11830 Federal Register / Vol. 55, No. 61 / Thursday, March 29, 1990 / Rules and Regulations

system set forth in 40 CFR 262.11 is

effective, the Agency believes that

imposing a testing requirement does

have some merit, in that it could

increase the accuracy of determinations,

could clarify the responsibilities of

generators, and could facilitate

compliance monitoring.

The Agency will continue to evaluate

the comments on this issue as well as

explore other options for a testing

requirement. At present, however, the

Agency is not yet ready to go forward

with a testing requirement based on any

of the options it has evaluated thus far.

Should the Agency decide that an

appropriate approach is available, it will

propose and solicit comment upon the

details of that approach in a separate -

rulemaking. In the meantime, the

Agency believes that the existing

determination requirement (as specified

at 40 CFR 262.11), as well as the liability

for incorrect determinations, is effective

and practical.

H. Applicability to Wastes Managed in

Surface Impoundments

As discussed above, in response to

the proposed TC, EPA received many

comments questioning the validity of

applying the TC to wastes, including

wastewaters, likely to be managed in

surface impoundments. In response to

commenters' concerns, on May 18.1987,

EPA published a Supplemental Notice of

Proposed Rulemaking in the Federal

Register, which requested comments

and data on several issues related to the

regulation of wastes managed in surface

impoundments under the TC rule. The

Agency also requested comment

(assuming such an approach) on: (1) The

criteria to be used to determine whether

the surface impoundment scenario

should apply to a particular waste, (2)

the point at which concentration

measurements should be made (e.g., at

the point of generation or within the

impoundment), and (3) how multiple

surface impoundments should be

handled under the TC rule.

Comments received in response to the

notice concerning the surface

impoundment management scenario are

summarized and addressed in section

II.A.2.c. Comments received in response

to the notice, which addressed sampling

point and multiple impoundment issues,

are discussed below.

1. Sampling Point

In the May 18, 1987 notice, EPA

requested comments on whether

evaluations of wastes managed in

surface impoundments should be based

on measurements of the concentration in

the impoundment or at the inlet to the

impoundment. In response, some

commenters supported sampling at the

inlet to the impoundment and stated that

sampling the waste within the

impoundment is not only contrary to

Congressional intent, but conflicts with

EPA's own regulations that require the

determination of hazard to be made at

the point of generation.

Other commenters, however, argued

that wastes should be sampled within

the impoundment or that the

impoundment effluent should be

sampled. Many of these commenters

argued that measuring the

concentrations in the impoundment

more accurately represents the

concentrations of hazardous

constituents that pose a threat to ground

water. Some commenters argued that

evaluation of hazard should be based on

impoundment effluent because

concentrations of the wastewaters

within the impoundment are

approximately the same as the

concentrations in the impoundment

effluent.

If the Agency were to allow persons

to make their determinations on the

waste in the impoundment, it would

raise questions that the Agency has not

yet evaluated completely nor taken

comment on. For example, in this

situation, should the Agency actually

require testing; if so, how often and

what should be tested? Would such a

result allow persons to land dispose of

wastes that (but for the point of hazard

determination) would be hazardous,

contrary to Congressional intent? Would

such a result allow persons to treat

wastes without a permit and thus be

inconsistent with Congressional intent?

EPA concedes that, for some activities

(e.g., closure), leachate quality may be

more appropriately assessed by

measuring concentrations at multiple

sites within the impoundment.

The current rules require that the

determination of whether a waste Is

hazardous be made at the point of

generation (i.e., when the waste

becomes a solid waste). (A waste must

be a solid waste before it can be

classified as a hazardous waste under

RCRA.) EPA believes that determination

of the regulatory status of a waste at the

point of generation continues to be

appropriate, especially since the Agency

is not developing a separate

mismanagement scenario or set of

regulatory levels for wastewaters. To be

consistent with other hazardous waste

regulations and until the Agency

addresses the above questions, EPA is

retaining the existing approach of

requiring sampling at the point of

generation.

2. Multiple Surface Impoundments

In the May 18, 1987 notice, EPA

requested comment on how multiple

surface impoundments or "treatment

trains" should be handled under the TC

rule. Some commenters favored

regulating all surface impoundments in a

treatment train as a single unit-if the

first impoundment treats a hazardous

waste, all impoundments would be

required to comply with the RCRA

regulations for hazardous waste

treatment facilities. Other commenters,

however, suggested that each

impoundment should be regulated

individually. Still other commenters

stated that owners and operators should

be required to determine whether the

most upstream surface impoundment is

treating wastes that exhibit the TC, but

they should only be required to evaluate

downstream impoundments If an

upstream impoundment exhibits the TC.

As discussed above, the Agency has

decided not to develop a separate

regulatory scheme for surface

impoundments. Thus, the Agency will

continue toregulate all surface

impoundments as individual units and

will not pursue any of the other options

discussed by commenters. Currently,

under 40 CFR part 261, each surface

impoundment in a series of multiple

surface impoundments is regulated

separately. If a surface impoundment

receives or generates a hazardous

waste, the owner or operator of the

impoundment is required to comply with

the RCRA regulations governing

hazardous waste treatment, storage, and

disposal facilities. On the other hand, if

a downstream impoundment is not

treating or generating a

characteristically hazardous waste and

upstream units have not managed, listed

wastes, then the downstream unit is not

subject to RCRA subtitle C

requirements.

I. Relationship to Other RCRA

Regulations

1. Hazardous Waste Identification

Regulations

a. Hazardous Waste Listings. Under

the June 13. 198, proposal, the

hazardous waste listings in subpart D of

40 CFR part 261 would not be affected.

All the listings would remain in effect,

including those listings that were based

on the presence of TC constituents. It is

EPA's intention that the hazardous

waste listings would continue to

complement the revised TC as they had

the EPTC.

A number of commenters, however,

argued that the TC should supersede

certain hazardous waste listings. In

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