Category Archives: Center for Biological Diversity

Suisun Marsh gas drilling plan runs into environmental buzz saw

SOLANO COUNTY, CALIFORNIA – APRIL 7: Suisun Marsh as seen from Solano County, Calif., on Wednesday, April 7, 2021.There is a proposal to drill into the Suisun Marsh for fossil fuels. (Nhat V. Meyer/Bay Area News Group)
SOLANO COUNTY, CALIFORNIA – APRIL 7: Suisun Marsh as seen from Solano County, Calif., on Wednesday, April 7, 2021. There is a proposal to drill into the Suisun Marsh for fossil fuels. (Nhat V. Meyer/Bay Area News Group)
East Bay Times, by Shomik Mukherjee, April 12, 2021

The Suisun Marsh — known as the largest swath of contiguous wetlands on the West Coast and a haven for thousands of migrating waterfowl — has become the Bay Area’s latest battleground between fossil fuel producers and environmentalists hellbent on fighting climate change.

A Brentwood company, Sunset Exploration Inc., announced in January it wants to explore for natural gas by drilling a section of the 116,000-acre marshland about 9 miles southwest of Suisun City in an area known as Hunter’s Point, according to the U.S. Army Corps of Engineers.

Sunset proposes to construct a gravel drilling pad almost an acre large and drop a volleyball-sized drill bit about a half-mile into the sandstone ground, probing to see if there’s enough gas worth extracting. This first-phase process would last several weeks.

If the well yields enough natural gas, Sunset next plans to build a pipeline from the drilling pad to send the gas to an existing pipeline about a mile and a half away, There, the gas would be tapped to serve about 30,000 homes in the surrounding region for up to 10 years.

Because Sunset already has mineral rights to more than 4,400 acres in the Suisun Marsh, it can technically drill without a permit. But it won’t be able to if the Army Corps determines the well and pipeline would harm the environment.

A coalition of environmental groups, including San Francisco Baykeeper and Center for Biological Diversity, has already taken a stand against the project and wrote a Feb. 26 letter urging the Army Corps to reject Sunset’s request for a permit.

They contend the drilling operation would contribute to climate change because combusting natural gas to produce energy releases carbon emissions. Plus there’s the added risk of gas leaks.

In addition, opponents contend the project would threaten hundreds of bird, fish, mammal and reptilian species that thrive in the marsh, as well as sensitive plants such as the Suisun thistle that doesn’t grow anywhere else on Earth.

So swift and fierce was their response that Sunset is contemplating a retreat.

“It may not be worth the fight,” Bob Nunn, president of Sunset Exploration, said in a recent interview.

Joining the chorus against the project is the state Department of Justice’s Office of the Attorney General, which sent its own letter recently telling the Army Corps that it’s concerned drilling would disrupt natural habitats and produce more carbon emissions at a time when the state is attempting to tamp down its fossil fuel production.

“The proposed fill and drilling in areas of Suisun Marsh could harm unique and irreplaceable habitat for endangered California Ridgway’s rail and salt marsh harvest mouse, numerous migratory bird species, listed fish species, and the very rare Suisun thistle,” the attorney general’s office wrote.

Asked why a state law enforcement agency would weigh in on a drilling project, the office replied in an email, “We’ll let the letter speak for itself.”

Even if the Army Corps signs off on the drilling plans, Sunset Exploration would need to get the OK of other federal and state environmental regulatory agencies, such as the California Department of Fish and Wildlife and the California Regional Water Quality Control Board.

If approved, Sunset’s wouldn’t be the only natural gas well at Suisun Marsh. Several other active gas wells operate there, their locations shown on an online map created by the California Geological Energy Management Division. About a dozen other gas wells have been plugged and are no longer active for various reasons. Nunn said these wells are similar in size to what he proposes to build.

“We were surprised at the level of opposition,” Sahrye Cohen, a regulatory chief at the Army Corps who will review the permit application, said in an interview. “I think it’s an indication of the times. People don’t want fossil fuels in California.”

