Translation of Issue 48 pages 31-35 Troad  y rhod

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Coming full circle – restoration of the Tan y Bwlch turbine and the environmental considerations

Hydro-electric schemes aren’t new to Snowdonia. Here, TWM ELIAS recalls the history of such schemes and in particular discusses the turbine which recently received its official opening in the grounds of Plas Tan y Bwlch this year – the third such scheme at the Plas. He also describes the ecological considerations which were fundamental to the project’s success.

The history of electricity in Snowdonia
The 13th of June, 2013, was an important day in the history of Plas Tan y Bwlch, the Snowdonia National Park Centre, as the latest hydro-electric scheme at the Plas was officially opened. This is the third such scheme since the first small scheme was established in 1884, when the Plas was among the first houses in Wales to have its own private electricity supply.

The use of such power was very much a newfangled idea at the end of the 19th century, with technology developing at a rapid pace. Turbines were already driving agricultural machinery in Hafod y Llan, Nant Gwynant, and innovative engineers and industrialists in Snowdonia’s slate industry soon exploited this new potential, e.g. to drive machinery in Llechwedd Quarry in 1891 and, in 1899, to pump water from the lower levels of Croesor Quarry in the depths of the Moelwyn Mawr to light the underground chambers there(1). As the area is blessed with high and consistent rainfall throughout the year, surely it makes sense to convert the clouds’ gift into ‘turbine fuel’?

In the first decade of the 20th century three significant hydro-electric schemes were established in Snowdonia – Dolwen near Blaenau Ffestiniog (1902) and Cwm Dyli on the slopes of Snowdon (1906), to service the area’s slate quarries; and Dolgarrog (1907) for the aluminium works there. The North Wales Power Co. network also distributed power to supply industry, private dwellings and street lightning to a number of nearby towns. (2)

In 1904 the second electricity scheme in the Plas was established. It was larger and took water from the reservoir in Nant y Felin on the Plas’s land, with the turbine house located down by the highway (A487), to supply electricity to the flour mill, saw mill and other machinery on the Estate’s Home Farm.

Small electricity schemes were in vogue over the next few decades, and the Edwards company from Llanuwchllyn installed hundreds of them, predominantly on farms, in mills and in some villages throughout north Wales from 1910 onwards. During their heyday, in the 1920s-30s, Wales and the Lake District in the north of England were leading the way in Europe in terms of developing hydro-electric schemes. Then, due to the need to reconcile power and increase the strength of the supply, most of the small schemes were gradually abandoned towards the end of the 1930s with the expansion of the electricity distribution network, e.g. the turbine installed in the Plas in 1904 was operational until 1936 before it was decided to connect to a stronger supply from the North Wales Power Co. network, which had opened the Maentwrog Power Station on the other side of the Valley in 1927.

Electricity consumption grew rapidly after that, revolutionising the lives of the majority of people by the mid-20th century. The industry was nationalised in 1957 under the Central Electricity Generation Board (CEGB) before it was disbanded and privatised in the mid-1990s(3).

A renewed interest in hydro-electricity
Over the last few years, in light of increasing energy costs and the global need to reduce carbon emissions, there has been a renewed interest in generating electricity through ‘green’ and sustainable methods. Hydro-electric schemes are a most acceptable means of achieving this, especially in a mountainous and wet area such as Snowdonia National Park, where the environmental and landscape impact can be minimal. From the mid-1990s until 2011, seven small hydro-electricity schemes in the Park were given planning permission, but there has been a significant increase subsequently and a further 30 had been given permission by mid 2013(4).

Work began in 2006 to explore the appropriateness of reinstating a turbine in the grounds of Plas Tan y Bwlch, and how to do so in a way that would epitomise good practice for others to emulate. Snowdonia National Park has a policy to permit small electricity schemes, on suitable sites, which have minimal impact on the landscape and the environment. In this case no insurmountable problems were foreseen with the scheme from a planning perspective: it would use the original dam from previous schemes; the pipeline would run underground for most of its length; and the small turbine house would be carefully landscaped. There was much more to consider in terms of its environmental impact.

Protected site
Laying a pipeline from the original dam of Llyn y Felin through the Plas’s woodland, which is part of Coedydd Maentwrog Special Area of Conservation (SAC), to a new turbine house 59m lower down the slope near the highway (A487) was challenging. The pipeline would have to follow a route through mature woodland on the slopes of a ravine that has been included in the SAC based on the community of trees and plants, such as mosses etc, found here, and its use by various species of bats.

