SEA’s Fenceline Monitor Report for September ‘97



Review of the fenceline reports and raw data from the Tosco SFAR refinery for the month of September ’97 reveals that the overall situation with emissions and the status of the various monitoring equipment to be much unchanged from the previous month.

As was the case in August, the various open-path monitoring systems on the North fenceline generally appear to be functioning properly. On the South fenceline, however, we see some real problems. The FTIR unit on the South continued to operate well below its capacity throughout the month, and the UV unit on the South continues to produce data that appears to conflict with the results generated by the other equipment.

Again in September, our analysis of the raw spectral data generated by the North FTIR unit reveals more than twice as many reported detections or "hits" for MTBE than are indicated in Tosco’s reports. Also, n-hexane is detected on 29 occasions, all of which went unreported during the real-time monitoring at the refinery. Besides the ever-present "ambient" gases, (including methane, carbon monoxide, and nitrous oxide) MTBE and n-hexane continue to be the pollutant gases most often detected by the North FTIR equipment and were the only gases detected by us in this September data set.


Of the three types of optical-remote equipment in use here, only the FTIR units allow for re-analysis of the original spectral data. Because of this, a vast majority of the work that goes into preparing these monthly reports involves working with the raw FTIR spectra.

Tosco’s contractor reports an on-line percentage of greater than 99% for the North FTIR unit during the month of September. In all, more than 8,300 individual spectra generated by the North FTIR were re-analyzed for this report. The list of gases which are monitored was expanded to 13 in September. (see Summary Chart)


The only compounds detected in this September data set were MTBE and n-hexane. We have been able to confirm the presence of MTBE in 128 spectra, compared to only 51 reported by the refinery. These are very similar to the results arrived at in the August data set. As with the earlier data, it is important to recognize that the additional "hits" which we were able to identify do not necessarily indicate a discrepancy between our results and those provided by the refinery’s contractor Terra Air Services. A review of the summary chart will show that the peak concentration figures for MTBE once again match very nicely between the two data summaries, and that the additional "hits" which occur can be attributed to the lower detection limits we were able to achieve for this compound.


We have identified n-hexane in 29 of the 8,319 spectra from September. Tosco’s report indicates that this chemical was not detected at all during the month. As with MTBE, it is important to note that there is not necessarily a discrepancy here, and that these hits come as the result of lower detection limits. In this case, however, a quick comparison of the reported detection limits for n-hexane between the two data summaries show clearly that there is vast room for improvement by Tosco’s contractor in this area.

N-hexane absorbs light energy (and is monitored for) in a region of the infrared spectrum commonly known as "the C-H stretch". In this region, centered near 2,900 wn, scores of other hydrocarbon molecules are also known to exhibit strong absorbance features. If one assumes that any large hydrocarbon release from the refinery is likely to contain some n-hexane, this compound could then be effectively monitored as a "surrogate compound" for this class of hydrocarbon molecules.

During the 6-moth test phase of the fenceline montior project, we learned from one of the contractors involved that the presence of n-hexane can indeed be a very good indicator of total hydrocarbon emissions. In light of this, we believe that the effectiveness of the current fenceline monitoring system could be greatly enhanced by a marked improvement in the detection limits for n-hexane on the FTIR monitors.


A review of the summary table will show that we did not detect Ammonia even once in the September data set. Terra, on the other hand, reports 118 confirmed detections of this compound. This circumstance is very similar to the one concerning n-hexane, except that now the situation is reversed. Now Terra’s superior detection limits for Ammonia have resulted in the detection of this chemical at levels which would have "slipped by" us. This is clearly something we need to work on. By making adjustments within our "script file" we should be able to improve our detection limit figures for Ammonia in future month’s reports.

South FTIR

Throughout the month of September, the FTIR unit on the South fenceline was producing irregular spectra which severely hampered the unit’s performance. This problem (apparently with the MCT detector) did not render the unit totally unusable, although it did adversely affect detection limits for all monitored compounds.

As was the case with the August data, an attempt was made to analyze the data from the South FTIR unit in the same fashion as that from the North. We found, however, that the excessive noise present in the spectra made a thorough analysis of these data files very difficult. "False positive" reporting was a consistent problem for several of the monitored compounds. In the end, we decided again to analyze only the spectral files from the North FTIR unit.

