Tag Archive for: TDEM

October 2020 Gate Update

On Friday, October 16, 2020, stakeholders in the Lake Houston Spillway Improvement Project met at the dam to review gate alternatives and progress on the project. The main item of interest: a review of options still under consideration to increase the outflow during major storms, such as Harvey.

History of Project

Shortly after Harvey, representatives from the Lake Houston Area identified “increasing outflow” as one of the main strategies to reduce flooding. Harris County Flood Control District even conducted a pilot study. Flood Control included $20 million for the project in the 2018 bond fund (CI-028). With matching funds identified, grants were then written.

FEMA approved the project. And in April of this year, the clock started ticking on the first of two phases.

Phase One Includes…

Phase One includes preliminary engineering and environmental permitting. It should take 18 months and is on schedule at this point. A key deliverable for phase one is verification of the benefit/cost ratio. But, of course, to determine that, you need to know the cost.

Alternatives Still Under Consideration

FEMA allotted 18 months for Phase 1. We’re six months into that. Work to date has focused on determining the optimal alternative. Five remain:

  1. Expanding the existing spillway by adding new tainter gates
  2. Adding a new gated spillway within the east embankment
  3. Creating a new uncontrolled spillway within the east embankment
  4. Building crest gates within the east embankment
  5. Developing crest gates within the existing spillway

Tainter gates lift up from a radial arm. The tainter gates on Lake Conroe have 15X more release capacity than the lift gates on Lake Houston.

Crest gates flop down from a bottom hinge.

Above: the current conditions at the Lake Houston Dam. Looking slightly upstream. East is on the right.

The east embankment is a solid earthen area 2800 feet long east of the spillway and existing gates. Water cannot get over it in a storm. By adding various structures in this area, engineers could widen the current spillway capacity, allowing release of more stormwater.

One main benefit: additional gates would reduce uncertainty associated with pre-releases. Operators could wait longer until they were certain an approaching storm would not veer away at the last minute. That would avoid wasting water.

Reverse angle. Note the difference in height between the east embankment (left) and the spillway (right). Looking downstream toward Galveston Bay.
Looking west toward Beltway 8. This shows the major segments of the dam.

Benefit/Cost Ratio Must Be > 1.0

The lake-level reduction benefits of these gate alternatives during major floods range up to roughly 8x. The costs also vary by roughly 4x. Those are order-of-magnitude, back-of-the-envelope estimates and far from final. Much hard work remains to develop tighter costs and tighter estimates of flood-level reductions. The latter will determine flood-prevention savings in a storm. And the benefits divided by the costs will determine the benefit/cost ratio.

In FEMA’s eyes, the benefit/cost ratio must exceed 1.0 to justify the project. Said another way, it must produce more benefits than it costs.

FEMA allotted 18 months for phase 1. We’re six months into that phase with a year left. Project partners expect results of the alternatives analysis before the end of the year.

Benefit/Cost Calculation

Given the ballpark costs of some of these gate alternatives, we will need very tight estimates of the benefits.

Potential Benefits include:
  • Upstream flood risk reduction
  • Reduced maintenance (debris management) for CWA
  • Improved Water Quality (post storm)
Potential Impacts include:
  • Increased scour and erosion potential to wetlands downstream
  • Increased water surface elevations to structures downstream
Calculating Benefits

Benefit Cost Ratio = (Net Present Value of Benefits)/(Project Costs)

Project Costs = (Capital costs) + (Net Present Value of Operations and Maintenance Costs)

Major Tasks Remaining in Phase 1

Barring surprises, the preliminary engineering report is due in February 2021 and environmental permitting should be complete by the Fall of 2021. Other tasks that must be completed by then include:

  • Hydrologic modeling of flows into and out of Lake Houston using the latest Atlas 14 data
  • Hydraulic modeling of Lake Houston, its Dam, and the San Jacinto River downstream of the dam to Galveston Bay
  • Calibration of models to historic storms
  • Examination of upstream benefits to residents/businesses removed from flood impacts
  • Examination of downstream impacts associated with additional flow release scenarios

It’s important to understand that not everyone who flooded in the Lake Houston Area did so because of the lake level. Some on the periphery of the flood flooded because water backed up in streams leading to the lake. If you got two feet of water in your living room, it doesn’t automatically mean a lake level reduction of two feet would eliminate your flooding by itself.

