Reclamation Difficult Job At California Borax Mine
Environmental article by Harold Hough
Considering how anti-business and anti-mining California is, it is hard to believe that the world’s largest borate minerals mine is in California. It’s even harder to believe that it is considered one of California’s most environmentally friendly companies. However, thanks to an aggressive environmental mentality, cooperation with local colleges and environmental groups, and a excellent reclamation program it is showing skeptics that mining and the environment aren’t incompatible.
Borax (formerly US Borax) is a part of the Rio Tinto Group and operates California's largest open pit mine in Boron, California - one of the richest borate deposits on the planet. The company supplies nearly half the world's demand for refined borates.
Borax began doing business about 130 years ago and today mines at its open pit operation in Boron, CA. This mine, which currently supplies nearly half of the world’s borax was discovered in 1925 and went into production in 1927. Originally, it was an underground mine for mining tincal ore; the principle sodium borate mineral. In the late 1950s it became an open pit operation for mining both tincal and kernite, which is used for manufacturing borates and boric acid.
At the same time the mine became an open pit operation, processing facilities were built on site. This expansion allowed it to become one of the major suppliers of borates and boric acid. Most of the processing of the borates for agriculture, industrial, and specialty applications occurs at Boron and at a second refining and distribution operation in Wilmington, CA.
Open pit operations require a lot of land reclamation. The challenge is even greater in California’s Mojave Desert, which has a complex ecosystem of scorching summer heat, sub zero winters temperatures, and little rainfall. Another problem of this high desert is the poor combination of soil, sand, silt, and clay that that Borax has to reclaim.
The work began with a baseline study in 1991 that looked at undisturbed land and what sort of plants inhabited the area. The next step was to plant a number of gardens to discover optimum seed mixtures, planting techniques, and slopes. When the overburden is dumped outside the ultimate perimeter of the mine, it comes to rest at an angle of about 36 degrees. This was found to be much too steep and therefore vulnerable to erosion. Angles of up to 18 degrees, achieved by bulldozers, proved better for the vegetation.
Borax used a form of terracing to prevent erosion and “harvest” the meager supply of water. Rain accumulates or “puddles” in the furrows so that it lasts longer and brings maximum benefit to the plants. Their studies also revealed that, unlike normal gardening, a rough, rocky surface makes a better nursery in this environment than a smooth seedbed. That’s because rocky lumps offer very young plants both shade from the sun and protection from the desert winds. Scientists also discovered that overburden from 200 feet below the surface was better for seed growth.
However, that isn’t enough to guaranteed seed growth in the Mojave Desert. Borax environmentalists looked at different types of saltbush from different vendors. In the end, they discovered that the best seeds were ones gathered locally rather than from a seed supplier.
Although the plants need to survive dry conditions, Borax biologists discovered that the ideal climate for the young plants was two wetter than average winters in a row – something that only naturally happens 15% of the time. Consequently, the mine gives the seedlings a little help if nature isn’t cooperating.
Seedlings aren’t the only consumers of water at Borax. Water is necessary for refining the borates, in addition to dust control. However, the biggest problem isn’t getting it, but properly disposing of it after it has been used. Borax has been committed to recycling and reusing much of the water that it uses in the refining process. The rest of the effluent from the refining process - mostly water and dissolved borates - is discharged into lined ponds. After the water evaporates, the borates are sent back to the refinery.
The process is also allowing the mine to reclaim some borates lost in older evaporation ponds. Borax is using magnetic separation to extract residual borates from the clay in older ponds for refining before sending the wastes to on-site landfills.
Despite the political problems and environmental challenges, Borax has found a way to successfully reclaim some of the most difficult terrain in the world. That’s one reason it is still operating in California.