Presentation given at Alberta CLRA conference in 2012 on the importance of background samples. Brief covers case study for naturally elevated metals in undisclosed location in Alberta.

1. Importance of Knowing What is Normal
(the need for control or background
samples)?
Court D. Sandau, PhD, PChem
CLRA Alberta Chapter 2012 Conference

2. Good Science, Needs Control
• All investigations require control samples
• Controls are needed to eliminate alternate
explanations of experimental results
– Environmental investigations general
hypothesis – “Is the site contaminated?”

3. Other Terms

4. Case Studies for Controls

5. Arson Investigations
• Controls are called comparison
samples
– Not known until after analyzed,
whether or not accelerants are
present

6. Litigation Cases
• Sample unusual locations
– Furnace filters
– Furnace ducting
– Attic dust
• Controls deliberately left out as
concentrations of contaminants are usually
found to be “normal”
• Without controls, +ve hit indicates pollution,
which could = $$$

7. Litigation
• Sampling homes or yards from
surrounding municipalities
• Sampled carpet dust (exposure) and
soils (guidelines)
• Provides comparison data to
otherwise unknown levels of
contaminants in unfamiliar matrices

8. Metals Case Study
• Development of historical pasture/farm land
adjacent to municipality in Alberta
• Approximately ½ quarter section
• No known or identifiable sources of
anthropogenic contamination
• Potential for incidental farm related spills
• No visible signs of impacts

9. Definitions for Soil Background
• Environmental Geochemistry Definition
– relative measure to distinguish between natural
element or compound concentrations and
anthropogenically influenced concentrations in‐
real sample collectives (Matschullat et al. 2000)
• ISO soil background content guidance
– Content of a substance in a soil resulting from
both natural geological and pedological
processes and including diffuse source inputs
(BS EN ISO 19258)

10. Soil Sampling
• Consultant identified arsenic exceedances
of Tier 1 AB Guidelines (17 mg/kg)
• Consultant undertook vigorous sampling
program
n = 473 samples (surface
to 2 mbg)
n = 18 background samples
• Comprehensive, but limited to arsenic and
a few other metals (barium, selenium and
thallium)

11. Choosing Location for
Background
• Concentration will vary with soil parent
material, soil depth, and hydrologic regime
• Sufficient (?) representative samples
outside area affected (more than 3)
• Statistical analysis likely required
Systematic grid
Define average

12. Regulations or Guidance
PROTOCOL FOR THE CONTAMINATED SITES REGULATION
UNDER THE ENVIRONMENT ACT
PROTOCOL NO. 9:
Determining Background Soil Quality
Prepared pursuant to Part 6 – Administration, Section 21,
Contaminated Sites Regulation, OIC 2002/171
The Contaminated Sites Regulation provides a
"release" as a contaminated site when the
concentrations of substances at a site do not
exceed local background levels.
EPA 540-R-01-003
OSWER 9285.7-41
September 2002
Guidance for Comparing Background
and Chemical Concentrations in Soil
for CERCLA Sites
Office of Emergency and Remedial Response
U.S. Environmental Protection Agency
Washington, DC 20460
If background levels exceed remediation criteria,
it is futile to reduce the contamination levels to
meet the remediation criteria. It is only possible
to remediate to background levels.
Environment Canada (http://
www.on.ec.gc.ca/pollution/ecnpd/tabs/ tab08-
e.html)

13. Site Data
x = 11.5
GM = 8.1
Max = 45.0
95% = 26.0
95UCL = 12.3
Med = 9.3
23% Above

14. Control Data
x = 14.9
GM = 11.0
Max = 29.0
95% = 29.0
95UCL = 19.4
Med = 19.4
44% Above

15. Results
• Site is similar to background site
• Site likely has baseline levels of
arsenic that sporadically exceed
Tier 1 (17 mg/kg) and Soil
contact (21 mg/kg) guidelines
• Presented to regulators and
stakeholders

16. Alberta Guidelines
ALBERTA TIER 2
SOIL AND GROUNDWATER
REMEDIATION GUIDELINES
2.4.2 Background Soil Quality
…In cases ‘where’ the natural background is
demonstrated to be greater than Tier 1 guidelines, the
remediation level shall be to natural background or to
guidelines developed using Tier 2 procedures.

17. Results of Study
• Definitively proved background
concentrations exceeded Tier 1
• Regulator requires proof that no risk exists
on site
– Through bioavailability study
• Under negotiations but due to time
constraints, may not be possible

18. Lessons
• It’s hopeless!
• Need to get regulators involved early in the
process when there may be background
issues
• Provide a solid study design and statistical
summary
– Need to show that the data is understood
• For contentious contaminants, may still
require additional study (sometimes it is
just optics)

19. Questions?
Contact Info:
Chemistry Matters
Court Sandau
csandau@chemistry-matters.com
www.chemistry-matters.com
Twitter – EnviroCertainty