BACKGROUND
- In 2011, a hydrocarbon sheen had been occasionally observed during low tides in the Dominguez Channel about 400 ft south of the Carson Street Bridge. In May 2011, the Los Angeles Regional Water Quality Control Board (LARWQCB) issued orders to various entities to conduct facility and channel assessments to determine the nature and source of the release. In response, Resource Environmental, LLC (RELLC), which is an independent organization formed by several major oil companies for the purpose of responding to and cleaning up releases of petroleum fuels into the soil and groundwater, was engaged to conduct a comprehensive assessment program from 2011 through 2024 at the Dominguez Channel and several properties in the immediate vicinity. RELLC also developed an Interim Remedial Action Plan to address this concern.
- It was determined that the light non-aqueous phase liquid (LNAPL) that was seeping into the channel is primarily a naphtha range material mixed with low levels of crude oil originating area from pipeline source(s). A non-aqueous liquid means it does not mix with water which is why it floats on top of water in the form of a sheen. Naphtha, commonly shipped between refineries, is one of many constituents of gasoline. This LNAPL was observed entering into channel waters from (1) sediments within the bottom of the channel and (2) horizontal, perforated sub-drain pipe systems installed within the west and east channel levees. Accordingly, RELLC enhanced the recovery operations of LNAPL in wells and subdrain manholes along the channel levees.
- Product recovery and semiannual groundwater monitoring have been conducted from 2011 to the present. Occasional and intermittent hydrocarbon sheen events on the channel have been contained with floating booms in order to isolate the sheen. When sheening was observed once in 2013 and again in March 2019, RELLC re-deployed booms from then through December 2019. When sheening was observed in April 2020, RELLC re-deployed booms from then through December 2021. The next sheening event occurred in March 2023 and RELLC re-deployed booms from then through December 2023. The most recent sheening event occurred in February 2024 and RELLC again re-deployed absorbent booms that continue to contain the hydrocarbon sheen.
ENVIRONMENTAL SITUATION AND PATH FORWARD
Through its extensive assessment work conducted from 2011 through 2024, RELLC has identified the most probable source of the LNAPL that has occasionally caused sheening. In the 1950s and 1960s, one or more of the pipelines located adjacent to the channel transferring these petroleum hydrocarbon products apparently leaked at various times and places and in various quantities. At the time, the regional underground aquifers, including the near surface aquifer, were very deep due to over pumping of the aquifers. The leaks from the pipelines weren’t then apparent and no one knew that leaks had occurred. However, since the early 1970s, the water table on which hydrocarbons naturally float, has risen over 100 feet due to clean water being injected into the aquifers for the Dominguez Gap Barrier project to prevent seawater intrusion. Only recently have the aquifers risen (thereby raising the level of the floating hydrocarbons) to the point where the groundwater elevation is higher than the clay bottom of Dominguez Channel. As a result, it finally became apparent that there had been historical leaks of petroleum hydrocarbons from the old, abandoned pipelines. In other words, the channel has been a gathering water body so that water from the aquifer pushes up into the bottom of the channel resulting in an observable surface sheen on the channel.
The only permanent solution is to extract the residual LNAPL contaminants from under the channel bottom and remove areas of the clay channel bottom. This would best be done in conjunction with the future plans of Los Angeles County to widen and deepen the channel. For now, RELLC has minimized impacts by removing LNAPL from the subsurface using recovery wells in order to reduce pressure beneath the channel bottom and to reduce sheening.
Under the purview of the LARWQCB, investigations and evaluations have indicated that there are no human health issues presented by this channel condition. In addition to the evaluation within the channel, all areas adjacent to the channel have been adequately assessed for any impacts from these historic pipeline leaks. There is evidence of impacted soils in several industrial areas and beneath the streets which were the corridors on these old pipelines, but these minimal impacts present no health concerns based on current activity and use. However, out of an abundance of caution, in 2024, RELLC will be conducting additional assessment at residential boundaries which are east of pipeline corridors where historic leaks may have occurred and in certain residential areas just to the east of the boundaries (that is, east of the former Active RV site).
