The developer should have waited for Donald Trump to abolish the EPA, then no one would have known about the problem. Now, liberal techies will never want to live on this street.

This is the most difficult problem that Mountain View faces, let alone the valley, is the fact that toxic chemicals were dumped for decades here. And the chemicals never degrade, in fact they get more concentrated over time. I know about the problem because my family was involved in toxic detection. I also lived near a toxic dump in my town and was a witness to the Woburn Mass. pollution problem made famous by the book, “A Civil Action”.

This is the most difficult problem for development in the valley. No one should live in a place that has the likelihood of killing you due to carcinogenic chemicals or heavy metal pollution. The chip industry is notorious for dumping the used chemicals to make the semi-conductors that made the valley what it is today. And no one arranges funding to the EPA to clean up the messes, instead, they funds get cut, and the people suffer the health problems because of it.

They have been trying to clean up TCE in that area for DECADES and it's still there. This is a case of a completely unscrupulous developer clamoring to make his money by selling people houses on land that will bleed TCE into their homes. When the cancer shows it will be too late. It's criminal in my mind to even offer housing in that area. Also, liners don't work over time so don't let them BS you with that false hope of safety.

The most important question:

How in the world did the City of Mountain View approve this project in the first place? Who did the environmental study that allowed such a polluted sight to be allocated for residential buildings? This situation is a clear indication that the City is a questionable operation. What benefits were promised by the developer to build this project? What CERTIFIED environmental analysis was performed prior to its approval? It appears that the City may have some responsibility for this problem.

"How in the world did the City of Mountain View approve this project in the first place?"

Jeez, some of you people. . . This topic has a very long and detailed history in the Voice. Including answers to many questions like that above, along with what can and can't be removed, and informed comments by such local environmental experts as Lenny Siegel (who followed the whole thing and helped spearhead clean-up efforts) on what can and can't be cleaned, what the contamination does and doesn't expose people to (some have freely but cluelessly speculated in these pages -- more so, the less they knew).

If you missed it all, you can catch up by doing a little research on your own rather than asking other people to inform you. (The "Search" box at the upper right of the web page is very helpful.) M-E-W or MEW (from the boundary street names) is the usual acronym for the zone where the underground contamination occured.

This is long but it is important

If you bother to read this article TCE Removal from Contaminated Soil and Ground Water published in 1999, it can be found here (Web Link it raises more questions than solutions.

It in fact reported this:

Moffet Field Study - A form of in situ aquifer bioreclamation has been studied at a test site on the Moffet Field Air Station in California (Roberts et al., 1989; Semprini et al., 1987). The test aquifer was shallow, confined, and composed of coarsegrained alluvial sands. To create the test zone, an extraction well and injection well 6 meters apart with 3 intermediate monitoring wells were installed. The 3 monitoring wells were used to gather data for tracer and degradation studies. Parameters including methane, oxygen and halogenated solvent concentrations were continuously monitored…

RESULTS FROM THE MOFFET FIELD STUDY DO NOT PROVIDE A WHOLESALE LICENSE FOR INITIATION OF IN SITU BIOREMEDIATION OF AQUIFERS CONTAMINATED WITH TCE. Injection of methane, oxygen and other nutrients into an aquifer to stimulate a methylotrophic population would, in aquifers having little TCE sorption potential, push aqueous-phase TCE from the microbially stimulated portion of the aquifer before the appropriate bacteria could adapt or be stimulated. This technological limitation may be overcome in the future by redesigning the injection protocols currently utilized for in situ biological remediation. Such scenarios have been developed by Roberts et al. (1989). HOWEVER, GIVEN THE LOW RATES OF TCE DEGRADATION IN INITIAL FIELD TESTS, THIS SCENARIO AWAITS DOCUMENTATION.

“Summary

Due to its chemical structure and unreactive nature, TCE is not easily transformed to environmentally safe compounds. THE MOST EFFICIENT AND COST EFFECTIVE METHOD FOR REMOVAL OF TCE FROM POLLUTED GROUND WATER AT THIS TIME APPEARS TO BE AIR STRIPPING, ESPECIALLY FOR AQUIFERS WHICH ARE UTILIZED AS POTABLE WATER SOURCES. Aquifers subjected to bioremediation would require further treatment of the ground water before human consumption, thus increasing the overall cost.

