BACKGROUND
In 2011, a hydrocarbon sheen had been observed occasionally during low tides in the Dominguez Channel about 400 ft south of the Carson Street Bridge. In May 2011, the Regional Water Quality Control Board – Los Angeles Region (LARWQCB) issued orders to conduct facility and channel assessment 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, conducted a comprehensive assessment program from 2011 through 2017 at the Dominguez Channel and several properties in the immediate vicinity and developed an Interim Corrective Action Plan. It was determined that the light non-aqueous phase liquid (LNAPL) seeping into the channel is primarily a naphtha range material mixed with low levels of crude oil originating from pipeline source(s). Naphtha, commonly shipped between refineries, is a component of gasoline. 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. Since 2011, any occasional sheen on the channel has been contained with booms. It was not necessary to deploy booms on Dominguez Channel from November 2012 through February 2019, because no sheening had been observed with one exception in July 2013. However, when hydrocarbon sheening was observed in March 2019, RELLC re-deployed booms through December 2019, at which time no further sheening was observable. When hydrocarbon sheening was again observed in April 2020, RELLC re-deployed booms through December 2021, at which time no further sheening was observable. When hydrocarbon sheening was again observed in March 2023, RELLC re-deployed booms through December 2023, at which time no further sheening was observable. When hydrocarbon sheening was again observed in February 2024, RELLC once 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 likely leaked at various times and in various quantities. At the time, the regional aquifers, including the near surface aquifer, were very deep, due to over pumping of the aquifers. At that time, the leaks from the pipelines weren’t 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. It has only been recently that the aquifers have 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 is a gathering water body, so 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 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 of these old pipelines. However, these limited impacts exhibit no health concerns based on current activity and use. 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 likely occurred and in 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 leaks from these pipelines for several decades. We don’t know and cannot determine the exact pipeline source or precise location of the old pipeline leaks that impacted the channel. Eventually, the bottom of the channel will have to be dug up to solve the problem. To minimize disruption in the community with the required construction activities, this work will be best completed in coordination with possible general widening/deepening of the channel with 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 next few years. Until then, RELLC will remain diligent with its ongoing remedial 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); conducting groundwater sampling that confirms that contaminant concentrations and areas of contamination are stable or decreasing (2011-2023)
- Conducted soil sampling at the channel and along levees to identify contamination (2011-2017); identified specific areas with LNAPL; pumping out LNAPL that might otherwise get into channel (2011-2023)
- 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 – 2023)
- Deploying absorbent booms on the channel (as needed) to contain and remove sheen (2011-2013, 2019-2021; 2023)
- Removing LNAPL from levee subdrain system to prevent it from getting into channel (2011-2023)
Former Active RV Property (1202 East Carson Street):
- Conducted soil and soil vapor sampling (2011-2012)
- Investigation on east side of site showed there are no known impacted soils and no potential vapor intrusion concerns at the eastern boundaries adjacent to the residential neighborhood
- Evaluation of impacted soils near and under commercial building on-site pose no vapor concerns to current property commercial use. 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 (2011-2023)
Neighborhood Adjacent to Active RV (Ashmill Street, Cloverbrook Street):
- Installed groundwater monitoring wells (2014); conducting groundwater sampling that shows that very few contaminants are detected, and concentrations of any detected contaminants are very low (2014-2023)
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