Spool connecting BSC5 to GV15 will be removed soon.  Need to decouple annulus plumbing from spool-to-GV15 flange, requires venting GV15's annulus volume, this volume has never been vented, don't know if inner O-ring(s) will leak into CP6/X2 module ->  First I isolated the ion pump body from the rest of the annulus piping, then I shut down the aux. pump cart connected to but isolated from GV15 and changed the setpoint at which the turbo starts to a value below what the diaphram backing pump could achieve.  Next I started the pump cart and let the pressure come down to the ultimate pressure of the diaphram pump (~1.5 torr).  Next, with Gerardo monitoring the pressure in CP6/X2 module, I valved-in the pump cart into GV15's annulus and Gerardo confirmed that CP6 pressure was unaffected.  Now I opened the orifice (vent port) and the hanging turbo which resulted in the annulus volume settling in to around ~200 torr.  Still no change in adjacent volume pressure.  Finally I shut down the aux. cart and let the annulus volume fully vent -> No leak.  

Decoupled piping from spool flange and blanked-off both (decoupled) flanges -> Pumped GV15 annulus volume with pump cart, opened pump body to rest of piping and restarted ion pump.  Isolated pump cart from annulus.

Removed RGA from BSC5. Now Apollo can remove spool from between BSC5 and GV15