Collapsed Towers Evaluation / Investigation Final Report

The towers were part of the 220 kV Double Circuit Double Conductor transmission line from Pul-e-Khumri to Naibabad and the 220 kV Double Circuit Single Conductor line from Pul-e-Khumri to Kunduz. The investigation was based on limited information supplied by Da Afghanistan Breshna Sherkat (DABS), including photographs of some of the towers, samples of steel members from two of the towers, weather data, seismic event data, and tower locations. The investigation was hampered by the lack of information, including the failure to obtain original construction drawings and specifications from DABS. The investigation found that Tower No. 494, a 220 kV Double Circuit Double Conductor tower on the Naibabad to Pul-e-Khumri line, showed evidence of sabotage, with a torch cut through the angle iron leg near the concrete foundation. The failure mode of Tower No. 489, another 220 kV Double Circuit Double Conductor tower on the same line, is unknown due to the lack of photographs. In contrast, the investigation found clear evidence of an explosive charge causing the failure of Tower No. 544, a 220 kV Double Circuit Single Conductor tower on the Kunduz to Pul-e-Khumri line. Samples of tower steel were collected and tested for yield strength, ultimate strength, and elongation. The investigation also found that Tower No. 500, a 220 kV Double Circuit Single Conductor tower on the same line, failed due to a structural failure, with photographs showing the tower folded over with the conductors on top. The investigation was unable to determine the cause of failure of Tower No. 486, another 220 kV Double Circuit Single Conductor tower on the Kunduz to Pul-e-Khumri line, due to the lack of photographs. The investigation concluded that the failure of the towers was not caused by an explosive ordinance, but rather by a combination of factors, including sabotage and structural failure. The investigation recommended that DABS conduct a thorough investigation into the cause of the tower failures and take steps to prevent similar incidents in the future. The investigation also recommended that DABS provide additional information to the Afghanistan Engineering Support Program to facilitate a more comprehensive investigation. The investigation was conducted by Tetra Tech, Inc. under the Afghanistan Engineering Support Program, with funding from the United States Agency for International Development (USAID). The investigation was completed on June 6, 2016.