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PART 2 - The solution - No 9 Adit:

Diagram showing work undertaken at Cwmrheidol in early 1993.

The National Rivers Authority (now the Environment Agency) commissioned Simon Hughes and I to tackle the problem. This we did in 5 stages:

1. Create large lagoon to catch any sudden surges during works. The lagoon was floored with hundreds of tons of powdered limestone.

2. Remove scree above and behind the dam in order to expose it properly.

3. Pump out clear water sitting on top of ca. 0.5m of ochre, liming the discharge every 15 minutes thus raising the pH from 2.5 to 5.5. This stage went on on a 24-7 basis.

4. Pump out ochre into the large lagoon and bury with powdered limestone.

5. Remove dam and repair broken lagging.

Some aspects of this utterly messy but ultimately successful job are illustrated below.

Setting up pumps
Opening up the adit mouth and setting up pumps. A considerable amount of scree had to be cleared off the back of the adit. The excavator dug well back to allow for further landslides, this permitting access to a "porthole" into the water at the back of the dam. A submersible pump was lowered just under the surface of the water, to avoid stirring up the ochre below. A digital pH meter was installed in the mine discharge, a large stash of agricultural lime was placed just upstream and we were ready to go.

Inside entrance to No 9 adit, Cwmrheidol. The dam lies ahead...
A view up the adit during pumping. The dam lies ahead in the darkness. While pumping was ongoing the adit floor up to the dam was cleared of debris.

Removing the dam
Once the water and ochre had been pumped well down, work commenced on tackling the dam, a mixture of fine shale, soil and soft ochre. In this image the dam is half-removed. The burst lagging where the shale came in is above and to the left of the dam.

Ochre, unsafe timbers and bad air make the mine beyond very unpleasant
Beyond the dam lay the inky depths of the mine which was explored for a short distance. However, dangerous roof conditions and bad air made a full inspection of the mine impossible. This image is taken a short way in. Note the square timbering and copious amounts of ochre in places - it covered the floor, walls and roof. Ochre itself is however less toxic than the mine water with its loading of heavy metals - a classic case of the highly visible pollution being aesthetically displeasing while the apparently "clear" water is in fact the real rogue!

Repairing the adit portal lagging
The lagging on the level portal was replaced. Note that this was a temporary job designed to tackle an environmental emergency: we made it clear at the time that a longer-term solution must be found and implemented. However, the adit should not let in any more scree for a few tens of years.

Spreading powdered limestone on the ochre, Cwmrheidol mine
Here, one of the NRA excavators is spreading lorryloads of powdered limestone over the ochre pumped from the mine into the big lagoon. The ochre in turn was pumped onto a powdered limestone bed. This image also shows the rusty mine-tips.

Here the No 9 job is nearing completion. The words "Keep Out - bad air" were added to the mine door after this photo was taken. In front of the door are the remains of a mine-wagon which was found buried in shale and winched out of the way. The water was set to discharge via a pipe from this small settling lagoon.

Although we went home happy after completing this work, Nature was to have a nasty surprise for us, some distance away, which 6 months after this photo was taken was to transform the site's appearance once again.

NEXT: The Surge!