Gravel packing apparatus and method. The apparatus can include a conduit configured to extend between first and second wellbore intervals and through an isolation valve assembly separating the first and second intervals. A sliding sleeve can be configured to slide between an open position and a closed position. When the sliding sleeve is in the open position, it is configured to allow a flow of gravel slurry through the conduit between the first and second intervals, and when the sliding sleeve is in the closed position, it is configured to completely isolate the first and second intervals from each other.