What Lies Beneath: A sinkhole story
The story of the sinkhole repair and reinstatement on the A413 adjacent to Deep Mill Diner/ Bubbles Car Wash, Little Kingshill, Great Missenden - July 2025.
Chapter one
On Tuesday 1 July, our Buckinghamshire Highways team received an out of hours emergency call regarding a hole that had appeared on the A413 outside of Bubbles Car Wash. This was a large hole, that was potentially very dangerous for drivers on this fast and busy road.
The person who called in the emergency was actually a senior officer from Buckinghamshire Council who was travelling by bike. Having reported the hole to the team, they stayed on site until both the police and our crews arrived to assess the situation.
Photos of the hole discovered on A413, outside Bubbles Car Wash
That evening, and through to the next day, detailed investigations were carried out, with the road and our crews protected by a lane closure using two-way traffic lights. This included the use of ground penetrating radar and CCTV. It appeared the sinkhole had been caused by localised water ingress (the unwanted presence of water in openings or structures). However, whilst investigating the sinkhole, we found what we believed to be an old defunct drainage channel almost 2m under the road surface, running across the A413.
Old defunct drainage channel almost 2m under the road surface, A413
As always, we worked hard to understand the problem and to share as much information as possible with road users via One.Network. We also provided timely updates via our dedicated social media channels: Facebook - @BuckinghamshireHighways and X - @Bucks_Highways
Screenshots of Buckinghamshire Highways Facebook posts on the A413 sinkhole
Chapter two
Following the discovery of the old defunct drainage channel, we liaised with the council’s archaeology officer who attended site to record and map the feature as part of the Historic Environment Record database – an organised collection of information about a specific geographic area's historic environment. It was clear that the channel pre-dated the road and perhaps was associated with the formation of the turnpike road in the 18th Century.
We did not consider there to be any immediate safety issues concerning the depth of the feature found. It was however important that this was addressed to preserve the future structural integrity of the A-road, so works were planned with immediate effect.
Early on Saturday 5 July we closed the A413 to carry out a full repair of the sink hole and reinstate the old drainage channel. This required excavating down to 2.2m across the extent of the carriageway, filling in the old drainage channel and reinstating the road surface. We also worked closely with utility companies already operating nearby to coordinate efforts and minimise disruption and liaised with HS2Ltd/Align on the emergency works recognising that this is a key construction route.
On Monday 06 July the road was re-opened by 6am in time for the morning rush-hour traffic.
Photos of the emergency roadworks taking place and completed on the A413
Chapter three
Less than two-weeks after the works to repair the sinkhole, the A413 was closed again near the Deep Mill Diner and Great Missenden Pumping Station (approx. 500ft along the road from Bubbles Car Wash) by the utility company, Affinity Water. This was to allow Affinity Water to investigate multiple burst water mains outside the pumping station, resulting in flooding of the road and significant damage to the surface of the carriageway making it unsafe for road users. It was estimated that the road needed to remain closed for up to 10 days (until Sunday 27 July) to enable Affinity Water to fix their pipes and then repair the road structure and surface.
This presented a collaboration opportunity for Buckinghamshire Highways and allowed us to action a lot of our own maintenance works under Affinity Water’s emergency closure. Whilst the road was closed for the sinkhole, Buckinghamshire Highways took the opportunity to carry out some much-needed large area patching work in the area. We carried out two patches of approximately 50 square metres (that's roughly the same size as 16 and a half UK King-size beds!) along the Amersham side of the closure. The council’s Street Scene team also cleared kerbside debris and litter from the verges along the Great Missenden side of the closure, negating further disruption to road users at a future date.
The repair works carried out by Affinity Water were completed earlier than anticipated on the 24 July - including the resurfacing of a large section of the carriageway on the A413.
Affinity Water flooding of A413 (left) and large area patching work carried out by Buckinghamshire Highways on A413 (right)
Report a problem on the pavement or road surface
You can report a problem on the pavement or road surface by using FixMyStreet. Alternatively, please call us to report flooding or a problem on roads and pavements that you feel is unsafe and needs to be dealt with as an emergency:
In office hours: 01296 382416
Out of hours: 01296 486630