Using Site-Specific Life Cycle Inventory to Support a Contaminated Site Management Decision

1. Using Site-Specific Life Cycle Inventory to Support a Contaminated Site Management Decision J.F. MÉNARD, J. GODIN, S. HAINS, L. DESCHÊNES, R. SAMSON Seattle, 23-09-03

2. Goal of the Study • Identify, among four alternatives, the management option for a landfill site that minimizes potential environmental impacts, classified as: • Primary impacts: generated by the landfill leachate, mainly contributing to local impacts (ETP and HTP); • Secondary impacts: generated by the site management operations (i.e.: excavation, waste transportation,…).

3. Presentation Outline • Goal and Scope Definition • site history • management scenarios • functional unit • Inventory analysis • system definition • data source summary • assumptions • Results summary • LCIA • Sensitivity analysis • Conclusions and Limits

4. Site History SPENT POTLINING (SPL) LANDFILL: • A waste produced from aluminum refining; • Classified as a dangerous waste in North America in the late 1980’s; • Major contaminants: Fluoride, Cyanide, Fe, Al.

5. Site History • 1980: Closure of the landfill: 360 000 m3 of waste mix and 100 000 m3 of SPL; • 1989: Covered with a waterproof liner to limit landfill leachate generation; • Today, groundwater is still contaminated and so is the surface water at the site’s edge; • Contaminated soil (before capping) - slow release of adsorbed contaminants.

6. Management Scenarios • The site represents a low risk for the aquatic ecosystem (preliminary ERA); • Contaminants such as cyanide have a potential for natural attenuation (Meehan et al., 1999).

7. Functional Unit • The management, for a period of 50 years, of the landfill site (i.e.: 360 000 m3 of waste mix, 100 000 m3 of SPL and 200 000 m3 of contaminated soils). • 50 years : Period of time estimated for pseudo-steady-state conditions to be reached under the no-intervention scenario. - Excludes: long term emissions caused by the eventual deterioration of capping.

8. System Definition

9. System Definition Energetic valorization (3b): system expansion (ISO 14 049, 2000)

10. Data Source Summary

11. Data Source Summary Landfill leachate flow simulations: A predictive site-specific model was used to simulate the contaminants emissions to surface waters through groundwater: • Based on site-specific data: hydrogeological, geochemical, and microbiological characteristics. • Three-dimensional finite element model : FRAC3DVS model (Therrien and Sudicky, 1996).

12. Assumptions • Landfill leachate flow simulations: Geochemical conditions were assumed to be constant during the 50-year period. • Water emissions during excavation works (precipitation and infiltration ): • Flow calculations are based on equipment characteristics, economic and technical constraints: - Option 2 – over 4 years - Options 3a and 3b – over 7 years • The treatment was considered to be inefficient. • Volatile compounds released from SPL: Neglected.

13. LCIA Methodology Characterization factors have been developed: - ETP (Al, cyanide, fluoride) and HTP (Al)

14. Summary of Results Comparative Assessment • Option 1 (No-intervention) has the lowest potential environmental impacts for all categories. • Option 3b is second except for GWP, AP, NP and POCP.

15. Summary of Results Primary impacts • Primary impacts are essentially local (on site). • Excavation reduces the primary impacts by a factor of 2. Option 1

16. Summary of Results Option 2 • On-site cell: material production contribution (ex.: steel = 10,7 ktons for Option 2). • Excavation water is the major contributor to ETWA and ETWC. Option 3b Option 3a • Option 3a and 3b, important contributionof thelong-distance transport by train (ex: soil to landfill - 4000 km) • Option 3b, beneficial effect of the reuse of the SPL fraction as an alternative fuel.

17. Sensitivity Analyses Temporal boundary: leachate emissions over 100 years for Option 1: • Impacts increase < 7% for all concerned categories. Amount of contaminated soil excavated: • Uncertain: between 140 000 m3 and 200 000 m3; • Baseline scenario: upper limit as worst case; • Lower limit: reduces size of containment cell and transported volume. Ranking remains the same.

18. Conclusions • Option 1: • Lowest potential environmental impacts; • Primary impacts (on-site) are significant (almost twice as much as for excavation scenarios); • Further investigations are required for the acceptance of Option 1 (i.e.: full ERA, evaluation of site-specific natural attenuation potential). • If Option 1 is rejected: Option 3b should be implemented based on the results of this comparative LCA: • Further investigations to select an appropriate excavation water treatment to reduce the impact associated with the excavation life cycle stage.

19. Limits of the Study • Possible overestimation of the primary impacts: EDIP method considers no chemical degradation and all chemicals are biologically available; • Land-use impact category inclusion could appreciably influence results: • Option 1: the site is not restored. • Excavation options: the site is restored to the industrial criteria. • A longer temporal boundary could influence the results: - Option 1: deterioration of the capping resulting in increased leachate generation; - Excavation options: secure cells were considered totally sealed but could themselves become sources of contamination in a long term perspective.

20. Using Site-Specific Life Cycle Inventory to Support a Contaminated Site Management DecisionQUESTIONS Additional information: Julie.godin@polymtl.ca Seattle, 23-09-03

21. Summary of LCI Results Materials involved in excavation and disposal site remediation scenarios

22. Data Source Summary Landfill leachate flow simulation: Calibrations: • Groundwater flow: by trial-and error using water table elevations measured on-site; 2) Contaminant fate and transport: • using different parameters (hydraulic conductivities, dispersivity coefficients, Kd, and source concentrations); • matching of the simulated concentrations with the average observed on-site concentrations.