The primary alternative now being studied for removal of TCE from contaminated soil in the vadose zone is soil venting. Soil venting appears to be both efficient and cost-effective for VOC removal from the vadose zone in many instances. LIMITATIONS WILL OCCUR IN SOIL CONTAMINATED WITH A MIXTURE OF WASTE (TCE MIXED WITH LOW VOLATILITY WASTE) AS WELL AS IN HIGHLY IMPERMEABLE SOILS. These limitations highlight the need for continued research into soil bioventing, including anaerobic and aerobic techniques based on co-metabolism of TCE driven by the less volatile constituents.

WITH NEW RESTRICTED AIR EMISSIONS STANDARDS, THE USE OF AIR STRIPPING AND SOIL VENTING TECHNOLOGIES MAY REQUIRE THAT OFFGASES FROM THEM BE TREATED IN SOME MANNER BEFORE DISCHARGE TO THE ATMOSPHERE. Use of biological reactors to treat air or water streams from air strippers or soil venting operations may be a cost effective alternative to GAC. The movement toward clean air will require that research and demonstration studies be conducted pertaining to development of efficient cost-effective technologies. Biological remediation, though unproven at this point, could destroy TCE completely, thus meeting the intent of Section 121 of CERCLA. More research is required, however, before full-scale implementation of such technology. Anaerobic treatment of aquifers contaminated with TCE may be a viable option.

EXTENSIVE MONITORING WOULD BE NECESSARY TO ASSURE THAT THE FINAL PRODUCT OF THIS REMEDIATION IS NOT VINYL CHLORIDE. Extensive protocols also may be developed for utilization of native methylotrophs in aquifers through stimulation with methane and oxygen before contact with TCE contaminated ground water. Additionally, biological methods may be designed to effectively treat off-gases from air strippers or soil vacuum extraction systems.

It would appear that there is LIMITED SUCCESS in cleaning up TCE. In fact it would appear that a waste processing facility would need to be built on top of that land due to the air emission standards. TCE is so water soluble that the only way to remove it thoroughly is to dig a hole at least ½ mile deep because of the groundwater effect in Mountain View. I have justified skepticism that the site can be cleaned to the extent that it could be considered safe for a residential project. Lenny Siegel surely should have known this, but it appears he did not discuss the difficulty of the problem, I do not know why.

[Post removed due to disrespectful comment or offensive language]

Lenny Siegel started the Center for Public Environmental Oversight. His background in community activism is long and commendable. But now that he's on the city council, he actively advocates for building on top of contaminated soil. He says as much in his own publication here: Web Link

He says that the toxins have not been eliminated but advocates a build, mitigate and test approach. Well, Google did that and it hasn't worked out so well. Many of their employees were subjected to toxic levels of TCE. Google concentrated on the effects of TCE on pregnant women so many male employees were reassured under the false belief that TCE was only a danger to women.

This decision to build on toxic land is a breach of trust. Yes, we need more housing, but building on top of toxic soil with the promise of regular air quality tests is too similar to preying on unsuspecting young families who likely have little to no understanding of cancer risk and environmental causes. Google did regular air quality tests and still accidentally subjected their employees to months of toxic levels of TCE. Web Link

Young families trust their government and the experts to be making the right decisions. However, the onset of cancer can take years so the consequences may not appear until long after Lenny Siegel has left the Mountain View city council. Maybe this is a risk he should not be taking with our lives.

If the groundwater beneath the site still is contaminated, the surface soil will re-contaminate unless an impervious barrier is buried beneath the entire site to prevent TCE and other contaminants to re-infiltrate the soil above. I would not recommend that any adults of child-bearing age or with children or who wish to have children live in any housing constructed on that site. It's like a mini Love Creek in Niagara Falls, NY.

I read the paper written by Lenny.

It appears to paint a very rosy picture. Unless you start to understand how things can go wrong very easily. He assumes that all the remediating methods described will not fail. There are many problems with the solutions described because of the following:

We live in a tectonic area, barriers will be destroyed easily in the case of a significant tremor, not enough to do damage to the buildings.

Materials will degrade regarding underground barriers and vapor collection, these will eventually break down, thus requiring in the worst case, complete destruction of all construction above it.

The current “safety” levels are not fixed, future research may indicate that much lower levels are just as dangerous, the science is always improving, but it can result in unsafe standards now.

Finally, it seems that Lenny wishes others to take a gamble with their family’s health by choosing to build on an unwarranted risky location. Those sites should never be used for a residence, but for industrial and commercial and the least. This at least reduces the time of exposure because a typical workday will be 10 hours a day where a person living at a residence can potentially be exposed at 14 hours a day.

Some places should not be developed as residential. Let the developers live there with their families once "the all clear" is given.

