screening level risk assessment (slra) update csr stage …

SCREENING LEVEL RISK ASSESSMENT (SLRA) UPDATE

CSR STAGE 11 AMENDMENT WEBINAR #6 DECEMBER 5, 2017 GEORGE SZEFER Senior Contaminated Sites Officer

This PowerPoint presentation and a recording of the audio will be posted on the web following the webinar

OUTLINE

• Refresher

• Summary of Changes (majority of presentation)

• Example Calculations using GPM

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WHAT IS SLRA • A simple screening assessment tool. • Assess whether contamination poses acceptable or unacceptable

risks to human health or environment. • Based on assessment of the presence/absence of exposure pathways

and receptors. • A risk-based approach eligible for a certificate of compliance (risk-

based standards). • No further remediation required as long as site conditions do not

change.

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WHEN CAN YOU USE SLRA • After characterizing site conditions and determining the

nature/degree/extent of contamination (soil, groundwater, sediment, surface water)[DSI].

• May be used pre or post-remediation. • Non high risk sites (high risk sites subject to Director’s decision). • Some substances/conditions and pathways precluded from

assessment (precluding conditions). • Exemption for beneficial use contamination. • Voluntary similar to Protocol 2.

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PRECLUDING CONDITIONS (HIGH RISK, SUBSTANCES, MEDIA)

• Director’s decision required to apply at high risk sites.

• Inorganic substances in soil or groundwater with pH<5. • Bioaccumulative substances. • Contaminated vapour. • Contaminated sediment/surface water (except where contamination

qualifies under beneficial use exemption). • Mobile NAPL (implicit through high risk restriction).

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PRECLUDING CONDITIONS (PATHWAYS)

• Deep rooting plants or trees in areas of soil or groundwater contamination (prescribed land uses only).

• Very high permeability soil or complex hydrogeologic units. • Preferential pathways that transport contaminated groundwater to a

receiving environment or water well. • Groundwater contamination that extends beyond a source parcel

boundary and is not demonstrated to be stable or decreasing. • Screening of pathways not specifically identified (e.g., chronic

occupational exposure pathways for subsurface workers).

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BENEFICIAL USES

• Zinc localized around galvanized materials. • Copper localized around copper pipe/wire. • Prescribed substances localized around treated or preserved wood

utility poles, structural timber or pilings. • Road salting.

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SLRA PROCESS

• Problem formulation/CSM.

• Check for requirements, precluding conditions, exemptions.

• Evaluate exposure scenarios.

• Determine risk.

• Reporting.

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SUMMARY OF CHANGES

Summary of changes between 200808 V2 and 201711 V3 • *Major changes but many others in document – conduct careful read

of entire document!*

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NEW 2017 Nov V3

OLD 2008 Aug V2

PRIMARY CHANGES FROM 201707 DRAFT

201707 Draft Version (Stakeholder review document): Section 3.2 Precluding Condition: • groundwater contamination that extends beyond a source parcel boundary.

Section 6 Director’s Approval of Alternate Screening Methods • …where plume stability has been demonstrated…and contaminant migration

beyond the property boundary has not and will not occur…request a Director to approve the groundwater contaminant transport pathway assessment component of SLRA (Appendix A).

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PRIMARY CHANGES FROM 201707 DRAFT

201711 Version 3 (changes in red from 201707 draft) Section 3.2 Precluding Condition: • groundwater contamination that extends beyond a source parcel boundary

and is not demonstrated to be stable or decreasing (see Section 6).

Section 6 Plume Stability • …where plume stability has been demonstrated…completion of the

groundwater contaminant transport pathway assessment component of SLRA (Appendix A) is not necessary.

• Director’s decision no longer necessary.

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NET RESULT OF PRIMARY CHANGES FROM 201707 DRAFT

Section 3.2/Section 6/Appendix A: • If plume is stable, whether within or beyond parcel boundary, not necessary

to complete Appendix A (soil leaching/solute transport assessment) as per s6.

• If plume is not stable, and contamination within parcel, conduct transport assessment as per Appendix A:

• transport prediction to water well or 10 m from high water mark of receiving environment on the parcel, or, transport prediction to parcel boundary, whichever is lesser.

• If plume is not stable, and contamination extends beyond source parcel,

precluded from assessment in SLRA as per s3.2.

