Meanwhile, a burst main has been repaired but continues to affect supplies to Miskin, near Cardiff, and Ynysybwl in Rhondda Cynon Taf while the system is "recharged".
In the second crash, about 20 minutes later, a car crashed down an embankment on the westbound side between Junction 34 at Miskin and Junction 35 at Pencoed.
However the company, based in Miskin near Llantrisant, said it was facing the worst economic downturn for decades, and had decided to recommend closure to its board, transferring work to Hungary in 2011.