Request from a developer to investigate and survey workings uncovered during site development works.
On 11 May 2022 we were contacted via the KURG website enquiry page by a contractor preparing a site for construction near Maidstone. They requested that we might help in urgently investigating a ‘sinkhole’ which had been exposed by their ground works excavations.
John Smiles and Pete Burton attended the same day to investigate the site and advise the contractor on what they might need to deal with before continuing with their works.
The sinkhole was a small, domestic scale sand mine cut into the locally abundant fine-grained construction sand of the Folkestone Beds laid down in the Cretatious. At least two other underground sand mines are known to exist in the immediate area.
Following the usual safety checks, an approximate tape and compass and photographic survey was carried out. This survey was then supplied to the contractor, ready for referral onto their design team to advise what to do next to make this minor working safe for the access roads and light industrial units destined to be built on the site before the end of the year.
The likelihood is that the site will either be untopped – the tops of the chambers being no more than four metres beneath the current (recently modified) landform – and levelled with layers of compacted fill, or made good with foamed concrete or similar.
Whichever fate awaits this small mine will of course obliterate it, probably within a week or so.
History: The Crossness Pumping Station was built by Sir Joseph Bazalgette as part of Victorian London’s urgently needed main sewerage system. When the buildings were abandoned, the pumps and culverts below the Beam Engine House were filled with a weak sand and cement mix to reduce the risks from methane. We are helping the trust to remove some of this mix and explore some of the old tunnels. More information on the Crossness Pumping Station can be found on their website http://www.crossness.org.uk
19th August Work started on helping, the group who are engaged in the restoration of the engines, in removing sand from one of the cylinders and a tunnel.
14th October Work continued on digging out the tunnel, until the daily influx of water, and on the area below the piston. Digging was halted around lunch time to enable us to hold our AGM in the canteen.
14th October After lunch we concentrated on emptying the area inside the piston. 2 people inside the piston filling the buckets, 2 people man (and woman) handling them to the ground and then an electric winch to raise them to the surface, where we used wheelbarrows and a dumper truck to dispose of the spoil.
17th February Work continued inside digging in the area below the piston, The outlet valves can be clearly seen at the back and we are in the process of uncovering the inlet valves in the bottom of the chamber. It’s a good job that we have a fan to provide fresh air as it was getting a bit smelly at the bottom.
17th February Outside we are digging a hole which we hope will eventually lead through an arch and into the filth hoist chamber. Work is tough going even with a kango hammer as the infill here is much harder than inside.
17th February Having a dumper truck to take away all the spoil is very useful, even if we have to barrow it out to it.
17th March Work continued on emptying the area below the piston and we had just finished this when a break through was made in the hole outside. Lunch was temporarily put on hold and a ladder found to investigate.
17th March Descending down into the Filth Hoist Chamber we found that the infill had settled / washed away leaving ample room for us to enter and investigate. The photo on the left shows the Filth Hoist bearing whilst the photo on the right is looking out from the Filth Hoist chamber. The archway is under the main building foundations and the rusty metal on the left is the flywheel casing .
17th March Some of the digging crew.
14th April Although we expected to finish things off on the last visit we ran into some problems in our efforts to get to the base of the flywheel housing. As we lowered the level of the sand we opened up an easy route for the water in the outside access chamber to drain through into our workings. As a result we will have to shore up the excavation as we go.
14th April On inspection we discovered that the area between the flywheel casing and the flywheel is full of debris and we are investigating the best way to gain access into the space
26th May Due to the confined space we were working in and the dust & fumes a fresh air supply was necessary. This home built blower and helmet was more than up to the task.
26th May Outside work started on emptying the pit. Unfortunately the spoil below the sand was a rather unpleasant black tarry sludge that stuck to everything.
Although not recently discovered we went to have a look at 2 holes from the WW2 era in Hamstreet. The first hole had about a foot or more of water in it when we arrived but this was quickly pumped out to reveal a small concrete lined and concrete floored chamber about 10ft deep
Access was by foot rings in the sides and the floor would have originally been wooden boarding
The only thing of interest in this hole was some graffiti possibly dating back to it’s early days
The second hole, smaller in diameter produced little of interest after a couple of hours digging and has been abandoned. This is possibly an escape route from a WW2 post but the original entrance has been lost over time.
