trifugation. “Major constituents" are those water quality parameters deemed critical for the proposed dredging and disposal sites taking into account known point or areal source discharges in the area, and the possible presence in their wastes of the materials in §§ 227.22 and 227.31.

§ 227.62 Disposal of unpolluted dredged material.

Material which is determined to be unpolluted may be dumped at any site which has been approved for the dumping of settleable solid wastes of natural origin.

§ 227.63

Polluted dredged material.

Any dredged material which cannot be classified as unpolluted according to the requirements of § 227.61 is regarded as polluted dredged material.

§ 227.64 Disposal of polluted dredged material.

Polluted dredged material may be disposed of in the ocean if it can be shown that the place, time, and conditions of dumping are such as to produce a minimum impact on the marine environment. When material has been found to be polluted in accordance with § 227.61(c), bioassay tests may be performed when it can be shown that the results of such tests can be used to assist in setting disposal conditions. There is at present no adequate means to identify the potential long-range harmful effects of the leaching out of toxic and/or bioaccumulative pollutants into the marine environment after the dumping of polluted dredged material. To minimize the possibility of any such harmful effects, disposal conditions must be carefully set, with particular attention being given to the following factors:

(a) Disposal site selection.-(1) Disposal sites should be areas where benthic life which might be damaged by the dumping is minimal.

(2) The disposal site must be located such that disposal operations will cause no adverse effects to known nursery or productive fishing areas. Where prevailing currents exist, the currents should be such that any suspended or dissolved matter would not be carried into known nursery or productive fishing areas or populated or protected shoreline areas.

(3) Disposal sites should be selected whose physical environmental characteristics are most amenable to the type of

dispersion desired. Environmental characteristics which may promote minimum dispersion can include weak bottom currents, minimal bottom slopes, and the existence of naturally occurring finegrained bottom sediments. Natural depressions or borrow pits may provide desirable site characteristics in some areas. Environmental characteristics which may promote maximum dispersion can include strong bottom currents, deep bottom slopes, and the existence of naturally occurring coarse-grained bottom sediments.

(b) Dumping conditions.-(1) Times of dumping should be chosen, where possible, to avoid interference with the seasonal reproductive and migratory cycles of aquatic life in the disposal area.

(2) If the type of material involved and the environmental characteristics of the disposal site should make either maximum or minimum dispersion desirable, the discharge from and movement of the vessel during dumping should be in such a manner as to obtain the desired result to the fullest extent feasible.

§ 227.65 Revision of test procedures.

Test procedures and values mentioned above are based on the best currently available knowledge and are subject to revision and modification based on the general increase of knowledge or specific information on the effects of the disposal of dredged materials in the ocean. § 227.70

Definitions.

§ 227.71 Limiting permissible concentrations.

The limiting permissible concentration is that concentration of a waste material or chemical constituent identified in § 227.31 in the material to be dumped which, on the basis of scientific data, is believed to produce no long-term adverse environmental consequences, through bioaccumulation or otherwise, or in the receiving water which, after reasonable allowance for initial mixing in the mixing zone, will not exceed 0.01 of a concentration shown to be toxic to appropriate sensitive marine organisms in a 96-hour bioassay, or 0.01 of a level otherwise shown to be detrimental to the marine environment. The 96-hour bioassay and consequent 0.01 application factor are to be the result of the testing of a specific concentration of the waste material in seawater from the dump site, or similar to water from the dump site, that causes a 50-percent mortality of ap

propriate sensitive marine organisms in the 96-hour test period, or that produces another identifiable reliable physiological indicator of toxicity in such animals within the same time period. The 0.01 factor is based on the best available current experience and is subject to revision or modification based on the general increase in knowledge or specific information on the effects of a specific waste. § 227.72 Mixing zone.

A mixing zone is the column of water immediately contiguous to the release zone, beginning at the surface of the water and ending at the ocean floor, the thermocline or halocline, if one exists, or 20 meters, whichever is the shortest distance.

tion of the same constituent in a sample of natural seawater at the dumping site or in an adjacent area not subject to dumping.

§ 227.75 High-level radioactive wastes.

High-level radioactive waste means the aqueous waste resulting from the operation of the first cycle solvent extraction system, or equivalent, and the concentrated waste from subsequent extraction cycles, or equivalent, in a facility for reprocessing irradiated reactor fuels or irradiated fuel from nuclear power reactors.

§ 227.80

Amendment of criteria.

In the event that the Administrator or his delegate concludes that it is desirable to amend this part, he shall announce his intention of doing so by publishing notice thereof in the FEDERAL REGISTER, and shall thereafter follow the procedures prescribed in section 4 of the Administrative Procedures Act (5 U.S.C. 553). Any person proposing amendments to this part shall notify the Administrator of the amendments so proposed, and the justifications supporting the amendments so proposed. Should the Administrator reject the amendments so proposed, he shall notify the proponent of such action within 30 days of the date upon which such amendments were given to him.