"Lenny Siegel started the Center for Public Environmental Oversight. His background in community activism is long and commendable. But now that he's on the city council, he actively advocates for building on top of contaminated soil. He says as much in his own publication . . ."

" I read the paper written by Lenny.It appears to paint a very rosy picture. . ."

It doesn't occur to either of you that Lenny Siegel might just come to conclusions contradicting your expectations because he KNOWS MORE about the subject than you do??

This is the often the problem when people embrace notions about perceived threats that they understand very little about at all. The sense of threat becomes the main thing important. Subsequently, their own assumptions are never ever closely examined, only defended. If they encounter competent information (or even in some cases, irrefutable proof) contradicting their assumptions, well, there must be something wrong with the source, so let's attack its credibility. (No shortage of ammunition available for that: websites by the thousand offer comforting support -- no matter how misleading, uninformed, or plain wrong -- for every technical-risk anxiety du jour; you can conjure endless talking points without ever having to examine your core assumptions, let alone set aside those that are false friends. It's the point Stewart Brand made about environmental "romantics" vs "scientists:" Both are sincere, but the scientists are driven by a respect for reality and are eager to shed beliefs that are wrong, The far more numerous romantics are driven by the primacy of their own current notions and will fight against anything that threatens those, especially when wrong.)

Hello Reader,

You Stated:

t doesn't occur to either of you that Lenny Siegel might just come to conclusions contradicting your expectations because he KNOWS MORE about the subject than you do??

My father and I worked for a company called Dasibi Environmental Corp, that produced toxic gas analysis equipment certified by the EPA for companies to comply with the Clean Air Act. My father was a Vice President of that company. So your assumption that my knowledge in this area is limited may have been not well founded.

You also stated:

Subsequently, their own assumptions are never ever closely examined, only defended. If they encounter competent information (or even in some cases, irrefutable proof) contradicting their assumptions, well, there must be something wrong with the source, so let's attack its credibility.

However, your claim there is irrefutable truth is questionable. I demonstrated that the TCE pollution control methods are quite complex. I have asked questions regarding the long term effectiveness of said pollution control. It would appear that there are many that assume that this pollution control is “fool-proof” or “infallible”. All I am doing is demonstrating that this highly unlikely to be true.

You stated:

Both are sincere, but the scientists are driven by a respect for reality and are eager to shed beliefs that are wrong, The far more numerous romantics are driven by the primacy of their own current notions and will fight against anything that threatens those, especially when wrong.)

You simply have to understand, I am basing my observations in a true scientific sense, I am demonstrating appreciation of the “real-world” consequences of relying of the face value of ones opinion. The Document written by Lenny Siegal in fact was a promotional document for the City of Mountain View if you read the following text he stated:

Ten years ago or so Mountain View pioneered the practice of notifying prospective homebuyers that vapor intrusion was being investigated or mitigated on development properties. This now occurs routinely. IN FACT, IN APPROVING A HOTEL PROJECT ABOVE THE SAME PLUME AS THE PLYMOUTH STREET OFFICE PROJECT SHOWN ABOVE, THE CITY COUNCIL VOTED TO REQUIRE THAT PERMANENT HOTEL EMPLOYEES BE TOLD THAT THE PROPERTY IS SUBJECT TO AN ENVIRONMENTAL RESPONSE UNDER THE SUPERVISION OF THE WATER BOARD.

So just telling the people that work or reside at a toxic dump site alone makes it safe to be there? This is a very bad public policy because it takes advantage of uneducated people not understanding the risks of being where they work or live.

Reader, is that reasonable?

Why did the City Council approve the project before testing was done?

The blame lies completely with the Republican party. They repeatedly block any effort to clean up toxic waste sites and they continue to block critical infrastructure projects that would prevent this problem going forward. Any extinction level event that happens on this planet due to human error can lie in, terms of blame, completely at the feet of the conservative political party of this country.

Check for 1,4-dioxane ..We are having the same issue here in tucson Arizona military base used the to clean planes so it all got dumped into the soil and contaminated the water wells that was like 50 years ago..found out about in the late 1980s later they settled a lawsuit.. but now they found another chemical 1,4-Dioxane was was commenly used with tce and is just as bad or worse but did not have the means for testing for it until recently so now the government sickened us with cancer and they are trying to keep it quite..

@Mark Noack:

MEW stands for Middlefield-Ellis-Whisman. The 'M' does not stand for 'Moffett'. Please correct your article.

