Here’s an update to last week’s watchlist. It includes seven Lake Houston Area developments – four from last week and three new.
Perry Homes’ Woodridge Village
On April 28, 2020, Harris County Commissioners approved the purchase of Woodridge Village from Perry Homes with two conditions: 1) that the City of Houston would defray half the cost by contributing $7mm worth of land that HCFCD needed for other flood control costs, 2) that the City would adopt new Atlas-14 rainfall statistics.
The next day, Houston Mayor Pro Tem Dave Martin discussed the deal on a Facebook live “virtual lunch” with the Lake Houston Area Chamber. At about 26:20 into the video, he said that the stipulations had already been agreed to. He said the City had already identified 11 pieces of property, 6 of which were presented to the County during its consideration of the deal in executive session the previous night. He also said the City would divert water from Taylor Gully to the Kingwood Diversion Ditch and build a barrier between Elm Grove and Woodridge, while the county built a regional detention facility.
Perry contractors went back to work the next day before Martin spoke. They continued working all week. They worked near Mace in Porter, on N2 (the large detention pond in the middle of the western border), and N3 (another detention pond on the eastern border).
A reliable source who needs to remain anonymous told me that the work was at the request of Perry’s lawyers. The source said that Perry and its contractors were simply complying with their contract.
This week marks the anniversary of the first storm (May 7th) that landed Perry in hot water. And forecasters predict an above-average hurricane season, which starts in four weeks. The lawyers may have had that on their minds, too. As they say in legal circles, “The third time is the pen.” Woodridge contributed to flooding Elm Grove twice last year, in May and September.
Excavator working near Mace in Porter on April 29, 2020.
Romerica’s “Orchard Seeded Ranches”
This is the 331-acre project formerly known as the Heron’s Kingwood. It wound around the Barrington and River Grove Park. Romerica is now trying to develop the same land under a different name, “Orchard Seeded Ranches.”
However, on Thursday, 4/30/2020, the Houston Planning Commission deferred approval of the developer’s General Plan.
General Plan of Orchard Seeded Ranches in Kingwood Texas
The Commission then asked the developer to consult with the City Engineer; the Planning and Development Department; and Harris County Flood Control before bringing further requests back to the Commission.
That should send a strong signal to the developer that rough waters lie ahead. Any proposal will likely be debated publicly when/if the developer returns.
The development is still listed in CoH’s PlatTracker. So we will continue to watch this one.
Holley’s Kingwood Cove Golf Course Redevelopment
A review of the City of Houston’s PlatTracker Plus Map indicates that Holley has not yet applied for any permits on the golf course in Forest Cove. City of Houston confirmed that via a FOIA request (Freedom of Information Act).
Note how golf course on left is unshaded. That indicates no activity with the Planning Commission. Compare that to the purple area on the right for Romerica’s property. That indicates approval of a General Plan is still pending.
A review of the Harris County Appraisal District website indicates a limited liability company in Pittsburgh, PA, actually owns the golf course.
Harris County Appraisal District info for property at 805 Hamblen, aka Kingwood Cove Golf Course.
It’s not unusual for developers to use other people’s money. I shall continue to watch this. Holley says his engineer is reworking plans based on input from people surrounding the course.
Ryko Property Near Confluence of Spring Creek and West Fork
This property is in Montgomery County and the City of Houston’s Extra Territorial Jurisdiction. The Montgomery County Engineers office says the company has not yet filed any plans that have been approved. The City of Houston PlatTracker Plus Map also shows the owner has not yet filed any applications.
US FWS Wetlands Map shows wetlands throughout the Ryko property between Spring Creek and the West Fork.
New Caney ISD High School #3
Dark green area in center between Sorters Rd. and 59 is future home of New Caney ISD High School #3.
The New Caney Independed School District plans to build a third high school south of the HCA Kingwood Medical Center and behind the car dealerships that front US59. I don’t know much more about this except that they plan to extend roads into the area that is now forest. High schools usually have large parking lots. And that means rapid drainage. It is unclear at this time whether MoCo will require detention ponds.
