With one school already built and construction of another pending, Rio School District can now move forward and build a third 18-acre intermediate school on the site of the massive RiverPark development in Oxnard — following approval of a plan to mitigate elevated methane levels found beneath a portion of the site last year.

However, the district appears to have jumped the gun a bit, beginning construction a week before the California Department of Toxic Substances Control gave them the go-ahead.

“They had started some sewer trenching,” said Sharon Fair, branch chief of the Glendale and Sacramento branches of the school property evaluation and cleanup division of the DTSC, “which they probably should not have done until we completed the approvals.”

In January 2005, as per state requirements for schools paid for with bond money, the DTSC conducted a Preliminary Environmental Assessment of the school site, testing for a host of contaminants, including pesticides, metals such as lead and arsenic, and various gases.

The investigation revealed that methane levels in the northern part of the proposed intermediate school site were “significantly higher” than 5,000 parts per million, the point at which the DTSC evaluates a site for possible protective action, according to Javier Hinojosa, chief of the Glendale Schools Unit of the DTSC and supervisor of the RiverPark Legacy Intermediate School project.

While exposure to methane does not pose a direct health risk, at concentrations between 50,000 and 150,000 parts per million it has the potential to catch fire or explode. The gas occurs naturally in coal mines and oil fields, as well as in organic material that has been deprived of oxygen.

Although several abandoned oil wells were found on and around the school site, tests determined the source of the methane was likely from recompacted soil, meaning the methane is less concentrated than it would be if it were petroleum-based, Hinojosa said. Continued testing has shown the amount of methane decreasing notably over the last year, he added, but because of fluctuations in the levels, mitigation is still required.

In May, the DTSC issued a Draft Removal Action Workplan outlining the strategy for keeping the methane from seeping into the future buildings and reaching levels of concentration high enough to cause an explosion. The plan calls for the construction of a venting system that would “safely release the methane gas to the outside air or atmosphere and prevent gas buildup in the soil beneath and within two of the four planned buildings.” An impermeable barrier made of high-density latex would also be put in place to stop methane from entering the buildings.

“The remedy is tied to construction,” Fair said. “Usually, if we have contamination, we dig it out and haul it off the site, and that’s done prior to construction. But for methane, because the system is tied to the buildings themselves, the implementation of the response action is done at the time of construction.”

The public comment portion for the draft RAW concluded on June 13. On July 25, the plan was approved by the DTSC, with few changes made as a result of the comments, Hinojosa said. They are now prepared to implement plans for construction, he said.

But eight days prior to the approval of the RAW, the DTSC received a phone call from a citizen who observed construction already occurring on the 3.35-acre site slated for remediation, violating the district’s School Cleanup Agreement with the DTSC.

The DTSC contacted Gerry Hels, senior environmental engineer for ENSR International and the Rio School District’s environmental consultant, who confirmed that some sewer trenching had commenced on the site that had previously been fenced off. According to a letter signed by Fair and sent to the district on July 20, Hels “attempted to stop the work, but was only partially successful.” The letter goes on to request that the district “stop construction work immediately, as these activities may pose a potential safety threat.”

With the resignation of Superintendent Patrick Faverty last December and the ongoing strife amongst the board of trustees, Fair said it has been difficult to communicate with the district, but she understands construction at the school site has since halted. Since the violation happened so close to the approval of the RAW, she said no action will be taken to penalize the district.

Representatives from the Rio School District could not be reached at press time.

Hinojosa said the DTSC will continue to monitor the school site’s methane levels on a monthly, quarterly and yearly basis, depending on fluctuations in concentration levels. If the levels continue to deplete as they have, there should be significantly lower concentrations within five years. In the worst case scenario, 30 years of monitoring would be required, Hinojosa said, but added that they “don’t anticipate going that long.”