E.6 Dilution Volume Method for CDF Effluent Discharges

A new graphical implementation of TABS (FastTABS) (Lin, Jones, and

Richards 1991) has been developed that successfully addresses the need for

efficient model setup, execution, and analysis. It is mouse driven with pull-down

menus and requires a minimum of manual data entry to complete an application

from start to finish. FastTABS was designed to allow easy application of each of

the models in the TABS system which include hydrodynamics, constituent, and

sediment transport. The FastTABS software runs on Macintosh and DOS-based

personal computers as well as most UNIX workstations. A primer, user's

manual, and tutorial are available.1

E.6 Dilution Volume Method for CDF Effluent

Discharges

E.6.1 Approach

A simplified approach to evaluation of mixing zones for CDF effluent dis-

charges is presented in this section in which the volume of water required for

dilution is expressed as a rate of flow (USAEWES 1976). This approach is

generally applicable in both riverine and estuarine conditions. However, the

approach should only be applied where there is a discrete discharge source such

as a conduit or a weir. Since the effluent discharge will occur at a specified rate

Vp, the volume of ambient site water per unit time that would be required to

dilute the discharge to acceptable levels can be defined as:

V A = V p D = V p [(C e - C BG )/ (CWQ - C BG )]

(E-10)

where

VA = volume of site water/unit time required for dilution, cfs

Vp = rate of effluent discharge, cfs

Ce = concentration of the contaminant in the effluent in ug/L

CBG = background concentration of the contaminant in the disposal site

water in ug/L

CWQ = applicable WQS for the contaminant in ug/L

It is assumed that the mixing zone associated with an effluent discharge will

resemble the shape in Figure E-2. Therefore, once the required volume per unit

A limited government license allows USACE office use of the FastTABS software

supplied through the USACE Waterways Experiment Station (WES). Other users may

obtain the software from Brigham Young University, (801)-378-5713. The point of

contact for additional information is: Dr. David R. Richards, USACE Waterways

Experiment Station, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199, (601)

634-2126.

E15

Appendix E Evaluation of Mixing in Surface Waters