SOLANO COUNTY, CALIFORNIA – APRIL 7: Suisun Marsh as seen from Solano County, Calif., on Wednesday, April 7, 2021. There is a proposal to drill into the Suisun Marsh for fossil fuels. (Nhat V. Meyer/Bay Area News Group)

Sunset’s Nunn acknowledged his company is pondering whether the costs of an extended review process are justified given the stiff resistance.

“The environmental community likes to thrust longer and longer delays on the smaller projects, until eventually the project becomes unrealistic and the operator says, ‘To hell with it,’” Nunn said.

While natural gas is cleaner than oil, producing less greenhouse gas emissions when it combusts, it still is a fossil fuel — and California’s goal is to reduce its emissions by 40% before 2030, an ambitious plan that involves transitioning to fully renewable energy sources.

Nunn called critics of oil and gas drilling hypocritical for participating in a carbon-fueled society and argued that shipping oil to California from elsewhere emits more carbon than would his local drilling project.

San Francisco Baykeeper’s executive director described Nunn’s comments as “nonsense,” saying there’s no tolerance in the Bay Area for “dinosaur oil companies” amid a transition to cleaner energy sources.

“Any time there’s drilling in the vicinity of wetlands, you need to evaluate thoroughly the environmental impacts of that drilling,” Sejal Choksi-Chugh said in an interview. “The Bay is no place for oil and gas drilling — the fact that (the company) is reconsidering is a big step and we’re pleased to hear that.”

Jacob Klein, an organizer with the Sierra Club’s Redwood Chapter, described Nunn’s justification for drilling locally and extracting natural gas instead of oil as “common talking points” that ignore the bigger picture.

“Rather than make comparisons between petroleum-based energy sources, we just need to be leaving (natural gas) in the ground,” Klein said.

Project opponents also point to the immediate environmental damage that drilling can wreak. A pipeline operated by energy company Kinder Morgan burst in 2004, spilling more than 120,000 gallons of oil into the marsh and killing numerous species.

Sunset Exploration acquired an existing Solano County permit and 4,400 acres of mineral rights for Hunter’s Point in 2018 after previous holder Venoco went bankrupt as it was seeking to obtain a drilling permit from the Army Corps.

Sunset was hoping to finish the job, though the opposition is now giving it second thoughts.

“They’re singling me out,” Nunn said. “If this gets drawn out for months and years, the real loser will be the environment.”

Environmental Groups Oppose U.S. Army Corps Plan to Dredge the Bay for Bigger Oil Tankers

BayNature.org, by David Loeb, April 16, 2020
The Phillips 66 San Francisco Refinery in Rodeo. (Photo By Dreamyshade, Wikimedia CC BY-SA 4.0)

Drive east along Interstate 80, past the Phillips 66 refinery in Rodeo, and you can see that the Bay Area remains very much embedded in the fossil fuel economy. And if the U.S. Army Corps of Engineers has its way, we may well be doubling down on that relationship.

The Corps has a pending proposal, officially dubbed the “San Francisco Bay to Stockton, California Navigation Study,” to dredge a 13-mile stretch of the San Francisco Bay Estuary from San Pablo Bay (just north of Point San Pablo) through the Carquinez Strait to the Benicia-Martinez Bridge. This project would deepen the channel leading to four oil refineries along the shoreline by an average of three feet, allowing for the arrival of a larger class of oil tankers than can currently access these refineries. The Army Corps’ January 2020 Environment Impact Statement (EIS) for the project claims that the total volume of oil shipped will not necessarily increase as a result of the project, but rather claims that the dredging might even result in reduced ship traffic in the Bay by delivering the same amount of oil on fewer (but larger) ships.

A map of a proposed new San Francisco Bay dredge from the Army Corps of Engineers’ January 2020 environmental impact statement.

This argument has not persuaded Bay Area environmental groups, who last spring submitted comments on the Draft EIS opposing the dredging project. These groups, including San Francisco Baykeeper, Sierra Club, Center for Biological Diversity, Friends of the Earth, Communities for a Better Environment, and Ocean Conservation Research, are submitting similarly negative comments on the Final EIS, which they say is not much of an improvement over the 2019 draft version. The deadline for public comments has been extended, due to the Covid-19 pandemic, until Tuesday, April 21.

