RIASSUNTO
ABSTRACT
Shell dredging in estuarine areas started with the arrival of early settlers. Although modern techniques decreased the number of dredges, the output has increased considerably. In order to dredge, a dredging company must receive a permit from the proper state agency to remove such state-owned resources. In addition, federal permission from the U.S. Army,Corps of Engineers has to be obtained. To date, no permits are being issued without an environmental impact statement or sufficient data in the hands of controlling agencies. Opposing opinions as to the influence of shell dredging on the estuarine environment have resulted in serious conflicts between conservational and industrial groups.
Fossil shell is a very important raw material in the Gulf Coast coastal zone. The main users are manufacturers of cement and lime who supply the construction and chemical industries with tremendous quantities. Additional consumers of raw shell include poultry and cattle feed producers. The material is also used as road ballast. Fossil shell can play an important role in port activities. It is the second largest bulk cargo handled at the Port of Houston.
The source of fossil shell is diminishing and a change to limestone is inevitable. However, the present costs involved in the transport of shell inland or limestone toward the coast make it economically inefficient and impossible to initiate a change and transition.
Although the many estuaries along the Gulf Coast vary significantly in physical and biological aspects, it is striking that the various studies all point to the same general conclusions. The additional suspended load resulting from dredge discharge, the oxygen budget and the rapid salinity changes are considered to be the most important environmental aspects. The impact of fossil shell dredging on the estuarine environmental parameters is considerably less than one would suspect.
Studies resulting in an impact assessment can be very extensive, such as the one carried out in San Antonio Bay, Texas. Although the results do not indicate that shell dredging should be terminated, preconceived ideas resulted in aggressive reactions. Due to the many opposing ideas and often incomplete information, researchers of all Gulf states are compiling their findings into one book.
INTRODUCTION
The removal of shell material from estuarine waters began with the arrival of early settlers and has continued to present. With pick and shovel small quantities of mudshell were removed from subaerially exposed banks. Once it was discovered that shell banks also existed in totally submerged condition and that larger quantities could be found below the mudline, the removal of shell material became a lucrative industry. Today it has become an established industry and plays a significant role in the economic framework of the coastal zone.