Page History

<span class="midtitle">Megasite characterization<br /><br /></span>
 <strong>Contaminant preselection approach</strong><br/><br/>
The contaminant preselection was based on the characteristics of the contamination sources. Two major sources of contamination were considered: waste heaps (primary) and Quaternary deposits (secondary). The preselection was oriented on those contaminants, which pose problems to both: to soil and groundwater at a national level. The background levels of contaminants in the subsoil environment were also taken into account. Next, the contaminants of concern were selected according to: 
<ul>
<li>observed frequency of occurrence in the environmental compartments within the megasite,</li>
<li>fate in the subsoil environment: the Natural Attenuation (NA) potential,</li>
<li>toxicity,</li>
<li>mobility in the subsoil environment,</li>
<li>availability of data.</li>
</ul>
As a result, the general list of the priority contaminants for the Tarnowskie Góry megasite (heavy metals and none-metals) was prepared (see table below).<br/><br/>
<table width="100%" border="1" cellspacing="0" cellpadding="3">
<tr height="60" bgcolor="#F4EBEA" align="center">
<td width="25%">Contaminant</td>
<td width="15%">Frequency occurrence</td>
<td width="15%">Natural attenuation potential</td>
<td width="15%">Toxicity</td>	
<td width="15%">Mobility potential</td>
<td width="15%">Availability of data</td>
</tr>
<tr align="center">
<td align="left">Arsenic</td>
<td>Moderate</td>
<td>High</td>
<td>High</td>
<td>Low</td>
<td>Moderate</td>
</tr>
<tr align="center">
<td align="left">Barium</td>
<td>High</td>
<td>High</td>
<td>Moderate</td>
<td>Low</td>
<td>Moderate</td>
</tr>
<tr align="center">
<td align="left">Boron</td>
<td>High</td>
<td>Low</td>
<td>Moderate</td>
<td>High</td>
<td>Moderate</td>
</tr>
<tr align="center">
<td align="left">Cadmium</td>
<td>Moderate</td>
<td>Moderate</td>
<td>High</td>
<td>Low</td>
<td>Moderate</td>
</tr>
<tr align="center">
<td align="left">Strontium</td>
<td>High</td>
<td>Low</td>
<td>Low</td>
<td>High</td>
<td>Moderate</td>
</tr>
<tr align="center">
<td align="left">Zinc</td>
<td>High</td>
<td>Moderate</td>
<td>Moderate</td>
<td>Low</td>
<td>Moderate</td>
</tr>
</table><br/>
At a later stage, a more focused re-evaluation was made for the priority contaminants, based on: 
<ul>
<li>the interpretation of modelling results and risk assessment</li>
<li>experiences of the liquidator of the chemical plant</li>
<li>conclusions of the group of experts meeting</li>
<li>results of the evaluation of the priority contaminants using the Pricon-tool (see: <a href="../tools/index3433.html?index=50"><i>Tools -> Pricon</i>)</a></li>
</ul>
As a result boron was selected as the most critical contaminant at the Tarnowskie Góry megasite.

<span class="midtitle">Clustering<br /><br /></span>
 <strong>Clusters at Tarnowskie Góry</strong><br/><br/>
The clustering approach for the Tarnowskie Góry megasite differs for these applied for the other cases, and it reflects the specific complexity of the problem in terms of geohydrological, economical and social conditions. There are three major clusters defined at the Tarnowskie Góry megasite that are oriented on receptors, pathways, boundary conditions and appropriate stakeholders interests (see figures and table below). Within the cluster the primary and secondary contamination sources are recognized. The clusters combine environmental and contamination 
characteristics, and boundary conditions.

