Section 3.5, while preliminary inputs to use in these calculations are detailed in Section 4.2. Releases may be accidental or intentional. Table 2.1 Storage release details Release point Release mechanism Control measure Container Spill due to piercing Spill kit, bunding Blending unit Spill kit, bunding Dam Wall failure dam construction guidelines Dam Overflow State dam construction guidelines Dam Leak through dam floor Lining Table 2.2 Use release details Release point Release mechanism Control measure Pipes Leaks Spill kit, bunding Blending unit Spill kit, bunding Wellhead Blowout Blowout preventer Transport accidents Truck accidents may occur at any point along a transport route to intermediate holding warehouses, individual well sites or re-use and disposal sites, potentially releasing single chemicals, chemical formulations or other coal seam gas waste products to the environment. Depending on the location of an accident, release may be direct to an aquatic receiving environment or indirectly from an accident occurring at some distance from an aquatic ecosystem (e.g. a lake or other wetland, stream, or river). In this latter case, release is direct to soil and subject to runoff and other fate pathways discussed in Section 2.4. Truck accidents are single events where the potential release at any location is limited to the carrying capacity of the truck. Control measures may contain the contents of a spill or reduce the quantity of chemical entering a pathway to an aquatic receiving environment. These include materials that contain the spillages and spill kits on trucks. Storage accidents Mishandling of containers stored at intermediate holding warehouses and individual wells may result in container failure and release to the environment of single chemicals or formulated products. Noting that some chemicals are reformulated, spills of intermediate blends may also occur on site. Examples of mishandling include accidental piercing of containers and spills during reformulation. The release to the environment of process fluids stored in lined formulation pits prior to their use, or of stored coal seam gas waste products, may arise due to dam wall failure, overflow of dams during rainfall events, and from leaks through the dam lining or floor.
Table 4.5 Values used in Exposure Equation 9 to determine the percentage of contaminant in runoff water Variable Tier 1 Tier 2 Tier 3 Ψ Precipitation (mm/day). To be determined. Values between 1 and 100 mm based on DSEWPaC (2009) and OECD (2000). Bounding estimate rainfall based on regional data. The probability of rain exceeding a certain value based on regional data will be used as described in Section 3.4.2. R Runoff (mm/day). To be determined by the methodology described above (Section 3.4.2) and verified using ANRA (2001). Regional data on soil types and hence curve numbers. Allow for variability of soil types within region. Heterogeneity factor Bounding estimate value of 1. Refined values 0.5 to 1 based on Dunne and Black (1970), Kuhn and Zhu (2008). No change Retention factor Depending on release scenario 0.5 to 1 (Linders et al. 2000; Willis et al. 1994). No change No change Transportsuspended contaminant 0 for contaminants with water solubility ≥ 1 mg/L (Grover 1989). % suspended sediment as calculated by Release Equation 4. No change 20% or 12.5% depending on scenario. 9%, 7.5% or 5% (Balmer and Frey 2001; OECD 2000) and available GIS data. Allow for variability of slopes within region. Buffer Default Value 1 (No effect). No change No change DT50soil Assume no degradation (DT50 = ∞; k = 0). Use bounding estimate DT50 value. Use more likely DT50 values, such as the geometric mean or 95th percentile. Koc Assume no affinity for soil (Koc = 0). Use bounding estimate Koc value. Use more likely Koc values, such as the geometric mean or 95th percentile.