Only in Cologne by Duncan J.D. Smith

117 Innenstadt generation plant in action visit the Heizkraftwerk Merkenich at Mer­ kenicher Hauptstrasse 2, where tours are again available courtesy of RheinEnergie AG. The tunnel beneath the Rhine was excavated between 1983 and 1985, at a depth of six metres beneath the surface of the riverbed. Its successful construction through loose river gravel was considered a bold engineering effort at the time, necessitating the boring of the tun- nel and then the insertion of a series of concrete rings thirty centime- tres thick, each inserted from the Deutz side using hydraulic rams. Dur- ing the operation some interesting artefacts were unearthed, including fragments of Second World War bombs and pieces of steel from the original Hohenzollern Bridge (Hohenzollernbrücke), blown up delib- erately by German engineers in March 1945. Those walking through the tunnel, which is only three metres in diameter and therefore some- what claustrophobic, will emerge eventually on the west bank of the Rhine at Breslauer Platz. The history of Cologne’s public power and heating supply is in- extricably tied up with that of its public water supply. The city’s first waterworks were established in 1872, followed a year later by the city’s purchase of the Imperial Continental Gas Association, a private Eng- lish company responsible for gas supply and street lighting in Cologne since 1841. The first public electricity supply was inaugurated in 1891 on Zugweg (Altstadt-Süd), and was the first power station in Germany to generate an alternating current. The waterworks were relocated to the same site around the same time (see no. 39). Supply continued una- Cologne’s District Heating Tunnel (Fernwärmetunnel) beneath the Rhine