MLGW estimates costs, risks from ruined substation

Memphis Light Gas and Water is an estimated five months away from completely restoring the substation destroyed in a July 11 explosion.

The catastrophic failure at Substation 68 destroyed the breaker, one transformer and the control house, leaving most of Lakeland and Arlington and part of Bartlett temporarily without power.

MLGW CEO Jerry Collins told the Arlington town board on Aug. 1 that the cause remains unknown and any evidence was destroyed in the explosion and fire.

In the latest update from MLGW, the utility company responded to community rumors about deliberate sabotage.

“MLGW has not ruled out any potential cause at this time, but has no evidence to suggest that,” the statement noted.

Utility company answers questions

MLGW responded to key concerns more recently:

Not-so-toxic emissions: The explosion ignited and distributed the mineral oil that insulated the transformer. Residential neighbors worried this was a hazard and questioned whether the substation used mineral oil that contained polychlorinated biphenyls (PCBs).

MLGW’s response: Substation 68’s transformer used modern non-PCB-containing mineral oil known as HyVolt II. Combusting it typically produces emissions that are not of toxicological interest in a short-term outdoor, open exposure condition like the July 11 explosion. The open-air setting and local meteorology at the time “does not translate to a health concern for nearby residents.”

Mineral oil residue: Is any mineral oil residue at the substation hazardous?

MLGW’s response: “Most of the released oil was consumed by the fire, and some slightly darker areas of oil can be seen remaining on the crushed rock which serves as base material on the ground in the areas where substation equipment is located. The remaining oil does not represent a residual hazard, but will be removed and replaced in the process of repairing and restoring the substation site.”

Contamination: How far did any mineral oil contamination reach?

MLGW’s response: “Most of the oil was released in the immediate vicinity of the damaged transformer. The oil was contained within the area of crushed rock which serves as base material on the ground of the substation. Direct site inspection indicates that the released oil only went approximately 100 feet in a westward direction. That is less than half the distance from the transformer location to the fence separating the substation site from the homes. No vegetation damage or other evidence of oil was observed on the MLGW side of the fence.”

The sulfur compound: Citizens asked about the substance described as a “sulfur compound” that was found around the large circuit breaker (and neutralized in the immediate aftermath).

MLGW’s response: Sulfur hexafluorine (SF6) is a gas used as an insulating substance in the large circuit breaker. The substance found around the breaker was a component of that. SF6 isn’t flammable, is essentially nontoxic and dissipates rapidly in the air.MLGW crews mixed baking soda with water and sprayed it on or near the circuit breaker to neutralize any SF6 byproducts. The MLGW response noted, “That would not be expected to exhibit residual toxicity.”

Cost: What’s the repairs estimate, and who pays?

MLGW’s response: “It is early in the process, but MLGW currently estimates that cost of repairs will exceed $5 million. MLGW expects the majority of that cost will be covered by insurance.”