Congressman Dan Crenshaw (left) reviews the project with team members at the Lake Houston Dam and listens to their needs.

Phase 2 Still Not Certain

Assuming all goes well in the planning, accounting, and conceptual validation, FEMA will make a go/no go decision on construction at the end of next year or the beginning of the following year. Construction should take another 18 months.


Funding for this project comes from FEMA, Texas Division of Emergency Management, City of Houston and Harris County Flood Control. Other stakeholders include the Coastal Water Authority, Harris County, Fort Bend County, Baytown, Deer Park, and other communities adjacent to Lake Houston.

Posted by Bob Rehak on 10/17/2020

1145 Days since Hurricane Harvey and 394 since Imelda

Mouth Bar Dredging: First Pictures of Next Phase

Earlier this month, the State, Harris County and City of Houston announced the next phase of West Fork mouth bar dredging. Late last week, it got underway in earnest.

West Fork mouth bar on Monday 1.20.2020 before mechanical dredging started.

How Mechanical Dredging Works

Rachel Taylor took the ground-level pictures below earlier today from her back yard in Atascocita Point. They show mechanical excavators eating away at the mouth bar and loading the spoils on barges.

Sunday afternoon, 1.26.2020, two mechanical excavators worked the western end of the mouth bar. They loaded the spoils on waiting barges (right). Photo courtesy of Rachel Lavin Taylor.
Service boats then pushed the barges upriver. Photo courtesy of Rachel Lavin Taylor.
Barge loaded with spoils passes the Deerwood Country Club. Photo courtesy of Rachel Lavin Taylor.
Barges then anchor at Berry Madden’s property on the south side of the West Fork opposite River Grove Park. That black object jutting into the photo from the lower left is the skid of the helicopter. Photo taken 1.20.2020.
From there, other trucks move the spoils inland. For orientation, that water tower in the upper left is south of Kings Lake Estates. Photo taken 1.20.2020.

Mechanical dredging is slower and more labor intensive than hydraulic dredging, but can mobilize faster. In hydraulic dredging, dredgers pump the spoils to a placement area via pipelines. That is faster, but has higher overhead. It also creates more noise.

Hydraulic Dredging Options

The hydraulic pipelines can stretch miles. In the case of the first phase of West Fork mouth bar dredging, they stretched 10 miles upstream. It took five booster pumps to get the material all that way to a sand mine on Sorters just south of Kingwood Drive.

Luckily for us, the pipe from the first phase of mouth bar dredging is still at the Army Corps dock opposite Forest Cove.

Pipe from the first phase of mouth bar dredging still sits at the former Army Corps command post and could be rewelded into longer sections if needed.
The Great Lakes Dredge also remains at the dock. Here you see the pieces below and behind the crane.

At some point in this project, dredging may switch from mechanical to hydraulic. The fact that the Great Lakes dredge remained here bodes well. It chewed through 500,000 cubic yards of debris at the West Fork mouth bar in less than three months. Officials expect mechanical dredging of 400,000 cubic yards to take 8 -12 months.

Additional Dredging Targets and Financing

Other targets reportedly include the East Fork Mouth Bar and several mouth bars that have formed at the mouths of ditches or streams leading into the lake.

State Representative Dan Huberty helped bring $30 million to this phase of dredging via an amendment to SB500 in the last legislature. That money will funnel through Harris County via the Texas Water Development Board. The County also included $10 million in the 2018 flood bond. And the City is applying $6 million left over from a FEMA/TDEM grant for debris removal from Harvey.

