AGS Guide to Environmental Sampling

AGS Guide to Environmental Sampling- 2010 1

AGS Guide to Environmental Sampling

Association of Geotechnical and Geoenvironmental Specialists, 2007. All rights reserved No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior permission of the Association of Geotechnical and Geoenvironmental Specialists. The document is not intended to be exhaustive. Although every effort has been made to check the accuracy of the information and validity of the guidance given in this Guide, neither the members of the Working Party nor the Association of Geotechnical and Geoenvironmental Specialists shall be held liable for any loss, damage or claim of any kind sustained by any person or organisation as a result of the contents of this document or anything contained herein. All brand names, trademarks, and registered trademarks are the property of their respective owners.

AGS Guide to Environmental Sampling- 2010

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1 Purpose This document is intended to provide practical guidance on the mechanics of the environmental sampling of soils, liquids and gasses in order to improve consistency in approach across the industry and summarise current best industry practice on:

The mechanics of sampling differing media, The avoidance of cross contamination, The use of blank, duplicate and trip samples, Suitability of sample containers, transport and recording.

The methodology of what, where and how often to sample will be dictated by the conceptual site model, the purpose of the investigation and the actual site conditions. These concepts are dealt with in other industry, BSI and regulatory guidance documents that should be referenced prior to undertaking any environmental sampling. 2 Introduction All sites are unique and hence the precise equipment required to undertake the investigation and sampling, as well as the associated health and safety requirements, will therefore vary. The following is an outline guide as to those issues that will influence the environmental sampling process. 3 Health and Safety Since all sites are unique it is vital that an appropriate Health and Safety risk assessment is undertaken prior to works being undertaken. This is to ensure that any potential for harm to site operatives and adjacent receptors resulting from the site works is identified and is reduced to a minimum by the establishment of safe working practices and methods. By the same reasoning, the potential to create environmental harm and the potential for cross contamination throughout the proposed works should also be assessed prior to the works being undertaken and measures put in place to minimize that risk. 4 Sample Containers Each laboratory may have specific requirements for sample containers for particular determinands. It is general good practice to provide samples in the form and amount required by the laboratory. Failure to do so may not allow testing and analysis to be undertaken to the standards, certification, tolerance or limits of detection required. Table 1 shows the appropriateness or otherwise of the most commonly used sampling containers for various media and determinands. A certain minimum amount of material is required for testing for a given determinand and a matrix of the typical amounts is enclosed as Table 2. However, reference should always be made to the requirements of the laboratory in each case and to the nature of the material being sampled.


5 Investigation and Soil Sampling

It is important to consider the contaminants likely to be encountered when selecting appropriate investigation and sampling techniques, to avoid loss or alteration of the contaminant being investigated. In order to collect a representative VOC (Volatile Organic Compound) sample for example, the least amount of disturbance and contact with the atmosphere is required and hence cable percussive or rotary drilling methods are not generally appropriate. Ideally such samples should be collected in lined windowless samplers or similar. It should be noted, however, that ground conditions often dictate the drilling technique required to achieve the scheduled depth. Also the effects of disturbance and the potential to create a vertical pathway for contamination, if bentonite seals and nested casing are not used, need to be considered. Some techniques may be more suitable than others yet not be widely available for use in the UK e.g. sonic or directional drilling.

In general the key elements to be considered are the following:

Potential for cross contamination from flushing media, investigation equipment, sampling point, sample equipment and surrounding media.

Loss of Volatiles volatiles are generally lost when material is disturbed or subjected to an elevated temperature. The investigation, sampling, storage and transport methods chosen should reflect this so as to provide accurate and consistent results.

Flushing media should also be considered as having the potential to mobilize or alter the status and amounts of various determinands, especially if they are soluble or volatile and water is used for example. This will also apply when the sample is taken from below a water table or other water surface.

Use of lubricants, adhesives and filter media ideally these should be chosen so as to not interact with or add to the determinands being tested. For example it may be better to use vegetable rather than mineral based lubricating oils. It is general good practice to make note of the materials being used so that they can be accounted for or discounted in subsequent analysis of the results.

In general all Soil Samples should:

Be extracted using clean and appropriate equipment. Be placed directly into clean and suitable sample containers. Be sampled away from any surfaces such as the edges of the window

sampler, bucket, shovel, plastic tube or any surfaces created by the investigation techniques.

Be thoroughly mixed so that they remain representative during transit and subsequent analysis.

Be appropriate in amount, volume and composition for the required testing schedule.


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Be representative of the material under investigation. Particle size will influence laboratory sample preparation and this should be noted as it will affect the results.

Not be left unsealed for a significant period of time Be described accurately or be fully representative of a soil horizon which

has been accurately described Be appropriately recorded and uniquely referenced in a manner

compatible with the requirements of the AGS Format, and safely sealed and labelled as soon as practicable after sampling.