The concerns of these organizations fall in to three basic categories: direct impacts on the local aquatic environment from both the dredging itself and from the increased traffic; direct air quality impacts on local communities from the increase in refinery operations; and above all, concern that increasing the capacity for delivery and production of fossil fuels directly contradicts the state’s mandated goal of reducing greenhouse gas emissions to slow the impact of climate change.

I. Impacts on Local Aquatic Environment

The Army Corps’ EIS contends that the Bay floor sediments to be disturbed by the dredging do not contain significant levels of toxic materials. But comments by the environmental organizations point out that the Corps appears to be relying on studies done over a decade ago or more, and they list a range of contaminants that could be re-suspended from the settled sediment that are not addressed by the Corps. The groups point out that this narrow body of water connecting the Bay with the Delta is heavily used by endangered fish species, including Delta smelt, longfin smelt, and Chinook salmon, among others, as well as by harbor seals and California sea lion, both protected marine mammal species.

The groups also point out that the EIS only addresses the impact of the dredging itself on the local aquatic environment. By asserting that the deepening of the channel will not, on its own, increase the level of shipping in the channel, the Corps disclaims any responsibility to address the impact of increased oil tanker traffic. However, as the environmental organizations point out, there is little chance that the refineries would not take advantage of this opportunity to increase their operations. In fact, as Ocean Conservation Research points out in its comments, the Phillips 66 refinery in Rodeo has recently been granted permission by the Bay Area Air Quality Management District to double its refining capacity. So it would be naïve to ignore the probability of increased traffic in the Strait, with is attendant increase in disturbance of all kinds (noise, water pollution, possible spills, etc.) and the resulting impact on wildlife populations.

In addition, Ocean Conservation Research’s comment letter points out that in order to accommodate the larger ships of the Panamax class (so-called because they are the maximum size allowed through the Panama Canal), the Phillips refinery has proposed an enlargement and expansion of its wharf facility. Such a project would involve disturbance of sediments full of toxic heavy metals left behind by the Selby Slag, a company that operated a smelter there into the 1970s, extracting ore from waste metals. Because the wharf expansion is considered a separate project, the Corps is not legally required to address it in its EIS — but expansion of the wharf would not be economically viable without the deeper channel.

Additionally, according to Baykeeper Executive Director Sejal Choksi-Chugh, “Baykeeper has concerns about how the project will impact salinity in the Delta. Deepening the shipping channel will push the fresh water/salt water mixing zone (known as the X2) further east, threatening drinking water supplies” for people in Contra Costa County and other Delta communities.

II. Impacts on Local Communities

Again, by asserting that the dredging project will not result in increased refining activity, and therefore only considering the impact of the actual dredging work, the Corps’ EIS does not find any impact on surrounding “environmental justice communities.” These communities, including Richmond, Vallejo, and Martinez, have been subjected to high levels of pollution from decades of industrial activity, and are demographically “majority minority” and low income. The failure of the EIS to contemplate increased levels of air pollution from increased refinery activities belies the refineries’ long record of “accidental” spills, flares, releases, etc. that have caused the area’s residents to periodically “shelter in place” long before the novel coronavirus.

III. The Big Picture

All of these local negative impacts are bad enough. But in their comments, the environmental groups assert that it is essential to step back and look at the much larger picture of what the dredging project implies for the region, the state, and the planet:

“The proposed channel alterations would remove constraints on expanding fossil fuel import and export volumes … The project will likely result in a significant increase in future volumes of crude oil and refined petroleum products shipped through the Bay … Here, the increased volume of oil and coal passing through the deepened channels will lead to greater refining and export activity. These in turn will lead to more greenhouse gas emissions, both at the refineries and when the products are combusted. Stated differently, the dredging is ‘a mere step in furtherance of many other steps in the overall development’ of the area’s fossil fuel industry.”

