~Lactose, veggie oil to stimulate toxic-eating bacteria
Cleanup of contaminated groundwater between Alameda Point’s Seaplane Lagoon and Main Street will begin later this year, according to the Navy. The cleanup area is directly south of the Site A residential and commercial parcel slated for groundbreaking in a few months. It is one of the most difficult environmental cleanup areas to remedy at Alameda Point, which is why it has taken 20 years to figure out what plan to implement. The Navy’s contractor presented the cleanup plan at the March 9, 2017 Restoration Advisory Board meeting at Alameda Point.
A cleaning solvent called trichloroethene was used in the Navy’s industrial repair and refurbishing operations in this area. The solvent leaked into the ground to depths of 70 feet and spread around nearly 19 acres. Industrial activities included the Aircraft Engine Test Facility in Building 360, which is the large building next to the Main Street soccer field, along with the Engine Test Cell in Building 14, and the Ship Fitting and Engine Repair Facility in Building 162.
“Each one of these buildings involved [employees] working with engines. So they worked with degreasers, and that’s where the chlorinated solvents come from,” said Dr. David Cacciatore with CB&I Federal Services, Inc., the Navy contractor that will conduct the groundwater bioremediation. “Spills or [leaks from] vessels within those buildings have caused this release to the groundwater of those chlorinated solvents.”
Prompt cleanup has been hampered by a maze of utility lines that preclude effective use of faster remedies such as heat-induced vapor extraction and injecting special chemicals into the ground to neutralize the toxic solvent.
The Navy’s contractor will instead rely on a slower method called bioremediation, which utilizes indigenous bacteria in the ground to breakdown the toxic solvent to harmless compounds. Originally, the Navy was considering the use of cheese whey to help stimulate the growth of beneficial bacteria in the ground. But the contractor will instead use 100% lactose, a form of sugar found in milk.
“Cheese whey is about 85% lactose, the rest are mineral solvents,” said Cacciatore. “First of all, it’s harder to dissolve cheese whey in water than it is to dissolve a sugar in water. And also cheese whey involves these mineral byproducts that then foul up the well and leave deposits in the well.”
The bacteria require an absence of oxygen, making this an anaerobic process. “So by ensuring that there’s no oxygen in the subsurface and that there’s a substrate, which is a food source, the bugs basically take these chlorinated solvents and sequentially pull off chlorines until eventually the chlorinated ethenes become ethene and ethane which are non-toxic,” said Cacciatore.
The first round of injections will be only lactose, without any added bacteria. “It’s going to bolster the population of a lot of the organisms that are present,” said Cacciatore. “And then we’re going to come in after that injection of the substrate [lactose] and measure the micro-organisms at select points.” Based on those tests, the contractor may inject commercially available supplies of the friendly bacteria to boost the bacteria count. Vegetable oil may also be injected into the ground to accelerate the growth of the bacteria.
A limited test of heat-induced vapor extraction several years ago using high voltage electrodes removed a significant amount of groundwater contamination, but it only achieved part of the desired goals. A sewer line was damaged during installation of the 30-foot-long electrodes into the ground. Another limitation is that the electrodes heat up the soil at the bottom of the electrodes deep in the ground, rather than creating heat evenly throughout the contamination area to vaporize the contamination. There are also electrical lines coming from the nearby Cartwright Substation that rule out the electrode heat treatment throughout the area.
If the method of injecting neutralizing chemicals were to be used, the various water, sewer, gas, and electrical lines would interrupt the even dispersal of the chemicals. The pipes would be the pathway of least resistance through the soil and lead to uneven distribution.
Also rejected was the method of pumping contaminated groundwater to the surface, running it through a treatment system, and re-injecting the cleaned water back into the ground. This groundwater recirculation method, commonly referred to as pump-and-treat, would use hydrogen peroxide and ozone to change the solvent into harmless compounds. But this process is more expensive than bioremediation and has high environmental impacts due to high energy use and greenhouse gas emissions from running numerous pumps.
Stimulated bacteria, on the other hand, will become a self-replicating, self-expanding cleanup machine.
Maximum cleanup goals will take between 25 and 40 years to reach.
It will take until the year 2023 before the land can be turned over to the city and then sold to private contractors for commencement of new construction. But in the year 2023, the land will still not be totally clean. It will come with restrictions due to the lingering potential for toxic vapor intrusion into buildings. All buildings will require a special vapor barrier and vapor extraction system underneath the structures to provide protection until the goals for unrestricted use and unlimited exposure are achieved. These maximum cleanup goals will take between 25 and 40 years to reach, according to Navy cleanup documents.
The horizontal extent of the contamination, plus a 100-foot buffer area, covers some 19 acres in the cleanup area known as Operable Unit 2B. Construction of buildings with ground-floor residential units or occupancies with sensitive receptors, including schools, child care facilities, hospitals, and senior care facilities, overlying the contaminated area plus the buffer are prohibited until the maximum cleanup goals are achieved.
Shorter version of this story originally appeared in the Alameda Sun.
Additional information –
Alameda Point Environmental Report 