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Version, februari 4th, 2000

ANNEXES Circular on target values and intervention values for soil remediation

Four annexes belong to this circular:

•        annex B contains the measurement and analysis regulations for soil/sediment and groundwater for the substances listed in annex A;

•        annex C gives the data required for determining the remediation urgency and the remediation deadline for the substances in part A; annex D provides a guideline for dealing

ANNEX A: TARGET VALUES, SOIL REMEDIATION INTERVENTION VALUES AND INDICATIVE LEVELS FOR SERIOUS CONTAMINATION

Introduction

Soil remediation policy uses soil remediation intervention values, indicative levels for serious contamination and target values. These three types of standards are dealt with below. The point of departure in setting standards for environmental policy as a whole is the risks involved. This strategy is set forth in the document Premises for Risk Management [Omgaan met risico's]. The risk-based approach in environmental policy (Ministry of Housing, Spatial Planning and the Environment (VROM), Lower House of Parliament, parliamentary proceedings 1988-1989, 21 137, no. 5).

The intervention values and the accompanying target values for soil/sediment and groundwater are given in table 1. The indicative levels for serious soil contamination and the accompanying target values for soil/sediment and groundwater are given in table 2. The intervention values, indicative levels and target values for soil/sediment for metals depend on the concentration of organic substances and clay. The additional comments to table 1 and 2 describe how the values can be converted for the soil to be assessed. The soil type correction is not applied for the intervention value for PAH (sum of 10) for soils with an organic matter content of up to 10% and for soils with an organic matter content from 30% upwards.

Soil remediation intervention values

The soil remediation intervention values indicate when the functional properties of the soil for humans, plant and animal life, is seriously impaired or threatened. They are representative of the level of contamination above which there is a serious case of soil contamination.

The soil remediation intervention values are based on extensive studies of the National Institute for Public Health and Environmental Protection (RIVM, report numbers 725201001 to 725201008 inclusive, report numbers 715810004, 715810008 to 715810010 inclusive, report numbers 711701003 to 711701005 inclusive) of both human and ecotoxicological effects of soil contaminants.

Human toxicological effects have been quantified in the form of concentrations in the soil above which the so-called maximum permissible risk (MPR) for humans may be exceeded. For non-carcinogenic substances this corresponds to the Tolerable Daily Intake (TDI). For carcinogenic substances this is based on an additional chance of tumour incidence of 104 for lifetime exposure. It is assumed here that all exposure routes are operational.

Ecotoxicological effects are quantified in the form of concentrations in the soil above which 50% of the potentially present species and processes may experience negative effects. The ultimate intervention values for soil and sediment are based on an integration of the human and ecotoxicological effects. In principle the most critical effects are definitive.

The intervention values for groundwater are not based on any separate risk evaluation with regard to the presence of contaminants in groundwater, but are derived from the values for soil/sediment.

The intervention values in this circular deviate for some substances from the values proposed by RIVM. There may be several reasons for this. The report of the Technical Soil Protection Committee (TCB) may have resulted in adjustments to the RIVM's proposals, but it may also be the case that during policy discussions new data became available or additional considerations played a role.

Intervention values are related to a spatial scale. For there to be a case of values being exceeded and thus an instance of serious contamination, the average concentration of a minimum of 25 m3 of the soil volume in the case of earth or sediment contamination, or 100 m3 pore saturation soil volume in the case of groundwater contamination, must be higher than the intervention value for at least one substance. The protocols for preliminary and further investigations indicate how tests should be carried out. If one of the different sampling protocols is being used or will be used, the sampler himself needs to determine and give adequate reasons as to how the 25 m3 or 100 m3 criteria have been tested.

Serious contamination below the level of the intervention value

In specific cases there is a chance that for concentrations in the soil below the intervention levels the functional properties of the soil for humans, plant or animal life have nevertheless been seriously impaired or are in danger of being impaired and that there is a case of serious contamination. A few examples are given below:

•        If in the case of point sources of pollution (for example based on calculations) it is likely that
the failure to take measures in the near future (a maximum of a few months) will result in
soil contamination on the said scale, then one is also dealing with a case of serious
contamination.