Before progressing, a series of reports were commissioned as part of the statutory Environmental Impact Assessment required for such a scheme. The assessment’s outcomes would dictate the fate of the scheme first and foremost and it would include recommendations on any additional mitigating measures needed to minimise the damage to protected plants and animals here.

In 2009, a botanical report was commissioned including a National Vegetation Classification (NVC) survey and a Bryological assessment of the ravine and woodland surrounding the pipeline’s proposed route. A report and survey on mammals and birds was produced in 2010 and a tree survey, including a report on the work’s potential impact on them, was produced in 2012. Based on the findings, a scheme of work was drafted with firm operational guidelines to be followed by contractors and the officers from the Park’s Ecology and Woodland departments, who would be supervising the work from day to day.

The key considerations
The NVC survey showed that the pipeline would traverse, or would be likely to affect, seven different semi-natural communities of plants including: a mixed oak woodland (mainly W10e and W17) interspersed with some ancient pine trees at the upper levels; a decorative row of lime trees (Tilia) at a lower level; and grassland (MG10a) in the apple tree orchard above the turbine house.

The high-level plants in the woodland were of relatively little botanical interest as they were covered by a thick blanket of Rhododendron ponticum until the mid-1970s, and some areas remain under the heavy shade of non-native trees and beech trees whose leaves rot slowly. This contributed to the soil’s acidity, which is already on the acidic rocks of Maentwrog. The main source of interest is the low plants – ferns, bryophytes and lichen. For example, the 2009 survey identified 83 bryophytes (56 mosses and 27 liverworts) which may not be a high number, perhaps, but contains some species of special interest in nine sites – mainly on tree trunks. Protecting those trees was a priority.

Avoidance and mitigating measures
Some of the plants to be protected were:
Fern – Hay-scented buckler-fern (Dryopteris aemula) in Nant y Felin ravine. A decision was made that the pipeline should avoid the ravine, so as not to disturb the soil on the slopes.
Liverwort – rare species: Plagiochila punctata and P. killarniensis on tree trunks near the river and Fissidens curnovii on stones in the river. The main risk to them would be if diverting water through the pipe reduced the river flow and therefore moisture in the ravine. To avoid this, a water splitter was placed by the dam to prevent the extraction of water during shortages.
Lichen – three types of the Lobarion community (Lobaria pulmonaria, L. virens and Sticta fuliginosa) were found, mainly on mature trees. To avoid damaging these trees and their roots, the pipeline’s route was chosen carefully and there were thorough consultations with the contractors undertaking the work.
Mosses – Knowing the location of rare species, e.g. Leucobryum juniperoideum, it was relatively easy to avoid them.
Individual trees – protecting the mature trees in the upper section of the site was synonymous with protecting what grew on them. Care was taken not to damage the trunks or the roots – whether directly while digging the trench for the pipeline or by compacting the soil under the wheels of machinery and impairing drainage.

These problems were overcome by choosing the route carefully and laying the pipe on the surface of the ground when it couldn’t be buried easily without damaging the trees’ principal roots, and covering it with geotextile to encourage mosses etc. to grow over it in time. Planks were laid on the ground under the wheels of machinery when they needed to work on the woodland floor and, when digging the trench to bury the pipe (at least 500mm deep), close supervision was ensured to avoid cutting through roots thicker than 25mm and to lay the pipe underneath them if possible. Particular care was taken when the trench was being opened between the large lime trees above the orchard.

Other wildlife – one feature of the woodland’s SAC is its interest in terms of bats. Some species roost in the ancient trees and no work could be undertaken near one culvert where lesser horseshoe bats hibernate between November and February. Construction of the turbine house included three voids with access for bats.  Other considerations included not working during birds’ nesting season; ensuring that neither the shelters or resting places used by the area’s otters were disturbed; and carefully choosing the pipeline’s route through the orchard to the turbine house to avoid ant hills in the grass and marking them so machine drivers could avoid them when opening the trench. They had to be prepared for the unexpected too – such as the instance when the author had to rescue a grass snake which had fallen into the trench!

Twm Elias is a lecturer and course organiser at Plas Tan y Bwlch, Snowdonia National Park Study Centre.

1) Hydro-Electricity in North West Wales, Dewi W Thomas (1997), pg. 27
2) Ibid., pg. 39 – 86
4) Planning Department, Snowdonia National Park Authority