I can't believe it happens in the center of Silicon Valley. I used to work for environmental firm to test soil and ground water in foreign countries for US corporation to build industrial and commercial projects. Whenever there was trace of toxics in the sample, they suspended the development until the soil got cleaned. It never occurred to me on US territory, US companies would ignore the pollution and got approval to build before soil got cleaned

Hello ALL,

I am not a fan of political parties. It is a SIN on ALL OF THEM. How did we get to this place?

It took 20 years to get rid of Lead from gas and other products, it took 20 years to recognize DDT and Dioxin. We thought we were providing the public safety from poisons or toxins. However, the political solution is not to clean up the problem. Instead the rules are to let toxins remain, and just give people a warning they are being exposed to harmful chemicals or elements.

Why, because the cost and effort to actually CONTROL the pollutants is so high, that the various governments in the U.S. would rather pass the risk off to someone else, instead of solving the problem. This is being done by both political parties and both are equally responsible for the damage they are causing.

In particular, Lenny Siegel has never discussed his education in this field. I would like to know what degree he has?

My father was a Dr. of Chemistry, a PHD, my 20+ years experience with his industry after I was 15 provided me with much education regarding pollution. I have worked on many Air and Water Pollution projects regarding cleaning and detection. So I clearly do not have a formal education. But my experiences with the EPA, NASA, DOD, and Harvard School of Public Health on pollution control projects is significant.

My girlfriend and I lived on Murlagan Avenue from 2006 to 2014. The TCE contamination killed our two cats and gave her Polycythemia Vera. That entire neighborhood should be condemned. It is unfit for human habitation.

I'd love to see the cancer and birth defect statistics for that neighborhood.

I'm sure the MV Voice will delete these comments. Mountain View is a city in denial of many things.

The Voice has (in its years of coverage of this topic) published disease statistics in the affected neighborhood. With expert commentary pointing out that how little they revealed, especially when the diseases people were so eager to point to were of types not causally associable with this specific contamination.

It's human nature to jump to conclusions like "the TCE contamination killed our two cats and gave her Polycythemia Vera" but the reality, much harder for many to accept, is that confident self-diagnoses are almost always wrong. If the commenter I just quoted had grounds for such conclusions, they weren't given (usually they're pure guess). The claim consists of asserting a belief, rationalized as needed with plausibility arguments.

Someone else's two cats died of cancers; she learned that this is (very rarely, but occasionally) correlated with rabies vaccination; so she testified tearfully to the City Council that vaccination "almost certainly" killed her cats. I'm sorry but that's BS: notions don't become fact proportionately to how strongly you believe them, how emotionally you shout them, or how many bumper stickers about them decorate your Prius.

It's tough for some people to accept that pets die, and humans get grave diseases, even without any unusual environmental factors at all. But add a headline-making abnormality like the MEW solvent plume and it becomes the irresistable explanation for the thousand ills all flesh is heir to.

Hello Reader,

I understand your point of view when you state:

It's human nature to jump to conclusions like "the TCE contamination killed our two cats and gave her Polycythemia Vera" but the reality, much harder for many to accept, is that confident self-diagnoses are almost always wrong. If the commenter I just quoted had grounds for such conclusions, they weren't given (usually they're pure guess). The claim consists of asserting a belief, rationalized as needed with plausibility arguments.

Unless you are willing to actually live in the proposed new housing, or in a known polluted area, please do not ask anyone else to take the risk? It is easy to rationalize the potential risk when you do not take it. TCE has a complex history regarding poisoning I grant you. But it is tombstone science, you track illness or death long enough to establish cause and effect. That to me sounds like you want others to be your guinea pig. I am not willing to put others in harm’s way, only to eventually determine the mistake later with their suffering.

She does not have the genetic marker usually associated with PCV. TCE exposure is a known cause of PCV. Her physician said as much, and we researched it. The two cats died young, just under ten years old. I consulted a lawyer, we had an excellent case against numerous parties, but it would have required staying in Silicon Valley, which neither of us had any desire to do. She bought a very nice fixer-upper in Florida for $10,000. Mountain View was the worst place either one of us has ever lived (we're in our 60s and we've been around) in every way. Getting out was a great relief. Hubris is rampant in California.

Just an update

I discovered the state of California Air Resources Board knows about airborne TCE if you read the following webpage (Web Link

In fact ambient monitoring is required by the CARB if you read this document (Web Link

The known health problems are discussed in this article (Web Link

There appears to be a requirement on behalf of the CARB, and this appears to be in fact not happening in Mountain View where it is a known toxin. I am going to contact them to see what monitoring information they have regarding the City of Mountain View. From what I can tell, they are not monitoring Mountain View site at all.( Web Link This means that the CARB is not getting an accurate measure of health risk in Mountain View.

