401(k) Plan abandoned and missing contributions

I have an unresponsive client who sponsors a 401(k) plan with prevailing wage.  They have not deposited the owed prevailing wage into the plan for months, and are now potentially shuttering their doors and just walking away.  What do I give them to impress upon them how they need to fund the contributions?  I haven't been able to find anything concrete here, on the IRS website, DOL website, or ASPPA book, but maybe I am just searching incorrectly?

You may want to point them to this law suit where the Department of Labor stepped in to recover the Davis-Bacon contributions:

https://www.planadviser.com/government-contractor-accused-of-missing-401k-payments/

If anyone were to bring your client's situation to the attention of the DOL, the DOL very likely would intervene.  (Note that the suit later was dropped by the DOL after the past due contributions plus earnings were paid.)

The employer might fear enforcement from workers and organized labor even more than enforcement by the US Labor department’s Employee Benefits Security Administration.

The employer might want its bankruptcy lawyer’s advice about which debts are nondischargeable.

Each of the employer’s owners and executives might want one’s lawyer’s advice about the extent to which the individual might be personally liable regarding the employer’s debts.

This is not advice to anyone.