> question is - what do they do with the waste from treatment.

System reliability is a big question.

> wasn't because they dumped toxic chemicals or water directly in the ground, but that [...] mechanism failed

It's not an isolated incident, leaks is actually the most common cause. Many fabs became superfunds not because the owners are evil, but because many safeguards, industrial or regulatory, were simply not in place at that time.

Let me repost an older comment.

I'd say early inexperience on semiconductor manufacturing was another major factor responsible for the pollution, many safeguards, industrial or regulatory, were simply not in place at that time. For example, many plants had storage tanks as parts of the production process, a common practice in the industry - most ended up having a massive leak, releasing various harmful chemical pollutants, including highly toxic TCE. And it seems the companies weren't doing it deliberately to save costs, many pollution events were "just" industrial accidents, and few foresaw the consequences of leaking tanks, not to say that some leaks were only discovered years later.

Now the companies are doing the cleanup under the supervision of the EPA, I think it's fortunate in a sense that these companies are the world's most powerful ones and they have the ability to pay, not some non-existent companies that already declared bankruptcy. And unfortunately, the price we are paying now for being ignorant in the early days is that the pollution still requires many years, or even many decades, of work to achieve even a basic, minimum level of cleanup. Some cleanup efforts have been active since the late 80s, and was still being continued working on in the 2010s.

Some examples:

* COMMODORE SEMICONDUCTOR GROUP

(Yes, the plant that produced MOS 6502 that we knew and love, and it was a pioneer for making the first widely-used microprocessor for personal computers, and also a pioneer for having a massive leak of TCE storage tank...)

> Background: Waste solvents were stored in an underground concrete storage tank on site until 1975, when it was taken out of service. An unlined steel tank was installed next to the concrete one in 1975. Inspections conducted by the Pennsylvania Department of Environmental Protection (PADEP) indicated that both tanks leaked.

> Cleanup: In 1981, Commodore excavated soils and pumped water from a contaminated well, then sprayed it onto surrounding fields. The volatile organic compounds (VOCs) dissipated into the air. Since 1984, air strippers have been in use to remove solvents from the groundwater.[...] Construction of the groundwater extraction and treatment system began in the Fall of 1999. In February 2000, pipelines and underground wiring were installed, pumps were installed at each of the extraction wells, and the groundwater treatment building was constructed. The treatment process equipment was installed in May 2000. Preliminary start-up and testing of the system began in August 2000.

* ADVANCED MICRO DEVICES, INC.

> Background: Two below-ground acid neutralization system (ANS) tank vaults were located at the northern and southern ends of the 901 and 902 Thompson Place buildings, respectively. Leaks from these ANS tanks appears to be the primary on-site source of VOCs to groundwater in this area.

> Cleanup: After the two acid neutralization tanks were removed, AMD excavated and disposed of soil impacted with VOCs, and installed a groundwater extraction and treatment system. Extracted groundwater was treated with air stripping technology followed by carbon adsorption. [...] The groundwater extraction and treatment system began operating in 1983 and continued through 2002, when it was discontinued with State approval to allow for an in-situ bioremediation (ISB) pilot test. The full-scale ISB system, which was initially pilot-tested from 2002 through 2004, and then expanded in 2005, includes groundwater treatment by carbon filtration and injection of an organic carbon source to stimulate the growth of naturally-occurring microbes that break down target VOCs into environmentally-benign end products.

* INTEL CORP. (MOUNTAIN VIEW PLANT)

> Background: The site is one of three Superfund or National Priorities List (NPL) sites that are being cleaned up simultaneously. The other two Superfund sites are the Fairchild Semiconductor Corp. (Mountain View Plant) site and the Raytheon site. The three sites are located in the Middlefield-Ellis-Whisman (MEW) Study Area. Site investigations at several of these facilities during 1981 and 1982 revealed significant soil and groundwater contamination by toxic chemicals, primarily volatile organic compounds (VOCs).

> Cleanup: Under EPA’s direction and oversight, Intel has implemented the soil and groundwater cleanup program at the former Intel facility. The soil cleanup has been completed at the site and all the former MEW facilities.

* FAIRCHILD SEMICONDUCTOR CORP. (MOUNTAIN VIEW PLANT)

> Background: The 56-acre former Fairchild Semiconductor Corp. (Mountain View) site is located in Mountain View, California. A facility on site manufactured semiconductors. The site is one of three Superfund National Priorities List (NPL) sites that are being cleaned up simultaneously.

> Cleanup Activities: Under EPA’s direction and oversight, [...] Fairchild Semiconductor Corp. [...] implemented soil and groundwater cleanup programs that have included soil excavation and treatment, installation of four slurry walls, soil vapor extraction and treatment systems, and groundwater extraction and treatment systems. The soil cleanup by soil vapor extraction and excavation and aeration has been completed at all the former MEW facilities, including the former Fairchild facilities. Groundwater cleanup will continue to operate for many decades in order to meet the trichloroethene (TCE) groundwater cleanup standard of 5 parts per billion. The MEW site groundwater remedy has removed over 76,000 pounds of contaminants, and has reduced contaminant concentrations throughout the multiple aquifer zones.

> HEWLETT-PACKARD (620-640 PAGE MILL ROAD)

> Cleanup: Extensive investigation and cleanup at the HP Site has been conducted since discovery of a release from a 1,000-gallon underground waste solvent tank in 1981. Interim remedial measures included excavation and off-site disposal between 1987 and 1992 of approximately 10,700 cubic yards of soil, construction and operation (beginning in 1994) of a soil vapor extraction and treatment (SVET) system; and groundwater extraction and treatment beginning in 1987 and continuing to the present day.

> NATIONAL SEMICONDUCTOR CORP.

> Background: The National Semiconductor Corporation (National Semiconductor) previously manufactured electronic equipment at this 50-acre site. Underground storage tanks, sumps, and pipes are the suspected sources for contaminated groundwater and soil in Sunnyvale underneath the site.

> Cleanup: Beginning in 1982, contaminated soils, leaking tanks and equipment were removed. Subsequently, National Semiconductor initiated a program of pumping and treating the groundwater to contain the contaminated plume while further site studies were underway. In 1989, National Semiconductor began investigating the type and extent of contamination at the site. The investigation was completed in 1991, and the EPA selected the final remedy for the site. Construction of the remedy began in 1991. The final cleanup remedy, which includes soil vapor extraction and operation of the groundwater extraction and treatment system, is ongoing.