June 1999 L.A. Sewage Spill during Y2K Test According to City of L.A.

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"When the power was disconnected and the generator turned on, the gate automatically closed, despite the previous command. Over the past week, it has been determined that two separate circumstances contributed to the gate closing and the resulting spill. The Tillman Plant has a number of Uninterruptible Power Supplies (UPS) for its various computers providing backup power. One UPS, which backs up the computer controlling the AVORS gate was not working. It was down for maintenance. Ordinarily, this should not have presented a problem. In the absence of the UPS, the computer simply reboots when the emergency power comes on. This brings up the second circumstance. The programming language written for the computer that controls the AVORS gate requires the gate to be closed as step one when the computer reboots (default closed). The reasoning for this instruction, that was prepared in the early 1980's, remains a mystery.

The logical sequence for rebooting would be to open AVORS so that flow would continue on to Hyperion. Presumably, if you are in a situation where the power to the plant has been lost and you are operating on a generator, the plant is in trouble. Sewage flow should bypass the plant and continue on to Hyperion until everything is stabilized. The staff has combed through the original computer code to find an explanation as to why this was not done.

Memory capacity of the early 1980's generation computer system at Tillman is extremely limited. The computer did not have sufficient memory to "remember" its previously set position prior to the power shutdown (i.e. AVORS diversion gate open). When the computer rebooted, there were two options available to the programmer who wrote the commands in the early 1980's. The initial command could have been open (to a maximum of 40%) or closed.

It has been speculated that this instruction for the gate was intended to simplify operations by minimizing the need to manually close the gate if that became necessary. This thinking is totally counter-intuitive and staff working on the Y2K exercise that night was not aware of this unorthodox operating command. If the reboot command been more logically written to open the AVORS diversion gate, (40%) there would not have been a spill."


"C. Spotters in all Plants and Major Pumping Stations

We may not be able to trust our control panels in a Y2K event. We cant be flying blind. We will need personnel in the field as our eyes and ears."



Tom, who is evacuating L.A. around 12/27 or 12/28.

-- Tom (Y2KOhNo!@Yikes!.com), December 21, 1999


By the way, I know most of you know about the failed Y2K test. I just thought you'd be interested in the City of Los Angeles' version of the failure.

Tomorrow, I'm going to finish transporting my extensive preps to my remote location far enough away from L.A.. I'm just wondering if I'll be able to return anytime soon.

Thanks to everyone for the helpful, invaluable info you've provided.

Wishing all of you, doomers and pollys too, the very best in 2000!


-- Tom (Y2KOhNo!@Yikes!.com), December 21, 1999.

Best to you, too, Tom. Thanks for enlightening us -- I have two civil engineering friends who were happy to read your post.

-- (ladybuckeye_59@yahoo.com), December 21, 1999.

And then this is what the California State Water Resources Control Board had to say in its Case Study Evaluation on this "preventable" matter:


"The spill, which was the result of a Y2K preparedness test of Tillmans emergency power system, was caused by inadequate planning, poor communication, by the treatment plant staff and management responsible for developing and implementing the testing procedure...

"The major contributing factor to the "unexpected" diversion gate closure was that a critical uninterruptable power supply (UPS) unit serving the local computer, Area Control Center (ACC) #3, was out of service during the test. The incident was entirely predictable since most of the key staff were aware that this particular UPS was out of service for at least 11 months prior to the incident. Several staff were also aware that a power failure at ACC #3 would result in a default closure of several gates, including the 8-foot diversion gate that controls the flow in the AVORS line...

"Tillmans operations management, including the Chief Plant Operator (CPO) and the top senior operators, were unaware of the problem with the gate during the power failure even though other supervisors and staff were aware of the potential for gate closure during a power outage with UPS #3 out of service. This indicates a lack of communication, inadequate contingency planning or both."

and other damning conclusions

-- Brooks (brooksbie@hotmail.com), December 21, 1999.

So is there any recent info as to their status at present? I guess all there is to offer are the "feel good...everything's going to be just fine" stuff right? I have a sis that lives in LA. I'm not even sure she's aware that the park incident occurred. Did the press cover it well when it happened?


-- beej (beej@ppbbs.com), December 21, 1999.

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