The environmental groups believe that the ultimate plan of the oil companies is to have the Bay Area’s refineries serve as an outlet for oil extracted from the Alberta tar sands, one of the most carbon intensive fuel sources on the planet, given the energy that must be invested to extract it, liquefy it for transport, and ship it. Moreover, the transport of this oil from its source in northern Alberta to the Bay Area is highly problematic, both politically and environmentally. It involves expansion of the controversial Trans Mountain pipeline over First Nation lands of the Salish people in Canada (a project that they are resisting both in the courts and on their land). Then the unrefined oil must be transported by tankers through the Salish Sea, threatening the already depleted Southern Resident population of killer whales. And finally, the tankers must pass through the Golden Gate, where recovering populations of humpback whales and gray whales are also facing increased threats from ship strikes in this busy shipping channel.

All of this leads to the final question of why U.S. taxpayers should fund (at an estimated initial cost of $57 million) a project whose main intended beneficiaries are privately owned oil refineries. Of course, direct taxpayer subsidies to the fossil fuel industry are nothing new, but in an era when we climate change requires us to be reducing our dependence on carbon-intensive fossil fuels, this project would appear to be moving us in the opposite direction.


About the Author

David Loeb
From 2001-2017, David Loeb served as editor and then publisher of Bay Nature magazine, and executive director of the nonprofit Bay Nature Institute. A Bay Area resident since 1973, David moved here after graduating from college in Boston. The decision was largely based on a week spent visiting friends in San Francisco the previous January, which had included a memorable day at Point Reyes National Seashore. In the late 1990s, after many years working for the Guatemala News and Information Bureau in Oakland, David had the opportunity to spend more time hiking and exploring the parks and open spaces of the Bay Area. Increasingly curious about what he was seeing, he began reading natural history books, attending naturalist-led hikes and natural history courses and lectures, and volunteering for several local conservation organizations.
This was rewarding, but he began to feel that the rich natural diversity of the Bay Area deserved a special venue and a dedicated voice for the whole region, to supplement the many publications devoted to one particular place or issue. That’s when the germ of Bay Nature magazine began to take shape. In February 1997, David contacted Malcolm Margolin, publisher of Heyday Books and News from Native California, with the idea of a magazine focused on nature in the Bay Area, and was delighted with Malcolm’s enthusiastic response. Over the course of many discussions with Malcolm, publishing professionals, potential funders, and local conservation and advocacy groups, the magazine gradually took shape and was launched in January 2001. It is still going strong, with a wider base of support than ever.
Now retired, David contributes to his Bay Nature column “Field Reports.”

Dredging the Carquinez to Accommodate Oil

[BenIndy Editor: Please come to the Pinole Public library on Nov. 13 at 6pm to protest the plan to increase dredging in the Bay.  More info and sign a petition at Sunflower Alliance.  If you can’t make it, download a comment form – or comment by email to SFBaytoStockton.PA@usace.army.mil.  – RS]

The Army Corps is deepening shipping channels to allow tankers access. The agency says it will clear the air. Environmentalists don’t agree.

The East Bay Express, by Jean Tepperman, Sept 11, 2019
The dredging will deepen a 13-mile stretch from San Pablo Bay to the four refineries along the Carquinez Strait. PHOTO COURTESY USGS

The federal government is preparing to deepen the shipping channels that serve four of the Bay Area’s five oil refineries. Because the channels are too shallow to accommodate fully loaded modern oil tankers, those ships travel to and from refineries only partly loaded, and sometimes wait for high tides before sailing. By reducing the number and duration of those trips, the project is likely to reduce diesel emissions affecting the already-polluted refinery communities along the Carquinez Strait. But environmentalists view it as a move to subsidize and expand oil production at a time when the future depends on ending the use of fossil fuels. And they predict it will actually increase air pollution by enabling an expansion of refinery production.

