Abagold WEC BAR - Anchor Environmental

A.2. POTENTIAL IMPACTS TO MARINE BIOTA: BAROTRAUMA FROM BLASTING (Alternatives 1 and 2)Explosive charges in, adjacent to or beneath a water column producepressure waves or shockwaves which pass into the water medium.Shockwaves have harmful and often fatal impacts on organisms with gascavities, for example swim bladders in fish and sinus cavities and lungs inbirds and mammals.Nature of impactStatusNegativeExtentLocalDurationMedium termIntensityHighProbability ofProbableoccurrenceCumulative impact Highprior to mitigationSignificance prior to HIGHmitigationDegree to which impact Mediumcan be mitigated No blasting in the sea must be conducted during the periodbetween 30 June and 31 December as southern right whales arelikely to be in the vicinity of Walker Bay. Observations with binoculars must be sited on key vantage pointsimmediately before the intended blast. Blasting should onlycommence when cetaceans are not seen to be diving or resting onthe sea surface within two kilometres of the blast site. All blasting must be conducted using a rock breaking technologyknown as NoneX (www.nonex.co.za). This is not an explosivetechnology. It is propellant compound encased in a cartridge whichreacts very quickly to produce high volumes of harmless gas(nitrogen, carbon dioxide and steam). The cartridge is sealed insidea drilled hole and ignited. High pressure gas is released and entersinto the fractures caused by drilling and natural fractures or planesof weakness in the rock. The gas pressure causes the fractures toexpand and the rock to split apart. The cartridges do produce ahigh pressure over a short time frame and so will produce noise. Blasting activities must be limited to one detonation series per dayto avoid or reduce the mortality of predators and seabirds attractedto fish kills from previous blasts.Proposed mitigationProbability ofPossibleoccurrence withmitigationCumulative impact with LOWmitigationSignificance with LOWmitigation53