By Stephen Young
By Stephen Young
By Stephen Young
By Jim Schutze
By Rachel Watts
By Lauren Drewes Daniels
Public officials are saying things now about the Trinity River in downtown Dallas that make no sense, are impossible to believe and may even be sort of crazy.
Here's the basic: The whole multibillion-dollar Trinity River project, Dallas' Big Dig, is on hold and in trouble because the U.S. Army Corps of Engineers say they have "discovered" sand in the Trinity River bottoms.
The sand, they say, might destabilize the levee system that protects downtown from flooding. They have halted work, although they deny it, on a new bridge over the river, because of the sand.
They say they didn't know.
I'm not sure I can even express how insane that is. It's like going to the beach and saying you discovered sand. Had to cancel the whole picnic.
The Trinity River bottoms are nothing but sand. Everyone has always known that. Always.
French utopians knew it in 1855. That's not a joke. It's a fact. In 1855 several hundred French utopians arrived on the west bank of the Trinity River in what is now Dallas, where they established a short-lived colony called La Reunion. One of them, a scientist named Emil Remond, wrote home saying the area would be ideal for brick-making because of the huge amounts of sand in the river bottom.
In 1918 Ellis W. Shuler, a founding faculty member at SMU, wrote a book on the geology of Dallas County saying that the huge sand and gravel deposits along the Trinity River made the region ideal for the manufacturing of cement.
And guess what? Sand and gravel mining along the Trinity River eventually created such a large industry that an area just three miles north of the La Reunion lands became known as "Cement City." Could just as easily have been called "Sand City."
Something's just missing here. Something is not being told to us.
The Corps of Engineers revealed in early April they had ordered a halt to basic construction of the first Calatrava suspension bridge over the Trinity River at the western terminus of the Woodall Rodgers Freeway, after some heavy construction equipment started wobbling around on what turned out to be quicksand.
More recently the Corps ordered the city to carry out a 20-month, $29 million project of core sampling and analysis along the 30-mile Dallas floodway system, citing as one of the reasons the recent discovery of sand near and under the levees.
My colleague Sam Merten and I have both asked the Corps on multiple occasions how it could have approved construction of the Calatrava bridge without knowing about the sand. Kevin Craig, manager of the Trinity River project for the Corps, told me the Corps didn't know about the sand until one very bad day a year ago when a drilling rig boring a 54-inch diameter shaft 90 feet down to bedrock ran into a subterranean layer of flowing sand—sand charged with underground water.
When Merten asked Craig a similar question, Craig said, "We didn't have all the geotechnical data. We approved that with the understanding that we would have geotechnical people on site as they were drilling, and that's where we really found the sand."
No. No. First of all, you don't test the soil by launching the full project—a bridge slated to cost at least $115 million—and then watching to see if it works out. Second of all, the French utopians. Third of all, the Corps did know.
Of course they knew. They're the U.S. Army Corps of Engineers. Look at me. This is serious. In the big report the Corps released April 3 revealing that the Dallas levee system is all screwed up, they referenced a document in the footnotes called, "Seepage Investigation, blah blah blah" dated 1953. I asked for a copy. It took forever. I got a copy.
At the back of the report is a map of the area right where the Calatrava bridge is being built and a log of test borings that the Corps made in July 1952, before rebuilding the Dallas levees. At almost the exact point where the Calatrava bridge is being built now, the log shows a layer of sand beginning five feet beneath the surface of the ground and extending down five more feet in depth.
On top, you have a layer of clay—a cap. Water can't flow through clay. But beneath the clay is sand. Water can move through sand.
This is more than you ever wanted to know about sand, but I have been talking to engineers about it and doing some reading. There are two Trinity Rivers out there—the one we see and a more ancient Trinity, the grandfather of the one we can see, that flows beneath the surface through what are called "water sands."
If you do something radical to change the water pressure in the water sands, like drill a big hole, water will flow through the sand toward the hole you have drilled.
Everybody knows that. I always have difficulty getting construction industry people to talk to me on the record about this project because they don't want to be black-balled from future government projects. But anyone who has done construction anywhere near the Trinity River knows that sand, water sand, flowing sand and collapsing pier shafts are common pitfalls.