Get Full Government Meeting Transcripts, Videos, & Alerts Forever!
Get email alerts on the Air Quality topic
No spam. Unsubscribe anytime.
Consultant warns of recurring hexavalent‑chromium spikes; city to install 30‑ft met tower for source investigation
Summary
A contractor reported repeated near‑threshold readings of hexavalent chromium at one Paramount sampler and recommended installing a taller meteorological tower at the sheriff’s station by late June to gather representative wind data to support South Coast AQMD and EPA modeling.
Paramount’s environmental consultant told the City Council Tuesday that ambient air monitors in the city have registered recurring elevated concentrations of hexavalent chromium at one monitoring site, and staff recommended installing a taller meteorological tower to improve wind data for source investigation.
"In November 2021, the city of Paramount retained Trinity Consultants to take over South Coast ACMs routine hexavalent chromium monitoring," consultant Randall Baxter said, explaining the program’s sampling schedule and exceedance criteria. He summarized South Coast AQMD’s operational threshold as "above one nanograms over three consecutive sample periods," using an EPA sampling cadence of one sample every six days.
Baxter said that while the monitoring network hasn’t shown the three consecutive exceedances that would formally trigger a regional designation of exceedance, one sampler site has accumulated multiple exceedances and near‑threshold readings in the same general area, creating a pattern of concern that merits further investigation.
To improve the representativeness of local wind data for dispersion modeling, Baxter proposed installing a 30‑foot (approx. 10‑meter) meteorological tower at the roof of the sheriff’s station—north of City Hall and away from trees that can distort wind readings from the current tripod near City Hall. He said the city is aiming to install the structure by the end of June and will build the platform to EPA meteorological guidance so the data can be used for modeling.
City staff said they have been coordinating with South Coast AQMD (the regional air district) and that South Coast is continuing to review the data. The met tower would provide higher‑quality wind and stability information that is commonly used to tie exceedance events to potential sources in modeled reconstructions.
The presentation also described the monitoring network and workflow: 24‑hour filter samples collected on an EPA schedule (one in every six days), rapid lab turnaround for expedited analysis, and a public environmental portal where results are posted. Baxter said the city has replaced older pull samplers with newer equipment and that the system includes a meteorological station (temperature, humidity and wind) currently mounted on a short tripod at City Hall.
Councilmembers asked timing questions and a city manager said staff will continue to work with South Coast AQMD on the technical review of the monitoring results. No regulatory action was proposed at the meeting beyond the proposed met‑tower installation and continued coordination with the regional air district.
The council did not take a policy vote; consultants said the met tower installation is being scheduled for late June, pending logistics and resource mobilization.
