Understanding Water at Waihi
At the Oceanagold Waihi operation we are well known as being a gold and silver producer, but what is less well known is that we are also a significant water producer. Our underground mine acts in a similar way to a bore well; drawing in water and removing it. Other water types around site are also captured and treated before discharge to the Ohinemuri River.
We use water in our refining processes, taking occur in, where well and spring water is drawn from, and what water leaves 40m3 of water on average a day from the and joins through evaporation and rainfall as part of the water cycle. Mine Ohinemuri River. However, we also discharge operation dewatering however, is deep enough below ground that it is 9,500m3 of water to the Ohinemuri on average confined to the lower basement andesites. The nature of the andesite rock a day; over 230 times what we draw. layer is such that it has minimal interaction with the above volcanic deposit In 2021, we discharged 3,500,000m3 of water, all to layer in relation to water; meaning that conditions like rain or drought do specific standards for safe release. These standards form not affect the amount of water present in our underground operations, and part of our operating consent conditions issued by conversely, mine dewatering cannot dewater or affect the upper layer. Waikato Regional Council through the Resource Baseline studies of the water quality and aquatic biology of the Ohinemuri Management Act. On site we maintain Polishing Ponds River and its tributaries originally commenced in 1981, and this work where treated water sits as its final step on site, awaiting continues today. At present, we maintain nine biomonitoring sites around independent lab results to confirm the water meets these the Waihi area: both upstream and downstream of the discharge locations specifications before its release. of our operation. Sites include the Ratarua, Mataura, and Waitete streams, Like much of New Zealand’s geology, the Waihi area is made as well in the Ohinemuri itself. In addition, ten river sites are regularly up of separate groundwater systems that are independent from monitored for water quality. Data from our water monitoring is reported to each other; soils, upper volcanic deposits and lower basement Waikato Regional Council for independent review. deposits – in the case of Waihi the lower deposits are mostly in the Multiple years of data, in-house monitoring, and external verification and form of andesite rock and begin to form roughly 100 m to 200 m study of the local waterways has helped contribute towards the Ohinemuri below the surface. Upper volcanic deposits are what most of us picture River being one of the most comprehensively studied and understood river when we think about water systems; this is the layer that Waihi’s rivers ecosystems in New Zealand.
Due to the current COVID-19 climate, we are postponing our planned Correnso and Project Martha Community meeting originally scheduled for Thursday the 3rd of March at 5:30 pm. We will confirm a new date and time when possible through our regular channels. Apologies for the inconvenience and we look forward to catching up with the local community when it is safe to do so.