14 



and coliforms), the differences are marked and may be impor- 

 tant. 



The nitrate, silicate, and to a certain extent the phos- 

 phate show double layers of high concentration, one at the 

 surface and one near or at the bottom. From about 2,000 feet 

 to 4,500 feet from the boil there is an intermediate layer 

 at a depth of 20 feet having low concentrations o The two 

 layers of high nutrient values meet at about 4,500 feet. 

 At greater distances the concentrations are relatively uniform 

 with depth but continually decrease by dilution and diffusion. 



The average profiles for oxygen and ammonia differ from 

 those of other nutrients, and are in themselves different. 

 The oxygen profile shows an unsaturated layer extending from 

 the outfall along the bottom for all distances samples (9,000 

 feet). The oxygen content in the upper 40 feet, except near 

 the outfall is high, and from a distance of 1,200 feet is at 

 or near saturation. The ammonia concentrations, which are 

 perhaps the best indication of sewage, are greatest in the 

 boil and from the surface to a depth of 10 or 15 feet. Below 

 15 feet ammonia is low and approaches the normal value for 

 shelf waters. High ammonia concentrations, 50 to 100 times 

 that of normal water, occur as far as 9,000 feet north of the 

 outfall, and it is probable that these high concentrations 

 extend even farther. 



The average values for both days emphasize the character 

 of the dispersion of the nutrients. Generally, silicate and 

 nitrate show strong concentrations in the top and bottom 

 layers 5 phosphate high at the surface and a moderate concen- 



