RE: Consultation period16 Jun 2023 14:04
Part two. NRW issued its consent yesterday, 21 September, and Alba’s geologists were therefore able to collect the sediment samples from the estuary yesterday. As a result, it is expected that Alba’s report will be submitted to NRW in the next week or so, with a supplemental appendix being submitted once the estuary samples have been assayed at the ALS Laboratories (which normally involves a turn-around time of a few weeks). Given the time this process has taken to date, NRW has indicated to Alba that it will carry out its HRA as quickly as possible in order to proceed swiftly to a determination of Alba’s application.
Although Alba understands NRW’s concern as regards the potential impact of the discharge of water from any former mine into a watercourse, Alba has taken great care, and taken the best available advice, to devise a robust dewatering scheme and to ensure that any water discharged into the watercourse post-treatment in the manner proposed will not have a detrimental effect on the environment. Indeed, Alba’s and NRW’s concerns are completely aligned in that regard. It should also be noted that:
(1) The flooded lower workings are estimated to hold 800m³ of water, or about 1/3 of the volume of an Olympic-size swimming pool. With the water to be pumped at a flow rate of up to 4.2m³/hr (100m³/day), it is estimated that the lower workings would be dewatered within just eight days.
(2) Discharge from the drainage adit is not currently treated and has never been treated since mine abandonment in 1998. By contrast, Alba’s dewatering scheme involves:
· Water pumped out of the lower workings being first passed through two Siltbuster HB10 settlement tanks, operating in parallel and each with a capacity of 10m3/hr, with no settling reagents to be used.
· The electrical conductivity (EC) of the water being manually monitored on a daily basis (in Phase 1) and on a monthly basis (in Phase 2).
· Collected settled solids being assayed to determine if any gold or deleterious elements are present.
(3) A substantial amount of data has been compiled by Alba to date to support its application, including the following:
· 12 rounds of water sampling have been undertaken over the course of the best part of a year. Samples were taken from five sampling points, upstream of the mine, downstream of the mine and from the current discharge itself.
· The flooded Llechfraith Shaft has also been sampled and profiled. The water column in the shaft was profiled by lowering a Van Essen CTD diver, that was set to record water depth, temperature, and electro-conductivity every second. In addition, a profile was made of water temperature, electrical conductivity (EC), pH, dissolved oxygen (DO), and redox potential (ORP – which measures whether the water is reducing or aerobic), using an in-situ Aqua Troll 600.
· A v-notched weir was installed 10m into the drainage adit. The CTD diver was then deployed at this site to record the water quali