15-ton F-14 TOMCAT from 1,900-ft water depth 100 miles off Scotland in 
1976 reportedly required about two months, involved seven vessels and 
cost about $2 million (Ref 3). 
Another potential application of hardening is the stabilization of 
ocean cables and pipelines on firm seafloors in deep water. The purpose 
is to prevent accidental damage which is caused mostly by trawlers and, 
importantly, to preclude purposeful damage. At the present time, cables 
and pipes are protected by burial in those seabottoms soft enough to be 
trenched. In bottoms not suitable for trenching other protective methods 
are needed. In some cases, pre-cast concrete covers have been placed 
over seafloor cables to stabilize them on a firm bottom (Ref 4). A 
study is currently underway in Norway on in situ concreting of underwater 
pipelines (Ref 5). 
Containment of Hazardous Substances 
Another potential application of placing concrete on the seafloor 
is to cover or contain hazardous substances for the purpose of isolating 
them from the environment. Again, this is an alternative to recovery. 
A hazardous material incident could involve radioactive materials from a 
nuclear power source or weapon system. Another example is containment 
of hazardous materials dumped in the ocean in the past and presenting a 
potential problem in the present. Biochemical agents have been dumped 
off the U.S. East Coast and radioactive wastes from earlier military and 
Civilian developments have been placed on the seafloor in the Pacific 
Ocean near San Francisco and the Atlantic Ocean off Maryland. Leakage 
problems if they arose could be resolved in many instances by encasement 
in concrete. 
BACKGROUND 
Prior Work 
The Civil Engineering Laboratory conducted a literature survey in 
1966 on state-of-the-art methods of subaqueous concrete placement. The 
report concluded that, for general use, the most practical methods to 
consider for adaptation to placing concrete in forms in the deep ocean 
were the pumping method and the preplaced aggregate method; bucket 
placement would be practical for small quantities. Also a concept was 
proposed adapting an existing cargo-type submarine for use as an under- 
water concreting plant. The submarine has the advantage of avoiding the 
air/sea interface motion problems and could be used covertly. It would 
be limited by size and strength of the pressure hull to placing small 
quantities of concrete at depths less than about 1,000 feet, unless an 
expensive special hull were built (Ref 6). 
