excavation area and dealt with quickly by on-site staff. It would pose a very low risk to passing vehicles but if there were any public safety concerns a cordon would be set up.
How long will this process take?
We expect to complete search and removal in the area where the SIPs were found within a week. We will then begin a search of the wider area.
How many devices are thought to be buried at the site?
It is not yet known whether this is limited to two individual finds separated by a few metres or part of a wider cache of abandoned and buried UXO.