2.0 METHODS 



The July 1992 survey at PDS was designed to map the extent of dredged material at 

 the site, to evaluate the status of benthic recolonization, and to determine the effectiveness of 

 the capping operation by obtaining sediment chemistry data on site and at the reference areas. 

 To accomplish this, SAIC conducted a bathymetric survey, a REMOTS® sediment-profile 

 survey, an acoustic sediment density study, and sediment sampling for chemistry and grain 

 size. 



2.1 Bathymetry and Navigation 



The precision navigation required for all field operations was provided by the SAIC 

 Integrated Navigation and Data Acquisition System (INDAS). This system uses a Hewlett- 

 Packard 9920 series computer to collect position, depth, and time data for real-time 

 navigation. Contribution No. 60 (Parker and Revelas 1989) contains a detailed description of 

 INDAS and its operation. Positions were determined to an accuracy of ±3 meters from 

 ranges provided by a Del Norte Trisponder® System. All positions are in datum NAD 27. 

 For the present survey, shore stations were established at known benchmarks: Cape Elizabeth 

 Light (43°33.959' N, 70°12.034' W) and Portland Head Light (43°37.381' N, 

 70°12.502' W). 



The July 1992 PDS bathymetric survey was set up over the same area used in January 

 1989. The 900 x 1100 m area consisted of 45 lanes oriented east and west with 25 m lane 

 spacing. An ODOM DF3200 Echotrac® Survey Recorder with a narrow-beam 208 kHz 

 transducer recorded depth to a resolution of 3.0 cm (0.1 ft) as described in DAMOS 

 Contribution No. 48 (SAIC 1985). At the beginning of the survey, a surface-to-bottom cast 

 of a Sea-Bird Electronics, Inc. , Model SBE 19-01 conductivity-temperature-depth profiler 

 (CTD) was done to obtain accurate speed of sound data for the analysis. Analysis of the 

 bathymetric data was conducted using the Hydrographic Data Analysis System (HDAS). All 

 depth values were converted to Mean Low Water (MLW) after compensating for vessel draft 

 and tidal fluctuations that occurred while surveying. During analysis, position and depth data 

 were checked to identify and eliminate any outlying values before producing an accurate 

 contour plot. 



2.2 REMOTS® Sediment-Profile Photography 



A REMOTS® survey was conducted at PDS and reference stations on July 22 and 23, 

 1992. The orthogonal REMOTS® sampling grid at the disposal site was designed to map the 

 areal extent of the dredged material deposit and to confirm predictions about benthic 

 recolonization. Forty-two stations were surveyed at the disposal site. The three reference 

 areas, SEREF, SREF, and EREF (Table 2-1), were each surveyed in a 13-station cross- 

 shaped grid. Triplicate photographs were taken at all stations. 



Monitoring Cruise at the Portland Disposal Site, July 1992 



