The Town of Miami has a new and much improved public works yard now that APS has finished the excavation of the old Miami Manufactured Gas Plant.
The gas plant was in operation around the turn of the century and there weren’t any environmental regulations in place at that time.
The town of Miami owned the site and operated the MPG beginning around 1923. The plant was sold to Arizona Edison Company, and APS predecessor company between 1926-1930. The synthetic gas was manufactured until 1939-1940 when the facility was converted to natural gas. The facility was taken out of service in 1942 but still used the gas holder to store natural gas until 1950.
MPG operations consisted of a generator house, above ground oil and water tanks, a gas holder, two purifiers and two scrubbers. Six high pressure gas tanks were added for storage of natural gas. The town bought the site from APS around 1972.
APS located eight MPGs that were operated by their predecessor companies. The residues found at the MPG sites are composed of many chemicals and might present health or environmental concerns if direct and substantial contact were to occur.
The soil remediation project was conducted under the Arizona Department of Environmental Quality (ADEQ) and Voluntary Remediation Program (VRP).
APS surveyed sites in Arizona to prioritize each one to make sure there weren’t any surface exposures. The investigation for the Miami site began in 1997, and no exposure was found so it was ranked below the ones that did have exposure. In 2016, APS started planning with ADEQ to clean up the site. The only way to remove the material is to excavate it and the depth of the material varied from two feet to 20 feet over the site. Air quality monitor stations were run 24 hours to make sure there were no issues and a misting system to capture any dust particles was in place as well. APS has a zero-dust policy when excavating. Soil samples were taken from the site and had to come back clean before backfilling could begin. APS crews removed around 10,000 tons of special waste soil and transported it to a landfill with the appropriate permitting. The site was restored to how it was before, which included two carports that had to be removed during the process, a new cast iron water line was also relocated on the south end of the site connecting the mail supply line with a tank that serves the community, concrete bays, fencing and two tuff sheds.
The carports were based on a design from a student at the Talliesin project.
APS Project coordinator Judy Heywood with the APS Enviromental Department stated that “the town of Miami was fantastic to work with, because they didn’t ask us to come in here and make your yard smaller and smaller each week and to park your vehicles elsewhere. It was a great partnership.”
There were delays during the project due to weather and road construction. Another delay was found once they started digging, a sludge basin that was from the original sewage treatment plant. All the costs associated with the remediation, replacement of carports, and water line improvements were covered by APS.