CONCLUSIONS
The problem of sheening on the channel is most likely from historic pipeline leaks and there have been no known such leaks from these pipelines for several decades. We don’t know and cannot determine the exact pipeline source or precise times or locations of the old pipeline leaks that have now impacted the channel. Eventually, the bottom of the channel will have to be dug up and restored to permanently solve the problem. To minimize disruption in the community with the required construction activities, this work will be best completed in coordination with the future general widening/deepening of the channel by the Corps of Engineers and the Los Angeles County Department of Public Works. The timing of the channel widening and/or deepening is not known but this activity is not likely to happen in the near future. Until then, RELLC will remain diligent with its ongoing remedial and monitoring activities.
All testing results continue to be reported on a regular basis by RELLC to the LARWQCB. In addition, RELLC will continue to communicate with the City of Carson to ensure that City and community leaders are fully informed about this environmental assessment.
For more information about RELLC, please go to www.rellc.net.
TIMELINE & STATUS Environmental assessment activities are continuing until all necessary evaluations are completed. All activities are performed Monday through Friday, from 7:00 a.m. until 5:00 p.m., as approved by the LARWQCB.
CONTACT INFORMATION
If you would like additional information about the environmental assessment, please contact:
Los Angeles Regional Water Quality Control Board
Majd Nima, Project Manager
320 West Fourth Street, Suite 200
Los Angeles, CA 90013
213-576-6707
City of Carson
Christopher Palmer, Planning Manager
701 East Carson Street
Carson, CA 90745
310-952-1761
RELLC
310-857-2334 (Local)
800-461-9960 (Toll Free)
SITE SPECIFIC DETAILS
Channel and Levees:
- Installed groundwater monitoring wells (2011-2017; 2023); conducting groundwater sampling that confirms that contaminant concentrations and areas of contamination are stable or decreasing (2011-2024)
- Conducted soil sampling at the channel and along levees to identify contamination (2011-2017; 2023); identified specific areas with LNAPL; pumping out LNAPL that might otherwise get into channel (2011-2024)
- Conducted studies that showed that pressure from rising groundwater levels sometimes forces some contaminants up from the base of the channel into the water, which occasionally causes a sheen (2015 – 2024)
- Deploying absorbent booms on the channel (as needed) to contain and remove sheen (2011-2013, 2019-2021; 2023; 2024)
- Removing LNAPL from levee subdrain system to prevent it from getting into channel (2011-2024)
Former Active RV Property (1202 East Carson Street):
- Conducted soil and soil vapor sampling (2011-2012; 2023; ongoing in 2024)
- Soil vapor sampling and sub-slab soil vapor sampling is being conducted in 2024 to determine if there are any soil vapor concerns at the eastern boundaries adjacent to the residential neighborhood.
- Evaluation of impacted soils near and under commercial building on-site was conducted. Long-term restrictions likely needed with a deed restriction to limit future property for commercial use.
- Installed groundwater monitoring wells (2011-2012); conducting groundwater sampling that confirms that contaminant concentrations and areas of contamination are stable or decreasing (2011-2024)
Neighborhood Adjacent to Active RV (Ashmill Street, Cloverbrook Street):
- Installed groundwater monitoring wells (2014; 2023); conducting groundwater sampling (2014-2024)
- Sub-slab soil vapor sampling will be conducted just to the east of the former Active RV site in 2024 to determine if there are any soil vapor concerns in the residential area just to the east of the boundaries.
Former Carson Air Harbor Facility (21611 Perry Street);
- The LARWQCB identified this site as a potential source of contamination to the Dominquez Channel
- However, 2011 investigations showed the site was not a source of contamination to Dominquez Channel
76 Station #6082 (1025 East Carson Street):
- The LARWQCB identified this site as a potential source of contamination to the Dominquez Channel
- However, 2011 investigations showed the site was not a source of contamination to Dominquez Channel
Former Texaco Station (1209 East Carson Street):
- The LARWQCB identified this site as a potential source of contamination to the Dominquez Channel
- However, 2011 investigations showed the site was not a source of contamination to the Dominquez Channel, and the LARWQCB granted environmental case closure for this site in 2015