McCabe has given ReduceFlooding.com permission to reproduce his letter. See below.
To the SJRA:
Thank you very much for the opportunity to respond to the Sand Trap Study you have formulated. I think your initial work is excellent and commend you on your data gathering. However, there are a few points I would like you to consider before proceeding.
As you know, my group worked very hard with TCEQ to establish Best Management Practices (BMPs) for Sand Miners in the San Jacinto watershed. This Rulemaking was approved in early 2022 and incorporated into 30 TAC Chapter 311, Subchapter J. Also approved was corresponding Regulatory Guidance document RG 555, implementing the BMP Rules.
Key Provision: Undisturbed Buffer Zones
A key provision of the Regulatory Guidance is:
“2.1.1 Vegetative Buffer Zones Vegetative buffer zones are continuous undisturbed or planted vegetated areas that surround a development, or land disturbance activity, or that border an intermittent stream or permanent water body. Buffer zones aid in sediment filtration and removal by slowing surface water flow through these areas. Disperse construction site runoff over the entire buffer zone if possible. A minimum 100-foot buffer zone is required adjacent to perennial streams greater than 20 feet wide, 50 feet for perennial streams less than 20 feet wide, and 35 feet for intermittent streams. Measure buffer zones from the stream bank to the nearest area of disturbance at the site.”
Study Recommendation is “Counterintuitive”
We had fought very hard to establish these buffer zones (at one time we had proposed buffer zones of 1,500 feet). The very essence of this provision was to KEEP the miners out of the San Jacinto riverbed. Now to go back and allow in-stream mining seems counter-intuitive to me.
Legal Complications of Waiving Buffer Zone
Additionally, I am not certain how you would get this buffer zone condition waived. HB 1824 issues a waiver per the Parks and Wildlife Code, Sec. 86.017. However, it does not address TCEQ regulation at 30 TAC Chapter 311(J), which was implemented AFTER HB 1824 was passed. You need to have your staff look at the interaction between the two conflicting provisions.
More Holistic Approach Needed
Before proceeding, I would suggest looking closely at Bob Rehak’s Holistic approach to reducing sedimentation, as outlined in one of his recent articles:
Revegetating riverbanks
Dredging more often where the sand builds up near the mouth of the West Fork
Dredging a channel through the mouth bar area
Reinforcing sand-mine dikes to withstand floods
Leaving more natural green space between mines and the river
Moving sand mine stockpiles out of floodway/floodplain areas
William McCabe, Lake Houston Area Grassroots Flood Prevention Initiative
If you have questions or comments on the SJRA’s Sediment Trap Proposal, please submit them via email to: floodmanagementdivision@sjra.net.
Deadline: No later than April 29, 2022
Posted by Bob Rehak on 4/15/22 based on a letter by Bill McCabe, Chairman of the Lake Houston Area Flood Prevention Initiative
1690 Days since Hurricane Harvey
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The San Jacinto River Authority (SJRA) recently completed a 246-page conceptual design study, in partnership with the Harris County Flood Control District, that explored the feasibility of implementing sediment trapping facilities (“sand traps”). The purpose: to remove sediment from the West or East Fork of the San Jacinto River. The results and findings of this study have been documented in an engineering report entitled “San Jacinto River and Tributaries Sediment Removal and Sand Trap Development.”
Prior to proceeding to preliminary engineering design and any subsequent project phases, SJRA is seeking public input on the proposed project alternatives detailed in the report. The full report, as well as a brief summary document, are located on SJRA’s Flood Management Division website.
Caution: The full study is dated 1/7/22. But the “brief summary” is dated 3/9/22. Make sure you at least read the executive study of the full report as well as the brief summary. There are important differences.
Overview/Purpose
SJRA says the purpose of the sediment trap study was to assess the feasibility of implementing a pilot project to trap and remove sediment from the West OR East Fork of the San Jacinto. The study only assessed locations where one or more Aggregate Production Operations (APOs) could partner with the the SJRA. They restricted the study this way to reduce costs; the SJRA does not have a source of funding to clean out sand traps and would rely on sand miners.
Initial Concerns
The decisions to:
Define the study objective as sediment reduction, not damage reduction and…
Only consider locations near sand mines…
…give me mixed emotions about this project.
