School soil still safe
The letter concludes that “Detected concentrations of VOCs at the Site are well below human health risk based levels and are not expected to increase. VOCs at these concentrations do not pose a threat to the health of individuals who attend classes, who work at the school, or who might otherwise use the school’s property.”
The DTSC letter and the scientific report arising from the most recent soils testing affirms the site is environmentally safe for students, families, staff and the community, and supports the 2014 and 2015 environmental site approvals previously granted by the DTSC.
“IUSD’s priority is the safety of our students, their families, staff and the community,” said IUSD Superintendent Terry Walker in response to the letter and report.
“In selecting the Portola High School site and throughout construction, IUSD’s process, procedures and findings have been based on the scientific studies and tested principles of top environmental agencies at both the federal and state levels, in addition to a multitude of leading environmental experts.
“Since the inception of the project, the Board of Education has directed the District and those working on the school site to go above and beyond to ensure safety,” Walker said. “After this third series of testing, the California Department of Toxic Substance Control once again determined the school site is safe for students, staff and the community. We share in the community’s excitement and look forward to opening this state-of-the-art educational facility in August. Portola High School will be home to generations of Irvine students and will continue IUSD’s tradition of excellence.”
But how safe is safe? We read the report, which is 52-some pages of text, stretching to 500 pages long, when tables, lab reports analysis and notes from the many people and organizations involved in the analysis and testing process are totaled.
Actually reading the report, one thing that stands out is that the most conservative choices in analysis were made at every point.
In other words, the scientists err on the side of maximum possible risk. Whenever there’s a choice in the analysis, they incorporate the riskiest option.
For example, two standards of risk assessment were used in looking at potential risks at the school site, a residential standard and an occupational standard.
The residential standard of analysis assumes that an individual would be at the high school site for 24 hours per day, 350 days per year for 26 years. That’s right: all day, every day, (with two weeks off per year), for 26 years! Basically not within the realm of probable or even possible, but that’s one standard used.
The less rigorous occupational standard assumes a staff member would be at each location for 25 years, 250 days per year for 8 hours per day and students would be at each location for 4 years, 250 days per year for 8 hours per day.
Now that’s much more imaginable, right? A 25-year employee at the new high school might work 8 hours a day, and we should make sure anyone doing so is safe.
At the much more conservative residential standard (on site 24 hours a day for 26 years, two weeks off a year), the newest soil samples reveal that on a scale where the “level of concern” for exposure to chemicals is shown as the number 1.0, the hazard index at Portola High School site was 0.155. That’s fairly easy math to comprehend: 0.155 is way less than 1.0.
The reports include another risk management measure for chemicals that’s a bit less intuitive. It’s for chemicals known to be carcinogenic at scientifically established levels.
The results for the soil samples at Portola are divided between those taken at 5 feet beneath the surface and those taken at 15 feet beneath the surface.
For samples taken at 5 feet: The estimated carcinogenic risk using the maximum detected concentrations was 1.8E-06, within the EPA risk management range of 1E-04 and 1E-06.
For samples taken at 15 feet, the estimated cumulative carcinogenic risk was using the maximum concentrations detected was 1.45E-06.
“Those concentrations are within the risk management range of 1E-04 and 1E-06,” the report concludes.
Huh? Not so intuitive. So we asked the DTSC to explain what those numbers mean. Here’s the response:
“Both DTSC and USEPA’s risk management range is between 1 in a million (10-6) and a 1 in ten thousand (10-4). This means that when the estimated risk is within this range, the regulatory agency makes a decision on what action to take based on various factors: ecological, human health and welfare, legal, economic and behavioral factors.
“One way to think of a 1 in a million risk of cancer is that if there were a million people on the school property, there is a chance that one person might get cancer from being exposed to chemicals on this site. In reality, there will not be a million people on the school property in any point in time, so this is a very conservative, health protective assumption.
“In terms of the maximum risks estimated for a hypothetical future resident using the 5 and 15 foot data, the risks are very close to the 1 in a million mark, being 1.9 in a million and 1.45 in a million.
“These estimates are actually overly conservative, since the maximum detected VOC concentrations do not all occur in one location, and even if they did, the chance that a person would spend 26 years of their life, 350 days per year, 24 hours a day, on that spot is unrealistic. In other words, there are many layers of added protection in each step of the risk assessment process, to ensure that people are safe.”
So, to sum up: low concentrations of chemicals in the parts per billion range were found in the soils sampled, as have been in earlier testing.
The maximum concentration of each chemical found at any of the testing locations was combined with all the others found, to create a “maximum detected VOC concentration” number, even though no place at the site has that combination.
That number was then used in a scenario where someone basically never left the spot where that imaginary maximum concentration is for 26 years. And then imagine one million people doing that.
Out of that number, less than two in one million could get cancer from those chemicals, based on an exposure scenario that will not exist at the school site.
The studies upon which DTSC based it’s confirmation of the safety of the site also looked at the possibility that any of the VOC gases found in low levels in the soil at the site could find it’s way into the school buildings.
The model used to make the vapor intrusion analysis also uses the most conservative choices, including assuming that the soil present is more porous than the actual compacted soil of a construction site.
The model also assumed, according to a DTSC response to an ICN query, that “the foundation slabs were assumed to be 15 centimeters (6 inches) thick. Also, the foundations slabs were assumed to be cracked for the modeling. These cracks allow for the passage of contaminants from the subsurface into the school buildings. Undoubtedly, the foundations at the school are thicker than 15 centimeters and have very few cracks.”
“Hence, the J/E modeling for the school, again, would over-predict the exposure risk due to the conservative assumption of a relatively thin foundation that is cracked.”
So, with every assumption made much more conservative than what is actually likely to ever exist at the high school, the DTSC once again concludes that “Detected concentrations of VOCs at the Site are well below human health risk levels.”
Finally, and once again, some of the top scientific minds in California confirm that the new school site is safe, and would be safe if people lived there for years and years and years.
It’s safe for our kids, their teachers and the staff that supports them. Now, let’s move on to celebrate the grand opening in August.