The U.S. Army Corps of Engineers is gearing up to start the project, first authorized by Congress in 1965 and funded in 2012. The Army Corps currently maintains a 35-foot-deep shipping channel down the middle of the strait. The plan is to deepen it to 37 or 38 feet along a 13-mile stretch from the Bay to the refineries, three of which lie in northern Contra Costa County and one across the strait in Benicia.

That the project will primarily benefit the oil industry is not disputed. “The channels in the study area primarily serve crude oil imports and refined product exports to and from several oil refineries and two non-petroleum industries,” according to the Environment Impact Statement issued by the Army Corps in April. “Petroleum is the big economic driver” of the project, agreed project contact person Stu Townsley. Indeed, the Western States Petroleum Association is one partner in the project.

The Army Corps says deepening the channels will save between $7.6 and $11.3 million a year in shipping costs, savings that could be passed on to consumers. A comment letter on the project from the Center for Biological Diversity, Communities for a Better Environment, the Sierra Club, and other environmental organizations says, “In essence, the public is subsidizing the oil industry to ensure greater profit for private corporations.”

However, the Army Corps also argues that the project will provide environmental benefits. Agency economist Caitlin Bryant said her forecast predicts that the same volume of oil will be shipped with or without the project. If the ships involved are fully loaded, it will take fewer vessel trips to handle the same amount of oil, and tankers no longer will have to idle offshore waiting for high tide. Fewer trips and less idling time will mean less diesel pollution.

The project will mainly benefit shipping in a type of vessel called a Panamax. The Army Corps predicts that as the volume of petroleum shipping increases, the number of Panamax “ship calls per year” will increase. But by dredging, they can reduce the size of the increase. The Army Corps projects that the project will result in about 11 percent fewer Panamax trips in the Carquinez Strait in 2023, the first year the project will be completed, 10 percent fewer in 2030, and about 8 percent fewer in 2040, with corresponding decreases in the level of air pollution they contribute to the already-high levels of pollution in refinery communities.

But environmentalists worry that the project will enable greater volumes of oil imports and exports by “debottlenecking” shipping. The environmental groups challenged Bryant’s forecast in their letter. They pointed out that Richmond’s Chevron refinery, the only one now able to handle fully loaded tankers, is operating at 99.7 percent of capacity, while the other refineries operate at only 91.3 percent. Removing the shipping bottleneck would make it easy for the other refineries to step up production, the groups claim. And they argue that increasing oil production will not only worsen climate change but increase local air pollution, outweighing the benefits of reducing the number of tanker trips.

Critics see the project as part of a larger trend to increase oil shipping and refining in the Bay Area. “The refineries are importing more oil to make products for export, polluting all the way,” said Greg Karras of Communities for a Better Environment. Exports from Bay Area oil refineries “have increased in lockstep with the decrease in domestic oil demand,” as refineries seek new markets. The Bay Area, Karras said, is becoming “the gas station of the Pacific Rim.”

Sunflower Alliance, along with Stand.earth, the Rodeo Citizens Association, the Interfaith Council of Contra Costa County, Idle No More SF Bay, Communities for a Better Environment, and Crockett Rodeo United to Defend the Environment (CRUDE), have launched a petition campaign against the dredging project. They had already joined together as the Protect the Bay Coalition to fight a proposal by Phillips 66, to increase the amount of oil shipped to and from its Rodeo refinery. “It’s troubling that this project, stalled since 1965, is going forward just after P66 requested a permit to triple oil tanker deliveries to its wharf,” said Shoshana Wechsler of the Sunflower Alliance. “Is the Army Corps of Engineers trying to facilitate increased tar sands refining at P66?”

Because it’s likely that future imports will increasingly come from tar sands, oil spills, which inevitably occur, would be more destructive. Tar sands crude oil is so heavy that it sinks when spilled in a body of water. Unlike lighter oil, it can’t be cleaned up by conventional “skimming” methods and remains on the bottom, leaching toxic chemicals. The amount of tar sands crude oil traveling to the west coast of Canada is expected to triple soon. Owners of the planned Trans Mountain Pipeline just announced they’re about to re-start construction on the project, after delays caused by protests from indigenous tribes and environmental organizations. When the tar sands crude arrives at the coast, it will be shipped to refineries in the United States — including California — as well as to Asia. Bay Area refineries have already been gearing up to process this heavier, dirtier crude oil.

