Commission Meeting to Discuss Levee Issues in Mercedes
MERCEDES – The International Boundary and Water Commission addressed the public about its plans to repair cracks in the Rio Grande flood control levee.
The meeting took place at the IBWC office in Mercedes. The levee is in place to prevent floodwaters from over taking the area.
The cracks are on the U.S. side of the Rio Grande River between the Gateway International Bridge and Lake Brown. Over the years, they have shifted and opened up.
A year after the U.S. Army Corps of Engineers reviewed it the IBWC contracted Arcadis Engineering to take the engineers’ solution to put plans and specification into place.
When that happened, Arcadis found more issues with the structural integrity of the levee.
"What you have occurring here, you basically have Lake Brown, which is an oxbow, is kind of seeping toward the Rio Grande. You've got a subsurface seepage going on. The other thing that happens is the water in the Rio Grande is controlled by dams. And so when they release the water, the rush of water comes down and it rises quickly in the river, and then drops very quickly in the river. It’s not a great condition for slopes,” Kirk Lowry, an Arcadis engineer, said.
He said because that water gets stuck up in the slope areas of the levee it weakens the soil. He also pointed out that the flaws of the levee came about six months after IBWC widened and slightly raised the levee at the request of FEMA.
Arcadis has identified three plans to stabilize the levee and eliminate the cracks. The plans have to do with creating something similar to concrete columns underground.
Those columns would be from the levee all the way down to the river. Two types of those concrete columns will work but that would mean removing the levee to make that happen, which in turn would mean putting a flood protection plan in place.
The third alternative, which also involves a different method of the concrete columns, will let the engineers keep the levee in place.
IBWC must choose from one of the three plans. Arcadis is recommending the third which involves keeping the levee.
No word yet when IBWC will make their decision. Arcadis said if they choose the third option it will take anywhere from seven to nine months to complete.
Plans Presented to Help Levee:
1 - First plan is deep soil mixing. Deep soil mixing involves taking an auger, making a hole in the ground and injecting cement mixed with soil to create a concrete-like column structure. It is much stronger than soil. This will create resistance to the failure surface of the levee. These concrete columns will be placed from along the levee all the way down to the river.
2 - The second plan is similar to deep soil mixing only without cement and soil. The hole made by the auger will be filled with stone.
3 - The third option is to combine deep soil mixing and stone columns. This would not require engineers to remove the levee.
* Both the first and second plans would require IBWC to remove the levee, which would also require a flood protection to be put in place.