From Wasteland to Green Parkland The West Melbourne Gasworks

Transcription

1 MGP 2006 International Conference Reading UK 2-4 April 2006 From Wasteland to Green Parkland The West Melbourne Gasworks Ken Mival - Senior Principal - URS Australia (Presenter) Warren Pump Senior Principal URS Australia Glenn Dixon Projects Coordinator - VicUrban Melbourne Docklands The Vision 1

2 Gas production started 1st Jan

3 1920s Significant expansion and reconfiguration in 1920s 3

4 West Melbourne Gasworks Site in 2000 Regulatory Progress EPA - Clean up Notice Issued Audit Starts & Risk Based Criteria Established Clean-up Contract Let by Docklands Statements of Environmental Audit Issued Clean-up Notice Lifted - GQRUZ Declared 2002 to Groundwater Monitoring Continues 4

5 Development of Risk Based Criteria Tier 1 Soil Criteria - Gas Industry Association & NEPM HRA for Residential; Open Space; and Roads Ecological Risks - Back Analysis from Yarra River Attenuation in Groundwater - Bioscreen Estimated Max Allowable Soil Source Concentrations Moderated by HRA; Odour; and Union Concerns Fate & Transport Modeling and HRA for NAPLs Acceptance Criteria for Clean-up Contract Units mg/kg 5

6 Clean-up Process : Methods Considered Cap and Contain with: Bentonite Slurry Walls» Limitations: Obstructions Long term integrity NAPL sources remain on site In-situ Deep Soil Mixing Barriers» Limitations: as above Clean-up Process : Methods Cont. Excavation, Separation of Inert Solids, then Potential Treatment of Fines by: Low Temperature Thermal Desorption [cost & time] Bioremediation [time and effectiveness] Incineration for Energy Recovery [trial proposed] Chemical Treatment [many attempts] Stabilisation and Landfill [last resort & low cost] 6

7 Clean-up Process First Contract Excavated & Treated about 300,000m to 8 metres depth Power-screen separates coarse material; Concrete and Brick crushed & re-used Fines treated to reduce/stabilize contaminants About 15% processed material returned to excavation Clean-up Process contd. Remove tarry liquids and shallow groundwater Separation in Interceptors Hydrocyclones to remove silt and some NAPLs Backfill Soils from large CBD excavations Re-used soil from other Docklands sites 7

8 The Theory The Reality large areas under management simultaneously 8

9 Clean-up Process contd Contractor Proposed Treatment Options: Energy recovery for tars and oily wastes [unavailable due to constraints at power station] Containment of source areas by capping & deep cut-off» [Obstructions uneconomic - did not proceed] Permanganate treatment of PAH soils [Attempted but unsuccessful] Fenton s Reagent (Peroxide) to treat PAHs [Also failed] Clean-up Process contd Lime Treatment of PAH in Soils Reduces by about 30%» [partly successful some re-use on site] Excavation and Dump Approx 350,000 tonnes to landfill 150kL of liquid tarry wastes removed off site 9

10 Exothermic Reactions up to 100 o C and up to 30% Lime in some stockpiles! 10

11 Pug Mill for Fenton s Reagent Trial Clean-up Process contd GRS Remediation Excavation and Treatment within Tent Reterra Machine to Crush and Mix Soils Enhanced Bioremediation Odour management Tent; Daily cover; Deodorisers 11

12 Clean-up Process contd Results Partial Success with Naphthalene and TPH BaP largely unchanged Attributed to project timing in winter Approx 50,000 tonnes of hydrocarbon contaminated wastes disposed to landfill GRS under wraps to control odour 12

13 Excavations up to 9.5m deep Addition of materials to control odour when outside the tented area 13

14 Worst Case Scenario - Post Clean-up Modeled Potential Extent of Vapour Risk from NAPLs in Worst Case Scenario Benzene 14

15 Groundwater Monitoring 2002 to 2005 TRHs Area A Fill - TRH (C10-C36) (140m g/l trigger) mg/l TRH C May-02 Aug-02 Nov-02 Feb-03 May-03 Aug-03 Date Nov-03 Feb-04 May-04 Aug-04 MW27A MW28A MW29A MW 18A Benzene Area A Fill - Benzene (0.5m g/l trigger) mg/l Benzene May-02 Aug-02 Nov-02 Feb-03 May-03 Aug-03 Nov-03 Date Feb-04 May-04 Aug-04 MW27A MW28A MW29A MW18A 15

16 Total PAH Area A Fill - Total PAH (1mg/L trigger) mg/l PAH May-02 Aug-02 Nov-02 Feb-03 May-03 Aug-03 Date Nov-03 Feb-04 May-04 Aug-04 MW27A MW28A MW29A MW 18A Phenols Area A Fill - Phenols (5m g/l trigger) 2.5 MW27A mg/l Phenol May-02 Aug-02 Nov-02 Feb-03 May-03 Aug-03 Date Nov-03 Feb-04 May-04 Aug-04 MW28A MW29A MW18A 16

17 Metals - Manganese Area A Fill - Manganese (10m g/l trigger) MW27A mg/l Mn May-02 Aug-02 Nov-02 Feb-03 May-03 Aug-03 Date Nov-03 Feb-04 May-04 Aug-04 MW28A MW29A MW18A Metals - Nickel Area A Fill - Nickel (2mg/L trigger) mg/l Ni MW27A MW28A MW29A* 0 May-02 Aug-02 Nov-02 Feb-03 May-03 Aug-03 Date Nov-03 Feb-04 May-04 Aug-04 17

18 Cyanide - Area A Area A Fill - Cyanide 20 MW27A MW28A 15 MW29A mg/l CN May-02 Aug-02 Nov-02 Feb-03 May-03 Aug-03 date Nov-03 Feb-04 May-04 Aug-04 MW19A trigger ph MW18A Cyanide Area B (Source Zones) Area B Fill - Cyanide MW24A* 60 MW23A 50 MW13A mg/l CN MW14A MW15A MW21A 10 0 Aug-01 Dec-01 Apr-02 Aug-02 Dec-02 Apr-03 date Aug-03 Dec-03 Apr-04 Aug-04 MW26A ph trigger * Indicates x 10 Employee Presentation p 36 18

19 Conclusions The Risk Management approach allowed development whilst contamination remains Major sources of groundwater pollution have been removed to the extent practicable Metals and Hydrocarbons in groundwater have reduced or remain at acceptable concentrations Cyanide mobilised by high ph in groundwater is short term Assumptions in Risk Assessments and Modeling were appropriate Contingency groundwater management plans are not required to be implemented Wetlands Recycle Stormwater For Irrigating Parkland 19

20 Award Winning Park on Area B 20

21 Innovative large mobile sculpture in children s play area A walk from south to north through the park 21

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24 Acknowledgements Mr John Tabart Retiring CEO - VicUrban Mr Glenn Dixon Projects Coordinator VicUrban and Co-Author Mr Warren Pump URS Site Superintendent and Co-Author Mr Colin White GHD - Project Manager West Melbourne Gasworks Clean-up 24