Major environmental incidents

There has been sand mining on Stradbroke Island for about sixty years. Over that time there have been numerous major environmental incidents which have dramatically affected the island’s dunes, lakes, swamps and the large aquifer. Below is a description of some of these incidents which have affected Straddie’s waterbodies.

The current mining company, Sibelco, may argue that they have systems in place to ensure incidents like these would not happen now.  This is wrong!  Recently, in September 2011, Sibelco pleaded guilty to allowing a dam wall at its mine in the Upper Hunter (NSW) to collapse, releasing up to five million litres of sediment laden water which seriously polluted Middle Brook.

Sibelco cannot be trust to protect the environment on Stradbroke Island.

60 000 – 100 000 diesel spill near Amity Swamp

1991 CRL was responsible for a 60,000-100,000 litre diesel “, spill near Amity Swamp. CRL did not disclose the spill to the Department of Mines until 1994 (3 years later).

Lake Kounpee drained by sand mining

Description of impacts

CRL Bayside Mine ruptured aquitards (1987) which supported the fragile perched lake system of Lake Kounpee. This resulting in the draining of the lake. Bentonite and mine tailings were added in unsuccessful attempts to slow water loss at the lake bottom, even though the evidence indicated that the aquitards responsible for perching had been cut by mining to the west of the lake.

CRL attempts to raise the water level by pumping water from other areas (18-Mile Swamp) were unsuccessful because a maximum level was lowered by new conditions in the ruptured aquitards. Some natural recharge has occurred from rainfall.
Waters of different quality added to compensate for reduced natural inflows within the small catchment of perched waters.
Exotic flora and fauna species in waters pumped form 18-Mile Swamp and Kounpee Trench were also added to the lake ecosystem.

Remedial Actions taken and outcomes

CRL mounted two campaigns (1988, 1997/98) to build subsurface grout walls (one close to the lake margin and the second subsurface “curtain” about 100 m to the west) to reduce subsurface water outflow and raise surface water levels to the pre-mining range. CRL’s consultants differ in forecasts of the 1998 microfine grout stability. Trenches were constructed close to the 1998 injection points as part of a proposed program to test integrity of the grout “curtain”, and for artificial recharge areas so that a long filtration pathway may ‘modify the composition’ of make-up water to be pumped from Kounpee Trench. CRL (October 1998) after applying to the DME to artificially recharge did not do so. Rainfall led to a small natural recovery of the water level. CRL reapplied in 2001 and DNR&M approved artificial recharge in 2002 to accelerate the natural rise in water level. Problems with rates of infiltration so recharge trenches enlarged (June 2002). Water levels have not yet stabilised to test the integrity of the grout curtain.
DME officers (1997/8) approved a program to strip accessible bentonite and tailings that had been added to the lake but now can change water quality. Long-term outcomes of water quality have yet to be determined. Baseline data on original water quality is limited.

DME and DNR officers approved a program to eradicate pest fish with poison (Rotenone). Long-term outcomes of flora and fauna species and populations have yet to be determined.
Lake Kounpee North Long-term monitoring shows a marked decline in water level over time. CRL (2001) admit these changes probably caused by ruptured aquitards in the Lake Kounpee catchment area and/or increased outflow resulting from reduction in water levels at Lake Kounpee and/or natural changes in rainfall. CRL’s consultant concluded that Bayside mining ruptured aquitards associated with the perching of Lake Kounpee had not affected Lake Kounpee North. However, CRL documents appear to show official acceptance that water levels in Lake Kounpee North were affected by the damage to Lake Kounpee.

Aboriginal shell middens destroyed

Extensive sandmining of the East Coast dunes destroyed numerous shellmiddens of archeological and aboriginal cultural significance.

Lake Kounpee North

Description of Impacts

Long-term monitoring shows a marked decline in water level over time. CRL (2001) admit these changes probably caused by ruptured aquitards in the Lake Kounpee catchment area and/or increased outflow resulting from reduction in water levels at Lake Kounpee and/or natural changes in rainfall.

Remedial Actions Taken and Outcomes

CRL’s consultant concluded that Bayside mining ruptured aquitards associated with the perching of Lake Kounpee had not affected Lake Kounpee North. However, CRL documents appear to show official acceptance that water levels in Lake Kounpee North were affected by the damage to Lake Kounpee.

Kounpee Swamp

Description of Impacts

Because Lake Kounpee and Kounpee Swamp share an overflow at R.L. 43.5 m, the impacts at Lake Kounpee may indirectly affect this area in the longer term.

Remedial Actions Taken and Outcomes

No technical investigations to test for possible effects of outflows from Lake Kounpee on Kounpee Swamp have been reported.

