Strood & Higham Railway Tunnels, Kent were originally constructed 1818-1825 by French POWs as part of the Thames Medway Canal, and converted to rail use in the mid-19th century. About 60% of the 3,483 m overall length of the two tunnels, which are closely abutting via a small crater-like depression known locally as the 'bomb-hole', is lined, mostly with the original brick lining. There are also some short sections, which have been lined since the original tunnel construction, using a variety of lining methods. The remaining 1,405 m is unlined over 16 sections of tunnel varying in length from 2.5 m to 256 m. A detailed survey carried out in February 2001 showed that the tunnel cross section varies considerably along the unlined sections, in width from 7.2 m to 9.6 m, and in height from 5.9 m to 6.9 m.The tunnels are in the Upper Chalk, and numerous chalk falls have been recorded since 1957. A fall in December 1999 struck and derailed a train. As a result, a 60 m section of tunnel at the fall location was lined in April, 2000, using a structural reinforced shotcrete lining. Shortly after the tunnel was reopened, another fall occurred close to the repaired section. A further fall occurred on 13th April, 2001 while a borehole was being cored in the chalk as part of a site investigation. The normal line speed on this section of the third rail electric route is 70 mph, but there is currently a speed limit of 20 mph.Design and Construct Contract awarded by Railtrack to Amco/Costain JV with specialist consultants London Bridge Associates. Anticipated closure period 20 to 30 weeks, total construction 70 weeks. Total cost estimate €25 million. Visit www.amco-construction.co.uk 34/02.