•        Humans can be exposed to soil contamination through numerous routes. When determining
human exposure for the purpose of deriving intervention values the assumption has been
that all exposure routes are in place. A type of standard behavioural pattern has been
assumed to determine exposure. Filling in most of these factors has only a limited impact on
the exposure occurring, but the influence of a few of these factors such as soil ingestion
and the consumption of crops grown on contaminated soil can be considerable. If the
standard is exceeded for these factors, this may result in exposure above the human MPR
without the intervention value being exceeded.

•        The MPR for humans can also be exceeded at concentrations below the intervention value
in the case of the inhalation of volatile compounds under floor areas and in ambient air.

If a situation of this kind is suspected it is advisable to have an additional investigation carried out into the actual exposure. An additional investigation is necessary to ascertain the deviation in relation to standard exposure and what the repercussions of this may be. The C-SOIL/SEDISOIL/VOLASOIL-models developed should be used for this in which the actual consumption/inhalation can be filled in instead of the standard. The actual exposure should then be compared with the MPR for humans. If this is exceeded one is dealing with a case of serious soil contamination.

Indicative levels for serious contamination

The RIVM's proposals for intervention values have not resulted in intervention values being set for a number of substances. The so-called indicative levels for serious contamination have been given for these substances. Indicative levels have been set for substances in the second, third and fourth series. No indicative levels have been set for the first series of substances.

There are two reasons why it was decided to set indicative levels for the second, third and

fourth series of substances instead of intervention values.

1.   There are no standardised measurement and analysis regulations available or to be expected in the near future. Annex B gives an overview of the available measurement and analysis regulations. In principle indicative levels have been given for substances for which there are no measurement regulations for soil/sediment and groundwater.

2.   The ecotoxicological underpinning of the intervention values does not exist or is minimal and in the latter case it would appear that the ecotoxicological effects are more critical then the human toxicological effects. The TCB's report gives a number of criteria which can be used to decide whether the ecotoxicological underpinning is sufficient. On the strength of the TCB report the following criteria have been used in this circular to determine whether an intervention value can be set:

•        there have to be a minimum of four toxicity data available for a minimum of two taxonomic groups;

•        for metals all the data have to relate to the soil compartment;

•        for organic substances a maximum of two data may be derived from data on the water compartment via equilibrium partitioning;

•        there have to be a minimum of two data for individual species available.

If one or more of these criteria fail to be met and if ecotoxicological effects are more critical than human toxicological effects, the setting of an indicative level for serious contamination suffices. For example this is the case for silver and beryllium.

The indicative levels have a greater degree of uncertainty than the intervention levels. The status of the indicative levels consequently is not equal to the status of the intervention levels. Exceeding or undershooting of the indicative levels therefore does not have any direct consequences on a decision about the gravity of the contamination being taken by the competent authority. Hence the competent authority should bear in mind other considerations besides the indicative levels when deciding whether there is a case of serious contamination. Examples which spring to mind are:

1.      Decide on the basis of other substances whether there is a case of serious contamination and whether remediation is urgent. Frequently several substances occur simultaneously in contaminated sites. If intervention values have been set for other substances, it can be ascertained on the basis of these substances whether there is a case of serious contamination and whether remediation is urgent. In a case of this kind an estimate of the risk for substances for which there are only indicative levels is less relevant. It is however important to make a risk estimate for substances for which there is only an indicative level if there is no question of serious contamination or remediation being urgent for other substances.

2.      An ad hoc determination of the actual risks. Other site-bound factors alongside toxicological criteria play a role in determining the actual risks for deciding on the urgency of remediation. These include exposure possibilities, the use of the site or the surfaces of the contamination. These factors can frequently be readily determined and this allows a reasonable estimate of the actual risks to be carried out, despite uncertainty as to the indicative levels. It is advisable here to use bio-assays, since this solves the problem of the uncertainties in the ecotoxicological underpinning as well as the uncertainties arising as a result of the lack of standardised measurement and analysis regulations.

3.      Additional investigation into the risks of the substance. Additional toxicity experiments can be carried out to make a better estimate of the risks of the substances.

