Session 2 Potential Sources of Contamination. Learning Objectives

Transcription

1 Session 2 Potential Sources of Contamination 1 Learning Objectives Develop skills in identifying potential sources of contamination contaminants of potential concern types of contamination Understand the differences between classes of contaminants types of contaminants LNAPL and DNAPL behaviour 2 What Makes a Site Contaminated? A relative term Depends on a combination of Type of substance Concentration (ppm, ppb) Location (soil, groundwater, surface water) Current, planned or adjacent land and water use Jurisdiction and regulatory standards 3 1

2 What Makes a Site Contaminated? Any substance in the wrong place at the wrong concentration G. Patrick, Concentration: Parts per Million (ppm) Measuring Parts per Million In water: milligrams per litre (mg/l) Example: 4 drops in a 200-litre barrel In soil: milligrams per kilogram (mg/kg) Example: 11 grains of sand in a bucket 5 Concentration: Parts per Billion (ppb) Measuring Parts per Billion In water: microgram per litre (µg/l) Example: 2 ml in an Olympic-size swimming pool 2 m 50 m 25 m In soil: microgram per kilogram (µg/kg) Example: Four marbles in the pool 6 2

3 Natural Background Concentrations Many substances are naturally present at background concentrations Background concentrations vary depending on location, geology Establishing background may be difficult consult local guidance 7 Small Group Activity Identifying Potential Sources of Contamination Identify the following: Operations and processes of potential environmental concern Contaminants of concern associated with the operations and processes you have identified Record your notes 8 Small Group A Route of proposed power transmission corridor Agricultural land Old municipal dump Agricultural land Farm house, barn, barnyard Cardlock (unattended) gas station Scenario A Small engine repair 9 9 3

4 Small Group B Auto wrecking yard Location of proposed runway extension for regional airport Agricultural land (Actively worked) Agricultural land (Actively worked) Dairy (Milk and cheese) Residential area (developed in 1970s) Scenario B Residential area (developed in 1930s) 1/19/ Small Group C Residential area (1990s construction) Residential area (1950s construction) Corner store Hardware store (Founded 1950) Dry cleaner Operating since 1960s Delicatessen Gas Station (Constructed 1998) Scenario C Route of proposed rapid transit line (elevated) Small Group D Residential area (developed in 1920s) Sawmill and planing shop Highway maintenance yard and vehicle garage Treated wood pole storage yard Residential area (developed in 1990s) Scenario D Proposed natural gas pipeline route (buried) 4

5 Debrief Small Group Activity What operations and processes did your group identify that are of concern? What contaminants of concern are associated with the operations and processes you identified? 13 Point Sources Common Point Sources Leaking storage tanks Leaking buried pipes or transfer lines Unlined lagoons Landfill leachate seeps Leaking or buried drums Contaminated fill Spills or derailments 14 Point Source: Storage Tanks Typical storage tanks at commercial facilities include USTs or ASTs for: fuel oil for heating systems diesel for emergency generator gasoline and diesel for vehicle fuelling waste oil spill containment UST = Underground Storage Tank AST = Aboveground Storage Tank 15 5

6 What do you notice? Point Sources Source: USEPA Point Source 1/19/ Point Source 18 6

7 Point Sources of Dry-Cleaning Contamination Ref: State Coalition for Remediation of Dry Cleaners, August Point Source Dry-cleaning solvent (PCE) leaked out of this pipe joint 20 Point Source 21 PVC pipe leading into sump was weakened by DNAPL discharge (tetrabromoethane) 7

8 More Subtle Point Sources Some hazardous materials can become point sources of contamination: Polychlorinated biphenyls (PCBs) Lead-based paints Mercury-containing equipment Where might we find some of these substances? 22 Hazardous Substances Polychlorinated Biphenyls (PCBs) PCBs are used as coolants and lubricants in some electrical equipment: Fluorescent light ballasts Fluid-cooled (not air) transformers Capacitors In Canada, since 1977, PCB manufacturing banned and PCB use restricted 23 Hazardous Substances Lead-Based Paint Lead from spilled or peeling paint may be detected in soil or groundwater Lead in Canadian paint phased out in early 1980s Post-1992 Canadian paints virtually lead-free 24 8

9 Hazardous Substances Mercury Mercury is used in Switches Fluorescent light tubes Metal halide lights Broken or discarded equipment can leak mercury into the subsurface 25 Non-Point Sources Common Non-Point Sources of Contamination Fertilizer applications Factory farms (manure) Ditch water infiltration Sewage sludge applications Particulate fall-out from smoke stacks 26 Non-Point Source 27 9

10 Non-Point Source Spreading Fertilizer 28 NAPLs LNAPLs Most of the petroleum hydrocarbons e.g., gasoline, middle distillates DNAPLs Most of the chlorinated solvents (e.g., TCE) PCBs Coal tar, creosote Some pesticides Mercury We can classify NAPLs according to their behaviour in the subsurface: floaters and sinkers 29 An LNAPL Conceptual Model 30 10

11 LNAPL Can Exist Below Water Table Hydrodynamic case Pour in olive oil first, chase with water Hydrostatic case LNAPL is like an iceberg Funnel Water Olive oil Tubing 31 Mobile LNAPL Released LNAPL migrates vertically downward through unsaturated zone, under gravity gradient X LNAPL may reach water table and pancake out (spread radially) Most lateral spreading will occur within capillary fringe Large group question: When will LNAPL finally stop spreading? 32 Mobile LNAPL Spreading continues until source is cut off, and/or entire volume is trapped and held by capillary forces (i.e., residual) Answer to large group question 33 11

12 Groundwater Flow Residual LNAPL Residual LNAPL immobile, trapped in soil by capillary forces mostly above water table, BUT Water table fluctuations may carry mobile LNAPL up and down smearing residual above and below water table This is a LONG-TERM source of contamination 34 Buried Utilities Can Act as Conduits Modified from Lundy and Gogel, A DNAPL Conceptual Model Direction Monitoring Well DNAPL Dissolved Plume Gravelly Sand Concentration Profile Silt Bedrock Silt 36 12

13 DNAPL in a Geoprobe Core Sample 1/19/ DNAPL in a Geoprobe Core Sample 1/19/ Schematic DNAPL Release 39 13

14 DNAPL Injection Experiment 40 Pouring dyed PCE into the ground DNAPL Injection Experiment Reality vs. Conceptualization PCE DNAPL at CFB Borden, University of Waterloo 41 Simulation of DNAPL Migration Through Soil 42 14

15 Lessons Learned Site history and use can indicate potential contaminants Contamination can be integrated into a CSM in a number of ways LNAPLs and DNAPLs have very different impacts and formulation within a CSM End of Session 2 Potential Sources of Contamination 45 15