<strong>Cluster I</strong> represents surface waters and soils with human exposure within the residential area in the close vicinity of the chemical plant. Potential risks related to the contaminants and various routes of exposure are taken into account.<br/><br/>

<strong>Cluster II</strong> comprises the subsurface with primary (waste heaps) and secondary (the Quaternary deposits) contamination sources, as well as contamination plumes and receptor wells in the Triassic aquifers (level I). This cluster is subdivided into two separate clusters because of the management reasons. These represent different receptors and different stakeholder interests.
Cluster IIa represents already the contaminated parts of the Triassic aquifers with the stakeholders' interests affected by deterioration of the groundwater quality. Cluster IIb comprises the area where the Triassic groundwater is under threat of future contamination. In cluster IIa - different contaminant plumes (level I) are combined together, along with the background chemical characteristics of the aquifer, as to give better opportunity for assessing and managing risks.
Cluster IIb combines flow directions and geological characteristics. In that cluster, various hydrological regimes are taken into account, as well as initial plume characteristics in cluster IIa. In that aspect various extraction regimes of operating wells are clustered within one management scheme established for the whole area.<br/><br/>

<table border="1" width="0" cellspacing="0" cellpadding="2">
<tr align="center" bgcolor="F4EBEA">
<td width="20%">Aspect/ Cluster</td>
<td width="20%">I</td>
<td width="20%">IIa</td>
<td width="20%">IIb</td>
<td width="20%">III</td>
</tr>
<tr>
<td>Contaminants</td>
<td>B, Cd, Zn, As Ba, Sr</td>
<td>B, Cd, Zn, As Ba, Sr</td>
<td>B</td>
<td>B</td>
</tr>
<tr>
<td>Main risk aspect</td>
<td>Complex human exposure</td>
<td>Complex contami-nation </td>
<td>Plume expansion</td>
<td>Plume expansion</td>
</tr>
<tr>
<td>Main management aspect</td>
<td>Land use</td>
<td>Water use</td>
<td>Hydrological regime - pathways</td>
<td>Hydrological regime</td>
</tr>
<tr>
<td>Sources</td>
<td>Primary and secondary </td>
<td>Primary and secondary </td>
<td>Secondary (Quaternary and Triassic plumes)</td>
<td>Secondary (Quaternary and Triassic plumes)</td>
</tr>
<tr>
<td>Area</td>
<td>Megasite</td>
<td>Megasite</td>
<td>Risk management zone</td>
<td>Risk management zone</td>
</tr>
<tr>
<td>Receptors/ interest</td>
<td>Land owner</td>
<td>Owners of the closed wells</td>
<td>Owners of the operating wells</td>
<td>Owners of the operating wells</td>
</tr>
</table><br/>

The characteristic of the Triassic aquifers (level I) is essential as natural and anthropogenic fractures in the Triassic formations (galleries, shafts) might be expected. Due to these fractures, potentially two groundwater flow directions are dominant: south-west and west. Therefore, two additional receptor-specific clusters were distinguished within cluster II: 

<ul>
<li>cluster IIb/S-W</li>
<li>cluster IIb/W</li>
</ul>

The hydrological regime is an important factor of risk distribution in the groundwater formations being at risk. Changes of the exploitation of two groundwater reservoirs Lubliniec-Myszkow and Gliwice (e.g. higher water extraction rates) may change the directions of groundwater flows. Currently, the water balance in the aquifers is stabilized and it is close to natural in comparison to the past high-rate extraction regime.<br/><br/>

<strong>Cluster III</strong> represents risk of contamination migration into the Triassic aquifer (level II) through diffusion processes between the levels I and II. The fluxes between these levels may be high, but the groundwater characteristic allows for high dispersion of contaminants in the water body of the second horizon. The clustering comprises secondary sources, migration pathways, use of these water resources and the background geochemical characteristic of layer II.<br/><br/>

<span class="midtitle">Modelling<br /><br /></span>
 Two basic methods of assessment were used according to differentiate cluster features:
<ul>
<li>health risk assessment,</li>
<li>groundwater transport modelling.</li>
</ul>
The health risk assessment was used to screen the risk in accordance with the land use pattern and to integrate contamination plumes in groundwater. The conceptual model for the human exposure was built.<br/><br/>
The groundwater transport modelling comprised:
<ul>
<li>building up of the conceptual model,</li>
<li>mathematical modelling.</li>
</ul>
The conceptual model of hydrogeological conditions was built up based on the following general assumptions.<br/><br/>
The research area of 116.3 km<sup>2</sup> covers the major groundwater intake wells (figure below), which have an impact on hydrodynamic conditions.

