129 



The results from the environmental predictive models are de- 

 scribed in my written testimony. 



The results of the study lead to the following conclusions. One, 

 placement of subject wastes on the abyssal sea floor with no accom- 

 panying loss to the water column appears feasible with modest ad- 

 vancements in technology. Initial indications are that the abyssal 

 waste isolation option will be cost competitive with present waste 

 management methods for higher priced areas. 



Two, model predictions suggest that for reasonable waste isola- 

 tion scenarios, the placed waste would likely be contained locally 

 within a defined site, would burj' local fauna which would be re- 

 placed by different, more opportunistic abyssal communities, and 

 would impact geochemical processes beneath the waste site for 

 thousands to tens of thousands of years. 



Three, the Atlantic offers the most favorable sites for waste isola- 

 tion. The Pacific sites are less favorable. The Gulf of Mexico offers 

 poor choices for isolation sites. 



Four, overall impacts of placed waste are predicted to be local- 

 ized. 



Our recommendations are, one, an in situ experiment using 

 uncontaminated, organic-rich, fine-grained dredged material would 

 be needed to generate the data necessary for further development 

 and validation of models to predict changes in physical, biological, 

 and chemical environments of the abyssal sea floor if perturbed by 

 large-volume deposits of contaminated dredged material. 



'^0, research must be undertaken to better predict the perform- 

 ance of waste-filled geotextile bags, especially hydrodynamic re- 

 sponse and geotextile strains during release from a transport plat- 

 form, descent through the water column, and impact on the sea 

 floor. 



Three, development of technologies necessary for the handling, 

 bagging, and transport of contaminated dredged material would be 

 needed to ensure technology availability when, and if, environ- 

 mental acceptability of the abyssal sea floor waste isolation option 

 is demonstrated. 



In June 1995, NRL was funded by the Advanced Research 

 Projects i^ency [ARPA], to extend portions of this paper study, ap- 

 plying advanced simulation technologies to the waste isolation 

 problem with focus on the end-to-end simulation and visualization 

 of the relocation of contaminated dredged material to the abyssal 

 sea floor and the potential environmental impact. The scope of this 

 new project is summarized in my written testimony. 



My colleagues and I thank the chairman and the committee for 

 this opportunity to make the results of our work known to the sub- 

 committees. I will be happy to answer any questions you may have 

 on our work. 



[The prepared statement of Dr. Valent follows:] 