Community groups also worry about harm the project could cause to the local marine environment. Even with no increase in the volume of oil shipped, the Army Corps predicts an increase in the use of larger ships. Environmentalists say larger ships go faster, which increases noise in the underwater environment as well as the likelihood of “ship strikes” on marine mammals. An increase in shipping would amplify those problems.

Environmental groups also charge that the Environmental Impact Statement underestimates the harm that would be caused by the dredging itself — both from the initial channel project and the subsequent annual maintenance that will be required. An earlier report from the Army Corps acknowledged that current ship traffic and maintenance dredging already stress the endangered Delta smelt. Noise associated with the dredging would also stress sturgeon, salmon and trout, and marine mammals.

The stirred-up sediment mixes with the water, changing its temperature and chemical makeup in ways that harm fish populations. The Army Corps describes plans to minimize these impacts, including the use of less-damaging dredging equipment and limiting dredging to times of the year when it would cause the least harm to wildlife. The environmental groups say these assurances are not adequate because dredging at the planned times could still harm smelt and salmon, and because the Army Corps says it will use these methods when “practicable” — which environmentalists see as a significant loophole.

And they warn that dredging could stir up heavy metals and other toxic pollutants now settled in the floor of the channel. Townsley of the Army Corps of Engineers responded that the Corps does some routine dredging every year. “The process includes rigorous sediment testing,” he said, and “it has not identified challenges with the cleanliness of the dredged material in the channel.” The environmentalists say they should also test the water before approving the project.

Environmentalists also raise questions about the recent decision to limit the dredging project to a 13-mile stretch mostly west of Martinez, rather than continuing it to the port of Stockton, as originally envisioned. They suspect that the project stops where it does because going farther inland would worsen an already serious environmental problem: increasing the concentration of salt in the Delta. They say the corps is illegally “piecemealing” the project — doing an environmental study of just one part so as not to acknowledge the harm the full project would cause.

Sea-level rise and diversion of water to Central Valley agriculture are already making Delta water saltier. Large amounts of fresh water are being pumped in to keep the salt level down, but if it continues to increase, it will threaten agriculture and every other aspect of the Delta ecosystem. The Army Corps of Engineers acknowledges that this is a serious issue for the dredging project. It will be a factor in the decision about whether to deepen the shipping channel to 37 feet or 38 feet. Deeper dredging would save the oil industry more money but allow more salt upstream.

The Environmental Impact Statement says planners limited the project to the western section because that’s where it’s currently needed. Dredging the first 13-mile stretch is “more appropriate for the immediate problems facing existing vessels.” The dredging is planned to go just past the eastern-most refinery in Martinez.

Townsley of the Army Corps said the “rescoping was based on a number of factors, not just environmental.” A large part of the motivation for the project, he said, is the “national economic interest — why taxpayers in Kansas would find some value in it.” He said planners evaluated whether the stretch farther east has “enough maritime commerce to justify” the expense. He said it was “close to being a positive” but was rejected because of “the complexity of the study — other factors.”

The Port of Stockton is the official “nonfederal sponsor” of the project because the original plan was to deepen the channel all the way to Stockton. Spokesperson Jeff Wingfield said the port hopes the eastern phase will be completed next. That raises another fear in the environmental community. Stockton doesn’t ship petroleum, but it does export coal — and it can’t get big ships fully loaded with coal down the Carquinez Strait. Environmental and community groups fighting coal exports in Richmond — and potential coal exports in Oakland — fear shipments of coal will increase if shipping channels are deepened to Stockton.

Finally, project opponents charge that the Army Corps of Engineers has not consulted enough with the community in developing the project. They say an initial community hearing in June was poorly publicized. They also point out that Corps staff members who wrote the Environmental Impact Statement are based in Florida. They say work on the project should be done by local people who know the area and can consult with the community.

