bottom samples demonstrated that extensive silting has occurred in the ship 

 channel and bays. Low dissolved oxygen, hydrogen sulfide production, and 

 high organic content of the mud in the channel, all indicative of organic 

 pollution, prevent the establishment of a normal bottom fauna. In the bays 

 adjacent to the channel the dissolved oxygen concentration is independent 

 of the flow rate of the San Jacinto River, being dependent on phytoplankton 

 production of oxygen and, at certain seasons of the year, fluctuating widely 

 in a diurnal cycle. The concentration may range from supersaturation to 

 extremely low concentrations in a relatively short period. 



A small temperature gradient was found in the ship channel, 2° to 3° 

 higher in the upper channel than in the lower part of the survey area. 

 When the dissolved oxygen level is sufficient, a large and diverse popula- 

 tion of fishes exists throughout the bays in the survey area and for a con- 

 siderable distance above the Humble Oil & Refining Company's outfall. The 

 species composition of this population varies with the season, with predom- 

 inantly marine fishes during the summer when the salinity is high and predom- 

 inantly freshwater fishes in the winter when the salinity is lower. Both the 

 number of species and the diversity of fishes present decreased farther up the 

 the channel. 



27. CHAPMAN, C, "Channelization and Spoiling in Gulf Coast and South Atlantic 

 Estuaries," Pvoceedings of the Marsh and Estuary Management Symposivm, 

 Louisiana State University, Baton Rouge, La., 1967, pp. 93-106. 



Several methods of channel construction are used that permit varying 

 degrees of control over the resulting spoil. Mechanical excavation with 

 bucket dredges or draglines provides good spoil control on a small area. 

 Hydraulic excavation, however, requires large spoil areas and affords poor 

 control unless the spoil is removed from the construction site (hopper dredge) 

 or retained within ring levees. 



Disadvantages of channelization and spoil dumping include the segmenta- 

 tion of bays, which promotes shoaling; increased saltwater intrusion; in- 

 creased flushing time; altered tidal exchange, mixing, and circulation; 

 increased turbidity; and loss of submerged aquatic vegetation. However, 

 none of these changes are as significant as the direct physical loss of a 

 habitat. 



Advantages of channels and spoil deposition include the connection of 

 isolated waters and marshes, which make them available as fish nursery areas; 

 the provision of routes of escape or refuge for fish during cold periods; the 

 improvement of water exchange and circulation; and the release of nutrients 

 trapped in bottom sediments. 



Suggestions are made for planning channels and depositing spoil to reduce 

 the loss of vital bay and marsh habitats.. 



28. CHASE, G.L., "Evaluation of Environmental Effects Associated with Sidecast 

 Dredging," Froaeedings of the Eighth Annual Offshore Technology Conference, 

 Vol. 2, 1976, pp. 621-646. 



Sidecast dredging has been employed annually in the New England region for 

 the past 4 years. Operation of the dredge is restricted to inlet channels and 

 ocean sand shoals. Physical and chemical analyses of sediment samples from 18 

 navigation projects confirmed that dredged material consists primarily of clean 



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