City drain doesn't line up with easement!?

I just bought a house from a builder in a new development. There's a drainage easement (from street sewer) that runs along the side of my lot (to a creek). The only problem is, the drain is buried (and the outlet comes out) 15 feet from the property line. The easement is only 8 feet! What do I do? Is this the builder's fault or the city's fault? Who do I contact and what can I likely change?