Blaksley Lagoon

Description of Impacts

Since the CRL Bayside Mine operated near the lagoon in 1981/82 long-term monitoring and independent observations confirm a permanent reduction in water levels (pre-mining record high of RL 33.5 m). This degraded condition is probably caused by damage to subsurface aquitards that create perching conditions.

The lagoon was used as a holding pond for Bayside make-up water from 18-Mile Swamp and this activity would have added water of different quality and probably introduced exotic species of flora and fauna. However, because the lagoon reduces to a dry bottom the ecological impacts are not known.

Remedial Actions Taken and Outcomes

CRL’s AERs refer to probable damage by mining, but a full retrospective analysis to determine the likely subsurface conditions (as with Lake Kounpee) has yet to be carried out.

Sampling for water quality is infrequent, in part because the water level is so low.

No environmental studies of the flora and fauna have been reported.

(CRL intend to use the experience of artificially recharging Lake Kounpee catchment as the basis for a similar remediation program at Blakesley Lagoon. However, no detailed study to determine the nature and locations of the postulated ruptured aquitards has been undertaken

South Lagoon

Description of Impacts

Lagoon water levels increased due to discharges (seepage) from Gordon dredge pond at rates faster than the WNC (1997B) model predicted. No CRL data presented but the highest (June 1997) level at RL 13.26 m is probably 3 m higher than natural.

Water quality appears to have changed slightly (acidity reduced by almost 1 pH unit; this is equivalent to a 10-fold decrease in acidity)

Peripheral vegetation lost by drowning. Vegetation lost by clearing for installation of dewatering equipment (e.g. bores and spearlines, powerlines).

Remedial Actions Taken and Outcomes

CRL installed bores and spears to pump water from the lagoon back to Gordon dredge pond. CRL has set a target for early to mid 1999 to reduce the water level to R.L. 11.2 m but this was not achieved until mid 2000. Inundated areas still remain in some locations.

Native Companion Lagoon

Description of Impacts

For at least four years Native Companion Lagoon was flooded by dredge pond seepage from CRL’s Gordon mine. (Between 1988 and 1993)

Water quality data indicate that drainage from the mine continued into late 1994.

The surrounding vegetation and animals suffered severe damage, including the drowning of approximately 6 ha of peripheral vegetation and the sedge population in the lagoon was reduced.

Remedial Actions Taken and Outcomes

CRL reported that water levels have returned to pre-mining conditions.

No assessment of impacts on water quality can be made because of the lack of pre-mining water quality data.

CRL commenced a revegetation program in 1992. No data on progress has been presented and was not reviewed in the AERs for 1997/98 and 1999/2000

Duck Lagoon

Description of Impacts

CRL cyclone-return waterline burst; topsoil and tailings and process water washed into lagoon.

Approximately 300 cu m of tailings, topsoil and processed water flowed into lagoon during heavy rains.

Water quality may have been affected by this incident; no monitoring data reported.

Remedial Actions Taken and Outcomes

CRL removed topsoil and tailings from lagoon (method not stated0. Silt fencing erected and earthworks carried out near drainage area as a measure of future recurrence.

Ground water modelling undertaken in 1997 predicts levels likely to rise to near the levels of the perching units. Groundwater extraction was commissioned late 1997.

Canalpin Creek/Swamp

Description of Impacts

Tailings sand from CRL’s BaysIde mine was illegally dumped on a recreational reserve.  CRL’s Ibis mine water supply pipe burst, causing a huge sand slip, smothering four hectares of swamp, mangroves and sea grass beds in Moreton Bay. This sand slip is very obvious from satellite images.

Pre-mine hydrological studies and groundwater modelling indicated potential for this area to be impacted upon. Slight rises in water levels in creek and fringing swamp occurred due to discharges (seepages) from dredge pond (late 1997 and 1998).

No formal action was taken by the Department of Mines.

Remedial Actions Taken and Outcomes

CRL erected silt-control fencing in damaged area to reduce additional movement of sediment into wetland. Displaced sand and soil removed by hand shoveling. Vegetation left for natural regeneration. Dewatering equipment (i.e. spearlines) erected to reduce increased outflow from toe of Ibis dune.

Black Snake Lagoon

Description of Impacts

Pre-mine hydrological studies predicted the potential for adverse impacts generated by the CRL’s Ibis Mine. Increased water levels due to discharges (seepages) from Ibis dredge pond during 1997/98 and of inflow of water from tailings placed in 1998. Water of different quality introduced to the subsurface

Remedial Actions Taken and Outcomes

During July 1997 CRL installed an additional bore at the southwest bank of lagoon and constructed a spear line in December 1997. Water levels were temporarily controlled and ceased in March 1998. Slow rises in the ground water level in response to tailings placement has led to a rise in water level at lagoon. Water levels maintained within normal range even though other lake levels are falling due to reduced rainfall.