The water intakes may be susceptible to contaminants migrating from the dumping sites of the chemical plant. Within 2002-2003 the total anthropogenic drainage of the described water-bearing horizon based on well intakes and adits was 51,000 m<sup>3</sup>/d (30,000 m<sup>3</sup> - intakes, 21,000 m<sup>3</sup>/d i.e. 0.24 m<sup>3</sup>/s - adits).<br/><br/>
The investigated site is located at the border of two main Triassic groundwater reservoirs, the Major Groundwater Basins (MGWB): Gliwice (MGWB 330) and Lubliniec-Myszkow (MGWB 327). 
<br/><br/>
Based on the hydrogeological profiles, four water-bearing horizons were distinguished: two in the Quaternary deposits and two in the carbonate Triassic formations (MGWB 330). The geological model is presented in figure below.

The structure of the water-bearing horizons and characteristic parameters that were included in the digital model comprise: thickness, coefficients of filtration, effective porosities, and percolation parameters between layers. The main recharge of these aquifers takes place through infiltration of precipitation. Field research indicates the possibility of infiltration from surface watercourses, located within the area of the chemical plant.<br/><br/>
<strong>Hydrodynamic modelling</strong><br/><br/>
The conceptual model of hydrogeological conditions was converted into a digital model. A quasi 3D model was developed, which consists of four permeable layers linked together by infiltration of water through semi-permeable layers (see figure below). Two permeable layers represent Quaternary, and the other two - Triassic formations of Muschelkalk and Roet. The boundary of the modelled groundwater system was set at the bottom of the Roet formations.

In the performed simulation studies the modelling was used to analyse the map of groundwater table elevations (see figure below), as well as directions and velocities of the groundwater flow (see figures below). The results of simulations were presented at three hydrodynamic situations: 
<ol>
<li>current hydrodynamic situation with water extraction from the wells (the beginning of 2003);</li>
<li>hypothetic hydrodynamic situation without water extraction from the wells located within the model area;</li>
<li>hypothetic situation with a hydrodynamic barrier of several fictitious wells extracting water from the Muschelkalk water-bearing horizon (layer 3).

<strong>Modelling of boron migration</strong><br/><br/>
The main objective of the modelling studies was to evaluate the current spreading and future scenarios of boron migration in groundwater within the Triassic aquifers. The studies consisted of two stages. The first stage included representation of the current situation based on monitoring studies on the spatial distribution of boron concentrations. The second stage was focused on forecasting the spreading of boron in the selected time frames (up to 2100).<br/><br/>
<br/><br/>
The forecast studies were carried out again for three hydrodynamic conditions, resulting from different groundwater extraction regimes: 
<ol>
<li>current groundwater extraction regime;</li>
<li>no groundwater extraction;</li>
<li>extraction from existing wells at the current rates and with a hydrodynamic barrier of fictitious wells</li>
</ol>
As an example, the plume extension of boron in 2030, as predicted by the simulation studies at the extraction regime 1, is shown in figure below:<

The results of scenario simulations of boron migration within the Triassic aquifers at different extraction regimes were used for the detailed risk assessment in the next step of this section.<br/><br/>

The digital modelling of the groundwater circulation system and water flow simulations was done using the MODFLOW-96 software. Simulations of the advective flow were performed using PMPATH and contamination migration - using MT3D.

