Plumes of poison

Last fall, Don Mandel was exploring southwest Chico, off River Road, looking for a possible site for a well. Mandel is a project manager for the state Department of Toxic Substances Control (DTSC), and he wanted to drill a monitoring well to assess the spread of contaminated groundwater in what is known as the Southwest Plume.

He was driving down Miller Avenue when “lo and behold, there was a new well"—one that didn’t show up on his maps. Other private wells in the area had been closed in 1991 because of the presence of the solvent perchloroethylene, or PCE, in groundwater, and residents along Miller and nearby streets had been connected to the water system of California Water Service Co. (CWS). This working well was unique.

It dated to 2002, was about 200 feet deep, and had gone in when a mobile home had been put on the site. When the water was tested, it showed 150 parts per billion of PCE, an amount 30 times the maximum contaminant level (MCL) that is considered safe, 5 ppb. It was the highest concentration yet found in the plume. “We were shocked that it came back in that concentration,” Mandel said. Residents of the home were supplied with bottled water.

The discovery was a reminder that, in the 22 years since groundwater contamination first was found in the Chico area, in October 1984, it remains a persistent and pesky problem. Because of various treatment remedies, the overall levels of contamination have gone down significantly, but it could be another 10 or 20 years before the water is completely clean.

There are eight distinct plumes of contaminated groundwater under Chico. They’re called plumes because of their feather-like shapes, but there’s nothing pretty about them. All contain or contained unsafe amounts of a carcinogenic solvent—TCE (trichloroethylene), PCP (pentachlorophenol), PCE or DCE, which is a breakdown product of PCE—and all are in the aquifers that supply Chico’s drinking water.

Most came from dry cleaning companies, which in the past often disposed of solvents in less-than-ideal ways—pouring them down the sewer or into a septic tank or simply on the ground. Chico’s sewer lines often leaked, allowing the contaminants to get into the groundwater.

Two plumes—the airport plume and the Victor/20th Street plume in south Chico—were caused by the same company, Victor Industries, which operated a plant at the airport before moving to a site at East 20th and Mulberry streets. Victor made aluminum tubes (for toothpaste, mostly) and aerosol cans, and used TCE and PCE as machinery degreasers, allegedly dumping it on the ground afterwards.

DTSC has spent more than $10 million so far on just the Southwest and Central plumes, Mandel said, and neither is clean yet.

Since the contaminants have been found, Cal Water has carefully monitored its drinking-water wells. So far it has discovered contamination in four of them; two have been abandoned, a third has been outfitted with a treatment system, and a fourth has been offline for several years, said the company’s Mike Pembroke. CWS also operates two DTSC treatment wells at Chico Junior High School. Whenever the slightest amount of pollutant is detected in a treatment well, Pembroke said, it is shut down and the filter is replaced. Chico’s water is completely safe to drink, he said.

Here’s a brief rundown of the status of Chico toxic contamination plumes:

Chico Municipal Airport Plume (1): This plume extends for almost a mile from the airport southwest toward Sycamore Creek. DTSC finalized a remedial-action plan (RAP) to clean up the TCE in the groundwater, but the city of Chico has been unable to implement it because it calls for an extraction well in a wetland area with populations of the endangered Butte County meadowfoam. The city is looking for an alternative site. When treated, the water will go into the city sewer system.

North Valley Cleaners Plume (2): From 1964 to ‘88, this dry cleaner at the North Valley Plaza discharged chemicals into an on-site septic system. Following years of study, in 1998 the DTSC issued a remedial-action order to the responsible parties, who are currently developing the site-specific risk assessment and feasibility study leading to a final RAP.

North Central Plume (3): This is a success story. Although residual amounts of PCE and DCE have occasionally been found at one of the three monitoring wells located at the original source of the contamination (the former First Avenue Cleaners, at the freeway where the Spa Broker is now located), the amount was well below the MCL. Monitoring at the CWS treatment well at the center of the plume has detected no pollution since 2004.

Central Plume (4): This is by far the largest and worst of the eight plumes; it originally contained concentrations of PCE as high as 2,900 ppb. Although DTSC has been working to clean it up since 1986, the agency is only now preparing to release a draft remedial-action plan to the public. Unless there is significant public resistance to the plan, Mandel said, it will be implemented before the end of 2007.

At this point the plan calls for three new “pump-and-treat” wells to be added and connected to two existing treatment wells at Chico Junior High School. Those wells, which use granulated activated carbon to filter the water, have been operating as an interim measure since 1997, treating almost 400 gallons of water a minute. Thus far they have removed, according to a DTSC fact sheet, “in excess of 1,300 pounds of PCE from the Chico drinking water aquifers"—the equivalent of two 55-gallon barrels of pure PCE.

Until recently the state had difficulty getting the parties responsible for the contamination—there were several, but the main ones were Esplanade Cleaners and Flair Custom Cleaners—to pay for cleanup. State bond money paid for the interim treatment wells, but then the money dried up. Finally, in 1999, the insurer for Esplanade Cleaners stepped forward, voluntarily financing the construction of 21 monitoring wells that have enabled DTSC to determine just where the three new treatment wells called for in the RAP should be placed, Mandel said.

The state is also close to signing a settlement agreement with the remaining responsible parties, he added.

Southwest Plume (5): Three now-defunct dry cleaners contributed the pollution in this plume, which is about seven blocks wide and two miles long and extends from the south campus neighborhood west into the orchards. CWS and DTSC installed a carbon treatment unit on one CWS well; at the beginning of treatment, groundwater samples tested as high as 38 ppb for PCE, but today they are averaging about 10 ppb. DTSC has five monitoring wells in the deep aquifer, and they are showing clean water. The agency has punched 13 wells in the intermediate aquifer but, as the Miller Avenue find showed, still hasn’t defined the limits of the plume. Much work remains to be done to clean up this plume.

Louisiana-Pacific Plume (6): Another success story. Residual pollution from the old Diamond Match plant included arsenic in the soil and PCP, ethyl benzene and xylene contamination in the groundwater. Some 30,000 cubic yards of soil has been excavated, consolidated on site and covered with a three-acre asphalt cap. A groundwater extraction and treatment system worked so well that it was shut down in 2003, though regular monitoring continues. The site is considered clean and ready to be developed.

Victor/20th Street Plume (7): This plume stretches from Mulberry Street a mile and a half to the Stanley Park neighborhood off Dayton Road. Residents of the neighborhood were connected to CWS in the mid-1990s. DTSC has obtained settlement funds from the responsible parties and used it to extend the water line to the Chico Mobile Country Club. Currently DTSC is working on a design for a groundwater extraction and treatment system and should have a RAP ready for review by mid-2007.

Skyway Homes Subdivision Plume (8): First discovered in 2003, the plume has contaminated a number of private wells in this neighborhood off Hegan Lane. In 2004 DTSC began a bottled-water program for residents, then in 2005 put individual carbon treatment units on the private wells. It has since determined the probable source of the contamination: the former CE Building Products factory on Speedway Avenue. The company manufactured metal frame windows and aluminum shower enclosures and used TCE as a degreaser to clean parts. DTSC has drilled 12 monitoring wells but says more will be needed before it can determine the complete extent of contamination.