Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:6:p5
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 6 (pt 5/10)
Character Range: 191089–194635

vapour source concentration for a petroleum mixture could not exceed a level that would result in the maximum allowable vapour risk for the given scenario. For these scenarios, no HSL is presented for these chemicals and the HSL is shown as 'not limiting' or 'NL'.
  (6)     The HSLs for TPH C6-C10 in sandy soil are based on a finite source that depletes in less than seven years, and therefore consideration has been given to use of sub-chronic toxicity values. The >C8-C10 aliphatic toxicity has been adjusted to represent sub-chronic exposure, resulting in higher HSLs than if based on chronic toxicity. For further information refer to Section 8.2 and Appendix J in Friebel and Nadebaum (2011a).
  (7)     The figures in the above table may be multiplied by a factor to account for biodegradation of vapour. A factor of 10 may apply for source depths from 2 m to <4 m or a factor of 100 for source depths of 4 m and deeper. To apply the attenuation factor for vapour degradation, a number of conditions must be satisfied. Firstly the maximum length of the shorter side of the concrete slab and surrounding pavement cannot exceed 15 m, as this would prevent oxygen penetrating to the centre of the slab. Secondly, measurement of oxygen in the subsurface is required to determine the potential for biodegradation. Oxygen must be confirmed to be present at >5% to use these factors.

  (8)     For soil texture classification undertaken in accord with AS 1726, the classifications of sand, silt and clay may be applied as coarse, fine with liquid limit <50% and fine with liquid limit>50% respectively, as the underlying properties to develop the HSLs may reasonably be selected to be similar. Where there is uncertainty, either a conservative approach may be adopted or laboratory analysis should be carried out.

  (9)     To obtain F1 subtract the sum of BTEX concentrations from the C6-C10 fraction.

  (10)  To obtain F2 subtract naphthalene from the >C10-C16 fraction.

Table  1A(4) Groundwater HSLs for vapour intrusion (mg/L)
              HSL A & HSL B                   HSL C                      HSL D
              Low – high density residential  recreational / open space  Commercial / industrial
CHEMICAL                                                                                                                                                                                     Solubility limit
              2 m to <4 m                     4 m to <8 m                8 m+                     2 m to <4 m  4 m to <8 m  8 m+       2 m to <4 m       4 m to <8 m       8 m+
SAND

Toluene       NL                              NL                         NL                       NL           NL           NL         NL                NL                NL                61
Ethylbenzene  NL                              NL                         NL                       NL           NL           NL         NL                NL                NL                3.9
Xylenes       NL                              NL                         NL                       NL           NL           NL         NL                NL                NL                21
Naphthalene   NL                              NL                         NL                       NL           NL           NL         NL                NL                NL                0.17
Benzene       0.8                             0.8                        0.9                      NL           NL           NL         5                 5                 5