Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p7
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 7/10)
Character Range: 163290–166176

residential), consideration should be given to collecting further data such as conducting a soil vapour survey of the source area.
The level of groundwater contamination present is of concern. The groundwater quality is unacceptable for human consumption and should be restricted for use by site occupants. Potable use is unrealistic given the poor groundwater quality and yield, however, it could cause adverse effects on potential ecosystem receptors. Further consideration should be given to groundwater contamination regarding any potential receptors off-site and any realistic future use potential. State and local groundwater protection policies would take effect in applying controls over the presence, extraction and use of impacted groundwater.
Note, it would not be an appropriate approach to install a thickness of fill to cover hydrocarbon contamination to enable the use of less stringent HSLs or to enable the application of a 'x10' or 'x100' biodegradation factor.

Case study 4: Application of soil vapour interim VOCC HILs and HSLs –

vapour intrusion assessment for a commercial building adjacent to industrial premises

Site Scenario
A drum reconditioning works is located beside a four-storey office building in an industrial estate. A drum pre-clean area attached to the works has leaked chemical wastes to the subsurface. Limited soil and groundwater sampling, constrained by existing infrastructure and land uses, have detected TCE, PCE and derivatives, BTEX and TRH fractions in soil and groundwater bores. Initial results suggested a potential human health risk to ground floor occupants of the office block. The surface of the site comprises sealed hardstand.
Response
The soil and groundwater sampling has been followed up with soil vapour samples at 01 m depth located in the bituminised area immediately adjacent to the office block at four locations to further assess the human health risk.
    * A preliminary screening step (refer Section 9.2.1 of Schedule B2) has determined that an assessment of potential vapour intrusion risks is necessary as receptors (occupants of office block) are located within 30 m of an identified volatile source.
    * The HSL assumptions and limitations were checked with the aid of the HSL checklist –(ASC NEPM Toolbox) and the HSLs confirmed to be applicable for the site-specific conditions.
    * BTEX and naphthalene were subtracted from TRH fractions C6 – C10 and >C10 – C16 to obtain F1 and F2 respectively (note F2 data not presented here).
    * Soil Type - Predominant soil type determined to be sand.
    * Biodegradation is not a consideration as the office block concrete slab and contiguous bituminised area is >15 m wide.
    *
Step 1: Document results and select interim VOCC HILs and soil vapour HSLs
Soil vapour values mg/m3, refer Table 1A(2) for interim VOCC HILs and Table 1A(5) for soil vapour HSLs