Shirley Thomas has owned a five-unit apartment complex on Pismo Street in downtown San Luis Obispo for more than 40 years.
Until recently, she didn’t know that an oil pipeline runs beneath Pismo Street near her property. She also didn’t know that at some point in the past — likely 50 years ago — it leaked hydrocarbons into the surrounding soil and groundwater.
“There was never a disclosure of the pipeline,” Thomas said. “I can’t imagine something like this running through the center of town and people aren’t aware of it.”
She was recently notified by Stantec, a consulting company based in Minnesota hired by Union Oil Co., that the site was being monitored for possible remediation. The company requested that Thomas allow it to install a groundwater monitoring well on the property.
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She has so far refused.
“I really don’t want them coming onto the property,” said Thomas, adding that it would be disruptive to her tenants.
Alison Jones, an environmental scientist with the Central Coast Regional Water Quality Control Board, is overseeing the project. Jones said the contamination is not considered a health risk and does not pose a threat because it has only been found in the shallowest groundwater and no wells are in the area.
“It is not in the city’s water supply,” Jones said. Monitoring wells have already been installed nearby, but the additional wells are needed to make sure that the contamination hasn’t spread, Jones said.
“It is not real volatile,” she said. “The plume is pretty localized. It doesn’t seem to be going anywhere. We are just trying to get a better idea of the extent of it.”
The 24-foot-deep pipe, which could date back to 1910, runs from the Central Valley to Avila Beach. It was replaced in the 1990s with a newer pipeline, which includes a monitoring system to detect leaks. The old decommissioned pipe was cleaned out and left in place.
The site is one of approximately 24 active pipeline cleanup sites in San Luis Obispo County. Those sites are ranked by priority from low to high based on their risk to human health and the environment. The site under Thomas’ property is ranked a low priority.
The higher and medium priority cases include: the Avila Tank Farm, owned by Chevron, in Avila Beach; a pipeline at Tassajara Creek, also owned by Chevron, on the east bank of Santa Margarita Creek; and the Nipomo Creek Pipeline, owned by ConocoPhillips, in Nipomo. The majority of the remaining cases are considered low priority.
“It is fairly common to have sites around the county where leaks are found,” Jones said. “A lot of them are old and not really a threat. We find them and investigate them, and sometimes remediation is required.”