OR/14/043 Site description - Foel Fawr Sites 1 and 2, Brest Rhiw and Moel Gornach
| Farr, G, Graham, J, and Stratford, C. 2014. Survey, characterisation and condition assessment of Palustriella dominated springs 'H7220 Petrifying springs with tufa formation (Cratoneurion)' in Wales. British Geological Survey Internal Report, OR/14/043. |
Foel Fawr Sites 1 and 2, Brest Rhiw and Moel Gornach
Introduction
Foel Fawr, including Herbert’s Quarry, is located north of Brynamman (SN7313319125) on land owned by the Brecon Beacons National Park (BBNP). The area has been designated as a SSSI (Mynydd Ddu) for its geological interest and it is also located within the Fforest Fawr Geopark area. Herbert’s quarry is a post industrial Site that has been quarried extensively for lime and agricultural quick lime since pre-industrial times and increased in the 19th century to supply demand for lime flux in iron production (Andrews et al., 1997[1]). The high pH waters (recorded up to pH 12.2 in this study) can be considered hyperalkaline and are the result of dissolution of lime spoil (Andrews et al., 1997[1]). Foel Fawr Sites 1 and 2 and Brest Rhiw are all located within close proximity of the lime spoil and have thus been included together, where as Moel Gornach acts as a natural comparison being located away from the historic mining area and spoil. There is significant tufa deposition at Foel Fawr Sites 1 and 2 and Brest Rhiw with limited more localised tufa deposition at Moel Gornach.
Geological and hydrogeological data
The main historic quarrying operations are concentrated within the Carboniferous Dowlais Limestone Formation with large areas of unconsolidated lime spoil deposited on the northern flank of Foel Fawr and elsewhere below the main quarries. Recharge occurs from precipitation on the topographically higher ground above the lime spoil. Springs and seepages occur at the base of the lime spoil and also at or near where the Carboniferous Limestone contacts with the Avon Group (lower limestone shales). It is below the area of lime spoil where the tufa deposits are more concentrated and they are strongly associated with the historic dumping of lime waste in the area. Surface water flows to the north via several small unnamed streams and the Cwm Nant-dywyll, all which cut down into the underlying Devonian Old Red Sandstone before joining the Afon Clydach.
Foel Fawr Site 1: two water quality samples were obtained, FF1.1 ‘downstream’ and FF1.6 ‘upstream’. Both samples are dominated by calcium and bicarbonate ions, however the ion balance for both samples was over the recommended 10% limit. Neither sample contained elevated nutrients in the form of nitrate and phosphate. The most notable changes, possibly related to the deposition of CaCO3 and associated ions from solution as tufa between the upsteam sample (location 6) and the downstream sample (FF1.1) are the reduction in the following:
Hardness (as CaCO3 mg/l) from 1490 mg/l to 183 mg/l Calcium from 594 mg/l to 71.7 mg/l
Magnesium from 360 to 32.9 μg/l Manganese from 360 -32.9 μg/l and Iron from 1910 to 32.9 μg/l
pH readings in the field range from 11.42 pH (location 8) at the top of the Site near the inflow and become less alkaline as you walk down through the Site to 8.22 pH (location 9).
Foel Fawr Site 2: four water quality samples were obtained from Sites FF2.1, FF2.2, FF2.3 and FF2.4. All samples were dominated by calcium and bicarbonate ions, however the ionic balance for sample FF2.4 was over the recommended 10% limit. All four samples contained very little evidence of nutrient enrichment, with most samples below the limit of detection for nitrate and phosphate. The waters at the base of the spoil (Sites FF2.1) had a pH value of 12.2.
Brest Rhiw: one complete sample and one nutrient only sample were collected at Brest Rhiw, like the samples at Foel Fawr Sites 1 and 2 calcium and bicarbonate are the dominant ions and there is only a small amount (1.64 mg/l NH4), with a more neutral pH value of 7.32.
Moel Gornach: two samples were obtained from Sites MG1.3 (top of the Site) and MG1.1 (towards the base of the Site). Unlike Foel Fawr 1 and 2 and Brest Rhiw there is no lime spoil in the area of Moel Gornach and there is also less tufa deposition, with only a very small amount observed forming near the spring head. Both samples were dominated by calcium and bicarbonate ions and both have pH values >8. The upland setting and low intensity land use is reflected by the low level of nutrients within both samples, many below or close to the lower limits of detection.
