256 



exceptional growth for southern California. Private and Federal de- 

 velopments in the San Diego Bay portion of the delta were of sufficient 

 magnitude to warrant flood control works on the river. Subsequently, 

 a separate flood control channel, which empties into the ocean, was 

 built for the San Diego Eiver, and some navigation dredging was done 

 in Mission Bay. 



During the same period of time (1900-1959), changes were occur- 

 ring in Mission Bay. In 1929, California incorporated Mission Bay 

 into its State park system. In 1945, title to the tidelands and sub- 

 merged lands was granted to the city of San Diego. The city passed a 

 $2 million bond issue for improvement of Mission Bay. It also coop- 

 erated with the Corps of Engineers, complying with all conditions 

 necessary to obtain a multipurpose flood control and navigation project 

 for the San Diego Eiver and Mission Bay. 



Since 1946, the venture has accomplished a completely separate flood 

 channel for the San Diego River, a superbly planned recreational 

 development in Mission Bay including private investments totaling 

 over $22,500,000 for support and service facilities, an orderly preser- 

 vation of habitat necessary for coastal fisheries, and open- water recre- 

 ation areas with water quality sufficiently high for all water-contact 

 sports. The bay has been zoned for various activities, banks have been 

 stabilized, and beaches have been created. All of this area is just a few 

 minutes drive from the center of San Diego. 



The total dredging effort in Mission Bay since 1946 has cost over 

 $6,500,000 and over 9,500,000 cubic yards of material have been 

 removed. Mission Bay stands today as a shining example of what 

 determined community effort can achieve (IV-5-6, IV-5-7). 



Section 2. Sources of Poixution 



Nearly all of man's activities can result in environmental degrada- 

 tion. The pollutants and polluting conditions outlined in the preceding 

 section are rarely unique to a particular use or specific activity, but 

 they result from man's existence in the estuarine zone as well as his 

 use of it. The major sources of pollution described in this section fall 

 into three broad categories : 



(1) Those sources associated with the extent of development of the 

 estuarine zone, including waste discharges from municipalities and 

 industries, and land runoff from urban and agricultural land. 



(2) Those sources associated with particular activities of great pol- 

 lutional significance, specifically dredging and filling, watercraft op- 

 eration, underwater mining, and heated effluent discharges. 



(3) External sources having impact derived through flow regula- 

 tion and upstream water quality. 



MUNICIPAL WASTES 



Over 8 billion gallons of municipal wastes are discharged daily into 

 the waters of the estuarine zone. While most of this volume is domestic 

 sewage, many municipal waste discharges also contain significant 

 amounts of industrial wastes, which may add to their variability and 

 complexity. 



