ADEQ works to stop contamination plume

Agency concerned with long-term exposure to groundwater tainted by chemical leak

If nothing were done to stop a contaminated groundwater plume, it would head straight to Alice Byrne Elementary. The main concern for officials with the Arizona Department of Environmental Quality are the teachers and staff, not the students.

Students aren’t there long enough, moving on to other schools, limiting their exposure. On the other hand, teachers and staff are known to spend entire careers at that school, sometimes spanning several decades, potentially exposing them to contaminated well water in the long term.

However, ADEQ hydrologist Richard Snyder said that a person would have to come into fully body contact with contaminated water, such as showering in it or rolling around in a puddle, for it to be dangerous. Alice Byrne uses only well water for irrigation and does not use it for drinking or other purposes.

The agency held a public meeting last Wednesday afternoon to discuss proposed plans for cleaning up the contamination that originated at 20th Street and Factor Avenue. A Community Advisory Board listened to Snyder as he reviewed the site history, feasibility study results and a proposed plan to fix the problem.

In 1990 Houston International, formerly Houston Photo Products, reported a leaking underground storage tank located near the southeast corner of the 20th Street and Factor Avenue intersection. Leaked contaminants included tetrachloroethene, trichloroethene, 1,1- dichloroethene and cyanide.

Historical operations at the former Houston facility included a motion picture laboratory and an area that manufactured photographic film and paper processing equipment for the photo industry. The facility used tetrachloroethene in a vapor degreaser for parts cleaning. Operations were discontinued more than 20 years ago.

The facility is currently occupied by commercial businesses including a film processing equipment manufacturer, an engine services company and a personal storage facility.

The 80-acre site is in an area that includes commercial and light industrial businesses, warehouses and residential neighborhoods. Three schools are located downgradient of the existing groundwater

plumes.

The contamination plume is bounded approximately by 17th Street to the north, 21st Street to the south, Kennedy Lane to the east and 4th Avenue to the west.

ADEQ invested the soil and groundwater at and in the vicinity of the Houston facility. After finding various contaminants, the agency took immediate action to take care of some issues right away. The agency found that some of the contamination had also come from water disposal systems including septic systems and sumps. It removed four of these and cleaned another septic system as part of the early response action.

In addition, cyanide soil was excavated to a depth of one foot along the south and east of the property boundaries and covered with gravel and asphalt.

As part of the investigation, the agency installed numerous wells for monitoring groundwater contamination. Three aquifer zones have been identified at the site with the upper two containing contamination. The plume is about 4,500 feet in length and flowing in a west-northwesternly direction.

“It’s a pretty good size plume,” Snyder said.

The good news, he noted, is that the contamination plume has been moving extremely slowly. At this point it has only reached 3rd Avenue. Alice Byrne is at 16th Street and 8th Avenue. (Two other schools, St. Francis Assisi Catholic School and Harvest Preparatory Academy, are more to the south, out of the plume’s reach.)

It seems that nature has been healing itself with naturally occurring microbes digesting the contaminants. This has slowed the speed of the flow. As the plume dilutes and dissipates, it travels even slower. Also, as the plume moves, it’s not getting deeper.

Monitoring wells show drops, in some areas, “drastic” drops, in the levels of contamination.

“The natural system is doing its job,” Snyder said.

The agency did a few studies and modeling to determine the travel time of the contaminants. They indicated that without any action, the contamination would likely reach the school in 25 to 30 years.

The agency completed the final remedial investigation report in June 2014. It contained three alternative remedies. A feasibility study work plan was completed in November 2014 and the report in August 2016. The agency took comments from the public on the proposed remedies between July 12 and Oct. 11.

The remedy selected by the agency includes injecting molasses or vegetable oil into the subsurface using a small drilling rig at the contamination hot spots and the downgradient edge of the plume. The intent is to provide a nutrient to help stimulate the biodegradation of the contaminants.

The estimated cost to implement this remedy is about $3.9 million. The costs accrued by ADEQ so far total $7.9 million.

The agency will continue to monitor the wells after the injections have stopped. The agency will also keep an eye on the asphalt cement cover to ensure that it maintains its integrity.

Once contaminant concentrations are below the aquifer water quality standards, the wells will be abandoned and the site delisted. The agency expects this to be a four-year process.

“It took some time, but now we have our arms around it,” Snyder said.

The goal is to stop the contamination plume from reaching Alice Byrne. “That’s what we’re working on, to stop it in its tracks so it doesn’t get to the school,” Snyder said.

If the remedy plan doesn’t work, the agency will likely shut down the wells and provide the school with irrigation water.

But the agency believes it will “knock down” the contamination before it gets any further. Snyder said that a contractor has used this method at other sites and it’s been “quite promising.”

The agency is now finalizing a Record of Decision to implement the plan. Snyder expects this to end by January. Snyder hopes

to start implementing the plan in February or March. However, it all depends on when funding becomes available.

“I’ve got to beg for money first,” Snyder said. “Our main problem is always, ‘Will you give us money?’”

He noted that it comes at a time when the Legislature is talking about cutting the agency’s budget. He suggested attendees write to their legislators about it.