2025: The former Motorola plant headquarters building is scheduled for demolition and several wells may require abandonment and replacement. Upon demolition, further assessment beneath the former building is planned. In addition, NXP USA, Inc. (NXP) (the current responsible party, formerly Freescale Semiconductor Inc., an independent company that spun off from Motorola in 2004) plans to perform additional soil gas sampling west of North 46th Street.

2024: Site development activities included demolition of several former Motorola plant buildings and ongoing additional assessment within the former building footprints. Groundwater remedial actions at OU1 removed and treated over 95.6 million gallons of contaminant of concern (COC) impacted groundwater and nearly 499 pounds (lbs) of trichloroethene (TCE).

2023: Several extraction and monitoring wells at the facility were abandoned and replaced due to ongoing development. Groundwater remedial actions at OU1 have removed and treated over 4.44 billion gallons of COC impacted groundwater and nearly 29,320 lbs of TCE.

2022: Several additional wells were installed to further define the TCE plume northwest of the former facility.

2021: Results of a field scale pilot program indicated that the biological conditions needed to promote bioenhanced attenuation of TCE are not sustainable on a long-term basis nor feasible for widespread implementation.

2018: Pilot project work continued with TCE mass reduction. Applications of bioenhancing products and a bio-agent were performed through August. Program monitoring continued through the year with additional injections of bioenhancing product in December. Preliminary results showed positive in-situ TCE-degrading bio-activity. 

2017: OU1 sitewide soil gas to indoor air vapor intrusion investigation was completed in November 2017.

In 2017, as part of the Feasibility Study (FS), a Focused Mass Reduction Field Scale Pilot Project was implemented. This pilot program included installation of test wells and the application of a mixture of agents to promote and enhance biodegradation of TCE in groundwater. 

2017: The Focused Mass Reduction Field Scale Pilot Project Work Plan was approved and implemented. Test wells for the TCE mass reduction pilot project were installed in the Almeria neighborhood.

2016: The Focused Mass Reduction Field Scale Pilot Project work plan was prepared. Vapor Intrusion (VI) investigations conducted at the former 90-acre Motorola campus indicated no VI issues. VI investigation of residential areas was completed and mitigation deployed at 15 residences. Eight new groundwater monitor wells were installed to help fill data gaps in the groundwater monitoring network.

The United States. Environmental Protection Agency (EPA) five-year review (FYR) was performed for all the OUs and indicated that the COC groundwater plume within OU1 and OU2 was shrinking in size and concentrations were decreasing. The interim remedy at OU1 was deemed protective of human health in the short term. The protectiveness at OU2 was deferred until completion of the VI investigation.

2015: NXP submitted a Remedial Investigation (RI) Work Plan and seven additional soil vapor monitoring wells were installed in the source areas. In December treated water discharged from the groundwater extraction treatment system was routed to the Old Crosscut Canal for beneficial use.

2014: Freescale Semiconductor, a wholly owned subsidiary of Motorola Inc. (Freescale), which would become NXP, installed several monitor wells to further characterize and delineate the extent of TCE in groundwater. Freescale, with EPA oversight, continued to perform the VI investigation. Indoor air mitigation systems in residential homes continued to be monitored. EPA performed soil gas and indoor air sampling at select locations during February 2014.

2013: Freescale submitted a revised work plan to address data gaps associated with the northern and western boundaries, and within some residential neighborhoods. Freescale continued monitoring and maintenance of the groundwater treatment system, in addition to sample collection of groundwater and soil vapor. Indoor air mitigation systems were installed in several residential homes in the OU1 area.

2012: Freescale submitted a work plan to address data gaps associated with the northern boundary and continued monitoring and maintenance of the groundwater treatment system. Results from soil gas monitoring in the adjacent neighborhoods indicated the need for indoor air sampling.

2011: The FYR was completed in September 2011. The remedy was considered not protective pending VI investigation. EPA continued sampling and investigation regarding VI.