Northpark Woods
Looking northwest at Northpark Woods from over Sorters/McClellan Road. The drainage ditch on the left parallels Northpark Drive. Sand mines and the West Fork are in the background.Photo 4/21/2020.
This high-density development along the West Fork San Jacinto River in Montgomery County is now about one-third to one-half built. Construction continues.
The Colonies in Plum Grove
North of SH99 in Plum Grove and east of the East Fork in Liberty County, lies one of the largest developments in the Houston region without detention ponds.
Formally known as Colony Ridge, some locals call it “The Colonies.” Colony Ridge bills itself as a “master-planned” community with six major subdivisions: Sante Fe, Camino Real, Grand San Jacinto, Rancho San Vincente, Montebello, and Bella Vista. Together they comprise 30,478 lots on approximately 10,000 acres at present. And they’re still growing!
The Colonies currently cover an area almost as large as Kingwood. Photo 4/21/2020.Drainage empties into the East Fork San Jacinto. While flying over the area, I did not see one detention pond. Mobil homes make up most of the housing stock.Note open-ditch drainage.
Colony Ridge advertises itself as “an escape from the city, land on which to grow and build a home, no restrictions and easy credit.” Aerial photos reveal people scratching out hardscrabble lives on barren lots.
This is a blue collar neighborhood. The developer says his target market is poor Latino laborers. They see this as a step up from apartment living and a chance to own a part of the American dream.
But while flying over it, I did not see one detention pond.
As SH99, the Grand Parkway, pushes east from 59, this area will boom. Without better drainage regulations, Liberty County and Plum Grove will heap their drainage problems on those downstream.
FEMA’s National Flood Hazard Layer Viewer shows East Fork Flood Plains relative to Colony Ridge (right).
The good news is that Liberty County has joined with seven other counties to form a Southeast Texas Drainage District. The bad news is that Harris County is not one of the seven.
Posted by Bob Rehak on 5/3/2020
978 Days after Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/05/20200421-RJR_1204.jpg?fit=1200%2C800&ssl=18001200adminadmin2020-05-03 10:41:082020-05-03 11:00:12Development Watchlist: Perry, Romerica, Colony Ridge and More
Since the National Flood Insurance Plan’s (NFIP) inception in 1968, additional legislation has been enacted to strengthen the program, ensure its fiscal soundness, create better maps, and tie rates closer to risk. Next year, FEMA will transform the NFIP with something called Risk Rating 2.0, a major change.
FEMA says that with Risk Rating 2.0, NFIP is leveraging industry best practices and current technology to deliver rates that are fairer, easier to understand, and better reflect a property’s unique flood risk.
That last part is code for “we lost a lot of money.”
Unsustainable NFIP Losses
NFIP continues to pay claims in excess of revenues, and borrows increasingly from the U.S. Treasury.
Last October, Michael D. Berman wrote an article titled “Flood Risk and Structural Adaptation of markets: An Outline for Action” in the Federal Reserve Board’s Community Development Innovation Review. In it, he says, “On September 22, 2017, after borrowing $5.825 billion to fund claims from Hurricanes Harvey, Irma and Maria, the NFIP had reached its maximum U.S. Treasury borrowing authority of $30.425 billion in program debt. On October 26, 2017, Congress cancelled $16 billion of NFIP debt—the first time in the history of the NFIP that has occurred. Then on November 9, 2017, the NFIP borrowed another $6.1 billion to fund additional 2017 losses, including additional losses from Hurricanes Harvey, Irma and Maria.”
Rating Flood Risk at Property Level
Berman claims, “The NFIP is clearly not properly pricing flood risk, nor is it adequately influencing prudent behavior by property owners and municipalities to sufficiently reduce or otherwise mitigate this risk…This new rating system, known as Risk Rating 2.0, is expected to include repricing of premiums based on flood risk at the property level.”
What Risk Rating 2.0 Involves
FEMA says its current risk-rating methodology has not fundamentally changed since the 1970s. It is now heavily dependent on the 1-percent-annual-chance-event (100-year floodplain).