Townsley responded that developing the project was “a team effort” in which “local people were well represented.” It’s Corps policy to “get expertise wherever we can,” he said, “but we make sure we have people who understand the local conditions.”

The public comment period on the Environmental Impact Statement has officially closed, but project opponents attended an Army Corps of Engineering hearing on a related topic in July and demanded more opportunity for public input on the dredging project. Afterwards spokespeople for the project said that although the official public comment period has closed “the Corps maintains an email address at SFBaytoStockton@usace.army.mil for comments related to this action. Responses to comments received through September 2019 will be included in the Final Report.”

Townsley said the Army Corps “goes through a fairly rigorous process of coordinating with other agencies and collecting comments.” All the comments and letters on this project show “exactly the way the system is supposed to work.” He added that the Army Corps plans to hold another public hearing on the dredging project, probably in late September or early October. The final report is expected after the first of the year.

Air District fines Valero for recent emission release violations

Repost from KQED News
[Editor: Significant quote: “The risk of these tiny particles getting into people’s lungs is yet another example of the dangers of living near a dirty refinery,” said Hollin Kretzmann, a staff attorney at the Center for Biological Diversity. “Communities should not have to be afraid of breathing in pollution that could affect their health.”  – R.S.]

Air District Hits Valero With Violations Over Benicia Refinery Releases

By Ted Goldberg, Mar 15, 2019
A sooty plume, containing petroleum coke particulates, emerging from flare stacks this week at Valero’s Benicia refinery. (Solano County Department of Resource Management)

Local air regulators have issued seven notices of violation against the Valero Energy Corp. over a malfunction at its Benicia refinery that has led to the release of petroleum coke dust from the facility since Monday.

The problem has led to a response by four agencies: the Bay Area Air Quality Management District and Solano County health officials have launched investigations into the releases; the U.S. Environmental Protection Administration and the Benicia Fire Department are monitoring the situation.

It’s unclear how long the problem will last.

“Valero is telling us they are unable to give an estimate of when it will be resolved,” said Benicia Fire Chief Josh Chadwick.

A Valero representative says the malfunction is tied to a device that removes particulates during a process that takes place inside the refinery.

“We have been experiencing operational issues with the flue gas scrubber,” said company spokeswoman Lillian Riojas.

That led to so-called coke fines — very small carbon particulates that are a byproduct of the oil refining process — being released from the refinery’s flare stacks.

Normally, warm water vapor moves through the refinery’s towers and exits the stacks as steam, but the petcoke particulates make the plume appear dark and sooty.

“The fines remained in the raw exhaust gas,” said Professor Eric Smith, associate director of the Tulane Energy Institute, specializing in refinery operations.

“The dark smoke will continue until all of the fines in the lines leading to the exhaust stack have been cleared from the system,” Smith said.

While the material is not hazardous, the releases could include trace amounts of heavy metals, according to Terry Schmidtbauer, Solano County’s assistant director of resource management.

Valero’s Riojas did not respond to follow-up questions about the status of the scrubber that led to this week’s releases, but Benicia Fire’s Chadwick said Friday that “the maintenance issue has been resolved.”

So far, air tests have not raised concerns among the agencies monitoring the site. Crews have not detected high levels of sulfur dioxide, nitrogen dioxide or particulate matter, according to Chadwick.

And Schmidtbauer says the situation is slowly improving — the amount of coke dust coming from the facility has been lessening.

Nevertheless, the air district has issued four notices of violation against Valero for visible emissions and three for public nuisance,  agency spokesman Ralph Borrmann said.

The U.S. EPA says significant quantities of dust from pet coke can present a health risk.

“The risk of these tiny particles getting into people’s lungs is yet another example of the dangers of living near a dirty refinery,” said Hollin Kretzmann, a staff attorney at the Center for Biological Diversity. “Communities should not have to be afraid of breathing in pollution that could affect their health.”

The problem represents one of the more extensive malfunctions at the refinery since it lost all power on May 5, 2017, an event that led to a major release of pollution, shelter-in-place and evacuation orders.