E.5 Fasttabs Modeling System for Evaluation of Hydrordynamic Transport

b. Step 5.2:

8 Et L

W≥

8(0.0441m 2 / sec-1 )(190 m)

W≥

(0.579m/sec-1 )

W ≥ 10.8 m

This condition is amply satisfied since W equals 146 m.

Step 6 - Estimate maximum width of mixing zone. Estimate the

maximum mixing zone width as:

0.484 Qe Ce

Y-

u( C s - Cb )d

0.484 (0.425m3 /sec-1 ) (3.5 10-3 mg/L )

0.579m/sec-1 ( 2.5 - 1.0) 10-4 mg/L  ( 2.54m )





Y = 3.3m (10.7 ft )

Since the mixing zone is predicted to have a length of 623 ft (190 m) and a

maximum width of 10.7 ft (3.3 m), it is within the allowable limits of 750 ft

(228.6 m) from the effluent outfall.

E.5 Fasttabs Modeling System for Evaluation of

Hydrodynamic Transport

Rivers, reservoirs, and estuaries have been modeled for a number of years

using the USACE TABS numerical modeling system. TABS is a family of 2-D

numerical models that can simulate hydrodynamic, sediment, and constituent

transport processes in these water bodies. TABS has been used to simulate far-

field dispersion of instantaneous and continuous dredged material discharges.

Some independent near-field analysis is usually required. TABS can handle

complex geometries and unsteady flow conditions. Either particulate or

dissolved phases of dredged material can be modeled.

The TABS system consists of many separate programs that individually

address different aspects of the modeling process (Thomas and McAnally 1990).

These include mesh development, geometry input file generation, boundary

condition definition, hydrodynamic input file generation, job status monitoring,

and post-processing of the results.

E14

Appendix E Evaluation of Mixing in Surface Waters