Over the winter Scottish Water have been laying new pipes between Howden and Yarrowford Treatment Works.
But last month work ground to a halt after the foundations of a major settlement were found at Philiphaugh - just a foot or so beneath the surface.
Specialists had been brought in to check a stretch of the planned pipeline route, just a few yards from the known Battle of Philiphaugh site.
And what they found has surprised many.
Scottish Borders Council's archaeologist Chris Bowles told us: "We knew there had been something there, we just didn't know where it was. Now we have the village, and it is quite an extensive village.
"We have got a really extensive area of maybe half a kilometre where we have had buildings right along the road running to the salmon viewing centre."
Items found on the site - which include a few pieces of pottery, a badly eroded coin, and, what are believed to be, two ancient fire hearths - will now be examined and carbon dating used in a bid to give a more precise dates for the settlement.
Aerial photographs of the field at Philiphaugh showed crop marks, which initially suggested there may have been an Anglo-Saxon settlement on the site.
However the trench alongside the A708 appears to have thrown up a Medieval village on the site.
Mr Bowles added: "It's not every day you find a Medieval village. Most are either built upon or you knew about through documentation, but we had no idea this was there.
"Medieval documents do mention Philiphaugh House, which was where the cricket club is now, and village - but we had no idea where the village was.
"This is a very exciting find. All we know for certain at the moment is that the village wasn't there when the Batttle of Philliphaugh took place in 1645."
This latest discovery lies just a few miles south of another lost Medieval village at Sunderland Hall.
And there is already debate about why they were deserted - including the theory about them being ransacked by English armies during the turbulent 16th century.
Local historian and author Walter Elliot believes the Philiphaugh finds could date back even further - and possibly be the original Selkirk.
He told us: "I do think the original Selkirk was here.
"It was the site of an Anglian civilisation - somewhere between 600 to 1000AD.
"We have known about the site for some time because of the aerial photographs and it is exciting that we now have proof on the ground."
While the archaeologists can't be 100 per cent certain of when the foundations date from, there are a number of stone buildings with stone floors across the entire area, with cobbled areas in between.
Archaeological digs have already taken place on the field nearby in a bid to paint a clearer picture of the Battle of Philiphaugh.
Interpretation boards have already been erected and a new booklet, being published by Philiphaugh Estates, will be released later this year.
Local Councillor Vicky Davidson said: "We'll have to update the interpretation boards after this latest exciting find.
"Philiphaugh has always been an important historical site - but it looks like it will be even more important after this latest find."
Guard Archaelogy, who carried out the dig on behalf of Scottish Water, will study and carbon date the finds over the coming months at their laboratories in Glasgow. And the current trenches will be covered over again during the next few weeks.
Stewart Cooper of Scottish Water's corporate affairs team added: "The Borders is of course a particularly historic part of Scotland. While projects of this kind by Scottish Water are all about improving Scotland's water infrastructure they can often involve an element of digging and excavation - which can be fascinating when they help shed light on an area's past."