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The adits were the drainage channels or tunnels for pumping out the water accumulated by rain and spring seepage in order to keep the mine dry.
The left hand illustration shows how the underground adit from the Tolroy section crossed under the Leedstown road and surfaced in a field in Trelissick Farm, probably with a natural spring, and ran down the natural downhill contours of the land. Today it has a helping hand and is piped across the A30 trunk road under the pedestrian foot bridge. It meets the adit from the Mellanear section and together they flow downhill, down Water Lane, and across (but today under) Chenhalls Road and along side the road and out into the estuary.
The right hand illustration concentrates on the Mellanear section and shows how the water was pumped up from Gundry's Shaft and onto a wooden flume (aquaduct) and sent to a reservoir and prior to that a water wheel; with the overflow running through a tunnel and then joining the Tolroy waters in Water Lane.
When there is exceptional rainy weather then all these old adits spring to life and the photos taken in 2016 illustrate why the lane is called Water Lane and what it must have looked liked in its hey day.
This Thesis was written by Tom Swanson studying at the Camborne School of Mines as part of his B.Eng 3 Industrial Geology and it is acknowledge that this excerpt is taken from his research and remains his copyright.
Ryans Field is a 15 acre, RSPB managed field in the south east of Hayle Estuary, cut of from the estuary in the 1930's by construction of a causeway, isolating the field from tidal flooding in all but spring tides. A small stream in the north of the field drains Mellanear Mine, with concentrations of Zinc in the sediment reaching 7%, Copper 6 % , and Arsenic 1.5%, within a discreet plume.
The impact of mine waste on natural systems is severe, and Cornish estuaries are unfortunate enough to contain world class levels of contamination.
Ryans Field receives drainage primarily from the Hayle, and to a lesser extent, Canonstown catchment areas, which contain a total of 29 mines. Ryans field also receives drainage from a tributary off Mellanear river, running along Water Lane.
More recent misuse of the field came about when the RSPB ploughed the field in the early 1990's. Unknown to them at the time, they were in fact remobilising tonnes of mine waste, lying below the surface within laminated clay-silt beds. Ploughing would have broken up the dense, anoxic sediment, allowing oxidation of detrital contaminants, and increased mobility. The discreet plume of contamination in the north east corner of the field contains the highest levels of contamination. It is precisely positioned over the only part of the field which is undisturbed, and nearest to incoming sediment from the tailings from Mellanear Mine, connected to the field by a small stream called Water Lane, which runs parallel with the northern edge of the field.
The map was made in 1907 shows in the east of the map Mellanear Mine, with the shaded area to the west believed to be the tailings dump. The perimeter of the dump is defined by Water Lane, which runs due west, then north west, where it intercepts the north east tip of Ryans Field and runs along the fields perimeter, and into the Estuary.
Ryans Field will receive ongoing contamination from Mellanear Mine draining into the Water Lane stream, from the flooding of the field on spring high tides, and from leached contaminants from the dredged waste which extends to and upstream of Hayle River.
The following has been extracted from the Mining Report of 1987 when the land was being prepared for house building. Due acknowledgments are made to the author.
The land lies within the West Alfred Consols mining sett, with the West Wheal Alfred sett lying immediate to the south west. The local workings were known as Mellanear Mine. Records are fairly complete for the main and latter workings, but are very limited for the early surface and shallow workings along the lodes.
At the time of trenching; the site had been partially cleared of trees and scrub vegetation, with some of the surface fill and mine waste dumps partially removed. The main shaft dump to the south of the site remained, with some removal continuing.
Some interest centered on the north west boundary area of the site where a deep channel had been encountered with a firm natural base at 2.4 metres below the existing surface. This channel appeared to run further up slope and parallel to the western boundary hedge. The feature was traced in this direction and approximately half way along this boundary hedge the channel passed into a tunnel, with the portal approximately 24 metres from Water Lane. The arch of the portal was at 1.3 metres below the surface and a firm natural base had been found here at 3.4 metres below the surface. Although most of the tunnel was open and unobstructed a layer of blue grey clay slimes was present along the floor of the channel and tunnel. A visual inspection of the tunnel confirmed its trend and nature, and it appeared to continue further towards the north east and continue out of the small enclosure. Because this feature appeared to continue into the land area present under consideration, work was commenced in this section of land.
A short trench was excavated at right angles to the indicated trend of the tunnel and a large area of blocky earth back fill was immediately encountered. The back fill was fully excavated to a firm base and sides, and the extent and the nature of the feature soon became apparent. The feature was rectangular in shape and all four sides had been lined with shaped blocks of hard altered shale. The approximate dimensions of the feature, measuring from the inside of the faced walls, were 6.8 metres by 1.3 metres, with the original dimensions of the pit being approximately 8.0 metres by 2.1 metres. At the north east end of the pit the block facing wall was excavated out in order to confirm that no tunnel extended to the north east, When the blocks were removed it was clear the end wall was intact and with no tunnel stubs. However, down to 2.8 metres below surface, and from this level to the base of the pit (4.8 metres deep) a tunnel was present which was obviously that found in the enclosure to the south west.
It is evident that this pit had been originally excavated to house a water wheel, as the Ordnance Survey parcel 7729 ( the small enclosure in the northern corner of the large site) had been used as a water holding reservoir, and it is presumed that water was taken from this reservoir down to the water wheel by a surface or raised timber flume, the run off water being removed from the wheel through the tunnel, along the back filled channel and into the lower ground to the south west of Water Lane.
The reservoir was shown to have a thin covering of earthy surface fill with layered damp laminated grey green slime below. These slimes had obviously settled out of the reservoir water, probably after being pumped out of the mine.
The main mining feature within the land was the recorded Gundry's shaft within the main dump area. Because of the thick covering of mine waste fill present, it was decided to strip the superficial layers and use shallow slot trenching within the natural horizons in order to identify the shaft back fill. However, as the stripping commenced, a number of timbers were quickly uncovered, with thick vertical posts supporting outer wooden plank lining, within the higher layers of mine waste. These timbers, forming an approximate rectangular shape, were shaft supports, holding back the layers of mine waste on the sides that had been dumped as the shaft was being sunk. The back fill in the center of the shaft was excavated out and it became clear that as well as the planking supporting the surface fill dumps at the top of the shaft, all four inner sides of the shaft were also timber lined. The back fill was excavated to a depth of approximately 5.5 metres from the original ground surface and the timbering was still visible at this depth. The approximate dimensions of the shaft at the natural ground surface level were 4.0 metres, by 3.0 metres widening to 3.4 metres, measured outside the timber lining. There was no sign of a 'sollar' or platform, although one may possible be present at a slightly greater depth than excavated.
A moderately deep channel running about 19 metres approximately NNE – SSW parallel to Water Lane was excavated. The channel sides were deep and stone lined and the width from the inside was 1.5 metres and the depth was 2.2 metres, and back filled with assorted cobbles of mine waste. The nature of this channel cannot be ascertained.
In general the only disturbance to the natural ground profile of this whole Croft site involved several areas of old buildings foundations, an area of old flues or drains; several old timbers; all of which were considered to be surface related activities.