The Hemel Hempstead sinkhole that appeared on Saturday morning may have been caused by building homes on the site of a former brickworks, it has been suggested.
This website has been sent images that show what the area looked like in 1878, when it was occupied by an old brickworks. The brickworks had fallen into disuse by 1924.
Houses were built there between 1964 and 1970 as homes were added to the ‘new town’ of Hemel Hempstead. They were later demolished and replaced by houses that were built after 1996.
Old maps show that clay pits used by the brickworks were in a similar area to where the sinkhole is now.
George Storrow, 73, of Beaconsfield Road, Hemel Hempstead, said: “I would guess that in the 1960s the pits were not filled in properly with soil and compressed down. Water could have seeped in and washed the uncompressed soil away.”
He said new homes could have been built directly on top of the former clay pits, while it was only the gardens of the 1960s homes that were in that area.
Don Chisholm, who used to run chalk mines in Pinner, has a different theory.
He said: “Where there’s a brickworks, there’s chalk mines and chalk mines do not like getting wet.”
He said in the past chalk was often extracted at sites owned by brickworks to form a material called lime, which is used to make cement.
He said: “Chalk will dissolve when it rains.” This may have caused the area above the sinkhole to fall into what was a former chalk mine, he added.
They were only discovered after a huge sinkhole appeared in the garden of a Highbarns house.
The Nash Mills mines are thought to have been dug in the 19th century to produce chalk for papermaking at John Dickinson.