Many of the homeowners had complained about issues with their cast iron sewer pipes. A number of cast iron sewer pipes removed from the ground were severely degraded and were no longer serviceable. Homeowners were spending approximately $15,000 to $20,000 to replace their sewer pipes and one homeowner reportedly spent over $40,000.
Both the City and the homeowners suspected that the crude-oil contaminated soils underlying their houses was responsible for the degraded sewer pipes. Consequently, HG Cornerstone was retained to perform an engineering assessment of conditions and a forensic study for a possible casual connection. In April 2017, HG Cornerstone initiated the first, preliminary, phase of their engineering study. This first phase was limited in scope and its main goal was evaluating whether a causal connection between the soil contamination and degraded sewer pipes was likely.
The homes within the Carousel neighborhood were built directly on top of soil that was contaminated by petroleum hydrocarbons in the form of crude oil. The 44-acre development site was previously operated by Shell as the Kast Property Tank Farm, a crude oil storage tank farm which included three massive crude oil storage reservoirs. In 1965, Shell sold the property to a developer named Barclay Hollander Curci.
In 2007, the State of California Department of Toxic Substances Control initiated an environmental investigation at the site. In 2011, the State of California Los Angeles Regional Water Quality Control Board issued a Cleanup and Abatement Order requiring that Shell clean up the site. A Remedial Action Plan (or “RAP”) was subsequently approved by the Los Angeles Regional Water Quality Control Board and Shell began implementing the cleanup work in 2016. The cleanup of the site is expected to take about a decade or so. In very general terms, the cleanup of individual properties involves excavating and removing about 5 to 10 feet of soil from around most houses. Excavation of the soil located directly beneath the house was not made part of the RAP although soil vapor extraction was included as an additional remediation option for any homeowner who requested it.
On September 14, 2017 HG Cornerstone issued its interim report for the first phase of its investigation titled “Interim Engineering Observations & Assessment Report, Forensic Cast Iron Sewer Pipe Study, Former Kast Property, Carousel Tract Residences, City of Carson, CA.” On September 19, 2017, HG Cornerstone’s interim engineer’s findings were presented to the City at its City Council meeting.
HG Cornerstone had found that, based on the first phase of its study, there is merit to the possibility that a casual connection does exist between the soil contamination and the cast iron pipe corrosion observed. Several key, theoretical pipe corrosion mechanisms associated with the soil and site conditions were identified. However, HG Cornerstone noted and recommended that further study is necessary and required to confirm these preliminary findings. In its report, HG Cornerstone also identified several imminent health hazards associated with the corroded sewer pipes beneath residents houses including potential sewer gas exposure and hazards associated with wastewater directly entering the subsurface. Based on HG Cornerstone’s report and preliminary findings, numerous issues were brought to light including the fact that many residents of the Carousel neighborhood were able to see photographs of the soil cleanup work for the first time as this work was screened from public view.
The second, more definitive, phase of the forensic study has been delayed due to lack of funding and pending discussions between the City of Carson and the Los Angeles Regional Water Quality Control Board to determine whether the removal and replacement of degraded cast iron sewer pipes by Shell can possibly be included in the RAP. This second phase is expected to begin in the early Spring of 2018.