Sewage Release in Front of Elementary School

On Friday October 6, 2007 some children leaving Tommie Barfield Elementary were entreated to a sewage release in front of the school. They noted the effluent and the odor. City workers responded - they spread a white powder on the areas soaked with the effluent and pumped the nearby lift station(s). There is no mention and/or explanation from the present governance. The following is a possible explanation of what could have caused the sewage release in front of the elementary school. The author/resident has asked to remain anonymous and merely provided the following as a public service until if and when the present governance factually describes the events/causes that led to the sewage release in front of the elementary school.

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In an effort to gain capacity at the plant for the addition of dewatering effluent to the force main system, it is entirely possible that certain lift stations would be temporarily shut down. As the flow from the gravity lines usually going to that lift station does not get moved on down the line to the plant it starts to back up. It fills all the pipes and then fills the manholes in that area. This process is called surcharging and is often done to lessen flow at the plant during periods when equipment is down for repairs or flow is too high to handle. It is not an approved process, but it is done everywhere.

Usually if the decision to surcharge certain parts of the system is by design then the lift stations are operated occasionally to keep the sewage contained within the piping and manhole structures, however, if this is done, all you do is gain the time that it took the system to fill up and then you have to operate just as you would if you hadn’t surcharged the system in the first place because the sewerage is still entering the system at the same rate day after day.

Obviously if this surcharging get’s away from the operators, or they didn’t know it was happening as in the case of a non telemetered or alarmed lift station, the event that you observed yesterday might be the result. The manhole at the lowest part in the system served by the inoperable lift station will be the first to lift, spewing sewerage around its location and thereby relieving the hydraulic pressure. If more than one manhole is at the same level, then you would likely see them all lift.

One additional point is the use of multiple pumper trucks. This would be indicative of a surcharge event because if it simply was an explosion in the wet well, there would likely only be one pumping truck needed to clear the wet well. So we may not have had an explosion after all, but rather surcharging of that part of the system. This may be indicative of them getting ready to send dewatering effluent to the plant and they may be seeing just where they can shut things down to gain hydraulic capacity for this dewatering operation.

One additional thought pertains to sending the dewatering effluent to the plant and lays out like this. [The city has] dug a great hole on San Marco across from Walgreens. This is no doubt to tap into the force main that runs from that location either directly to the plant or to cascading lift stations further down the line. That is a great distance from there to the plant and it could conceivably take a day or two for the dewatering effluent to arrive at the influent structure. If after three or four hours of this chemically different influent starts mixing into the primary basins it starts to adversely affect the biomass at the plant, they cannot simply shut it off. Even if they react immediately to stop putting the effluent into the system, there is still as days worth or more in the pipe and that will just keep coming.

This is the risk they run by doing this, and as pointed out in the open letter [by Butch Neylon] to Rony Joel.