Risk Rating 2.0 will incorporate a broader range of flood frequencies, new mapping data, and new technologies, more individual rating characteristics, such as:
• Distance to the coast or another flooding source; • Different types of flood risk; and • The cost to rebuild a home.
By reflecting the cost to rebuild, the new rating plan will also aim to deliver fairer rates for owners of lower-value homes.
Rates that Promote Mitigation Efforts
FEMA also plans to offer mitigation credits to help incentivize risk-reduction efforts and reduce the cost of future flood events. Risk Rating 2.0 will initially provide credits for three mitigation actions:
Installing flood openings;
Elevating onto posts, piles, and piers; and
Elevating machinery and equipment above the lowest floor.
FEMA is not yet saying how many premiums will increase or decrease, or by how much. Two things ARE clear though.
6:1 Payback on Flood Mitigation Investments
First, the old system is broken and unsustainable. Flood maps were outdated and based on data decades old in many cases. They contained many unmapped areas and the mapped areas were strongly influenced by local politicians and developers. Maps also did not reflect the effects of upstream development or more intense, frequent storms.
Second, the new system has a chance to incentivize risk-reduction. The old system encouraged people and communities to rebuild things the way they were after a disaster. We need a new system that encourages more prudent behavior.
FEMA cites a recent study by the National Institute of Building Sciences. Looking back over 23 years of data, the study found that for every dollar that the federal government invests in flood hazard mitigation, taxpayers save an average of six dollars of future disaster recovery spending.
Rebuild to Fail or Rebuild to Adapt?
The current federal flood insurance program promotes rebuilding in flood prone areas. Hopefully, the new system will promote adaptation to help mitigate increased risk.
Flood insurance rates that better reflect risk may promote more prudent behavior by developers, lending institutions, property owners, buyers, and real estate agents who will all “follow the money.”
In early April, the Coastal Water Authority (CWA) quietly finalized the scope of work for engineers working on adding more gates to the Lake Houston Dam. Engineering firm Black & Veatch’s contract was approved. And their work has now begun. Here’s what it involves.
Looking upstream at the Lake Houston Dam. Photo taken 11/4/2019.
The current gates on Lake Houston’s dam have one fifteenth the discharge capacity of Lake Conroe’s – 10,000 cfs vs. 150,000 cfs.
Additional gates could help synchronize the release rates of the two dams and thus reduce flood risk. More/bigger gates could lower the Lake Houston faster in advance of a storm and add width to the spillway during a storm. Both help reduce flooding.
Avoiding Unnecessary Releases
Currently, it takes several days to lower Lake Houston enough to significantly reduce flood risk. During that time, approaching storms can veer away or dissipate. So a conservation angle exists here, too. More gates release water faster. That lets CWA wait until weather-forecast certainty is higher before lowering the lake. And that, in turn, helps avoid unnecessary discharges and conserve water.
18-Month Project Starting from April 8th
The addition of gates is a three-year project broken into two 18-month phases.
Phase 1 involves preliminary design of conceptual alternatives, selecting the “best” based on criteria described below, and permitting.
The clock for Phase 1 started ticking on April 8, 2020, the day Black and Veatch’s contract was approved. Phase 1 should conclude in September 2021.
Phase 2 involves final design and construction. Assuming all goes well, we could have more discharge capacity at the Lake Houston dam by March 2023 at the earliest. However, there will be an evaluation period between the two phases that could push the completion date out further. Also…
Phase 2 Depends on Outcome of Phase 1
One objective of Phase 1 is to prove up the concept, the budget, and the benefit/cost ratio.
Proceeding to construction in Phase 2 will depend on the outcome of Phase 1. In Phase 1, engineers will examine several possible designs to determine the most effective alternative. They will consider flood reduction benefits, downstream impacts, cost, environmental impact, constructibility and more.
Then FEMA will evaluate the benefit/cost ratio of the winning design to ensure it meets or beats initial projections in the grant request.
If it does, FEMA will release money for Phase 2, the final design and construction.
If it doesn’t, the whole project could die.
FEMA does not guarantee Phase 2 funding at this time.
