Last night, I read a strangely moving 125-page white paper titled Freshwater Gravel Mining and Dredging Issues. It was authored by G. Mathias Kondolf, Matt Smeltzer and Lisa Kimball of UC Berkeley for the Washington Department of Fish and Wildlife, Washington Department of Ecology, and Washington Department of Transportation in 2001. Despite “Gravel” in the name, the paper is an encyclopedic review of the scientific literature that surrounds both sand and gravel mining in all of their various forms (river, flood plain, wet, dry, bar scalping, in-stream sand traps, etc.).
It’s a virtual primer on how aggregate mining affects rivers, infrastructure, the water table, people and the environment. The study argues that many of the impacts of sand and gravel mining are never reflected in the cost of the products because government, in effect, subsidizes them. The authors also argue that if the full costs of mining were reflected in the price of aggregate, that we might be producing it in ways that were safer.
About the Author(s) and Focus
The lead author, Kondolf, is Professor of Landscape Architecture and Environmental Planning at Berkeley. He specializes in hydrology, environmental geology, environmental impact assessment, and riparian zone management with an emphasis on stream channel processes as they relate to natural resource management. Kondolf’s research is widely cited in scientific literature concerning sand and gravel mining.
While a large part of this white paper discusses aggregate mining’s impacts on salmon, it also addresses issues related directly to humans.
Sources for Aggregate and Their Cost
“Sand and gravel deposited by fluvial processes are used as construction aggregate for roads and highways (base material and asphalt), pipelines (bedding), septic systems (drain rock in leach fields), and concrete (aggregate mix) for highways and buildings.
Page 21 discusses two primary sources of construction aggregate. In many areas, aggregate is derived primarily from alluvial deposits, either from pits in river floodplains and terraces, or by in-channel (instream) mining, removing sand and gravel directly from river beds with heavy equipment.” The primary type of mining done in the Houston area is floodplain mining. However, the industry is beginning to push mining in rivers as a way to reduce excess sedimentation. (Ironically, many governments see floodplain mining as the answer to the dangers of river mining.)
Pages 22 and 23 discuss another novel source: reservoir deltas (much like the West Fork of the San Jacinto between US59 and FM1960). “Extraction of reservoir deposits serves to restore some (albeit a small fraction) of the reservoir capacity lost to sedimentation.” However, in the late 1990’s and early 2000’s, the cost of building new reservoirs in California was approximately $3,000/acre foot, while the cost of mechanically removing sediment from old reservoirs was $20,000/acre foot, almost 7X more.
“The economic value of avoiding further reservoir capacity loss could be a significant factor making removal more economically attractive in the future, especially if the environmental costs of instream and floodplain mining become better recognized and reflected in the prices of those aggregates.”
Kondolf, et al. also discuss other potential sources of aggregate such as recycled concrete. “Recycling concrete rubble not only avoids environmental impacts of new aggregate production, but avoids impacts of disposing the rubble as well.” Further, they found that the quality of recycled concrete could meet half of current aggregate uses.
Abandoned concrete crushing facility on North Houston Avenue in Humble.
Dangers Associated with Floodplain Mining
“As in-channel mining is increasingly discouragedor prohibited, mining of floodplain pits is encouraged as a less damaging alternative,” say the authors. However, there is no shortage of dangers associated with floodplain mining. The authors catalog those.
Where mines intersect the water table, dangers include:
Lowering of alluvial water table
Loss of wells
Loss of riparian vegetation
Prevention of seedlings from establishing
Die-off of trees
Reduced summer base flow in rivers
Increased water temps in river during summers due to shallower water
Fish kills due to river lowering
Increase in evaporative losses.
During excavation, if floodplain pits are kept dry by pumping, they:
Lower local water tables
Potentially dewater nearby tributary channels
Desiccate riparian vegetation and floodplain wetlands.
Floodplain pits are often accompanied by channelization to maximize the floodplain area accessible for mining and to prevent the channel from eroding into pits. Miners may straighten channels and stabilize banks with rip rap. Even when successful in keeping pits “isolated,” the principal biological effects of floodplain and terrace-pit mining include:
Conversion of riparian forest to open pond habitat
Reduced habitat complexity in the channel
Loss of dynamic channel migration processes due to levees and bank protection
Lack of natural channel banks
Loss of riparian vegetation along hardened banks
Changes in the hyporheic zone dynamics potentially affecting stream water temperature and water quality
Increased potential for contamination of the alluvial aquifer due to the operation of equipment
Spills and the direct route to groundwater through the pit
Loss of floodplain wetlands
Dewatering of tributaries due to lowered water tables.
Pit Capture Inevitable
Often old pits are used to settle fines. Once filled, the pits act as fine sediment plugs in the floodplain. “Subsequent channel migration can erode these, releasing concentrated fine sediments into the channel,” say the authors.
