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Home arrow Archives   The American Surveyor     

An Integrated Solution for Mining Print E-mail
Written by Leonie Preston   
Friday, 11 March 2011

A 1.767Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

The Twangiza-Namoya gold belt in the eastern Democratic Republic of Congo (DRC) is potentially one of the most exciting undeveloped gold deposits in the world today. Exploration and mining activities across what are today Banro's four major projects began in the 1920s. The Company's most advanced and largest project, Twangiza, was discovered in the 1950s and currently possesses mineral reserves of 4.54 million ounces. In 1996, Canadian-based gold exploration company Banro Corporation acquired control of the Twangiza property and started a US$9 million exploration program the following year. The Company left the DRC in 1998 and resumed exploration in October 2005. It has since invested over US$80 million in exploration on the Twangiza project alone.

Today, Banro's four projects--Twangiza, Kamituga, Lugushwa and Namoya--contain 6.72 million ounces of identified and measured resources, as well as inferred resources of 4.46 million ounces and have considerable potential to add future resources. Twangiza, however, will be the first to enter production. Banro is aiming to process 1.3 million tonnes (1.43300 tons US) of ore per year and is scheduled to begin operations of the Twangiza gold mine in late 2011.

With Banro's focus to date being exclusively on gold exploration, Banro's Chief Surveyor Mike Trenor says Banro's mission for the Twangiza project is to continue expansion of its resources. "Presently only about ten percent of the total Twangiza license has been explored," Trenor said. "Banro hopes that continued regional exploration will add oxide and transitional resources."

As part of Phase 1 of the project, the reconstruction of roads, bridges and infrastructure is still underway. Projected to be completed by end of 2010, Banro is using scalable Trimble RTK GPS surveying technology that has proved to not only be important, but essential--particularly as there are no remaining national survey reference network points around the project area. Prior to Congo achieving its independence and becoming a republic in 1960, there was a network which was constructed and maintained by the colonial administration.

At the outset of Congo's independence, all the reference points were destroyed by local inhabitants, who believed that gold and other treasures had been hidden beneath them. Thus, Banro had to establish a geodetic control network from scratch.

The Twangiza Mine will be an open-pit operation, since the oxide resource is situated along the crest of a major anticline--perfect conditions for RTK GPS. The RTK base station has to date been used in a mobile role and was set up on a Banro control point near the area of work with the CMR+ corrections transmitted via a 35W Pacific Crest repeater radio. For the construction and mining phase, the new base station will be permanently mounted on the roof of the IT building, and will be transmitting the CMR+ corrections 24/7.

Rigorous Conditions
The Twangiza Project is situated on the edge of the Rift Valley, at the northern end of the Itombwe Mountains. With altitudes of between 4,900 and 9,800 feet above sea level, and deeply incised valleys with few or no roads, access is a problem. Initially there was no communication, apart from HF radio and satellite phones. Access was limited to helicopter. Fortunately the Trimble R8 GNSS Rover, with no cables or backpack, was light enough (at just over 2 pounds) to not have been a major burden during the early surveys.

Today there is road access to the mine site and cell phone networks have penetrated to all of Banro's project areas. The rugged topography, difficult access and the complete lack of national survey reference network points have all contributed to Banro's decision to utilize the Trimble RTK GPS surveying equipment. The project is broken up into three phases, with the first phase (exploration) to a large extent having been completed. The project is currently entering phase two which will mainly entail construction and phase three which will commence in late 2011 and will focus on mining.

"As this is a relatively recent project (the current exploration and development program commenced in late 2005) the Trimble RTK GPS equipment is used for almost all of our day-to-day survey work on the project," says Trenor. "The only time we don't use it is when reflectorless total stations provide safer measurement to exposed and dangerous mined pit faces." The Trimble TSC2 Controller is used with Survey Pro software that works seamlessly with RTK and conventional total stations. For the survey of difficult and dangerous faces in the artisanal pit, control is brought in by RTK, and then completed with the total station utilizing the same job file.

Increased Productivity
The first step for Banro had been to establish a control network. This was done by fixing a primary point at the project using AUSPOS and then fixing a control network using static GPS observations and Trimble Geomatics Office Software. Thereafter topographic, borehole setting out, collar surveys as well as road and construction setting out surveys were implemented, mostly with the RTK system. The Trimble GPS receivers also provided essential ground control data for the LiDAR surveys that were flown in 2007 and 2008. As Banro moves into mining, more rovers will complement the survey equipment for mine layout and repeated volumetric surveys. Accuracy requirements are dependent on the type of survey being carried out, but typically for RTK it is of the order of 25mm.

The productivity achieved from using this equipment is a major benefit with personnel who have rudimentary surveying skills but can be trained to become productive in a short time. With Trimble's RTK GPS, measurements and results are available immediately, without the need for an extensive control network or time-consuming office calculations. Banro currently uses Trimble Geomatics Office and ModelMaker for day-to-day work, but the new rovers will be using Trimble SCS900 Site Control Field Software and Trimble Business Center Office Software.

One of the important tasks undertaken by the Banro surveyors is the positioning of completed exploration drilling. All the exploration diamond drill collars for the project are surveyed and fixed using the Trimble surveying technology, which allows for electronic data to be recorded providing accurate measurements and descriptions. It is the repeat measurements of undisturbed collars that prove the accuracy of the results. If any drill collar is resurveyed and it differs by more than 5 cm from the previous value, it is investigated and resurveyed.

Trenor comments that with years of proven performance and flexible field control options, Trimble's RTK GPS equipment considerably improves productivity, efficiency and accuracy. With RTK GPS the number of rovers working in the field is unlimited, and instead of having a two-person total station survey crew, you can have two GPS survey teams operating in real time. This potentially boosts the mining profits by implementing quicker audit measurements. The mine is not tied to AFREF, but once the permanent mine beacons and base station are fixed, this will be considered.

As with any mechanical equipment, the user's productivity and overall profitability needs to be maximized. Banro is now in the construction phase of the project and will move in the next two years into full mine production surveying.

Impact on DRC Communities
The economic and social benefits for the communities of the eastern DRC region will be considerable. People in this region have suffered tremendously, particularly during the years 1996-2002, in what some commentators have called as "Africa's World War." The formal, regulated mine that is being established by Banro will have a definite impact on improving living standards. In many respects, the establishment of a mine is the only path to the improvement of the lot of local communities.

Through the Banro Foundation, a registered DRC charity, the Company has already built two new schools, a potable water system serving 18,000 people and has rehabilitated over 30 miles of roads and bridges in the Twangiza area. Banro recently signed a memorandum of understanding with the community of Luhwindja and a separate agreement with the leaders of the Twangiza artisanal miners. Both agreements will provide for continued social and economic benefits to both communities and create partnerships among the parties to support the development of the project.

Leonie Preston is a journalist based in Cape Town, South Africa.

A 1.767Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

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