Tag Archive for: sand mines

TACA Now Claims Sand Mines Helped to Prevent Flooding Downstream

David Perkins, CEO of TACA (the Texas Aggregate and Concrete Association) now claims that sand mines helped to prevent flooding downstream. The claim appeared in the current issue of Mining Technology in an article titled “Did Sand Mining Exacerbate Flooding During Hurricane Harvey?”

Perkins is quoted as saying, “…what [these sand mines] actually do – in contrast to what people were stating – is that they stored quite a bit of that floodwater and helped to prevent additional flooding …”

He explained how.  “… For example, one 60-acre pit that’s 100 feet deep holds 6,000 acre feet of water. We’ve got some great potential capacity for off-channel storage that we could incorporate into our mining activities.” [Emphasis added twice.]

Did Mines Really Help Prevent Downstream Flooding?

Did they prevent flooding or could they have the potential to do so? Perhaps, but only if they followed best management practices common in other states and countries. More on that later.

Let’s suspend disbelief for a moment and examine Mr. Perkins’ theory.

The pits are already filled with water, so you only have a tiny portion of those acre feet available for storage during a flood! Not as much as he implies. Is the amount significant?

The difference between the top of the water and the top of the dikes is usually 10 to 20 feet at best. So let’s be generous to Mr. Perkins and assume 20. And let’s use the pit below as a test case. It’s 160 acres – about the size of Kingwood’s East End Park so people will have a reference.

Here’s what the same pit looks like from ground level.

Peak flow from Harvey would have filled this pit in less than 8 minutes.

How 8 Minutes was Calculated

The pit above is approximately 160 acres.

  • Assume 20 vertical feet are available to store water.
  • 20 feet x 160 acres = 3200 acre feet of potential storage.
  • Now let’s calculate how fast Harvey would fill that up.
  • Approximately 150,000 cubic feet per second (cfs) flowed through this area.
  • There are 43,560 cubic feet in an acre foot. To find the fill rate…
  • 150,000 cubic feet per second/43,560 = approximately 3.5 acre feet per second
  • To convert seconds to minutes, 3.5 x 60 = 210 acre feet per minute.
  • 1600 acre feet of extra capacity/210 acre feet per minute = 7.6 minutes.
  • Thus, Harvey could have filled 20 feet in this pit in less than 8 minutes.

Did It Delay, Reduce, or Prevent Flooding?

So this pit really wouldn’t have done much by itself to prevent flooding. It delayed flooding on the West Fork for 8 minutes in a 4-day flood. It reduced flow by 3,200 acre feet. But it did little prevent flooding as Mr. Perkins claims. To put things into perspective, the total amount of flow going into Lake Houston would have filled up NRG stadium in 3.5 minutes (see page 7).

Contribution to Flood Reduction if You Put All Mines Together

However, if you consider all the pits on the West Fork together (20 square miles), they might have delayed  flooding by 10 hours according to the same calculations. That’s starting to sound like a significant contribution. Barker and Addicks Reservoirs together store a total of 410,000 acre feet. West Fork sand mines occupy 12,800 acres. If every acre had 20 vertical feet of storage available, you would have 256,000 acre feet of storage. That might not stop Harvey but it could certainly help reduce flooding – especially in smaller floods.

Two Problems Need to Be Addressed with Perkins’ Theory

Mr. Perkins’ theory has two major flaws that would need to be addressed before it could be taken seriously by residents.

That would mean following best management practices common in other states and countries.

Ignoring Best Practices Contributes to Flooding

Regardless of storage POTENTIAL, if mines fail to follow best management practices, they are likely to do more harm than good.

Texas does not enforce best management practices common in other states, such as setbacks from rivers, sloping of dikes, and strengthening of dikes.

In Texas, we locate mines in floodways. And dikes are so thin that they often fail. Case in point: the mine we are talking about. There, dikes have been breached repeatedly. The river has cut through the pit and carried sediment downstream. That sediment then helped clog the river and create floods, not prevent them.

Rather than trying to deny what happened and change the debate, TACA should acknowledge what happened and work with citizen groups and government to create new regulations that protect the public as well as themselves.

What Really Happened in West Fork Mines During Harvey

Here’s what it looked like. This series of photos shows West Fork sand mines during Harvey on 8/30/17, one day after the peak. The river was flowing at only one-third of its peak on this day, according to the San Jacinto River Authority.

West Fork Sand Mine complex inundated by Harvey. Two of the three stockpiles in this photo were decimated by the flood. Sediment from the pits was also picked up by currents within them and carried downstream. Mine used in illustration above is in center. 

Following are several close ups that show water breaching dikes, entering the mine and eroding areas within it and then carrying sediment downstream. All images taken on 8/30/17, courtesy of Google Earth and NASA.

Floodwater broke dikes, captured the sand pit and flowed straight through it.

