Via http://ea-lit.freshwaterlife.org/archive/ealit:1559/OBJ/19000504.pdf

Some extracts

Where EC Directives standards, particularly those for metals and/or pH, are not met due to natural causes,
we can recommend a derogation, that is these standards will not apply. The imperative standard for zinc
was exceeded in the Angarrack Stream in 1993.  A derogation for zinc applies to this stretch.  A
derogation for zinc also applies at Carnegwen Reservoir, though this site did not exceed the imperative
standard for zinc between 1993

The area is predominantly rural but the expansion of existing towns and villages and individual developments could increase the flood risk in some cases to an unacceptable level if the watercourse that receives the runoff has insufficient capacity to cope with the extra flow. Our aim is to identify these problems before they occur and either object to the development or request that compensation works are carried out in advance of the development aaaaa