And, the Marina was also the place where man-made gas was produced. The Marina Times
wanted to investigate more about the allegedly and potentially harmful residue from hydrocarbons. So, the editor there called upon this reporter to get the details.
The hydrocarbons date back to the 19th Century in the form of tar. PG&E reassured, when this reporter spoke to representatives that the left-over tar is being monitored and cleaned up. Speaking on behalf of PG&E, Nicole Liebelt noted toxicologists and health experts, have established that exposure to tar residues is not common because, in most cases, they are located below the ground surface. She explained further that, in the mid 1800s and early 1900s, before natural gas was available as an energy source, more than 1,500 manufactured gas plants were located in cities and towns across the country.
Gas manufacturing in the City of San Francisco
originated in the Gold Rush era, in the early 1850s, when the City was the key urban and financial center for the U.S. western territories. The San Francisco Historical Society
and SF Museum also confirmed that in the Gold Rush days
and there after, at least four manufactured gas plants supplied gas for lighting, cooking and heating. One was the North Beach Gas Plant. It was located at Bay and Buchanan and another was near the area west of Fillmore and Bay Streets.
Kathleen Iudice of the SF Historical Society and Museum, pointed to the fact that documentation shows that engineers at the time of the 1906 Earthquake worked diligently to shut off the gas and then repair the system. (Such is explained in the account written in 1906 by Edward Jones, a gas engineer for the SF Gas and Electric Company).
Realtor and SF Historical Society member, Gloria Rogan
said that during those early days much of the Marina District was basically "swamp-land" used as a place to gather cows and wash clothes. "This is how the name 'Cow Hollow' came about" said Rogan.
She mentioned that much of the land demographics of the City in those days cam be found on maps of the period. "The real estate maps dating back to 1904 show all the ground water," she said. While according to Rogan and other historical researchers, manufactured gas at that time was produced with "carburetted water."
(That was the term used back then). With all that water, such as watering spots for cattle, dairy farms and the lagoon known as "Washerwoman's Lagoon," 19th Century engineers made gas through a process of passing steam over red-hot carbon fuel.
The problem with this process is the risk of carbon monoxide poison. The process also produced a lot of waste material in the form of tar, which includes cyanides, metals, solvents. By the time following the 1915 Panama-Pacific International Exposition the old system of "water-gas" was completely dismantled and demolished. Also, Liebelt noted, "PG&E wants to ensure that any potential impacts to the environment from former MGPs are addressed in accordance with today’s regulatory standards."
"Of the 41 manufactured gas plant sites (MGPs) historically owned or operated by PG&E, she noted, through the 1950s, 40 have been or are in the process of being investigated, cleaned up or remediated." "The investigation of the former MGP sites in the Marina District were initiated in 2010" she said.
The concern about tar residue from old manufactured gas plants h
as been on-going for many years. More than 20 years ago, the United States Environmental Protection Agency (EPA) conducted research that identified around 1,500 former manufactured gas plants around the country.
The research found that, in some cases, residues from these facilities may remain on site. Water contamination is rare. But there is always a danger that tar can cause health hazards, this is why monitoring and testing is important.
Following the EPA study, PG&E voluntarily, along with other utility companies across the country, established a program to identify the location of MGP sites and began a process of testing groundwater and soil samples from sites in the service area.
Liebelt mentioned to this reporter that one thing that was not stressed in previous reports is
that the cooperation of the public in the effort is voluntary. PG&E notifies residents and welcomes them to participate. She confirmed that in some instances temporary relocation has been requested by property owners. Presently, only five property owners in the Marina area have chosen to participate in the clean-up process, which if requested, includes temporary relocation. PG&E would not disclose where those five properties are, only that they are in the footprint location of the two old MGP sites.
The duration of the tar residue clean up process is anticipated to take approximately six weeks to four months. This might involve soil removal, which could range from very little to approximately 50 yards to 300 cubic yards. "It’s really dependent upon the site and the residual impacts found on that particular property," she said. Most of the tar residue is within the footprint of the former MGPs, generally at a depth of about three feet. No residue has been found at the surface of any of the property sites tested so far. And, PG&E officials said they don not expect to find any.
The San Francisco Examiner mentioned in their article
on the subject of the old MGP sites that "volitile organics" could form, as The Examiner talked with other officials at agencies like The Dept. of Toxic Substances Control
and the Bay Area Air Quality Management District.
Leibelt did emphasize that the cost of clean up would be paid by PG&E. For more information about the MGPs residue clean up program, call 415-973-0270 or email PG&E.