Rapids within the mine.

Force of floodwater washed out road INSIDE mine. 

Floodwater rushing out of forest into sand mine. It then flowed through and over dikes on the opposite side.

Exit Point for Floodwaters in this Mine

This next image shows the floodwaters exiting the mine on the far side after they scooped up sediment.

Floodwaters exit mine during Harvey. Photo taken on 8/30/2017.

Harvey was not the only flood when this has happened. The Memorial Day flood in 2015 and the Tax Day Flood in 2016 also saw breaches of the dikes. Those floods were much smaller and still caused problems, underscoring the need to modify permitting, regulations and best practices.

Exit point when river captured mine during Memorial Day flood in 2015.

Exit point two months later, on 7/31/2015. Breach was still unprepared and mine was leaking sediment into river.

By March of 2016, the breach had been repaired, but you can also see how sand was building up against it.

Less than a year later, when the flood waters had subsided, we can see the growth and orientation of the sand bars within the mine on the upper left in this 2017 image. This indicates that current within the mines during river capture was forcing sediment out of the mines.

I fail to see how this particular sand mine can prevent flooding. These pictures tell a different story. If the operator and TACA supported best management practices common in other states and countries, they might be able to help prevent flooding. But until that happens, I’m going to call Mr. Perkins’ claim a perfect-world generalization that has real-world limitations and exceptions.

And until TACA and the mines acknowledge the role they have played in flooding, residents will have a hard time emotionally accepting their presence in the community.

As always, these are my opinions on a matter of public interest. 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 11, 2018

347 Days since Hurricane Harvey

Do Local Sand Mines Follow Best Management Practices?

Note: This is the first article in a series on sand mine best management practices. It focuses on insufficient natural buffers between the mines and the San Jacinto river. Subsequent posts will focus on land clearing, site reclamation practices, and more.

A comparison of sand mining actual and best management practices found that performance shortfalls in local mines exacerbate sedimentation in the San Jacinto River, contrary to assertions by the Texas Aggregate and Concrete Association (TACA) that sand mining has environmental benefits.

Proximity of mines to San Jacinto River in non-flood conditions.

TACA claims that when a river floods, the current is so weak that sand and sediment are deposited inside of mines. An analysis of satellite and aerial photos shows, though, that the current is strong enough to break dikes, destroy roads, re-route the river through mines, and carry sediment downstream.

TACA sounds eerily reminiscent of Richard Pryor when his wife caught him in bed with another woman. “Who you going to believe? Me or your lyin’ eyes?”

In at least one case, a broken dike has gone unrepaired for years while pollution continues to escape into the San Jacinto, the main source of water for Lake Houston and millions of people.

Dangers of Sand Mining

Numerous states and countries acknowledge the following risks of sand mining. Most impose regulations on the industry because sand and silt washed downstream from mines can:

  • Impair water quality
  • Increase water treatment costs
  • Impair wildlife and fish habitat
  • Reduce carrying capacity of rivers and streams
  • Reduce the volume of lakes
  • Block drainage ditches
  • Contribute to flooding
  • Impose dredging expenses on taxpayers
  • Ruin recreation

Louisiana: Leader in Communicating Best Practices

The Louisiana Best Management Practices Guide to sand mining is one of the most concise, candid and clearly written guides in the world. Government and industry developed it together. The refreshingly honest introduction states:

  • “Sand and gravel mining operations can potentially cause off-site impacts to water quality if site planning and BMPs are not factored into every aspect of the mining operation.”
  • “…BMPs … should be utilized … to prevent pollutants from leaving the mining operation.”
  • “Siltation is considered the highest nonpoint source priority of concern in wetland areas and the second highest priority affecting lakes (1992 Report to Congress).”
  • “Mining related activities have been estimated to cause 7 percent of the nation’s nonpoint source impacts to lakes and 17 percent to coastal waters.”

Comparing Texas Practices to Other Areas’

Texas does not make it clear what the state’s best management practices (BMPs) for sand mines are. So how do sand mines along the San Jacinto measure up to other states’ and countries’ guidelines? Not well.

One focus of their BMPs is the use of buffer zones, setbacks and strips of vegetation to reduce erosion and control sedimentation. The minimum distance between mine and river in most cases is 100 feet. Some specify more.

  • Alaska, for instance, discourages mines from locating within 1000 feet of a public water source, i.e., the San Jacinto which feeds Lake Houston, the main drinking water source for millions of people. The minimum near other bodies of water in Alaska is 200 feet.
  • Malaysia specifies a 50 meter setback (164 feet) from all river channels.
  • Australia prohibits sand mining in sensitive areas altogether.

In Texas along the San Jacinto, miners often excavate to within 40-50 feet of rivers, and remove vegetation to build dirt roads on the remaining narrow strip between the mine and the river. These thin, sandy barriers provide little defense against floods. They have been repeatedly breached, as you will see below. The river often runs right through mines, carrying sand and sediment downstream.

