Were it not for the actions of 10 quick-thinking heroes during last month’s Southern Highlands bushfire, thousands of Wollondilly residents would have been without water to protect their homes.

The 10 men – four from the Sydney Catchment Authority (SCA) and six from the National Parks and Wildlife Service (NPWS) – swarmed around the Nepean water filtration plant on Thursday, October 17, and kept it safe from the flames.

If the plant had burned,  24,000 residents in Picton, Bargo, Thirlmere and The Oaks who rely on the Nepean and Avon dams would have lost their water supply – both for drinking and for trying to save their homes from burning.

SCA compliance officer Shane Muldoon raised the alarm about the danger the blaze posed to the  plant.

‘‘Our fire tower at Avon had called in the smoke sighting and I was on fire patrol that morning with a couple of other fellows because it was a high fire danger day,’’ Mr Muldoon said.

‘‘I went up on the hill to see what was happening and I could see the fire spotting in front of itself, about  half a kilometre at the time.

‘‘Looking at the path of the fire it was going to impact on Nepean.’’

He rang the SCA  hotline and met  the three other  firefighters on duty  to work out what to do.

Six firefighters from NPWS, who had been fighting a fire at Yerrinbool the previous day, arrived and agreed to help.

‘‘If there were only four of us, I don’t think we’d have saved what we did,’’ Mr Muldoon said.

About 30 minutes before the fire reached the Nepean depot, the 10 men set about preparing it to withstand the flames by wetting down all the buildings and filling up the gutters with water.

‘‘The first sense we had that the fire was close was at 3pm with the sky getting redder and redder and the heat from the valley was intensifying,’’ SCA firefighter Colin Heaslip said.

‘‘For a few moments we just stood there waiting.’’

Then the fire came up the gully and over the depot.

‘‘It turns day into night,’’ Mr Muldoon remembered.

‘‘Then you get this orange glow, and then the heat intensity of the fire comes through.’’

Mr Muldoon began overseeing the efforts of the other firefighters, smoke stinging his eyes because his goggles didn’t fit over his glasses.

Flying embers hit the men in the face and back.

The firefighters moved from one spot fire to the next – from one near the helipad that threatened a shed full of aviation fuel, to another housing machinery.

‘‘When the fire front passed we then moved our resources down to the filtration plant. As the fire moved on we moved with it.

‘‘There was still fire in the area  but  it was safe enough for us to enter because the heat intensity had passed.’’

Flames were attacking several buildings. One  inside the filtration plant’s fence was quickly dealt with. Other buildings at the top of the rise were also on fire but Mr Muldoon said they were left to burn as there was still power running to them and pouring water on them would have risked electric shock.

The 10 men spent the next eight hours keeping the flames at bay, and a look at the plant yesterday showed how close the fire came.

One side of the plant is built into a slope that is completely blackened and features the stumps of many burnt-out trees.

 Detached hoses lying nearby have been charred and melted. The corner of the main building  shows scorch marks.

 On the rise overlooking the plant are burnt-out buildings and blackened trees.

In other areas the vagaries of fire are obvious. Down the road from the plant is a toilet block and administrative office completely untouched.

Stand in front of it and you might think that no fire came through. But turn around and you see a valley of blackened trees and it becomes clear that the fire simply leapt  the spot you’re standing on.

It also becomes clear just how brave those 10 men were – or indeed anyone who stands in the way of an unpredictable fire.

NSW Primary Industries Minister Katrina Hodgkinson, who visited the plant on Monday, praised the 10 men as ‘‘heroes’’.

‘‘This was a very hot and very violent fire, and when it came through here the winds were about 80 to 100km/h that day,’’ Ms Hodgkinson said.

‘‘So it was a pretty dangerous place for them to be. It was very brave of them to put themselves between the filtration plant and the fire. I reckon they’re absolute heroes.’’

Wollondilly MP Jai Rowell was also on hand to inspect the efforts of the men.

‘‘What the guys did here was nothing short of a miracle,’’ Mr Rowell said.

‘‘I was out here for the nine days of the fire and in one of the briefings, this was one of the areas everyone was worried about when it hit. So to see it still up is good.’’