HVO 2009 Annual Environmental Management Report - Final

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Coal & Allied – Hunter Valley Operations reported in the Annual Return (see Appendix 15). The leak was immediately blocked and a barrier installed to prevent flow of discharge water further downstream. Incident 1000042150 On Saturday 4 April 2009 a hole was discovered in the embankment of Dam 15N. The hole in the embankment developed as a result of a small leak in the pipeline that runs through the dam wall to supply water to the pumping infrastructure. It was apparent that water from Dam 15N had been leaking through the hole in the pipeline and seeping through the embankment and into Farrells Creek. Dam 15N is situated in the headwaters of a tributary of Farrells Creek. At the time the hole was discovered only seepage was evident, at a rate estimated at 1-2L/s. Farrells Creek was flowing at the time in a week were the site had more than 150mm of intense rainfall. Dam 15N is a storm buffer dam for the CHPP and reached about 75 per cent from the rainfall runoff. At this stage water in the dam would have been higher than the pipeline, thus resulting in a small leak in the pipeline and subsequent seepage from the area. Dam 15N was in the process of being emptied when the leak was discovered. Water quality sampling showed that the leak had not deteriorated the quality of the creek water, and no actual or material pollution occurred, hence the incident was not immediately notified to the DECCW. However the dam is not a licensed discharge point under the HRSTS so the leak was reported in the Annual Return (see Appendix 15). Dam 15N is maintained empty to allow 1 in 100 year storm buffer capacity for the CHPP and Maintenance area. Incident 1000045546 On Tuesday 26 May 2009 a review of water sampling results indicated that a clean water diversion dam (Dam 18W) had elevated electrical conductivity. Dam 18W is designed to passively spill to Parnells Creek via an engineered spillway. Dam 18W is located on HVO’s western boundary and is a settling basin for the main western clean water diversion. Approximately 2.5 square kilometres of clean catchment is diverted into Dam 18W. Parnells Ck is an ephemeral creek draining to the Hunter River. Due to rainfall, approximately 30L/s was estimated to be flowing over the Dam 18W spillway. Water quality was tested on the 28 May 2009 upstream and downstream of the confluence of Parnells Creek in the Hunter River. Results showed that electrical conductivity was falling downstream of the confluence. Actions were implemented to drain water from Dam 18W into Parnells Dam to reduce and stop the flow over the spillway. Initial investigation determined that there were two sources of saline water entering Dam 18W. A natural saline seepage and a seepage path from the West Pit (Bobs Dump) Tailings Dam. Further investigation determined that a seepage from the Bobs Dump Tailings Facility was not the main source of salinity in Dam 18W. The contribution of salts from the tailings facility seep is not sufficient to elevate the salinity of Dam 18W to a measured electrical conductivity of 3mS/cm. A natural saline seepage was recording saline values up to five times the levels recorded in Bobs Dump Tailings Dam. Since the incident Coal & Allied has isolated the tailings facility seepage from the Dam 18W catchment. Dam 18W has been pumped and drained into Parnells Dam to mitigate water overflowing the Dam 18W spillway. Incident 1000047847 On Monday 6 July 2009 a blast at HVO Cheshunt Pit was initiated at 10:18am. Overpressure results of 122.4dB(L) and 120.7dB(L) at Maison Dieu and Warkworth respectively, and 116.9dB(L) at Wandewoi were recorded. The EPL states that airblast overpressures from blasts carried out on site should not exceed 120dB(L) at any time. An independent investigation by Terrock Pty Ltd determined that at the time of the blast an atmospheric inversion was present. The EnvMet model used by Terrock predicted an increase of between 5dB(L) and 15dB(L) over normal emission levels during this period. In addition to the inversion one hole in the blast pattern released energy upwards out of the hole instead of transmitting it through the rock strata. This was determined to be a result of the small ground movement AEMR 2009 149
Coal & Allied – Hunter Valley Operations (relief) of the blast design. Under normal atmospheric conditions this is unlikely to have resulted in an overpressure exceedance. HVO have not had a blast overpressure exceedance for at least five years. A meteorological model for predicting inversions has been implemented and incorporated into blasting procedures to reduce the risk of a recurrence. As a result of this incident a warning letter was received from the DECCW due to a breach of the EPL. Incident 1000053288 On Monday 21 September 2009 at 3:00pm, during a non-routine inspection, an old exploration borehole was found to be discharging saline water into a clean water diversion channel. The water collected in a downstream dam within the HVO EPL Boundary. The volume of water discharging from the borehole was estimated to be in the vicinity of a 1-3L/s. Water samples were taken from the bore, which indicated that the discharging water had a high salt content (EC of 6.92mS) with a pH of 6.57. Water samples were also taken from the downstream dams to determine the extent of the discharge. Water samples were also collected from the nearest mine water storage to determine the origin of the discharging water. The investigation determined that the discharging water was originating from a mine water storage void on site. The extent of the discharged water was found to have extended no further than a farm dam within the mine lease area. The farm dam is currently being managed to ensure no mine water leaves site. Actual environmental impact was considered negligible given that all water is currently contained on-site. AEMR 2009 150
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HVO 2009 Annual Environmental Management Report - Final

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