First, please note that I am licensed to practice law in California, not Hawaii, and in any case I cannot dispense specific legal advice in this forum.
However, I am a qualified legal research and can speak in gerneral terms about the law.
Please keep in mind that lawyers cannot always deliver favorable information .
In Hawaii, cleanup of toxic waste sites is governed by HRS 128D Hawai‘i Environmental Response Law (HERL).
Recovery of costs is specifically authorized at HRS 128D-5.
The only time limits are that actions for recovering costs must be filed within 6 years of finishing the cleanup.
Liability for toxic waste sites is detailed at HRS128D-6.
Liability attaches not only to the property possessor who actually caused the contaminations, but also attaches to subsequent possessors/owners under the theory that they should have discovered the contamination and so are charged with constuctive knowledge of the contamination.
The are exceptions to liability, such as contamination caused by natural disaster or war, or where the property came into possession of somewhere who had no actual knowledge of the contamination, and who could not reasonbly be expected to have discovered the contamination.
None of those conditions seem to be applicable in the scenario described.
As a matter of general response with respect collections of such large debts, especially with a state agency, negotiation can be extremely helpful and easing the burden, if it cannot be removed.
There may also be some public funded resources to assist independant, family run businesses for this type of situation.