<span class="midtitle">Determination of risk<br /><br /></span>
 To match the different assumptions for the clusters, combined approaches were applied to carry out the risk assessment. A two-step risk assessment approach shaped for each cluster was used: 
<ul>
<li>risk assessment based on regulatory limits;</li>
<li>risk assessment based on exposure scenarios.</li>
</ul>
For cluster I, the quality of surface waters, soil and air were assessed. The assessment, carried out for the megasite area, was based on soil quality standards. Data on contaminant contents were used, including measured values and their interpretations (interpolations and simulations of changes in environmental media). At this stage, this assessment was supported with the health risk assessment, which was based on various exposure scenarios. The results show that the combined risks are moderate and negligible in the context of land use patterns. <br/><br/>
The assessment of groundwater quality performed for cluster IIa was based on the groundwater quality standards and it showed unacceptable level of risk for the existing groundwater use pattern.
<br/><br/>
The health risk assessment for cluster IIa was based on the use of groundwater for drinking purposes. The oral uptake was considered as the exposure pathway. Analysis of the toxicity of contaminants showed that, they have different end-points (target organs or processes). From the toxicological point of view it may be useful to combine arsenic with barium plumes as one risk plume and barium with cadmium as second risk plume. Boron and strontium can be analyzed separately. However, in this case the integrated risk plumes were similar to these determined separately on the basis of drinking water quality standards. The plume extensions of boron, barium, cadmium and zinc used for risk assessment are shown in subsequent figures.

Results confirmed that boron could indeed be used as an contamination indicator in groundwater modeling for clusters IIb and III. Groundwater is intended to be used for drinking purposes, therefore, strict requirements concerning quality standards are required.<br/><Br/>
For cluster IIb the risk was defined as: 
<ul>
<li>plume extension along with consecutive rising of contaminant concentrations in given water extraction zones (wells) to an unacceptable levels at a given time,</li> 
<li>rising of background levels of contamination (still below the quality standards but above the natural background values - risk of unacceptable trend formation).</li>
</ul>
The similar assumptions were made in the case of cluster III. The risk assessment was based on quality standards as the reference level (see table below), and it was defined as:
<ul>
<li>risk of rising the background concentration trend formation in the scope of quality parameters (plume extent)</li>
<li>unacceptable fluxes within the Triassic groundwater (i.e. between layers: I and II).</li>
</ul>
Table: Drinking water quality requirements<br/>
<table border="1" width="100%" cellspacing="0" cellpadding="2">
<tr align="center">
<td width="30%">Heavy metal</td>
<td width="35%">Drinking water standard</td>
<td width="35%">Carcinogenic *****</td>
</tr>
<tr>
<td>Arsenic<br/>[µg/dm<sup>3</sup>]</td>
<td>10**</td>
<td>yes</td>
</tr>
<tr>
<td>Barium<br/>[mg/dm<sup>3</sup>]</td>
<td>0.7*</td>
<td>no</td>
</tr>
<tr>
<td>Cadmium<br/>[µg/dm<sup>3</sup>]</td>
<td>3**</td>
<td>No - oral intake; Yes - inhalation exposure</td>
</tr>
<tr>
<td>Boron<br/>[mg/dm<sup>3</sup>]</td>
<td>1**</td>
<td>no</td>
</tr>
<tr>
<td>Strontium<br/>[mg/dm<sup>3</sup>]</td>
<td>22****</td>
<td>no</td>
</tr>
<tr>
<td>Zinc<br/>[mg/dm<sup>3</sup>]</td>
<td>0.5-5***</td>
<td>Not classifiable as to human carcinoge-nicity</td>
</tr>
</table>
<font size="1">* Guidelines for Drinking Water Quality, third edition, WHO<br/>
** Polish Health Ministry regulation<br/>
*** Polish Environmental Ministry regulation on drinking water from surface waters.<br/>
**** RAIS Risk Assessment Information System, September 2003,<br/>
***** IRIS Integrated Risk Information System United States Environmental Protection Agency, March 2003<br/>
</font><br/><Br/>
A set of scenarios was developed to assess the risk in cluster II and III with the following situations being analyzed:
<ul>
<li>residual contamination in the soil and Quaternary deposits,</li>
<li>total clean-up of the megasite area,</li>
<li>groundwater extraction rates at the current levels.</li>
</ul>
Modeling was also done for other contaminants, including barium, zinc and cadmium. In a long-term perspective, i.e. till 2030, at the current level of groundwater extraction the boron concentration contour line of 0,5 mg/dm<sup>3</sup> is expected to move slightly, according to groundwater flow directions. It can be concluded that both now and within the next 30 years, the spreading of boron within the Muschelkalk water-bearing horizon, which is the main drinking water source for the area of Tarnowskie Góry, does not pose any significant risk for the major wells. Regarding boron, in the forecasted period of 30 years its concentrations in water from some currently exploited wells of minor importance located on the outskirts of Tarnowskie Góry, i.e. in Opatowice and Strzybnica, should not exceed the standard value of 1 mg/dm<sup>3</sup> although they are situated on the direction of contaminant plume movement. Also the Staszic water-intake is not expected to be affected in the forecasted time (see picture below).