After off-channel pits“inevitably”(authors’ wording)become captured by the channel, other impacts often result:
Bed and bank erosion upstream and downstream
Potential loss of infrastructure, such as roads and bridges, through “head cutting”
Bank erosion
Property destruction
Excessive downstream sedimentation
The authors claim capture is inevitable for floodplain pits, though not necessarily for terrace pits, which are usually higher in elevation and farther from the channel. Pit capture is most rapid when:
The pit lies inside of a meander
The upstream end of the pit is much lower than the adjacent channel
The river floods, creating a pressure difference inside and outside of pits that causes dikes to collapse.
Captured pits become lakes within the river, transforming lotic (moving water) environments into lentic (still water) environments, thereby inducing changes in the ecology of the reach.
In the Naugatuck River, Connecticut, captured pits have become lakes with seasonally stagnant water and low oxygen levels. Authorities there expect the pits to persist for hundreds of years.
“Moreover, channel incision and instability induced upstream of captured gravel pits could trigger other pit captures, resulting in widespread and long-term cumulative effects,” say the authors.
Reclamation Costs
Floodplain pits, when abandoned without remediation, “can be viewed as substantial liabilities for future generations, either to maintain their separation from the current channel, or if already breached, to suffer consequences of resultant channel incision … or to pay the price of re-isolating the breached pits.” They also pose safety hazards because of their steep sides.
On page 95, Kondolf et al. cite the costs of several public projects which became necessary after miners had abandoned pits. “The actual costs of isolating gravel pits will depend, of course, upon the surface area extent, excavation depth, and geometry of the pit and channel, as well as the availability and cost of suitable fill material. Experience to date in the Central Valley of California suggests that the costs … have been around $3-4 million per pit, although all these projects use dredger tailings available nearby” (and the costs are in 2001 dollars).
Decommissioning Costs Should Be Paid Upfront
“…pit isolation is a costly exercise, and given the likelihood of pit capture, these costs of “decommissioning” should probably be taken into consideration when permits for the gravel pits are initially awarded. It would be an interesting exercise to estimate the value of gravel extracted from these pits during their period of commercial operations compared to the current costs of reclamation.”
Alternative Sourcing Dependent on Full-Cost Accounting
Future regulation of aggregate mining should emphasize incentives to use alternative sources, such as … reservoir deltas, quarries and recycled concrete rubble. There is currently little incentive to use alternate sources. They generally require higher transport or production costs than aggregate taken from channels and floodplains.
Because the full costs of extracting aggregate from rivers and flood plains are not incorporated in the price paid for the product, it will be difficult to encourage use of alternatives. In effect, extraction of river/floodplain aggregate is subsidized.
Another study by M.D. Harvey and T.W. Smith found that the cost of mining-induced infrastructure damage was equivalent too $3/ton in a California river.* That’s equivalent to about $4.50/ton in today’s dollars.
Neither does the price of aggregate reflect the cost of dredging, which was necessitated here in part by the choice to locate mines in floodways. Dredging costs for Phase 1 of the West Fork already exceed $70 million. Phase 2 could easily cost another $100 million – all borne by taxpayers.
If such costs were incorporated into the price of river and flood plain aggregate, alternatives might look much more attractive.
*Gravel Mining Impacts on San Benito River, California. In: Proceedings of 1998 International Water Resources Engineering Conference, Hydraulics Division, ASCE, Memphis, TN, August 1998.
Posted by Bob Rehak on August 7, 2018
435 days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2018/11/SandMineHumble_27.jpg?fit=1500%2C1000&ssl=110001500adminadmin2018-11-07 19:34:492018-11-08 08:29:50Why We Need Full-Cost Accounting for Aggregate Mining
Scientific literature from around the world has identified both immediate and long-term risks associated with sand and gravel mining. These risks underscore the need for tighter regulation of the sand mining industry in Texas, where the industry does not follow best practices commonly accepted in other states and countries. Yet some miners here are pushing to start mining rivers (as opposed to flood plains where they mine now).
Why Don’t We Just Let Them Mine the River?
When looking at all the sediment in the San Jacinto, it’s logical to think, “Why don’t we just let sand miners mine the river?” However, many countries in the world have outlawed the practice of river mining, largely because of the dangers of over-mining. If Texas explores this solution, experience has shown that it should be under strict governmental supervision to prevent excesses which have widened rivers, damaged properties and destroyed the river environment elsewhere.
Sedimentation in the East Fork of the San Jacinto. This dune constricts the conveyance of the river by approximately 50 percent. It would be a likely target for river miners. But where would they mine after such obstructions are removed?
River mining differs from the type of remedial dredging that we are doing now. The objective for river mining is to maximize profit, which often means pushing limits. The motivation for dredging is to maximize profits by staying within the limits outlined by the client (i.e., the U.S. Army Corps of Engineers).
