Supervising Scientist Division

Supervising Scientist Annual Report 2002 - 2003: Nabarlek

Supervising Scientist, Darwin, 2003
ISBN 0 642 24383 2
ISSN 0 158-4030

2 - Environmental assessments of uranium mines (continued)

2.4 Nabarlek

2.4.1 Developments and on-site environmental management

Pioneer International Ltd and the Northern Land Council (on behalf of the Traditional Owners) continued discussions related to the rehabilitation expectations for Nabarlek. This includes arrangements to complete site clean-up, particularly the former camp area and laboratories.

Weed and fire control on-site have been actively pursued to protect the development of a mid-storey canopy and feral animal exclusion from the site has been significantly improved. Further planting of root stock in the vicinity of the former ponds area is planned following the successful programme involving Traditional Owners reported in the 2001-02 Supervising Scientist Annual report. It is the Supervising Scientist's view, however, that these positive initiatives by Pioneer International need to be followed by a more strategic approach to ensure that rehabilitation outcomes acceptable to all stakeholders are achieved. At the MTC meeting held in April 2003, the MTC agreed to an oss request that the next meeting, scheduled for the new financial year, be devoted to commencing the development of a strategy for the final rehabilitation of Nabarlek.

A Mining Management Plan (MMP), required under the NT Mining Management Act, has been approved and is in operation at Nabarlek. This plan describes how the site will be managed for the coming year. Compliance with the MMP will be audited by oss, NLC and DBIRD in July 2003.

DBIRD has completed a review of the movement of contaminants in groundwater at Nabarlek. Overall, the quality of surface and groundwaters in the region continues to improve. The most important potential contaminant sources are buried tailings in the former pit and residual effects from the land application of pond water over a decade ago. It is likely that future monitoring needs at the rehabilitated minesite will be rationalised to focus on these contaminant sources by seeking further verification that the tailings containment design continues to perform to expectations and that the environment remains protected.

Minesite Technical Committee

The Nabarlek Minesite Technical Committee met once during the year. Table 2.12 provides information on the meeting and the major points of discussion.

Table 2.12: Nabarlek Minesite Technical Committee Meetings
Date Significant agenda items
23 April 2003 Application for Authorisation and Mining Management Plan

There were no reportable incidents at Nabarlek during the year.

2.4.2 Off-site environmental protection

Routine monitoring of the site continues to be undertaken by staff of DBIRD. The results published to date indicate that there are no detectable impacts arising from the site in the surface waters and that the ground water impacts remain insignificant. In the former forest irrigation area the groundwater quality continues to approach the pre-mining condition.

2.4.3 Indicators of ecosystem rehabilitation success

Following the recommendations of a workshop on the rehabilitation of Nabarlek mine in April 2000, attended by the major stakeholders involved in the process, the Supervising Scientist awarded a research grant over two years in November 2000 to the Australian Centre for Mining Environmental Research (ACMER). The grant was in support of Stage 2 (Verification of indicators and transfer of monitoring technology) of the project 'Indicators of ecosystem rehabilitation success'. The project sought to verify that Ecosystem Function Analysis (EFA), a method of assessing the trajectory of an ecosystem, can be used on rehabilitated minesites to assist in interpreting whether a self-sustaining system is evolving. Nabarlek has been used as one of the nine test minesites in this appraisal with fieldwork completed in the 2001 dry season. The Draft Final Report was received in May 2002.

The correlation of four EFA indices with relevant contemporary published measures was investigated at each of the nine minesites. Of the total of 36 comparisons, 22 were fully verified, eight were partially verified, five could not be verified for technical reasons (for example, inappropriate equipment for the field conditions), and one failed to be verified. Full verification required the regression relationship between the measured variable and the EFA index to have an r2 value greater than 0.5 and P < 0.05 with data from the minesite and the analogue site plotted together. Partial verification required the same statistical significance between the measured variable and the EFA index but allowed for different regression equations between the analogue site and the minesite. In this case, cross calibration would be required to meaningfully compare the value of an EFA index at an analogue site with the value of the EFA index at the minesite. For example, an infiltration index of 0.3 might correlate with an infiltration rate of 80 mm/h on the rehabilitated minesite and 180 mm/h on the analogue site.

At Nabarlek, the Stability index and the Nutrient Pool Size Index were fully verified, the Soil Respiration index was partially verified and the Infiltration Index failed to be verified. Infiltration rates were measured at Nabarlek during the dry season when the soils were dry to a depth of 50 cm and 'cracked'. Hence extremely high infiltration rates were measured that had no correlation with the Infiltration Index. These high infiltration rates, due to the 'cracks' in the soil, would not reflect infiltration rates during the wet season when the soil is wet and devoid of cracks due to swelling of clays.