2010: Work continued on the Bedrock Study and End Use Alternatives. Community interviews were held for the FYR and to update the Community Involvement Plan. The connection to the City of Phoenix sanitary sewer was completed in December 2010. EPA began VI investigations.

2009: Freescale began conducting the bedrock extraction pilot test in September and researching alternative end uses for the treated water. ON Semiconductor announced that the manufacturing operations at the 52nd Street Plant would be terminated. The treated water from the OU1 Treatment Plant was used by ON Semiconductor in manufacturing operations. Freescale evaluated alternative end uses for the treated water. Pending a final decision ADEQ and EPA approved discharge to the City of Phoenix sanitary sewer. As of December, the treatment plant treated 1.2 million gallons of groundwater and an estimated 495 lbs of volatile organic compounds (VOCs) were recovered. 

2008: As of January, the OU1 groundwater treatment system (located at 5005 East McDowell Road) treated approximately 2.8 billion gallons of groundwater. In December, Freescale installed one bedrock extraction well and two bedrock monitor wells for a bedrock pilot study to collect additional bedrock permeability information and to evaluate bedrock groundwater extraction and its potential to remove mass and enhance the extent of vertical capture in the bedrock aquifer.

2007: Freescale installed three groundwater monitor wells at the Old Cross Cut Canal to better define the groundwater contamination and to evaluate the effectiveness of the treatment system. A FYR addendum report was issued by ADEQ in October, which provided an update on the action items that were listed in the third FYR report dated September 2006.

2005: In September and December, Freescale submitted a Groundwater Remedial Alternatives Analysis to evaluate other remedial alternatives and potential optimizations to the groundwater treatment system.

2004: In April, Motorola spun off its semiconductor sector into a new company, Freescale Semiconductor, a wholly owned subsidiary of Motorola Inc. Freescale Semiconductor agreed to implement the requirements of the OU1 Consent Decree and the OU2 Unilateral Order.

2003: In April, Motorola shut down the groundwater treatment system upon discovering cracks in the carbon vessels that serve as air emission controls. The OU1 Effectiveness Report was submitted and ADEQ identified three areas of concern:  1) the stagnation area (downgradient of the off-site capture zone); 2) the area to the north around monitor Well EW-18; and 3) the capture of contaminants in bedrock.  In October, Motorola submitted a Letter of Intent to conduct an FS to evaluate other remedial alternatives and/or optimize the current groundwater treatment system.  Since the groundwater treatment system was off for approximately six months until the air emission controls were replaced, ADEQ required Motorola to conduct an evaluation of capture. Motorola determined that during the time the system was off, contaminated groundwater did not migrate past the capture zone.

2002: In response to the FYR, Motorola conducted studies and evaluated the OU1 groundwater treatment remedy in an effort to optimize the system. In November, ADEQ determined that the soil cleanup was complete in the southwest parking lot area (SWPL) area. Another health consultation was completed by the Agency for Toxic Substances and Disease Registry (ATSDR).

2001: In September, ADEQ completed the second FYR of the OU1 remedy.

1996: ATSDR completed an update to the 1988 Health Assessment and the 1993 update to the health consultation. In November, the SWPL soil vapor extraction (SVE) operations began and continued through April 1997. Approximately 170 lbs of VOCs were removed during the system operation in addition to the approximately 269 lbs that had been removed during the pilot Air Sparging (AS)/SVE test in February 1993.

1995: In November, Motorola conducted a soil gas survey consisting of 25 sample locations of the off-site area immediately to the west of the Courtyard and the northern part of the 52nd Street facility. In November, ADEQ completed the first FYR of OU1 which determined that the OU1 was operating effectively and meeting the remedial objectives. 

1993 – 1994: ATSDR completed an update to the 1988 Health Assessment. In February, an AS/SVE pilot program was conducted in two locations within the SWPL area. Approximately 269 lbs of VOCs were removed.  A program was initiated to periodically remove free product solvent from bedrock.

