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Hodbarrow Sea Defences
Duddon Sands, near Millom, Cumbria, UK
Hodbarrow Sea Defences
associated engineer
Sir John Coode
Coode, Son and Matthews
date  pre 1884, 1888-90, 27th April 1900 - April 1905
UK era  Victorian  |  category  Coast Protection  |  reference  SD173779
ICE reference number  HEW 968
photo  ICE R&D Fund
The sea barriers at Hodbarrow are part sea defence and part earth dam. They were built in three phases and are designed to prevent the inflow of sea onto land that is prone to subsidence by the underground mining of haematite ore.
The coastal haematite ore workings were leased to the Hodbarrow Mining Company Ltd. by the Earl of Lonsdale in 1855, after the discovery of an 18m thick iron ore deposit at a depth of 24m. From 1873 the ore was extensively worked, and its extraction caused subsidence to the coastal land above.
The first phase of defence work, of unknown start date, comprised 152mm thick timber sheet piles driven to a depth of 2m, with 300mm square timber king piles driven to a depth of 6m. These were tied back by iron rods to other piles 18m behind the line of the main defences. This first stage was breached in 1884, following subsidence.
The second phase took place between 1888 and 1890, in the shape of a concrete wall, designed by Sir John Coode. This Inner Barrier was backed by a clay embankment and made watertight with puddled clay placed immediately behind the concrete. This wall was affected by subsidence, when the central section of the wall collapsed. The large breach that occured then remains in place today.
The Outer Barrier is the third and final phase of defences. This wall was constructed under the direction of Messrs. Coode, Son and Matthews, and designed to protect some 69 hectares of land. The contract for the construction was let to John Aird & Co in 1889 and commenced on 27th April 1890. The defences are designed to be watertight and also flexible, to allow for potential further subsidence.
Appropriately, the dam engineer James Mansergh was drafted in to assist the operation, for the Outer Barrier defences effectively functioned as a dam. They comprise an outer slope of limestone and an inner slope of slag. Between them, it was intended that a puddled clay cut-off would be formed with clay fill above. This was abandoned in favour of steel sheet piles, 9m long, driven with the assistance of water jetting in certain places.
When completed, the Outer Barrier is made up of a curved wall over 2km long, 12m high, with a maximum crest width of 25m, and a maximum width at its base of 64m. The seaward 1 in 1.5 slope is of 25 tonne concrete armour blocks on some 475,000 cubic metres of limestone rubble. The landward 1 in 1 slope comprised 26,000 cubic metres of slag, substituted by 415,000 cubic metres of clay fill and 61,000 cubic metres of concrete during construction. The practical completion certificate of this stage is dated 1 October 1904, and the last stone was laid on 13 April 1905.
Mining ceased at Hodbarrow in 1968. The Outer Barrier now encloses a large lake with the boats of the Port Haverigg Holiday Village in the northwest, and the Hodbarrow Lake Nature Reserve within the remains of the Inner Barrier in the northeast. The Outer Barrier has a central lighthouse (SD174779). There is also a former lighthouse on land (SD180783) and the remains of a windmill (SD182782) by a disused quarry at Hodbarrow Point.
Contractor: Lucas and Aird (Inner Barrier)
John Aird & Co (Outer Barrier)
Research: PD
"Industrial Archaeology in the Lake Counties" by J.D. Marshall and M. Davies-Shiel, David & Charles, Newton Abbot, 1969
Engineering, 7th April 1905
reference sources   CEH North

Hodbarrow Sea Defences