TEST METHOD: Soil Sampling for contamination studies

Updated: 25 February 2003

RISK ASSESSMENT

Assess the Quality, Safety and Environmental risks of each step.

OVERVIEW

When land use is to be changed, the soil is tested for contamination as part of the process of determining its end use. The following guidelines shall be adhered to when sampling soils as part of a contaminant survey.

TASK SAFETY REQUIREMENTS

Safety boots are mandatory

Observe the requirements of the Chemical Hygiene Plan

Use appropriate PPE for the contaminant suspected. This may include disposable overalls, gloves, overshoes and respirators.

SPECIFIC JOB STEPS

RISK ASSESSMENT

RISK CONTROL

Select appropriate sample containers and transportation materials. Don’t know what type of bottle is appropriate, or transport temperature and holding time requirements? Refer to Sample collecting, handling and transporting
Samples should be collected in such a manner so as to best characterize the extent of contamination of the soil in question. There is no specific number or type of samples which will apply to all situations and best judgment will have to be used in conjunction with guidance from the literature. What literature? Refer to the field method bibliography.
The type of sample, grab or composite, will vary depending upon the constituent being identified. While grab samples come from one location, composites come from several locations and are joined to form one sample. When sampling for non-volatiles or semi-volatiles, several composite samples are preferred, with confirmatory grab samples. Possible loss of volatiles in composite samples. When volatiles are in question, care must be taken when collecting composite samples to minimize the loss of volatiles during handling. In order to minimize handling of volatiles, several grab samples are preferred, with confirmatory composite samples.
A. Tank PitIf there is a question as to the extent of residual contamination, or if comprehensive documentation is necessary, a tank pit may be sampled for laboratory analysis. A total of five samples should be taken from the excavation. One composite sample from each of the side walls at a distance approximately one third up from the bottom of the pit. Several samples should also be collected to form one composite sample from the bottom of the pit. Any remaining samples should be grab samples from areas with greater potential for contamination such as stained soils, adjacent to a corrosion hole, opposite a manway, or opposite a tank opening. From how deep should the samples be taken? All samples shall be taken no less than 15 centimeters below the exposed surface being sampled. Samples for compositing should be taken from random locations on the floor and walls of the tank pit.
B. Soil PileThe number of samples required for an excavated pile will be related to the quantity of soil stockpiled. The table at the end of this instruction can be used as a guide in determining the appropriate number of samples. Samples shall be collected in accordance with proper sample collection techniques. All samples must be collected in glass containers with air-tight sealable tops. Where in the pile should be sampled? Best judgment is needed to determine the most appropriate sampling locations. The objective of the sampling is to characterize the extent of contamination of the pile. Consideration should be given to how the soil was stockpiled. Is the most contaminated soil toward the top? Are areas visibly contaminated? How high and how long is the pile? It may be preferable to divide the pile into manageable segments. Samples should be taken from within the pile. Surface soil should not be used as sampling material.
C. Non-Excavated (Broadacre) Soils Treatment of non-excavated soil is similar to soil piles except that the contamination may spread over a wide area. It differs, however, in that the depths of the contaminated zone are varied. The sampling locations and depths are best laid out in a replicable grid. How many samples are required? For small areas (less that 10 hectares) use 16 sampling locations per hectare. For larger sites refer to the NEPM for Assessment of Contaminated Sites, see field method bibliography.
Sample collection.Determine sample locations by tape or GPS and record on a sample location plan.Use earthmoving equipment, drills, augurs or hand equipment as appropriate to excavate the area of investigation. Then use stainless steel equipment (spade, trowel etc) to obtain a clean sample.    
Place sample either directly into a sampling bottle if testing for volatiles, or into a mixing tray if sampling for metals. Place into transportation container. Record sample details on a chain of custody form, as specified in SFM2-159 Collecting, Preparing, Storing &Transporting Samples. Include a unique sample identifier, location, container type and requested analysis. Some metals such as mercury may be present in particulate or droplet form, not evenly distributed in the sample. The laboratory receiving them may sample a ‘clean’ part of the sample, missing the contaminant or getting unrepresentative readings. Mix sample in tray well, to distribte the contaminant evenly, so that the laboratory may analyse a representative sample. Transfer to sample bottle.
Wash all equipment between sampling locations. Dry on clean paper towels. Earthmoving equipment only needs the loose dirt removing from it as smaller sampling holes are made in the exposed soil surface by the smaller stainless steel equipment. Cross-contamination Wash equipment using three buckets. One with phosphate-free laboratory detergent, one with tap water and one with distilled water. Use plastic scrubbing brushes in the first two buckets. The brushes MUST STAY IN THEIR RESPECTIVE BUCKETS so as not to transfer contaminants.
After sampling, return any excess soil to the excavation. Washing water, waste paper towels and any disposable PPE shall be returned to the laboratory for disposal as contaminated waste    

Recommended Number of Soil Pile Samples

CONTAMINANT:

SEMI-VOLATILES

VOLATILES

SAMPLE TYPE:

Grab

Composite

Grab

Composite

SOIL QUANTITY (m 3):

 

0-50

1

1

1

1

50-100

1

2

2

1

100-200

1

3

3

1

200-300

1

4

4

1

300-400

2

4

4

2

400-500

2

5

5

2

500-800

2

6

6

2

800-1000

2

7

7

2

>1000

Proposed sampling plan shall be submitted for approval on site specific basis

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