Revised On: April 24, 2024 - 11:00 a.m.

EPA #: AZD009004177

Superfund National Priority List (NPL) Status: The EPA listed this site on Oct. 4, 1989

Location

The Motorola 52nd Street Superfund Site (the site) is located in Phoenix, Arizona within the general boundaries of 52nd Street on the east, Palm Lane on the north, Seventh Avenue on the west and Buckeye Road on the south. Due to its size and to better manage cleanup efforts, the site was divided into three areas called Operable Units (OUs). The operable units, from east to west, include OU1, OU2 and OU3.

The site consists of a large area of contaminated groundwater extending from the former Motorola facility at 52nd Street and other sources west of 52nd Street, including Honeywell, the former Joray Corporation, and Arizona Public Service. ADEQ, working in concert with the U.S. Environmental Protection Agency (EPA), is the lead agency for activities in OU1 and OU2 with the exception of the vapor intrusion/indoor air investigation. The EPA is the lead agency at OU3, and EPA has concluded a vapor intrusion/indoor air investigation at the western portion of OU3.

Contaminants of Concern

Volatile Organic Compounds (VOCs), including trichloroethene (TCE), 1,1,1-trichloroethane (1,1,1-TCA) and tetrachloroethene (PCE), are the main contaminants of concern (COCs) for the site. Additional COCs may be identified in one or more of the remedial investigation/feasibility studies (RI/FS) currently in progress.

Public Health Information

There are currently no known exposures to COCs in excess of applicable health-based screening levels at the site. This includes studies conducted to date for groundwater, soil (surface and subsurface) and soil vapor intrusion.

In Phoenix drinking water is provided primarily through surface water sources, with only limited groundwater use from areas located outside the Motorola 52nd Street Superfund site.  However, interim remedial measures are in place at OU1 and OU2 to clean up groundwater and reduce migration of COCs. Remedial activities include operation of two groundwater extraction and treatment systems (GETS): one located at the former Motorola facility (OU1) and the other located at N. 20th Street and E. Washington Street (OU2). These remedial systems are designed to mitigate the risk of exposure to the COCs through groundwater.

The EPA has also been studying the possibility that soil vapor from contaminated groundwater has migrated into buildings and has impacted indoor air. VOCs are able to easily transfer from liquid to vapor phase. TCE and PCE vapor can travel up and into surface structures, such as residential homes and commercial buildings. This exposure scenario, known as vapor intrusion (VI), is currently being studied as a part of the RI/FS process within OU1, OU2 and OU3. Based on the detection of elevated TCE concentrations in soil vapor, vapor mitigation systems were installed at specific locations to reduce exposure risk.

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, some is discharged into the sanitary sewer system and some is recharged into the aquifer.

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 interim remedial systems 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 have removed and treated over 4.29 billion gallons of COC impacted groundwater and nearly 28,336 pounds of TCE. At OU2, groundwater remedial actions have removed and treated nearly 18.6 billion gallons of COC impacted groundwater and 16,011 pounds of VOCs. The 2021 EPA (five-year) review of the interim remedies indicated the need to address several outstanding issues in order to define a final remedy. These issues included: completion of the RI/FS at OU1 and OU2, an ongoing source of contamination at OU1 (the dense non-aqueous phase liquid [DNAPL] that resides in bedrock fissures), and evaluation of the potential vapor intrusion pathway within 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 pathways 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. NXP installed seven additional soil vapor monitoring wells in December 2015 and completed the OU1-wide vapor intrusion report in November 2017.

In 2017, as part of the feasibility study, NXP implemented the Focused 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. As of 2021, results of this field scale pilot program indicated that the biological conditions needed to promote bio-enhanced attenuation of TCE is not sustainable on a long-term basis nor feasible for widespread implementation, as documented in the “Draft Focused Mass Reduction Field Scale Pilot Project Summary Report”, dated Nov. 18, 2021, CTS# 419296.

Status

OU1

Currently, OU1 is operating under an interim remedy that includes two sets of groundwater extraction wells to contain and control COCs. Activities to complete the remedial investigation portion of the project are ongoing. In early 2021, NXP installed four new groundwater monitoring wells northwest of the former Motorola facility to further characterize the source of TCE. In April 2022, NXP submitted a workplan to remove and replace remedial wells at a secondary source area. This work is expected to begin in late 2022. The remedial investigation report is anticipated to be issued in 2023.

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. The final remedy is pending completion of the RI/FS. In late 2019, a work plan to enhance the groundwater extraction system was approved, and implemented in late 2020. The enhancement to the remedy included the installation of two injection wells, which began operation in October 2021. Remedial investigation activities continue with indoor air sampling and monitoring for vapor intrusion, which is planned for completion in 2023.

Remedy evaluation continues for the Honeywell 34th Street site. An integrated focused human health risk assessment was submitted in November 2018 and is near completion. The annual groundwater monitoring report, submitted in July 2022, indicated continued detection of TCE in groundwater above the action level. An FS to assess remedial options is planned for completion in early 2023.

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 testing performed in 2018 indicated significant concentrations of PCE accumulating in subsurface soil. As a result, the SVE system operates in a cyclical fashion to improve efficiency and cost effectiveness. Investigation of the soil vapor plume and the possible presence of DNAPL in bedrock began in 2019 and was completed in 2021. A workplan to perform additional soil sampling to define the extent of hexavalent Chromium (Cr[vi]) is planned for implementation in September 2022.

OU3

Groundwater monitoring continues at OU3 on an annual basis. The OU3 responsible parties completed an initial draft of the groundwater baseline risk assessment in September 2018 and a final version was submitted in June 2022. In 2022 EPA completed their soil gas investigation at the western edge of the OU3 area. The OU3 responsible parties are also in the process of revising the FS report.

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