A double walled riser sump has an annular space between the two walls. The provision of the annular space provides for monitoring the integrity of the two walls of the sump. The two walls of the sump are preferably separated by a thin film or a distance fabric that allows the passage of fluids, and preferably liquids. The annular space may be in fluid communication with a reservoir holding a monitoring fluid and positioned near the top of the sump to be easily accessible. In some embodiments, a top of the riser sump is also double walled and the top annular space is in fluid communication with the annular space between the vertical walls. If a leak develops in either wall of the sump, a corresponding drop in the fluid level of the reservoir will occur.