Pros
On one hand, I look at this and say, “It’s a pilot project. Try it and see if there’s a benefit.” Sediment IS a problem and they believe they can remove up to 100% of the annual sediment load (from the West Fork).
Cons
On the other hand, the study authors, Freese & Nichols (F&N) claimed (in the San Jacinto River Basin Master Drainage Study) that of all the sediment coming into Lake Houston, two thirds comes from Spring and Cypress Creeks while only 13% comes from the West Fork upstream of US59.
Perhaps that’s because they’re using model inputs from a sediment gage at I-45 located 8.5 miles upstream from most of the large West Fork sand mines (page 34, paragraph 3 of full study).
The “Mouth Bar,” a giant sand bar that blocked the West Fork of the San Jacinto, backing the river up into Kingwood and Humble. Thousands of homes and businesses flooded behind this blockage. The above-water portion has since been removed, but most of the underwater portion remains.
In the entire 246-page F&N study and the three-page summary, the word “damage” occurs only once…in relation to erosion damage, NOT flood damage.
It appears that F&N did not even look at creating sand traps where they were most needed, in the headwaters of Lake Houston, because of cost and logistical considerations. Yet the Army Corps, City of Houston, and State of Texas are spending $200 million to dredge that area. One wonders whether SJRA should have looked harder for partners to clean out the traps.
Finally, if sediment traps only work financially near sand mines, the “solution” will not work on other tributaries that F&N alleges contribute 5X more sediment than the West Fork. They just don’t have the sand mines that the West Fork has.
Nature of Proposed Solution
Five years after Harvey, we have a conceptual design and a recommended location: rock-lined channels cut through one or two point bars at the West Fork Hallett mine.
The shot below shows the same area in real life. To put the magnitude of the proposed solution into perspective, the solution would cover a little more than an acre. But sand mines like Hallett cover 20 square miles on the banks of the West Fork between US59 and I-45.
2021 photo of sand bar outsde Hallett mine that would have a narrow channel cut through it to trap sand.
My Biggest Fears
My biggest fears with the proposed pilot study are that it:
Asks people to chose from a limited menu.
Could divert attention from better solutions that would reduce flood risk faster in the headwaters of Lake Houston.
Might make the public think the problem is solved.
Could open the door to river mining and further destabilize the riverine environment.
Is not a transferrable solution.
For a pilot study, that last point is troubling.
Also, F&N worries that removing too much sediment from the West Fork could create a “hungry-water” effect that increases erosion downstream. But they have no way of directly measuring how much sediment the West Fork transports. Or what percentage they would remove. That’s because they’re relying on a sediment gage upstream from the sand mines. This introduces an element of risk in the pilot study.
Recommendations Should Be Based on a Holistic Examination of Alternatives
Note lack of vegetation on this steep-sided, eroding bank of Hallett mine on West Fork in foreground.
Before moving forward with the pilot study, I suggest a more holistic examination of additional alternatives that might have a greater impact on reducing flood damage, not just sedimentation. Examples include, but are not limited to:
More on the sand trap proposal in coming days. In the meantime, please review the SJRA’s sediment trap proposal and forward your comments to the SJRA. I will also print thoughtful letters, both pro and con, from responsible parties. Send them to: https://reduceflooding.com/contact-us/.
Posted by Bob Rehak on March 27, 2022
1671 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.
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The City did apply for a grant to fund construction of a detention basin on the Perry Homes’ Woodridge Village Property north of Elm Grove Village in Kingwood. It was correctly attributed.
Four Projects Should Have Been Attributed to SJRA
The SJRA submitted four of the five applications that were incorrectly attributed.
San Jacinto River Sand Trap Development
Spring Creek Watershed Flood Control Dams Conceptual Engineering
Upper San Jacinto River Basin Regional Sedimentation Study
Lake Conroe-Lake Houston Joint Reservoir Operations Study
Here’s more information about those four proposals.
The Sand Trap Study currently underway has to do with identifying acceptable locations for the sand traps. Once identified, the new grant would cover the cost of their detailed design. The proposed study would extend work currently underway.
