Buildings with Sub-Slab Ventilation Systems

For any building constructed with a sub-slab ventilation system per Section 3.1.2 of the Risk Management Plan, it would be necessary to undertake periodic monitoring of concentrations of contaminants of concern within the sub-slab ventilation system (e.g., soil vapours beneath the building slab that the ventilation system captures and directs to atmosphere, rather than intruding into the building).

Such monitoring would need to commence prior to building occupancy, and be completed on a quarterly basis for the first year and a semi-annual basis the second year and each successive year until such time as MECP agrees to remove or alter the vapour monitoring program requirement. It is expected that vapour monitoring would be required for a minimum period of two years (i.e., at least six monitoring events).

The vapour monitoring program shall be developed and overseen by a Qualified Person per Section 5 or Section 6 of O. Reg. 153/04 (a “QPESA” or “QPRA”, respectively), with consideration given by the Qualified Person to collecting outdoor air sampling locations.

The vapour sampling program should be designed and completed with consideration of the guidelines and recommendations outlined in the MECP Draft Technical Guidance document. Sampling methodology and laboratory analyses shall be completed in accordance with MECP guidelines/protocols, as well as the requirements outlined below.

Each recovered sample is to be analysed for the parameters which the Risk Assessment has identified potential concerns regarding “soil to indoor air” or “groundwater to indoor air” exposure pathways, and which are outlined in Table H-3. Alert criteria for each parameter in soil vapour (i.e., recovered from sub-slab vapour sampling ports of a sub-slab ventilation system) is also provided in the table.

During each sampling event, “whole air” samples should be collected from each established monitoring port and at each outdoor sampling location, typically using stainless steel electropolished (or “summa” polished) passivated vessels equipped with twenty (20) minute sampling interval regulators. (Samples for mercury analyses will need to be collected using hopcalite or equivalent sorbent tubes. Sampling methodologies for heptachlor and hexachlorobenzene will need to be determined at the time of sampling efforts in consultation with the local district office of MECP, as Canadian laboratories are not currently accredited to complete such analyses.)

Sampling methodology and laboratory analyses should be completed in accordance with MECP guidelines/protocols (e.g., in accordance with US EPA method TO-15, or a variance of that method for parameters such as PHC subfractions, and NIOSH method 6009 for mercury).

