The following tasks were completed over the past 2 weeks:

- Aquarium Technology Ltd. (UK) was contacted regarding best method for replacing window seal.  A detailed procedure was provided (attached below)
- The warm cell windows were determined to be acrylic, not glass.  Estimated weight: 450lb per panel

- All water in the warm cell windows was released to grassy area outside the lab after approval from Gord Wood (OH&S) and Joe Mildenberger (RPG)
- Warm cell was cleaned up and blocks were configured to make fields as low as possible in the work area around the windows (~2micro Sv/hr max field around windows).  No contamination found on warm cell floor.
- The old seal around each window was cut mechanically with a thin blade
- The panel spacer rods were removed  (most were constructed of SS and Al, however a couple were mild steel and were badly corroded)
- The window panels were separated from the frame using a rubber mallet and moved to the center of the tank (the panels were not removed from the tanks for this repair)
- The old seal material was removed from the panels and the aluminum frame using WD40 or mineral spirits to help break it down (this was a very tedious and unpleasant task)
- Pitting due to corrosion was found in various places on the aluminum frame.  It appeared to be worst where mild steel spacer rods were used, and also worse at weld locations (see attached photo).  Max depth of pits ~1/8"
- The corrosion was cleaned as much as possible using a wire brush then rags with mineral spirits
- A final clean of sealing surfaces was done with isopropyl alcohol
- A deep pit (~1/4" deep) was found on the inside of the inside of the aluminum frame on the west tank, south window (see attached photo)
- This pit, as well as some other smaller ones on the same side were filled with Dow Corning 791 sealant material

- Rubber stand-offs (Digi-Key #SJ5009-0-ND) were installed on the frame side in the center of the sealing faces (3 top, 3 bottom)
- The panels were moved back into place resting on 3/8" thick aluminum spacers (see attached photo).  These replaced spacers of the same size and material that were slightly corroded

The following tasks remain to be completed:

- Install panel spacer rods (mild steel rods to be replaced with SS or Al)
- Apply sealant to all panels from outside the tank as detailed in the procedure using 20oz pneumatic applicator caulk gun (PO: TR206556)
- Install corrosion inhibiting pads inside tank.  Will use 6 pads per tank, (4x McMaster 3609K2 & 2x McMaster 3590K2 per tank)
- Perform final clean of inside of windows and tank
- After 14 days cure time fill tanks with city water and allow to sit to check for leaks
- If leak tight, use water in tanks to back-flush the sand filter
- Refill tanks and start pump with filter in normal mode
- Occasionally check for water leaks and check status of pitting inside tank over the coming months/years
- Also monitor corrosion inhibiting pads and replace or change materials if necessary

Summarized Seal Replacement Procedure provided by Aquarium Technology Ltd:

1) Cut out the viewing panel entirely and mechanically clean all sealant traces from both the panel and the frame bearing faces of the tank structure

2) Degrease all sealing surfaces with something like pure petroleum spirit (mineral spirit) which won't harm the acrylic

3) Reinstall the clean viewing panel spacing it off the frame bearing face by around 10mm using self adhesive rubber stand-offs  (depending on panel flatness likely no more than 3 needed along the top and bottom)

4) Brace the panel in place, mask off the frame and panel, and then inject Dow Corning 791 sealant from the outside.  Ensure that the sealant goes in under pressure, fully wets both surfaces, and completely fills the void.

5) Allow the sealant to cure for 10-14 days before filling the tanks