From the OIG (PDF)

This management alert presents a safety concern at a U.S. Postal Service Facility in Pontiac, MI (Project Number 16RG002HR001). This issue came to our attention during our review of safety concerns at the facility (16RG002HR000).

Introduction
This management alert presents a safety concern of the methane detection system observed at the U.S. Postal Service Michigan Metroplex Processing and Distribution Center (Metroplex), located in Pontiac, MI (Project Number 16RG002HR001). This review was initiated based on safety concerns expressed to us in a complaint which identified five employee deaths during a 14 month period (16RG002HR000). We have not correlated these deaths to the safety concern at this time, but are continuing work in this area. However, we are reporting this issue with the methane detection system for your immediate action.

The Metroplex is built on a site previously used as a vehicle manufacturing plant that included a foundry.1 This site is considered a brownfield. Brownfields are former industrial or commercial sites where future use is affected by environmental contamination. Brownfield sites are converted into usable space under the supervision of the U.S. Environmental Protection Agency (EPA). The EPA has specific guidelines and regulations that must be followed to properly assess, safely clean up, and sustainably reuse brownfields.

Before the Metroplex site was developed into useable space, the landowner commissioned environmental studies to determine which contaminants were present and what remediation was necessary to remove or contain such contaminates. Light non-aqueous phase liquid (LNAPL)2 was one contaminate found in multiple underground locations throughout the site. As part of the decomposition process organisms underground break down LNAPL and produce colorless and odorless methane gas.

When the Postal Service built the Metroplex, a gas venting system was installed under the foundation and inside the building. The purpose of the venting system is to prevent the buildup and accumulation of methane gas underneath the building by actively capturing the gas and venting it away from the building. Additionally, a methane detection system (MDS) was installed with sensors strategically placed in various enclosed spaces within the facility. The MDS was designed to detect and alert personnel of any seepage and accumulation of methane gas inside the facility.

Methane gas is extremely flammable and may form explosive mixtures with air when levels reach certain concentrations known as “lower explosive levels” (LEL). Control of the explosion hazard is achieved by ventilation. In the case of the Metroplex, ventilation occurs through the gas ventilation system, which is built under the foundation and into the structure of the building. The LEL is also used as a percentage reading on the main control panel of the MDS. The system was designed and calibrated to detect and measure methane gas and shows the relative concentration of the atmosphere to the LEL. An LEL reading of 100 percent on the main control panel would indicate the concentration of the methane gas is combustible.

1 A foundry is defined as a workshop or factory casting metal. 2 LNAPL is a groundwater contaminate made up of a group of organic substances that are relatively insoluble in water and are less dense than water. LNAPLs tend to spread across the surface of the water table.

The detection system was built with a color coded light indicator warning system:

• Red: Danger – methane detected at 20 percent LEL.
• Amber: Warning – methane detected at 10 percent LEL.
• Blue: Malfunction – a detector sensor malfunction occurred.

The initial warning level for the detection of methane gas on the MDS is set at 10 percent LEL. When a sensor in the system detects methane gas at a range of 10 to 19 percent LEL the amber light on the main control panel is illuminated. The light will remain illuminated until the level drops below the 10 percent LEL warning level and the MDS is manually reset. The higher danger level for detection of methane gas on the MDS is set at 20 percent LEL. When methane is detected at 20 percent LEL or higher, the red light on the main control panel is illuminated until the level falls below the threshold and the system is manually reset.

The Postal Service took over maintenance of the MDS in October 2014 from the vendor that installed the system. The three Postal Service building equipment mechanics authorized to perform maintenance on the MDS received training from the vendor. If the system fails or needs repair that Postal Service personnel cannot resolve, the mechanics are required to contact the vendor.

Summary
Based on our observations and review of the system log book, 3 the MDS at the Metroplex has not been functioning properly since March 2015. Maintenance personnel repeatedly replaced the sensors and stated the continuous flashing amber warning light, which detects methane at 10 percent LEL, was due to sensor malfunction and not the buildup of methane gas. However, if the system was operating as designed, the blue indicator light, which is designed to flash when there is a sensor malfunction, would have been illuminated during our observation. Additionally, the amber light flashed when the screen on the main control panel showed 0 percent LEL, which further indicates that the full system may not be functioning properly.

According to the vendor hired to perform system maintenance and recalibrate the MDS and its components, he has repeatedly recommended the Postal Service resolve his claims of methane buildup. Specifically, the vendor recommended the Postal Service modify the system to include a ventilation of the pipes that release the methane gas into the atmosphere. On January 15, 2016, management stated they have taken action by issuing an emergency contract for an industrial hygienist to evaluate the methane levels at the facility. According to a report detailing the results of the evaluation, the methane level was low and there is no immediate health or safety concerns identified with regard to the methane levels in the facility.

3 A MDS log book is maintained to record maintenance of the system and record incidents when there is a change in status of the detection system

Postal Service managers are required to demonstrate a commitment to providing safe and healthy working conditions. If methane builds up in enclosed spaces, the health and safety of employees may be at risk and could result in medical complications. Unmitigated accumulations of methane gas may increase risks to the health and safety of employees and could lower productivity and employee morale.

READ ENTIRE REPORT (PDF)