What Happens Now?
The scope of work document reveals who will do what in the next 18 months on the Lake Houston Spillway Improvement Project (LHSIP).
Objective: To relieve upstream flooding by increased discharge capacity that supports pre-releases.
Modifications could include (but are not limited to):
Additional crest gates on or adjacent to the existing dam or…
New, as-yet-unspecified hydraulic structures that provide for releases elsewhere on the embankment
The project will consider both upstream benefits and downstream impacts.
Looking downstream over the Lake Houston Dam in foreground gives you some idea of the courage that it requires to live or work below a dam.
After defining alternatives and constraints, the contractor, Black & Veatch, will analyze the alternatives to quantify and compare costs and benefits of each configuration.
Five Major Tasks in Phase 1
Preliminary engineering involves five major tasks:
Management plans
Hydrology and Hydraulic Modelling
Permitting
Field Investigation
Development of alternative concepts
Let’s look at each.
Management Plans
Black & Veatch will begin Phase 1 by developing project-, quality-, and risk-management plans.
H&H Studies
Hydrology and hydraulics (H&H) studies will evaluate the ability of the various concepts to reduce upstream flooding and downstream impacts. Black & Veatch will develop H&H models that combine both the San Jacinto River and Buffalo Bayou basins to evaluate downstream impacts of any dam.
The combined model will extend all the way to Galveston Bay and evaluate design alternatives for up to nine events:
2-, 10-, 50-, 100-, and 500-year storms
Extreme historic events (e.g. Harvey, Ike or Memorial Day), including at least one with storm-surge effects
A hypothetical Probable Maximum Precipitation event.
The process includes collecting, reviewing, adjusting and validating existing models before performing simulations.
Permitting Gauntlet
To save time, permitting will begin concurrently with design. The permitting schedule is aggressive and may spill over into Phase 2 as details are refined. Permitting includes (but is not limited to) coordination with federal, state and local agencies for:
Environmental Assessment
Environmental Impact Statement
Wetland delineations
Threatened and endangered (T&E) habitat assessment
T&E species-specific surveys
Migratory Bird Treaty Act (MBTA) surveys
Freshwater Mussel survey
Stormwater pollution prevention
Clean Water Act
Flood Plain Construction
The environmental team will also consider:
Topography and Soils Construction Impacts
Land Use
Indirect and Cumulative Impacts
Geology, Hydrology and Drainage
Sediment Quality
Vegetation
Air Quality
Invasive Species
Coastal Zone Management Wildlife and Endangered Species
Essential Fish Habitat
Existing Facilities and Utilities
Noise Quality
Socioeconomics
Traffic and Circulation
Waters of the U.S., including Wetlands
Environmental Justice
Cultural Resources (historical and archaeological)
Recreation
Floodplains
Visual/ Aesthetic Appeal
Water Quality
Hazardous Materials
Field Investigations
Black & Veatch will also conduct site surveys and a geotechnical investigation, complete with borings, to evaluate soil conditions, depth-to-water, permeability, and seepage control.
A bathymetry team will measure water depth and develop contour maps for an area that extends 500 feet upstream from the dam.
Preliminary Engineering/Conceptual Design
Finally, preliminary engineering will develop conceptual layouts and site plans for several alternatives.
This exercise will also evaluate areas of impact, site access and utilities, staging and borrow areas, dewatering extents, existing structure tie-in, general facilities layout, and downstream channel alignment.
These site plans will be used for costing and evaluating the feasibility for each alternative.
Criteria for Choosing Best Alternatives
The engineers will also develop an evaluation matrix that includes, but is not limited to:
Ability to meet project goals
Environmental clearance
Construction costs, including any environmental mitigation
Long-term operation and maintenance costs
Benefit/cost analysis
Risks in design, construction, and operation.
