City Of Palo Alto: Matadero Creek/VA Palo Alto Health Care Diesel Spill Community Update

Press release from the City of Palo Alto:

October 21, 2021

Oct. 21, 2021 Community Update

The Fire Department continues to consider the incident at Matadero Creek to be stable. Soil remediation continues on the VA property, while regular monitoring of the creek at 16 locations indicates that Matadero Creek is largely remediated, with no observed impacts to fish or wildlife. The sampling data continue to show that the boom system is still keeping the residual contained. All work is being conducted to ensure that wildlife remain protected throughout the remediation.

The Palo Alto Fire Department remains in Unified Command, which means the Palo Alto Fire Department Hazmat Bureau is working as a cohesive unit through all phases of this incident with the VA Palo Alto Health Care System, City of Palo Alto Stormwater staff, California Department of Fish and Wildlife, the San Francisco Regional Water Board, the Santa Clara Valley Water District and third-party remediation and environmental scientist experts.

Representatives from regulatory agencies continue to meet to review all aspects of the incident, including cause of the release, continued containment of the diesel, and remediation of the soil and water. Action plans continue to evolve based on monitoring results and expert recommendations.

On Oct. 19, contaminated soil was removed at the outfall. In addition, Unified Command, the VA, and third-party contractors developed a monitoring plan for the October rains.

Soil remediation is ongoing at two locations along the creek--next to the outfall and at the creek bank near the water sampling site W-007.

In August, soil samples were collected at the outfall in tandem with the storm drain sampling. Four of 12 samples contained TPH-Diesel at concentrations above the Water Board goal of 260 mg/kg (ranging from 290 to 3,300, with an average of 1,235 mg/kg). Therefore a permit was obtained from Fish and Wildlife to remove a limited amount of soil at the outfall. The soil removal was completed on Oct. 19, along with follow-up sampling at the creek bank. Sand bags were placed on the site as a temporary measure to protect the creek bank through the winter. A long-term plan to shore up the creek bank will be presented to the Department of Fish and Wildlife for review and approval.

At the creek bank near water sampling site W-007, following approval by the Department of Fish and Wildlife, bioremediation additives were applied in late September to enhance natural microbial breakdown of the remaining petroleum. The objective is to accelerate natural processes in order to maximize removal prior to a significant rain event, while minimizing disturbance of the creek bank and vegetation. Contractors will resample the site at the end of October and compare the results with samples collected just prior to the application.

While the storm drain system and the outfall are believed to have been sufficiently remediated, the Unified Command, VA and third-party contractor met to develop a plan to minimize the release of any lingering contaminated material during the rains. The plan includes additional booms just downstream of the outfall and coordinated monitoring by VA staff and City staff.

Throughout the remediation, Matadero Creek has been monitored at 16 locations for multiple chemicals related to diesel:

Throughout the monitoring process, the primary constituent consistently detected has been TPH-diesel, rather than the individual PAH or BTEX species. Based on discussions with the Department of Fish and Wildlife, this is a positive outcome in that it is the individual PAH and BTEX compounds that would be expected to impact wildlife.

Based on the most recent analytical data, it appears that the TPH-Diesel results at all water monitoring locations are below the Water Board goal of 640 ug/L.

To date, more than 14 PAH species have been analyzed on more than 220 water samples. As can be observed from the data tables, out of more than 2,900 combined analytical results for these PAH species, only 2 PAH species had a combined total of four values greater than the Water Board’s Habitat Goal, and no such value has been observed since mid-June.

As can be observed from the data tables, while there have been more than 200 tests for BTEX, there was single finding of Xylene in early May at one location, and more recently one minor detection of toluene at another location; both were far below the Water Board’s Habitat Goal.

All data are available by downloading the latest data table.

Download: Creek Water Sampling Table 1 and 2 With Map as of October 21, 2021(PDF, 1MB)

More information will be released as details become available.

Read the initial joint community update on this issue.

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This press release was produced by the City of Palo Alto. The views expressed here are the author’s own.