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Dam to SW of former Felin Fawr Slate Works

A Grade II Listed Building in Llandygai, Gwynedd

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Latitude: 53.1748 / 53°10'29"N

Longitude: -4.0749 / 4°4'29"W

OS Eastings: 261418

OS Northings: 366194

OS Grid: SH614661

Mapcode National: GBR 5S.3SR6

Mapcode Global: WH54G.CGTH

Entry Name: Dam to SW of former Felin Fawr Slate Works

Listing Date: 26 July 2001

Last Amended: 26 July 2001

Grade: II

Source: Cadw

Source ID: 25606

Building Class: Industrial

Location: The dam is the upper of two once-similar structures across the Galedffrwd, retaining a reservoir to the NW of the lane leading to Mynydd Llandegai, SW of the former slate works.

County: Gwynedd

Community: Llandygai (Llandyg√°i)

Community: Llandygai

Locality: Coed y parc

Traditional County: Caernarfonshire

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The Felin Fawr Slate Works complex was established at the beginning of the C19, serving the Penrhyn Slate Quarry - an early example of an industrialised slate sawing and dressing site relying on water power. The earliest surviving water-power system at the site (comprising a pair of dams forming a reservoir on the Galedffrwd, and a water wheel) appears to date from 1846-1848, associated with an early campaign of improvement on this key site. The lower of the two dams has been altered in recent years, but the upper dam remains virtually intact. The resultant reservoirs ultimately provided the water to operate both water wheels on site, together with a later turbine.


High dam wall constructed from massive slate blocks. The wall is roughly coursed and slightly battered, built on a slight curve across the valley floor. Two cast-iron sluices, and a brick-lined spillway in the centre of the dam wall. From the base of the dam, are the remains of 4 cast-iron pipes partially supported on a stone causeway, which formerly took water downstream to various areas of the slate works site.

Reasons for Listing

Listed as a fine mid-C19 masonry dam, an important component in the exceptionally complete surviving water-powered slate works at Felin Fawr.

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