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SUMMARY OF CHANGES FROM ORIGINAL 200808 V2

General • Majority of changes to pathway/transport assessment components -

primary objectives: • Harmonization with Protocol 28, Protocol 2, Protocol 27, other protocols and

technical guidance documents • General update/cleanup

• Limited ecological component changes (e.g., habitat assessment, receptor species assessment).

• Use GPM (manual calculation not necessary). • As provided in Technical Guidance 13

• Director’s advice re: NAPL not present (removed as superseded by Protocol 16).

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S3.1 Requirements (New section)

• Created to consolidate various protocol requirements into one section.

• Based on DSI (no change). • Application limited to those substances listed in Table A-1, App A.

• Expanded to 158 substances from 141

• Application at agricultural land use sites no longer requires Director’s decision.

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S3.2 Precluding Conditions

• Section reworked to specify substances/media and pathways that are precluded.

• Application at high risk sites requires Director’s decision (no change).

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S3.2 Precluding Conditions (substances/media)

• Ionizing organic substances added to Table A-1. • No longer precluded.

• Acidic site media preclusion (pH<5). • Now includes both soil and groundwater (groundwater added).

• Bioaccumulative substances. • Precluded irrespective of depth (previously within top 1 m of soil).

• Presence of NAPL preclusion removed. • Mobile NAPL preclusion is implicit through high risk site preclusion.

• Vapour contamination – not possible to screen in SLRA. • Follow P24, TG4, proceed to DRA, as necessary.

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S3.2 Precluding Conditions (pathways)

• Presence of deep-rooting plants and trees (soil exposure assessment pathways precluded).

• Now applies in areas of soil or groundwater contamination (groundwater added). • Limited to wildlands (natural or reverted), agricultural or low density residential

land uses.

• Presence of groundwater contamination beyond parcel boundary and

not stable (groundwater transport assessment pathways precluded). • See earlier slides.

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S3.3 Beneficial Use Exemption

• Restructured to align with Administrative Guidance 15.

• Expanded offset distance to 3 m (previously 1 m).

• Refocussed wood treatment exemption wording.

• Added road salting as beneficial use.

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S4.1 Problem Formulation

• Conceptual site model as graphic or flowchart (box model). • Included wording about identifying risk management measures and

exposure pathways addressed outside of SLRA. • Added contaminant source area definition - where substance

concentration in soil exceed applicable: • Generic/matrix numerical standards; • Site-specific numerical standards; or • Background concentrations.

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S4.3 Evaluation of Potential Exposure Scenarios

• More explicit wording of potentially harmful concentrations - substance concentrations that exceed, in soil or groundwater, as applicable:

• Generic/matrix numerical standards (Sch 3.1, Parts 1-3, Sch 3.2); • Site-specific numerical standards (P2, P10); or • Background concentrations (P4, P9).

• Vapour pathway removed. • Expanded wording about assessment of exposure pathways/scenarios

not specifically identified in SLRA, e.g., subsurface workers. • Cleanup or assess using DRA.

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S5.0 Reporting

• Principal author(s) and registered professional biologist, as applicable (habitat assessment).

• Adding wording about any precluding conditions and how addressed outside of SLRA.

• Added wording on specification of any risk controls to be included in a PVP

• Added requirement to satisfy Protocol 27 reporting requirements if leachate testing undertaken as part of Appendix A.

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S6.0 Plume Stability (previously Alternative Methods) • Requirements to demonstrate plume stability. S7.0 Director’s decision of Alternative Methods (new) • Site-specific parameter values outside the parameter ranges provided

in the protocol or GPM; or • Site-specific parameter values instead of the default values provided

in the protocol or GPM. • Harmonization with changes to P2.

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QUESTIONS ?


Appendix A (Soil Leaching/Groundwater Transport Assessment) • Potential for contaminated groundwater, as may result from

predicted soil leaching or actual contaminated groundwater, within a source area, to migrate to a downgradient point of compliance.

• Use GPM from TG13.

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• Consult P28, Chapter 4 for GPM derivation information.

• GPM used with forward calculation (source to point of compliance). • Equations separated from text to improve readability.

• Equations updated to match P28.

• Only used where plume within parcel and plume not stable.


S1.0 App A (Predicted Soil Leachate Concentrations)

• Harmonized default values with P28. • Porosity terms, bulk density, fraction organic carbon.

• Source dimensions determined following P2 or applicable standards. • Leaching tests changed to match P27. Follow sections 4 through 6 of

P27 for substances/soil sample selection requirements. • Inorganics:

• Leaching test for all substances except cyanide.

• Organics: • Leaching test for select substances (added). • Partitioning equation.

