 The availability of sea sand within the Auckland region means the road costs of transporting sand from further parts of the country are avoided.Concerns about possible negative consequences of this sand mining have also been raised.In 2008, Crest Energy, a power company, received resource consent to install about 200 underwater tidal turbines in the Kaipara Harbour, which would use the substantial tidal flows moving in and out every day near the harbour mouth to produce electricity for approximately 250,000 homes.