The Lower Cataract River is a 5km stretch flowing from Broughtons Pass Weir into the Nepean River at Douglas Park. (Douglas Park is 15km south of Campbelltown, NSW).
It was once a beautiful river with crystal clear water, flowing through steep 80m high cliffs, and loved by local residents, campers and canoeists.
Ten longwall mines went underneath this stretch in the 1990s, at a depth of 430m beneath the river bed. As a result the rocky bed was badly cracked in hundreds of places. The water was polluted by ingress of saline and acidic groundwater and by ecotoxic chemicals leaching from fractured Hawkesbury sandstone. A massive fish kill was reported by a fisheries inspector. 50% of the river’s flow was lost down the cracks. Methane gas vents erupted along the river, at one point measured at 20 litres per second – ten years later some vents are still active.
The river turned red in 1995 – 6, due to iron oxide reaction; ten years later it is a milky green colour except when flow is augmented by heavy rainfall. There are few fish, and algal blooms flourish while bacterial mats coat the rocky surfaces under water. Mining impacts have caused eleven rockfalls along the gorge, some small, some large. BHP Billiton erected warning signs along the cliffs and fenced off dangerous parts – it is not safe to walk here.
The following photos were taken by keen amateur photographer Tom Chapman, where the river flows through his property. The Chapmans lived on the river for over forty years and were dismayed at its fate. Tom has given us an invaluable record of the river before and after mining impacts.
The photos of the river in the left-hand column were taken in the 1970s, while those on the right were taken in 2005, ten years after mining had passed underneath this spot.
After mining had wrecked their river, eight families took BHP Billiton to court and won some compensation in 1998.
The Mining Warden, after hearing scientific and expert evidence from both sides, concluded that mining had caused 80% of the water loss and pollution, while the current drought was only responsible for 20% of the damage.
BHP Billiton has made little effort to remediate the damage by grouting up cracks. A few days’ work in 1999 was not very effective even in a limited section of cracking. They have not been back since.
Rivers SOS anyway believes that grouting is not a long term solution. Even a mild earth tremor will re-open cracks, and concrete will eventually crumble. The only solution is to prevent this irreparable damage in the first place, by mandating an adequate safety zone around river systems. More about this is written on the site spieless.home.blog.
In May 2005, six Rivers SOS members walked along the Lower Cataract River in order to make a photographic record of the cracks, as follows: