The cache is across the river from the intake to the Amuri Irrigation Scheme.
Cross the bridge and park up on the same side as the cache in a wee layby (rather popular spot on the day I placed the cache). The scheme was built in 1980 by the government to supply water to the areas between Balmoral to the south and Waiau in the north east and you will cross it a few times on a trip between here and the Hurunui river. There used to be an old cache not far from here but it got claimed by the river (which is why it isn't closer to the intake!).
This cache is a 200ml Sistema which should hopefully get less wet than the predecessor. No need to cross the fence!