Land Remediation

Protocols

Protocol: 4 Determining Background Soil Quality

Prepared pursuant to Section 53 of the

Contaminated Sites Regulation under the

Environmental Management Act

Protocol For Determining Background Soil Quality

1.0 INTRODUCTION

The Contaminated Sites Regulation provides a "release" as a contaminated site when the concentrations of substances at a site do not exceed local background levels. When assessing, remediating, or relocating contaminated soil, on site substance concentrations may be evaluated against background.

This protocol summarizes available regional background soil quality estimates for specified inorganic substances in British Columbia and provides procedures to establish background soil quality on a site-specific basis for use under the Contaminated Sites Regulation. This information may be used to decide contaminated site status, evaluate satisfactory remediation of contaminated sites and authorize contaminated soil relocation. The ministry does not recommend the direct quantification of local background concentrations at wide area sites (see section 5.2.3.1 below).

2.0 DEFINITIONS

Section 1 of the Contaminated Sites Regulation defines background as:

1 "background concentration" means the concentration of a substance in an environmental medium in a geographic area, but does not include any contribution from local human-made point sources, determined by following protocols approved by the director under section 53.

For the purposes of this protocol:

"local background concentration in soil" means the concentration in soil determined within a local geographical area, which can be attributed to natural and anthropogenic non-point sources, but does not include any contribution from anthropogenic point sources.

"regional background soil quality estimate" means a value for a substance, for a region, as listed in Table 1 of this protocol.

3.0 REGULATORY ASPECTS

The regulatory framework considering background concentrations can be found in Part 5, section 11(3) of the Contaminated Sites Regulation (CSR):

11(3) A site is not a contaminated site with respect to a substance in the soil, surface water or groundwater if the site does not contain any substance with a concentration greater than or equal to the local background concentration of that substance in the soil, surface water or groundwater respectively.

Section 11(3) denotes substance background concentrations determined on a local background (i.e. site-specific) basis. In addition, regional background soil quality estimates may also be considered equivalent to local background concentrations in soil for the purposes of section 11(3) of the regulation.

Section 17(2)(b) of the Contaminated Sites Regulation states that a contaminated site is considered to have been satisfactorily remediated if:

17(2)(b) the soil, surface water or groundwater at the site does not contain any substance with a concentration greater than or equal to the local background concentration of that substance in the soil, surface water or groundwater respectively.

Finally, section 45(3)(b) considers the deposit of contaminated soil at a deposit location to be acceptable if the contaminated soil does not contain any substance with a concentration exceeding:

45(3)(b) the local background concentration of that substance in the soil at the deposit site.

Regional background soil quality concentration estimates may also be considered equivalent to local background concentrations in soil for the purposes of section 17(2)(b) and 45(3)(b) of the regulation.

4.0 OVERVIEW

The ministry has considered background soil quality under the Contaminated Sites Regulation within a three stage approach.

In the first stage the site's substance concentrations are compared to the toxicologically-based CSR soil quality standards which, in the development of the regulation, were adjusted on the basis of provincial or lower mainland background soil quality estimates.

The second stage allows the use of regional background soil quality estimates as indicators of local background soil quality at sites located within any particular region.

The third stage allows the assessment of local background soil quality specific to the subject site using either:

(a) ministry reference data (or alternate reference data sources approved by the ministry) for the area, or

4.1.1 Initial Assessment of Site Status

Note the BC Environment Administrative Region in which the suspect contaminated site is located (Figure 1). Compare the soil quality (substance concentrations) measured at the site to the numerical soil standards of the Contaminated Sites Regulation. Exceedance of standards indicates the site is a contaminated site.

4.1.2 Consideration of Background Release

4.1.2.1 Stage 2: Regional Background Approach - Comparison to Table 2

A site may be released as a contaminated site based on regional background.

For the exceedances noted, compare the site's soil quality to the relevant 95^th percentile regional background concentrations, provided in Table 1. If the relevant Table 1 regional background concentrations are not exceeded, the site may be released as a contaminated site based on regional background.

4.1.2.2 Stage 3: Local Background Approach - Quantification of Local Background

A site may also be released as a contaminated site based on consideration of locally assessed background for the site. Local background is established by either:

i) comparing site exceedances to ministry data for local background within an area or locale, or other data pertaining to local background within an area or locale which has been approved for such use by a manager; or

ii) comparing site exceedances to local background concentrations quantified directly at a local background reference site approved by a manager.

