368 Influence of Mines upon Land and Livestocic 



which accuamlates in the "slime" or "catch"' pits. Even with the most 

 careful management and the employment of modern machinery some 

 of the ore finds its way into these waste heaps. In the case of some mines, 

 however, it is found that the waste heaj^s contain appreciable quan- 

 tities of ore-laden matter. At the present time some of them are found 

 to contain enough ore to make further extraction profitable. 



In the fresh heaps the lead is usually present as sulphide and the 

 clean drainage water from them is found to be practically free from lead. 

 After the heaps ha\e been exposed'to the action of air and water for 

 some years, however, it is found that the drainage water from them is 

 impregnated with lead and other metalliferous substances. A sample 

 of soil from a field near Talybont, contaminated with surface water from 

 the wastes of a disused mine, w^as found to contain -11 \>ev cent, of lead. 



2. Sand, and more particularly slime, are blown from the heaps 

 by the dry east winds. Fields situated on the western sides of the mine 

 heaps are almost invariably affected in this way, in some cases, e.g. at 

 Cwmsymlog, for a distance of at least a mile. This effect is readily 

 perceived when there is a strong east wind and the ground is covered 

 with a layer of snow. 



The following are results of analyses of soil samples taken on the 

 western and eastern sides of mine refuse heaps. The samples were taken 

 on land which as far as could be observed had been contaminated by 

 wind action only. 



Mynydd Gorddu Mine. Cwmsymlog Mine. 



Sample from Sample from 



(a) West side (h) East side (a) West side (i) East side 



Lead -08 % Lead-trace Lead 0-9 % Lead, nil 



3. Where mine wastes have been utihsed to construct and repair 

 roadways, some of the material may, in course of time, be washed over 

 the adjoining land especially where the roads are not protected by a 

 bank or ditch. 



A striking example of this effect is to be seen at a farm near Brynarian 

 Mine. The roadway leading up to the farm goes through the centre of a 

 field situated on a slope. Above the roadway the soil is fertile and free 

 from toxic substances. On the lower side of the road there is a strip of 

 land ranging in width from 10 to 20 yards where the vegetation presents 

 the usual appearance of that growing on lead poisoned soils. 

 Analvsis of soil samples showed 



(a) Soil above road to be free from lead. 



(h) Soil below road to contain -12 per cent, of lead. 



