3-54) completely eliminated the crosscurrent. Shorter extensions of the 

 training jetty reduced the strength and duration of the crosscurrent but 

 did not eliminate it. 



d. Training Structures — Delaware River . 



(1) Project . Rehabilitation of existing dikes. 



(2) Reference . U.S. Army Waterways Experiment Station (1956, 

 1964). 



(3) Laboratory . WES. 



(4) Test Period . April to November 1963. 



(5) Problem . Reedy Island Dike (Fig. 3-55), constructed in 

 1887 to 1917 to a total length of 17,000 feet, was designed to concen- 

 trate flow into the main channel east of Reedy Island and thus reduce 

 serious shoaling that occurred in that part of the estuary at the time 

 the dike was constructed. Pea Patch Dike, constructed in 1930-34 to a 

 total length of 19,000 feet, and Pennsville Dike, constructed in 1942-43 

 to a length of 5,000 feet, were built for the same basic reasons. At the 

 time of the model studies all three dikes were seriously deteriorated, and 

 estimates for rehabilitating the structures to design conditions showed 

 that expenditures of $5 million each would be required to restore Reedy 

 Island and Pea Patch Island Dikes, and $1,500,000 to restore Pennsville 

 Dike. 



(6) Purpose of Model Study . Model tests were conducted to de- 

 termine: (a) The effects of Reedy Island and Pea Patch Island Dikes on 

 hydraulic conditions in the estuary, and if the flow regimen so required, 

 the extent of dike rehabilitation necessary; and (b) the additional bene- 

 fits that would be derived from restoring deteriorated sections of Penns- 

 ville Dike to a crest elevation of about 2 feet above MHW rather than to 

 the elevation of mean tide level. 



(7) The Model . The Delaware Estuary model (Fig. 3-56) reproduced 

 the entire tidal part of Delaware Bay and River from the Capes to Trenton, 

 New Jersey, to linear scales of 1:1,000 horizontally and 1:100 vertically. 

 Before the dike studies, the entire model had been carefully adjusted and 

 verified for tides, tidal currents, and salinity conditions throughout the 

 full range of freshwater inflows. 



(8) Test Procedures . All three dikes were subjected to hydrau- 

 lic tests for existing and design conditions, and for essentially a com- 

 pletely deteriorated condition of each dike. After these tests were 

 completed and the results analyzed, further tests were made with certain 

 parts of the dikes restored to design conditions and other parts left in 

 a deteriorated state. 



140 