Procedure for deriving intervention values and indicative levels for serious contamination

The first circular containing intervention values (Circular on intervention values for soil remediation; Netherlands Government Gazette 1995, no. 95) was drawn up in 1994. The substances listed in this circular are referred to as the first series of substances. The RIVM has carried out an ecotoxicological and human toxicological risk evaluation of these substances. Intervention values for earth/sediment and for groundwater have been set by circular on the basis of this study. For the first series no distinction has been made between intervention values and indicative values for serious contamination.

Since 1991 provincial authorities, local authorities, environmental inspectorates and consultancies have been reporting substances encountered in the soil, but not included on the intervention values list dating from 1994. For a number of these substances the RIVM has carried out risk evaluations per series of substances and made proposals for intervention values. The risk evaluations have been carried out in a similar way to those for the first series of substances from 1994. The TCB has published a report on the RIVM's proposals. The Working Group on Soil Remediation Urgency and Intervention Values (UI) of the Soil Steering Party (StuBo) has made a proposal for intervention values and indicative values for serious contamination on the basis of the RIVM's proposals and the TCB's report. A circular was published in 1997 for the second and third series of substances (Netherlands Government Gazette 1997, no. 169). The values for the fourth series of substances are given in the present circular.

In future new series of substances will go through the same procedure. The choice of substances for future intervention values is dealt with in annex D.

Target values

The target values indicate the level at which there is a sustainable soil quality. In terms of curative policy this means that the target values indicate the level that has to be achieved to fully recover the functional properties of the soil for humans and plant and animal life. Besides this the target values give an indication of the benchmark for environmental quality in the long term on the assumption of negligible risks to the ecosystem.

The target values derive from the Integrated Environmental Quality Standards project (called INS) and were published in December 1997 (VROM, INS for Soil, Water, Air 1997). The INS target values have been included in the circular with a few exceptions. The INS target values are underpinned by a risk analysis wherever possible and apply to individual substances. The same target values for soil/sediment as in the present circular, which applies to soil remediation policy, are included in the Fourth Report on Water Management (NW4).

Target values soil/sediment

For soil/sediment the target values from the INS project have been checked for their practical feasibility in the project evaluating the use of target values (HANS), which was carried out in the period 1996-1998. The principle is that soils in relatively unpolluted areas in the Netherlands must for the most part meet the target values. The HANS project has drawn up a list of target values and a method of testing these so that the chance of soils in relatively unpolluted areas meeting the target values is a minimum of 95%. Where necessary the INS target values have been adjusted to the results from the HANS project.

The list of soil/sediment target values has been coordinated with the former list of intervention values. If there was a sum standard for the intervention value (this is a standard for a specific group of allied substances), a sum standard target value was also set. In that case this deviated from the target values for individual substances derived as part of INS.

The value for EOX is a trigger value. If the value is exceeded this does not result in the conclusion being drawn that the earth or sediment is polluted but that there is a necessity for further investigation. The investigation will have to ascertain whether the exceeding of the trigger value is the result of the presence of contaminants or whether it has a natural cause.

The following applies to testing the quality of a batch of earth against the soil/sediment target values:

•        the quality of the sample data must be sufficient to allow the test to be implemented. This means that two combined samples are compiled, each comprising 50 increments. The quantity of earth/soil to be assessed is a maximum of 1250 m3 (around 2000 tonne). This can be deviated from with reasons in the case of larger (or smaller) homogenous quantities provided the quality of the test is not diminished;

•        for non-suspect situations the combined samples are examined for the following substances: arsenic, cadmium, copper, chrome, mercury, nickel, lead, zinc, PAH (sum of 10), mineral oil and EOX. For suspect situations the package is added to by other substances which have a bigger chance of being encountered in higher concentrations;

•        if there is a target value for an individual substance that comes under the quantification limit then the target value is exceeded if the quantification limit is exceeded;

•        if there is a target value for a group of substances and substances which are part of this group are encountered in non-quantifiable concentrations below the quantification limit, 0.7 * of the quantification limit is taken in determining the concentration of the sum of the total group of substances;

•        clean soil/sediment exists if the following three conditions are met:

1.      all substances to be tested are below the interim value (V£ (interim value + intervention value) and for sediment are also under the trigger value. The trigger value is given in NW4, Ministry of Transport, Public Works and Water Management (V&W), December 1998);

2.      there are a maximum of N substances exceeding the target value. N depends on the number of substances to be tested: for 10 to 20 substances N = 3; for more than 20 substances N = 4. No limit may be exceeded in the case of less than 10 substances;

3.      the exceeding of the limit for the N substances amounts to a maximum of a factor of two, except for DDT/DDE/DDD and the drins, for which a factor of three applies.