The performed classification of risk for each defined cluster based on the IMS approach (see the manual details of determining risks: <a href="../manual/detailsea25.html?id=24">classification of risk levels</a>) showed that for: 
<ul>
<li>cluster I, the risk is on the level 3,<br>
The receptor is contaminated; the national legal standard (intervention level if existing) is exceeded.
</li>
<li>cluster IIa,  the risk is on level 5,<br>
The receptor is highly contaminated; the national legal standard (intervention level if existing) is exceeded more than 100 times. 
</li>
<li>cluster IIb,  current risk is on level 1,<br>
The receptor and the transfer pathway are not contaminated; concentrations are below the national legal standard.</li>
<li>cluster III, current risk is on level 1, <br>
The receptor and the transfer pathway are not contaminated; concentrations are below the national legal standard.</li>
</ul>

High risk for the cluster IIa, is due to the extensions of barium, boron, cadmium, arsenic and zinc plumes (see figure below). The current risk for cluster IIb is low but it may increase as should be considered in the future. In the case of cluster III, the future risk is much lower, although it cannot be completely excluded.

</a>

<span class="midtitle">Finalize clustering<br /><br /></span>
 <strong>Risk reduction objectives and re-adjustment of RMZ</strong><br/><br/>
According to the results of the previous steps, the following plane of compliance for risk management purposes for the Tarnowskie Góry megasite were derived (see figures below).
<ul>
<li>Plane of compliance I: established at the source. It is possible to control only the Sa and partially Sb sources at this plane.</li>
<li>Plane of compliance IIa: established at the west and southwest boundaries of the contamination plumes (boron plume). There are possibilities of measuring groundwater quality and implementing control measures to control the contamination at this plane for that purpose the existing wells can be used.</li>
<li>Plane of compliance IIb: established at the west and southwest boundaries of the risk management zone (RMZ) (boron plume contour at the year 2030). There are possibilities of measuring groundwater quality to control the contamination at this plane and implementing mitigative measures. For that purpose existing wells can be used.</li>
<li>Plane of compliance III: there is a possibility of measuring groundwater quality. Control measures are similar to those established at the IIa compliance plane.</li>
</ul>

According to the IMS and the performed risk assessment, the preliminary risk reduction objectives for the Tarnowskie Góry megasite were proposed (see figure below). The following management goals were established for each risk cluster:
<ol>
<li>Cluster I
<ul>
<li>Short-term elimination of the existing and potential health risks posed by the soil and surface water contamination. According to the risk assessment, there is no need for further remediation measures besides those already established within the program of the chemical plant liquidation. There is no need to establish other management goals.</li>
</ul></li>
<li>Cluster IIa 
<ul>
<li>Short-term reduction of contamination deposited in the Quaternary layers (control of the secondary contamination source).  </li>
<li>Short-term reduction of the contamination fluxes towards the cluster IIb (plume control/containment), </li>
<li>Long-term remediation of contaminated groundwater in the Triassic aquifers.</li>
</ul>
</li>
<li>Cluster IIb
<ul>
<li>Short-term elimination of risk concerning contamination of operating wells,</li>
<li>Short-term inversion of groundwater quality deterioration trends ("reversal trends"),</li>
<li>Long-term water quality improvement within the RMZ until the status of "good quality" is reached.</li>
</ul></li>
<li>Cluster III
<ul><li>Short-term reduction of contamination fluxes within the Triassic groundwater (i.e. between levels I and II).</li></ul></li></ol>