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The Influence of Unlined Boreholes on Groundwater Chemistry: A Comparative Study Using Pore‐Water Extraction and Packer Sampling
Author(s) -
PRICE M.,
WILLIAMS ANN
Publication year - 1993
Publication title -
water and environment journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 37
eISSN - 1747-6593
pISSN - 1747-6585
DOI - 10.1111/j.1747-6593.1993.tb00899.x
Subject(s) - borehole , aquifer , geology , drilling , groundwater flow , groundwater , petroleum engineering , extraction (chemistry) , hydrology (agriculture) , drilling fluid , geotechnical engineering , engineering , mechanical engineering , chemistry , chromatography
Abstract In the consolidated formations which form most of the major aquifers in the UK, many monitoring boreholes are left unlined (open) for their effective length. They therefore provide pathways for groundwater to flow from one part of the aquifer to another. A borehole was core‐drilled through Triassic sandstones into Permian mudstones at a site in North Yorkshire. Pore water was extracted from the core and compared with conventional depth samples and with samples taken from intervals isolated using packer systems: (a) during drilling, (b) about one month after drilling, and (c) two years after drilling. The study revealed that natural flow down the borehole led to rapid changes in the quality of water in some parts of the formation. The implication is that open boreholes can act as conduits to allow flow to take place from one part of the aquifer to another. They are therefore not reliable as sampling points, and may actually accelerate the vertical spread of pollutants. However, this last effect should not be over‐stated; in this study, the flow down the borehole was equivalent to the natural flow through only a relatively small area of land.