Fill? What Fits the Bill? Sampling Methodology and Selection - - PowerPoint PPT Presentation

› Fill? What Fits the Bill?

Sampling Methodology and Selection Process for Imported Aggregate Materials

Authors Meredith Guest, P.Eng., SNC-Lavalin Inc. Patricia Carmichael, M.Sc., P.Geo., SNC-Lavalin Inc. Scott Irwin, B.Sc., Defence Construction Canada April 26, 2016

Overview

• Purpose
• Approach
• Sampling Methodology and Selection Process

Outline / Flowchart

• Breakdown of Considerations/Requirements

Purpose

To revise/develop a process for the import of aggregate materials

Purpose

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› To revise/develop a process for the import of aggregate

materials

Why?

› Historical issues sourcing “clean” import aggregate materials that in the end fail guidelines due to naturally occurring metals and sampling and analytical methodologies › Previous methods included sampling and analyzing aggregate as soil › Currently no consistent and clear methodology for contractors / consultants to follow for the selection of imported fill material

Approach

› Literature Review › Methodology / Process Development › Local Source Sampling

Approach

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Steps included:

› Literature Review:

› Definitions › What constitutes aggregate material? › How does this apply to environmental quality guidelines / standards? › Lab methods (what is typical for aggregate material?) › Environmental quality objectives (how are results interpreted?) › Guidance from other jurisdictions (what do other regions / departments do?)

Approach (continued)

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› Development of Sampling Methodology / Process

› Key considerations from literature review › Step-by-step process › Flowchart (easy to flow guide)

› Sampling / Analysis at Local Sources

› Conducted field sampling to test process

Sampling Methodology and Selection Process

Sampling Method / Selection Process˗ Outline

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› Developed based on project considerations / requirements

› Material type › Appropriate laboratory analyses › Environmental quality objectives

› Other considerations / factors

› Exemptions (i.e., volume to be imported) › Source information already available › Land use

› Detailed Step-by-Step Procedure developed into easy to follow Flowchart

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Flowchart :

Process for Pre˗Determining Acceptable Fill Quality

Project Considerations/ Requirements

› Fill Type › Laboratory Environmental Quality Methods › Environmental Quality Objectives

Project Considerations

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› Is required fill material Soil?

› Soil classification standards provide guidance for differentiation between soil types and can include anything from clay to boulders › Soil can be broadly defined as: › unconsolidated mineral or organic material, rock, fill, sediment deposited on land (BC Contaminated Site Regulation - CSR) › “unconsolidated material on immediate ground surface that serves (or has potential to serve) as a medium for plant growth (Canadian Council of Minister of the Environment - CCME) › But, in terms of analytical methods, soil is defined as particles < 2 mm in particle size

Project Considerations

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› or Coarser Aggregate?

› Particle size larger than 2 mm › Regular lab analyses for soil quality not done on particles > 2mm without grinding to smaller size › Environmental concerns related to coarser aggregate (i.e., Acid Rock Drainage or ARD - potential of crush rock) is different from soil

Testing Considerations

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› Laboratory Methods

• Soils

› Federal and Provincial regulated testing methods for soil quality include wide variety of parameters › Analyses completed on particles <2mm › Analyses recommended dependent upon potential contaminants of concern from the source Other (larger material with weathered surfaces ex. Gravel / cobbles)

› Laboratory Methods

• Coarse Aggregate (Crush Rock)

› Rock with freshly exposed surfaces poses concern for Metals Leaching (ML) and ARD › Generation of ARD and ML can be enhanced by human activity ex. when bedrock is mined for construction › Lab testing methods include; › Toxicity Characteristic Leaching Procedure (TCLP) › Synthetic Precipitation Leaching Procedure (SPLP) › Mine Water Leaching Procedure (MWLP) › Shake Flask Extraction (SFE) › Acid Base Accounting (ABA)

Project Considerations

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› Environmental Quality Objectives

(EQO)

• Dependent on:

› Type of aggregate being imported › Location of receiving fill site › Near surface water receptor › Above/below groundwater table › Land use Assumption: › Aggregate only sourced from virgin non-contaminated sources › Environmental concern considered to be naturally occurring metals and ARD potential

Project Requirements

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Soil Quality Results › CCME CEQG for Soil › Regional background concentrations (i.e., BC Ministry of Environment Protocol 4) › Site specific background levels / Tier 3 site specific standards › For crushed fines (< 2mm) › Test for ARD potential Coarse Aggregate (Crush Rock) › Solid Phase - Review 3x crustal abundance or regional background to identify elevated metals › Leachate Testing – SFE preferred › Water quality guidelines (fresh/ marine) › Consider fill placement above/ below water table › Consider placement within close proximity to surface water › ABA testing (NPR, paste pH and sulphide content)

• Environmental Quality Objectives - EQOs

Project Requirements

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• ABA Testing

› Neutralization Potential Ratio (NPR)

› Neutralizing Potential - NP/ Acid Potential - AP › Ratio that indicates acid generation potential › NPR<1 high potential (should not be disturbed, BC Ministry of Transportation and Infrastructure MoTI) › Target >2

› Crushed Paste pH

› Indicate current acidic conditions › Paste pH <6 acidic; 6 to 9 = neutral › Target >5.5

› Sulphide%

› Used in conjunction with NP › Target <0.3%

Closing / Recap

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Flowchart

Process for Pre˗Determining Acceptable Fill Quality

Sampling Method Step by Step

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• 1. Volume (any exemptions?)
• 2. What type of material

› Is it soil, coarse aggregate or

• ther
• 3. Follow recommended testing

based on material type › Soil – total metals › Coarse aggregate – leachate and ABA testing › Other?

Step by Step

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› 4. Compare to EQOs

› Soil ( landuse, placement, background – at receiving site) › Coarse Aggregate (leachate, ABA testing) › 5. Consideration for existing chemical data › How old is it? › Is it representative of material to be imported? › For rock is it from same rock face as tested?

Application

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› Procedure / methods tested at local sources (3 local quarries with variety

• f aggregate)

› Soil testing completed on soil products › No metals exceedences noted when compared to commercial guidelines › pH range exceeded CCME CEQG guidance but within recommended 5 to 9 range › Coarser aggregate also tested for metals but used to provide additional information for ARD /ML analyses. Note as material would be crushed in lab it doesn’t represent its condition on a receiving site and is not soil. › Testing for ARD and ML potential completed on Coarse Aggregate › Overall results acceptable › Considerations › pH values can be outside of guideline range (concern when pH is <5) › Individual metals exceedences in ARD and ML testing (potential testing bias)

Questions

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