Types of Barriers against Sedimentation

Louisiana mandates a minimum 100-foot buffer adjacent to perennial streams. The state recommends a dual defense against sedimentation: vegetation and structural measures. Their best practices guide states, “Vegetation is an inexpensive and effective way to protect soil from erosion. It also decreases erosion from flowing water by reducing its velocity. Roots hold soil and increase infiltration. Topsoil should be added where existing soils are not suitable for adequate vegetative growth.”

Vegetative controls include:

  • Maintaining buffer zones between mine and river
  • Sod stabilization techniques. Sodding can be more than 99 percent effective in reducing erosion.
  • Protection of trees involves preserving and protecting selected trees that exist on the site prior to development.
  • Temporary and permanent seeding

Structural controls include:

  • Diversion ridges, berms or channels of stabilized soil
  • Silt fences
  • Sediment basins with banks sloped at 2:1 or less
  • Dikes – Must be well compacted and vegetated, with an outlet pipe or coarse aggregate spillway
  • Riprap protection – at the outlet end of culverts or channels to reduce the depth, velocity and energy of water so that the flow will not erode the receiving stream.
  • Check dams – Small dams less than 2 feet high constructed across swales or drainage ditches to reduce flow velocity and erosion.
  • Aggregate stabilized site entrances – at least 50 feet long to reduce sediment tracked onto public roads. Tire washing may also be needed.
  • Good housekeeping practices for fuel, debris, sediment from unstabilized areas, etc.
  • Post-construction stormwater management measures
  • Retention ponds
  • Vegetated swales and natural depressions that filter sediments from runoff with side slopes of 4:1 or less.

A Visual Comparison

Note the images below. The first represents the ideal; it is taken from the Louisiana BMP guide. The rest are from the West Fork of the San Jacinto in the last three years.

Image of ideal stream bank from Louisiana Sand Mining Best Practices Guide. Note vegetation, grass, gradual slope and aquatic plants.

West Fork Sand Mine,  9/14/2018. During Harvey, 150,000 cubic feet per second came rushing down this narrow channel and flooded 20 square miles of exposed sand in more than a dozen different mines.

Consequences of NOT Following BMPs

The image above and the following images all come from a small area of investigation shown below.

2.1 miles from Northpark Drive and US59, and 3.1 miles upstream from the US59 bridge.

The following images demonstrate what happens when miners work too close to the river. Numbers on the first image correspond to close-ups that follow.

Inundation of sand mines during Harvey on 8/30/17. Numbers correspond to close-ups below.  All photos courtesy of Google Earth.

1 – Rapids within sand mine.

2 – Water rushing into mine, creating turbulence.

3 – Water takes a shortcut across meander through mine.

4 – Washed out road INSIDE sand mine during Harvey. 

5 -Sand bars within sand mine in conjunction with ruptured dikes prove sand was carried downstream. Photo taken on 10/28/2017 (after Harvey).

In a white paper circulated among Texas state legislators called The Societal and Environmental Benefits of Sand Mining. TACA insists, “When [water invades a sand mine during a flood], the velocity of the water slows significantly, losing its ability to keep sediments in suspension and the stream or river begins to deposit its sediment load. When flood waters back into an area where a sand and gravel pit is located, the pit becomes a sediment trap for the flood waters and their sediments.” This series of photos directly refute TACA’s claims.

Why do we allow sand mines to operate in areas that flood repeatedly and violently, so near the drinking water source for millions of people?

Un-repaired Dike Still Leaks Sediment after 3 Years

Are the mines following Best Management Practices? The dike on the right in the images below ruptured in 2015 and still has not been repaired. Note sediment streaming into the West Fork.

Dike ruptured during flood in 2015 (see image below). It continues to spew sediment into the river.

Geologists say that once a river “captures” a sand mine, it repeatedly tries to take that same route in subsequent floods. This is a direct consequence of mining too close to the river. 

Cautionary Advice from India

Sustainable Sand Mining Management Guidelines from India state, “Floodplain Extraction should be set back from the Main Channel. In a dynamic alluvial system, it is not uncommon for meanders to migrate across a floodplain. In areas where sand and gravel occurs on floodplains or terraces, there is a potential for the river channel to migrate toward the pit. If the river erodes through the area left between the excavated pit and the river, there is a potential for “river capture,” a situation where the low-flow channel is diverted though the pit. In order to avoid river capture, excavation pits should be set back from the river to provide a buffer, and should be designed to withstand the 100-year flood… Adequate buffer widths and reduced pit slope gradients are preferred over engineered structures which require maintenance in perpetuity.”

