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 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.
Anticipated next steps include application of bioremediation additives to enhance natural microbial breakdown of the petroleum remaining in the soil along the creek. Soil samples will be collected before and after the application to monitor the degradation. In addition, areas with algal build-up are being attended via methods approved by the Fish and Wildlife Service.
At the VA hospital, remediation work is ongoing and will soon include a cleansing of the impacted storm drain, including the drainage outfall to the creek. This work will be closely monitored by representatives of the Unified Command.
Identified Algal Buildup Being Addressed
It has been observed that naturally occurring algae appears to be restricted from flowing downstream, and is building up at a few locations along the boom network. Algal buildup is naturally occurring in other areas of the creek where water pools up and stagnates. Because algal growth and subsequent decay can reduce the oxygen concentration in water, the remediation contractor has obtained approval from Fish and Wildlife to use pool skimming equipment to reduce the algal growth only in the areas where buildup is next to the booms.
Public Asked Not to Disturb the Creek
The Department of Fish and Wildlife asks that the public refrain from moving any material within the impacted section of the creek, as any adjustments could impact the rate and direction of water flow, which could inadvertently cause the water to come into contact with contaminated soil or direct water flow around the boom network. Furthermore, from a public health standpoint, in principle any material from the impacted portion of the creek is considered hazardous unless established to be nonhazardous by lab analysis.
There continues to be visible muskrat activity along the creek, demonstrating that the remediation efforts appear not to be interfering with wildlife. Representatives of Fish and Wildlife want to assure the public that while the algal buildup is being reduced to prevent oxygen depletion within the water, the muskrats (and other mammals) have not been impacted by the algae presence since their oxygen source is from the air above the water surface.
Ongoing Creek Monitoring
Throughout the remediation, Matadero Creek has been monitored at 16 locations for multiple chemicals related to diesel:
- Total Petroleum Hydrocarbon as Diesel (TPH-Diesel) - a measurement of the suite of hydrocarbon compounds that typically make up diesel fuel.
- Polyaromatic Hydrocarbons (PAHs) – individually measured compounds for which the Water Board has a specific water quality objective for each compound based on toxicity data.
- Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) – four compounds found in gasoline and diesel for which the Water Board also has specific water quality objectives for each compound based on toxicity data.
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-005. 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 220 water samples. As can be observed from the data tables, out of about 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.
There remains diesel residue in soil along the creek bank near the outfall. The Department of Fish and Wildlife, VA staff, and consultants evaluated options to enhance bioremediation. Anticipated next steps include additional light soil tilling and the application of bioremediation additives to enhance natural microbial breakdown of the petroleum remaining in the soil along the creek. 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 in order to maximize removal prior to a significant rain event, while minimizing disturbance of the creek bank and vegetation.
Creek Data and Map Update
As noted above, the boom areas that the team are 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 13, 2021(PDF, 471KB)