The car fishtailed, leaving skid marks for 57m before hitting a stationary truck and bouncing off across the other side of the road, where it came to a stop a further 25m away.
An investigation by the serious crash unit indicated he had been driving between 99-111km/h in the 50km/h zone.
Nepia and three of the four passengers in the car were injured. The most seriously hurt suffered multiple pelvic fractures and dislocated the ball of his hip on the left side.
Nepia himself suffered a fractured knee.
A subsequent blood test showed he had a blood alcohol level of 146mg per 100ml of blood, well over the legal limit of 80mg.
Nepia told police afterwards that he "couldn't remember" the incident and wanted to put it out of his mind.
About six weeks later, on January 6 this year, Nepia was stopped by police, again driving while disqualified and with two young children in the car.
He pulled into his home address before stopping the car, getting out and attempting to run into his house with his children.
He was arrested in the doorway and initially denied driving the car.
Nepia's counsel, Stephanie Burlace, said it was a very serious accident, and there was no other way to describe it.
Nepia himself said in his pre-sentence report he was thankful no one was killed.
It could have been far worse for himself and his friends.
His memory of the accident had still not come back, and he didn't remember getting in the car to drive. He had not fully understood how serious it was, but apologised to his friends, who supported him. His family were trying to get him to understand the seriousness of the incident and also how lucky he was.
That was a reflection of his maturity more than anything, and he knew what he did was wrong, she said.
She suggested a sentence of home detention coupled with a driving disqualification.
Judge Matheson said Nepia's report showed he was unemployed, has three children, and clearly had a problem with his consumption of alcohol.
His previous convictions included a number of driving offences, and he was disqualified at the time of the accident.
His report writer had expressed concern about his lack of understanding of his actions, and reported him as saying he didn't see why the accident warranted court action.
"That didn't impress probation, and that doesn't impress me," Judge Matheson said.
The judge said he was deemed at a low risk of reoffending, but his history spoke louder than any technical assessment tool.
It was aggravating that there had been injuries, it was premeditated driving - he had been to court and knew he wasn't supposed to drive.
He had pleaded guilty early, but his second driving-while-disqualified offence devalued any remorse and showed blatant disregard for the law, made worse by the fact he had his kids in the car.
Judge Matheson said he rejected home detention as an option, because he had been given a chance when he was disqualified from driving.
Nepia had shown contempt for authority and Judge Matheson held no confidence he would comply.
