BS ISO 5667-18:2001 pdf – Water quality — Sampling — Part 18: Guidance on sampling of groundwater at contaminated sites.
1 Scope This part of ISO 5667 provides guidance on the sampling of groundwater at potentially contaminated sites. It is applicable to situations where contamination of the subsurface could exist as a result of downward migration of pollutants whose source is at the surface or just below it, and when the guidance provided in ISO 5667-1 1 is inappropriate. 2 Terms and definitions For the purposes of this part of ISO 5667, the following terms and definitions apply. 2.1 piezometer device consisting of a tube or pipe with a porous element or perforated section (surrounded by a filter) on the lower part (piezometer tip), that is installed and sealed into the ground at an appropriate level within the saturated zone for the purposes of water level measurement, hydraulic pressure measurement and/or groundwater sampling 2.2 nested piezometers group of piezometers installed within a single larger-diameter borehole NOTE In general, each piezometer should be designed to allow sampling over a specific depth interval within the aquifer. Piezometer tips are isolated from each other by installing a permanent impermeable seal between them. 2.3 multiple boreholes group of individual boreholes or piezometers installed separately to form a monitoring network adequate for the purposes of an investigation 2.4 multi-level sampler single installation for sampling groundwater from discrete depths within the sub-surface NOTE The device can be driven directly into the ground, installed in a pre-existing borehole or installed in a purpose-drilled hole. When installed in a borehole, integral packers are used to isolate individual sample ports. 2.5 aquifer geological formation (bed or stratum) of permeable rock or unconsolidated material (e.g. sand and gravels) capable of yielding significant quantities of water 2.6 aquitard geologic stratum of formation of low permeability that impedes the flow of water between two aquifers
2.7 saturated zone part of an aquifer in which the pore spaces of the formation are completely water-saturated 2.8 unsaturated zone part of an aquifer in which the pore spaces of the formation are not totally water-saturated 2.9 groundwater water in the saturated zone and/or unsaturated zone of an underground geological formation or artificial deposit such as made ground 2.10 perched water table isolated body of groundwater, which is limited in lateral and vertical extent, located within the unsaturated zone overlying a much more extensive groundwater body 2.11 matrix potential combination of forces, independent of gravity, acting on soil water (water contained within the pores of a soil/rock matrix) that exist as a result of the attraction of solid surfaces to water and the attraction of water molecules to each other NOTE Generally, the smaller the particle size, the higher the matrix potential. 2.12 check valve mechanical valve which allows fluids to pass in only one direction NOTE The pressure of fluids flowing through the valve in one direction has the effect of opening the valve and in the other of closing it. 2.13 receptor entity that is vulnerable to the adverse effect(s) of a hazardous substance or agent EXAMPLES Human, animal, water, vegetation, building services, etc. 2.14 packer device or material for temporarily isolating specified vertical sections within boreholes in which to perform groundwater sampling from discrete zones or locations within the borehole or aquifer 2.15 hydraulic conductivity property of a water-bearing formation that relates to its capacity to transmit water through its internal, interconnected pathways 2.16 effective porosity proportion of saturated openings or pores within a water-bearing formation which contribute directly to the flow of groundwater NOTE Effective porosity is represented as the ratio of this volume of pore space to the total volume of rock.
3 Sampling strategy and programme design 3.1 General Groundwater sampling can be carried out as a single exercise or as part of a larger site or environmental investigation. Regardless of the purpose, a rational approach should be taken that clearly defines the objectives, determines the level of information needed and identifies the various stages of the investigation. It should be noted that, normally, groundwater sampling from the saturated zone alone cannot fully assess the level of contamination of a site in situations where an unsaturated zone of considerable thickness exists. The potential consequence of ignoring the unsaturated zone is that the unsaturated zone and groundwater system could become extensively contaminated before any tangible evidence of leakage or contamination is evident in samples collected from below the water table.