Protecting a beauty spot from polluted mine water
Our client is a county council in the UK.
The location is a woodland park with a canal. An area of natural beauty, the site was once home to a colliery that opened in the mid-nineteenth century. Today it’s a popular spot for hikers, dog walkers, joggers, cyclists, and picnickers.
The reed bed is part of an unmaintained treatment scheme built in the nineties. Once cleaned, the abandoned mine water from the former colliery is used to fill the canal to maintain its level.
Visitors to the site had reported seeing orange water on towpaths, alongside ponding in the woodland, which was flooding and rotting tree roots. If trees die and fall, they are a severe hazard to the public.
Untreated water from abandoned mines is often orange because it contains iron which, when meets the air, turns into iron oxide (more commonly known as ochre). In this case, the polluted water was reaching the canal, which can be extremely harmful to wildlife.
However, when mine water is treated correctly, the iron and other minerals within the water are removed. This prevents pollution of the ground and surrounding watercourses.
During our investigation, it became apparent that the treatment works had not been maintained for a significant time and, therefore, became ineffective. This had the potential to cause physical damage to the site as well as environmental harm. That’s why we advised our client to close the scheme down until refurbishment.
The whole site was buried under foliage, making the site impossible to access safely to determine the extent of the works required.
The primary treatment was blinded with ochre. The settlement lagoon was sludge-ridden, full of iron deposits, and covered with reeds propagating across the site. The reed bed itself – used to filter out the iron oxide – was 90% blinded with ochre deposits and completely overgrown. In addition, the pipework was entirely blocked with sediment and deposits.
Phase one involved clearing the site to assess the scale of work needed to bring the treatment scheme back to operational condition. Time pressures were building as bird nesting season was just around the corner.
We deployed site clearance teams to cut down and remove the vegetation making the site safe to access. This revealed the entire asset base and will help clear the way for phase two access.
As this site is used by many locals, we were very sensitive to their needs. We minimised road and walkway closures, and our hand-cutting of grassland meadows reduced our impact on the environment.
Phase two will bring the site back to its former glory. This will involve: inspecting the control panel and its operation; driving the borehole and the level controls; cleaning all the blocked pipework; replacing the primary treatment works; emptying and cleaning out the settlement lagoon; fully refurbishing the reed bed; and cleaning the site exit pipework which feeds the canal with clean and treated water.
Sludge dewatering methods will remove and dispose of waste in the most sustainable way – of which 90% will be recycled. In the spirit of reuse, healthy reeds should be transplanted back into the refurbished reed bed to save costs.
Obstacles we overcame
We worked quickly to avoid the nesting season to protect the wildlife within the reed bed
We used utmost precision and care to make sure our work didn’t result in more pollution being discharged into the grounds and watercourses
A busy beauty spot
We considered the local community in every decision we made to minimise disruption, as this is a site with a high footfall
We proposed a full site access and movement plan to allow vehicles to access the site while protecting the environment, minimising disruption, and avoiding damage to the wildflower meadows that surround the treatment works
Once the project is completed, we’ll have:
- Resumed full operation of the treatment works
- Prevented a pollution incident
- Protected the reputation of our client
- Refurbished the reed bed so it works properly, looks nice, and is a home for plants and wildlife
- Recycled 90% of the waste from site
- Enhanced the natural beauty of the site