Here you can seen a street map of the Bristol area including the route that NSI takes underground.

Bristol's Northern Stormwater Interceptor, nicknamed 'The Motherload' by drainers, is a massive stormwater drain which acts as a flood prevention measure for Bristol, completed in the mid 90s.

Building of the Northern Stormwater Interceptor (NSI) started in 1962 to relieve flooding over many parts of the city. The Severn Estuary has the highest tidal range in the country and the Avon is tidal right up to the city. Because of these high tidal ranges the level of the Avon can, during spring tides, be higher than the low-lying parts of the city.