25th November Work started on a dig near Ranscombe in Kent. On initial inspection the feature consisted of a round hole about 3½ feet in diameter about 2 feet deep filled with logs. After several dozen logs were removed work started in ernest to dig out the hole. Previous experience suggested it would be a collapsed dene hole. However as we began to increase the depth, evidence of other possibilities came to light.
The shaft appears to be flint lined suggesting the possibility that is not a dene hole but a well instead. By the end of the day we had managed to excavate about 20 feet and were now well into the chalk layer. Foot holds are clearly visible in the sides of the shaft and the flint lining above the chalk is clearly visible. More pictures can be found in the recent photos section.
16th December Work continued on the dig and grill has now been fitted to the hole. Although we removed another 10 feet of infill the purpose of the hole still remains a mystery. The composition of the infill seems to have changed very little, being very light and easy to remove and the shaft is still progressing down through the chalk layer.
31st December Work continued downward. Along with the infill some pottery remains and a large stone was recovered from the hole. Further investigation of the pottery found suggests it is associated with cooking or low status drinking type vessels. The piece with a rim was suggested as Romano British (3rd or 4th century) and the 5 other pieces of about same period to around Norman conquest, dating is imprecise on these pieces as there are no real distinguishing features. It would appear that pottery pieces above are from at least 3 different items which rather suggests more than just casual occupation in the area. There was also a hand made nail, 18th or very early 19th century and scrap of hand made salt glazed stoneware of probably 18th century.
20th January 2007 Work continued on the dig but nothing of huge interest was found. The hole is almost certainly a well, and having almost reached the end of the cable for our small winch the decision was taken not to proceed any further. Work was concluded, the site was tidied up and left safety gated
2nd April Rod, Harry, Hugh and Mike visited a house in Cliftonville where a hole had appeared in the back garden. There was a narrow trench some 10 feet long which slopes down to a arch cut in the chalk at the base of the chalk face at the end of the trench. This was about 10 feet below the surface of the ground. The slope was comprised of loose earth. They shifted some of the earth at the bottom but were unable to get into the chamber.
29th April. A KURG organised group arrived to have a dig in the trench. While the youthful team were, allegedly, kept out of the way digging into a not so exciting WW2 air raid shelter, the geriatric team made a breakthrough in the main trench after only an hour of digging. An extensive tunnel system was found stretching for some distance. At this stage the exact nature of the system is not understood but suggestions are that it was either dug as a folly or a practice tunnel during WW1.
This picture shows surveying in progress, to try and map the full extent of this underground system. Various inscriptions have been found with dates of 1917 & 1918, but apart from a a tin of Zog Paint Cleaner very few artifacts were found in the tunnel. The system was predominately clean and dry although evidence of some past water could be seen on the floor in places. There was also some evidence of candle (or similar) lighting on the walls and roof. The far end of the tunnel appeared to be backfilled from the surface in two places. For more pictures click here.
17th December Work started on this dig. An aerial cable was placed across the hole using the fence posts for support. A second lifting cable and ingenious pulley system was hung below this to enable the bucket to be raised and then moved sideways.
28th January After another early start 2 members who wont be named decided to take the exercise and walk the ‘short’ way across the fields to the dig. Unfortunately they took a wrong turning somewhere and ended up going completely the wrong way. They arrived about 1 hour after they left the car park. Progress was slow because the excessive amounts of wire in the hole and we even had to resort to using a car to pull it out. We didn’t get as much done as we would have liked to but we think we can now see the top of the chamber.
25th February Work continued and good progress was made despite the weather. We managed to remove lots of wire along with many old logs from the hole. At the end of the day the top of a small chamber was visible.
25th March Despite a promising start the top of the chamber visible last time has so far been a bit disappointing. Although just big enough to crawl into it seemed to be very small and almost entirely back filled. However after several hours of digging a small entrance was found about 120° from the small one. Clive was the first to enter and explore this, despite an initial concern about the quality of the air. The chamber turned out to be larger then expected and unusual in design as it turned through 90°. This chamber is about 20′ long by about 6′ wide with a height of about 10′. There is another small chamber off the back of this which looks as if it may connect to the small chamber first discovered. For more pictures click here.
