When my house was built a few years ago, the builder brought the waste line clean out up into the driveway. Then when the concrete driveway was poured, they never enclosed the cleanout in a vault box or frame and lid--it's just a smooth PVC pipe sticking up about 4" out of the driveway, with a light-weight press-in cap.

I want to cut the pipe flush with the driveway and cap it but I'm concerned about not being able to seal the pipe since it's smooth preventing me from using a typical threaded waste line cap. And with the pipe embedded in concrete, I'm not sure what to do.

Someone suggested cutting the pipe flush with the driveway and inserting a slip line with an expansion seal inside the pipe (vapor seal) then put a metal cap over that so a car can drive over it without damaging the pipe. However, I'm unable to locate an expansion type seal--does something like this exist?

Any advice other than not use that builder again? Thanks.