IOI breach

Seen here Monday, water runs through Potrero Creek just south of the partial breach as crews worked to divert the flow of the sewer line.

Authorities say sewage is no longer leaking into Potrero Creek from a broken section of cross-border sewer line after crews finished installing a bypass system early Wednesday.

John Light, area operations manager for the U.S. Section of the International Boundary and Water Commission (IBWC), said a contractor laid 11,400 feet of pipeline, effectively rerouting the sewage around Manhole 89 and up to the Nogales International Wastewater Treatment Plant just north of the break.

The fix is temporary, however, and the broken pipe itself has yet to be repaired.

The IBWC announced last Friday that it had hired Tucson-based contractor KE&G for $300,000 to repair the breach. On Monday, crews were seen preparing plastic pipes to divert the flow of wastewater so that work on the damaged section of pipe could begin. According to the county, the IBWC notified the Santa Cruz County Emergency Operations Center that the contractor finished connecting the pipe at 2 a.m. Wednesday, stopping the flow of wastewater into the creek.

Light said crews with KE&G are operating the bypass 24 hours a day and have staff on site to ensure the pipe is working properly.

“They are continuing, with our team of engineers, to investigate damage to the pipeline – where it occurred, extent of the damage and possible resolutions for the repair,” he said during a news conference at the County Complex Wednesday afternoon.

Light said the IBWC is working with the city and county to find an “ultimate” solution and the bypass will remain in place until the breach is repaired.

The break in the line just north of city limits was discovered Tuesday, July 25. Gov. Doug Ducey declared a state of emergency two days later after testing by state environmental officials found excessive levels of E. coli bacteria in sections of Potrero Creek near the pipeline break.

Hans Huth, an associate hydrologist with the Arizona Department of Environmental Quality, said staff is collecting water samples immediately up and downstream of the breach, in addition to sites in Pima County and as far north as Eloy.

E. coli, a bacteria found in the digestive tracts of humans and warm blooded animals, is generally spread through food or water contaminated with human or animal feces, according to the Mayo Clinic. E. coli infections can cause diarrhea, abdominal pain and fever, and, in severe cases, kidney failure, which can lead to death if left untreated. Children, the elderly and pregnant women, as well as those with a weakened immune system, are the most at risk for developing severe symptoms.

According to the Arizona Emergency Information Network, the state’s water quality standard for E. coli is 235 colony-forming units per 100 milliliters of water (CFU/100 mL) for full body contact.

ADEQ initially tested for a variety of contaminants, including E. coli, nutrients and heavy metals, which weren’t detected. Samples were taken in an area already designated as “impaired” for E. coli, meaning that the Nogales Wash consistently contains levels of E. coli that are above the state’s water quality standards, and staff is working to determine the extent of the increase in E. coli levels caused by the breach, according to AzEIN.

Samples taken Aug. 1 show that there were 579,400 MPN/100 mL detected at the site of the break, 517,200 MPN/100 mL at a site above the break, and 143,900 MPN/100 mL at a site below the break, according to test results posted to the AzEIN website. MPN, the most probable number, is a statistical probability of the number of organisms per 100 milliliters of water.

Because the pipe is no longer spewing raw sewage into the creek, Huth said, ADEQ will most likely only collect samples through Friday, Aug. 4.

Asked if the contaminated water had reached the Santa Cruz River, County Health Services Director Jeff Terrell said it most likely had due to monsoon rains. He added that municipal water sources along the river were safe because “their wells are far enough away,” but he still encouraged those with private wells within 100 feet of the waterway to have their wells tested for contamination.

Terrell said he was unsure how many wells were within that 100 foot area, but added that the county was working to collect that data and add it to an online map where visitors can also see testing sites and results.

Though there are no labs certified for testing water samples in Santa Cruz County, there are several in neighboring Pima County. People can also visit the Arizona Department of Health Services at or call (602) 364-0720 for more information on certified labs.

The pipeline, known as the International Outfall Interceptor, carries 10-14 million gallons of wastewater from Nogales, Sonora and Nogales, Ariz. to a treatment plant in Rio Rico each day. It follows the bed of the Nogales Wash north to Potrero Creek and then to the plant, nine miles north of the U.S. Mexico border.

Potrero Creek joins with the north-flowing Santa Cruz River in Rio Rico.

Rebuilding slopes

A team from the U.S. Army Corps of Engineers, which was deployed last Friday to assist with the rebuilding of slopes along the Nogales Wash that were eroded by recent floodwaters, was also working on repairs along Hohokam Drive this week where about 280 feet of the IOI became exposed – but didn’t break – after a storm in late July. Proposed work entails armoring an earthen berm with mesh wiring or riprap, which consists of loose stones used to form a retaining wall, and then pouring shotcrete over it.

Additionally, crews are working to stabilize the west bank of the Nogales Wash near Marten Road north of city limits. Work is also being carried out on the Donna Avenue bridge at the north end of Nogales to protect the abutments, according to a news release from the corps’ Los Angeles District.

With crews working against the weather, it was unknown when repairs would be completed, said Jesus Valdez, county public works director.

The county has established a hotline for public inquiries about the IOI breach at (520) 375-7784 and said updates will also be posted on the county’s Facebook page, Twitter feed (@santacruzaz) and at

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