The South Forty-Foot Drain, also known as the Black Sluice Navigation, is the main channel for the land-drainage of the Black Sluice Level in the Lincolnshire Fens. It lies in eastern England between Guthram Gowt and the Black Sluice pumping station on The Haven, at Boston. The Drain has its origins in the 1630s, when the first scheme to make the Fen land available for agriculture was carried out by the Earl of Lindsey, and has been steadily improved since then. Water drained from the land entered The Haven by gravity at certain states of the tide until 1946, when the Black Sluice pumping station was commissioned. The Drain was navigable until 1971, when improvements to the pumping station led to the entrance lock being removed. It is currently being upgraded to navigable status by the Environment Agency, as part of the Fens Waterways Link, with a new entrance lock being completed in December 2008, giving access to the first of the drain, and the upgrading of the southern section, including a link to the River Glen to allow navigation to Spalding forming phase 2 of the project. History The Lincolnshire Fens are an area of low-lying land which have been subject to flooding and attempts to prevent it for centuries. In medieval times, the Midfen Dyke was built to drain the area, but by 1500, this was regarded less as a drain for the land than as a boundary marker between the Parts of Holland and the Parts of Kesteven, two of the three medieval subdivisions of Lincolnshire which functioned as county councils until their abolition in 1974. The first serious attempt to drain the area to the south west of Boston, now known as the Black Sluice Area but formerly known as the Lindsey Level, was from 1635 to 1638, when the Earl of Lindsey agreed with the Commissioners of Sewers for Lincolnshire to carry out drainage works which would make of land available for agricultural use. The Earl and a group of Adventurers paid for the works, in return for land grants. The cost of the work was £45,000, and involved the construction of a sluice near Boston, called Skirbeck Sluice, the construction of the first of the South Forty-Foot Drain, from Boston to Great Hale, the construction of two drains from there to Guthram, which were called the Double Twelves, and the construction of the Clay