Units meeting the definition of WWTUs (§ 260.10) are exempt from the requirements of §§264 and 265, which include the closure requirements. (See §§§264/265.1(g)(6).)
It is important to note that the WWTU exemption applies to the unit itself, and not to the waste. Therefore, any waste that is removed from a WWTU is subject to full RCRA regulation.
The following guidance documents provide additional information regarding the WWTU exemption:
Memo, Gray to Munger; April 1, 1985 (RCRA Online #11066)
Memo, Lowrance to Hopkins; August 15, 1990 (RCRA Online #11551)
Memo, Porter to Philipp; January 2, 1986 (RCRA Online #12532)
Memo, Porter to Philipp; January 2, 1986 (RCRA Online #12527)
Memo, Williams to Davis; December 24, 1985 (RCRA Online #11118)
Monthly Call Center Report Question; February 1995 (RCRA Online #13727)
The guidance documents cited above are available in the RCRA Online database at the following URL: https://rcrapublic.epa.gov/rcraonline
A hazardous waste which is generated in a product or raw material storage tank, a product or raw material transport vessel, a product or raw material pipeline, or in a manufacturing process unit or an associated non-waste-treatment-manufacturing unit, is not subject to regulation under 40 CFR Parts 262 through 265, 268, 270, 271, and 124 or the notification requirements of Section 3010 of RCRA until it exits the unit in which it was generated, unless the unit is a surface impoundment, or unless the hazardous waste remains in the unit more than 90 days after the unit ceases to be operated for manufacturing, or for storage or transportation of product or raw materials (40 CFR §261.4(c)). This exclusion does not apply to a treatment unit.
In addition, it is important to note that this guidance represents clarification of the Federal regulations. Most states are authorized to implement the Federal regulations. We recommend that you also contact your state's implementing agency to acquire additional information on WWTUs. The Office of Resource Conservation and Recovery (ORCR) has compiled a complete list of phone numbers and waste program Web sites maintained by EPA Regional offices and state environmental agencies to help users locate the appropriate agency within their states. This compilation is found at the following URL: www.epa.gov/hwgenerators/links-hazardous-waste-programs-and-us-state-environmental-agencies