and bottom circulation in the area of the disposal grounds has not been 

 obtained. The reason for this lack of understanding is that the Bight 

 dumping grounds are not strictly marine but have estuarine characteristics. 

 The hydrographic conditions in this area constantly change as freshwater 

 flows from the Hudson and Raritan Rivers into the oceanic environment. 

 Generally, conditions in the Bight are similar to those off the mouths 

 of large rivers. 



The flow of the Hudson and Raritan Rivers varies seasonally from less 

 than 0.6 X 10^ to more than 1.3 x 10^ cubic feet per day. With such an 

 influx freshwater, it would be expected that the distribution of physical 

 properties would be greatly affected. Paradoxically, a study of hydro- 

 graphic conditions in the Bight by Ketchum, et al (1951) has shown that 

 when- the river flow was great, a steady state condition existed and the 

 distribution of properties was explainable. When the river flow was 

 low, the patterns were erratic, changeable, and unpredictable. 



To maintain a steady-state condition within the Bight, nontidal drift 

 of mixed water in a net seaward direction must be taking place. To counter- 

 act rapid flushing, and to maintain the steady-state condition, a large 

 quantity of ocean water must also enter the area. This oceanic counter- 

 drift would be expected to be rich in oxygen and nutrients. The study by 

 Ketchum and his associates, concluded that an active circulation pattern 

 exists in the Bight having a beneficial cleansing action on whatever 

 pollutants enter the area. The rate of flushing was estimated to be 

 from 6 to 10 days, and to be independent of the river flows, but depend- 

 ent on tidal oscillations. 



This active circulation pattern within the Bight was inferred by 

 studying the spatial distribution of properties and by identification of 

 water masses and boundary conditions. Although it appears correct in 

 explaining total water mass exchange and drift, it does not answer 

 immediate questions concerning circulation patterns within the dumping 

 grounds . 



The Sandy Hook Laboratory (SHL) attempted to directly measure the 

 circulation in the Bight related to the movement and dispersal of dumped 

 materials. SHL established a sampling grid of 23 hydrographic stations 

 in part of the Bight (Figure 9) and made periodic measurements of tempera- 

 ture, salinity, and dissolved oxygen. Attempts to measure directly 

 velocity, current direction, and particulate transports were made, but 

 were partially unsuccessful. Three of four current meters placed at 

 fixed stations, 40 feet above the bottom within the study area (Points 

 A, B, C, Figure 9), gave satisfactory records for only limited periods. 

 The results of this current data are discussed in the section on bottom 

 circulation. Estimates of surface and bottom sediment transport were 

 obtained by SHL using seabed and surface drifters. The Seabed drifter 

 used was a positively buoyant plastic saucer (diameter 18 cm) fastened 

 to a small diameter stem 54 cm long. The free end of this stem was 

 weighted so that the whole drifter had a slight negative buoyancy. Sur- 

 face drifters were small bottles ballasted to float vertically and to 



39 



