Sinkholes in a field are said to have formed as a result of tunnel boring for the HS2 train project.
Two additional holes were discovered on the borders of South Heath, near Great Missenden, Buckinghamshire, where the Chiltern Tunnel is under construction.
This implies that HS2 has generated four craters in the county in nine months.
HS2 Ltd. stated that “safety was its top priority” and that both sinkholes had been walled off while digging activities were underway.
The smaller of the two holes was discovered near Frith Hill during normal monitoring on February 7, and a larger feature was discovered in the same field five days later, according to the Local Democracy Reporting Service.
HS2 Ltd. said that no public right of way existed over the impacted site.
In May, a sinkhole of around 6m (20ft) in diameter and 5m (16ft) deep developed out in Shardeloes Lake near Little Missenden, followed by another in Hyde Heath in November.
Both were filled up and discovered to have no major effect on water quality.
According to HS2 Ltd., the latest sinkholes might be the result of digging disruptions and recent rains, which deteriorated pre-existing weak points.
“We have always recognised that the geology of this part of the route is particularly challenging, with poorer quality, less stable chalk susceptible to ground movement,” said a spokesperson for the company.
“Temporary fencing has been installed and extra monitoring put in place.”
The Chiltern Tunnel, which runs for 10 miles (16 kilometers), is the longest section of the HS2 project, which intends to enhance communications between London and Birmingham.
Buckinghamshire Council and the Environment Agency have been contacted for comments.