The Liberty Materials Mine in Conroe on the West Fork of the San Jacinto was cited last month for allegedly discharging 56 million gallons of wastewater loaded with up to 25 times the normal amount of sediment. When we look at the issue of sediment in the river and how it affects flooding, such breaches contribute to the problem. But it’s not just what such sand mines discharge. It’s also about what the wetlands they were carved from don’t hold back any more.
Before there was a Liberty Materials in Conroe, the area they now occupy contained many densely forested wetlands. Now there is nothing to slow down the water during heavy rains. Much more sand and sediment are exposed. And the wetlands are no longer there to filter it. It’s a double whammy. We get it coming and going.
Before Liberty, Abundant Wetlands
Visually, it appears that wetlands once covered roughly half the area of this mine. But what was actually there?
US Geological Survey (USGS) and US Fish and Wildlife Service (USFWS) use a five character alpha-numeric code to classify wetlands. Liberty Materials operates in areas that were classified as PFO1A and PEM1A.
P stands for the class: Palustrine. Palustrine wetlands include any inland wetland that lacks flowing water. The word palustrine comes from the Latin word palus or marsh. Wetlands within this category include inland marshes, swamps and floodplains covered by vegetation.
The second two letters in each case stand for the subclass: FOrested or EMergent. Forested means it had broad-leaved, deciduous trees or shrubs taller than 6 meters. Emergent means it had aquatic plants.
These were areas that could store large volumes of water during floods. Plus, they had vegetation that could suck it up.
Trees Soak Up Water, Too
Trees can soak up 50 to 300 gallons of water in a day depending on their size, age and type. They send it back into the atmosphere; let’s use 100 gallons as a conservative average and do some simple math to calculate their contribution to flood reduction.
It’s difficult to estimate the number of trees per acre; it depends on the factors mentioned above plus more. But some people use 500 trees per acre as a good average for estimating purposes.
The Liberty sand mine complex comprises more than a thousand acres. That’s 500,000 trees each soaking up 100 gallons of water per day. Or 50 million gallons of water per day.
That’s about the same amount that the TCEQ estimates the Liberty Mine discharged downstream in one breach.
Personally, I’d rather have the trees and wetlands than white water and a river that’s so silted up it contributes to flooding.
Influence of Wetlands on Flooding
Imagine a sand box that’s 1.5 miles wide and 2.5 miles long. Here’s what it looked like the day after the peak of Hurricane Harvey.
And here’s why. Note how closely the extend of flooding matches the extent of the flood plains. Like almost all mines on the West Fork, this one lies substantially within the floodway and floodplain.
Is Liberty’s Luck Running Low?
If these people had the strongest dikes in the world, maybe you could cut them some slack. But they don’t. They breach repeatedly.
We need sand, but not at the expense of floods and the environment. Maybe it’s time for TACA to run some of its members out of Texas. That do-good routine they stage in Austin every other year could be in jeopardy with members like Liberty. See below.
Posted by Bob Rehak on 12.5.2019
828 Days since Hurricane Harvey
The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.