While watching a story from 1989 on the National Geographical channel yesterday, I immediately felt that it was a Mercury retrograde event. So I decided to research it, and low and behold it certainly was.
It was about a San Bernardino CA train disaster, and the subsequent failure and explosion of a petroleum pipeline there later on May 25th which was caused by damage done by earth moving equipment during the crash cleanup. These were two related incidents; the duality definitely a Mercury related clue.
A chart for the first event, the derailment on May 12th at 7:36 AM is indeed telling.

Notice that retrograde Mercury then was at 6 Gemini 51; strong in its own sign and in the 12th house of sorrow. And remember that Mercury rules communication, transportation (trains). In fact, there were three other planets that were retrograde then..Uranus, Neptune, and Saturn.
So what happened was that the train was carrying trona (a material used to make fertilizer) that had been mined and loaded onto the freight cars for shipment to a buyer. The buyer had purchased 6,900 tons of trona; thus the mining company contracted for 69 100-ton hopper cars. When the mining company turned in the final contract to the clerk for the bill of lading, they had not filled in any weight, assuming that the railroad would know that they had filled the 100-ton cars to capacity. Since something had to be filled in in that paper work slot, the clerk wrote down 60 tons per hopper car, going by a visual comparison of 100 tons of coal. As a result, the train was listed as significantly lighter than its actual weight.( First Gemini mistake that day).
Engine #2 of the first four engines did not have any dynamic brakes, just air brakes (also, the locomotive was dead-in-tow since the crew couldn't get the 7551 started), engine #3 did have dynamic brakes but they operated sporadically. Engine #6 (the last one of the two helper engines in the back) also did not have dynamic brakes. This information about the last engine was not passed on to the lead engineer (second Mercury mistake that day).
Thus, the engineer had faulty weight information and faulty information about his braking power to work with when was calculating his maximum descent speed down the steep mountain pass. When he realized that the train was gathering too much speed, he did all he could to brake the front engines and asked the helper engine engineer to do as much as he could to help also (not knowing that he had only one working engine braking in the back). As a last chance to stop the train, the helper engineer activated the emergency brake, unfortunately this canceled all the dynamic brakes on the train, allowing the train to pick up speed (another mistake). After the activation of the emergency brake, the only brakes which were operational were the air brakes, which were melting. As it ran away down the treacherous Cajon Pass, it reached a speed of 110 mph (177 km/h) on a curve at Duffy Street in San Bernardino that was designed for no more than 40 mph. Can you just imagine how the crewmen felt as they approached that curve at that runaway speed? At that speed, and with the friction of the brakes, the wheels were actually melting when the train left the track in its destructive crash.
The conductor, head-end brakeman, and two residents were killed in the crash. Seven homes were destroyed, as was the entire 6 locomotive/69 Southern Pacific freight train. So the numerous Mercury tie ins that day were that the yardmaster in Barstow miscalculated the weight of the train which in turn affected the brakes, and caused the helper engineer to press some wrong buttons in trying to slow the train down.
Some of the other aspects that were operating then were the Sun in the 12th house of sorrow at 21 Taurus 50 squaring the Moon at 21 Leo 58; within only 8 minutes of arc. The Moon ties in to the seven homes that were destroyed. the Part of Fortune at 19 Virgo 50 in the domestic 4th house T-squared to the first and 7th house cusps at 19 degrees and 42 minutes of Gemini and Sagittarius respectively tells us that the houses were way too close to the train tracks to start with, and they certainly paid the price for it. And Neptune conjunct the 8th house cusp points to the life and death part of the whole story.
The next episode of this story manifested on May 25, 1989 at 8:05 AM. Buried six feet underground along the railroad right-of way is a 14" high pressure gasoline transit pipeline operated by Calnev Pipeline. At that precise time, the pipeline burst, showering the neighborhood in gasoline, and ignited into a large fire which killed two people and destroyed eleven more homes. Pluto retrograde tells us how wrong they were about the underground danger that was lurking, and went undiagnosed. Another wrong judgment, and huge mistake.
The total property damage was $14.3 million. Many residents moved out after this, and homes are no longer allowed to be built next to the rail lines. The chart for this event is also very interesting.

Mercury was still retrograde then, and as it was on May 12th The Sun by then had moved up to 04 Gemini 22 conjunct the sorrowful 12th house cusp and formed an 8th house inconjunct to retrograde explosive Uranus at 04 Capricorn 30 in the 6th house. Jupiter at 15 Gemini 06 formed a looser inconjuct to retrograde Pluto (underground) at 13 Scorpio 13.
What's most interesting though, and certainly binds these two events together is that on May 25th, Mercury had retrograded back to 01 Gemini 44 which conjoined the Venus placement at 01 Gemini 39 in the May 12th chart. And they both formed a T-square to the nodes at 00 degrees and 08 minutes of Pisces and and Virgo respectively. So this Mercury to Venus set off the second tragic event. The Part of Fortune at 06 degrees of Pisces ties into the fact that 6 people were killed in the two events.
A sad story like this should remind us not to second guess anything when Mercury is retrograde, and not to go digging to far below ground when Pluto is retrograde!