“Evidence of environmental problems associated with river sand and gravel extraction is increasing. So also is the community’s expectation of river systems. Future management decisions must be based on the principle of sustainable development – sustainability not only of the sand and gravel resources but also of other river uses and values.”
The discussion of risks begins with an admonishment. “Management of sand and gravel extraction must ensure that the activity does not conflict with the aims of other component policies.” For instance, they say that, “Wild and scenic rivers, wetlands and designated recreational areas are all places where sand and gravel extraction would have a highly visible and adverse impact. Extraction should not be considered in such areas.” (Sec. 6.1.1, Page 16.)
“Increased rates of river erosion and other channel changes can occur in the shorter term, due to both natural and human-induced changes. These changes include increases in the size, magnitude and frequency of floods…” (Sec. 6.1.3. Page 17.)
“…excavation below existing bed level may be a direct cause of bank collapse.” (Sec. 6.1.4. Page 19.)
“Most of the finer sediments (sand, silt and clay) released from erosion of alluvial banks will be transported downstream, often for considerable distances. Increased siltation in these downstream areas can cause problems to navigation … and adversely impact flooding in the area.” (Sec. 6.1.5. Pages 19-20.) The U.S. Army Corps of Engineers found an increase in flood risk from sedimentation in its value engineering study on the West Fork last spring.
“If extraction is below the riverbed level, groundwater recharge from rivers to floodplain aquifers may be severely reduced. This will impact adversely on bores and wells in the area.” (Sec. 6.1.6. Page 20.)
“Extraction of river sand and gravel often involves direct clearing ofvegetation (that stabilizes soil). … Construction of access tracks and processing sites associated with the extraction process can also involve clearing of vegetation.” (Sec. 6.1.7. Page 20.)
“Suspended solids adversely affect many waterusers and ecosystems. They can significantly increase water treatmentcosts, especially where they act as a substrate for bacteria and so increasethe problems and costs of disinfection in water treatment plants.” (Sec. 6.1.9. Page 20.)
“There will be some rivers, however, where the value to other users will be such that extraction may need to be precluded. Similarly, where past extraction has over-taxed a river system, future extraction may need to be precluded until the river has recovered sufficiently, if it does so at all.” (Sec. 6.1.12. Page 22.)
What to Do
The Australian report then goes on to talk about the need for sand and gravel to support road building and economic growth. (Sec. 6.2).
Section 6.3 talks about alternative sources for sand and gravel.
Section 6.4 talks about governmental costs to monitor sand and gravel extraction.
Section 7 talks about guidelines for safe extraction when mining in rivers and how to crack down on illegal activity (something we desperately need to do here as well). Here they talk about the opportunity to involve community members as extra pairs of eyes and the need to enroll major purchases (such as TxDoT) in the enforcement effort.
Section 8 talks about permitting procedures.
Section 9 talks about performance measures and monitor programs. Here they have some novel measures that we could learn from. I especially like Section 9.3, Community Monitoring. Inputs include:
Data collected by local community groups including extractors;
Reports by local ‘care’ groups and riparian landowners;
Reports by local environmental or recreational interest groups;
Reports by local TCM Committees;
Reports by local government.
Such an inclusive approach helps guarantee that the needs of various interest groups are balanced.
Australian Conclusions: A Cautionary Tale
Section 10, the Conclusion, says on page 36: “There are many natural causes which may increase the rate of riverbed and bank erosion. However, extraction of large amounts of sand and gravel from within the channels has exacerbated the situation in many rivers.Past experience in some areas of the State has shown that crisis point can be reached. In other areas, increasing conflict with other river uses has made extraction of sand and gravel a less viable option.”
If the State of Texas decides to permit river mining, I sincerely hope we can find a workable balance for the San Jacinto that protects everyone’s interests.
Posted by Bob Rehak on 11/5/2018
433 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2018/03/Harvey-SanJac_323-e1524608786151.jpg?fit=1985%2C940&ssl=19401985adminadmin2018-11-05 21:30:122018-11-05 21:35:47Immediate and Long-Term Risks Associated with River Sand Mining
Note: If you are from Harris County, you cannot vote in this election, but it still affects you. Please forward this link to friends in Montgomery County. This is an update of a previous post and recommends some candidates at the end.
Next Tuesday, Montgomery County voters will elect board members to the Lone Star Groundwater Conservation District (LSGCD) for the first time ever. Some candidates advocate using more groundwater, a move that could give residents cheaper water in the short run, but which could also cause subsidence and contribute to flooding in the long run. It could even create shortages, raise water costs and limit growth. Here’s how.
How Subsidence Can Increase Flood Risk
When ground subsides, it sinks. In this region, the primary cause is groundwater removal.
“Using surface water instead of groundwater reduces subsidence. Where groundwater use has been reduced, subsidence has generally ceased,” said Michael Turco, General Manager of the Harris-Galveston Subsidence District.
