Opponents of oil and gas drilling want a technique that breaks rocks open to boost petroleum flow, banned in order to protect underground water.
Using a process known as horizontal hydraulic fracturing, or fracking, a mix of water, sand and chemicals is repeatedly injected at extreme pressure to break open long cracks, as a drill bores sideways through oil-and-gas-bearing rocks.
The Climate Justice Taranaki group says both petroleum and the chemicals used in fracking fluid can contaminate aquifers.
But the Petroleum Exploration & Production Association says any chemicals are hugely diluted and injected deep below fresh water.
TAG Oil of Canada is using the system near Inglewood and Stratford.
Such long cracks may reach mountain-filtered acquifers, which lie as deep as 800 metres.