› 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 › 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 4
Approach › Literature Review › Methodology / Process Development › Local Source Sampling
Approach 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?) 6
Approach (continued) › 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 7
Sampling Methodology and Selection Process
Sampling Method / Selection Process ˗ Outline › 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 9
Flowchart : Process for Pre ˗ Determining Acceptable Fill Quality 10
Project Considerations/ Requirements › Fill Type › Laboratory Environmental Quality Methods › Environmental Quality Objectives
Project Considerations › 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 12
Project Considerations › 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 13
Testing Considerations › Laboratory Methods › Laboratory Methods • Soils • Coarse Aggregate (Crush Rock) › Federal and Provincial regulated › Rock with freshly exposed surfaces testing methods for soil quality poses concern for Metals Leaching include wide variety of parameters (ML) and ARD › Analyses completed on particles › Generation of ARD and ML can be <2mm enhanced by human activity ex. when bedrock is mined for construction › Analyses recommended dependent upon potential › Lab testing methods include; contaminants of concern from the › Toxicity Characteristic Leaching source Procedure (TCLP) › Synthetic Precipitation Leaching Other (larger material with Procedure (SPLP) weathered surfaces ex. Gravel / cobbles) › Mine Water Leaching Procedure (MWLP) › Shake Flask Extraction (SFE) › Acid Base Accounting (ABA) 14
Project Considerations › 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 15
Project Requirements • Environmental Quality Objectives - EQOs Soil Quality Results Coarse Aggregate (Crush Rock) › CCME CEQG for Soil › Solid Phase - Review 3x crustal abundance or regional background › Regional background to identify elevated metals concentrations (i.e., BC Ministry of Environment Protocol 4) › Leachate Testing – SFE preferred › Water quality guidelines (fresh/ › Site specific background levels / marine) Tier 3 site specific standards › Consider fill placement above/ › For crushed fines (< 2mm) below water table › Test for ARD potential › Consider placement within close proximity to surface water › ABA testing (NPR, paste pH and sulphide content) 16
Project Requirements • 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% 17
Closing / Recap
Flowchart Process for Pre ˗ Determining Acceptable Fill Quality 19
Sampling Method Step by Step 1. Volume (any exemptions?) 2. What type of material › Is it soil, coarse aggregate or other 3. Follow recommended testing based on material type › Soil – total metals › Coarse aggregate – leachate and ABA testing › Other? 20
Step by Step › 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? 21
Application › Procedure / methods tested at local sources (3 local quarries with variety of 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) 22
Questions 23
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