FTE - social builidng by factory

Hi, I have a problem with caluclating FTE for our NC project. The building is a social - office building consisting of 2 floors - ground floor is a social part for factory workers and second floor is an office part. On the groud floor - there is a canteen, showers and toilets for factory workers and first floor - we have typical office space. As the water usage in the building will be generated by the factory workers (working 24h/d), that come in into the factory through the discussed building, how to treat them? should they be treated as partial FTE (let's say they spend 2 hours a day in this building - half an hour in changing rooms in the morning, 1 hour for lunch and half an hour in the evening to change clothes) or should they be trated as transints? the bicycle racks will be provided in discussed building as well.... Many thanks.