Looking ahead at some of the data we have recently received, it appears that the problem with the South FTIR was not fully resolved until sometime in early November.


UV Monitors

For the 8 compounds monitored by the UV systems, we cannot provide any more detailed information than what is available in Tosco’s report at this time. We have acquired some new software, and in future reports we will be able to access the databases for the UV and TDLS systems which we were unable to do for the present data set. This will allow us to examine the results from these monitors on a minute-by-minute basis. Still, because of the way these monitors work, there is little we can do to independently verify the validity of the results.

As with the August data, the UV monitors on the South are reporting concentrations of compounds such as carbon disulfide and toluene which are at least one order of magnitude higher than the readings on the North UV units. Especially considering that the South fenceline is predominantly upwind of the refinery, these numbers seem not to fit.

When asked about the concentrations being reported on the South fenceline, refinery official Dale Iverson has said repeatedly that he does not believe these numbers to be accurate. This is problematic for us. Here a key Tosco official is telling us that the numbers in their own reports are unreliable, yet there is no indication in the reports themselves that there is a problem with the data.

We have spoken with the project manager for the instrument manufacturer in Canada, who insists that the concentration figures being reported by their equipment are accurate.

It is clear that Tosco needs to undertake some basic Quality Assurance measures to determine what’s going on with the UV monitors on its southern border. There are any number of basic steps they could perform to accomplish this task. As we stated in our last report, the complete lack of any type of QA plan by the refinery and it’s contractors is, in our opinion, the single largest problem with the operation of the fenceline monitoring system at this time. It is clearly unacceptable for the refinery to continue operating their monitoring system in this fashion, as it is unacceptable for the refinery managers to continue to send us reports which they believe to be in error.



TDLAS Monitors

At the present time we cannot provide any more detailed information about the operations of the TDLAS monitors than that which is provided in Tosco’s reports.
Like the UV systems, the raw spectral data which is used to determine emissions concentrations is not saved by the TDLAS monitors. Hence, no subsequent analysis of the spectra -or raw data files- is possible. With the acquisition of our new database software, we will be able to more closely examine the results of the TDLAS monitors. This should prove especially useful in comparing calculations for ammonia concentrations between the TDLAS and FTIR systems.



SEA does not have a toxicologist on-staff. Except in such cases where a reported emission concentration represents a violation of Federal, State, or local standards, WE WILL NOT BE COMMENTING on the relative risks of any reported release.

By making these reports publicly available, both those emissions figures reported by SEA, and by TOSCO, we do not wish to imply that any of these chemical emissions pose ANY HEALTH THREAT WHATSOEVER to people in the surrounding communities.

SEA member Andy Mechling, who has been retained by SEA to re-analyze the raw emissions data from Tosco’s FTIR monitors, holds no formal scientific credentials. He holds Bachelors degrees in History and Communications. He has undertaken training by the Environmental Technologies Group, the manufacturer of the FTIR instruments, and now has more than two years experience producing and analyzing this type of data for a number of community groups in a wide variety of situations. SEA has every confidence in his abilities to accurately analyze and report this data. Still, considering of our staff’s lack of scientific credentials, any chemical concentration figures reported by SEA should be regarded as our BEST ATTEMPT to arrive at the truth, rather than the ultimate truth regarding chemical emissions from the Tosco refinery.

Because of the nature of infrared spectroscopy, where the raw spectral data is saved electronically, all reported concentrations of chemical emissions are ultimately verifiable. SEA will make the raw spectra which make up our reports available upon request to any party for any reason. Furthermore, in the event that there is a discrepancy between our analytical results and those arrived at by Tosco’s FTIR contractor, SEA will make every attempt to notify the refinery, and to rectify the discrepancy BEFORE making any results publicly available.

We are undertaking this project, and making these reports public, because we believe that residents in our communities have a fundamental right to know as much as possible about the air that surrounds them. It would be much preferable to us if this task were being undertaken instead by one of the regulatory agencies, who possess infinitely better resources than our very small organization. Unfortunately, this is not the case at all, and the job is left for us to do. Simply put, we are making this data public in this fashion because we are presently the ONLY AVAILABLE SOURCE for this type of chemical emissions data.