What additional steps does a food plant need to take when undergoing construction?

I would like to get suggestions on how to reduce the risk of contamination, during construction.

More envirnomental swabs, air sampling

Depends on what you're producing, size of your facility, areas separation, degree of your product exposure, etc. More details are required:)

Surely swabs and sampling is about verification, rather than actually reducing the risk?

Exactly how is best to manage it will very much depend on your facilities, what you're doing, where, how much space you have etc.
Generally the preference is likely to be that you don't produce whilst undertaking construction work in the same area, for obvious reasons.

As olenazh suggests, if you can provide some more detail on exactly what you're trying to do then forum members may be able to give some more specific suggestions and advice.

We've been on a number of consults for ground up and construction.  

There are most times extensive installations of preventors needed (draping, air suckers, portable particulate cleaners, etc.) so that the need for swabbing is not the main need + you will need to have extensive over-watch of contracted workers if you are in production at same time.

Here is so additional information

 Plant will be down Thurs-Sun. During the downtime- expand a room adding more panels, addition of a entry way in to expanded area. Cooler add wall divide the room, block off two dock doors with panels. Current roll -up door into production room. Will block off entry way, and relocate entry way to back side of the room.

Recent questions.

Listeria issue when tearing down walls. How do we control micro issues. Plant was built in 1990.

During production- the site will continue to build walls in non production areas during production. 

What are some of the risks?