Two case studies are presented on the beneficial use of SWM pond sediments as environmentally sustainable and cost effective alternatives to landfill disposal.
2. Overview of Case Studies A & B
• Both residential SWM ponds require sediment cleanouts in 2017 to restore
storage capacities and water quality treatment efficiencies.
• Sediment metal concentrations were low. However, Petroleum Hydrocarbons
(PHCs) and Polyaromatic Hydrocarbons (PAHs) exceeded Ontario Regulation
153/04 Table 1 background soil standards, which triggered regulated waste
management requirements.
• Non-hazardous landfill tipping fees would be $360,000 for Pond A and $684,000
for Pond B.
• MOECC approval of the Pond A sediment reuse pilot study is expected to be
issued within the next eight weeks.
• The Canadian Food Inspection Agency (CFIA) has approved the Pond B sediment
reuse pilot study.
2
• A risk based weight-of-evidence approach demonstrated the potential benefits
of sediment reuse as an alternative to landfill disposal.
4. Risk Based Weight of Evidence
4
Petroleum hydrocarbon (PHC) source and bioavailabiity
evaluationsby Gas Chromatogram-FlameIonization
Detector (GC-FID) chromatograms
Polyaromatic Hydrocarbon (PAH) source and bioavailability
evaluationsby chemical mass balance modelling
Plant and earthworm ecotoxicity and bioavailability
testing
Ontario Regulation 153/04risk assessment
5. Different PHC Product Bioavailabilities
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Examples: gasoline, diesel and kerosene
Examples: weathered asphalt, tires, engine emissions
More
Bioavailable
Less
Bioavailable
6. 6
Examples: gasoline, diesel and kerosene
Examples: weathered asphalt, tires, engine emissions
More
Bioavailable
Less
Bioavailable
Dominant PHC sources in
Ponds A and B sediments
Different PHC Product Bioavailabilities
7. Relevance of Bioavailability?
7
• O.Reg. 153/04 soil standards
assume that contaminants are 100%
bioavailable.
• Soil standards may over estimate
true toxicity risks for some PHC
sources.
9. GC-FID Chromatograms
9
Essential to PHC Source Identifications
Sediment Sample
Extract injection
F2, F3, F4
concentrations
quantifiedby
chromatogram
integrations
) ) ) ) ) ) ) )
ion flowflame detector
capillarycolumn
carrier
gas
line
Vaporizer
Oven
Flame Ionization
Detector
electronic
signal
10. Typical SWM Pond Sediment PHC Pattern
10
Common PHC
sources reported by
Carbon Range
GC-FID Chromatograms Can Be Provided By Most Laboratories
11. Plant and Earthworm Ecotoxicity Studies
Results Were Key to Beneficial Use Approvals
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• SWM Ponds A and B. Environment Canada 21-day benchscale test
methods. Plants thrived in 80% sediment plus 20% compost mixtures.
Endpoint measurements were not significantly different than the clean
control soil measurements.
• SWM Pond B. Environment Canada 52-day benchscale test
methods. Earthworms thrived in 80% sediment plus 20% compost
mixtures. Endpoint measurements were not significantly different
than the clean control soil measurements.
• Tissue sample chromatograms found no evidence of PHC absorption.
12. 12
Residential SWM Pond A Case Study
MOECC Approval Process
Sediment Reuse as Topsoil on Municipal Road Boulevards
13. 13
Residential SWM Pond A Case Study
Pilot Study Approval Process
PHC and PAH chemistry data identified sources and bioavailability risks
Results:Primary sources were asphalt, car tires with minimalgasoline engine emissions = low bioavailability
Plant EcotoxicityTests
Results:Plants thrived in the mixture of 80% sediment + 20% compost.
Months of Meetings and Phone Calls Between the City, CH2M, Ontario Ministry of Agriculture
Food and Rural Affairs (OMAFRA) and the Ontario Ministry of Environment and Climate Change
(MOECC) Approval Branch, Standards Development Branch and local district office.
Result: CH2M conducted a risk assessmentto apply the mixture of 80% sediment +
20% compost on municipal road boulevards.
Risk AssessmentResults
14. O.Reg. 153/04 Table S2 Soil Component Values
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Adult Outdoor
Worker Risk
B(a)P
Example: Benzo(a)Pyrene Risk Assessment
Risk Based Soil
component
value 0.096
mg/g
Table 1
Background
Soil Standard
0.3 mg/g
Residential SWM Pond A Case Study
• The average sediment B(a)P concentration of 0.49 mg/kg exceeded both values
15. Adjusted Exposure Frequency
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S2 Adult Outdoor
Worker Risk
Benzo(a)Pyrene Risk Assessment Example
Becomes
9.6 mg/kg
Residential SWM Pond A Case Study
• The average sediment B(a)P concentration of 0.49 mg/kg did not exceed the
adjusted 9.6 mg/kg S2 soil component value
• The MOECC Modified Generic Risk Assessment(MGRA)model assumes
contact for 5 day per week.
