REPORT DOCUMENTATION PAGE 



form approved 



OMB No. 0704-01 S 



Public reporting concern for the collection of information is estimated to average 1 hour per response including the time for reviewing instructions, 

 searching existing data sources, gathering and measuring the data needed and correcting and reviewing the collection of information. Send comments 

 regarding this burden estimate or any other aspect of this collection of information including suggestions for reducing this burden to Washington 

 Headquarters Services, Directorate for information Observations and Records, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302 

 and to the Office of Management and Support, Paperwork Reduction Project (0704-0188), Washington, D.C. 20503. 



1. AGENCY USE ONLY (LEAVE BLANK) 



2. REPORT DATE 



May 1998 



3. REPORT TYPE AND DATES COVERED 



FINAL REPORT 



4. TITLE AND SUBTITLE 



OCEANOGRAPHIC MEASUREMENTS AT THE PORTLAND DISPOSAL SITE 

 DURING SPRING OF 1996 



6. AUTHOR(S) 



Scott E. McDowell and Stephen D. Pace 



5. FUNDING NUMBERS 



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



Science Applications International Corporation 

 221 Third Street 

 Newport, RI 02840 



8. PERFORMIGORGANIZATION 

 REPORT NUMBER 



SAIC No. 388 



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



US Army Corps of Engineers-New England District 



696 Virginia Rd 



Concord, MA 01742-2751 



10. SPONSORING/MONITORING 

 AGENCY REPORT NUMBER 



DAMOS Contribution #121 



11. SUPPLEMENTARY NOTES 



Available from DAMOS Program Manager, Regulatory District 

 USACE-NAE, 696 Virginia Rd, Concord MA 01742-2751 



12a. DISTRIBUTION/AVAILABILITY STATEMENT 



Approved for public release; distribution unlimited 



12b. DISTRIBUTION CODE 



13. ABSTRACT 



Under the Disposal Area Monitoring System (DAMOS) Program for the U.S. Army Corps of Engineers, New England District, Science Applications International 

 Corporation (SAIC) conducted an Oceanographic Measurement Program at the Portland Disposal Site (PDS). A single instrumented tripod was deployed from February 27 to May 



14, 1996, in order to acquire site-specific data on tides and near-bottom currents, water temperature, and turbidity. The tripod was deployed in the southwest corner of the PDS, in 

 a region of relatively rough topography having a water depth of approximately 60 m. Overall, the 78-day measurement program provided excellent data from which to characterize 

 near-bottom currents and turbidity, and evaluate the physical processes governing bottom sediment resuspension within the PDS. 



Vertical profiles of temperature, salinity, and density were acquired at a single location in the PDS during February, April, and May 1996. respectively. The February 

 profile revealed a water column that was very weakly stratified, as is typical for the coastal Gulf of Maine in winter. Water property characteristics during late April and mid-May 

 illustrated that relatively fresh and warm water had been introduced to the surface layer, presumably as a result of river discharge. Beneath a moderate thermocline and pycnocline, 

 water properties were nearly constant throughout the lower half of the water column during late spring. With regard to the vertical density stratification, it is apparent that the entire 

 water column to a depth of 60 m is very weakly stratified throughout winter and early spring, whereas the introduction of relatively fresh/warm waters at the surface during mid- 

 spring causes considerable stratification that may tend to decouple horizontal currents and other transport processes within a two-layer water column. 



Time series observations of winds, waves, atmospheric pressure, and surface water temperatures were acquired from NOAA buoy 44007, located 6 km southwest of the 

 PDS, to assess the seasonal and inter-annual variability in meteorological conditions from 1993 through 1995, as well as meteorological conditions during the 1996 measurement < 

 program. Analysis of the annual wave statistics revealed that wave characteristics were very similar for the 3.4 years of wave records. Significant wave heights less than 2 m 

 occurred from 90 to 95% of the time during each year. The maximum significant wave height observed in each of the four measurement years ranged from 5.6 to 7.3 m. Overall, 

 wave characteristics during the first half of 1996 were typical of other recent years at this location. 



Quantitative analysis of storm waves revealed 72 events during the 3.4-year analysis period that had significant wave heights between 3 and 4 m; average durations for 

 these wave events were only 6 to 8 hrs. Wave heights in the range of 5 to 6 m were observed only 22 times with average durations of less than 3 hrs. 



The wave records from March through May 1996 exhibited nine storm events attaining significant wave heights greater than 2 m, with one reaching 5.8 m. This storm 

 activity was similar to that during other recent years, and sufficient for analysis of storm-generated currents as they affect bottom sediment resuspension. 



The moored instrumentation at the PDS yielded nearly complete records of near-bottom currents, water temperature, pressure, and relative turbidity over the period from 

 late February to mid-May 1996. Hourly averaged near-bottom current speeds during the measurement period ranged from to approximately 0.4 knots ( ~20 cms' 1 ), with the 

 majority of the variability occurring at periods of approximately 12 hr in association with the semi-diurnal tide. Tidal harmonic analysis of the current velocity data revealed that the 

 amplitude of the M: semi-diurnal tidal current is weak (approximately 3 ems'), but significantly stronger than all other tidal constituents. 



Time-series measurements of near-bottom turbidity during the 78-day measurement period were acquired using optical sensors at levels of 33 and 81 cm above the 

 seafloor. Detailed analysis of the near-bottom current data during the nine storms revealed that high-frequency oscillatory currents could be induced by large-amplitude surface 

 waves, resulting in relatively high bottom stress and sediment resuspension as confirmed by elevated near-bottom turbidity levels. The field observations of near-bottom turbidity 

 were useful for documenting that sediment resuspension had occurred during a subset of the storms, but the measurement program was not designed to quantify the depth of erosion 

 nor the volume (per unit area) of sediment that had been eroded during the storms. Furthermore, additional analysis and numerical modeling of the data to determine the complex 

 interactions between wave height, period, and duration, the speed and direction of background currents, and the availability of fine-grained bottom sediments on sediment 

 resuspension at the PDS was beyond the scope of this project. 



14. SUBJECT TERMS current measurement, turbidity, suspended solids, thermocline . 

 pycnocline and wave dynamics 



15. NUMBER OF PAGE 62 



16. PRICE CODE 



17. SECURITY CLASSD7ICATION OF 

 REPORT Unclassified 



18. SECURITY CLASSIFICATION 

 OF THIS PAGE 



19. SECURITY CLASSIFICATION 

 OF ABSTRACT 



20. LIMITATION OF 

 ABSTRACT 



