Sinkhole Collapse under Commercial Property Form

Q

Our insured's building is covered by the building and personal property form (CP 00 10 04 02), with special causes of loss (CP 10 30 04 02). The building has a system of pipes that divert water runoff from the roof into a retention basin. Suppose that one of the pipes breaks, and the water runoff erodes the underlying limestone, causing the building to collapse in the hole created. Is this event covered by the policy as “sinkhole collapse?” We are concerned that the retention basin might be seen as “man-made,” thus excluding coverage for collapse.