Southern Montgomery County, and northern and northwestern Harris County have some of the highest subsidence rates in the region today.
Yet some Montgomery County voters advocate removing more ground water because, at this moment, it’s cheaper than surface water. They are betting their future and their neighbors’ futures on it.
One part of Baytown, the Brownwood subdivision, is a classic, visually striking, and cautionary example of subsidence. Brownwood subsided so much that it became uninhabitable. Excessive groundwater pumping by industry around Galveston Bay caused the area to sink ten feet.
In 1944, the area that would become Brownwood in Baytown was starting to show signs of development.
By 1978, Brownwood was well developed…and sinking fast. Then, in 1983, a 12-foot storm surge from Alicia destroyed the entire community.
Today, Brownwood floods so muchthat all homes are gone. Baytown converted what was left into a park.
Coastal vs. Differential Subsidence
Inland areas also face flood threats from subsidence, but not the kind associated with storm surge. In Montgomery County and surrounding areas, the flood threat comes from sinking at different rates in different places.
Example: subsidence around Jersey Village created a “bowl” within the landscape that has been linked to increased flooding there. See the contour map below.
Other examples: The Woodlands and Kingwood sank two feet in the last century. Most of Buffalo Bayou sank eight.
Red contours show subsidence in last century. Blue contours show subsidence in first 16 years of this century. Note how the small red circle near Jersey Village (A) quickly expanded to the large blue circle around it. Also note (B) the widening gap between red and blue at the top of the frame. This shows that areas that depend on groundwater, i.e., Montgomery County, are subsiding faster than those on surface water, i.e., most of Harris County. Source: Harris-Galveston Subsidence District.
Three Ways Unequal Subsidence Increases Flood Risk
Unequal sinking contributes to flooding by changing the slope of rivers and streams.
If the slope increases, water flows faster and contributes to flooding downstream.
If slope decreases, water moves more slowly or even pools, contributing to flooding upstream.
Sinking between two drainage basins can even divert floodwater from one basin to another.
The “Pump-Now, Let-Somebody-Else-Pay-Later” Mentality
Subsidence happens so slowly that some people claim it’s not a problem – especially those on higher ground. They want to continue pumping water from wells because they perceive it to be cheaper than surface water.
It can be – at least in the short run– until wells run low or dry. Then pumping costs increase – often along with salinity – and the people who depend on the well are out of water and out of luck.
Much of the groundwater in Montgomery County used for human consumption is pumped from the Jasper aquifer which also affects Harris and Galveston Counties. Source Harris-Galveston Subsidence District.
And that high ground they enjoyed? If it subsides faster than surrounding areas, they can alter the slope of rivers and creeks, increasing their own flood risk, like Jersey Village. This is currently happening in southern Montgomery County and northern Harris County.
Depleting at More Than 500X the Recharge Rate
Still, some people say, “I’ll worry about that when it becomes a problem.”
Problem is:
We’re depleting aquifers much faster than they’re recharging.
That means it could take 26,880 years (10 x 12 x 224) to replace the Jasper groundwater that residents will use in just 50 years.
The rate of depletion will exceed the rate of recharge by more than 500X – an environmental catastrophe.
More Expensive in Long Run
Now consider this. Experience and science show that pressure in an aquifer will decrease when pumping exceeds the recharge rate. And as pressure in an aquifer decreases, the cost of bringing water to the surface increases dramatically. Then recovery is no longer economical, i.e., competitive with surface water. It’s like the oil industry. As a rule of thumb, half the oil in reservoirs is left underground. It’s simply too expensive to recover because of low pressure.
For all these reasons, most counties in the region are trying to switch people to surface water. Groundwater withdrawals in Waller, Liberty, Grimes, Walker and San Jacinto Counties have either declined or stayed the same since 2000.
Counties surrounding Montgomery have either decreased groundwater pumping or kept it steady.
Montgomery County groundwater pumping virtually tripled in the last three decades.
Montgomery County Growth
The surge in Montgomery County groundwater usage is largely because of growth. On a percentage basis, Montgomery County is growing faster than any county in the region except Fort Bend.
Montgomery County growth trails only Fort Bend.
So Why Worry NOW?
Water resources take so long to develop that they need to be planned 50 years ahead. If Montgomery County hopes to keep growing rapidly, where will water come from to support that growth? Especially if voters undermine financial viability of the half-billion-dollar, surface-water treatment plant – that they just built – by shifting back to groundwater!
The San Jacinto River Authority (SJRA) finished the plant in 2015 to comply with the LSGCD requirement to reduce groundwater use. Many people don’t realize that the SJRA pumps groundwater from 38 wells to supply The Woodlands. The SJRA must comply with LSGCD regulations like everyone else.
To comply, the SJRA and 90 other water utilities who partnered with them, drew up plans for a surface water treatment plant and signed contracts to purchase water from it. The SJRA then borrowed money from the State and built the plant. Inevitably, the cost of water increased to cover construction.
