A mistake in measuring the population at Riversdale Beach, on the Wairarapa coast, has seen the cost of providing sewerage to the beach resort leap by over $1 million.
After earlier investigations, the cost of a reticulated sewage scheme to service 290 properties was put at $3.24 million.
But a report tothe Masterton District Council says it will cost $4.45 million and blames higher-than-projected numbers of people at the beach over the summer, which means a higher-capacity system is needed.
Riversdale relies on septic tanks but groundwater contamination has meant increased momentum for a sewage scheme, with residents and the Masterton District Council keen for a solution.
The leap means each property's share of the cost will probably be between $4600 and $12,280.
