In 1971 Santa Fe-Pomeroy performed a study for the Civil Engineering 
Laboratory of construction methods for large undersea structures. The 
emphasis was on documenting the then existing capability of the construc- 
tion industry to fabricate large concrete spheres and cylinders and to 
emplace them on the ocean floor. Potential technology for extending 
construction capability to 3,000 ft depths was also considered including 
in situ construction methods in which concrete is mixed on a surface 
vessel and transported to the seafloor by bucket and pipeline methods. 
For the complex type of structures studied prefabrication or modular 
construction with in situ grouting was considered most promising (Ref 
Do 
Recently, a study was performed by Halliburton Services for the 
Civil Engineering Laboratory on conceptual methods for placing concrete 
at deep water depths (Ref 8). Five concepts were presented. The present 
authors consider that one of the concepts, called "Pumped Tremie Method 
(Closed System)," has the potential of being a versatile system for 
placing concrete at shallow or deep depths with or without the use of 
forms. It is this concept which is reported herein after being advanced 
by studying the technical and operational aspects of the placement 
method. 
State-of-the-Art Methods 
A number of state-of-the-art methods exist for transporting concrete 
and similar materials by pipeline and for placing them underwater. 
These methods are discussed briefly. 
Tremie Method. The construction industry regularly places large 
quantities of concrete underwater by tremie methods at depths of tens of 
feet to one or two hundred feet in protected waters for bridge piers and 
other waterfront type structures (Ref 9). Concrete falls by gravity 
through open pipes and is placed in forms or confined spaces. Flow rate 
is controlled by depth of burial of the lower end of the tremie in the 
concrete. Good quality concrete is regularly produced using established 
mix designs and operating procedures. Maximum depth of placement under- 
water to date is about 400 feet. Major limitations on going deeper are 
difficulties in starting the flow and maintaining control of the flow 
without runaway of the high slump concrete in the typically 12-in. or 
greater diameter pipe. Special approaches have been tried such as foot 
valves and pipe-within-pipe methods but these do not promise an order- 
of-magnitude increase in depth capability without considerable development 
of relatively complex methods. Also, the total weight of tremie pipes 
filled with concrete becomes very great with increasing depths. 
Bucket Method. Large and small quantities of concrete have been 
successfully placed underwater by covered, bottom-opening buckets of up 
to several cubic yard capacity. Bucket placement is used primarily in 
relatively shallow water although depth is restricted more by operational 
considerations than by technical limitations. Stiffer concrete with 
larger aggregate (up to several inches diameter) can be placed by bucket 
