Superfund Site | Motorola 52nd Street: Page 2 of 2

Environmental Considerations: Within the site, there are no unique wildlife habitats or threatened or endangered species. Native vegetation is sparse, as the site is located entirely within urbanized areas of Phoenix. As such, there are no known elevated risks to the environment from COCs or from the mentioned interim remedial activities being conducted at OU1 and OU2.

The extracted groundwater, impacted with COCs, is being treated to the EPA drinking water standards or less. Most of the treated groundwater is beneficially reused and future plans are to have all of the treated groundwater beneficially reused.

Action Taken: Responsible parties have operated various soil vapor and interim groundwater treatment systems since the early 1990s that have reduced the extent of contamination. Vapor intrusion mitigation has been installed at 15 residences. The responsible parties, EPA, and ADEQ are in the process of gathering information from across the site to identify any new COCs and to develop final cleanup actions. This process will be completed over the next few years.

The OU1 and OU2 GETS have been effective in reducing the extent and concentration of COCs in groundwater across a large portion of the site. To date, the groundwater remedial actions at OU1 has removed and treated over four billion gallons of COC impacted groundwater and over 26,000 pounds of TCE. At OU2, groundwater remedial actions have removed and treated over 16 billion gallons of COC impacted groundwater and over 15,000 pounds of VOCs. In 2016, review of the interim remedies indicated the need to address several outstanding issues in order to define a final remedy. These issues included an ongoing source of contamination — dense non-aqueous phase liquid (DNAPL) that has seeped into bedrock fissures — and completing evaluation of the potential vapor intrusion pathway within OU1 and OU2.

In 2011, the EPA entered into an agreement with NXP USA, Inc. (NXP) (formerly Freescale Semiconductor Inc., an independent company that spun off from Motorola in 2004) to investigate the soil gas (vapor) to indoor air pathway within OU1. From 2011 to 2014, soil gas samples were collected and analyzed for TCE and PCE. Due to TCE concentrations in soil vapor above health-based screening levels, the EPA followed up with sub-slab and indoor air sampling at homes, apartment buildings, and commercial buildings within identified areas. Under EPA oversight, NXP sampled 115 residences, four schools and seven commercial buildings. NXP installed sub-slab depressurization systems at 15 residences and successfully reduced TCE concentrations to below two micrograms per cubic meter (µg/m3) in those homes/buildings. Although four locations refused mitigation, all remaining residences now have levels below current health-based screening levels.

In 2017, as part of the feasibility study, NXP implemented the Focused (TCE) Mass Reduction Field Scale Pilot Project at OU1. This pilot program included installation of test wells and the application of a mixture of agents to promote and enhance bio-degradation of TCE in groundwater.

Status:

OU1
Currently, OU1 is operating under an interim groundwater remediation system to contain and control COCs. NXP installed seven additional soil vapor monitoring wells in December 2015 and is in the process of drafting the OU1-wide vapor intrusion report and completing the remedial investigation. A draft Remedial Investigation report is anticipated to be issued in 2019.

NXP also began implementation of the TCE mass reduction pilot project work plan in the Almeria neighborhood. The purpose of this pilot project is to determine the effectiveness of treating TCE and other COCs in groundwater using a chemical specific bio-agent and other bio-enhancing applications. To date, results have been positive and monitoring continues.

OU2
Currently, OU2 is continuing to operate the 20th Street groundwater extraction and treatment system and monitoring the COC groundwater plume. An administrative order of consent (AOC) was signed to complete the RI/FS for the final remedy. Soil gas monitoring for vapor intrusion began in March 2017 and continues in 2019.

Remedy evaluation continues for the Honeywell 34th Street site. An integrated focused human health risk assessment was submitted in November 2018. The annual groundwater monitoring report, submitted in April 2018, indicated continued detection of TCE in groundwater above the action level.

The former Joray Corporation (Kachina) facility, located at 30th Street and E. Washington Street, continues to operate a soil vapor extraction (SVE) system that began in March 2013 to remove residual VOC concentrations (primarily PCE).  The soil vapor rebound test performed in 2018 indicated significant concentrations of PCE accumulating in subsurface soil. As a result, the SVE system will be operated through 2019 in a cyclical fashion to improve efficiency and cost effectiveness. A work plan to further investigate the soil vapor plume and the possible presence of DNAPL in bedrock will be implemented in 2019.

OU3
Groundwater monitoring continues at OU3 on an annual basis. The OU3 Working Group completed a groundwater baseline risk assessment in September 2018 and is in the process of revising the FS report.

Learn more about this Superfund site on the EPA website | View Site >