The Spring Creek Watershed Flood Control Dams Conceptual Engineering Grant would cover the cost of partially designing dams. The San Jacinto River Basin Study identified locations for the dams. But it did not look at construction details. The new study would look at things, such as environmental impacts, utility conflicts, height of embankments, size of reservoir, etc. It continues work to date in the Spring Creek Watershed. San Jacinto River Basin Study partners have not yet released the locations.
The Regional Sedimentation study builds on KBR’s work in 2000. KBR studied portions of the watershed that drain into Lake Houston, but not the East Fork, Caney Creek and Peach Creek. The new study has two objectives: understand where sediment is coming from and what can be done to reduce it. For instance, if the sediment is coming from new developments or sand mines, there may be a need to look at regulations that affect those.
The Lake Conroe-Lake Houston Joint Reservoir Operations Study would look at the best ways to operate the two dams under different storm scenarios. It would assume the construction of additional floodgates on Lake Houston. It would also model storms approaching from different directions. The study will answer questions, such as “What would the effect of pre-releasing water into Galveston Bay be on Cities such as Baytown if a hurricane approaches from the south?” The deliverable: an operations plan.
Sedimentation and Its Role in Flooding
Two large sources of sediment: sand mines and new developments. Here the drainage for the Artavia development tries to find a path to the West Fork, through or around two sand mines. One of the mines was cited by the TCEQ for discharging 56-million gallons of sediment-laden wastewater into the West Fork.The City, County, State and Federal Government are still working to remove the West Fork Mouth Bar, 1040 days after Hurricane Harvey. This bar is partially the result of excess sedimentation. During Harvey, this bar formed a partial dam that contributed to the flooding of more than 4000 homes and businesses.
More East Fork Gages in San Jacinto County
In addition, the SJRA has applied for a grant to purchase several more stream gages in San Jacinto County. San Jacinto County lies between Cleveland and Lake Livingston.
San Jacinto County partnered with the SJRA on that grant and would provide ongoing maintenance and operations if the application is successful.
Benefits of Additional Gages
Those additional gages would extend the flood-warning time for people in the East Fork Watershed. Such information is crucial for developing evacuation plans in emergencies.
The gages would also help inform the gate operations at Lake Houston. During Imelda, the East Fork received ten times more rain than the West Fork, but the West Fork has far more gages. That hindered understanding of where the danger was coming from and when it would strike.
As news becomes available about other grant applications in the San Jacinto Watershed, I will post it here.
Posted by Bob Rehak on 7/4/2020
1040 Days after Hurricane Harvey
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The SJRA announced earlier this week that the Harris County Flood Control District will partner with the River Authority on a “sediment trap” pilot study for the East and West Forks of the San Jacinto. The two have hired engineering firm Freese & Nichols to conceptually design the traps and identify the optimal locations for them.
Finding the Right Combination of Factors
Most sediment traps are big holes dug in a river or channel though some are off to the side. As water passes them, velocity decreases. Suspended sediment and sand being pushed along the river bed fall into them.
Source: EPA. The hole reduces water speed which accelerates deposition in a fixed location that’s easy to clean out.
The optimal length, for instance, depends on the speed of floodwaters and the settling rate of sediment particles. The trap needs to be long enough to give suspended sand time to fall out of suspension. Otherwise, sand just passes over the trap and continues downriver.
The hope: that the right type of traps placed in the right locations could help reduce flooding by reducing the amount of sediment migrating downriver and then blocking the mouths of each river branch.
Coming Out of HB1824 and River Basin Study
House Bill 1824, passed just last year, helps make sediment traps financially feasible. It allows the partners to remove material from the San Jacinto River and its tributaries to restore, maintain, or expand storm flow capacity without the need for state permitting or a royalty payment to the state.
The scope of work outlined for Freese & Nichols includes, but is not limited to:
Reviewing and comparing: current and historical LiDAR surveys and aerial photos to gauge sediment erosion, deposition and location
Evaluating digital elevation maps to identify constrictions
Identifying the ten areas with the largest volumes of sediment deposition, including the two largest at a sand mine.
Reviewing FEMA floodplain, National Wetland Inventory, Texas Historical Commission and Texas Parks and Wildlife information for any problems related to each potential site.
