What’s the Difference Between the New and Old Arvin Ozone Monitors?

In 2010 there were two monitors measuring ozone on the outskirts of Arvin. The old monitor was 3 miles east on Bear Mtn Blvd and the new one was slightly further away to the northeast near a country school called Di Giorgio. The Bear Mtn monitor had been in place for around 20 years.

Background:  The air quality in the San Joaquin Valley has gradually improved over time due to smog rules for cars and a gradual tightening of rules for stationary sources of pollution such as water pumps and boilers.  Everyone agrees we have a long way to go before we have clean air in the Southern end of the valley.  The improvement has slowest in the Arvin area due to geography. The Arvin Bear Mtn monitor, over the past five years, was measuring the most violations for one-hour and 8-hour ozone standards. In fact, it was measuring more of these typess of violations than any other place in the United States.  The bottom line was the SJV would never be declared in compliance with Clean Air Act standards until the Arvin air was clean.

The Arvin-Edison Water Storage District, which is part of the federally built and subsidized Friant water system, leased out the ground for the Bear Mtn monitor to the California Air Resources Board. When they balked at renewing the lease in 2009, CARB and our local Air Board did not protest. They built a new monitor which is called Di Giorgio a few miles to the north and significantly further away from the backstop of hills rapidly climbing to the southeast.  The air seems to pile up in this part of the valley before it can find an escape by rising up and over the mountain passes. The Di Giorgio monitor sits in the path of rising air but the Bear Mtn monitor was in a slightly more stagnant area.

So, how significant are the differences in the readings of these two monitors? They both were working in the Summer of 2010 so they could be compared.

Here is one comparison showing a 15% average difference in ozone levels during the month with the highest values.

Aug 2010

More important than the difference shown above, which is obviously consistent and statistically significant, are the number of violations each monitor recorded of the different ozone standards.

For the 1997 8-hour ozone standard,  which the valley must comply with by 2023, the Bear Mtn monitor showed 31 violations.  The Di Giorgio monitor only had 8.  This is a dramatic difference which could make or break the 2023 deadline for this standard and potential fines for non-compliance.

Another key difference is with the one-hour ozone standard.  Over the last five years of its existence, the Bear Mtn monitor was responsible by itself for one-third of these types of violations for which we are now in non-compliance and paying an annual $29 million fine to finance local air cleanup programs.   There were 46 days with these one-hour violations from 2006-2010.  Bear Mtn had violations on 30 of those days and was the sole violator 15 times.  Di Giorgio was not close to a violation of this standard in 2010 nor this year in 2011.

We can see that Arvin Bear Mtn was a very significant monitoring station that needs to be returned.  There is no reasonable way that EPA can certify the valley with compliance of any ozone standard in the future with the results from this monitor missing.  Commonsense  should prevail on this issue by CARB, the local air board, and at the Arvin-Edison Water Storage District board.

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