If the relevant local background concentrations are not exceeded, the site may be released as a contaminated site.

5.1 Stage 2 Approach - Regional Background Estimates - General Procedure

The ministry has determined for each of its administrative regions within the province and for the Vancouver area, regional background soil quality estimates for 17 inorganic substances (Table 1). These regional background estimates represent, the 95th percentile value for a substance as described in reference 1.

In circumstances where site-specific local background soil quality has not been directly quantified for the site, the regional background soil quality estimates of Table 1 may be used as determinants of background soil quality for the site.

Table 1 regional background soil quality estimates are based on surficial or near surface soil samples obtained at BC Environment background sites (reference 1). Consequently, these regional background estimates may only be used as determinants of background soil quality to a maximum depth of 3m from the soil surface at a site. For sites with contamination at depths greater than 3m, background soil quality should be directly quantified using the stage 3 local background approach.

For sites located within the Vancouver area, the Vancouver area background soil quality estimates presented in Table 1 should be used as applicable regional background quality estimates. Sites located within BC Environment administrative region 2, which lie outside the Vancouver area, should use the region 2 background soil quality estimates of Table 1.

5.1.1 Deciding if a Site is a Contaminated Site or has been Satisfactorily

Remediated

Sites at which the soil quality for a specified substance exceeds an applicable CSR schedule 4 or 5 numerical soil standard, but does not exceed the corresponding

appropriate regional background soil quality estimate listed in Table 1, can be provided a release under section 11(3) or 17(2)(b) of the regulation. Otherwise, the site is deemed to be either a contaminated site or an unsatisfactorily remediated contaminated site.

5.1.2 Deciding if Contaminated Soil is Suitable for Relocation

Soil to be relocated from a contaminated site which exceeds, for a Table 1 specified substance, an applicable CSR schedule 4, 5 or 7 numerical soil standard, but does not exceed the corresponding appropriate regional background soil quality estimate for

the soil deposit location, can be considered acceptable for deposit at that location in accordance with section 45(3)(b) of the regulation. Otherwise, the soil quality standards of sections 45(2) or 45(3)(a) apply.

5.1.3 Other Substances

Table 1 provides regional background soil quality estimates for 17 inorganic substances only. The ministry does not plan to expand Table 1 beyond the current list of 17 substances. For substances not listed in Table 1, local background soil quality may be established directly using the procedures described in section 5.2 below.

5.1.4 Reporting Requirements

Responsible persons wishing to apply for release of their site or to relocate soil from their site on the basis of consideration of regional background soil quality estimates must submit to a manager, for review and approval the following information:

a) a site investigation report (i.e. a PSI or DSI) which fully characterizes the concentrations of contaminants present in the soil of the site per se, or in soil proposed to be relocated from the site,

b) identification of the BC Environment region or area in which the site is located, or in the case of proposed soil relocation, the region or area of the proposed deposit site,

c) a listing of applicable regional background soil quality estimates abstracted from Table 1 of this protocol, and

d) formal written request for release of the site under CSR section 11(3) or 17(2)(b) or approval to relocate soil under 45(3)(b).

5.2 Stage 3 Approach - Direct Quantification of Local Background Soil Quality

Responsible persons wishing to apply for release of their site under CSR section 11(3)

or 17(2)(b) or to relocate soil under section 45(3)(b) may elect to directly quantify site-specific local background soil quality for their site in accordance with the procedures detailed below.

5.2.1 General Procedures

Local background soil quality for a site may be established in either of two ways:

i) by use of ministry or other reference data pertaining to local background within an area or locale, which has been approved for such use by a manager, or

ii) by direct quantification of local background at a local background reference site approved by a manager.

5.2.2 Establishing Background based on ministry or other reference data

The data upon which the regional background soil quality estimates of Table 1 are based is available from the ministry. The ministry database is limited in regard to specific locales within administrative regions. However, in some circumstances this data may be sufficient to establish local background for some sites.¹ In addition, for some locales other non-ministry local background reference data may be available.

A responsible person for a site may therefore wish to investigate the possibility of establishing local background for their site based on such reference data, rather than directly assessing local background for their site through the reference site procedure. Where this is the case, a responsible person must provide a report for the approval of a manager detailing the source of the reference data used and presenting arguments to show that this data is relevant for the purposes of establishing local background for their site. The arguments presented in the report should provide information similar to that required under the reference site procedures (see below).

