IV-423 



DREDGING AND FILLING OPERATIONS 

 Laguna Madre 



One good example of water quality changes from dredging and 

 filling operations is South Bay of the Laguna Madre system in 

 Texas (Figure IV. 5. 30). The dredging and redredging of the 

 Brownsville ship channel resulted in almost complete enclosure 

 of the South Bay from Laguna Madre. Settlement of suspended 

 sediment has caused a 60 percent reduction in depth in South Bay 

 and has changed the bottom characteristics from desirable vegeta- 

 tive habitat to soft mud. The water circulation has been reduced 

 and salinities have increased, and composition of the biological 

 community has been altered in terms of number and density of 

 species (IV-5-10). 



UNDERSEAS MINING OPERATIONS 



Petroleum production in the estuarine areas of the Nation is now 

 big business. The pollution potential of this extraction industry 

 is staggering to the imagination. The damage that could occur to 

 fish, wildlife recreational utilization, and shoreline structures 

 from well blows and broken pipelines is immense. The oil industry 

 is well aware of this hazard, and since 1955 there have been only 

 eight such incidents. The primary pollutional effects of these 

 occurrences to date have been high mortality of waterfowl in the 

 area of the oil slick and nuisance contamination as a result of 

 oil washing onto shoreline areas. 



