267 



MINERAL EXPLOITATION 



Commercial exploitation of the mineral resources in estuarine areas 

 is another potentially significant waste source. Three types of extrac- 

 tive activities exist in the estuarine zone: (1) sub-bottom mining of 

 sulfur and petroleum, (2) mining of materials such as sand, gravel, 

 and oyster shell from the estuarine bottom, and (ii) mineral extraction 

 directly from the water. Each creates a different water-quality 

 problem. 



The sub-bottom operations, especially for petroleum, interfere with 

 the aquatic habitat m several w^ays. In the exploration phase, the use 

 of seismic explosions can be detrimental to the biota in the immediate 

 vicinity. Drilling activities always present the potental threat of a 

 blowout or rupture resulting in a wild well (fig. IV.5.17). Potential 

 problems in the production phase include the possibility of collision 

 or storm damage to the rig and the disposal of the oil well brine. 

 Transportation of oil whether by ship or pipeline poses an additional 

 pollution threat. 



In sulfur mining, the Frasch process is generally used; super- 

 heated water (325° F.) is pumped into the sulfur formation and 

 molten sulfur is pumped out. The bleedoff waters must be vented from 

 the deposit, and these waters are highly saline with a rather high 

 hydrogen sulfide content (fig. IV.5.18) . 



Both petroleum and sulfur mining cause a secondary impact due to 

 the shoreline support facilities that accompany their development. 



The shoreline development creates problems similar to those dis- 

 cussed under municipal and industrial waste sources. 



Mining from the estuary floor causes alteration of the estuarine 

 shape and water circulation characteristics. A secondary effect is the 

 turbidity problem associated with material removal. Mining of sand 

 and gravel from the estuarine floor is universal, while oyster shell 

 dredging in any great quantity is restricted to the gulf coast. These 

 operations remove part of the estuarine floor with a concomitant de- 

 struction of habitat and life. There are also great amounts of sus- 

 pended and settleable solids frequently released in the water, from 

 which they are redeposited in other places. Phosphate mining, common 

 in North Carolina and Florida, may introduce nutrient phosphates 

 and toxic fluorides into the water. 



Extraction of minerals from sea or estuarine water is the third type 

 of mining activity. Minerals extracted include common salt, magnesium 

 oxide, magnesium metal and bromine. Available information indicates 

 that the pollutional impact of the water extraction process is 

 insignificant. 



The extent of estuarine mining activities is shown in table IV.2.8. 

 On a nationwide basis the subbottom mining industry is restricted to 

 the Gulf coast of Texas and Louisiana, and the coasts of California and 

 Alaska. Isolated areas of the other types of mining activity also are 

 shown in the table. The economics of bottom mining and of water ex- 

 traction compared to the availability of materials from other sources 

 seems to preclude extensive development, except for materials such as 

 sand and gravel. 



