ments. Such impacts could add greatly to the cost 

 of improvements, either in financial outlays to 

 mitigate them or in the loss of wildlife resources. 



In some cases, loss of wDdlife resources may 

 prove greater than the benefits of navigation 

 improvements. For example, the James River, 

 which flows into the Atlantic Ocean in soutliern 

 Virginia, serves as the navigation outlet for the 

 City of Richmond. However, conditions in the 

 James River are ideal for production of seed 

 oysters, and one of the Nation's foremost oyster 

 beds is located in the James River estuary. 

 Enlarging the channel, as has been proposed, could 

 so alter bottom conditions and salt and fresh water 

 relationships that the oyster resource might be 

 seriously damaged, perhaps eliminated. 



Another example of the influence of resource- 

 environmental considerations relates to a reach of 

 the St. John's River in Florida. Proposals have been 

 made to canalize the section of the river between 

 Lake Monroe and Lake Harney. However, this 

 section is a principal spawning area for a signifi- 

 cant anadromous fishery, the American shad. The 

 shad run in the St. John's river has been increasing 

 generally over the past decade and has come to 

 represent an important commercial and recreation 

 fishing resource. 



Detailed investigations indicate that with a 

 navigation project including locks, in operation, 

 the water velocity in the river channel would be 

 insufficient for shad spawning and hatching. Silta- 



tion conditions also would be modified, adversely 

 affecting the fishery. Because of the potential 

 damage to the shad resource, studies of navigation 

 improvement have been suspended indefinitely. 



Under certain circumstances, further extensive 

 deepening of harbors and channels entails danger 

 to another major resource— fresh water supplies. 

 These underground supply sources, called aquifers, 

 may extend under harbors or channels. It is 

 possible that harbor or channel deepening opera- 

 tions could damage the impervious layer of protec- 

 tive rock, permitting salt water to seep into the 

 aquifers and thereby degrade or pollute municipal 

 water supplies. 



A specific instance of this problem has been 

 encountered in the study' * of further navigation 

 improvements on the Delaware River, which serv- 

 ices the port of Philadelphia. Preliminary investiga- 

 tions indicate that deepening of the channel from 

 its present 40 feet to a depth of 50 feet would 

 necessitate blasting and removal of rock- 

 impervious rock which now protects a major 

 aquifer. A deepening project could, therefore, 

 cause damage to the aquifer. The exact dimensions 

 of the problem are exceedingly difficult to deter- 

 mine and evaluate, but the potential adverse 

 effects cannot be ignored in project evaluation. 



Channel deepening in estuary areas also can risk 

 intrusion of tidal, salt water above those points 

 where fresh water is drawn from channels for 

 municipal or irrigation supplies. Again, referring to 

 the Philadelphia study, deepening of the existing 

 channel could lead to intrusion of salt water upon 

 a major intake supplying fresh water to 

 Philadelphia. Control barriers, including navigation 

 locks, can be constructed to help control salt 

 water intrusion. Yet such facilities add to project 

 expense and could significantly comphcate ship- 

 ping operations. 



Appendix C summarizes problems described in 

 the preceding sections which would be experi- 

 enced in deepening major harbors. Shown in the 

 table are the present authorized depths for 102 

 U.S. harbors and depths at which problems due to 

 dislocations, rock. Continental Shelf, water re- 

 sources or ecology might occur. The data comes 

 from various U.S. Army surveys and in many 

 instances is very preliminary in nature. 



Figure 8. Channel dredging at Providence, 

 Rhode Island. Deeper channels may require 

 removal of bedrock at great expense. (U.S. 

 Army Corps of Engineers photo) 



18, 



U.S. Corps of Engineers, Preliminary Study of 

 Navigation Improvements on the Delaware River, 1968. 



111-71 



