Geology Site Account

Summary

Historical site only. Site of the Harwich borehole which, in 1857, was the first borehole to reach the 'basement of Essex', the hard Palaeozoic rocks that underlie the whole of the county, over 300 metres below the surface.

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Site description

The Tendring Hundred Water Company was established in 1884 but the companys origins can be traced back further to the town of Harwich where the lack of good drinking water had long been a complaint among residents. Several attempts had been made to find water but none had been successful including two boreholes that were carried down into the Chalk, one of which was recorded to be almost 300 feet deep.

Undeterred by this failure the sinking of an ambitious new borehole was commenced in 1854. Two years later the Harwich borehole had penetrated deep into the Chalk but had still not encountered a satisfactory supply of water and the decision was made to continue through the Chalk to the strata below. In November 1857, three years after the work had commenced, the borehole had been carried through the Chalk, the Upper Greensand and the Gault into the hard, slate-like basement rocks of Essex.

Although no satisfactory water supply was obtained from this borehole, and it was to be several more years before a good supply was found for the town, the borehole had reached a depth of over 300 metres (1,000 feet) and proved to be of great value to science. The hard basement rocks of Essex “ dating from the Silurian period and about 420 million years old - had been revealed for the first time.

The site was by the harbour, near the pier, just west of the former Great Eastern Hotel.

The geological succession (drawn to scale) encountered in the Harwich borehole. The depth (in metres) below ground level is shown. Illustration © Essex Rock and Mineral Society.