[abstract] DIGGIN' DEEPER - COMPRESSED AIR WORK BEYOND 30 METERS.

Abstract

For the first time in the development of this century's caisson activities in Germany, the legal pressure limit of 30 meters equivalent water depth had to be overruled to allow the driving of a tunnel under the Baltic Sea in the State Capital of Kiel last year. It serves for a piped heat supply network and connects the two sides of a fjord approx. 1350 m apart. Due to ground conditions a maximum depth of 38 meters had to be planned for. The initially intended application of the Canadian DCIEM tables (for O2-in-water-decompression of divers) very soon proved to be impracticable, offering just less than one hour of compressed air work per individual shift. In very close cooperation on site the legally responsible health authority, reacting to technical and human demands, gradually extended the isobaric exposure time, which finally ranged from 3 hours at 33 meters to 1.5 hours at 39 meters. Not a single incident of DCS occurred beyond the 30 meter pressure level. This table work will be presented for discussion, its rationale will be outlined. The extraordinary importance of "fringe factors" will be stressed, including the continuous medical coverage through the nearby Naval Medical Institute. More discussion and investigation is still needed before these figures can be introduced via legislation into the West-German statute book for unrestricted use.