Sand Miners Externalize Costs

Because these West Fork sand mines did not consider violent floods in their design and construction criteria, taxpayers downstream bear the cost of remediation. Dredging of the West Fork will cost tens of millions of dollars – for the initial 2.1 mile phase alone! That doesn’t even include recurring and unnecessarily high costs of water treatment because of turbidity.

Posted 6/24/18 by Bob Rehak

299 days since Hurricane Harvey

 

Where did all the sand come from?

Our San Jacinto River is clogged with sand that impedes the flow of water and contributes to flooding. Where did all the sand come from? When? Under what conditions? Are there ways to reduce the volume of sand coming downstream? As the U.S. Army Corps of Engineers prepares to dredge the San Jacinto for the first time, we should ask ourselves these questions.

The river has eight tributaries that affect the Lake Houston Area: Spring Creek, Cypress Creek, Lake Creek and the West Fork on the west; and Peach Creek, Caney Creek, Luce Bayou and the East Fork on the east. All produce sand naturally.

They send sand downstream at different rates at different times, depending on the location of rainfall within the watershed, the volume of flow, the speed of flow, and management of the flood gates at Lake Conroe.

San Jacinto River Watershed Map. Tributaries affecting the Humble/Kingwood area include: Cypress Creek, Spring Creek, Lake Creek, West Fork, Peach Creek, Caney Creek, East Fork, and Luce Bayou.

Other factors include the percentage of sand content in soil and the health of vegetation along stream banks. Vegetation retains and slows runoff, reducing erosion.

 

The Natural Resources Conservation Service of the USDA produced this soil map of Montgomery County. Blue colors indicate highest percentage of sand; red colors indicate the lowest. Note huge concentrations of sand on Spring Creek and West Fork.

The map above helps us understand why so many sand miners chose to locate along the West Fork – lots of sand. The West Fork is also sparsely populated compared to Spring Creek as you can see in the satellite image below. It shows the sand mines around the Humble/Kingwood area highlighted in red. One is located on Caney Creek (right); the rest are on the West Fork (left).

Satellite image from Google Earth with sand mines around Kingwood outlined in red. Image dated 10/28/2017.

While sand has been coming down the river and streams for thousands of years, rapid sedimentation in the West Fork between Humble and Kingwood didn’t become an issue until the growth of sand mining on the West Fork in the late 1980s.

Notice how most of the areas in red above are filled with natural vegetation in the 1985 image below.

Satellite photo of Kingwood area in 1985 before rapid growth of sand mining. Compare areas in red to previous image.

Today, mines expose approximately 20 square miles of loose sand on the West Fork alone between I-45 and US59.

Aerial photo taken on 9/14/18 of sand mining operation on West Fork.

Dikes around the mines are supposed to keep sand from being discharged into the river. However, Harvey inundated the mines.

Harvey’s floodwaters topped the dikes of sand mines. Image taken 8/30/2017.

An analysis of satellite images before, during and after Harvey shows massive loss of sand from stockpiles within many of these mines.

During floods like Harvey when the SJRA releases water from Lake Conroe, dikes are overtopped and broken. I suspect that sand then comes down the West Fork in tremendous volumes that dwarf Spring Creek’s contribution.

To test this hypothesis, I looked at USGS flow data for both tributaries. I also reviewed all my aerial photos and Google Earth’s historical images.

Under normal conditions, Spring Creek flows at 80 cubic feet per second (cfs) and the West Fork of the San Jacinto at 150 cfs. These are not sufficient flow rates to suspend sediment the size of sand. (For an excellent discussion of sedimentation, see Fundamentals of Sediment Transport at Fondriest.com.)

However, during Harvey, Sring Creek flowed at 78,200 cfs; and the West Fork at  55,000 cfs. Then the San Jacinto River Authority opened the gates at Lake Conroe. That flipped the ratio dramatically. With the flood gates open, Spring Creek still flowed at 78,200 cfs, but the West Fork increased to 130,000 cfs. Flow rates that high can (and did) move houses off their foundations.

Four hundred and fifty aerial photos in the gallery of this web site show a bright, white trail of sand between sand mines and the sand clogging the East and West Forks around Humble and Kingwood. Flood waters swept that sand from a to b. The giant sand deposits at River Grove Park and elsewhere grew exponentially during recent floods.

This tells me that when discussing the origins of the sand, we need to primarily evaluate the river during floods. More water is moving faster under greater pressure. That’s when erosion and deposition happen quickly. That’s when the river overtops and ruptures dikes. And that’s when twenty additional square miles of exposed sand surface on the West Fork make their major contribution to our sediment and flooding problems.

We can’t control sand coming down rivers naturally. However, with better sand mining practices, we may be able to reduce mankind’s contribution to our flooding problem, not to mention the related cleanup costs borne by taxpayers.

In upcoming posts, I will discuss my research into sand mining best practices.

Posted May 22, 2018 by Bob Rehak

266 Days since Hurricane Harvey