City Mill River - City Mill Lock

City Mill Lock

City Mill Lock, which connects Bow Back River and the bottom of the City Mill River to the Waterworks River, was built as part of the 1930s improvement programme. Unlike Carpenter's Lock, which was built at the same time and was fitted with vertical radial gates, City Mill Lock was built with conventional mitre gates. Two pairs of gates pointing to the west, allowing the lock to be used when the level of the water in the Waterworks River was lower than that in the City Mill River, and a third pair pointing to the east, which prevented high tide levels in the Waterworks River forcing the gates open, and the City Mill River draining as the tide fell. The lock was 20 feet (6.1 m) wide, and could handle boats up to 87 feet (27 m) long. The original gates lasted for almost seventy years, but by 2000 were deemed to be unsafe, and were replaced by stop planks.

In 2005, the lock was partially restored as part of the planning gain required from the developers of the adjacent Bellamy Homes housing scheme. Three sets of new steel gates, manufactured in Sheffield by Mandall Engineering, were installed at a cost of £200,000, and a further £100,000 was spent on general improvements to the area and the access paths to the lock. This left the lock in good condition, but not operational, since the gates did not have balance beams, and the hydraulic operating mechanism was not included in the work. Funding for the provision of the equipment came from the development of the area for the 2012 Olympic Games. Another £200,000 wes spent on the hydraulic rams, sluices, and the associated controls, and on lock ladders and landing stages to enable the lock to be used safely by boaters. The work was completed in 2010, and the lock was formally opened on 31 July.

The work involved dealing with large amounts of plant growth, particularly water pennywort, Hydrocotyle ranunculoides, a member of the apiaceae family, which were treated with herbicides to remove them. Water pennywort is a non-native invasive species, which quickly forms a dense mat of vegetation on the surface of slow-moving water, preventing the growth of other species and the movement of animals and boats.