The ACMER project confirmed EFA to be a valid and cost effective method for tracking the development of a rehabilitated landscape over time and for comparing those sites with analogue landscapes. However it is not intended to be the only method by which rehabilitation success at any site should be assessed. The contemporary measures used to assess the status of an ecosystem should still be used in any assessment of rehabilitation success. EFA provides additional information that can be very informative when used in a time series at significantly less cost than the contemporary measures and may reduce the frequency at which those contemporary measures are required.

oss will discuss the use of EFA at Nabarlek with the Nabarlek MTC in 2003-04 in the context of the development of a final rehabilitation strategy.

2.5 Other activities in the Alligator Rivers Region

2.5.1 Historical tailings adjacent to the Gunlom Road

During 2002-03, oss provided technical advice to Parks Australia North (PAN) to assist it in managing the area (the tailings area) adjacent to the Gunlom Road where uranium mill tailings from historical mining and milling activities conducted in the 1950s and 1960s had been deposited. oss implemented a programme of inspections focusing on issues such as radiological protection, fire, weed and erosion control in accordance with the agreed protocol. These activities focused on the tailings area, that had been stabilised with a rock cover to minimise erosion in 2000, and the small compound located nearby within which contaminated soil from the side of the Gunlom Road had been placed also in 2000. Both of these sites were well managed by PAN.

The development of a long-term management and containment strategy for the contaminated soil and tailings from these sites progressed during the year as part of the broader processes concerned with the development of a rehabilitation plan for the former uranium mines in the South Alligator Valley.

2.5.2 Rehabilitation of the South Alligator Valley uranium mines

Supervising Scientist Division staff continued to be involved in the development of the rehabilitation plan for the former uranium minesites in the South Alligator valley, as technical advisers to PAN. The initial part of the Rehabilitation Plan (Part A) reached the final draft stage during the year when the cultural setting was completed by the NLC and the draft was accepted by the Traditional Owners. This final draft is to be sent to the regulating agency (ARPANSA) for appraisal in the second half of 2003.

Part A deals with the rehabilitation of those sites where radiological issues are not a significant concern and rehabilitation is likely to require only relatively minor revegetation and earthworks.

Part B of the plan, which deals with sites where there are radiological issues, continues to be developed in consultation with the Traditional Owners. An essential component of Part B is the identification and approval of a suitable containment site for materials with radioactive contamination, such as that from the Tailings Area adjacent to the Gunlom Road. The Technical Advisory Group drafted a set of criteria for the location of a suitable containment site. These were used as an input to a desk study which resulted in the production of a map of the area identifying potentially suitable and unsuitable areas. Field checks were made in June 2003 to establish the validity of the method. Further field trips and discussions with Traditional Owners, some of which are planned for the second half of 2003, will lead to the selection of sites for more detailed investigation.

Work programmes for the specific sites at Sleisbeck and Guratba were also drafted during the year in preparation for field work once funds are available and all the necessary clearances have been obtained. It is hoped that PAN may be able to commence field work in 2004 and is intended that oss will be involved in providing elements of the works supervision.

The annual check of landfills and containments from the previous hazard reduction works was completed in October 2002. The annual programme involves examination of each site for signs of developing erosion problems and a basic radiological safety inspection. In 2002 the triennial radiation safety survey was also undertaken at each site. The outcome of the survey was reported to PAN in an Internal Report. All the survey results were satisfactory.

2.5.3 Exploration

Three uranium exploration campaigns were conducted in the Alligator Rivers Region during the 2002 dry season. All were continuations of programmes from previous years with the same operators in the same general areas. oss visited all the operational areas during the exploration season to inspect the environmental management procedures in place, including the management of camp facilities, management and rehabilitation of drill sites, and to check on progress of sites rehabilitated in previous years. The inspections were undertaken jointly with an inspector from DBIRD and a representative of the NLC. The operational areas visited were the King River vicinity (exploration by Cameco Australia Ltd), and the Myra Falls/Tin Camp Creek vicinity (exploration by Afmex and Cameco).

In all three campaigns, performance was found to be satisfactory with standards still improving as operators continued to pay attention to detail in dealing with environmental issues. The major issues discussed at each site were management of fuels and oils, disposal of rubbish, drill pad rehabilitation and standards applied in building exploration roads. Overall environmental management of exploration was of a high standard.

In December 2002 Afmex announced that it was withdrawing from exploration in the Alligator Rivers Region and would be closing its Darwin office. The camp at Myra Falls is now being operated by Cameco who have involvement in some of the former joint operations with Afmex as well as campaigns of their own in the area. Cameco will be the sole exploration operator in the Alligator Rivers Region in 2003.

At the end of the 2002-2003 wet season, preparations began for the 2003 dry season campaigns. oss has been in consultation with Cameco, the NLC and DBIRD to prepare an appropriate inspection regime for 2003. It will be implemented between July and September 2003.