Fill? What Fits the Bill?

Transcription

1 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

2 Overview! Purpose! Approach! Sampling Methodology and Selection Process Outline / Flowchart! Breakdown of Considerations/Requirements

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

4 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

5 Approach Literature Review Methodology / Process Development Local Source Sampling

6 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

7 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

8 Sampling Methodology and Selection Process

9 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

10 Flowchart : Process for Pre Determining Acceptable Fill Quality 10

11 Project Considerations/ Requirements Fill Type Laboratory Environmental Quality Methods Environmental Quality Objectives

12 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

13 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

14 Testing Considerations 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) 14

15 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

16 Project Requirements Environmental Quality Objectives - EQOs 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) 16

17 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

18 Closing / Recap

19 Flowchart Process for Pre Determining Acceptable Fill Quality 19

20 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

21 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

22 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

23 Questions 23