224 



TABLE IV.4.6.— MILITARY CARGO AND PASSENGERS TRANSHIPPED THROUGH CONTINENTAL U.S. WATER PORTS' 



I With the exception of the Great Lakes. 



2 1 measurement ton equals 40 cubic feet. 



3 Dollar amounts represent cost, not revenue, which is computed on predetermined billing rates. 



« No movement reported. 



Source: Quarterly progress report. 4th quarter fiscal year 1957, RCSDD-IL (Q) 493, Military Traffic Management and 

 Terminal Service, Washington, D.C. 



ESTUARINE MINING AND PROCESSING 



Actual extraction of both hard and soft minerals from the estuaries 

 is presently limited. By far the most valuable and potentially profit- 

 able mining activities in the estuary areas are petroleum extraction, 

 gas and sulphur recovery, and sand, gravel, and shell dredging. It is 

 important to note that the primary activity of extraction, with the 

 exception of sand and gravel dredging, has had relatively little effect 

 on the estuarine environment. Such secondary activities as petroleum 

 refining, transport by pipeline or ship, and petrochemical processing 

 have had much greater impact. Finally, the marginal activities which 

 grow up to support the populations drawn to areas of heavy petro- 

 leum extraction and secondary industry also place a heavy burden on 

 the quality of the estuarine zone. 



Petroleum (oil and gas) dominates present and projected mining 

 activity in the offshore regions of the United States, accounting for 

 over 84 percent of offshore mineral production in 1966. Offshore 

 sources supply a relatively small, but rapidly increasing, share of the 

 total domestic oil output. 



As table IV.4.7 illustrates, offshore production of petroleum has 

 grown steadily in the past decade, rising from less than 3 percent of 

 total production in 1958 to nearly 10 percent in 1967. If exploration, 