• Exposure to road boulevard soil is most likely to occur during landscaping
activities which would be completed 1 day per week; time on the
boulevard would likely be less than 0.5 days.
• The 5 days/week exposure was reduced to 0.5 days/week
• The reduced exposure period increased the S2 component value from
0.096 mg/kg to 9.6 mg/kg
16. Adjusted Toxicity Reference Value
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S2 Adult Outdoor
Worker Risk
Benzo(a)Pyrene Risk Assessment Example
Becomes
0.7 mg/kg
Residential SWM Pond A Case Study
• The average sediment B(a)P concentration of 0.49 mg/kg did not exceed the
adjusted 0.7 mg/kg S2 soil component value
• CH2M Risk Assessor, Krista Barfoot, was aware of recently updated
toxicity data for B(a)P that is currently considered acceptable and being
applied for risk assessments in Ontario
• The updated toxicity data was applied to the MOECC MGRA, leaving all
exposure factors at their default values
• The updated toxicity data increased the S2 component value from
0.096 mg/kg to 0.7 mg/kg
17. 17
Boulevard Pilot Study Plan
300 m3 of Sediment Spread Across Four Boulevards
$31,000 Tipping Fee Savings
Residential SWM Pond A Case Study
Vegetation and topsoil will
be stripped and replaced
with 80% sediment plus
20% compost mixture.
Only vegetation will be
stripped. Original topsoil
will remain in place.
North Zone
Sediment+Compost
South Zone
Original Topsoil
• Each zone will be planted with the samespecies and monitored for statisticaldifferences over time.
Example: Planting Area 4
• Soil chemistry will be included in the monitoring plan as well.
18. 18
Residential SWM Pond B Case Study
CFIA Approval Process
Sediment Reuse as a Tree Nursery Topsoil Fertilizer Product
19. 19
Residential SWM Pond B Case Study
Tree Nursery’s Poor Soil Texture and Low Organic Matter and
Could be Improved by Sediment Amendments
Silty Loam, 3% Organic Matter
SWM Pond B Sediment
Sand, 0.2% Organic Matter
Tree Nursery Soil
Grain Size Analysis
Sand Silt Clay
20. 20
Residential SWM Pond B Case Study
Good
Fair
Poor
Topsoil Quality Rating
Unamended tree nursery soil
Predicted future soil amended with 80%
sediment + 20% compost
80% sediment + 20% compost product
Soil Texture Triangle
30cm Layer of Sediment Plus Compost Would Improve
Nursery Soil From Poor Sand to a Good Sandy Loam
21. 21
Why CFIA Approval Instead of
OMAFRA NASM Approval?
Residential SWM Pond B Case Study
• The sediment was approved for use as a Non-agricultural Source Material (NASM) product.
• The NASM approved application rate would only allow a 0.6cm layer to be applied annually
for 45 years, which would not be enough to significantly improve the soil texture and organic
matter content.
• The CFIA approved application rate was the same as NASM. However, the CFIA has the
authority to permit the total 45-year volume to be applied on a ONE TIME ONLY basis. This
would be enough to significantly improve the tree nursery soils.
22. 22
Tree Nursery Pilot Study Plan
400 m3 of Sediment Spread Across 0.5ha of Land
$41,000 Tipping Fee Savings
Residential SWM Pond B Case Study
100% sediment amendment
80% sediment and 20% compost amendment
Unamended control soil
• Four randomized treatment zones
• 25 seedlings for three tree species will be
planted and monitored for 3-5 years.
• Soil chemistry analysis will also be included
in the monitoring plan.
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Summary
• This process involvedmany unexpected rabbit holes, but they ultimately
led to regulatory approvals
• The risk based weight of evidence approach was essential to the approval process
• The MOECC, CFIA and OMAFRA were very helpful and supportive during the
entire process
• We expect that the future Excess Soil BMP legislative changes will simplify the
sediment beneficial use approval process.
• However, every approval will require match making between each SWM pond
and each recipient site.
24. THANK YOU
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Contact information:
Lisa Rocha
416-661-6600 ext.5786
lrocha@trca.on.ca
www.sustainabletechnologies.ca
Francine Kelly-Hooper
519-502-3122
francine.kellyhooper@ch2m.com
Krista Barfoot
519-579-3500
krista.barfoot@ch2m.com
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