300 



Economic Aspects 



posal problem is given by the mere figures 

 for average volume of sewage in millions of 

 gallons per day: 4 for Santa Barbara, 4 for 

 Oxnard, 265 for Los Angeles City (at Hy- 

 perion), 180 for Los Angeles County (at 

 Whites Point), 35 for Orange County (near 

 the mouth of the Santa Ana River), 40 for 

 San Diego, and about 15 for all other coastal 

 communities. When discharged to the 

 oceans, these wastes must not constitute a 

 hazard to health of bathers, or be a threat 

 to commercial shipping and fishing, or be 

 esthetically offensive. Criteria set up by the 

 California State Water Pollution Control 

 Board must be met; chief of these is that the 

 coUform bacteria cannot exceed 10 per mil 

 in three consecutive samples or in more than 

 80 per cent of 20 consecutive water samples 

 tested. During the past this hmit has occa- 

 sionally been exceeded, mostly because of 

 leakage from outfalls, requiring the adop- 

 tion of measures such as chlorination of the 

 sewage and closing of beaches to the public. 



Because of the rapid growth of Los Ange- 

 les between 1945 and 1955 plans had to be 

 made to construct by 1960 new facihties 

 capable of handling an average of 420,000.000 

 gallons of sewage per day with storm peaks 

 of 720,000,000 gallons per day. The com- 

 plex question of whether Santa Monica Bay 

 might become seriously polluted by such a 

 great discharge of unchlorinated sewage led 

 to a thorough study by the University of 

 Southern California in 1955-1956 of oceano- 

 graphic conditions and the behavior of sew- 

 age discharges. This is probably the largest 

 oceanographic program ever conducted to 

 secure data for engineering purposes. On 

 its completion, a regular monitoring program 

 was set up for Santa Monica Bay by the City 

 of Los Angeles Bureau of Sanitation using 

 its own ship and facilities. Other general 

 pollution problems which arose from the in- 

 tensive study of the bay are being further 

 investigated by the University of Southern 

 California in a 5-year study of the mainland 

 shelf between Point Conception and Mexico 

 in a program supported by the California 

 State Water Pollution Control Board. 



The findings in Santa Monica Bay that are 

 of particular interest with respect to sewage 

 disposal may be briefly summarized. Cur- 



rents in the bay are slow, 80 per cent of the 

 observations by current meters, drift cards, 

 and drogues being about 0.2 knot (10 cm/ 

 sec) (Stevenson, Tibby, and Gorsline, 1956). 

 At an average concentration at discharge of 

 400,000 coliform bacteria per milliliter, dilu- 

 tion alone could not reduce the count to 

 below the acceptable limit; however, experi- 

 ments with patches of sewage tagged with 

 fluorescene dye and finally with radioactive 

 scandium showed that the T-90 (time for 90 

 per cent decrease in coliform count) varies 

 between 1.5 and 4.5 hours for primary efflu- 

 ent and between 3.0 to 6.5 hours for sec- 

 ondary effluent. Almost identical results 

 were obtained by the University of Southern 

 California and Los Angeles City investiga- 

 tions (Rittenberg, 1956; Gunnerson, 1958a, 

 1 958Z7). For primary effluent the decrease is 

 due mostly to sedimentation of solids to 

 which bacteria adhere, and for secondary 

 effluent it is due about equally to sedimenta- 

 tion, dilution, and mortality. When the new 

 effluent outfaU is built 8 km from shore, the 

 time required for effluent to drift inshore wiU 

 be 13 to 30 hours, so that after an initial 

 dilution of about 1 to 60 in the area of the 

 outfall the reduction en route to the shore 

 should be more than enough to comply with 

 state standards. An interesting side effect 

 of sedimentation was the finding of concen- 

 trations of more than 10,000 coliform bac- 

 teria per square centimeter on bottom off 

 Whites Point and Orange County outfalls 

 which discharge unchlorinated sewage and 

 maxima of 250 per square centimeter in 

 Santa Monica Bay where chlorination is stiU 

 practiced (Rittenberg, 1956; Rittenberg, 

 Mittwer, and Ivler, 1958). A Unear area of 

 high counts of bacteria on the bottom bor- 

 dering the entire southwest side of Palos 

 Verdes Hills marks the route followed by 

 sewage from Whites Point. The same area 

 is characterized by black sediment, locally 

 containing either (but not both) free hydro- 

 gen sulfide or Chaetopterus variopedatus, a 

 polychaete worm that serves as a pollution 

 indicator (Fig. 235). These studies of coli- 

 form bacteria in the water and in the bottom 

 are among the first that have been conducted 

 in nature — avoiding the uncertainties inher- 

 ent in the use of laboratory experiments. 