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S1.0 App A (Predicted Soil Leachate Concentrations)

• Inorganics: • “Liquid-Solid Partitioning (Leachability) as a Function of pH (Metals, Inorganics,

and SVOCs) – Prescriptive” (BC Soil Leachate Test). • “Saturated Paste Extraction for Soils” for chloride ion, sodium ion. • Use partitioning equation for cyanide.

• Organics:

• “Liquid-Solid Partitioning (Leachability) of VOCs – Prescriptive”. • BC Soil Leachate Test. • Partitioning equation.

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S2.0 App A (Predicted Soil Leachate Concentrations at Water Table)

• Unsaturated zone transport added - harmonization with P2.

• Use site-specific source depth (Z) and infiltration rate (I) - follow requirements laid out in P2.

• Biodegradation rates now active for unsaturated transport. • Organics: use prescribed half-life values, if no value provided, use a long half-life. • Inorganics: distribution coefficients (Kd) provided but sorption negated by steady-

state transport solution.

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S3.0 App A (Predicted Groundwater Concentrations in Saturated Zone)

• Mixing equation changed – harmonized with P28. Use for all water use pathways:

• Previous Dilution Factor (DF) of 20 for DW, IW and LW pathways no longer used.

• Use site-specific source length (X) and infiltration rate (I) - follow requirements laid out in P2.

• DF=1 constraint retained (consistent with P2): • Where source extends into the water table.

• Mixing zone thickness constraint added (consistent with P2): • Where calculated mixing thickness exceeds aquifer thickness, mixing thickness set

equal to aquifer thickness

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S4.0 App A (Predicted Groundwater Concentrations at Point of Compliance) • Changed point of compliance (formerly receptor):

• Water well or 10 m from high water mark of receiving environment on the parcel, or, parcel boundary, whichever is lesser (previously just for DW pathway).

• Changed maximum transport distance to 500 m (same as P2). • Biodegradation rates:

• Organics: use prescribed half-life values, if no value provided, use a long half-life. • Inorganics: distribution coefficients (Kd) provided, although sorption negated by

steady-state transport solution, some attenuation available from lateral dispersion. • No changes:

• transport solution (2D ss). • minimum average linear velocity constraint (5 m/yr). • use of maximum of predicted groundwater concentration and actual groundwater

concentration.

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Table A-1 App A (Substance Properties) • Revised to match Stage 10 CSR substance naming convention/listing:

• 158 substances (previously 141). • Added inorganics from P28 and Sch 3.2, culled substances without water use

standards. • Added chlorophenols (ionizing organics):

• CP, 2-, CP, 3-, CP, 4-, DCP, 2,3-, DCP, 2,4-, DCP, 2,5-, DCP, 2,6-, DCP, 3,4-, PCP, T4CP, 2,3,4,5-, T4CP, 2,3,4,6-, T3CP, 2,4,5-, T3CP, 2,4,6-

• Updated substance properties – harmonized with P28: • Koc, H’ from Risk Assessment Information System (RAIS). • Chlorophenol Koc’s from EPA Soil Screening Guidance (SSG). • Kd’s from EPA SSG or RAIS.

• Updated biodegradation rates (from Axiom): • Values for 27 substances (previously 8).

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Table A-2 App A (pH/Koc Isotherms)[New] • Select chlorophenols:

• Koc values to soil pH=8 (values calculated/extended to pH=9)

Table A-3 App A (Kd Values)[New] • For inorganics listed in Table A-1.

Table A-4 App A (pH/Kd Isotherm for Thallium)[New] • Included following removal of Thallium from Sch3.1, Part 1 and

therefore P28.

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Others

• Questionnaire: • Extensive changes to questions and notes – review carefully!

• “no” response, soil wicking, subsurface worker exposure assessment, water pathway wording, exceedance of standards, CSR schedule references…

• Forms/Figures:

• Wording/terminology changes based on overall protocol changes, CSR land use term changes, harmonize with P28/P2…

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QUESTIONS ?

SAMPLE CALCULATIONS USING GPM

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SAMPLE CALCULATIONS - BENZENE

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SAMPLE CALCULATIONS - BENZENE

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QUESTIONS ? GEORGE SZEFER

[email protected] OR (604) 582-5200

Advice provided during this webinar is based on information available at the time of recording and may

be subject to change.

This PowerPoint presentation and a recording of the audio will be posted on the web. If you do not wish

your question to be on the public record, please email the presenter following the webinar.

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