Street lights were provided in 1906. Acetylene was replaced in 1931 by coal gas produced in Bridgwater, as well as by the provision of an electricity supply. Around the 1860s, at the height of the iron and steel era, a pier and a deep-water dock were built, at Portishead, by the Bristol & Portishead Pier and Railway to accommodate the large ships that had difficulty in reaching Bristol Harbour. The Portishead power stations were coal-fed power stations built next to the dock. Construction work started on Portishead "A" power station in 1926. It began generating electricity in 1929 for the Bristol Corporation's Electricity Department. In 1951, Albright and Wilson built a chemical works on the opposite side of the dock from the power stations. The chemical works produced white phosphorus from phosphate rock imported, through the docks, into the UK. The onset of new generating capacity at Pembroke (oil-fired) and Didcot (coal-fired) in the mid-1970s brought about the closure of the older, less efficient "A" Station. The newer of the two power stations ("B" Station) was converted to burn oil when the Somerset coalfields closed. Industrial activities ceased in the dock with the closure of the power stations. The Port of Bristol Authority finally closed the dock in 1992, and it has now been developed into a marina and residential area. During the First World War hundreds of Somerset soldiers were killed, and war memorials were put up in most of the towns and villages; only a few villages escaped casualties. There were also casualties – though much fewer – during the Second World War, who were added to the memorials. The county was a base for troops preparing for the 1944 D-Day landings, and some Somerset hospitals still date partly from that time. The Royal Ordnance Factory ROF Bridgwater was constructed early in World War II for the Ministry of Supply. It was designed as an Explosive ROF, to produce RDX, which was then a new experimental high-explosive. It obtained water supplies from two sources via the Somerset Levels: the artificial Huntspill River which was dug during the construction of the factory and also from the King's Sedgemoor Drain, which was widened at the same time. The Taunton Stop Line was set up to resist a potential German invasion, and the remains of its pill boxes can still be seen, as well as others along the coast. A decoy town was constructed on Black Down, intended to represent the blazing lights of a town which had neglected to follow the black-out regulations.