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

Press release from the City of Palo Alto:

August 27, 2021

August 27, 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.

The storm drain system and drainage outfall to the creek have been cleansed by the contractor team; samples from the cleaned drainage network have been collected and will be analyzed to ensure the completeness of that work. The next remediation step is the application of bioremediation additives to enhance natural microbial breakdown of the petroleum remaining in the soil along the creek. Contractor work and neighboring wildlife activity continue to be closely monitored by representatives of the Unified Command.

Per the last public update, concerned members of the public had previously reported observing algal buildup along the boom network. Because algal growth and subsequent decay can reduce the oxygen concentration in water, the remediation contractor obtained approval from Fish and Wildlife to reduce the algal growth in the areas where buildup was next to the booms. Upon closer evaluation of the collected material, it was discovered to be free-floating aquatic plants. While that eliminates any concern about reduced oxygen in the water, if more organic material is observed to be restricting flow through the boom network, the contractor may remove it using the method previously approved by Fish and Wildlife.

Diesel residue remains in discrete soil sections along the creek bank. Beginning in early September, bioremediation additives are expected to be applied to the soil surface to enhance natural microbial breakdown of the remaining petroleum. Because the additives include very fine particles that are considered respiratory irritants, the contractors applying the material will be wearing personal protective equipment (PPE). Therefore, the public should not be alarmed if they notice workers equipped with PPE down in the creek bed.

The material being applied has been approved by the Department of Fish and Wildlife. Soil samples will be collected and analyzed before and after the application to monitor the biodegradation process. The project objective is to accelerate natural processes to maximize removal prior to a significant rain event, while minimizing disturbance of the creek bank and vegetation.

The Department of Fish and Wildlife reminds the public to continue to refrain from moving any material within the impacted section of the creek, as any adjustments could impact the rate and direction of water flow. This could inadvertently either cause the water to come into contact with contaminated soil or direct water flow around the boom network.

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 above Water Board goals at W-007, due to a combination of naturally existing conditions that appear to have trapped small portions of the initial spill; therefore limited treatment continues at this 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 showed 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 was repeated using a process that first removes non-TPH hydrocarbons. The lab results have since indicated “diesel range compounds detected, no recognizable pattern” suggesting that these samples did contain diesel residual. Meanwhile, these sites have continued to be monitored and the values are once again below the Water Board goal.

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 two 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.

As noted above, 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 below.

Download: Creek Water Sampling Table 1 and 2 With Map as of August 27, 2021(PDF, 962KB)

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.