Contractors in St Albans are to protect ancient Roman ruins by replacing gas mains by hand, despite increases in cost on the project.
New polyethylene (plastic) pipes are to be inserted into existing metal ones during work to replace 1.5km of gas mains in and around Verulamium Park, St Albans, which is standard practice for National Grid as the method reduces disruption.
However, Verulamium Park houses Roman remains including walls, the outline of part of a basilica and a hypocaust (heated floor), complete with a mosaic. Many important artefacts are known to lie in the soil surrounding the existing metal gas pipes but their exact whereabouts are unknown, as the pipes were installed in the 1950s when archaeological discoveries were inadequately recorded.
To avoid unnecessary damage, excavation work within parts of the park will be done by hand with archaeologists overseeing the work. It will be carried out by National Grid with its partners Triio, a joint venture between Skanska and Morrison Utility Services.
“It’s unusual to hand dig a scheme of this scale, and it’s precisely because of the importance [of the site] that we are using that oldest of special machines, the hand,” said Amec Foster Wheeler historic environment senior consultant Rachael Townend.
“There’s nothing more sensitive, and there’s nothing more flexible, than the human hand.”
Usually the work would be done by teams of two or three people, but in this case teams of around six could be used. Increases in time and cost on the project will be the main challenges but reducing damage risk is a priority.
“We’re very conscious that we’ll be working on some very historic ground,” said National Grid project engineer Dilbir Chana.
“Our project team is working very closely with Historic England and archaeologists to ensure that our work doesn’t adversely impact the area in any way.”
Work outside the park will continue as normal with machines used to dig through tarmac and concrete.
Replacement work starts Monday 13 March and is expected to continue for 12 weeks.