Three months after 40,000 residents were left without water for days, a £3 million operation is underway to lay two new vital supply pipes.

It was in July, during some of the hottest days of the year that taps ran dry in homes, businesses, schools and holiday parks on the Isle of Sheppey. The main delivering water onto the Island had burst - and then it broke again.

Video: Drilling site

As thousands of emergency bottles of water were handed out from makeshift distribution centres, Southern Water promised the disaster would never happen again and set to work planning a replacement supply.

In record time, it completed sensitive negotiations with different agencies to get permission to sink two new pipes beneath the Swale.

This month, a rig arrived on the mainland near Ridham Dock and work began drilling two bore holes to augment the two existing pipes, one of which goes over the Kingsferry bridge.

On Tuesday, bosses revealed they were already a third of the way along the first bore. They won't say when the work is expected to be completed but the website suggests it could be finished by the end of the year.

Sheppey already has an 18-inch (457mm) pipeline built in 1960 which runs along and under the bridge and a larger 2ft (600mm) pipe built in 1979 running under the Swale. The two new pipes will each be 15-inches in diameter (400mm) and will be linked so water can be switched between them should one fail.

After the new mains are installed, engineers will strengthen the bridge pipe to use as an emergency backup.

Peter Simmons, 56, is the senior project manager making sure it all goes to plan.

He explained: "We are currently drilling the first pilot hole. We will need to make four or five passes, each time increasing the size of the drill bit, until we get to the right diameter. Then we will pull the new pipe through from the Sheppey side and then start on the second bore."

The new blue pipe is already waiting on the Sheppey marshes. It arrived in 10m lengths and has been welded into one long 500m strip so it can be pulled under the Swale in a single movement. It is so long that part of it is stored along the old Ferry Road.

Temporary rollers keep it off the grass in case it crushes any great crested newts. The Sheppey marshes are an area of special scientific interest. Whenever the grass is disturbed the area must be searched and any protected wildlife moved to safety by an ecologist.

Despite the speed of completing the paper work, drilling is not easy.

Mr Simmons admitted: "We are drilling through different silts, peat, gravel, stiff London clay, shell deposits and even fossilised root fragments from what could be a prehistoric forest. But we were expecting them as they were detected during our initial surveys."

There was also a search for any unexploded bombs which might have been resting on the bed of the Swale.

The drill uses its own guidance system. Water, which is pumped through hollow rods, does most of the cutting. It is then returned to the surface as slurry which is cleaned and used again.

Katy Taylor, the water firm's chief customer officer, said: "We are spending £3 million to put two new pipe lines across to the Isle of Sheppey after we unfortunately lost water supplies to the Island for two days in the summer. We only had two pipes at the time and both of them burst because of the additional demand and the dry weather had compacted the soil around them."

She added: "This will make sure it won't happen again and lead to a more reliable and resilient water supply for the Island."

Southern Water has also given £30,000 to community organisations to thank them for helping during the emergency. Among the recipients were the RNLI, town and parish councils, the Sheerness Festival of the Sea and Swale Pride celebrations.