Two surveys were completed on November 2, A survey was run during maximum 

 flood while the dredge was stationed south of the Gateway Marine Terminal (Figure 3-9) and 

 another survey was conducted during the early ebb, after the barge moved north of the 

 terminal (Figure 3-10). The flood survey indicated that the plume extended northward for 

 approximately 400 meters. The United Illuminating outfall, located approximately 600 

 meters north of the barge, obscured the plume signal, and plume tracking in this region was 

 terminated. A small patch of the plume was observed to the west of the main channel, in 6 

 meters of water, 4(X) meters north of the barge (Figure 3-11). The survey run during the 

 beginning of the ebb shows that considerably smaller patches of the plume were advected 

 along the channel for a distance of approximately 250 meters south of the barge (Figure 3- 

 12). A small patch was observed 150 meters north of the barge, possibly a relict from the 

 previous flood. Dredge operations stopped and started throughout the survey, which may 

 explain the smaller, more variable nature of the patches. The CTD data, collected during the 

 early ebb, shows only slight density stratification (2-3 psu) within the top 2 meters, due 

 mainly to the proximity to upstream sources of fresher water, i.e., the Mill and Quinnipiac 

 Rivers, Surface to bottom temperature differences were less than a degree. 



The next day, November 3, the dredge was located in the vicinity of navigational 

 buoy "17" (Figure 3-13). The survey was completed during the first two hours of the ebb; 

 dredging was intermittent throughout the day. The plume trace was lost within 125 meters 

 downstream (Figure 3-14). Results of this survey were difficult to interpret due to 

 interference from wave turbulence; however, surface patches of black plume water were 

 visually spotted (no evidence of plume traces on the echo sounder) within the navigation 

 channel as far as 250 meters downstream. CTD data indicate a nearly vertically homogenous 

 water column with temperature differences from surface to bottom of less than a degree and 

 salinity differences of less than 2 psu. 



The dredge was located near buoy "16" (Figure 3-15) during two ebb surveys 

 conducted on November 11. Results of the first ebb survey, run during maximum ebb 

 currents, indicated that the plume traveled approximately 525 meters downstream along the 

 east bank of the channel (Figure 3-16) with excursions of 2(X) meters eastward onto the 

 adjacent shoals. The second survey (Figure 3-17), during the latter half of the ebb, shows the 

 plume again hugging the east bank for a distance of only 200 meters (Figures 3-18). 

 Currents were slack by the end of the last transect. The majority of the plume observed 

 during this second survey resides in deeper water with only minimal excursions (within 50 

 meters) over the adjoining shallows. Plume distributions in this area display some of the 

 characteristics of a density current, i.e., a gravitationally induced density contrast between 

 the sediment-laden plume and ambient waters (Figure 3-19). CTD casts, taken between the 

 two surveys, indicate a well mixed water column with negligible stratification. 



Dredged Sediment Dispersion in New Haven Harbor 



