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

Press release from the City of Palo Alto:

August 03, 2021

August 3, 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 continuing to keep 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 3rd 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.

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

Throughout the monitoring, the primary constituent consistently detected has been that of the overall measurement of 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.

The analysis continues to show periodic TPH-Diesel sample results outside of normal limits between W-008 and W-006 as well as occasionally just downstream at W-004. Third party experts suggest this may be due to limited sunlight exposure, a higher density of plants, and a natural in-creek obstruction to water flow. This combination of conditions may have trapped small portions of the initial spill. Therefore limited treatment was initiated at this single location. Meanwhile, according to Fish and Wildlife staff, these TPH-diesel values, while higher than the Water Board goal of 640 ug/L, are not the typical indicator of possible impact to wildlife. Rather, it is the more specific compounds within diesel, that of PAH and BTEX, that are of greater concern from a habitat perspective.

In mid-July, sites W-012 and W-013 observed an uptick in TPH, with analytical values greater than had been seen at either site since May 11. Because this particular lab analysis can pick up organic material other than TPH, including natural organics (e.g., humus) and petroleum decomposition products, the analysis of both samples is being repeated using a process that first removes non-TPH hydrocarbons. The results (pending) will be compared with the original results. In addition, these sites will continue to be monitored to ensure that the values return to below the Water Board goal.

To date, more than 14 PAH species have been analyzed on more than 200 water samples. As can be observed from the data tables, out of about 2,900 combined analytical results for these PAH species, only 2 PAH species had a combined total of 4 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, only a single finding of Xylene in early May at one location has ever been detected at the site, and it was far below the Water Board’s Habitat Goal.

A concerned resident and animal advocacy group met with the Fire Department’s Hazmat staff and VA staff to point out the location of a possible muskrat den along the creek and discuss how to ensure that remediation efforts not disturb the den. The resident has since reported seeing continued muskrat activity, demonstrating that the remediation efforts appear not to be interfering with wildlife.

Earlier in July there were efforts to mobilize diesel product remaining on the water surface and direct it to the downstream booms. The work to mobilize diesel product is no longer underway based on visual observations that the effort appeared to have had the desired effect.

There remains diesel residue in soil along the creek bank near the outfall. The Department of Fish and Wildlife, VA staff, and consultants are evaluating options to enhance bioremediation through additional hand tilling and/or biotreatment additives. The shared objective is to develop a strategy to accelerate natural processes in order to maximize removal prior to a significant rain event while minimizing disturbance of the creek bank and vegetation.

The boom areas that the team is closely monitoring are between W-006 and W-008 on the map and only due to the TPH-Diesel values. All data are available by downloading the latest data table.

Download: Creek Water Sampling Table 1 and 2 With Map - August 3, 2021(PDF, 889KB)

Additional Sampling Data

• Water Quality Data Summary - As of June 15, 2021(PDF, 677KB)
• Water Quality Data Summary - As of May 28, 2021(PDF, 162KB)

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.