15th July It was amazing to see just how much growth had taken part since we last visited. Nature seems extreamly keen on reclaiming the hole and the surrounding area. Despite further digging the only thing we found was a mouse in one of the holes made to probe for the third chamber. After some deliberation it was decided to persue the dig no further. The bats will have to make do with a single chamber. The picture shows the spoil heap from the dig. For more pictures click here.
22nd January 2012 After many years of being dry, work started to clear out the debris thrown into the well.
As the well is inside the cave we weren’t able to use our petrol winch but fortunately power was available so we could use the electric one instead.
During the day we managed to clear many buckets of chalk and soil thrown into the well along with several hundred coins thrown in over the years. After removing 5ft of spoil water is now visible and hopefully on the next visit we will be able to continue downwards and leave the well with water in the bottom.
6th May The Canterbury Bunker is an old underground Brigade Command Center that was decommissioned around 1945. The owner had previously found and opened up the west entrance with the help of KURG and this return visit was to explore the newly opened up east entrance. When the first entrance was opened up, the passage having been completely sealed for many years, was full of bad air from rotting wood and had to be well ventilated before exploring was possible. The air in the east passage was well ventilated before we entered and presented no problems
The west entrance, an opening near ground level, leads down a flight of 59 steps then along through an air lock. As can be seen in the diagrams to the right the tunnels were constructed using two methods and although all the tunnels using the arched RSJ and corrugated sheeting have survived virtually intact the tunnels using the pit prop method have collapsed and are totally inaccessible.
Hugh looking at the collapse in the east passage
The west passage was blocked after approximately 60’ where the arched roof stopped, but it was possible to enter the latrines on the right hand side after a little digging. The east entrance being slightly higher up has a flight of 66 steps down and can be entered to a length of 120‘. This is also blocked by a collapse where the arched roof stops. Half way along this passage a similar set of latrines can be entered on the left hand side and opposite this can be seen the collapsed passage connecting to the west entrance passage.
It was hoped it would be possible to enter the engine room beyond the end collapse but due to the fact there was a 12’ void above the collapse and the passages are dug in Thanet sand, its was decided this would be too dangerous, so no further exploration was possible.
16th June After many years of being sealed up the concrete lid was raised on the old Ice House at Lullingstone.
22nd June Digging then began to clear out all the rubble and return the Ice House to it’s original state so it can be used by the local bat population
Winching out the buckets
Looking down into the Ice House
June 29th Further digging took place and the level has now fallen significantly inside.
Fortunately the side entrance is well appointed and allows access without having to Descend / Ascend through the top.
Looking out of the side entrance
Nearly at the bottom !
June 29th More digging and hauling away of rubble.
After further digging the end is now in sight and will hopefully be reached during the next digging session.
The digging crew having a break
Looking down at the bottom
August 3rd After further digging during the intervening weeks, tonight we finished clearing all the remaining rubble from the Ice House.
The whole chamber is now clear. The bottom is clearly visible and the whole chamber is remarkably well intact. The chamber is approx 19′ deep with a further 4′ deep drain hole / soakaway in the bottom.
Looking into the drain hole
Installing the bat boxes.
Bat boxes have now been attached to the walls and all we can now do is wait and see if the bats will take up residence. During this visit we also had a look at the nearby bathhouse with a view to clearing the ivy off the outside and emptying the rubble out of it.
21st November Work started to look the the “bath house” although there are still conflicting ideas as to whether this is what it actually is. The pool itself was full of debris, probably from the crumbling walls and possibly a roof. There would appear to be a spring that feeds it, on the side furthest away from the river, with a constant source of fresh clean water.
Cleaning out the rubble
21st March 2010 Work continues on the “bath house”. Progress was hampered by the ability of the pump to keep up with the inflow of water. Initially this was thought to be entirely from the spring but further investigation revealed a link to the river. As fast as we were trying to empty it the river was refilling it. After digging an investigative hole and plugging the inflow we were able to drop the level significantly, especially with the aid if some manual bailing. Amongst the debris removed were some nice tiles, possibly from the bottom. Hopefully the next trip, when the river level is lower or we can use an additional pump, should see the task completed, and the bottom exposed.