Land use and pressures
Foel Fawr (Sites 1 and 2) are located near a car park, main road and footpath into Herberts Quarry, and as a result there was some localised littering but no evidence of damage from walking or disruption of the Site. The land surrounding the Site is sheep and horse grazed. There is no evidence of substantial poaching, burning or obvious signs of nutrient enrichment at any part of the Site. It is unlikely that there are any groundwater or surface water abstractions in the immediate area. The Site could receive runoff from the adjacent road and there is a possible road drain in the southwest corner of the Site. Significant negative indicator species such as Agrostis stolonifera display <1% cover.
Brest Rhiw is located adjacent to the main road and has similar issues to Foel Fawr, in that the land is open for walkers and grazing animals although there was no sign of substantial poaching, burning or nutrient enrichment.
Moel Gornach is located further away from the main road and receives less footfall from walkers. The area is open for grazing although there was no sign of substantial poaching, burning or nutrient enrichment.
© Ordnance Survey.
Vegetation (spring)
Palustriella falcata dominated short vegetation (between 1–3 cm height) with Scorpidium cossonii locally dominating margins of runnels (or hollows where there is movement of water). Cushions of Hymenostylium recurvirostrum and locally Eucladium verticillatum are associated with exposed tufa. Pinguicula vulgaris occurs in one place.
| Agrostis stolonifera | R (<1%) |
| Aneura pinguis | F |
| Bellis perennis | O |
| Bryum dichotomum | R |
| Bryum pseudotriquetrum | O |
| Calliergonella cuspidata | R |
| Campylium protensum | R |
| Campylium stellatum | F |
| Cardamine pratensis | R |
| Carex demissa | O |
| Carex flacca | F |
| Carex nigra | R (<1%) |
| Cirsium palustre | R |
| Climacium dendroides | R (<1%) |
| Cratoneuron filicinum | O |
| Ctenidium molluscum | R (<1%) |
| Didymodon fallax | R (<1%) |
| Eucladium verticillatum | O |
| Festuca ovina | R (<1%) |
| filamentous algae (Chlorophyta) | R |
| Fissidens adianthoides | O |
| Hymenostylium recurvirostrum | F |
| Juncus acutiflorus | F |
| Juncus effusus | R (<1%) |
| Jungermannia atrovirens (per.) | A |
| Leicolea badensis | F |
| Nostoc sp. | R |
| Palustriella commutata | O |
| Palustriella falcata | A |
| Philonotis calcarea | F |
| Philonotis fontana | R |
| Pinguicula vulgaris | R |
| Plantago lanceolata | R |
| Pressia quadrata | R |
| Prunella vulgaris | R |
| Ranunculus acris | R (<1%) |
| Ranunculus flammula | R |
| Riccardia multifida | R (<1%) |
| Sagina cf nodosa | O |
| Scorpidium cossonii | O |
| Scorzoneroides autumnalis | R |
| Taraxacum sp. | R (<1%) |
Mainly calcareous rocks and older tufa deposits within the area of flush/spring but above the level of seepage water supporting a small number of acrocarpous calcareous bryophyte species.
| Didymodon rigidulus | O |
| Ditrichum gracile | R (<1%) |
| Fissidens dubius | R (<1%) |
Vegetation (adjoining spring)
Upland acid grassland to 25 cm height (Nardus stricta, Hylocomium splendens, Dicranum scoparium, Galium saxatile, Potentilla erecta, Rhytidiadelphus squarrosus, occasional Vaccinium myrtillus).
| Hylocomium splendens | F |
| Dicranum scoparium | O |
| Nardus stricta | A |
| Galium saxatile | O |
| Potentilla erecta | R |
| Vaccinium myrtillus | R |
| Scleropodium purum | R |
| Juncus effusus | R (<1%) |
Short sheep and horse grazed calcareous grassland (to 5 cm height) dominated by Ctenidium molluscum on old mining spoil.
| Agrostis stolonifera | O |
| Bellis perennis | R |
| Ctenidium molluscum | A |
| Cynosurus cristatus | O |
| Plantago lanceolata | O |
| Rhytidiadelphus squarrosus | R |
| Thymus polytrichus | R (<1%) |
| Trifolium repens | O |
© Ordnance Survey.
