In the next two months, I expect to see legislation filed that will strengthen regulations on sand mining. Hopefully, legislation will prevent dangerous practices by the mining industry that have put residents at risk in the past.
Perhaps we can compromise on legislation that lets miners exercise their property rights without harming the property rights of others…or their incomes, safety, and families.
This is another post designed to raise awareness of sand mining problems and how other states have solved them. One of the main problems with sand mining in Texas: virtually all miners locate their mines in floodways. That almost guarantees a phenomenon called pit (or river) capture. Washington State has discovered the following about pit capture.
Causes of Pit Capture
Sand-pit capture happens when pressure from floodwater breaks through dikes and takes a short cut across sand mines instead of following the river’s course. A scientific paper called “Flood Plains, Salmon Habitat, and Sand and Gravel Mining” by David Norman and C. Jeff Cederholm describes the process. The paper, published in Washington Geology by their Department of Natural Resources, says pit capture is almost inevitable in the long term.
“Regardless of the best planning and intentions, impacts of flood-plain mining may simply be delayed until the river is captured by the … pit,” they say. “While capture may not occur in the next 100-year flood event, it is likely to occur in the future as development and consequent flood magnitude increase. In the long term, stream capture by (sand and) gravel pits is a near certainty.”
Consequences of Pit Capture
The paper cites more than three dozen examples of pit capture. Consequences include:
- Lowering the river bed upstream and downstream of mining operations
- River bed erosion and (or) channel incision
- Bank erosion and collapse
- Undercutting of levees, roads, bridge supports, pipelines, utility towers and other structures
- Increasing suspended sediment
- Deposition of silts
I have described how those consequences happen in several previous posts. Also, the paper describes the processes in detail, so I will not repeat the explanations here.
As in Washington, the Houston area has had many instances of sand-mine pit-capture.
Video Shows Simulation of Pit Capture
This short YouTube video may help you visualize how this process works. A company called Little River made it with funding from the EPA and State of Missouri. Little River specializes in table-top, tank experiments for science classes. This video shows how pit capture happens and how erosion results.
Depending on the area and depth of the pit, and sediment volume carried by the river, it could take “millennia” to restore the natural environment after pit capture.
Operators’ attempts to prevent pit/river capture by armoring dikes and channelizing rivers often accelerate floodwaters and increase erosion downstream, say the authors (page 13 and figure 17) .
Cures for Pit Capture
The Washington State Department of Ecology Shoreline Management Handbook recommends locating mining activities “outside the shoreline jurisdiction.” They recommend 200 ft. from the floodway or off the 100-year flood plain. The latter coresponds to Texas regulations for the John Graves Scenic Riverway District on the Brazos River.
Immediate Reclamation for Each Segment
The Washington State Department of Natural Resources administers their Surface Mine Reclamation Act (RCW 78.44). It generally requires reclaiming mines immediately after each segment is mined. The 1993 revision of this law requires that most mines in flood-plain environments be reclaimed as beneficial wetlands.
Avoiding pit capture requires thorough and immediate reclamation because of river migration. The longer a pit goes before reclamation, the greater the likelihood that river migration will capture it. We saw an example of that on the San Jacinto. The river is migrating 12 feet per year and is 38 feet away from breaking into a major sand pit.
The immediate reclamation requirement could benefit Texans. Texas law requires sand miners to file a reclamation plan to obtain a permit. However, there is no requirement to execute the plan before leaving the property. Many simply walk away from their obligations, much to the detriment of surrounding property owners and the safety of the public. Requiring miners to reclaim one section of a mine before permitting another would give them a powerful incentive to reclaim land.
Safeguards for Flood-Plain Mining if Necessary
The authors conclude: “If mine plans call for sites on flood plains, then wide, topographically higher, and thickly vegetated buffers should be considered as a means of reducing the probability of river avulsion in the near term. However, in most instances, buffers only delay the inevitable.:
“Determining an adequate distance between the flood-plain mine pit lake and the river will depend on understanding the rate of river meandering and the risk of avulsion.”
As always, these are my opinions on matters of public policy. They are protected by the First Amendment of the United States Constitution and the Anti-SLAPP statutes of the Great State of Texas.
Posted by Bob Rehak on August 13, 2018
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