Mowing "Near-Miss" near FDR Memorial - Provided by: NAMA


At approximately 10:45 am, 31 March 2016, a National Mall and Memorial Parks employee was mowing on West Basin Drive, near the FDR Memorial, in an area with multiple ball fields. He put up warning signs to let cars and pedestrians know that mowing was in progress in that area. The field had been mowed numerous times before.

While the employee mowed, the blade of the mower caught a screw head attached to a plate in the ground that was covering a water pipe. The screw and plate were thrown through the back passenger side window of a passing car. A visitor alerted the mower operator about what had happened. He ceased work and contacted his supervisors and U.S. Park Police.

One passenger in the car that was hit received a cut on her arm due to flying glass. No one else was hurt.

There had been no prior occurrence of mower blades hitting metal in the incident area. This is the only known incident of a metal plate being thrown in the park. The blades were adjusted to the normal cutting height, but on this occasion, the blade of the mower caught the screw and launched the plate. The plate sat at ground level with the screw tip just above it. Under normal circumstances the screw would have just damaged the mower blades, but the threads of the plate were actually stripped, allowing the plate to detach from its anchor. The employee performed the job as he normally would.


  • The park had completed a Job Safety and Health Analysis (JSHA) for mowing operations and the employye was working in accordance with the written guidance.
  • The employee immediately called for assistance and moved the vehicle to a safe location off the road – minimizing damage to the vehicle, protecting the employees, and minimizing the roadway hazard for other employees and visitors


  • The park is now conducting physical inspections of all visible lids around the ball fields of the FDR Memorial to see if there are any additional plates that are not anchored/secured fully.

  • Mower operators will check for this type of water pipe plate with screw on their grounds, and ensure the plates are secure prior to mowing to further prevent and/or reduce the likelihood re-occurrence.
  • If this type of water pipe plate or similar object is set above ground level or not level, operators should use a trimmer to remove the grass from around around the plates as a precaution.


  • Other parks should check for this type of water pipe plate with screw on their grounds, and ensure the plates are secured.
  • Chain guards on the front and rear of the mower (see below) can reduce the thrown objects hazard even more, but not totally eliminate the hazard. Chain guards will typically reduce the number of thrown objects by half and significantly reduce the velocity of those that are thrown.
  • Other shielding such as rubber belting or metal bands can be used to help reduce the thrown objects hazard as well.