the Mendips have produced contamination of the water emerging from the caverns at Wookey Hole. The lead in the water is believed to have affected the quality of the paper produced. The designation of the water catchment area for Wookey Hole, covering a large area of the Mendip Hills as far away as Priddy Pools, as a Site of Special Scientific Interest (SSSI) during the 1970s and 1980s was controversial because of conflicts of interest between land owners, recreational cavers and cave scientists. Initial proposals put forward by the Council of Southern Caving Clubs (part of the British Caving Association) were that SSSI designation, which would restrict what farmers and other landowners were allowed to do, would cover the entire catchment area. This was opposed as being too restrictive and difficult to enforce. It was argued that agricultural use of fields not directly in contact with cave entrances would have little detrimental effect on the caves themselves. There was also debate about which caves and cave features should be considered "important". The final settlement resulted in a smaller area being designated and many agricultural practices being removed from the list of proscribed "Potentially Damaging Operations". The entrance weir and sluice gate servicing the paper mill was built about 1852. The tunnel excavated from the third chamber to the ninth chamber and then out to daylight was dug in 1974–1975 by ex-coal miners from the Radstock area. The show cave was further extended in 2015 by excavating a tunnel from the ninth chamber to the 20th chamber. The constant temperature of in the caves is used by Ford Farm of Dorset to mature Cheddar cheese in the 'Cheese Tunnel' – an excavated side tunnel between the ninth chamber and the exit to the show cave. Cave archaeology Archaeological investigations were undertaken from 1859 to 1874 by William Boyd Dawkins, who moved to Somerset to study classics with the vicar of Wookey. On hearing of the discovery of bones by local workmen, he led excavations in the area of the hyena den. His work led to the discovery of the first evidence for the use by Paleolithic humans in the caves of the Mendip Hills. Middle Paleolithic tools have been found in association with butchered bones with a radiocarbon age of around 41,000 years. Herbert E. Balch continued the work from 1904 to 1914, when he led excavations of the entrance passage