Air Quality Monitoring

ConocoPhillips-Rodeo Oil Refinery

This website allows users to view air toxics monitoring data from optical monitors at a ConocoPhillips refinery in Rodeo, California (ConocoPhillips-Rodeo). It presents monitoring data for nine chemicals recorded at two locations: the facility's north and south fencelines. Chemical concentrations are recorded at 5-minute intervals, 24 hours a day, 7 days a week.

This project is a collaborative effort involving the refinery itself, the local county (Contra Costa County), and the U.S. Environmental Protection Agency (see the EPA's website about the project). Two local community organizations (Shoreline Environmental Alliance and Communities for a Better Environment) also have provided valuable input.

Background

ConocoPhillips-Rodeo is a large oil refinery located about 25 miles northeast of San Francisco. It is situated between the communities of Rodeo and Crockett, with a school and public housing on the south fenceline, a major freeway (I-80) to the east, and San Pablo Bay to the west.

The refinery is located on the eastern shore of San Pablo Bay. It was operated by Unocal until 1997 and by Tosco from 1997 to 2001. It is currently owned by ConocoPhillips Petroleum.

The fenceline monitoring system was installed as a result of releases, which included Catacarb (an alkaline solution), that impacted the community in 1994. For additional information, view Contra Costa County's accident history page.

These concerns led Contra Costa County to require additional air monitoring at the refinery in conjunction with the refinery's request for a land use permit. The County required the refinery to work with community members to design and install a monitoring network that could simultaneously measure and report toxic air pollutants at the refinery's fenceline.

Monitoring at ConocoPhillips-Rodeo

Most urban areas monitor six major air pollutants (ozone, particulates, sulfur dioxide, carbon monoxide, nitrogen oxides, and lead). Many facilities monitor emissions from individual smoke stacks and other units. By contrast, the remote sensing equipment at ConocoPhillips-Rodeo monitors for the presence of 30 air toxics all along the fenceline (as opposed to monitoring at individual points). The monitors can generate 600,000 data points in a year.

Monitoring equipment

The refinery has installed three types of monitors: FTIR (Fourier transform infrared), UV (ultra violet), and TDL (tunable diode laser). The monitors sit along both the north and south fencelines. Each of the monitors operates continuously, delivering data at 5-minute intervals, 24 hours a day, 7 days a week. All are "open path monitors," meaning they measure ambient air pollutants occurring over a 1,000-meter light beam path. One monitoring station also collects meteorological data, including wind direction (not currently reported on this site).

Monitoring data on this website

The nine chemicals presented on this Web site are all from the FTIR monitors. The chemicals are: ammonia, butane, carbon monoxide, carbonyl sulfide, formaldehyde, methane, methyl tert- butyl ether (MTBE), nitrous oxide, and ozone. Selection of these chemicals was based on a study and report completed under a grant from the U.S. EPA.

The UV monitors measure for BTEX compounds (benzene, ethyl-benzene, toluene, and xylene). The TDL monitors measure for ammonia and hydrogen sulfide. The measurements at the concentrations reported by the UV and TDL monitors are not sufficiently accurate that Contra Costa County is willing to report them on this Web site.

Details on monitoring with FTIR

FTIR monitors can detect, identify, and measure many different gases simultaneously. As a result, initial monitoring results are viewable at a computer in the ConocoPhillips-Rodeo refinery within seconds of the readings. To identify different gases, the monitors measure how much energy is absorbed in the infrared spectrum. Such a specific measurement of energy allows for the unique identification -- or "fingerprint" -- of each chemical molecule. The monitors also measure how much of each gas is present. The greater the absorbence, the higher the concentration in the air. At ConocoPhillips-Rodeo, the FTIR instruments continuously scan for 30 chemicals, including ammonia, benzene, ethyl benzene, 1,3, butadiene, formaldehyde, methane, and MTBE. Analysis of the raw data can reveal the presence of 300 additional chemicals. The FTIR monitors also record raw spectral files that can be reviewed later. If a chemical release occurs, it is possible to go back and look at the FTIR files to see when emissions started appearing and how long the release lasted.

Data Quality

Quality assurance and control (QA/QC) for the monitoring data that are presented on this Web site is performed by Petris Technology under a contract with ConocoPhillips. Neither Contra Costa County nor any other entity has performed any independent QA/QC of the data.

See also...