TABLE H-3: Soil Vapour and Indoor Air Alert Criteria

Parameter Units Alert Criteria

Soil Vapour Indoor Air

Benzene µg/m³ 2.53E+01 5.06E-01

Bromomethane µg/m³ 5.21E+01 1.04E+00

Carbon tetrachloride µg/m³ 2.09E+01 4.17E-01

1,4-Dichlorobenzene µg/m³ 1.39E+01 2.78E-01

1,2-Dichloroethane µg/m³ 2.14E+00 4.28E-02

1,1-Dichloroethylene µg/m³ 7.30E+02 1.46E+01

1,2-Dichloropropane µg/m³ 4.17E+01 8.34E-01

1,3-Dichloropropene µg/m³ 1.39E+01 2.78E-01

Ethylene dibromide µg/m³ 9.27E-02 1.85E-03

Heptachlor µg/m³ 3.85E-02 7.69E-04

Hexachlorobenzene µg/m³ 1.09E-01 2.17E-03

Hexane µg/m³ 2.61E+04 5.21E+02

Mercury µg/m³ 9.40E-01 1.88E-02

PHC F1 Aliphatic C6 - C8 µg/m³ 4.80E+05 9.59E+03

PHC F1 Aliphatic C>8 – C10 µg/m³ 2.61E+04 5.21E+02

PHC F1 Aromatic C>8 – C10 µg/m³ 5.21E+03 1.04E+02

TABLE H-3: Soil Vapour and Indoor Air Alert Criteria

Parameter Units Alert Criteria

Soil Vapour Indoor Air

PHC F2 Aliphatic C>10 – C12 µg/m³ 2.61E+04 5.21E+02

PHC F2 Aliphatic C>12 – C16 µg/m³ 2.61E+04 5.21E+02

PHC F2 Aromatic C>10 – C12 µg/m³ 5.21E+03 1.04E+02

PHC F2 Aromatic C>12 – C16 µg/m³ 5.21E+03 1.04E+02

1,1,1,2-Tetrachloroethane µg/m³ 7.51E+00 1.50E-01

1,1,2,2-Tetrachloroethane µg/m³ 9.59E-01 1.92E-02

Tetrachloroethylene µg/m³ 2.14E+02 4.28E+00

1,1,2-Trichloroethane µg/m³ 3.48E+00 6.95E-02

Trichloroethylene µg/m³ 1.36E+01 2.71E-01

Vinyl chloride µg/m³ 6.32E+00 1.26E-01

Xylenes µg/m³ 7.30E+03 1.46E+02

Alert criteria are also provided in Table H-3 for indoor air sampling results; however, indoor air sampling is only intended to be completed within a building as a possible contingency measures (e.g., if one or more of the soil vapour sampling results applicable to the building exceeds the corresponding alert criteria):

• Should any soil vapour sampling result exceed the soil vapour alert criteria specified in Table H-3, a confirmatory soil vapour sample will be recovered and submitted for laboratory analyses within 15 days;

• If the confirmatory soil vapour sampling result also exceeds the alert criteria specified in Table H-3, the Qualified Person shall expand the vapour monitoring program to include the collection of indoor air samples from the affected building(s):

 The number and location of indoor air sampling points will be determined considering building layout, building size, and potential vapour intrusion points;

 Indoor air sampling will also include the collection of outdoor air sampling locations;

 “Whole air” samples will collected at each sampling location using stainless steel electropolished passivated vessels equipped with eight (8) hour sampling interval regulators;

 The initial indoor air sampling program will take place within 15 days of receipt of laboratory results for the confirmatory soil vapour sampling; and,

 Future indoor air sampling events for the affected building(s) will occur concurrently with soil vapour sampling events, and shall continue so long as the vapour sampling program is required at the Site.

Should any indoor vapour sampling result exceed the indoor air alert criteria specified in Table H-3, the Qualified Person shall provide written notification to MECP within thirty (30) days, along with a description of the significance of the result, any measures taken as a

result (e.g., confirmatory indoor air sampling), and any contingency measures planned as a result. Such contingency measures could include converting the sub-slab venting system to an active venting installation through connecting the vent risers to regenerative blowers in place of using wind-driven turbines, adjusting percentage of fresh air intake of the building heating/ventilation system, a combination of these measures, or a similar approach. Regardless, the Owner, the Qualified Person, and MECP shall collaboratively determine the contingency measures warranted at the Site and the Owner shall implement these measures forthwith.

With the exception of heptachlor and hexachlorobenzene, the indoor air alert criteria reported in Table H-3 have been adopted from the “Health Based Indoor Air Criteria – Residential” entries on the “Human Health” tab of the 2016 MECP Approved Model (PIBS 7381e01, dated November 1, 2016). Heptachlor and hexachlorobenzene indoor air alert criteria have been adopted from the Inhalation Unit Risk factors selected for these parameters (1.3 (mg/m³)^-1 and 0.46 (mg/m³)^-1, respectively, per Appendix G of the Risk Assessment) and a target incremental lifetime cancer risk of 10^-6.

Soil vapour alert criteria in Table H-3 have been determined by applying an attenuation factor of 50 (α = 0.02) to the identified indoor air alert criteria.

Consideration of Typical Laboratory Reporting Limits: It should be noted that for some parameters, the typical reporting detection limits for air samples that are currently provided by commercial laboratories are greater than the risk-based Alert Criteria adopted within the RMP. Typical laboratory reporting limits are provided in Table H-4, along with the Soil Vapour and Indoor Air Alert Criteria adopted within the RMP.