Reference should be made to NEN 5740 for more information on implementing soil research or sampling a quantity of earth to check the target values. This Dutch standard is published by the Dutch Standardization Institute (NNI).

It was observed in HANS that the file with data on concentrations of substances in relatively unpolluted areas is incomplete. Hence it was decided to build up a complete database which will give information on the concentrations in relatively unpolluted areas for all substances for which target values have been set. This can then be used in a number of year's time to evaluate the testing rules and to make adjustments to these if necessary. The HANS follow-up project, Background values 2000 (AW2000), is currently at the definition phase.

Groundwater target values

Tables 1 and 2 also include target values for groundwater. For metals a distinction is made between deep and shallow groundwater. The reason for this is the difference in background concentrations in these. An arbitrary limit of 10 metres has been adopted. It has to be remembered that this limit is indicative. If information is available that another limit is more plausible for the site to be assessed then a different limit can be adopted. An example which springs to mind is information about the boundary between the phreatic groundwater and the first aquifer.

•        For shallow groundwater (< 10 metres) the environmental quality objectives for soil and water (MILBOWA) values have been adopted as target values. These are based on background concentrations and serve as a guide.

•        For deep groundwater (> 10 metres) the target values proposed in INS have been adopted. This means that the target value comprises the background concentration which is naturally present (BC) plus the Negligible Addition (NA). The background concentrations included in the INS are given as a guide.

In both cases the background concentration given must be viewed as a guide. If information is available on the local background concentration, this can be used as target value together with the Negligible Addition (NA). More information on background concentrations of metals in different areas in the Netherlands can be found in the RIVM report number 711701 017.

For some metals the background concentration in shallow groundwater is considerably higher than the background concentration in surface water. The background concentrations of surface water and groundwater and the target values based on these, are not coordinated. When granting permits for pumping and discharging groundwater to surface water as part of the Pollution of Surface Waters Act (WVO) this may result in the target values for surface water being exceeded. It is up to the competent authority to decide whether the local target values should be adjusted.

As part of INS the derived target values for some aromatic compounds and chlorinated hydrocarbons are approximately the same as the intervention values for groundwater. Since this produces an unworkable situation in practice, the INS target values for these substances have not been adopted and the MILBOWA target values have been retained.

Notes to table 1:

1.   Acidity: pH (0.01 M CaCl₂). In order to determine whether pH is greater than or equal to 5, or less than 5, the 90 percentile of the measured values is taken.

2.   In areas subject to marine influence higher values occur naturally (salt and brackish water).

3.   Differentiation by clay content: (F) = 175 = 13L (L = % clay).

4.   PAH (sum of 10) here means the total of anthracene, benzo(a)anthracene, benzo(k)fluoroanthene, benzo(a)pyrene, chrysene, phenantrene, fluoroanthene, indeno(1,2,3-cd)pyrene, naphthalene and benzo(ghi)perylene.

5.   'Chlorobenzenes (sum)' here means the total of all chlorobenzenes (mono-, di-, tri-, tetra-, penta- and hexachlorobenzene).

6.   'Chlorophenols (sum)' here means the total of all chlorophenols (mono-, di-, tri-, tetra- and pentachlorophenol).

7.   In the case of the intervention value, 'polychlorobiphenyls (sum)' means the total of PCB 28, 52, 101, 118, 138, 153 and 180. For the target value it refers to the total excluding PCB 118.

8.   'DDT/DDD/DDE' above means the sum of DDT, DDD and DDE.

9.   'Drins' above means the sum of aldrin, dieldrin and endrin.

10. 'HCH compounds' above means the sum of α-HCH, β-HCH, γ-HCH and δ-HCB.

11. The intervention value applies to the sum of the concentrations of organotin compounds encountered.

12. 'Phthalates (sum)' above means the total of all phthalates.

13. 'Mineral oil' is defined in the analysis standard. Where the contamination is due to mixtures (e.g. gasoline or domestic heating oil), then not only the alkane content but also the content of aromatic and/or polycyclic aromatic hydrocarbons must be determined. This aggregate parameter has been adopted for practical reasons. Further toxicological and chemical disaggregation is under study.