5.2.3 Establishing background based on data obtained at a reference site

Site-specific local background soil quality may be quantified directly through comparison to a carefully chosen reference background site. The emphasis in the reference site procedure is on accurate estimation of substance concentrations in soil which can be shown to be attributable solely to natural (i.e. non-anthropogenic) and generalized non-point anthropogenic sources. This is achieved by careful selection, analysis and comparison of reference site background soil substance concentrations to those observed at the contaminated site in question.

Selection of an appropriate reference site is critical to the accurate direct assessment of local background soil quality. The reference site must be shown to be free of any

possible anthropogenic point source influence with regard to the substances of concern identified for the contaminated site in question.

For example, urban areas have been subject to variable levels of anthropogenic non-point source contamination with lead as a result of generalized automobile emissions.

Thus, the soil of potential contaminated sites located within most urban areas would be expected to contain some amount of lead. In addition, at sites where lead was used in industrial or commercial activities, the soil may also contain additional lead as a result of point source contamination.

¹ Due to the small size of the data set, when ministry data is used, reference local background concentrations for a locale should be based on median as opposed to 95^th percentile estimates.

It is not the intent of the Contaminated Sites Regulation to dismiss, through the background release available under the regulation, the need to remediate contaminated sites which have been contaminated through point source release.

The procedure below quantifies local background soil quality directly through site-specific comparison to a local reference site. If the concentrations of substances in soil at the suspect or remediated contaminated site or in contaminated soil to be relocated, do not exceed substance concentrations established for the local reference site (i.e. the local background soil quality), then the site/soil is considered:

a) not to be a contaminated site under section 11(3), or
b) satisfactorily remediated under section 17(2)(b), or
c) acceptable for deposit under section 45(3)(b)

5.2.3.1 Wide Area Sites

Under the reference site procedure described below, it is necessary to closely match the contaminated site in question with a local reference site of suitable geographic area and scope. This is problematic in the case of contaminated sites which have been designated wide area sites under the regulation. Wide area sites tend to be large complex sites which typically encompass considerable geographic area. While it may be possible to select a reference site of sufficient size and scope to use in the direct assessment of local background soil quality for a wide area site, the sampling time, effort and analysis required to adequately characterize both the wide area contaminated site and its corresponding local wide area reference site would likely be prohibitively expensive.

For this reason, BC Environment does not recommend the direct determination of background soil quality for use at wide area sites. Rather, it is recommended that background soil quality at such sites be addressed through the use of BC Environment's stage 2 regional background soil quality estimates approach.

5.2.3.2 Reference Site Procedure - Local Reference Site Characterization

The reference site should closely match (i.e. be substantively similar to) the contaminated site in question in respect to:

a) geographical characteristics (e.g. location, topography, size/area, etc..),
b) soil physical/chemical characteristics (see soil maps, Geological Survey of Canada information, etc.),
c) hydrology, and

d) soil sampling depth.

Additionally:

a) within cities preference should be given to vacant land (land which has not received imported fill), naturally wooded areas, parks or large residential lots,

b) reference sites must not be located next to or within the general vicinity of contaminant point sources,

c) reference sites with any obvious vegetation damage should be avoided, and

d) the history of the reference site and adjacent land, including current and previous activities must be considered and documented.

5.2.3.3 Reference Site Information and Data Requirements - Site Soil Sampling and Chemical Analysis

Once a suitable local reference site has been located and if needed, permission to sample has been obtained, the following minimum information should be collected:

a) name and address of the property owner

b) current land use

c) surrounding land uses

d) any previous land uses (site history)

e) potential contaminant sources (both natural and anthropogenic)

f) latitude & longitude, and

g) a diagram of sampling plot locations within the overall property boundary.

Additional detailed information related to soil sampling methodology and the nature of the soil samples obtained at the reference site should also be documented. For example, additional information should be recorded concerning soil sample:

a) collection,

b) storage,

c) preparation,

d) archiving,

e) physical characterization, and

f) chemical analysis.

Sampling procedures and chemical analytical requirements differ for inorganic and organic substances. Soil sampling should be performed in accordance with ministry requirements (reference 3).

Ideally, soil samples taken from the reference site and the contaminated site in question should be subjected to identical analyses, using whenever possible, the same chemical analytical laboratory. Samples must be analyzed using BC Environment approved analytical methods, or alternate methods acceptable to the director (reference 4).

