1969: Texas Instruments (formerly Burr-Brown) began operation as a micro-electronics manufacturing facility. Past manufacturing and disposal practices resulted in the release of hazardous wastes into the soil and groundwater

1983: The TIAA site was placed on the NPL on September 8, 1983.

1988: A ROD for the regional groundwater at TIAA was issued by the EPA. This ROD also covered groundwater contamination in Area B which includes the Texas Instruments project area. 

1990: In March, a Consent Decree (CD) was signed by EPA and the Burr-Brown Corporation (now Texas Instruments) requiring Burr-Brown to clean up the eastern-most part of the contamination within Area B. The CD also required Burr-Brown to reimburse EPA for past and future oversight costs.

1992: In January, a groundwater pump and treat remediation system for Burr-Brown began operation. This system extracts contaminated groundwater and treated it using air stripping technologies before it was used in their manufacturing processes.

1997 - 1999: In March 1997, operation of the pump and treat remediation system was temporarily discontinued while EPA built a groundwater extraction system at the West-Cap project area. In November 1999, the pump and treat remediation system resumed operation with additional water being pumped from West-Cap.

2000: Texas Instruments bought Burr-Brown.

2006: In August, the West-Cap pump and treat system ceased operation while EPA installed two additional groundwater extraction wells at the West-Cap project area. Due to construction of the new wells, groundwater from the West-Cap project area was no longer pumped to the Texas Instruments' treatment plant pending a planned upgrade of the treatment system to accommodate increased pumping.

2007: PA and the Arizona Department of Environmental Quality (ADEQ) learned that Texas instruments would be moving their manufacturing process out of Tucson within the next few years.

2008: ADEQ recommended evaluation of the deep vadose zone. Texas Instruments further characterized trichloroethene (TCE) contamination in the vadose zone and in soils immediately below the water table. Laboratory results indicated that all soil samples were below applicable regulatory standards.

2009: In September, the groundwater pump and treat remediation system was shut off at the Texas Instruments property. Since 1992, this system removed about 16.3 pounds of TCE from approximately 176 million gallons of groundwater beneath the Texas Instruments project area.

Drilling and installation of a new injection well was completed in September 2009. The new well was designed for the injection of potassium permanganate during an ISCO pilot test. The pilot test began in October 2009 and was designed to determine if it would be a feasible alternative to the previous pump and treat system. Texas Instruments continues to collect groundwater monitoring data in order to track the movement of potassium permanganate through groundwater at the site.

2010: Texas Instruments collected groundwater monitoring data in order to track the movement of potassium permanganate through groundwater at the site. Groundwater level measurements were also collected to evaluate site groundwater conditions. Data suggest that groundwater levels in most of the Texas Instruments monitoring wells have remained relatively stable.

2011: EPA issued a proposed plan to amend the existing ROD for the clean-up projects associated with Area B. This included the AANG, West-Cap, West Plume B, and Texas Instruments Project Areas. In the proposed plan, EPA evaluated several remedial alternatives including ISCO using potassium permanganate.

2012: In April, EPA issued the ROD Amendment.  The ROD Amendment selected ISCO as an appropriate technology to replace the pump and treat remedies at the Texas Instruments, West-Cap, and AANG Project Areas. The ROD Amendment also concluded that monitored natural attenuation will continue for West Plume B.

2013: Following issuance of the ROD amendment, EPA began negotiations with Texas Instruments to implement an ISCO remedy at the Texas Instruments project area. ADEQ provided technical input on the remedy design. Texas Instruments continued to collect groundwater monitoring data in order to track the movement of potassium permanganate through groundwater at the site from the 2009 ISCO pilot test.

2014: EPA, the U.S. Justice Department, ADEQ, and Texas Instruments continued to negotiate the terms for a new consent decree and statement of work. The consent decree and statement of work describes the remedial design and remedial action activities that Texas Instruments must implement as part of the ROD Amendment.