After it was built, several providers changed their minds and began pushing the LSGCD board to produce more groundwater to take costs back down. When the board refused, the breakaway faction succeeded in getting a measure on November’s ballot to elect an LSGCD board more favorable to groundwater pumping.
Since 2001, the LSGCD has had a nine-member board appointed by a combination of local entities. They include Montgomery County, cities, and MUDs. The SJRA even has one seat. The appointees are experts who fully understand the future consequences of subsidence and unlimited groundwater pumping; an elected board may not.
If an elected board ignores the science and allows unlimited groundwater pumping, it would affect the financial projections on which the surface water plant was built.
Betting the Future
If people vote for candidates who advocate using “cheaper” groundwater in the short term, they will also be voting for subsidence and policies that limit long-term growth. Without question, they will be betting their future, their children’s futures and their neighbors’ futures on a rapidly depleting water source.
If that’s the will of the people, so be it. I just hope they don’t set a precedent that residents in neighboring counties follow. If so, we could all be sunk.
Candidates Who Believe in Science-Based, Groundwater Management
Fortunately, there are people running for LSGWCD board positions who believe in science-based, groundwater management. Knowledgeable acquaintances in Montgomery County recommend the following candidates who, they say, have professional experience related to water management and/or water supply, and would work to preserve Montgomery County’s future, reduce subsidence and prevent flooding:
Place 1, County Precinct 1 – Stuart Taylor
Place 2, County Precinct 2 – Garry Oakley
Place 3, County Precinct 3 – Rick Moffatt
Place 4, County Precinct 4 – Gail Carney
Place 5, County At Large – Gregg Hope
Place 6, Conroe – Jackie Chance, Sr.
Place 7, The Woodlands – Kent Maggert
Please spread the word to every voter you know in Montgomery County.
Posted by Bob Rehak, November 3, 2018
431 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2018/11/5-Subsidence-Contour-Map-e1541284423714.jpg?fit=1500%2C1289&ssl=112891500adminadmin2018-11-03 18:49:582018-11-03 19:00:50Subsidence, Flooding and the Lone Star Ground Water Conservation District Election
Why We Need Full-Cost Accounting for Aggregate Mining
Last night, I read a strangely moving 125-page white paper titled Freshwater Gravel Mining and Dredging Issues. It was authored by G. Mathias Kondolf, Matt Smeltzer and Lisa Kimball of UC Berkeley for the Washington Department of Fish and Wildlife, Washington Department of Ecology, and Washington Department of Transportation in 2001. Despite “Gravel” in the name, the paper is an encyclopedic review of the scientific literature that surrounds both sand and gravel mining in all of their various forms (river, flood plain, wet, dry, bar scalping, in-stream sand traps, etc.).
It’s a virtual primer on how aggregate mining affects rivers, infrastructure, the water table, people and the environment. The study argues that many of the impacts of sand and gravel mining are never reflected in the cost of the products because government, in effect, subsidizes them. The authors also argue that if the full costs of mining were reflected in the price of aggregate, that we might be producing it in ways that were safer.
About the Author(s) and Focus
The lead author, Kondolf, is Professor of Landscape Architecture and Environmental Planning at Berkeley. He specializes in hydrology, environmental geology, environmental impact assessment, and riparian zone management with an emphasis on stream channel processes as they relate to natural resource management. Kondolf’s research is widely cited in scientific literature concerning sand and gravel mining.
While a large part of this white paper discusses aggregate mining’s impacts on salmon, it also addresses issues related directly to humans.
Sources for Aggregate and Their Cost
“Sand and gravel deposited by fluvial processes are used as construction aggregate for roads and highways (base material and asphalt), pipelines (bedding), septic systems (drain rock in leach fields), and concrete (aggregate mix) for highways and buildings.
Page 21 discusses two primary sources of construction aggregate. In many areas, aggregate is derived primarily from alluvial deposits, either from pits in river floodplains and terraces, or by in-channel (instream) mining, removing sand and gravel directly from river beds with heavy equipment.” The primary type of mining done in the Houston area is floodplain mining. However, the industry is beginning to push mining in rivers as a way to reduce excess sedimentation. (Ironically, many governments see floodplain mining as the answer to the dangers of river mining.)
Pages 22 and 23 discuss another novel source: reservoir deltas (much like the West Fork of the San Jacinto between US59 and FM1960). “Extraction of reservoir deposits serves to restore some (albeit a small fraction) of the reservoir capacity lost to sedimentation.” However, in the late 1990’s and early 2000’s, the cost of building new reservoirs in California was approximately $3,000/acre foot, while the cost of mechanically removing sediment from old reservoirs was $20,000/acre foot, almost 7X more.
Kondolf, et al. also discuss other potential sources of aggregate such as recycled concrete. “Recycling concrete rubble not only avoids environmental impacts of new aggregate production, but avoids impacts of disposing the rubble as well.” Further, they found that the quality of recycled concrete could meet half of current aggregate uses.
