There was a very heavy rain storm on the morning of 2019-10-18. It was the sort of deluge that overflows the gutters and lifts the drain covers (not literally, but the water was forcing its way out of the drain cover sides and 'boiling' 5cm into the air !). During a visit to the observatory the following day, it was noticed that there was a distinct feeling and sound of water squelching under the rubber floor tiles, and looking down there was water coming up through the gaps between tiles when pressure was applied.

Pulling back the floor tiles and investigating revealed a huge puddle on water on the floor of the observatory, both on top of and under the plastic membrane. 

Pictures of the Puddle on Observatory Floor following deluge on 2019-10-18

 The rubber floor tiles were lifted and removed and towels used to soak up the large puddle of water. 

After the puddle was cleared an investigation began into how the water got into the observatory: 

•  there was no absolutely no indication that the water had come through the roof, walls or door of the observatory
  • the inside surface of roof and walls were all dry
  • there were no splashes or water on top of equipment etc
  •  the top surface of the rubber floor mat was initially dry when first entered, except for water along the jins between some of the tiles
  •  the carpet floor mat just inside the observatory door was dry.
     
• the water could therefore only have come from below the floor or from under the walls.
  
• water influx via the pier bolt holes (athough an initial canidate) was ruled out
  •  after drying there was no continuing any seep of water from around pier base, but there was water still evident under roof walls.
• water influx coming up through the concrete floor (athough an initial canidate) was ruled out
  •  although the central part of the floor remained much more damp that around the edges which looked relatively dry; this was due to the fact that concrete floor sealant was only put down around the outside and under wall parts of the concrete pad.
    (water had seeped into the floor from the puddle above, rather than had infused upwards from the underlying water table)
• water influx coming under the walls of the observatory is the most-likely point of entry
  •  at least 3 points of obvious weakness in the sealant around observatory wall was noticed
  • one was a small hole in the concrete that corresponded to an aborted drill hole when installing bolts for the fixing the dome to the concrete pad, its about 1.5cm deep and may have allowed water to get under the wall, and corresponds to a damp patch on the floor on the inside
  • two were a line of weakness in the sealent, either a line of weakness between sealent and bottom of dome roof or line of weakness between the sealent and the concrete pad.
  • water continued to seep through from under walls for 3 weeks following initial remedial fix to the sealent around base of outside wall
• water influx coming up the bolt hole used for pinning the observatory to the concrete pad couldn't be ruled out, but is less favoured
  • water that appeared to be seeping from under the observatory floors could have equally been coming up from the bolt holes
  • however its not thought that any of the bolt hole was drilled deeper than the thickness of the concrete pad,
  • if one of the holes had breached the pad its doesn't explain why water appeared to be seeping from multiple places along the wall base.

Investigating how the water got into the observatory (2019-10-19 & 2019-10-20)

First Repair Attempt
An emergency repair was made a few days later in which the sealent was replaced along all the sections of observatory based with obvious weakness. However this remedial repair was unsuccessful and water continued to seep under the walls from multiple points.

It was concluded that the repair had failed and during a second remedial repair on 2019-11-18, it was evident that the sealent in the first repair attempt has failed to bond to the concrete, during to dampness in the concrete and the seep of built up water still lingering under the wall.

Sealent along observatory base was eventually fixed by a second repair fix on 2019-11-17 / 2019-11-18