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Civil Engineering heritage: Scotland - Lowlands and Borders
Date 2007
Event ID 590348
Category Descriptive Accounts
Type Publication Account
Permalink http://canmore.org.uk/event/590348
Glencorse Dam retains the 50-acre Glencorse Reservoir which forms part of the water supply system to Edinburgh. It is located in the Pentland Hills about six miles south-west of the city and was built between 1820–24 to provide compensation water to mill owners for the water taken from Crawley Spring and Glencorse Burn to supply the city. The project was designed by Jardine, the Water Company’s engineer, with Telford acting as consulting engineer for the Company’s interest and Rennie for the mill owners.The earth dam, when built one of the tallest in Britain, is 330 ft long, 450 ft thick at the base, and about 110 ft high measured from rock level in the bottom of the cut-off trench some 50 ft below the bed of the burn. The illustration is based on Jardine’s 1819 specification before work started. There is an oval-section ashlar masonry tunnel carried through the embankment with cast-iron valve-work under a shaft to the top of the dam. Reaching an impervious bottom for the clay puddle cut-off wall proved a great problem which nearly resulted in abandonment of the dam; 10 000 cu yards of puddle clay being required to effect a seal. Crawley Cistern, a distinctive masonry building 60 ft long with a stone-slab roof surmounting a semicircular vault springing from 3 ft above floor level containing the 45ft by 15 ft open-topped masonry cistern, was designed by W. H. Playfair under Jardine’s direction. The tank is at the head of a nine-mile cast-iron aqueduct, with a maximum diameter of 20 inches, passing via Liberton and under Castle Hill to Hanover Street in the New Town on a plinth in a 6 ft by 5 ft wide tunnel.
The pipes were supplied by the Butterley Company and each was proved by subjecting it to a pressure equal to that of a column of water from 300 to 800 ft high. The whole works cost £145 000 and were dubbed by The Scotsman in 1825, ‘the most extensive, perfect and complete ever executed in modern times’.
R Paxton and S Shipway 2007
Reproduced from 'Civil Engineering heritage: Scotland - Lowlands and Borders' with kind permission of Thomas Telford Publishers.
