[Code of Federal Regulations]
[Title 40, Volume 22]
[Revised as of July 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR227.29]

[Page 215-216]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 227--CRITERIA FOR THE EVALUATION OF PERMIT APPLICATIONS FOR OCEAN 
DUMPING OF MATERIALS--Table of Contents
 
                         Subpart G--Definitions
 
Sec. 227.29  Initial mixing.

    (a) Initial mixing is defined to be that dispersion or diffusion of 
liquid, suspended particulate, and solid phases of a waste which occurs 
within four hours after dumping. The limiting permissible concentration 
shall not be exceeded beyond the boundaries of the disposal site during 
initial mixing, and shall not be exceeded at any point in the marine 
environment after initial mixing. The maximum concentration of the 
liquid, suspended particulate, and solid phases of a dumped material 
after initial mixing shall be estimated by one of these methods, in 
order of preference:
    (1) When field data on the proposed dumping are adequate to predict 
initial dispersion and diffusion of the waste, these shall be used, if 
necessary, in

[[Page 216]]

conjunction with an appropriate mathematical model acceptable to EPA or 
the District Engineer, as appropriate.
    (2) When field data on the dispersion and diffusion of a waste of 
characteristics similar to that proposed for discharge are available, 
these shall be used in conjunction with an appropriate mathematical 
model acceptable to EPA or the District Engineer, as appropriate.
    (3) When no field data are available, theoretical oceanic turbulent 
diffusion relationships may be applied to known characteristics of the 
waste and the disposal site.
    (b) When no other means of estimation are feasible.
    (1) The liquid and suspended particulate phases of the dumped waste 
may be assumed to be evenly distributed after four hours over a column 
of water bounded on the surface by the release zone and extending to the 
ocean floor, thermocline, or halocline if one exists, or to a depth of 
20 meters, whichever is shallower, and
    (2) The solid phase of a dumped waste may be assumed to settle 
rapidly to the ocean bottom and to be distributed evenly over the ocean 
bottom in an area equal to that of the release zone as defined in 
Sec. 227.28.
    (c) When there is reasonable scientific evidence to demonstrate that 
other methods of estimating a reasonable allowance for initial mixing 
are appropriate for a specific material, such methods may be used with 
the concurrence of EPA after appropriate scientific review.