14. The values for the sum  of polycyclic aromatic hydrocarbons, the sum of chlorophenols and the sum of chlorobenzenes in earth/sediment apply to the total concentration of the compounds belonging to the relevant category. If the contamination is due to only one compound of a category, the value used is the value for that compound. Where there are two or more compounds the value for the total of these compounds applies, etc. For earth/sediment, effects are directly additive (i.e. 1 mg of substance A has the same effect as 1 mg of substance B) and can be tested against an aggregate standard by summing the concentrations of the substances involved. In the case of groundwater, effects are indirectly additive and are expressed as a fraction of the individual intervention values (i.e. 0.5 of the intervention value of substance A has the same effect as 0.5 of the intervention value of substance B). This means that an addition formula must be used to determine whether an intervention value is exceeded. The intervention value for the sum of a group of substances is exceeded if:

ΣC_i/L_i≥1

where:     C_i = measured concentration of a substance in the group of substances in question

I_i    = intervention value for the group.

*numeric value below the detection level/quantification level or measurement method is lacking

# These target values have not been tested in HANS. All the other values have been tested in HANS.

^{^} The individual standards in INS are given in the Fourth Policy Document on Water Management along with the sum standards marked ^.

Table 2a:       Target values, indicative levels for serious soil contamination and background concentrations soil/sediment and groundwater for metals.Values for soil/sediment have been expressed as the concentration in a standard soil (10% organic matter and 25% clay).

Notes to Table 2

1.     Aromatic solvents are defined as a standard mixture of substances referred to as "C9-aromatic naphtha" as
defined by the International Research and Development Corporation: o-xylene 3.2%, i-isopropylbenzene 2,74%, n-propulbenzene 3.97%, 1-methyl-4 ethyl benzene 7,05%, 1-methyl-3-ethyl benzene 15.1%, 1-methyl-2-ethylbenzene 5,44%, 1,3,5-trimethylbenzene 8,37%, 1,2,4-trimethylbenzene 40,5%, 1,2,3-trimethylbenzene 6,18% and > ?? alkulbenzenes 6,19%.

2.     The indicative level is expressed on the basis of toxicity equivalents based on the most toxic compound.

*numeric value below the detection level/quantification level or measurement method is lacking

# These target values have not been tested in HANS. All the other values have been tested in HANS.

Supplementary remarks on tables 1 and 2

The target values, intervention values and indicative levels for metals and arsenic, with the exception of antimony, molybdenum, selenium, tellurium, thallium and silver depend on the clay content and/or the organic matter content. In assessing the quality of the soil the values for a standard soil are converted to values applying to the actual soil concerned on the basis of the measured organic material (measured by percentage weight lost by volatilisation, on the total dry weight of the soil) and clay content (the percentage by weight of the total dry material comprising mineral particle matter with a diameter of less than 2 ì m). The converted values can then be compared with the measured concentrations in the soil.

The following soil type correction formula can be used for the conversion for metals:

(SW,IW)_b = (SW,IW)_sb x [{ A+(Bx% clay (grain size< 2ìm ³)) + (Cx% organic matter)}/ {(A+(Bx25) +(CX10)}]

in which:

(S W, IW)_b              = target value or intervention value for the soil to be assessed

(S W, IW)_sb             = target value or intervention value for standard soil

% clay (grain size<2 ìm ³) = measured percentage clay (grain size<2 ìm ³) in the soil to be assessed

% organic matter = measured percentage organic matter in the soil to be assessed.

A, B, C                 = substance dependent constants for metals (see below)

Substance dependent constant for metals:

(SW,IW)_b = (SW,IW)_sb x (% organic matter/10)

in which:

(S W, IW)_b      = target value or intervention value for the soil to be assessed

(S W, IW)_sb             = target value or intervention value for standard soil

% organic matter   = measured percentage organic matter in the soil to be assessed. For soils with measured organic matter content of more than 30% or less than 2% contents of 30% and 2% are adhered to respectively.

in which:

(SW, IW)_b                = target value,intervention value for the soil to be assessed

% organic matter  = measured percentage organic matter in the soil to be assessed.

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