to the west in a narrow tongue. The 1.5 isotherm is 

 observed much farther to the west where it appears to begin 

 separating into multiple branches. A well defined eastern 

 edge to the plume as defined by a change in surface water 

 texture and a line of foam on the surface was observed in the 

 field. Dye concentration readings dropped to background 

 levels as this line was crossed. 



Vertical profiles (Figure 15) through the plume show the 4° 

 isotherm extends to the bottom at Station MFl but is at less 

 than 10' deep further out in the plume at Stations HFS and 4. 

 At Station MF5 south of White Rock, the base of the plume is 

 only 5' deep as indicated by the 1.5° isotherm. Station MF2 

 was located to the east of the visible plume edge and 

 recorded background levels only. Station MF5 located to the 

 west of Millstone Point indicates a trace of the plume at the 

 surface. This was not seen on the horizontal mapping data 

 and is believed to represent the effects of a minor eddy on 

 the northern edge of the plume. 



4. 3. 3 High Slack 



During high slack tide (Figure 12) the thermal plume is 

 relatively evenly distributed about the discharge point and 

 the center of the plume is shorter and broader than seen on 

 previous tidal phases. This difference between the core of 

 the high slack plume and the longer, narrower core of the low 

 slack plume is probably due to the change in tide elevations. 

 During low slack tide the elevation difference between the 

 quarry cut and Long Island Sound is greatest, producing 

 higher discharge currents at the cut than during high slack 

 tide. The greater currents would tend to carry the plume jet 

 further offshore. Lower current speeds during high slack 

 tide would allow the plume jet to spread out more quickly, 

 producing the shorter, broader pattern observed. The 4 



15 - 



