Giant Mine Oversight Board: Research Program

237,000 tons of arsenic trioxide dust are currently stored in fourteen underground chambers at the Giant Mine site. After evaluating a wide range of technical solutions to manage potential environmental impacts associated with the dust, the Project Team determined that its preferred method was to permanently freeze the dust and the rock around each underground chamber.

The Environmental Assessment of the remediation project concluded that the this “frozen block” method was the most appropriate technical solution currently available. However, it was also determined that freezing should not be viewed as the permanent solution and that emerging technologies should continue to be investigated. As a result, the Giant Mine Oversight Board, through Article 7 of the Giant Mine Remediation Environmental Agreement, has been tasked with supporting research into technical approaches that could serve as a permanent solution.

A State of Knowledge report regarding current remediation technologies for arsenic trioxide will be competed in early 2017.  A formal research strategy will then be developed to begin the active research.

Article 7: Active Research Toward a Permanent Solution for Arsenic

7.1 Research Program

In order to facilitate active research toward a permanent solution for dealing with arsenic at the Giant Mine site, the Oversight Body shall, on a periodic basis, ensure that:

  1. reports on relevant emerging technologies are produced;
  2. research priorities are identified;
  3. research funding is administered;
  4. results of research are made public; and
  5. the results of each cycle are applied to the next cycle of the steps described in sections 7.1(a) through 7.1(d).

7.2 Engagement

In conducting all of its activities described in section 7.1 (“Research Program”), the Oversight Body shall:

  1. encourage public awareness of its work; and
  2. create opportunities for interested persons, including the Parties, to participate as the Oversight Body considers meaningful and appropriate.

7.3 Existing Programs

In conducting all of its activities described in sections 7.1 (“Research Program”), the Oversight Body shall make best use of existing research institutions and programs.The research program will focus on the identifying effective arsenic trioxide management alternatives that are capable of protecting human health and the environment forever, that does not require human intervention.

Arsenic Trioxide (As2O3)

Chemical Compound


Formula: As2O3
Molar mass: 197.841 g/mol
CAS ID: 1327-53-3 [1]
Density: 3.74 g/cm³
Boiling point: 465 °C
Melting point: 312.2 °C

The word arsenic is derived from the Persian zarnikh and Syriac zarniqa, later incorporated into ancient Greek as arsenikon, which meant “masculine” or “potent” and referred primarily to orpiment, or yellow arsenic. The word became arsenicum in Latin and arsenic in old French, from which the current English term is derived. [2]

Arsenic is a naturally occurring element found in soil, water, plants and animals.  The properties of arsenic have been known since antiquity. Arsenic is naturally occurring in the food chain and is present in a wide array of foods, including flour, corn, wheat, fruit, poultry, sea food, rice and vegetables, as well as beer and wine, fruit juices and water. In modern times, arsenic has been used in a variety of applications including as wood preservatives, pesticides, in specific medical treatments and the semiconductor industry.

Arsenic trioxide is an arsenolite, an oxidation product of arsenic sulphides (white arsenic, As2O3). It is an inorganic compound created as a by-product of the process of extracting gold from arsenopyrite ores.  At the Giant Mine, roasting the ore at high temperatures released an arsenic-rich gas requiring the use of electrostatic precipitators, and bag houses to capture arsenic compounds. Up to 99.7% of the dust and fumes produced during roasting were captured, once the equipment was installed and operational. Prior to this, the arsenic gases were released directly into the atmosphere.

Over the lifetime of the Giant Mine, 237,000 tonnes of arsenic trioxide dust were collected and are now stored in chambers underground at the mine site. This collected dust is water soluble and contains approximately 60% arsenic trioxide and other minerals such as iron, antimony and gold.


  1. A CAS Registry Number, also referred to as CASRN or CAS ID, is a unique numerical identifier assigned by Chemical Abstracts Service (CAS) to every chemical substance described in the open scientific literature (currently including those described from at least 1957 through the present), including organic and inorganic compounds, minerals, isotopes, alloys and non-structurable materials (UVCBs, of unknown, variable composition, or biological origin)
  2. Vahidnia A, van der Voet GB, de Wolff FA. Arsenic neurotoxicity – a review. Human Experiment Toxicol 2007: 26: 823-832

Surface and Offsite Contamination

In addition to arsenic trioxide stored underground, the environment surrounding the Giant Mine site has been contaminated from arsenic trioxide dispersed during mine operations. While the Giant Mine Oversight Board has concluded that its research mandate will focus on the arsenic trioxide currently stored underground, it fully recognizes the importance of research and remediation related to surface contamination, including the aquatic environment. GMOB will continue to strongly encourage research into surface contamination issues by the appropriate agencies.