Land Reclamation and River Pollution Problems in the Croal Valley Caused by Waste from Chromate Manufacture

Chromate salts were manufactured at the Hall Chemical Works, Little Lever, near Bolton, from 1880 until 1968. All that now remains on the site is the derelict works and two heaps of waste from the process. They are up to 15 m high, and consist of several hundred thousand tonnes of material. Most of the 15-ha site is devoid of vegetation and it is a conspicuous feature of the landscape of the Croal Valley. Reclamation of the site would greatly improve the amenity of the district. It would also mitigate river pollution, for at present, rain water drains into the nearby river Croal and carries with it 3-5 t of soluble chromium every year. This effluent water has a severe effect upon the river flora. Table 1 shows the algal and macrophyte flora upstream from the effluent, as well as 200 m and 1P5 km downstream. Even 1 5 km downstream, the flora shows little sign of recovery, and there was no detectable decrease in the concentration of chromium in the river water, which varied between 0-2 and 0 5 mg Cr/l. A grass cover on the waste heaps would return half of the rain water back to the atmosphere by evapotranspiration (Ministry of Agriculture 1962) and so reduce the volume of effluent water. Two other factors would influence the amount of chromium entering the river: the degree of saturation of chromium in the effluent and the area of the heaps after they have been flattened. Reclamation schemes have been proposed by the Lancashire County Council not only to alter the unsightly waste heaps but to improve the condition of the river Croal. Part of this work was carried out as a preliminary study of these schemes.