Be stored and transported in appropriate conditions. 6 Groundwater Sampling In order to obtain a groundwater sample in a condition as representative of its in situ condition as possible it is generally necessary to purge the sampling point of the existing stagnant water in the standpipe or borehole.

Purging the standpipe should aim to remove the effects of:

Chemical interactions with the materials from which the hole or standpipe is constructed

Degassing and oxidation from contact with the air in the standpipe

Biological activity in the standpipe environment

Contamination from dust and extraneous matter which may have entered the standpipe or borehole.

Many contaminants will be adsorbed on to or will make up the sediment in the sample and hence a turbid sample may contain a greater concentration of a particular determinand than that of a clearer sample. For some contaminants, such as metals, filtering may be an acceptable way of removing the effects of such sediment but this may not be acceptable for contaminants with an affinity for the filter medium.

Alternatively samples can be recovered by using low flow techniques. With this technique, water is purged from the well through a flow cell at a rate that does not cause excessive drawdown in the well. The water level in the well is measured every 2 to 3 minutes during purging and purging is complete when water quality parameters such as pH, temperature, dissolved oxygen, electrical conductivity and redox potential have stabilised (typically this takes up to 20 minutes). The sample is then taken using the pumping equipment.

The choice of sample container, the decision to filter or not and (if used) the chemical fixatives added should be governed by the parameters to be analysed. Table 3 details some of the fixatives that can be used for certain parameters considered likely to be susceptible to alteration. Where monitoring is carried out as part of a long term programme of monitoring a consistent approach to sampling, fixing and filtering should be adopted to allow comparison between monitoring visits.


7 Gas and Vapour Sampling

Sampling of gases and vapours as opposed to monitoring with dedicated equipment such as gas detectors generally falls into two categories:

Bulk gas: Examples include methane, ethane, propane, butane, carbon dioxide, carbon monoxide, nitrogen and hydrogen sulphide.

Trace gas: Examples typically include VOCc, SVOCs and Cyanide.

Bulk gas samples are generally collected by pumping directly from a gas manifold or tap. The sample is collected in either a Gresham tube or Tedlar bag. In the case of a Gresham tube a hand pump is used to pressurize a re-usable steel cylinder with the sample gas and should ideally be purged using nitrogen gas before use. A Tedlar bag is a single use fluoroplastic film coated bag which does not require purging. However, like the Gresham tube, some form of pump usually needs to be fitted to the manifold or tap to provide a positive pressure to fill the bag.

Care should be taken in choosing the most appropriate sampling vessel as some gases such as hydrogen sulphide or hydrocarbon vapours can be adsorbed onto the metal surface of the Gresham tube and affect subsequent results if re-used. Tedlar bags, whilst single use and not requiring purging, are however more fragile and hence can be difficult to store and transport and also ideally need to be kept out of bright light which can affect the plastic.

Trace gas sampling is a more complex process involving pumping a measured volume of gas through an activated charcoal filter or other media over time from which the trace gases can be removed in a laboratory by some form of solvent extraction. The methodology is generally specific to the gas being tested for and reference should be made to Environment Agency (2004) Guidance for monitoring trace gases in landfill gas, Ciria 766 and the laboratory providing the sample media and testing.

8 Quality Control

On most sites a standardised sampling protocol implemented by experienced site personnel using good practice and procedures will generally provide an appropriate level of Quality Assurance (QA). Further specific examples of additional QA protocols that might be implemented are noted below.

On sites where a measured level of QA is required, the use of blank samples should be considered. The most commonly used methods of providing blanks are summarised in below:

Field blanks: Taken to assess the effect of the sampling process on the analysis. The sampling equipment should be rinsed at a predetermined frequency and the rinse water poured into two 1 litre glass bottles. All air should be expelled from the bottle before submitting for analysis.

Trip blanks: Taken to assess the effects of sample handling. A pre-packed vial sample usually containing known quantities of predetermined contaminants or de-ionised/distilled water will be labelled and returned to the laboratory for testing.


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Wash blanks: Taken to assess potential contamination from the sampling containers. A selection of sample containers are washed with de-ionised/distilled water prior to use and usually analysed for the same determinands as the sample.

In addition, duplicate samples may also be requested. These are generally taken to ensure that the medium being sampled is homogenous or to allow reference to the variability in the medium. In this case, industry standard is usually suggested as being one duplicate for every 10 samples taken. Duplicates may also be required for legal reasons so that all parties to a claim have a sample for independent testing or reference. In this case, ideally the whole sample should be made as homogenous as possible prior to creating separate sub-samples for each party.

Blanks and duplicates should be sent to the laboratory with other routine samples. However, it is standard practice to remove all reference to blanks and control samples on the laboratory copy of the chain of custody sheet.

