Generally, your state regulatory authority must be informed about changes in the operation of your hazardous waste facility.
If your facility is a generator, transporter, or treatment, storage, and disposal facility (TSDF) and you need to make changes to information previously submitted on an 8700-12 form, you should review the information on submission of a subsequent form and contact your state's implementing agency. Subsequent submission information is available in the forms and instructions for the 8700-12 form, available at the following URL: http://www.epa.gov/epawaste/inforesources/data/form8700/forms.htm
If your facility is a TSDF and you need to make changes to information previously submitted in a permit application, you should review the regulations on permit modifications and contact your state implementing agency. Permit modification regulations can be found in 40 CFR §270.41 
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If you facility is an interim status facility, please refer to §270.72 , "changes during interim status."
Please note that many types of facility changes require prior approval by the permitting authority; it's important to understand these requirements before making operational changes. In all case, we recommend you contact the appropriate state agency regarding any additional requirements that may apply.