BISBEE – On Sept. 9 last year, a major disruption in the wastewater system just across the border in Naco, Sonora, caused over four million gallons of raw sewage to flow into Naco, Arizona, and the Cochise County Board of Supervisors declared a county emergency.
The leak was stopped temporarily as local, state and federal officials joined in talks with Mexican officials to find a permanent solution. Those talks resulted in a plan to divert flow from a deteriorating collection line with a new bypass, new and replacement line installations, a new pump and repair of the lagoon system, according to Robert Molina, with North American Development Banks’s (NADB) grant project department. NADB provided funding for the project.
CONAGUA, which operates the plant, hired a resident engineer to oversee the system and installed monitoring systems in the lagoons and manholes, explained Molina in a presentation to the board of supervisors in February.
He also said a vacuum truck from Nogales was used to clean out the poorly maintained lines to remove blockages, which included a cow’s head stuck in the International Interceptor pipeline that runs along the wall.
To defray costs of the operation of the wastewater system, a solar project is being designed. At one point, it was discovered the power bills were not being paid and resulted in the cutoff of electricity. With pumps down, there was no way to move the sewerage through the system.
The problem with raw sewerage flowing into the U.S. has been ongoing for years, but last year’s spill threatened the Naco Port of Entry and Naco Elementary School to the east and ranchland and the San Pedro River to the west. The sewerage came across the border at a rate of 430,000 gallons a day, an estimate made by county Emergency Services Coordinator Gabe Lavine at the time.
Supervisor Ann English said Friday, “It is my understanding, after getting information from the county emergency services department, there have been no sewage flows for months. I can assure you, Cochise County does not want the sewage from Naco, Sonora, to contaminate the soil or water on our side of the border. We worked to get the upgrade and maintenance of the Naco, Son., sewage treatment facility funded through U.S .and Mexico federal dollars, not local tax dollars.”
NADB, which received some funds from the Environmental Protection Agency (EPA), is overseeing the repairs on the Naco sewage treatment facility, she continued. Emergency services and the county health department are continually monitoring for any flows and will look for solutions when needed.
“When necessary, we will call on our state and federal partners to help us again as we have in the past,” English noted.
Lavine affirmed previously, “The county will ensure a robust response to any substantial sewage flows in the future.”
The EPA and Arizona Department Environmental Quality (ADEQ) remain engaged in the progress of the repairs. The EPA provided technical assistance to Naco, Sonora, for a diagnostic study to pinpoint the main issues and scope the infrastructure project appropriately.
According to Molina’s report, the construction of a $5,000 bypass on Jan. 11, paid for by the Mexican section of the International Boundary and Water Commission, was necessary to divert flows from a “problematic manhole” located near the international border wall west of the port of entry.
A major issue with the system is it was constructed many years ago and the population has risen since 1996. The citizens’ usage could be exceeding the capacity of the system, Molina suggested.
He also cited the lack of utility bill collection in Naco and administrative issues with Mexico’s National Water Commission as ongoing impediments to financing and completing the work.
One recent incident almost caused problems due to a blockage near Manholes No. 1 and No. 5, but the blockage was cleared in time before any spillage, reported Molina.
In response to questions, Jesse Hereford, with the NADB, said 75 percent of the 1,200–foot main interceptor line which parallels the border has been replaced. According to the consulting engineer, it was at the highest risk of collapse.
“Once we replace the interceptor, the risk of this happening is highly unlikely. However, we cannot predict the intensity of the monsoon season, like a 100–year storm event,” Hereford said.
The bypass installed will continue to divert flows from west to east and reduce the pressure in Manhole No. 1, Hereford added.
The last section of the interceptor line will be completed by the end of June.