5.2.3.4 Reporting Requirements

Responsible persons wishing to apply for release of their site or to relocate soil from their site¹, on the basis of consideration of local background soil quality must submit to a manager for review and approval the following information:

a) a "Direct Determination of Local Background Soil Quality" report containing, at a minimum, details relevant to:

1. the choice or selection of the reference site,
2. the geographical location of the reference site (i.e. latitude and longitude, PIDs, etc..),
3. a complete history of landuse(s) at the reference site,
4. physical characterization of the reference site,
5. soil sampling procedures used,
6. soil sampling locations used (i.e. a map showing sampling locations),
7. soil depths sampled,
8. documentation of the soil contaminants of concern considered,
9. analytical results obtained,
10. the statistical significance of the results obtained, and
11. conclusions forthcoming from the assessment of reference site background

soil quality and the comparison of reference site background soil quality to the soil quality of the contaminated site in question.

b) identification of the BC Environment region or area in which the site is located, or in the case of proposed soil relocation, the region or area of the proposed deposit site, and

c) formal written request for release of the site under CSR section 11(3) or 17(2)(b) or approval to relocate soil under 45(3)(b).

 

1. All values are in ug/g unless otherwise stated. All values have been rounded in accordance with CSST rounding rule (reference 5). Values in brackets indicate that greater than 50% of values were less than the mean detection concentration MDC. for the substance, consequently tabled regional estimate is one-half MDC.

2. Each estimate represents the 95th percentile value obtained for a substance in the region or area.

3. Regional estimates are for the following BC Environment administrative regions:

   Region 1	Vancouver Island
   Region 2	Lower Mainland (includes Delta and Surrey)
   Region 3	Southern Interior Region (includes sub-region #3)
   Region 4	Kootenay (includes sub-region #4)
   Region 5	Cariboo
   Region 6	Skeena
   Region 7	Omineca-Peace(includes sub-region #5)

   
   
4. All soil samples, except those analyzed for mercury, were subjected to the Aqua Regia digestion method summarized in Appendix I.
5. Listed background soil quality estimates may be used as regional quality estimates within the Vancouver area only. Vancouver area includes, (see Figure 2 of this protocol) :
   

   Burnaby,
   Coquitlam,
   New Westminster,
   North Vancouver,
   Port Coquitlam,
   Port Moody,
   Richmond,
   West Vancouver, and
   Vancouver.

   
   
6. Soil samples for mercury analyses were subjected to the US EPA SW846 Method 7471 procedure summarized in.

    

Figure 1. Administrative Boundaries of BC Environment and Locations of Ministry Background Soil Study, Local Background Reference Sites.

Figure 2. Geographic Limits for Vancouver Area.

Appendix I. Summary of Aqua Regia Digestion Method

Reference soil samples used to develop Regional Background Soil Estimates were subjected to the following digestion procedure:

1. Dry soil samples at 60 ^{degrees C}, then sieve through a 100 mesh (150 um) screen, Weigh 0.3 g of the dried, meshed sample into a Teflon microwave digestion vessel, Add 4.5 mls Nitric Acid, 1.5 mls Hydrochloric Acid and 4 mls of DI water into the vessel, Digest in a microwave for 25 minutes under high pressure and 175 ^{degrees C}, Following digestion, bulk samples with DI water up to 50mls,
2. Assay sample, final Nitric Acid concentration is 9%, and final Hydrochloric Acid concentration is 3 %.

For further details of the Aqua Regia soil sample digestion procedure, contact Pacific Environmental Sciences Centre, North Vancouver, British Columbia.Appendix II. Summary of US EPA SW846 Method 7471 for MercuryReference soil samples used to develop Regional Background Soil Estimates for mercury were subjected to the following procedure:

1. Convert all forms of mercury in the soil sample to inorganic mercury using an acid-permanganate digestion of the air dried sample. Reduce inorganic mercury to its elemental state using SnCl₂. Measure mercury using cold vapour atomic absorption spectrophotometry at a wavelength of 253.7 nm. Analyses were completely automated using a Technicon autosampler coupled to a custom fabricated phase separator and detection using a Milton Roy Mercury monitor fitted with a 30 cm absorbance cell.
2. As a measure of the digestion and analysis efficiency, two SRM's were treated with every batch.

For further details of the mercury digestion/analysis procedure, contact Pacific Environmental Sciences Centre, North Vancouver, British Columbia.