1/25/17 USPS OIG: Environmental Conditions at Michigan Metroplex Processing and Distribution Center Management Advisory Report
This report presents the results of our follow-up to the management alert issued February 22, 2016, regarding the malfunction of the methane detection system observed at the U.S. Postal Service Michigan Metroplex (Metroplex) Processing and Distribution Center in Pontiac, MI.
Five postal employees deaths at Michigan facility prompts safety concerns of methane detection system
The Metroplex, established in 2008, is built on privately owned property that formerly contained a foundry, manufacturing operations, and hazardous materials storage and handling areas, which left residual contamination in the soil and groundwater at the site. The landowner tested the land (i.e., surface soils, subsurface soils, and groundwater) to determine the location and nature of the contaminants and initiated clean-up in preparation for building the facility. It is the landowner’s responsibility to continue annual groundwater testing of the land.
Studies commissioned by the landowner found methane generated through the decomposition of organic materials underground.When the Postal Service built the Metroplex, management installed a vapor extraction system to prevent methane from infiltrating the building and a methane detection system to detect methane and alert personnel of any seepage and accumulation of the gas inside the facility.
Concerns about the safety conditions at the facility arose in August 2015, with an initial APWU complaint. The concerns were bolstered in December 2015, by claims from a Postal Service contractor concerned about the safety and health of employees at the facility. Postal Service management requested that OSHA and three contractors test the methane levels and assess the methane venting and detection systems and their effectiveness.
In our management alert, we recommended management complete a review of the methane detection system to resolve any issues and establish an ongoing process to independently validate the results of the system on a periodic basis. Subsequently, the OIG contracted and worked with an environmental and technical services company, to assess the methane venting and detection systems, environmental concerns and management’s corrective actions.
What the OIG Found
The Occupational Safety and Health Administration and three contractors found that methane concentrations within the facility did not exceed methane exposure limits, and that other hazardous air pollutants detected within the facility were below permissible levels. Consequently, the facility was considered safe relative to methane exposure.
Management installed stand-alone secondary equipment to test for methane and took corrective actions to adjust sensors on the methane detection system that did not correctly detect known levels of methane by reprogramming, recalibrating, and properly mounting the sensors. Also, to improve performance and monitoring of the methane detection system, management installed a more detailed display panel, new wiring in select locations, and a computer to log historical readings from the sensors.
Following completion of our fieldwork (October 2016), the Postal Service commissioned an additional evaluation of the existing methane mitigation system relative to environmental requirements, system data collected from the time installed until the present, and changes in technology since installation.
The results of the additional testing (November 2016) disclosed methane levels of the building subslab sampled from two vent pipe locations (D1 and D2) exceeded the concentrations considered when the building was designed.
In subsequent discussions, Postal Service officials stated they would initiate modifications to the current methane detection system by making the subslab venting “active” on vent stacks D1 and D2, which are located in the quadrants of the building over the existing underground contamination. Management stated that vent stacks D3 and D4 will not be made active as there have been no readings indicating it is warranted in those areas. Their consultant’s November 2016 report indicated additional sampling of subslab vapors analyzed for speciated volatile organic compounds (VOC) did not identify benzene or other VOCs that exceeded the current screening levels.
An active system should include fans or vacuum blowers within the vertical pipes to remove potentially contaminated air through the pipes to vents above the exterior roof line of the building. This should mitigate the risks of vapor intrusion of methane and VOCs due to collection pipe spacing and increased pressure differentials. An active system also eliminates the need to look for potential cracks, openings, and pathways that could be sources of vapor intrusion in the event the pressure differential exceeds a set threshold.
While noting these corrective actions listed above, we identified the following issues:
- Management did not calibrate or check the methane detection system’s sensors with specific levels of methane calibration gas for 8 months, when the manufacturer recommended it do so every 6 months. Management is contracting with a vendor to perform periodic maintenance on the methane detection system.
- Officials were not sufficiently trained to perform their responsibilities with the system. Further, management did not update the methane venting and detection systems operating manual when system components were modified.
- The VOC benzene was found in the soil gas samples adjacent to the building. However, as noted in our report, the most recent testing disclosed that benzene was not detected in the samples collected and none of the detected VOCs exceeded the current screening levels. In addition, given the conversion from passive to active at the two vent stack locations noted, no further action is needed at this time. It is important to note though, that if the methane detection system is changed in the future from active to passive, additional testing would be needed to ensure that no methane, benzene or other VOCs are present above screening levels at the time of conversion.
- Four sensors in the ventilation pipes that monitor and detect pressure differences between the subslab and indoor air did not have alert notifications for increases in relative pressure differences due to weather changes and events that may cause vapor intrusion into the facility. We observed excessive differential pressure levels during our site visits and no alarms or alerts were triggered. In their response to this report, management provided documentation to show the system was set for notification if the building experiences negative pressure for 5 consecutive minutes. Further, no action is needed once the system is converted from passive to active, as an active system will mitigate the pressure in the pipes.
- Spacing between the collection pipes is greater than 50 feet and may not effectively collect and passively vent accumulated gases from beneath the building. However, given the Postal Service’s plans to convert the methane detection system from passive to active at the two vent stack locations, no further action is needed regarding this issue.
Periodic maintenance, adequate training, and an updated operating manual would allow officials to verify the methane venting and detection systems are operating as designed and prepare them to identify and resolve potential issues. These actions could also enhance employee confidence in the Postal Service, increase productivity, and boost morale.
Additional Conditions Impacting the Metroplex
While noting these corrective actions listed above, we identified the following issues:
Methane Sensor Calibration
Management did not regularly calibrate or check the methane detection system’s sensors with specific levels of methane calibration gas. The sensors were not calibrated for about 8 months – between September 14, 2015 and May 5, 2016.
According to the manufacturer, the sensors do not need to be calibrated on an ongoing schedule. However, the manufacturer recommends, as a precaution and to ensure the sensor is functioning correctly, that the sensors be checked for a response to specific levels of calibrated methane gas every 6 months. Management stated that they are actively pursuing a vendor to perform
maintenance on the methane detection system, which would include periodic sensor calibration.
Had adequate maintenance and monitoring been performed on a periodic basis the issues identified with the methane detection system may have been found and remedied sooner.
Employee Training and Operations, Maintenance and Monitoring Manual
The Postal Service did not adequately train supervisors and personnel performing maintenance on the methane detection system. According to a review of training records, no employees were trained to operate and maintain the methane detection system. Management stated maintenance personnel received training in October 2014 from a contractor when they took over the responsibility of maintaining the methane detection system, but did not have supporting documentation showing this training occurred.
From June 2 through 3, 2016, management provided training to select managers and supervisors on the methane detection system’s new display panel to make them aware of the features of the system and how it operates. However, the training occurred before the Operations, Maintenance and Monitoring Manual was completed. Management stated the Operations, Maintenance
and Monitoring Manual was being updated and would be completed mid-September, and key personnel would receive additional training on the methane detection system
What the OIG Recommended
We recommended management finalize conversion of the methane venting system from passive to active, develop a process to check the sensor calibration, provide training on the methane detection system to responsible personnel, and update the operating manual.