Abandoned concrete crushing facility on North Houston Avenue in Humble.
Dangers Associated with Floodplain Mining
“As in-channel mining is increasingly discouraged or prohibited, mining of floodplain pits is encouraged as a less damaging alternative,” say the authors. However, there is no shortage of dangers associated with floodplain mining. The authors catalog those.
Where mines intersect the water table, dangers include:
During excavation, if floodplain pits are kept dry by pumping, they:
Floodplain pits are often accompanied by channelization to maximize the floodplain area accessible for mining and to prevent the channel from eroding into pits. Miners may straighten channels and stabilize banks with rip rap. Even when successful in keeping pits “isolated,” the principal biological effects of floodplain and terrace-pit mining include:
Pit Capture Inevitable
Often old pits are used to settle fines. Once filled, the pits act as fine sediment plugs in the floodplain. “Subsequent channel migration can erode these, releasing concentrated fine sediments into the channel,” say the authors.
After off-channel pits “inevitably” (authors’ wording) become captured by the channel, other impacts often result:
The authors claim capture is inevitable for floodplain pits, though not necessarily for terrace pits, which are usually higher in elevation and farther from the channel. Pit capture is most rapid when:
Captured pits become lakes within the river, transforming lotic (moving water) environments into lentic (still water) environments, thereby inducing changes in the ecology of the reach.
In the Naugatuck River, Connecticut, captured pits have become lakes with seasonally stagnant water and low oxygen levels. Authorities there expect the pits to persist for hundreds of years.
“Moreover, channel incision and instability induced upstream of captured gravel pits could trigger other pit captures, resulting in widespread and long-term cumulative effects,” say the authors.
Reclamation Costs
Floodplain pits, when abandoned without remediation, “can be viewed as substantial liabilities for future generations, either to maintain their separation from the current channel, or if already breached, to suffer consequences of resultant channel incision … or to pay the price of re-isolating the breached pits.” They also pose safety hazards because of their steep sides.
On page 95, Kondolf et al. cite the costs of several public projects which became necessary after miners had abandoned pits. “The actual costs of isolating gravel pits will depend, of course, upon the surface area extent, excavation depth, and geometry of the pit and channel, as well as the availability and cost of suitable fill material. Experience to date in the Central Valley of California suggests that the costs … have been around $3-4 million per pit, although all these projects use dredger tailings available nearby” (and the costs are in 2001 dollars).
Decommissioning Costs Should Be Paid Upfront
“…pit isolation is a costly exercise, and given the likelihood of pit capture, these costs of “decommissioning” should probably be taken into consideration when permits for the gravel pits are initially awarded. It would be an interesting exercise to estimate the value of gravel extracted from these pits during their period of commercial operations compared to the current costs of reclamation.”
Alternative Sourcing Dependent on Full-Cost Accounting
Future regulation of aggregate mining should emphasize incentives to use alternative sources, such as … reservoir deltas, quarries and recycled concrete rubble. There is currently little incentive to use alternate sources. They generally require higher transport or production costs than aggregate taken from channels and floodplains.
Another study by M.D. Harvey and T.W. Smith found that the cost of mining-induced infrastructure damage was equivalent too $3/ton in a California river.* That’s equivalent to about $4.50/ton in today’s dollars.
Neither does the price of aggregate reflect the cost of dredging, which was necessitated here in part by the choice to locate mines in floodways. Dredging costs for Phase 1 of the West Fork already exceed $70 million. Phase 2 could easily cost another $100 million – all borne by taxpayers.
*Gravel Mining Impacts on San Benito River, California. In: Proceedings of 1998 International Water Resources Engineering Conference, Hydraulics Division, ASCE, Memphis, TN, August 1998.
Posted by Bob Rehak on August 7, 2018
435 days since Hurricane Harvey
Immediate and Long-Term Risks Associated with River Sand Mining
Scientific literature from around the world has identified both immediate and long-term risks associated with sand and gravel mining. These risks underscore the need for tighter regulation of the sand mining industry in Texas, where the industry does not follow best practices commonly accepted in other states and countries. Yet some miners here are pushing to start mining rivers (as opposed to flood plains where they mine now).
Why Don’t We Just Let Them Mine the River?
When looking at all the sediment in the San Jacinto, it’s logical to think, “Why don’t we just let sand miners mine the river?” However, many countries in the world have outlawed the practice of river mining, largely because of the dangers of over-mining. If Texas explores this solution, experience has shown that it should be under strict governmental supervision to prevent excesses which have widened rivers, damaged properties and destroyed the river environment elsewhere.
Sedimentation in the East Fork of the San Jacinto. This dune constricts the conveyance of the river by approximately 50 percent. It would be a likely target for river miners. But where would they mine after such obstructions are removed?
