Grand Canyon National Park (GRCA) requires the service of backflow prevention assemblies inspection, testing and maintenance. - per attached scope of work - Utilize blank bid schedule - done as a serv... Grand Canyon National Park (GRCA) requires the service of backflow prevention assemblies inspection, testing and maintenance. - per attached scope of work - Utilize blank bid schedule - done as a service contract location: Throughout GRCA NP. - South Rim (accessible year-round) - North Rim (closed to the public from December 1 to May 15) - Inner Canyon locations (accessible via foot or helicopter)