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Rainy Season Ending, Tijuana River Sewage Discharge Still A Focus

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Posted: Friday, May 17, 2019 10:54 am

For those who appreciate southern California’s seemingly endless days of sun, April usually brings an end to the rainy season in San Diego County. The end of the rain brings sunshine, but for those who really like to spend time in the water, the best part is that it brings an end to the rain-caused beach closures.

April started out feeling like the rainy season was over, but this year the rain has continued often from the final week of April and it continues to be in the forecast this week. But while locals generally know to avoid the water after a rain event – because of urban run-off and water flowing through the Tijuana River carrying many types of pollutants, John Rendine found something interesting this year. While the first few weeks of April did bring dry weather, he says there has been a recurring pattern of overnight discharge in the Tijuana River regardless of weather. Since the river is intermittent (or seasonal), outside of a rain event, it would be expected to be either dry or drying out. But Rendine reported overnight flows in the millions of gallons, based on United States International Boundary and Water Commission (USIBWC) data, particularly during the month of April. USIBWC has provided explanations for some of these events.

John Rendine is a retired Navy officer and former software systems engineer, who is a volunteer with Citizens Against Sewage. He took over monitoring the International Boundary and Water Commission (IBWC) gauge data for the group about a year ago. While the group has been monitoring it for longer, he began to automate and further refine their understanding of the flows and the state of the river so as to better highlight and anticipate pollution in the Tijuana River Valley (TRV) and in the beach waters.

The USIBWC data also provide cumulative precipitation data recorded at the gauging station. As Rendine points out, “This is a single point of precipitation data and we do not have rain gauges over the whole Tijuana River watershed (both sides of the border), so when we have no measurable rain on this side of the border, it might have rained somewhere up-river in Mexico. What we are observing from the USIBWC data is that even when there is no precipitation, there are often nightly flows for a several hour period.”

Rendine said in April, “Since the rain has stopped, overnight discharges have been recorded.” During the month of April, Rendine documented that based on USIBWC data, discharge flows were reported almost every night of some magnitude, ranging from under 10,000 gallons to over 2 billion gallons (during one three-day period non-stop). In total during the month of April which, until the very end of the month saw little to no precipitation in San Diego, Rendine calculated over 2.25 billion gallons were reported by the IBWC gaging station.”

This dry weather flow in the river – which implies sewage and/or other pollutants such as industrial discharge -- are part of the cause of beach closures beyond the usual advisories following rain events. When these are combined with the 20 million gallons of sewage that, according to Surfrider, is reportedly dumped daily at Punta Bandera, just five miles south of the US border, the chances for closures and for illnesses from having contact with polluted water increase.

Mitchell McKay is a long-time South Bay resident concerned about pollution in the TRV. He is also the President of a newly founded South Bay non-profit, Citizens for Coastal Conservancy (C4CC). Of the continued transboundary sewage flows, he says it’s a matter of environmental injustice: “Depending on your zip code, 130 gallons in La Jolla is a leading story but we [in the South Bay] struggle and fight for coverage and a sense of urgency for the magnitude of our shared transboundary sewage problem … the South Bay is not getting the attention regionally or nationally, from the EPA, the IBWC, [IBWC Commissioner] Jayne Harkins. Based on Rendine’s calculations using the IBWC’s own river gauge data, the cumulative flow exceeds 18 billion gallons since October 2018.”

The USIBWC near the end of April reported via twitter that there had been flow and that it consisted of “treated and untreated wastewater in addition to groundwater and rainstorm runoff.” The IBWC further noted, with regard to some of the flows in April, that repairs were being made overnight on the Mexican side of the border and that, “Mexico will be taking all possible measures to send the wastewater in their collection system to the Southbay [sic] International Treatment Plant but there may [be] some flows that enter the Tijuana River as a result of this work.”

With regard to the massive flow during the three-day period in early April, Carlos Pena, the area Operations Manager for the USIBWC said that during that period, “Our gauging station was malfunctioning and the reading was not correct.” But Ginger Sacco, from CAS, finds this explanation dissatisfying. She said that in her experience, when the gauge isn’t working, it simply doesn’t record flow at all. When asked for a revised estimate, Pena said, “The data from the days in question is not usable and an estimate is not available.”

Beginning several weeks ago, in an attempt to help stymie flows, both the USIBWC and Mexican IBWC constructed berms. The earthen berms, constructed across the river, are a cheap and effective method to block relatively small, usually dry-weather spills. William Bay, a photographer who grew up in Imperial Beach, has been documenting the building and rebuilding of the berms over the last several weeks. He took photos of the berm construction and spoke with workers on the Mexican side of the border. Of the Mexican berm, he said, “Despite IBWC official Dawi Dakhil claiming the berm is 8 feet tall, it’s clear that the berm is about 4 feet max.” The center washed out almost immediately as a result of rain. Bay says that he checked last week and they appeared to be rebuilding.

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