River mining differs from the type of remedial dredging that we are doing now. The objective for river mining is to maximize profit, which often means pushing limits. The motivation for dredging is to maximize profits by staying within the limits outlined by the client (i.e., the U.S. Army Corps of Engineers).
The Australian Experience with River Mining
In Australia, the government of New South Whales discussed many of these risks in “The NSW Sand and Gravel Extraction Policy for Non Tidal Rivers.” The executive summary (page 5) describes the situation we face today in the Houston region.
The discussion of risks begins with an admonishment. “Management of sand and gravel extraction must ensure that the activity does not conflict with the aims of other component policies.” For instance, they say that, “Wild and scenic rivers, wetlands and designated recreational areas are all places where sand and gravel extraction would have a highly visible and adverse impact. Extraction should not be considered in such areas.” (Sec. 6.1.1, Page 16.)
To that list, I personally would add, “The source of drinking water for millions of people.” A growing body of evidence collected by the Houston-Galveston Area Council suggests that alarming bacterial growth in the West Fork of the San Jacinto can be linked to excess sedimentation.
The Major Risks of River Mining
Other risks outlined by New South Whales include:
What to Do
The Australian report then goes on to talk about the need for sand and gravel to support road building and economic growth. (Sec. 6.2).
Section 6.3 talks about alternative sources for sand and gravel.
Section 6.4 talks about governmental costs to monitor sand and gravel extraction.
Section 7 talks about guidelines for safe extraction when mining in rivers and how to crack down on illegal activity (something we desperately need to do here as well). Here they talk about the opportunity to involve community members as extra pairs of eyes and the need to enroll major purchases (such as TxDoT) in the enforcement effort.
Section 8 talks about permitting procedures.
Section 9 talks about performance measures and monitor programs. Here they have some novel measures that we could learn from. I especially like Section 9.3, Community Monitoring. Inputs include:
Such an inclusive approach helps guarantee that the needs of various interest groups are balanced.
Australian Conclusions: A Cautionary Tale
Section 10, the Conclusion, says on page 36: “There are many natural causes which may increase the rate of riverbed and bank erosion. However, extraction of large amounts of sand and gravel from within the channels has exacerbated the situation in many rivers. Past experience in some areas of the State has shown that crisis point can be reached. In other areas, increasing conflict with other river uses has made extraction of sand and gravel a less viable option.”
If the State of Texas decides to permit river mining, I sincerely hope we can find a workable balance for the San Jacinto that protects everyone’s interests.
Posted by Bob Rehak on 11/5/2018
433 Days since Hurricane Harvey
Subsidence, Flooding and the Lone Star Ground Water Conservation District Election
Note: If you are from Harris County, you cannot vote in this election, but it still affects you. Please forward this link to friends in Montgomery County. This is an update of a previous post and recommends some candidates at the end.
Next Tuesday, Montgomery County voters will elect board members to the Lone Star Groundwater Conservation District (LSGCD) for the first time ever. Some candidates advocate using more groundwater, a move that could give residents cheaper water in the short run, but which could also cause subsidence and contribute to flooding in the long run. It could even create shortages, raise water costs and limit growth. Here’s how.
How Subsidence Can Increase Flood Risk
When ground subsides, it sinks. In this region, the primary cause is groundwater removal.
“Using surface water instead of groundwater reduces subsidence. Where groundwater use has been reduced, subsidence has generally ceased,” said Michael Turco, General Manager of the Harris-Galveston Subsidence District.
Southern Montgomery County, and northern and northwestern Harris County have some of the highest subsidence rates in the region today.
Yet some Montgomery County voters advocate removing more ground water because, at this moment, it’s cheaper than surface water. They are betting their future and their neighbors’ futures on it.
One part of Baytown, the Brownwood subdivision, is a classic, visually striking, and cautionary example of subsidence. Brownwood subsided so much that it became uninhabitable. Excessive groundwater pumping by industry around Galveston Bay caused the area to sink ten feet.
In 1944, the area that would become Brownwood in Baytown was starting to show signs of development.
By 1978, Brownwood was well developed…and sinking fast. Then, in 1983, a 12-foot storm surge from Alicia destroyed the entire community.
Today, Brownwood floods so much that all homes are gone. Baytown converted what was left into a park.
Coastal vs. Differential Subsidence
Inland areas also face flood threats from subsidence, but not the kind associated with storm surge. In Montgomery County and surrounding areas, the flood threat comes from sinking at different rates in different places.
Example: subsidence around Jersey Village created a “bowl” within the landscape that has been linked to increased flooding there. See the contour map below.
Other examples: The Woodlands and Kingwood sank two feet in the last century. Most of Buffalo Bayou sank eight.