Core sampling of sand bars to determine silt content
Ranking preliminary locations using the following: sediment deposition volume, potential sediment storage volume, proximity to existing roads, proximity to existing APO facilities.
Selecting the four locations with the highest potential based on drainage area, sediment load, geology, road access, etc.
Narrowing that to three locations in conjunction with SJRA and HCFCD
Developing sediment trap conceptual solutions specific to each of the final three selected sites
Estimating rate of sediment accumulation and clean-out intervals
Estimating reduction of sediment accumulation due to trapping
Submitting a final report.
The project does NOT extend into Lake Houston. Freese & Nichols will examine both the East and West Forks plus three miles upstream from the East and West Forks along certain tributaries. Tributaries would include, for instance, Lake Creek and Caney Creek. The idea is to intercept sediment before it can make its way into the lake.
Project Timing
The project timetable indicates completion in early fall of 2020, about the same time as the entire San Jacinto River Basin Study. Thus, any recommendations coming out of this project would not be constructed for this hurricane season. SJRA currently hopes to have the trap(s) installed by the end of 2022.
Pros and Cons of Sediment Traps
Proponents say sediment traps can reduce expensive dredging, restore fish habitat, reduce flood risk and more. However…
The scientific literature on sediment traps reveals mixed reviews. Many efforts fail, primarily because of lack of maintenance budgets and regular clean-outs. The SJRA and HCFCD plan to address that issue upfront by involving the sand mining industry. Notice that of the four location-ranking criteria bolded above, three favor proximity to sand mines:
Sand mines have pits to store sediment.
They have roads that lead to the river that can carry heavy equipment.
Mines have cleaning, sorting and transportation facilities onsite to reduce transportation costs, and thus make material more attractive for resale.
Compensation for Sand Miners
A compensation agreement for sand miners who remove sediment from traps has not yet been worked out. However, Matt Barrett, SJRA’s project engineer, says, “The intended benefit to the APOs of participating in the public-private partnership would be that they could utilize or sell the material they remove from the trap(s). ”
River mining is outlawed in Europe, many other first-world nations, and even in some third world countries.
It tends to alter the gradient of rivers; cause upstream and downstream erosion; destroy private property along river banks; and undermine infrastructure such as bridges and pipelines.
Thus, the sediment traps raise a question of potential liability. If a pipeline or bridge is undermined or if property is eroded by the traps, who is responsible?
“Stability of the river is key to the long term safety and well-being of our community. We know that our public agencies have an important task. Before spending additional taxpayer dollars, don’t we want to make sure that projects won’t make problems worse AND won’t raise taxpayer costs?” said Jill Boullion, Executive Director of the Bayou Land Conservancy.
SJRA Response to Concerns
The SJRA has consistently denied that it would permit wholesale river mining. Most recently, Matt Barrett, the River Authority’s engineer for the sediment trap project said, “SJRA has no intention of engaging in or facilitating river mining in the San Jacinto River or any of its tributaries. The legislative language in HB1824 allows for the removal of material for the purpose of restoring, maintaining, or expanding the capacity to convey storm flows. Any projects undertaken by SJRA to remove or facilitate the removal of material from the San Jacinto River or its tributaries would be for this purpose.”
“River mining is not part of what we are doing. Only sediment in the trap will be removed,” he said.
Barrett is aware of potential hazards. “SJRA and its consultant are aware of the potential negative impacts that can be caused by trapping and removing sediment from a river or stream – changing the sediment balance – and prior to constructing any sediment trap or implementing removal of any material will perform analysis to ensure that any potential negative effects do not offset the positive.”
He sees the current design project as part of a pilot study that can scale up later. “One of the goals of this relatively small scale project is to serve as a “pilot” that gives us data on the real-world effectiveness of sand traps. If data indicates this is a viable flood risk mitigation solution, then additional funding and partnerships could be sought to expand the concept. We are excited to start this project and seek solutions to reduce flood risk.
For More Information
For more on how on sediment traps work, see this presentation found on the EPA site about a project in Michigan. It’s not directly analogous to south Texas because rainfall rates, soil types and gradients differ. But helps explain the theory of traps.
948 Days after Hurricane Harvey and 197 since Imelda
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