Sanitation Facilities

We are contractors at this company and are not alowed to use the sanitation facilities near our workplace. The facilities we must use is about 2km away from our place of work. The reason giving my the company is that to many people are using the perminent staff facilities and the ablution facilities can not handle the volume. We work in shifts and the maximum amount of people per shift are eleven employees (day shift) the rest of the time only four people are at work. My question is, what can we do to resolve this problem. Our work is very critical and if we leave our place of work to long it could have serious complications in the processs of what they are manufacturing.
* Sorry didn't know which category to choose...