Jane,
 
I do not wish to sound like a purist. If you are in a situation where  
federal laws are no help and bad people lurk beyond the fence and there is zero  
budget for security and time is of the essence, then desperate measures need to  
be taken. I have seen situations in which backhoes ripped the earth around  
trashpits and the contents gently tipped into skiploader buckets for recovery  
elsewhere. I have also seen situations where triage was performed in the field  
to recover as much as can be recovered from what appears to be the richest  
deposits. 
 
However, I do not believe this is appropriate methodology. I would  encourage 
that you work out a better procedure with the government agent who  caused 
you to be there, the client who is paying, and any local stakeholders who  have 
demanded your work. If there is any budget at all, I recommend you rent  those 
same steel plates that trenching companies use to allow cars to drive over  
their work at night and bring a skiploader out to place them over the features  
during the off hours. Believe me, no bottle hunter can lift those plates.
 
Ron May
Legacy 106, Inc.