In order to start the expansion of the San Ysidro Port of Entry, millions of gallons of water have been pumped from under the border and into the Tijuana River, but the release of water was approved “without a whole lot of thinking behind it as far as I can tell,” according to a city official.
Bill Harris of the city of San Diego’s Storm Water Division was critical of the decision made by the San Diego Regional Water Quality Control Board, which OK’d the release amid the project.
Harris is concerned the additional water could have an impact on dredging that may begin in the coming weeks in the Tijuana River Valley.
Sediment and debris carried by the river to Smuggler’s Gulch and the Tijuana River Pilot Channel is removed by dredging in order to allow the river sufficient capacity to handle heavy rainfall.
Without removing the sediment, Harris said, a few inches of rain could cause a “flat flood” and threaten the lives of people, horses and wildlife living in the Tijuana River Valley—an area near Imperial Beach and San Ysidro.
Once the new San Ysidro Port of Entry is completed at one of the busiest border crossings in the world, northbound vehicle booths will rise in number from 24 to 62, and Interstate 5 at the border will expand from six to 12 lanes.
As part of the initial stages of construction, about 500,000 to two million gallons of water a day from beneath the U.S.-Mexico border will flow into the Tijuana River for up to 10 months, a government official said.
The water began to flow Nov. 2 and may continue through August, said Ben Neill of the Regional Water Quality Control Board.
According to National Weather Service records, the South Bay gets roughly 10 inches of precipitation a year, with heaviest rainfall from December to March, but the river’s watershed is spread across San Diego and Mexico and covers more than 1,700 square miles.
Dredging may begin within the next few weeks, Harris said, but can be delayed when rain causes heavy flow of the Tijuana River.
During rainfall events over the course of a few days in December 2008 and December 2010, two to three inches of rain flooded the Tijuana River Valley, leading to the evacuation of horses and people.
“If it’s just continuing to flow, we may not be too bad off,” Harris said. “However, if it begins to spread and percolate, then we may have some issues.
“We’re going to get in there this year if it doesn’t rain too hard. We’ve got a real tight window because of the legal crap.”
Multiple lawsuits by the group San Diegans for Open Government have disputed Tijuana River Valley dredging projects for the past three years.
Courts allowed the city to clear the channels by emergency action in 2009 and 2010, but in fall 2011 a temporary restraining order was approved to stop operations until analysis of environmental impact and mitigation plans were completed.
Aside from heavy rainfall, work may stop if dredging disturbs the nesting ground of particular birds, if artifacts are found or many other reasons detailed in an Oct. 15 settlement decision.
All work must be finished by Feb. 15, 2013, the start of the Light-footed Clapper Rail breeding season, and requires the approval of five different government agencies to go forward.
Expansion of the border crossing should not interrupt dredging activity, Neill said.
As of Nov. 20, early indications are that the water will seep into the ground before it reaches the Dairy Mart Road bridge, he said, though that could change in the future.
“The only thing that’s kind of unknown out there is the rainstorms, cause if there’s a heavy rainstorm that’s going to have an impact on the dredging project,” he said. “Right now it looks like the water isn’t going to get down to the part where they’ll dredge.”
A potential 2 million gallons of water a day can sound like a lot, but rain events will likely have a much larger impact, Neill said.
A day after storms brought less than an inch of rain to IB Nov. 9, the Tijuana River was flowing at a rate of 4.5 million gallons of water an hour, or 108 million gallons a day.
“That’s what it peaked at during this last storm, and this is an average of 500,000 a day. That’s half a percent of the peak of the rainstorm,” he said. “I don’t think you would notice the difference between that and the rainstorm. It’s a small amount of value, a real small amount.”
Tests of the water taken prior to the port of entry expansion found concentrations of metals such as lead, copper, zinc, iron and other potentially harmful pollutants as well as MTBE, a chemical compound added to gasoline.
Once the water is treated and contaminants are removed, it is not expected to impact water quality in the Tijuana Slough National Wildlife Refuge or ocean, Neill said.
After the water is pumped from underground, it is passed through a settling tank, sand bags, granular carbon and an ion exchange treatment before being sent to the river, Neill said.
Flow rates and cleanliness of the water will be tested at the U.S.-Mexico border, Hollister Street bridge, Dairy Mart Road bridge and the mouth of the Tijuana River.
The first monitoring report is due Dec. 30, Neill said.
Congress has not yet allocated funds necessary to complete the new border crossing, said Traci Madison with U.S. General Services Administration. U.S. Customs and Border Protection will operate the border crossing.