Red contours show subsidence in last century. Blue contours show subsidence in first 16 years of this century. Note how the small red circle near Jersey Village (A) quickly expanded to the large blue circle around it. Also note (B) the widening gap between red and blue at the top of the frame. This shows that areas that depend on groundwater, i.e., Montgomery County, are subsiding faster than those on surface water, i.e., most of Harris County. Source: Harris-Galveston Subsidence District.
Three Ways Unequal Subsidence Increases Flood Risk
Unequal sinking contributes to flooding by changing the slope of rivers and streams.
The “Pump-Now, Let-Somebody-Else-Pay-Later” Mentality
Subsidence happens so slowly that some people claim it’s not a problem – especially those on higher ground. They want to continue pumping water from wells because they perceive it to be cheaper than surface water.
It can be – at least in the short run– until wells run low or dry. Then pumping costs increase – often along with salinity – and the people who depend on the well are out of water and out of luck.
Much of the groundwater in Montgomery County used for human consumption is pumped from the Jasper aquifer which also affects Harris and Galveston Counties. Source Harris-Galveston Subsidence District.
And that high ground they enjoyed? If it subsides faster than surrounding areas, they can alter the slope of rivers and creeks, increasing their own flood risk, like Jersey Village. This is currently happening in southern Montgomery County and northern Harris County.
Depleting at More Than 500X the Recharge Rate
Still, some people say, “I’ll worry about that when it becomes a problem.”
Problem is:
The rate of depletion will exceed the rate of recharge by more than 500X – an environmental catastrophe.
More Expensive in Long Run
Now consider this. Experience and science show that pressure in an aquifer will decrease when pumping exceeds the recharge rate. And as pressure in an aquifer decreases, the cost of bringing water to the surface increases dramatically. Then recovery is no longer economical, i.e., competitive with surface water. It’s like the oil industry. As a rule of thumb, half the oil in reservoirs is left underground. It’s simply too expensive to recover because of low pressure.
For all these reasons, most counties in the region are trying to switch people to surface water. Groundwater withdrawals in Waller, Liberty, Grimes, Walker and San Jacinto Counties have either declined or stayed the same since 2000.
Counties surrounding Montgomery have either decreased groundwater pumping or kept it steady.
Meanwhile, Montgomery County’s groundwater withdrawals have soared. A report by LBG Guyton Associates to the Lone Star Groundwater Conservation District showed that the largest pumping increase since 2000 occurred in Montgomery County.
Montgomery County groundwater pumping virtually tripled in the last three decades.
Montgomery County Growth
The surge in Montgomery County groundwater usage is largely because of growth. On a percentage basis, Montgomery County is growing faster than any county in the region except Fort Bend.
Montgomery County growth trails only Fort Bend.
So Why Worry NOW?
Water resources take so long to develop that they need to be planned 50 years ahead. If Montgomery County hopes to keep growing rapidly, where will water come from to support that growth? Especially if voters undermine financial viability of the half-billion-dollar, surface-water treatment plant – that they just built – by shifting back to groundwater!
The San Jacinto River Authority (SJRA) finished the plant in 2015 to comply with the LSGCD requirement to reduce groundwater use. Many people don’t realize that the SJRA pumps groundwater from 38 wells to supply The Woodlands. The SJRA must comply with LSGCD regulations like everyone else.
To comply, the SJRA and 90 other water utilities who partnered with them, drew up plans for a surface water treatment plant and signed contracts to purchase water from it. The SJRA then borrowed money from the State and built the plant. Inevitably, the cost of water increased to cover construction.
After it was built, several providers changed their minds and began pushing the LSGCD board to produce more groundwater to take costs back down. When the board refused, the breakaway faction succeeded in getting a measure on November’s ballot to elect an LSGCD board more favorable to groundwater pumping.
Since 2001, the LSGCD has had a nine-member board appointed by a combination of local entities. They include Montgomery County, cities, and MUDs. The SJRA even has one seat. The appointees are experts who fully understand the future consequences of subsidence and unlimited groundwater pumping; an elected board may not.
If an elected board ignores the science and allows unlimited groundwater pumping, it would affect the financial projections on which the surface water plant was built.
Betting the Future
If people vote for candidates who advocate using “cheaper” groundwater in the short term, they will also be voting for subsidence and policies that limit long-term growth. Without question, they will be betting their future, their children’s futures and their neighbors’ futures on a rapidly depleting water source.
If that’s the will of the people, so be it. I just hope they don’t set a precedent that residents in neighboring counties follow. If so, we could all be sunk.
Candidates Who Believe in Science-Based, Groundwater Management
Fortunately, there are people running for LSGWCD board positions who believe in science-based, groundwater management. Knowledgeable acquaintances in Montgomery County recommend the following candidates who, they say, have professional experience related to water management and/or water supply, and would work to preserve Montgomery County’s future, reduce subsidence and prevent flooding:
Please spread the word to every voter you know in Montgomery County.
Posted by Bob Rehak, November 3, 2018
431 Days since Hurricane Harvey