What is the main conflict in The Engines of God by Jack McDevitt?

The story begins with the anticipated terraforming of a planet called Quraqua called Project Hope. It is the hope of those on Earth that this will be a new start. It is the year 2197 and archaeologists are trying to uncover the meaning behind the monuments they have found and those who created them. Quraqua is deserted now, but archaeologists have uncovered ruins that may hold the key to the Monument Makers. They scramble to uncover the last of the ruins before the terraforming project begins and covers them permanently.