1991 – 1992: The Arizona Department of Health Services (ADHS) completed a Baseline Risk Assessment that concluded:  the risk of public exposure to groundwater is limited, and therefore causes no imminent health hazard.  EPA completed an ecological risk assessment that concluded: because of [the VOC’s] high volatility and low toxicity relative to freshwater aquatic criteria, exposure of biota to acute or chronic levels of 1,1,1-trichloroethane (1,1,1-TCA) and TCE may not be a concern.  Inorganics (arsenic and lead) would be of most concern to biota because of their exceedance of the fresh water criteria, persistence in the environment, and their potential for bioaccumulation.  In May, an SVE system was constructed in the Courtyard and by June was operational. The SVE system was shut down in March 1993.  Approximately 350 lbs of VOCs were removed. In July, the pre-design RI Work Plan was submitted and the full-scale groundwater treatment system was placed in operation. The treatment system is considered an interim remedy and the final remedy will be determined after the final OU1 FS and Record of Decision are completed.  The plant treats groundwater by running it through two air strippers connected in series, and is then run through four liquid phase granular activated carbon (GAC) vessels (two parallel sets of two vessels connected in series) for polishing. The treated water is then used by ON Semiconductor for their facility operations. The air emissions are treated by vapor phase GAC. Approximately 95% of the air is recycled through the air strippers and approximately 5% is treated and then released to the atmosphere.

1990: A sump located within a building near the SWPL was identified as another source of contamination, mainly TCA. Initial soil sample results under the sump were as high as 30,000 parts per billion (ppb) of TCA. In 1990, ADHS completed a health study entitled: Cancer Incidence and Mortality in an East Phoenix Area Overlying Groundwater Contaminated with VOCs. The study found no elevated rates of cancer as compared to the rest of Maricopa County.  

1989: In June, Motorola and ADEQ entered into a Consent Order (CO), lodged with the Arizona Superior Court, requiring Motorola to design and implement an interim groundwater remedy and soil remedies in the OU1 area, and to continue to work on a revised RI/FS Work Plan to define work components leading to a final remedy. The remedial objectives as defined in this CO are to contain and control the migration and level of contaminants in the groundwater through implementation of the work by Motorola. On October 4th, the site was placed on the EPA’s National Priority List (NPL). Although the site was listed on the NPL, EPA delegated its authority to ADEQ to continue to be the lead agency.

1988: A health assessment was completed by the ATSDR that concluded that the site was unlikely to pose any threats to human health. The report also stated that although on-site and off-site groundwater was contaminated, contaminant levels at the point of extraction were below the levels of concern. In June, Motorola submitted a Remedial Action Plan (RAP) to ADEQ that proposed a remedial alternative, and a public meeting was held in July. In September, ADEQ and EPA issued official approval to implement the recommendations in the draft RAP in a Letter of Decision for the OU (later designated as OU1) interim remedy. The OU remedy selected consisted of the following components: 1) on-site extraction and treatment of groundwater from the Courtyard and 50th Street area, 2) on-site extraction and treatment of vapor phase organic contaminants from soils from the Courtyard, the Acid Treatment Plant (ATP), and SWPL areas, 3) off-site extraction of groundwater designed to contain contaminant migration at the Old Crosscut Canal, 4) on-site treatment of groundwater extracted from off-site wells, and 5) use of all treated groundwater at the Motorola 52nd Street facility. The OU interim remedy was designed to provide overall protection of human health and the environment by containing migration of VOCs and to treat the extracted groundwater to a level which will meet State/Federal standards.

1984 – 1987: From October 1984 to June 1987, Motorola completed an RI/FS under the direction of the oversight committee. The RI report summarized the results of source characterization and site investigation. The FS report established remedial objectives, identified alternative approaches, and evaluated alternative remedies. These draft documents were issued for public comment. Twenty- eight potential sources were identified and investigated, such as: past surface discharges, spills, tank and pipe leaks, and discharges to leach fields and drywells. It was determined that the majority of the contamination came from sources in the Courtyard area. A Pilot Treatment Plant was constructed in the Courtyard area which included two extraction wells.

