However, an application was never submitted to Heritage New Zealand, which would have monitored the works in order to minimise damage and thoroughly analysed any deposits "to contribute to the nation's historical record".
The builders moved in after the house on Main Rd, damaged in the February 2011 quake, was demolished. They began excavations for the new building foundations on October 21 last year.
Builders for Mike Greer Homes Canterbury Ltd, who were engaged by Arrow International (NZ) Ltd, dug up previously unexcavated ground and disturbed "a charcoal rich cultural layer containing shell, bone and fire cracked rock".
On December 18, Nick Cable, senior archaeologist at Opus International Consultants Ltd, notified Heritage New Zealand of site damage at the property.
Heritage New Zealand contacted Arrow and Mike Greer Homes and asked the contractors to desist from further earthworks.
The heritage watchdogs investigated and found that shell, charcoal, fire-cracked rocks and a humerus of a dog had been disturbed.
A report confirmed that one feature was exposed which consisted of a "dark semi-circular shape rich with charcoal and shell, and fragments of fire-cracked rock and bone".
The report concluded: "Although it is not possible to determine the exact extent of damage caused by the excavations for the foundations of a new dwelling, it is clear from the test trenches that the excavations for the gravel and concrete pad have cut through the in situ layer, disturbing at least one feature in the process.
"Based on the findings from the less intrusive excavations on the neighbouring property and the test trenches it is certain that the excavations, which extend over an area of at least 215sq m (the footprint of the new dwelling) have affected archaeological remains..."
At Christchurch District Court today, Arrow International (NZ) Ltd and Mike Greer Homes Canterbury Ltd both pleaded guilty to charges of causing an archaeological site to be damaged or modified without authority, in a breach of the Historic Places Act 1993 and the Crimes Act 1961.
The charge carries a maximum penalty of a $40,000 fine.
Arrow acknowledged "some confusion" between them and their builders over who should have contacted Arrow's consulting archaeologist.
Mike Greer Homes "assumed it was all in place", and claimed that it was advised by Arrow that an authority was in place and that they were not the first contractor on the site.
A lawyer for Arrow today asked for a conviction not to be recorded as the company was considering to apply for a discharge without conviction.
Andrew Riches, defence counsel for Mike Greer Homes, said he was not seeking such a position.
Judge Eddie Paul set down January 22 for sentencing next year.
