Examine the sources of the town's water, to see if any seem to be sub-standard
The town's water comes from three wells, numbered 5, 6, and 7. Water from each well is supposed to be disinfected with chlorine at the source before it enters the general water- distribution system.
Of the three, Well 5 is the shallowest - only 5 metres deep. Its water comes from an area of highly fractured rock overlain by only a thin layer of soil: ideal conditions for surface contaminants to be carried down into the well water.
Well 5 was brought into service in 1979 without any special conditions attached to its operation, even though it was known from the start to be vulnerable to contamination from surface run-off. In 1994, new regulations required wells of this type to be fitted with continuous monitors that would automatically sound an alarm if chlorine levels became dangerously low or the water became turbid (had particles in it). Well 5, however, was never fitted with an automatic monitor.
Well 5 is the most obvious "weak link" in the physical structure of the water system.
To really understand how the infection has entered the water supply, and whether it did enter at this weak point, you have to
