cation factor applied to determine the permissible 

 concentration of toxicant. 



(2) Pesticides. 



(a) Chlorinated hydrocarbons: Any addition 

 of chlorinated hydrocarbon insecticides is likely to 

 cause damage to some desired organisms and 

 shotild be avoided. 



(b) Other chemical pesticides: Addition of 

 other kinds of chemicals used as pesticides and 

 herbicides can cause damage to desirable orga- 

 nisms and should be applied with utmost discretion 

 and caution. Table III-5 (p. 62) lists the 48-hour 

 TLm values of a number of pesticides for various 

 types of fresh water organisms. To provide rea- 

 sonably safe concentrations of these materials in 

 receiving waters, application factors ranging from 

 Mo to Vioo should be used with these values 

 depending on the characteristic of the pesticide in 

 question and used as specified in (4), below. 

 Concentrations thus derived may be considered 

 tentatively safe under the conditions specified. 



( 3 ) Other Toxic Substances. 



(a) ABS: Concentration of continuous expo- 

 sure to ABS should not exceed Vr of the 48-hour 

 TLm. A concentration as high as 1 mg/l may be 

 tolerated occasionally for periods of time not ex- 

 ceeding 24 hours. ABS may increase the toxicity 

 of other materials. 



(b) LAS: The concentration of LAS should 

 not exceed 0.2 mg/l or Y-, of the 48-hour TL„. 



(4) Application Factors: Concentration of ma- 

 terials that are nonpersistant (that is, have a half- 

 life of less than 96 hours) or have noncumulative 

 effects after mixing with the receiving waters 

 should not exceed %o of the 96-hour TLn, value 

 at any time or place. The 24-hour average of the 

 concentration of these materials should not exceed 

 1/4 of the TLn, value after mixing. For other toxi- 

 cants the concentrations should not exceed Yoq 

 and Vioo of the TL^ value under the conditions 

 described above. Where specific application factors 

 have been determined, they will be used in all 

 instances. 



(5) General Considerations. When two or more 

 toxic materials that have additive effects are pres- 

 ent at the same time in the receiving water, some 

 reduction is necessary in the permissible concen- 

 trations as derived from bioassays on individual 

 substances or wastes. The amount of reduction re- 

 quired is a function of both the number of toxic 

 materials present and their concentrations in re- 

 spect to the derived permissible concentration. An 

 appropriate means of assuring that the combined 

 amounts of the several substances do not exceed a 

 permissible concentration for the mixture is 

 through the use of following relationship: 



\K^u ■ ■ ■ +L„-V 



Where C;„ Cb, . . . Cn are the measured concen- 

 trations of the several toxic materials in the water 

 and La, Lb, . . . L„ are the respective permissible 

 concentration limits derived for the materials on 

 an individual basis. Should the sum of the several 

 fractions exceed one, then a local restriction on 

 the concentration of one or more of the substances 

 is necessary. 



Marine and estuarine organisms 



Salinity 



To protect estuarine organisms, no changes in 

 channels, basin geometry, or freshwater influx 

 should be made which would cause permanent 

 changes in isohaline patterns of more than 10 per- 

 cent of the naturally occurring variation. 



Currents 



Currents are important for transporting nutri- 

 ents, larvae, and sedimentary materials for flushing 

 and purifying wastes, and for maintaining patterns 

 of scour and fill. To protect these functions, there 

 should be no changes in basin geometry or fresh- 

 water inflow that will alter current patterns in such 

 a way as to adversely affect existing biological and 

 sedimentological situations. 



PH 



No materials that extend normal ranges of pH 

 at any location by more than 0. 1 pH unit should 

 be introduced into salt water portions of tidal tribu- 

 taries or coastal waters. At no time should the in- 

 troduction of foreign materials cause the pH to be 

 less than 6.7 nor greater than 8.5. 



Temperature 



In view of the requirements for the weU-being 

 and production of marine organisms, it is con- 

 cluded that the discharge of any heated waste into 

 any coastal or estuarine waters should be closely 

 managed. Monthly means of the maximum daily 

 temperatures recorded at the site in question and 

 before the addition of any heat of artificial origin 

 should not be raised by more than 4 F during the 

 fall, winter, and spring (September through May), 

 or by more than 1.5 F during the summer (June 

 through August), North of Long Island and in 

 the waters of the Pacific Northwest (north of 

 California), summer limits apply July through 

 September; and fall, winter, and spring limits ap- 



35 