1982 – 1983: Site discovery occurred in November 1982 when Motorola reported that the 5,000-gallon (underground storage tank (UST) located in the Courtyard area had leaked TCA. From January 1983 to December 1983, Motorola conducted a preliminary investigation which included the installation of 29 monitoring wells. A report was submitted to ADEQ in December 1983. Analytical data indicated soil and groundwater contamination on the facility property, and groundwater contamination continuing to the west of the property. The highest concentrations of contaminants were found in the Courtyard area of the facility. TCE concentrations as high as 1,470,000 ppb and TCA concentrations as high as 721,000 ppb were found in bedrock. As a result, Motorola entered into a verbal agreement with ADEQ, EPA, ADHS, Arizona Department of Water Resources , Salt River Project (SRP) and the cities of Phoenix and Scottsdale (the oversight committee) to characterize the nature and extent of contamination and recommend remedial actions.

1974 – 1976: The SWPL area was used extensively as a main staging area of waste chemicals stored in 55-gallon drums that were suspected of leaking.

1963 – 1974: The Courtyard was the site of a 5,000-gallon TCA UST and a drywell that was approximately 3 feet in diameter and 15 feet deep. The drywell received solvents, mainly TCE and TCA, from 1963 to 1974. The solvents were used at the facility to remove greases, waxes, oils, and Photoresist. Soils and groundwater have been impacted with chlorinated solvents in this area. Additionally, free product solvent has been found in the bedrock at the Courtyard. The ATP was built on a buried waste solvent line suspected of leaking and there were reports of solvent spills in the area.

1956 – 1963: The Motorola 52nd Street facility was originally constructed in 1956 and in operation until the third quarter of 1999 when Motorola's Communications, Power and Signal Group was split off to become ON Semiconductor. Motorola remains responsible for the remediation effort related to its former operations at the 52nd Street facility. No municipal sewer was available thereby requiring on-site disposal of domestic and industrial waste in underground tanks, leaching fields, drywells, pits, sumps, and surface disposal areas. The types of wastes that were known to be released to the environment at the facility are: solvents, acids, cyanides and sanitary sewage. Solvents, such as TCE, TCA, freon, and tetrachloroethene, were dispensed to various Motorola operations at the facility.

2025: A work plan to install an additional extraction well south of the existing southern extraction well is in review and additional indoor air sampling is planned in Area 2 of OU2. As part of the Remedial Investigation (RI), work also continues to complete indoor air sampling at select industrial properties.

2024: The preliminary draft of the Soil Gas to Indoor Air Investigation Report was prepared and revisions are in progress. A work plan to perform additional indoor air sampling was approved and planned for implementation in February 2025. Additional soil and groundwater sampling was performed at the former Joray facility as part of RI activities.

2023: Data indicates that through 2023, groundwater remedial actions have removed and treated over 20 billion gallons of contaminant of concern (COC) impacted groundwater and 16,450 lbs of volatile organic compounds (VOCs).

2021: Two injection wells at the OU2 treatment system began operation.

2020: A work plan to enhance the groundwater extraction system was approved and implemented in late 2020.

2019: Groundwater investigation activities began at the former Joray facility.

2018: Vapor intrusion (VI) investigation continued with the 5th round of step-outs to fully define the extent of trichloroethene (TCE) in soil vapor at concentrations greater than the (site specific) Soil Gas Human Health Screening Level of 210 micrograms per cubic meter. An in-situ chemical oxidation pilot program work plan was approved and implemented in May. Approximately 40,000 pounds (lbs) of chemical oxidant was initially injected into four wells and later into six supplemental wells near the center and southern portion of the COC plume at the western end of OU2.

2017: The soil gas to indoor air investigation began at the OU2 area.