The EPA is in fact not monitoring the ambient air quality if you look at the site reports on the EPA website. I am very confused, if vapors are getting inside homes and businesses, it must be penetrating from the outside air. Thus the outside air quality must be significantly poor if venting and pumping the TCE vapors from inside the buildings back out of them is required. The only source it can come from is the outside air regarding vapors. The pumps are simply filtering out the ambient TCE vapors before pumping the clean air inside to displace the TCE vapors. So there must be a significant amount of ambient TCE pollution in Mountain View. Measurements are being avoided to prevent the real story from being discovered.

This is very disconcerting.

Just an update:

I asked the Council about the indeterminate problem with TCE, and Lenny Siegel criticised my question by saying he had up to date ambient TCE data. Alana Lee stated that 1 PPM is considered unsafe. Conversion means 1000 micrograms per litre.

From what I can see, the latest Vapor data results I can find on the EPA website was 2014. This information seems extremely out of date. So far I have not received any updates. Lenny Sigal claims to have up to date data, I look forward to receiving it.

Lenny Siegel tonight during the City Council Meeting break claimed to me that the NBC Investigates report I have been using as a reference was presenting false information. I was completely surprised he would say that. So I asked why didn't he seek a retraction or correction in the story? He didn't seem to indicate he ever tried. This behavior activated my suspicious reptilian brain. My intent is to contact Steven Stock who broadcast the following report (Web Link

I await an email by Lenny Siegel to explain how the report could be misleading.

My first reaction to this comment was that if such a misleading story existed, how could the NBC Investigates broadcast this news story? They surely would do all efforts to fact proof the story so that no one could disqualify its validity. From what I see, Steven Stock has no history of making false statements or even accidentally broadcasting misleading stories. I am concerned we are being given another "fake news" excuse.

> I am very confused, if vapors are getting inside homes and businesses, it must be penetrating from the outside air.

Nope, the vapors come from the ground through foundations into homes and businesses. Vapors also get into the outside air but they breaks down/disperse far more quickly there, keeping the concentration low

> Thus the outside air quality must be significantly poor if venting and pumping the TCE vapors from inside the buildings back out of them is required.

Flawed logic.

In response to Me you stated:

“Nope, the vapors come from the ground through foundations into homes and businesses. Vapors also get into the outside air but they breaks down/disperse far more quickly there, keeping the concentration low.”

Just to let you know TCE does not breakdown in the air, it only breaks down in the presence of metals, so your claim if factually false please read the following:

Chemical instability[

Despite its widespread use as a metal degreaser, TRICHLOROETHYLENE ITSELF IS UNSTABLE IN THE PRESENCE OF METAL OVER PROLONGED EXPOSURE. As early as 1961 this phenomenon was recognized by the manufacturing industry, when stabilizing additives were added to the commercial formulation. Since the reactive instability is accentuated by higher temperatures, the search for stabilizing additives was conducted by heating trichloroethylene to its boiling point in a reflux condenser and observing decomposition. The first widely used stabilizing additive was dioxane; however, its use was patented by Dow Chemical Company and could not be used by other manufacturers. Considerable research took place in the 1960s to develop alternative stabilizers for trichloroethylene. Other chemical stabilizers include ketones such as methyl ethyl ketone.( Web Link

As you know air does not contain much metal. So your claim it breaks down is inaccurate.

As far as dispersal in the air, TCE is a very heavy molecule compared to O2, N2, C02 the primary gases in the air. Thus it tends to remain low in altitude in the affected toxic sites and is hard to spread if the area has obstacles, like trees, buildings, hills.

Since Mountain View is known to have a lot of these, the vapors are in effect trapped in the valley. Your claim that it will disperse to lower concentrations also seems to be evidenced as incorrect given the NBC story describing migration away from the “known” “hot-spots” to "unknown" "hot-spots". Please look at this information (Web Link

As the EPA said, they do not know where or how long TCE is building up in the air in this report.

Having no knowledge regarding this public danger is very disturbing. Is this questionable logic?

thanks The Business Man. I do not think Ellison, Jobs, Gates, Zuckerberg or a lot of other successful business people required "A DEGREE!" to be successful here in technology. As a graduate degree R&D engineer (UCSB Scientific Instrumentation) I understand your reluctance 'to just believe' Lenny. Your personal experience in absorption spectrophotometry for decades of EPA and university studies is 'good enough' real-world credentials for me. Others may differ.