For more details on this next phase of dredging, see the previous post on this project.

Two Phase Project Outlined In Grant

Harris County’s proposal for the grant from the Texas Water Development Board (TWDB) calls for splitting the project into two phases. 

  • Phase One will focus on the West Fork Mouth Bar using the City’s $6 million and $10 million from the TWDB grant.
  • Phase Two will focus on the East Fork Mouth Bar using the remaining $20 million from the grant.
  • The $10 million from the County flood bond will fund surveys, formulation of specs, bidding, project management and more.

Progress Result of Pulling Together

All this is great news for the Lake Houston Area. The entire community worked since Harvey to make this happen through all levels of government.

As we look at other flooding problems in the area, it’s important not to get discouraged and to remember that we can make progress if we all pull together.

Posted by Bob Rehak on 1/26/2020 with photos from Rachel Lavin Taylor

880 Days since Hurricane Harvey

Clarification and $2.8 Billion Worth of Good News Regarding Senate Bill 500 and Harvey Funding

I previously reported that Senate Bill 500, an omnibus appropriations bill passed unanimously by the House this week, deleted all funding for the Texas Infrastructure Resiliency Fund (TIRF). However, I should also have clarified that it did NOT delete ALL funding related to Harvey and flooding.

The House deleted the portion of funding related to flood-mitigation while it considers House Bill 13 with its own infrastructure fund. The House DID leave IN approximately $2.8 billion for items not related to flood-mitigation infrastructure improvements, but related to Harvey repairs, reimbursement for extraordinary Harvey expenses, flood health care, and more itemized below. Unless noted otherwise, all expenditures are for fiscal year 2019. These Harvey-related appropriations include the following:

TDEM Matching Funds for FEMA

  • $273,000,000 to the Texas Division of Emergency Management (TDEM) for matching funds for projects sponsored by political subdivisions and approved for the Hazard Mitigation Grant program administered by FEMA 
  • $400 million to TDEM for matching funds for projects sponsored by political subdivisions and approved for the Public Assistance grant program administered by FEMA. 

Health & Human Services and Education

  • $110,000,000 to Health and Human Services for children’s Medicaid expenses
  • $271,300,000 to the Texas Education Agency (TEA) for increased student costs, reduction in school district property values and the reduction of the amount owed by school districts to achieve an equalized wealth level due to disaster remediation costs
  • $634,200,000 to the TEA for adjustment of school district property values and reimbursement to school districts for disaster remediation costs
  • $636,000,000 to TEA for the 2020 state fiscal year
  • $20,288,883 to the University of Houston
  • $4,000,000 to the University of Houston Downtown; 
  • $1,703,828 to the University of Houston – Victoria
  • $83,668 to the University of Houston – Clear Lake
  • $13,100,000 to the Lone Star College System
  • $2,458,239.76 to the Texas A&M Forest Service
  • $1,418,585 to Lamar University;
  • $1,312,657 to Lamar Institute of Technology
  • $6,319,458 to Lamar State College – Port Arthur
  • $406,112 to Lamar State College – Orange
  • $10,200,000 to UT Austin for storm damage

Criminal Justice and DPS

  • $38,6000,000 to the Department of Criminal Justice
  • $34,954,409 to Dept. of Public Safety (DPS) for Strategy A.1.1., Organized Crime; 
  • $60,000,000 to DPS for Strategy C.1.1., Traffic Enforcement
  • $2,000,000 to DPS for Strategy G.1.3., Information Technology

General Land Office

  • $696,921 to the General Land Office (GLO). for Strategy A.2.1., Asset Management
  • $20,459,797 to GLO for Strategy B.1.1., Coastal Management
  • $430,000 to GLO for Strategy B.1.2., Coastal Erosion Control Grant
  • $2,047,454 for Strategy B.2.1., Oil Spill Response
  • $4,217,510 to the GLO for full-time equivalent employees contingent on non-renewal of FEMA funding
  • $2,000,000 from the coastal protection account to the GLO for removal of abandoned vessels

