EPA Superfund Site

MOTOROLA, INC. (52ND STREET PLANT)

AZ | EPA ID AZD009004177

About this site’s exposure pathways: As of January 2025, there is insufficient data to determine the site-wide Human Exposure Control status at Motorola 52nd Street Superfund Site. Groundwater is contaminated with volatile organic contaminants (VOCs) that enter into some residential and commercial buildings, referred to as vapor intrusion (VI). The indoor air has been sampled in several of these buildings to determine if there is VI occurring and if VOCs are at concentrations unsafe for workers and residents. If so, a VI mitigation system has been installed. Not all buildings that could have VI have been sampled yet, so there is insufficient data to determine if VOCs in those buildings are above acceptable human health exposure limits. The completion of indoor air sampling will enable EPA to make a Human Exposure determination for the Site and to ensure that appropriate actions are taken to control exposures, if necessary. It should be noted that EPA cannot determine whether human exposures are under control for properties where owners and/or occupants have not allowed EPA access for sampling purposes.
Building occupants living within the Site who are concerned that vapors from the Site may be intruding into their building should contact the EPA remedial project manager or community involvement coordinator. For more information please visit https://www.epa.gov/vaporintrusion.
There are 3 Operable Units (OUs) at the site. ADEQ is the lead regulatory agency for OU1 and OU2 groundwater, and EPA is the lead for VI. EPA is also the lead for both groundwater and VI for OU3. Specific information about the VI investigations at each OU is below.
OU1: The off-site/residential area VI investigation began in 2010 and was completed in 2018. Some property owners declined providing access for VI investigation so ownership records for the area are monitored; as new owners purchase properties that have not been investigated, attempts to access the property are renewed. Additionally, re-investigation of some properties may be warranted with changing groundwater conditions. As of December 2024, seventeen sub-slab mitigation systems (mitigating 19 homes – one is a multi-unit dwelling) have been installed at residences throughout the area and are regularly monitored. A sub-slab mitigation system was also installed at a commercial building owned by the Arizona Department of Transportation in Fall of 2017. The Former Motorola 52nd Street Plant Campus (on-site) investigation began in 2015 and was completed in 2017. Multiple rounds of soil gas and indoor air sampling were conducted at the buildings throughout the complex. VI was not found to be occurring throughout the complex. New construction on the Former Motorola Plant Campus is being designed to prevent future VI as a precaution.
OU2: The VI investigation began in 2017 and is ongoing. Where soil gas data indicated a potential for VI above SGHHSLs, indoor air sampling was conducted. Multiple indoor air and fifteen soil gas sampling events have been completed, including additional step-out sample areas that were needed to bound the soil vapor concentrations to concentrations lower than the SGHHSLs. Vapor intrusion is not occurring in the buildings sampled. Investigation of commercial buildings remains to be completed in one portion of OU2 and will be conducted in 2025. Additional indoor air sampling is needed where access was difficult to obtain during the Covid-19 pandemic.
OU3: EPA conducted limited VI sampling at locations in OU3 in 2014. Based on this data, a small TCE soil gas plume exists in OU3. Confirmation soil gas sampling was conducted in 2020 to determine if potential VI exists for nearby commercial buildings. The results indicated indoor air sampling was needed in two buildings where they were above SGHHLS, including a residential hotel. The 2021 and 2022 results indicate VI is not occurring in OU3. No further sampling is planned, unless there is a change in site conditions that would warrant additional sampling.