During the transportation and storage of samples, all efforts should be made to cool the samples utilizing cool boxes and to get the samples to the laboratory within 24hrs. In cases where this is not possible, samples should be stored in a refrigerator to reach and maintain a low temperature to reduce the effects of possible biological activity.

All environmental samples should be labelled with the following which together form a unique and traceable sample in accordance with protocols embodied in the AGS Data Transfer Format:

Contract name / Site name

Location Identifier

Depth at which sample is taken

Date of sampling

Initials of Sampler

Additional information that might be added may include client name, sample type, time and unique reference number. Sample labels should ideally be waterproof and adhered to the sample container in advance. Labels will not generally adhere well to wet, greasy, dirty or condensate covered sample containers. Details provided on the label of each sample should be recorded on a chain of custody sheet that provides a traceable record of sample collection and movement between site and the laboratory. One copy of the chain of custody form should be dispatched with the samples to the laboratory and a duplicate copy should also be retained on site. The reference number of the relevant chain of custody sheet should be noted on each sample to aid the booking in system at the receiving laboratory.

Table 1- Comparison of Sample Containers

Contaminants Container Media Acid/

AlkaliMetals Other

InorganicsOils/Tar Fuel Solvents/

Volatiles Advantages Disadvantages

Plastic Bag S ++ ++ ++ + - - Cheap and readily available Leaks and is easily damaged

Plastic Tub (or pot)/ Bottle

S/W ++ ++ ++ + - - Cheap and readily available, Easy to use

Glass Jar/Bottle S/W ++ ++ ++ ++ ++ + Breakable Septum top Glass Vial

S/W + - - - + ++ Small and easy to store Small containers, difficult to fill, Expensive

Fluorinated Polymer containers e.g PTFE

S/W ++ ++ ++ ++ ++ - Expensive

Sampling Tube liners Plastic

S ++ ++ ++ + + - Readily available, easy to see the sample.

See Footnote

Metal Samplers S - + ++ ++ ++ - See Footnote Potential for Cross

Contamination, Very Expensive

Gresham Tube G - - + - - - Bulk Gas Purging Tedlar Bag G - - - - - + Bulk Gas Absorbent Media W/G + - + - ++ ++ Specialist Substances

Available

S-Soil W-Water G-Gas ++Good + Ok -No Note Samples should be removed rapidly if sampling for volatiles.


Table 2: Volumes Typical Recommended Volumes and Container Types required for soil and water analysis

Analyte Sample Type Container Volume Top

Fill level Notes

Metals Soil Plastic Tub 1 kg Snap top Plastic lid top Can be combined with Inorganics Inorganics Soil Plastic Tub 1 kg Snap top Plastic lid top Can be combined with Metals TPH / PAH Soil Glass Jar 250g Screw Top with PTFE Liner top Pesticides etc. Soil Glass Jar 250g Screw Top with PTFE Liner top VOC's Soil Glass Jar 60g Screw Top with PTFE Liner top Usually Requires 2 Metals Water Plastic Bottle 1 Litre Screw Top Plastic lid top Inorganics Water Plastic Bottle 1 Litre Screw Top Plastic lid top TPH / PAH Water Glass Bottle 1 Litre Screw Top with PTFE Liner top Pesticides etc. Water Glass Bottle 1 Litre Screw Top with PTFE Liner top Usually one per analyte type required VOC's Water Glass Vial 40ml Screw Top with Septum top Usually Requires 2

Notes:

1. A typical environmental sample will usually contain: 1 Plastic Tub or Bottle, 1 Glass Jar or Bottle and 2 small Jars or Vials 2. Leachates are usually undertaken on samples contained in the same materials and volumes as you would normally use for that analyte 3. A typical WAC test will require at least 2kg of sample, typically provided as additional Plastic Tubs and Glass Jars 4. Whilst the above is typical, the laboratory to be used should be consulted to determine the exact requirements for your testing suite 5. Sample volume may also depend on the grading and density of the material being tested.


Table 3- Fixatives

Parameter Sample Container Fixative ammonical nitrogen nitrite nitrate Chemical Oxygen Demand Total Organic Carbon phenols

Polyethylene Addition of H2SO4 until pH is less than 2

sulphides Polyethylene Addition of NaOH and zinc acetate

cyanide Polyethylene Addition of NaOH Until pH is greater than 12 metals Glass Addition of HNO3 to filtered sample until pH is less than 2

Notes 1. Care should be taken when using fixatives to ensure that they do not significantly affect the results by being inappropriately used, for example, filtering water samples prior to acidification.

AGS Guide to Environmental Sampling.pdfComparison of Sample Containers (table 1)Volumes (table 2)Fixatives-(table 3)

AGS Guide to Environmental Sampling

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