Portland, Maine, area (EPA 1987). The majority of recent disposal activities have been 

 restricted to the northern half of the site, at continually moored marker buoys. The 

 southeastern corner of PDS (Figure 1-2) has been selected as the site for disposal of 

 material from the Royal River under the Capping Demonstration project. 



Water depths within the southern half of PDS range from roughly 40 to 70 m 

 (Figure 1-2) as determined from recent bathymetric surveys conducted by SAIC. For the 

 Oceanographic Measurement Program, instrumentation was moored in the southwestern 

 corner of PDS to minimize potential short-term effects of dredged material disposal on 

 near-bottom turbidity. 



PDS is susceptible to storms because of unlimited fetch toward the south and 

 southeast. Large waves during winter storms are expected to generate substantial currents 

 which may reach the seafloor within the site and hence cause resuspension of fine-grained 

 material, whether ambient or derived from dredged material. 



PDS is characterized by rocky, irregular relief composed of a complex network of 

 bedrock outcrops, steep ridges caused by glacial scour, and small topographic depressions 

 containing natural sedimentary deposits of gravel, sand, silt, and clay (Morris 1996). 



The temporal variability of water properties and near-bottom currents within PDS is 

 poorly understood, as there have been few site-specific measurements. The only known 

 current measurements were acquired in August and September of 1979 using an instrument 

 situated 1.5 m above the seafloor (NUSC 1979). The observations showed that near- 

 bottom currents are generally weak (less than 1/3 knot), but because the instrument only 

 acquired current measurements at 2-minute intervals, the data were insufficient for 

 assessment of high-frequency processes (i.e., surface wave effects) that may affect bottom 

 sediment resuspension. Current measurements at other locations within the western Gulf 

 of Maine indicate that currents are generally weak (less than Vi knot) and dominated by the 

 semi-diurnal tide. Likewise, no time series of meteorological conditions (e.g., wind and 

 wave characteristics) have been acquired within the site, but long-term, near-continuous 

 data can be obtained from NOAA buoy 44007 located 6 km southwest of PDS (see Figure 

 1-1). 



1.3 Project Objectives 



The primary objective of the Oceanographic Measurement Program was to monitor 

 and evaluate the physical processes that may affect the long-term physical stability of 

 capped disposal mounds at PDS. Moored instrumentation was deployed in the 

 southwestern corner of the site from late February to early May 1996 in order to acquire 



Oceanographic Measurements at the Portland Disposal Site during Spring of 1996 