© UKP/Getmapping Licence No. UKP2006/01.
Vegetation (spring) of Foel Fawr Site 2
Palustriella falcata dominated short vegetation between 1–3 cm height with Scorpidium cossonii locally dominating margins of runnels (or hollows where there is movement of water). Cushions of Hymenostylium recurvirostrum and locally Eucladium verticillatum, Gymnostomum aeruginosum are associated with exposed tufa. Scorpidium scorpioides occurs locally.
| Agrostis stolonifera | R (<1%) |
| Anagallis tenella | R |
| Aneura pinguis | F |
| Bellis perennis | R |
| Bryum dichotomum | R |
| Bryum pseudotriquetrum | O |
| Calliergonella cuspidata | O |
| Campylium stellatum | O |
| Cardamine pratensis | O |
| Carex demissa | F |
| Carex flacca | F |
| Carex nigra | R (<1%) |
| Cirsium palustre | R |
| Climacium dendroides | R (<1%) |
| Cratoneuron filicinum | F |
| Ctenidium molluscum | R (<1%) |
| Dicranella varia (spor.) | O |
| Equisetum cf variegatum | R (<1%) |
| Eucladium verticillatum | R |
| Festuca ovina | R |
| Ficaria verna | O |
| filamentous algae (Chlorophyta) | O |
| Fissidens adianthoides | O |
| Galium palustre ssp. palustre | O |
| Gymnostomum aeruginosum | O |
| Hymenostylium recurvirostrum | F |
| Juncus acutiflorus | F |
| Juncus effusus | O |
| Jungermannia atrovirens | A |
| Leicolea badensis | O |
| Leicolea bantriensis | R |
| Moerckia flotoviana | R |
| Nostoc sp. | O |
| Palustriella commutata | O |
| Palustriella falcata | D |
| Pellia endiviifolia | R |
| Philonotis calcarea | F |
| Philonotis fontana | O |
| Pinguicula vulgaris | R |
| Plagiomnium ellipticum (non fertile) | R |
| Plantago lanceolata | R |
| Pressia quadrata | O |
| Prunella vulgaris | R |
| Ranunculus acris | R (<1%) |
| Ranunculus flammula | R |
| Riccardia multifida | R |
| Rivularia haematites | R |
| Scorpidium cossonii | O |
| Scorpidium scorpioides | R |
| Scorzoneroides autumnalis | R |
| Taraxacum sp. | R |
| Trifolium repens | R (<1%) |
| Tussilago farfara | R (<1%) |
Mainly calcareous rocks and older tufa deposits within the area of flush/spring but above the level of seepage water supporting a small number of acrocarpous calcareous bryophyte species.
| Ditrichum gracile | R (<1%) |
| Fissidens dubius | R (<1%) |
| Schistidium sp. | R |
Vegetation (adjoining spring) of Foel Fawr Site 2
Upland acid grassland to 25 cm height (Nardus stricta, Hylocomium splendens, Dicranum scoparium, Galium saxatile, Potentilla erecta, occasional Vaccinium myrtillus). Ocassional small hummocks occur comprised of Aulocomnium palustre, Sphagnum subnitens or Polytrichum commune.
| Aulocomnium palustre | R |
| Dicranum scoparium | O |
| Galium saxatile | O |
| Hylocomium splendens | O |
| Hypnum jutlandicum | O |
| Juncus effusus | O |
| Juncus squarrosus | R |
| Nardus stricta | F |
| Pleurozium schreberi | R |
| Polytrichum commune | R |
| Potentilla erecta | R |
| Sphagnum subnitens | R |
| Vaccinium myrtillus | R |
Short sheep and horse grazed calcareous grassland (to 5 cm height) dominated by Ctenidium molluscum with occasional Thymus on old mining spoil.
| Agrostis stolonifera | O |
| Bellis perennis | R |
| Ctenidium molluscum | A |
| Cynosurus cristatus | O |
| Plantago lanceolata | R |
| Prunella vulgaris | R |
| Rhytidiadelphus squarrosus | R |
| Scorzoneroides autumnalis | R |
| Thymus polytrichus | R (<1%) |
| Trifolium repens | R (<1%) |
Condition assessment
The overall assessment is that Foel Fawr (Sites 1 and 2) should be classified as as being in favourable ecological and hydrogeological condition.