2015 – 2017: As part of the RI, the VI investigation began in 2016 and continues to date. Semi-annual groundwater monitoring was performed and the groundwater extraction treatment system continued operation to reduce the COC plume.

2015: An administrative order on consent between the ADEQ and the OU2 companies was signed to complete the RI/Feasibility Study (FS) for the OU2 final remedy. The final remedy is pending completion of the RI/FS.

1999 – 2017: Honeywell completed remedial actions at the Honeywell 34th Street facility (within OU2) for jet fuel releases over the course of approximately 18 years. Honeywell used multiple remedial tools to remove more than 7,500 gallons of free product (via direct recovery) and approximately 17 million lbs of petroleum hydrocarbons from the subsurface between 1999 and 2017 using biologically enhanced soil vapor extraction (BSVE) technology. In addition, the BSVE system removed over 400 lbs of residual chlorinated VOCs from the subsurface in the eastern portion of the facility.

2014: Six new monitoring wells were installed to address data gaps within the COC plume.

2013: Negotiation of the OU2 supplemental RI/FS continued. The RI/FS will aid in determining a proposed plan and final remedy. An evaluation of VI is needed to address this potential pathway. Semi-volatile organic compounds were added to the September sampling rounds for select wells.

2012: ADEQ began negotiating the statement of work and the area of concern for the OU2 site-wide area. The RI/FS will address groundwater monitoring data gaps and investigation of the VI pathway.

2011: A FYR was completed evaluating the Record of Decision and the remedy in place. The hydrostratigraphic nomenclature of Subunits A, B and C was changed to Salt River Gravels and Basin Fill. Groundwater monitoring continued and the treatment system operated without disruption.

2009 – 2010: Motorola and Honeywell (the Companies) negotiated a Consent Decree (CD) with ADEQ for operation of the OU2 treatment system and for ADEQ to take over oversight from U.S. Environmental Protection Agency (EPA). In July 2010, the decree was approved by the Federal District Court in Phoenix. As of the end of September 2010, approximately 12,334 lbs of VOCs had been removed from the subsurface.

2008: As of September 30, the OU2 groundwater treatment system treated over 7.6 billion gallons of groundwater and removed over 10,567 lbs of contamination since the system began operation in December 2001.

2007: The Companies installed four sets of groundwater monitor wells to the south and west of the southernmost groundwater extraction well. Three additional locations were drilled during the month of November to evaluate groundwater elevations, contaminant concentrations, and bedrock.

2006: As of January, the OU2 capture and treatment system treated over 4.5 billion gallons of water and removed over 6,000 lbs of contamination. The second Five Year Review (FYR) was completed in September.

2005: ADEQ issued a Unilateral Administrative Order (UAO) to Joray Corporation to conduct an investigation at its former facility, Kachina Testing Laboratories.

2003: In April, the Companies submitted the Remedial Action Report. The report provided documentation to show that the OU2 groundwater treatment system had attained capture of the contaminant plume.

2002: In November, Motorola submitted an evaluation of groundwater extraction rates by conducting a model. The results of the model indicated that the extraction rates of the OU2 system could be substantially reduced while still maintaining capture of the observed plume. The pumping rate was reduced to 2,650 gallons per minute (gpm).

2000 – 2001: In March 2000, under the oversight of EPA, construction of the treatment system began and was completed in September 2001. The OU2 groundwater treatment system became fully operational, designed to pump at a rate of approximately 5,000 gpm. The treated water was discharged to the Salt River Project (SRP Grand Canal for irrigation use and met all treatment standards.

1999: On December 28, ADEQ approved the final 100% design report. In November, the Companies submitted the OU2 Remedial Action Work Plan to EPA.

1998: In November, EPA issued a UAO to the Companies for construction, start up, and two years of operation and maintenance of the groundwater treatment system. EPA became the lead agency for the remedial action phase for OU2.

