The 4" PVC drain line in the ISAC-1 active sump was modified so that the drain pipe terminates below the low level water line of the automatic pump-out system.  This will prevent backflow of sump gasses into the SHC, NHC, or TCS space if the air pressure in any of those rooms are lower than the sump air pressure.  The details of the modification were specified by Mechanical Services Group, and the work was done by Paul Jensen.  This system is defined in drawing IAM19183.