TOSHA, with the help of a federal OSHA engineer, last year faulted a construction deficiency for the wall collapse that killed workers John Eslinger, 53, and Don Storey, 44, who were in a flow control building next to the equalization basin when it collapsed.

However, TOSHA did not find any workplace safety violations in that incident.

The city hired Construction Engineering Consultants of Knoxville to investigate the plant but no report has been issued.

Veolia Water North America of Chicago has managed the plant for the city since 1994.

The plant is designed and permitted for an average flow of 3 mgd, according to Matt Demo, Veolia spokesman. The actual daily flow is an average 2.3 mgd.

The plant returned to partial treatment the day after the basin wall collapse and has been operating with a temporary system since then. Neither the city nor Veolia was cited by the Tennessee Dept. of Environment and Conservation or the U.S. Environmental Protection Agency in that incident.

This file was updated on Feb. 29, 2012.