The final twelve month checks have been carried out by the Coal Authority on a new pipeline that keeps river free from polluted mine water near to Bacup.
The original pipeline was replaced last year in a 3 month operation because its deterioration risked up to 80 litres of untreated mine water spilling into the river every second, damaging its ecosystem.
After years of sitting in the river, which flows past Manchester and into the River Mersey, the foundation blocks had moved, bending the pipes and moving them out of alignment.
Contractors for the Coal Authority, JN Bentley Ltd, carried out the work with help from business partners Severn Trent Services.
The entire river was dammed and a series of pumps moved the water past the areas of work, allowing excavators and engineers onto the riverbed.
Sections were then excavated and large, pre-cast, interlocking concrete blocks were fixed into position to take the weight and firmly anchor the pipe.
Coal mining has taken place around Bacup and in the vicinity of the River Irwell for hundreds of years. Old Meadows, or Scarr End as it was also known, was formally recognised as a coal mining concern in 1854. It operated under different owners, right up to its closure under the National Coal Board in 1969. Its peak output of coal was recorded as 30 tons per day.
The adit, on Burnley Road, is one of the most prominent remaining features of the mining activity in the valley. Originally, the mine water went straight into the River Irwell, but is now treated in settlement lagoons and a reed bed before being returned to the river.