(8) Test Procedures . A thorough study o£ salinity observations 

 made throughout San Diego Bay showed that the maximum variation in salin- 

 ity from surface to bottom, from one side to the other, and from the 

 entrance to the south end is only 0.5 part per thousand, which indicates 

 a well-mixed estuary with no significant density currents. Therefore, 

 the use of both freshwater and saltwater in the model was unnecessary, 

 and the model was operated only with freshwater. After the usual hydrau- 

 lic verification of tides and tidal currents, a dye-dispersion experiment 

 conducted in the prototype by the Federal Water Quality Administration 

 (now Environmental Protection Agency) was duplicated in the model, and 

 the results showed that dispersion rates and patterns in the model were 

 very similar to those observed in nature (see Fig. 3-40). After this had 

 been established, additional dispersion tests were conducted in the model 

 for existing conditions and for the two possible second entrances (see 

 Fig. 3-62). The model dispersion tests involved discharging equal quan- 

 tities of a fluorescent dye at three injection point locations (see Fig. 

 3-62) for 15 diurnal tidal cycles (24.84 hours each), then terminating 

 the releases and continuing model operation for an additional 35 diurnal 

 tidal cycles to observe dispersion of the dye. 



(9) Summary of Test Results . The results of the three tests are 

 summarized in Figure 3-63 which shows dye concentrations at given stations 

 throughout the bay at tidal cycles 15, 30, and 45 (dye was released during 

 the first 25 tidal cycles) for each test. The curves labeled "base test" 

 represent existing conditions; curves for plan 1-C represent the northerly 

 of the two second entrances tested, and curves for plan 6 the southerly of 

 the second entrances. The test results indicated an overall improvement 

 in flushing characteristics throughout the bay for both plans tested, 

 although dye concentrations were increased during certain phases of the 

 dispersion tests in certain areas for both plans. Dye concentrations 



for plan 1-C were generally significantly lower than those for plan 6, 

 although the peak concentrations for plan 1-C were higher than those for 

 plan 6 in the central part of the bay at higher high water slack and in 

 the extreme southern end of the bay at lower low water slack. 



For both plans, the tidal range in the southern part of the bay was 

 reduced by about 0.5 foot; the elevation of high water was lowered while 

 the elevation of low water was raised. Maximum velocities in the north- 

 em part of the bay were generally reduced by 60 to 80 percent; in the 

 southern part the velocities were relatively unchanged or showed increases 

 in the immediate vicinity of the proposed second entrance. A nodal point 

 developed in the central part of the bay where there was little horizontal 

 water movement at any time during the tidal cycle. The current pattern 

 photos showed that the nodal point during the ebb tide was about 6,000 

 feet south of that during the flood tide. Thus, a net southward circu- 

 lation was created, with a net inflow through the existing entrance and 

 a net outflow through each of the proposed second entrances. 



h. Water Quality--New York Harbor . 



(1) Project . Proposed inlet to Sandy Hook Bay. 



152 



