What is there at the moment
Glastonbury uses about 14 litres of water per person per day Page 4
BS8551:2001 claims that "Festival sites (camping) concessions" require 25-50 litres per person per day (!).
So that would make our requirements: 14~35 * 500 * 3.5 = 24500~61250 litres
Taps should be of closed type to minimise water wastage.
We need to use a commercial supplier Page 1.
Anglia water do temporary supplies but this requires piping to be laid etc which may turn out to be expensive and time consuming. Probably the preferred solution though, but would require land owners permission etc.
If we got the stool tanks (that hold 2800l) we could get 5 + 5 refills to give us 28,000l. This would also give us 5 locations round the site to get water from.
Costs: (617*5)+(387*5)= £5020
For budgetary purposes £6000 shall be used
Glastonbury's use is documented
Most camping festivals provide a number of tap points of varying sophistication (from tap on a post to sink with drainage). It is a minimum provision for camping healthily and the licensing authority will probably have a view on it. This is covered in the HSE document for running festivals.
A very useful trick when on a grass site is to put pallets down where the water point is, so you don't have to stand in mud to get water by the second day.
Where does used water (ie from washing) go? What drainage facilities are there on the site? The sanitation is likely to be self-contained so we need a separate consideration of how to dispose of 'grey water' other than pouring it into the stream on site (which is, clearly, not an acceptable option!)