1997: ADEQ and EPA determined that the investigation of groundwater contamination from 52nd Street to 7th Avenue would continue under the federal Superfund program. The EPA delegated its authority to ADEQ to continue to be the lead agency for the OU2 area.

1996: The Agency for Toxic Substances and Disease Registry (ATSDR) completed an update to the 1988 Health Assessment and the 1993 update to the Health Assessment. In October, Motorola and the City of Phoenix signed a CD with ADEQ to implement the design of a groundwater containment and treatment system for OU2. Honeywell withdrew from the agreement and did not participate in the design.

1994: In July, ADEQ and EPA issued the ROD selecting the interim groundwater remedy. The purpose of the OU2 interim remedy was to provide additional containment of contaminated portions of the groundwater. The interim remedy included groundwater extraction near 20th and Washington Streets, treatment of the water by ultraviolet oxidation and granular activated carbon, and discharge of the treated water to the Grand Canal for irrigation use.

1993: EPA named the City of Phoenix a potentially responsible party (PRP), as the landowner of a portion of the Honeywell and ITT Cannon properties. In August, Motorola submitted a draft Interim Remedy FS report which covers the same area as the final Remedy RI report. Sixty-seven remedial alternatives were evaluated and remedial objectives were proposed. The document was approved by ADEQ in January 1994. ATSDR completed an update to the 1988 Health Assessment.

1990 – 1992: ADEQ and Motorola continued an area-wide groundwater investigation to define the extent of groundwater contamination in the OU2 area. Area-wide sampling events were coordinated to include Motorola wells and East Washington (EW) wells. The extent of groundwater contamination prompted ADEQ and EPA to develop a second OU to address groundwater contamination before a final remedy was selected. Motorola submitted the RI report to ADEQ which confirmed that contamination migrating from the Motorola facility had extended into the EW area. Arizona Department of Health Services completed a Baseline Risk Assessment that concluded, “The risk of public exposure to groundwater is limited, and therefore causes no imminent health hazard.” EPA completed an ecological risk assessment that concluded, “. . . because of [the VOC’s] high volatility and low toxicity relative to freshwater aquatic criteria, exposure of biota to acute or chronic levels of 1,1,1-trichloroethane (1,1,1-TCA) and TCE may not be a concern. Inorganics (arsenic and lead) would be of most concern to biota because of their exceedance of the fresh water criteria, persistence in the environment, and their potential for bioaccumulation.” During this year EPA named additional PRPs: AlliedSignal (now Honeywell), ITT Cannon, and Tiernay Turbines (now Walker Power Systems).

1988: In July, questionnaires were mailed to 995 facilities located in the EW area requesting information regarding their hazardous substance use, storage, and disposal practices. In August 1989, ADEQ completed the Phase I report for the EW area. Questionnaire responses were evaluated by ADEQ to determine which facilities warranted additional investigations. At the time, four companies were found to have potential sources of contamination that may have contributed to the groundwater plume: Tiernay Turbines (now Walker Power Systems), Arvin Industries, FMC Corporation, and AlliedSignal (now Honeywell).

1985: From 1985 to 1989, ADEQ conducted an RI and initiated an investigation of PRPs. In 1987, the EW area was listed on ADEQ’s Water Quality Assurance Revolving Fund priority list. The study area boundaries were determined to be Thomas Road to the north, Lower Buckeye Road to the south, 48th Street to the east, and 7th Avenue to the west.

1983: ADEQ discovered groundwater contamination in the area known today as OU2. TCE was detected at the Desert Hills Well (Monroe and 27th Street) at 640 parts per billion (ppb), at the security center well (Central Avenue and Van Buren) at 202 ppb, and at the Eastlake Park well (Jefferson and 16th Street) at 44 ppb. At the time of discovery, it was not known that Motorola’s contamination extended beyond the Old Cross Cut Canal. Therefore, the contamination discovered in this area was initially thought to be a separate contaminant plume known as the EW area.

2025: The record of decision was approved by the U.S. Environmental Protection Agency (EPA).