Teas Parks & Wildlife and Workforce Commission

  • $17,000,000 to Parks and Wildlife to repair structures and equipment
  • $8,931,385 to Texas Workforce Commission for vocational rehabilitation services expenses

For More Information

Most of these expenditures will come from the Economic Stabilization (Rainy Day) Fund. For those who wish to learn more and review the exact wording of the House Committee Substitute version of SB500:

Here is the House version of CSSB500.

Here is the House Research Organization’s analysis of the bill.

Here is the House Appropriation Committee’s report on the bill.

Posted by Bob Rehak on March 30, 2019

578 Days since Hurricane Harvey

City Analyzing Samples from Mouth Bar In Hopes of Determining Volume Due to Harvey

According to Stephen Costello, Chief Resiliency Officer for The City of Houston, the City contracted with a company called Tetra Tech to take core samples earlier this week from and around the mouth bar on the West Fork of the San Jacinto.

Why Core Samples?

The mouth bar is a giant sand bar at the mouth of the river where it meets the lake. The size of it has concerned residents throughout the Lake Houston Area since Harvey. It has the potential to back water up on both sides of the river and worsen flooding.

Some background. The Army Corps initially excluded the mouth bar from its current dredging program on the west fork. Their reason: a small part of the bar existed before Harvey. FEMA, which is funding the dredging, by law cannot spend money on remediation for things that existed before the disaster in question.

It took months for the City, FEMA and the Army Corps to agree on a way to estimate the volume of sand deposited by Harvey. The answer says Costello: something called the Stockton protocol that he says was developed after Superstorm Sandy at Stockton University in New Jersey.

Analysis Due by End of February

The core samples will be key to estimating pre- and post-Harvey volumes. Costello says engineers will look at density and color of sand grains to help estimate where sediment from one storm stops and another starts.

Costello hopes engineers will complete their analysis by the end of February. In the meantime two other efforts are proceeding simultaneously.

Search for Suitable Disposal Site Continues

The Corps will evaluate one property for suitability as above-ground storage. Separately, others are also out looking at sub-surface storage sites (i.e., old sand pits). Several have been located. The cost and safety of above ground and below ground storage will be weighed against the possibility of hauling material off by truck. Distance between the dredge and disposal sites also affects pumping costs.

All this will take time, especially if a full-blown environmental study is necessary for the above-ground option. Costello says the Corps has told him that could take four months to two years.

Evaluating Plan B

Because of delays, Costello is starting to worry that delays may cost taxpayers the opportunity to save $18 million. That’s the cost to remobilize a second dredging project if the current dredging project cannot be extended.

Accordingly, Costello is pursuing two options. The first involves praying (that’s a joke). The second involves working back through the Texas Division of Emergency Management to get FEMA to declare the mouth bar part of the original emergency mission. The Corps seems to move much faster when orders come from FEMA, several sources tell me. Maybe we should start praying too. (That’s not a joke.)

Money, according to Costello, should not be a problem. FEMA has approved the use of debris cleanup money from Harvey for dredging. He believes enough money remains in that fund to cover the City’s cost share.

Where Current Dredging Project Stands

The Corps estimates that the current dredging project is 45% complete. They hope to complete dredging by the end of April.

City contractors are still removing downed trees from Lake Houston as a result of Hurricane Harvey’s destruction.
The Callan Dredge is currently working the area near Kings Harbor at the West Lake Houston Parkway Bridge.
The immensity of the equipment underscores the need to keep crews working at the end of the current project on the mouth bar. Remobilizing all this equipment could cost $18 million or more if delays create a need to remobilize.

Posted by Bob Rehak on February 7, 2018

527 Days since Hurricane Harvey