"It is sad we found out at the end of the day, we aren't able to let clients know."
Customers mainly used the free parking as there was only 30-minute parking on the Onehunga Mall road and a cut usually took between 45 minutes to an hour.
"This is the first time I have heard about it."
She did not know where else clients could park as the area had become "quite busy" in recent years.
Nearby store Hard to Find Books recommended customers use the carpark but it was almost always full.
Spokesman Brendon Harrison said the space was frequented by commuters parking their cars before catching the train to work.
"Customers complain they can't find a car space. It's a very busy area now.
"People around here are the most hopeless parallel parkers," Harrison said.
Look Sharp Store Onehunga manager Keshwh Nadin said he and other staff members used the free car spaces every day.
"All of our customers and staff use the car park, but now a lot of people park there and take the train to work.
"It's very hard to find a park, you have to circle around to find a space."
The park was already widely used and would be full up with commuters as early as 8.30am.
Nadin said he and staff would have to switch to parking in the library, but expected others to quickly follow suit.
A safety barrier would be put in the affected area tonight, AT Chief Engineer Andrew Scoggins said.
"This is a precaution after engineers raised some concerns about the state of the wall."
"We regret any inconvenience but safety is our first priority. If we have more heavy rain the wall could deteriorate even further."
Auckland Transport is currently assessing repair options for the wall.
There was no concern for neighbouring properties because the car park fronts on to a large empty section, Scoggins said.
A report by BECA said "This wall is considered to be in a high-risk, failed state, and any further loading from a range of potential triggers could destabilise the wall further".
"Further movement will likely result in a catastrophic failure, which would be a safety risk to any people nearby."
The engineers recommended that the best value for money would be a remediation solution incorporating a mesh and shotcrete skin, tied to a dead-man anchor at the top and anchored in the middle.
The cost of that would between $300,000 and $400,000, while a full rebuild of the wall could be in excess of $2m.
"We recommend that a full survey be undertaken of the wall and the ground above and below, including the carpark and road footpath above, and at least 5m out from the toe.
"A geotechnical investigation comprising at least two machine boreholes is recommended for all remediation options."
It follows on from Auckland Transport rejecting advice by engineers to install an "early warning system" to monitor unstable land long before two massive slips in Birkenhead that could cost up to $24 million to put right.
The warning bells were sounded in 2015, two years before the first slip swept away 25 carpark spaces in October last year, followed by a second, larger landslide in November that sent a drilling machine tumbling into the Rawene Reserve and workers scattering.
Auckland Transport and Auckland Council officers knew from February 2017 that a leaking stormwater pipe was causing cracks to the carpark but it was not fixed before the first slip. Council said it was unlikely stormwater pipes played a significant role.
It was not until two years later from the first warning bells on September 14, 2017, when large cracks appeared in the car park, that AT brought back a geotechnical specialist to check the ground and its stability.