Based on the orders-of magnitude decreases in instrumentation costs - I think a local-city-wide monitoring effort is both quite technically doable, and FINANCIALLY not onerous for Mountain View. The Public Good, is not free. Setup by a contractor - the city Public Works Dept. could monitor this (like it does for Water and Sewer issues.) Move some portable sampling stations - to any areas proposed for residential development - and CHARGE THE DEVELOPERS a fee.

The technology history of Silicon Valley - also left some bad residuals in Mountain View.

Hello Lenny Siegel,

Here is my understanding of the “Big report” you sent to me after I briefly reviewed it.

Table 2 seems to indicate that there has been NO approval of the results by the EPA regarding the OM&M Plans and the Response Action and Implementation Reports, why did you not see this?

In table 3 the test sampling was not appropriate regarding outdoor air, the sample was only 8 hours and once done in every 4 years. THIS SAMPLING SCHEDULE SIMPLY CANNOT ESTABLISH STATISTICAL SIGNIFICANT RESULTS. Only at least a bi-weekly sampling traced throughout a year would be required to satisfy the real measurements of the ambient air. Also, to deal with outdoor sampling, given that those who do not live in an indoor TCE controlled building, you must take a 24 hour sample. So these results are NOT appropriate.

Just think that a person’s air quality where they need to open windows and use fans will suck in the TCE, and then the vapors can either attach themselves to surfaces or get trapped due to their heavy weight, typically a window is at least 30 inches above the floor, the TCE gets sucked in but settles below a windows pane so that it cannot escape. TCE is too heavy a molecule, the measurements will vary significantly in a variety of conditions. .

So, my question is who established the sampling standards? Since when is 1 test done every 4 years can establish safety? You know that in the course of the year the levels will change, especially during the summers due to heat. The test was performed in October, alone. To prove safety a continuous sampling schedule is required to establish actual safety. THE SAMPLING RATE IS SIMPLY NOT ENOUGH TO ESTABLISH STATISTICAL SIGNIFICANCE. I AM SURPRISED YOU DON’T KNOW THAT. This report in my opinion is simply unacceptable regarding the scientific standards one must achieve.

Hello Lenny,

I forgot to tell you, I do have an Associate’s degree in Life Sciences, along with 10+ years of ambient air monitoring experience.

To address the information provided in the EPA report

Just in case you do not know, the relative temperature and humidity will directly change the rate of TCE vaporization.

Given that the report indicates that one sample (335OUT‐1) was taken on 10/12/2016, the weather was 70 degrees F at highest and 74% humidity, this would cause a significant decrease of TCE vaporization.

Given that the report indicates that another sample (335OUT‐1) was taken on 10/10/2016, the weather was 70 degrees F at highest and 61% humidity, this would cause a significant decrease of TCE vaporization.

Given that the report indicates that one sample (440OUT1) was taken on 2/7/2016, the weather was 72 degrees F at highest and 61% humidity, this would cause a significant decrease of TCE vaporization.

From what I read form this site (Web Link from March to September, the temperatures themselves are much higher in average from 13 degrees to 30+ degrees F, and in my experience also very much drier, thus the TCE vaporization rate will significantly increase during that time. Taking 3 samples on only 3 days of the year is simply unacceptable scientifically.

Just in case I need to I am about to demonstrate how ambient air monitoring is required to do in order for it to be validate scientifically.

First, the devices doing analysis must be certified by the EPA or NIST to be used in such monitoring.

Second, documented validation tests regarding accuracy will need to be documented at least once every 3 months of use.

Third, the use f the devices requires documentation to ensure they are operated correctly.

Fourth, the persons operating the devices must be certified to act as technicians during the monitoring.

Fifth, it is required to have at least 3 devices per site monitor to establish device reading validation, if variance between devices are recorded significant enough, the entire data recorded is invalidated.

Sixth, A reading of the devices must be logged at least in 15minute intervals for 365 days in order to provide the daily, weekly, monthly, seasonally, and annual trend information required to establish it as a ambient air monitor and not just a sample or snapshot.

If any of these is not performed, it is clearly not an ambient air monitoring program, thus the results cannot be scientifically certified and approved. The fact that the EPA published this document did not declare Mountain View air safe, only publishing a report that in itself contains such scientific problems. You need to get another study dine with the above requirements satisfied, otherwise it is NOT safe to assume that the TCE vapors in Mountain View are below hazardous levels.