NSW Neighbour Reporting to Council about Noise Pollution

Hi guys, could use some info on this matter.

I own a small transport company that deals with shipping containers. Late last year, I bought a block of land in an Industrial area zoned 4C.

We applied for our D.A (which I'm not sure why we need one as we're not building but only storing an odd container maybe once or twice a week and using it to park up our prime movers and trailers.)

Directly next door to us is a private residence. This used to be a residential zone but over 40 years ago it was rezoned, the person living in there is 90 years old and needs 24 hour care. He is still active, walks/talks and understands fine, he was hit by a car a few years ago and since then needs care.

Before we bought the property, we spoke to the nurses and the gentleman. They were excited that they were finally going to have new neighbours. I told him, generally we will start 6am and finish 6pm and every now and then a prime mover may return to base between the day for between 15-30 minutes. He was perfectly fine with this and for the first few months, while still waiting for our D.A, he would come out and watch us work and talk us.

Eventually this all stopped, he became distant and so did his nurses, then his son would come and photograph us working and complain to the council.

The council ordered us to cease until we got the D.A approved, we did for a a good 5-6 months and we started parking on the streets, however, this led to slashed tyeares, trucks broken into and kids from nearby playing and jumping on our trailers and playing with buttons/levers. We continued to work off the street but then the neighbours complained about us parking on the street.

So we moved back into our depot and started working from there again, this now led to a confrontation with the neighbor's son who doesn't live there, who has also been getting the nurses to film and photograph us while we start our trucks in the morning and work during the day.

From my understanding this area is industrial 4C (light industry), our D.A is for a transport terminal, for the loading and unloading of trucks which falls under 4C (this was on council website and checked before we applied for DA)

Our prime movers do make noise in the morning, they need to warm up and build air. Occasionally we need to swap containers using our sideloader. This takes 10 to 15 minutes and again is noisy but it's a one off noise during the day maybe once or twice a week.

I sympathize with our neighbor, I have tried to be as accommodating as I can by starting later and getting drivers to swap on the street away from the house but it feels like this guy's son wants to kick up a big stink to get us kicked off our land for noise pollution.

So I'm wondering, what's the worst that can happen to us here? How much can he complain to the council / police or EPA?

Thanks for any feedback!