226 



These fia^iires reinforce those already cited and identify the Gulf of 

 Mexico biophysical region as the probable future focus of continental 

 U.S. petroleum recovery and secondary processing growth. Alaska, 

 perhaps includins; the Bering Sea and Arctic margins, is also certain 

 to be an area of increasing exploration, recovery, and refining. 



The mining of sand and gravel from the estuary floor does not com- 

 pare in economic importance to the extraction and processing of 

 petroleum and sulphur. The present value of sand and gravel produced 

 in coastal bays and estuaries is estimated to be between $18 and $v50 

 million a year. Marine shell deposits, particularly oyster shell, have 

 been harvested for years, mainly in the Gulf of Mexico and San Fran- 

 cisco Bay. Production of shell was estimated to be about 21 million 

 tons in 1966, with a value of approximately $33 million. 



Yet, the mining of sand, gravel, and shell has a significant impact on 

 estuarine conditions wherever it is practiced. Unlike petroleum, the 

 mining of these aggregates is not the spur for industrial and popula- 

 tion expansion. The reverse is true. Demand for coastal and estuarine 

 deposits of aggregates is the direct result of metropolitan growth and 

 related urban demands for cheap construction material in the form of 

 concrete and other building products. 



Since suitable construction aggregates are found nearly universally 

 on the Atlantic, gulf, and Pacific coasts, and transportation of these 

 materials often makes up one-half or more of the costs to the con- 

 sumer, present and future growth of this industry in the coastal - 

 estuary zone will be dependent on increasing urban developments, and 

 the availability of competing deposits on the land surface. Thus, pro- 

 jections of growth of coastal -estuarine extraction of aggregates are 

 difficult due to the fact that local demand-and-supply conditions are 

 now and will continue to be the major determining factor in decisions 

 to exploit marine aggregate resources. 



Sources of aggregate extracted from supplies in coastal rivers and 

 estuaries already provide the principal source of sand and gravel for 

 such metropolitan areas as New York, Philadelphia, Baltimore, Wash- 

 ington, D.C., Norfolk, Mobile, and New Orleans. Oyster shell is a 

 major source of cement and associated lime requirements in Galveston 

 Bay, Tex. Significant quantities are also mined in the San Francisco 

 Bay. It seems reasonable to conclude that as urban areas continue to 

 grow through suburban expansion, as land values rise and as zoning 

 restrictions are tightened, that the demand for estuary reserves of 

 sand, gravel, and shell will grow. Offshore dredging on a massive scale 

 is presently precluded due to the high cost of building suitable dredges, 

 technological difficulties of deep-water recovery, and competing re- 

 sources on land and the estuaries. 



Salt is an obvious yet relatively insignificant product extracted from 

 estuarine water. Only three of over 100 salt-producing operations are 

 located in estuarine areas. Their total production in 1967, valued at $17 

 million, was about 7 percent of the total U.S. production. Such activity 

 in estuarine areas is bound to decline as pressure is exerted by more 

 competitive uses of estuarine land. 



Current interest in exploiting phosphorite and manganese nodules 

 and contiguous deposits of nickel, cobalt, and copper is limited by 