TABLE H-4: Comparison of Soil Vapour and Indoor Air Alert Criteria to Typical Reporting Limits

Parameter Units

Soil Vapour Indoor Air

Alert Criteria

Typical Laboratory

Reporting Limits

Alert Criteria

Typical Laboratory

Reporting Limits

Benzene µg/m³ 2.53E+01 3.00E-01 5.06E-01 1.60E-01

Bromomethane µg/m³ 5.21E+01 4.00E-01 1.04E+00 1.90E-01

Carbon tetrachloride µg/m³ 2.09E+01 6.00E-01 4.17E-01 3.10E-01

1,4-Dichlorobenzene µg/m³ 1.39E+01 6.00E-01 2.78E-01 3.10E-01

1,2-Dichloroethane µg/m³ 2.14E+00 4.00E-01 4.28E-02 4.00E-02

1,1-Dichloroethylene µg/m³ 7.30E+02 4.00E-01 1.46E+01 2.00E-01

1,2-Dichloropropane µg/m³ 4.17E+01 5.00E-01 8.34E-01 2.30E-01

1,3-Dichloropropene µg/m³ 1.39E+01 5.00E-01 2.78E-01 2.30E-01

Ethylene dibromide µg/m³ 9.27E-02 8.00E-01 1.85E-03 8.00E-02

Heptachlor µg/m³ 3.85E-01 TBD 7.69E-03 TBD

Hexachlorobenzene µg/m³ 1.09E+00 TBD 2.17E-02 TBD

Mercury µg/m³ 9.40E-01 n/a 1.88E-02 n/a

PHC F1 Aliphatic C6 - C8 µg/m³ 4.80E+05 5.00E+00 9.59E+03 5.00E+00 PHC F1 Aliphatic C>8 – C10 µg/m³ 2.61E+04 5.00E+00 5.21E+02 5.00E+00 PHC F1 Aromatic C>8 – C10 µg/m³ 5.21E+03 5.00E+00 1.04E+02 5.00E+00 PHC F2 Aliphatic C>10 – C12 µg/m³ 2.61E+04 5.00E+00 5.21E+02 5.00E+00 PHC F2 Aliphatic C>12 – C16 µg/m³ 2.61E+04 5.00E+00 5.21E+02 5.00E+00

Parameter Units

Soil Vapour Indoor Air

Alert Criteria

Typical Laboratory

Reporting Limits

Alert Criteria

Typical Laboratory

Reporting Limits PHC F2 Aromatic C>10 – C12 µg/m³ 5.21E+03 5.00E+00 1.04E+02 5.00E+00 PHC F2 Aromatic C>12 – C16 µg/m³ 5.21E+03 5.00E+00 1.04E+02 5.00E+00 1,1,1,2-Tetrachloroethane µg/m³ 7.51E+00 7.00E-01 1.50E-01 1.40E-01 1,1,2,2-Tetrachloroethane µg/m³ 9.59E-01 7.00E-01 1.92E-02 2.00E-02

Tetrachloroethylene µg/m³ 2.14E+02 7.00E-01 4.28E+00 3.40E-01

1,1,2-Trichloroethane µg/m³ 3.48E+00 5.00E-01 6.95E-02 7.00E-02

Trichloroethylene µg/m³ 1.36E+01 5.00E-01 2.71E-01 2.70E-01

Vinyl chloride µg/m³ 6.32E+00 3.00E-01 1.26E-01 5.00E-02

Xylenes µg/m³ 7.30E+03 9.00E-01 1.46E+02 4.30E-01

BOLD Alert Criteria is less than the typical laboratory reporting limit

n/a not applicable – sample collected using sorbent tube; effective detection limit determined by sampling volume TBD Canadian laboratories are not currently accredited for this analysis; consultation required prior to sampling efforts

Soil vapour and indoor air sampling events should include reasonable efforts (e.g., consultation and collaboration with the contract laboratory) to mitigate limitations that laboratory reporting limits may impose on the evaluation of analytical results. When such efforts are undertaken, the absence of a quantifiable concentration of a parameters within a soil vapour or indoor air sample but at a reporting limit greater than the soil vapour or indoor air alert criteria (as applicable) will not be considered a contingency plan trigger.