Contaminated Land Is Affecting Controlled Waters and Their Quality, and Where the Environment Agency Will Also Have Other Concerns Under Other Legislation
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APPENDIX 1 Geology and Mineral Resources South Gloucestershire extends from the Severn Estuary in the East to the Cotswolds to the west. Geologically the area is very varied, having representations of nearly every Geological System exposed at the surface, the exceptions being the Ordovician and Cretaceous. Generally the older Palaeozoic rocks are exposed in the centre of South Gloucestershire, with younger Mesozoic rocks to the east and north- east. More recent estuarine alluvial deposits cover the Lowlands adjacent to the Severn Estuary in the west. In landscape terms much of South Gloucestershire is anomalous in that the outcrops of older and harder Palaeozoic rocks do not form uplands but are characterised by low undulating terrain. This is because much of the area formed part of an ancient erosion surface which was reduced to a low relief before the deposition of the Mesozoic strata. It is therefore the younger rocks, most notably limestones of Jurassic age, which form the highest land of South Gloucestershire, that being the Cotswold escarpment to the east. - 88 - Figure 3 - Simplified Geology of South Gloucestershire showing sites of mineral extraction - 89 - The alluvial flatlands adjacent to the Severn Estuary are extensive and form a distinctly contrasting landscape to that of the central and eastern parts of South Gloucestershire. Flat pastures predominate, bounded by drainage ditches, known locally as ‘rhines’. Rarely does the land in this area rise above 6 metres AOD. Nearly all the rivers west of the Cotswold scarp flow into the Severn Estuary, whereas those which follow the dip slope to the east, other than the Bristol Avon which detours to the west, join the River Thames. The rock types of South Gloucestershire within each Geological System are set out below in chronological order, together with the quarrying operations they give rise to: Cambrian The oldest rocks of South Gloucestershire are represented by the Tremadoc series which are found in an inlier which extends north of Tortworth. These rocks are unworked and consist mostly of grey micaceous shales with interbeds of siltstone and very fine grained sandstones. Ordovician Missing. Silurian Mudstones, sandstones and some limestones of Silurian age are found in a number of small inliers in the Tortworth and Charfield areas. These small exposures are unworked. Devonian Continental red beds of the Old Red Sandstone occur in the Thornbury inlier and around the Coalpit Heath Syncline. Small quantities of sandstone have been worked in the past from the Upper Red Sandstone. Carboniferous Lower Consists predominantly of Carboniferous Limestones Carboniferous which form the most extensive outcrop of all the Palaeozoic rocks of South Gloucestershire. They outcrop on the northern rims of the Bristol Coalfield, north to Tortworth then south to Chipping Sodbury, and in isolated inliers at Wick and Codrington. The Carboniferous Limestone is nowadays by far the most important mineral resource in South Gloucestershire, being utilised for roadstone and construction aggregate. Active quarries are located at Tytherington, Chipping Sodbury, Wickwar and Wick. There is also a temporarily inactive site near Cromhall. Upper Formed in deltaic and swamp conditions these rocks can Carboniferous be split into two groups: (i) Quartzitic Sandstone – which outcrops on the northern and north-east rim of the Bristol Coalfield between Chipping Sodbury and Cromhall, and in the Wick inlier. Small quantities of sandstone are - 90 - extracted from the Cromhall Quartzite Quay at Cromhall. These rocks have skid resistant properties and are used as a top dressing in road surfacing; (ii) Coal Measures – which include the coal seams and the commonly occurring Pennant Sandstone are found south of Cromhall through Coalpit Heath to Kingswood in the Coalpit Heath Syncline and Kingswood Anticline. For over a hundred years coal was the most important extractive industry of South Gloucestershire. Centred on Kingswood, the Coalfield spread through South Bristol and north through Coalpit Heath to Yate. Coal mining reached its peak in Kingswood between 1870-1890. From the late 1950s the industry steadily declined due to the exhaustion of workable reserves and difficult geological conditions. The last working mine to close in South Gloucestershire was at Harry Stoke. Historically, there has been some small extraction of iron from Haematite lodes in fissured Pennant Sandstones around Iron Acton and Frampton Cotterell. At Wick, iron oxides known as ‘oxide’ or ‘ochre’ were worked from pockets in the Carboniferous Limestone. The Pennant Sandstone itself has been used locally for building stone and dry stone walling but, nowadays, its uses are limited and it is no longer extracted in South Gloucestershire. Coal Measure Clays are extracted for engineering bricks and pipes at Almondsbury and a similar clay pit is seasonally exploited at Shortwood. Permo- The Triassic rocks are mostly sandstones, mudstones