Waimakariri District Council has hired another company to re-do a survey of a new subdivision after it was discovered flood levels had been incorrectly measured.
The 300 houses at Silverstream Estates at Kaiapoi were fast tracked using special earthquake legislation.
The mistake calculating flood levels was discovered by chance by a builder's surveyor.
A council spokesperson said it was picking up the tab for the re-assessment work, but reserved the right to send the bill on to the company that made the mistake, Davis Ogilvie.
Only once the levels have been rechecked will it be known exactly how many of the 300 homes are affected.