2024: The Feasibility Study (FS) Report was finalized and the EPA presented the Proposed Plan to the public in November.

2022: The US EPA conducted a soil gas study at the western portion of OU3, which was incorporated into the Risk Assessment was completed in March. 

2016: In October the Remedial Investigation (RI) was finalized. 

2015 – 2022: Annual groundwater monitoring was performed and work continued on the RI and Risk Assessment.

2014: Additional groundwater monitor wells were installed and semi-annual groundwater reporting continued. EPA performed soil gas sampling at select locations during February 2014.

2013: Semi-annual groundwater monitoring for the OU3 area continued. New wells were installed. Soil Vapor Monitoring Well (SVMW)-1 continued to be investigated and EPA requested step-outs.

2012: A soil vapor monitoring well installation report was submitted in January. Groundwater monitoring continued and an aquifer test was completed. SVMW-1 showed soil gas levels above the Soil Gas Human Health Screening levels at the 18 to 20-foot zone and required further investigation.

2011: Groundwater sampling was conducted from the newly installed (Phase 3) wells. The well results were used to generate OU3 plume maps for the Upper Salt River Gravel, Lower Salt River Gravel and Basin Fill. Trichloroethene (TCE) levels continue to show a decline. Three soil vapor monitoring wells were installed and sampled for soil gas.

2010: In October and November, EPA installed seven shallow and intermediate groundwater wells as part of the Phase III OU3 groundwater investigation to help delineate the extent of the groundwater plume. Semi-Annual sampling reports were submitted in March and September of each year.

2009: On September 22, the EPA signed a Settlement Agreement and Consent Order with Honeywell and Arizona Public Service to complete an RI/FS for OU3.

2008: EPA completed the September 2007 and February, 2008 groundwater monitoring reports in February and July, 2008, respectively.

2007: EPA completed the March 2007 groundwater monitoring report which was finalized in September 2007. Several sites within OU3 conducted investigations in 2007 which are described in the individual facility histories below.

2005: EPA issued the final March 2004 groundwater monitoring report. The final groundwater investigation report summarizing the finding of the Phase I and Phase II groundwater investigation in OU3 was submitted in January. It provided recommendations for completion of the RI. The RI/FS draft work plan was submitted in April. In August, a groundwater monitoring report for the well network in the OU3 study area was submitted. Groundwater monitoring reports were prepared after each semi-annual sampling event.

2003: In January, EPA completed a supplement to the work plan to install additional monitor wells that are needed to complete the groundwater investigation. The EPA installed 16 new groundwater monitor wells as part of the ongoing groundwater investigation. EPA identified eight facilities in 2003 and four facilities in 2005 that may be potential sources to soil and groundwater contamination. EPA initiated negotiations with potentially responsible parties for investigations of soil and groundwater conditions at the facilities identified in 2003. Six agreements were reached and work began.

2002: EPA installed 15 groundwater monitor wells to investigate the nature and extent of groundwater contamination in the area. Monitor wells in clusters of up to three were installed to define the lateral and vertical extent of contamination.

2001: In December, EPA completed a work plan to conduct a groundwater investigation. Drafts of this work plan were made available to the public for comment.

2000: In June, EPA completed its groundwater flow and transport model for the site. One objective of the model was to assess the possibility of contaminants from the Companies’ source areas migrating beyond OU2. In February, EPA sent a letter to ADEQ which stated that after conducting its own modeling effort, EPA had concluded that the down gradient boundary (7th Avenue) for the study area was appropriate. EPA further stated that with the available information to date, it appeared that Motorola’s releases were not likely to have migrated beyond 7th Avenue.

1997: OU3 was formerly part of the East Washington Area which was listed on the Water Quality Assurance Revolving Fund priority list in 1987. In 1997, the EW site was not relisted on the new WQARF registry (See OU2 site history). On Nov. 26, 1997, EPA sent a letter to ADEQ creating a third OU and establishing the study area boundaries.