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Modelling impacts of oil-shale mining on groundwater resources in the Slantsy region,

Russia Jussi Leveinen, Boris Aneshkin, Francois Blanchard, Michael Staudt, Gijs Van den Dool, Svetlana Sapon, Olga Kruglova

2Jussi Leveinen, Maegs 15

Narva Groundwater Management Plan

• Life TCY –project

St Petersburg Geological Expedition

BRGM

GTK

FFEM

(Fonds Francais Environment Mondial)

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Potential pollution sources in Slantsy

Underground mining of Kukersite and dumiping of mine wastes: 1930-2004

Oil-shale processing (Kiviter technolgy) and combustion for energy 1955-2004

Other industries, transport, municipal solid and liquid wastes, agriculture

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Current pollution

• Mining stopped 2004 – dewatering pumping continues– possible new start of activites?

• No oil-shale processing for fuel in Slantsy – Processing of imported coke for paints and varnishes etc.

• Improved information on the current pollution situation is available

• Main concerns on mine water and dewatering:– Can mine water be used as a source of drinking water?– What happens if the dewatering pumping is stopped?

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Past industrial releases

• No active mining or oil-shale processing!

– different pollution today that in the near past

• Limited information on past releases and production rates

• Limited analytical information– Figures relative to MPC– Analytical methods and their

detection limits– Number of chemical

components analysed

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Chemicals of concern

• Phenols, heavy metals, sulphates • Mine dewatering and leachates from mining dumps

• oxidation of sulphides • other geochemical processes• phenols

– Oils shale processing (Kiviter technology) and combustions for energy• Industrial waste water, leachates from ash and semicoke dumps and settling

ponds

– Municipal sewage waters and solid wastes• Human metabolism=> phenols, nitrates, bacteria

– Live stock farming• Animal metabolism=> phenols, nitrates, bacteria

– Traffic • Fuels and petroleum products including phenol releases

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Release scenarios

The Risk Assessment Reports European Chemical BureauPrepared in the context of Council Regulation (EEC) No. 793/93 on the evaluation and control of existing substance

Phenol(draft Cd-document)

Estonian studies of Kiviter-processing and environmental emissions

e.g Kamenev I., Munter R., Pikkov L. and Kekisheva L., 2003 Wastewater treatment in oil-shale chemical industry. Oil Shale, 20,4, 443-457.

Russian data on local annual use of oil shale

1.4 million tons/a in 1990-1994

WWTPPhenol canal

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3D model of stratigraphical main units

Boundary of Mid/Upper Ordovician Kukruse/Uhaku-stage (Kukersite)

Lower Ordovician/Cambrian including Dictyonema Oil Shale (DOS)

Ordovician karstic limestones

Devonian aquifers and aquitards

Cambrian clay(aquiclude) overlying cross-border aquifers

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Model area

• Hydrological flow accumulation model (enhanced digital elevation model)

• A 3D MODFLOW (HUF) multilayer groundwater flow model for the Slantsy-area

• Main stratigraphical layers from C-O to Q with 7 model-grid layers

• Scenario modelling:– pumping as before– pumping stops (no remediation)– phenols, sewage, heavy metals– possible means for remediation

Main area of interest for modelling under task 3

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Drawdown around the mine area

• Conservative estimates of flow rates

Capture zone

80-year travel paths from C-O and O to the mines

Mine dumpsTop

Top of Ordovician

End points of 80-year flow paths from the top entering to the Ordovician systems

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What this all means…

– Polluted groundwater under Slantsy-town is subsiding towards the mine – Indications of pollutants (phenol, nitrate, heavy metals) already observed

in the mine water– Groundwater from overlying deposits entering sulphide bearing

Ordovician limestones and oilshale layers• Oxidation of sulphides releasing sulphates in extensive area but pH-buffered

by carbonates• Changing ion strengths and redox-conditions=> ion-exchange, desorption,

dissolution of heavy metals such as Cd, Cr • Hazardous concentrations reached without AMD

– Full impacts not yet detectable in mine discharges– Chemical quality of groundwater/minewater definitely not stable

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When dewatering is stopped what will happen…

• Hydraulic heads recover• Groundwater will become diverted

to flow laterally to rivers and other surface water bodies

• Impacts of past releases and activites can emerge after long time

• Impacts to aquatic ecosystems (rivers, lakes) can be predicted poorly relying on existing environmental data

• In Slantsy: significant risks for current water management (relying on surface water resources)

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Conclusions

• Strategy development for mine closure– State-of-art assessment of environmental impacts during

hydrogeological recovery • integrated water management tools and hydrogeological models

– human and ecological risk assessment– impacts/implications for water supply

– Feasibility of active and passive remediation methods• constructed wetlands in discharge areas• biochemical (bacterial processes) in mine water treatment• monitored natural attenuation

– Implementation and update plan• maintanance of monitoring and remediation in post-mining socio-

economical conditions