Long-term effects on water levels and water quality, if any, have yet to be determined.

Ibis Lagoon(s)

Description of Impacts

CRL artificially increased water levels due to discharges (seepages) along the top of the perching layer from the Ibis Mine dredge pond during 1996/97.

Water from Ibis mine dredge pond is of different water quality to that in Ibis Lagoons. Additional discharges of groundwater coming to the surface from mid 1999. CRL served with “show cause” notice.

Remedial Actions Taken and Outcomes

CRL removed vegetation and installed dewatering equipment to mitigate mining-induced rises in water levels. Mining program also modified to prevent additional discharges. Consultants engaged to study aspects of these events as part of official response to “show cause”. DNR&M accept CRL’s water management plan.

Wallen Wallen Creek/Swamp

Description of Impacts

Kounpee Trench (and pump station located in trench) cut into western fringing swamp at Wallen Wallen for water extraction at the former Bayside mine and the existing Ibis mine. Small quantity of water also used to recharge Lake Kounpee.

Remedial Actions Taken and Outcomes

No known or planned rehabilitation or remediation of this excavated trench.

Aranarawai Creek /Swamp**/Amity Swamp

Description of Impacts

Trench cut into swamp (late 1970s) surrounding creek used to pump water to Amity dredge pond (1977 to 1992). Water quality declined after 1992.

Remedial Actions Taken and Outcomes

No known or planned rehabilitation or remediation of this excavated trench has been advised.

Welsby Lagoon(s)

Description of Impacts

Mining changed original visual landscape to the north of the lagoons.

Wallum Creek

Description of Impacts

The mining company constructed an illegal dam wall across Wallum Creek to block salt water influxes to the creek so it could be used as a source of water for a dredge pond. The dam prevented normal tidal exchange and, after seeping down through the sand, the saline water killed most of the terrestrial vegetation along the western foot of the dunes, upstream of the dam site.

To establish the AMC Amity Mine dredge pond in 1977, several million cubic metres of sand overburden were excavated and most was pumped to reclaim areas for RSC’s caravan park south of Amity Township. As surface fresh water was in low-supply AMC pumped sea water from the tidal portion of Wallum Creek to the dredge pond. Eventually the saline water seeped from the pond and, coming to the surface along a 1-km-long zone, killed the terrestrial vegetation. Following DME instructions to cease pumping sea water, AMC constructed (off-lease and without approval) a bund wall (dam) across Wallum Creek, and pumped fresh water from the dammed-off area. Intertidal vegetation and fauna were killed because the dam prevented normal tidal exchange. After official instruction, AMC finally removed the bund wall in 1979.

Remedial Actions Taken and Outcomes

No specific rehabilitation efforts were made on the affected areas as they were on Crown land and off lease. No investigation of local contamination of ground water by salt water additions were made. Quinn and Beumer (1984) reported on the degree of mangrove recolonisation as at September 1983.

The regulator did not apply any penalties on either AMC or the lease holder (CRL).

Yarraman Lagoon

Description of Impacts

Competing for water for their dredge ponds, CRL& AMC pumped excessive amounts of water from Yarraman Lagoon. This resulted· in the exposure, drying out and fracturing of previously submerged peat beds and the death of all water  dependent vegetation at the back’of 18 Mile Swamp.

By the late 1960s the catchment of Yarraman Lagoon, and Yarraman Creek feeding it, were affected by sand infill from access roads. Into the 1970s (CRL and AMC) over-extracted water from the Lagoon. Submerged organic-rich sediments (peat) were exposed and on drying out shrank, fractured and crumbled. A spill of tailings buried the southern end on the shore. Yarraman Creek cut a new course. Up to the start of remining at Yarraman (2000) the lagoon held a smaller amount of water and exhibited extreme fluctuations in levels.

Remedial Actions Taken and Outcomes

The surrounds of Yarraman Lagoon received revegetation treatment (AMC) as required at the time of mining. No rehabilitation was attempted in the main Lagoon area (Crown land). After remining commenced at Yarraman (2000) all water bodies are monitored regularly. CRL is progressively reconstructing some new waterbodies and retaining others. The outcomes can be reassessed after mining concludes post 2010.

18-Mile Swamp

Description of Impacts

Trenches cut into Freshwater Creek and 18-Mile Swamp include Herring Lagoon (for the RSC water extraction pump station and CRL make-up water), Palm Lagoon (for Cr.’s Gordon Mine make-up water pump station) and Tazi Trench (site of former TAZI mining company water extraction site)

Remedial Actions Taken and Outcomes

All three artificial lagoons remain today. Herring and Palm Lagoon are both currently being used by RSC and CRL.

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