and Triassic conglomerates which occur as thick sequences of terrestrial red beds which lie unconformably on deeply folded Permian rocks. The Triassic rocks are well seen in the classic exposures of Aust Cliff which is situated at the eastern end of the old Severn Bridge, and are widely exposed throughout the central area of South Gloucestershire. The mineral Celestite (Strontium Sulphate) is commonly found in the Triassic Keuper Marls of the area. For over 100 years this mineral was extracted from shallow pits situated mostly to the west of Yate. Although production ceased recently, the area was at one time the world’s leading producer of Celestite. - 91 - The Permo-Triassic rocks have only been locally used on a minor scale for building stone, or as bulk fill, such as on the Second Severn Crossing approach roads. Jurassic This period heralded a return to marine conditions. The early Jurassic rocks occur as a wide north/north-east trending belt in the east, forming predominantly low lying areas of heavy clay with some limestones and various mudstones, silts and sandstones. Later deposition formed the Inferior Oolite Group, thick sequences of shallow water marine limestones, which make up the bulk of the Cotswold escarpment in the east. The Blue Lias Limestone has been locally exploited on a small scale for building stone or hardcore. Similarly the Oolite Limestones can be seen in buildings and dry stone walls in the Cotswolds. Cretaceous Missing. Quaternary These beds consist of various unconsolidated sediments comprising alluvium, glacial deposits and head deposits. These are found predominantly in the west adjacent to the Severn Estuary. Until recently, estuarine alluvial clays were exploited for brick making at Crooks Marsh, Severnside. - 92 - Table 1 - Simplified Table of Geological Formations present in South Gloucestershire C A I N O QUATERNARY HOLOCENE Unconsolidated Sediments eg PLEISTOCENE Alluvium, Glacial deposits, head Z deposits O I C M UPPER JURASSIC Oxford Clays E S JURASSIC MIDDLE JURASSIC Bathstones and Inferior Oolite Limestones O Z LOWER JURASSIC Lias Clay O White and Blue Lias Limestones I TRIASSIC C PERMIAN Sandstones P UPPER Coal Measures including the A CARBONIFEROUS Pennant Sandstones L Quartzitic Sandstones A CARBONIFEROUS E LOWER Carboniferous Limestones and CARBONIFEROUS Cromhall Sandstone O Z DEVONIAN Old Red Sandstones O SILURIAN Mudstones and Sandstones I including the Tortworth and Thornbury beds. C CAMBRIAN TREMADOC Shales, siltstones and fine sandstones. - 93 - APPENDIX 2 Special Sites Water-Pollution Cases Regulations 2(1)(a) and 3 ensure that the Environment Agency becomes the enforcing authority in three types of case where the contaminated land is affecting controlled waters and their quality, and where the Environment Agency will also have other concerns under other legislation. These cases are set out in regulation 3, and are broadly as follows: (a) Wholesomeness of drinking water: Regulation 3(a) covers cases where contaminated land affects controlled waters used, or intended to be used, for the supply of drinking water. To meet the description, the waters must be affected by the land in such a way that a treatment process or a change in treatment process is needed in order for such water to satisfy wholesomeness requirements. The standards of wholesomeness are currently set out in the Water Supply (Water Quality) Regulations 1989 (S.I. 1989/1147 as amended by S.I. 1989/1384, S.I. 1991/1837 and S.I. 1999/1524), and the Private Water Supplies Regulations 1991 (S.I. 1991/2790). An intention to use water for the supply of drinking water would be demonstrated by the existence of a water abstraction licence for that purpose, or an application for such a licence. (b) Surface-water classification criteria; Regulation 3(b) covers cases where controlled waters are being affected so that those waters do not meet or are not likely to meet relevant surface water criteria. These are currently set out in four sets of Surface Waters (Dangerous Substances) (Classification) Regulations: S.I. 1989/2286, S.I. 1992/337, S.I. 1997/2560 and S.I. 1998/389). (c) Major aquifers: Regulation 3(c) covers cases where particularly difficult pollutants are affecting major aquifers. The Environment Agency will already be concerned both with pollutants of this type and with managing water resources. The list of pollutants is set out in paragraph 1 of Schedule 1. It corresponds to List I of the Groundwater Directive (80/86/EEC). The major aquifers are described in paragraph 2 of Schedule 1 by reference to the underground strata in which they are contained. The British Geological Survey publishes maps which show the location and boundaries of such strata. For the purposes of regulation 3(c), the fact that contaminated land may be located over one of the listed underground strata does not by itself make the land a special site. The land must be contaminated land on the basis that it is causing, or is likely to cause, pollution of controlled waters; the pollution must be by reason of one or more substances from schedule 1; and the waters being or likely to be polluted must be contained within the strata.