I found an article from the June 26th edition of the Bucheon Herald (for some reason their website doesn't allow you to directly link to individual articles) which identifies the excavation on Wonmisan as the creation of an embankment for the extension of the Meolmoe Street (멀뫼로). These pictures tell the story as well.
Here's a map with the current location of Meolmoe Road (멀뫼길) marked in red. I can only assume that Meolmoe Street will be an upgrade of this road, which goes under the name Meolloe from Sosa Station to the intersection at Bucheon Stadium. It continues on at both ends, Southward uder the name Buil Street (부일로) and Northward as Yeowol Street, I believe. It would seem natural that this stretch of road between two streets get an upgrade.