Bengalla Mine Environmental Impact Statement (1993) - Part 1 of 3

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2.7.2 Existing Air Quality
Apart from gauges D4 (the anomalous gauge), D12B, D12C and D15, the general dust fallout levels are low -
between 1 and 2 g/m 2 /mth (long-term averages). Gauge D15 is near the Muswellbrook - Ulan Railway and
appears to be monitoring a local source of dust. Gauge D16 to the west, records long-term averages of 0.9 to
1.4 g/m 2 /mth. Gauges 12A, 12B and 12C are on the river flats and have slightly elevated dust fallout levels
(between 2.0 and 3.0 g/m 2 /mth (long-term averages)) due probably to agricultural activity. Apart from the areas
near gauges D12A, D12B and D12C the appropriate increment in annual average dust fallout is then 2.0
g/m 2 /mth. Near D12A, D12B and D12C, the acceptable increment is 1.0 g/m 2 /mth (annual average). (Strictly,
if a total deposition level of 4 g/m 2 /month (annual average) is acceptable then increments of slightly more than
2.0 g/m 2 /month (annual average) would be acceptable).
Monthly averages of total suspended particulate 24-hour concentrations (TSP) are shown in Table 2.6.
Excluding one 24-hour average concentration of 433 due to the ploughing of a nearby paddock, 24-hour
concentrations have been between 3 to 110 µg/m 3 (raw data). Taking account of the fact that these
measurements are of TSP concentrations and that PM 10 (particles less than 10 µm) concentration would be
expected to be approximately half the TSP concentrations, it is clear that concentrations over the monitoring
period have been well within the EPA's PM 10 goal of 150 µg/m 3 (24-hour average). Annual average TSP
concentrations (1992) have been 35, 40, 35 and 40 µg/m 3 for gauges HV1, HV2, HV3 and HV4 respectively.
Data so far available for 1993 indicate that similar concentrations will apply in 1993 as for 1992. These are
well within the NH&MRC annual average goal of 90 µg/m 3 for TSP and using a factor of 50 per cent for the
PM 10 to TSP ratio, the annual average PM 10 is below the EPA goal of 50 µg/m 3 . The acceptable annual average
TSP increment would then be approximately 40 µg/m 3 .
BENGALLA EIS. F156
NOVEMBER 1993