REPORT DOCUMENTATION PAGE 



Form approved 

 OMB No. 0704-0188 



Public reporting concern for the collection of information is estimated to average 1 hour per persons inculding the time for reviewing 

 instructions, searching exsisting data sources gathering and measuring data needed and correcting and reviewing the collection of 

 information. Send comments regarding this burden estimate or any other aspect of this collectikon of information including 

 suggestions for reducing this burden to Washington Headquaters Services, Directoriate for Information Observations and Records, 

 1216 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302 and to the Office of Management and Support. 



1. AGENCY USE ONLY (LEAVE BLANK) 



2. REPORT DATE 



July 1996 



3. REPORT TYPE AND DATES 



Final Report 



4. TITLE AND SUBTITLE 



Bathymetric and Subbottom Survey at the Cornfield Shoals Disposal Site, July 8, 1994 



6. AUTHORS 



M.B. Wiley 



6. FUNDING NUMBERS 



7. PERFROMING ORGANIZATION NAME(S) AND ADDRESS(ES) 



Science Applications Intenational Corporation 

 22 lThrid Street 

 Newport, RI 02840 



8. PERFORMING 

 ORGANIZATION REPORT 



SAIC No. 23 1 



9. SPONSORING/MONITORING AGENCY NAMES(S) AND ADDRESS(ES) 



US Army Corps of Engineers-New England Division 

 424 Trapelo Road 

 Waltham, MA 02254-9 149 



10. SPONSORING/ 

 MONITORING AGENCY 



DAMOS Contribution 

 Number 110 



11. SUPPLEMENTARY NOTES 



Avaiable trom : DAMOS PROGRAM MANAGER Regulatory Division, USACE-NED 



424 Trapelo Road 

 Waltham, MA 02254-9149 



12a. DISTRIBUTION/A VAIABILTY STATEMENT 



Approved for public release; distribution unlimited 



12b. DISTRIBUTION CODE 



13. ABSTRACT 



Over 100,000 m3 of mechanically dredged fine-grained material was released at a taut-wire moored buoy at the 

 Cornfield Shoals Disposal Site (CSDS) during disposal operations in 1991 and 1992. Despite the fact that this is a high energy 

 dispersive disposal site, the fine-grained dredged material did form a mound that was detected during bathymetric and REMOTS® 

 surveys in 1 992. Over time, active bed transport of ambient sediment at the site has produced areas of accumulation and areas of 

 loss. Active bed transport also may have caused the fine-grained deposit to be covered by sand. If sand has been transported over 

 the fine-grained material, the usefulness of REMOTS® sediment-profile photographs in mapping the dredged material deposit is 

 limited. The sand makes it difficult for the camera prism to penetrate to the depth of the dredged material. Due to the limitation of 

 the REMOTS® method, a swept frequency subbottom profile survey was conducted at CSDS in 1994 to map the extent of this 

 fine-grained deposit. 



The 1994 bathymetric survey detected minimal accumulation (25 cm) over the disposal mound since 1992. The 

 1 994 bathymetry also detected accumulations over a broad area southeast of the disposal mound. At the disposal location, the 

 subbottom profile survey detected an acoustic horizon at 1 m below the seafloor. Southeast of the disposal location, the subbottom 

 record identified a sand wave field. Taken together, the results of the bathymetry and subbottom surveys mapped evidence of fine- 

 grained dredged material accumulation at CSDS as well as evidence of active bed transport of ambient sand. 



Fine-grained material was released at CSDS to examine whether this dispersive site was suitable for the disposal 

 of cohesive, mechanically dredged silts and clays. The survey results suggest two approaches to the management of fine-grained 

 dredged material at CSDS. Fine-grained material is likely to accumulate at CSDS if it is disposed at a taut-wire moored buoy. 

 This management approach would allow close management of the material, but it may reduce site capacity. Fine-grained material 

 may not accumulate if it is disposed in relatively small volumes at numerous discrete locations (e.g., LORAN-C coordinates). If 

 the release of fine-grained dredged material is managed this way, resuspension and dispersal may prevent mound formation and 

 retain site capacity. 



14. SUBECT TERMS ,, . _ w ■* ■ » A. o XI rr>™ mm 



Cornfield Shoals Disposal Site (CSDS), bathymetric survey , Remote Monitoring of the Seafloor(REMOTS) 

 subbottom surveys, dredged material, dredged silts and clays 



17. SECURITY CLASSIFICATION OF REPORT 



UNCLASSIFIED 



18. SECURITY CLASSIFICATION 

 OF THIS PAGE 



19. SECURITY CLASSIFICATION 

 OF ABSTRACT 



15.NUMBER OF PAGES 



L8 



16. PRICE CODE 



20.LIMITATION OF 

 ABSTRACT 