From all the feasible options, engineers will then chose the three best based on:
Cost
Upstream impact
Downstream impact
Environmental impact
Permitting requirements
Constructibility
Timing on Phase 2
Assuming we get to Phase 2, the second 18 months may not start immediately. FEMA will need time to evaluate Phase 1 results. And the CWA will need to develop bid specs, bid the job, select a winner, and develop a contract with a scope of work, just as they did for Phase 1. That could talk several months and push completion well into 2023.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/05/20191104-RJR_4790.jpg?fit=1200%2C800&ssl=18001200adminadmin2020-05-01 12:22:242020-05-01 15:57:06Preliminary Engineering Starts for Adding More Gates to Lake Houston Dam
Development Watchlist: Perry, Romerica, Colony Ridge and More
Here’s an update to last week’s watchlist. It includes seven Lake Houston Area developments – four from last week and three new.
Perry Homes’ Woodridge Village
On April 28, 2020, Harris County Commissioners approved the purchase of Woodridge Village from Perry Homes with two conditions: 1) that the City of Houston would defray half the cost by contributing $7mm worth of land that HCFCD needed for other flood control costs, 2) that the City would adopt new Atlas-14 rainfall statistics.
The next day, Houston Mayor Pro Tem Dave Martin discussed the deal on a Facebook live “virtual lunch” with the Lake Houston Area Chamber. At about 26:20 into the video, he said that the stipulations had already been agreed to. He said the City had already identified 11 pieces of property, 6 of which were presented to the County during its consideration of the deal in executive session the previous night. He also said the City would divert water from Taylor Gully to the Kingwood Diversion Ditch and build a barrier between Elm Grove and Woodridge, while the county built a regional detention facility.
Perry contractors went back to work the next day before Martin spoke. They continued working all week. They worked near Mace in Porter, on N2 (the large detention pond in the middle of the western border), and N3 (another detention pond on the eastern border).
A reliable source who needs to remain anonymous told me that the work was at the request of Perry’s lawyers. The source said that Perry and its contractors were simply complying with their contract.
This week marks the anniversary of the first storm (May 7th) that landed Perry in hot water. And forecasters predict an above-average hurricane season, which starts in four weeks. The lawyers may have had that on their minds, too. As they say in legal circles, “The third time is the pen.” Woodridge contributed to flooding Elm Grove twice last year, in May and September.
Romerica’s “Orchard Seeded Ranches”
This is the 331-acre project formerly known as the Heron’s Kingwood. It wound around the Barrington and River Grove Park. Romerica is now trying to develop the same land under a different name, “Orchard Seeded Ranches.”
However, on Thursday, 4/30/2020, the Houston Planning Commission deferred approval of the developer’s General Plan.
The Commission then asked the developer to consult with the City Engineer; the Planning and Development Department; and Harris County Flood Control before bringing further requests back to the Commission.
That should send a strong signal to the developer that rough waters lie ahead. Any proposal will likely be debated publicly when/if the developer returns.
The development is still listed in CoH’s PlatTracker. So we will continue to watch this one.
Holley’s Kingwood Cove Golf Course Redevelopment
A review of the City of Houston’s PlatTracker Plus Map indicates that Holley has not yet applied for any permits on the golf course in Forest Cove. City of Houston confirmed that via a FOIA request (Freedom of Information Act).
A review of the Harris County Appraisal District website indicates a limited liability company in Pittsburgh, PA, actually owns the golf course.
It’s not unusual for developers to use other people’s money. I shall continue to watch this. Holley says his engineer is reworking plans based on input from people surrounding the course.
Ryko Property Near Confluence of Spring Creek and West Fork
This property is in Montgomery County and the City of Houston’s Extra Territorial Jurisdiction. The Montgomery County Engineers office says the company has not yet filed any plans that have been approved. The City of Houston PlatTracker Plus Map also shows the owner has not yet filed any applications.
New Caney ISD High School #3
The New Caney Independed School District plans to build a third high school south of the HCA Kingwood Medical Center and behind the car dealerships that front US59. I don’t know much more about this except that they plan to extend roads into the area that is now forest. High schools usually have large parking lots. And that means rapid drainage. It is unclear at this time whether MoCo will require detention ponds.
Northpark Woods
This high-density development along the West Fork San Jacinto River in Montgomery County is now about one-third to one-half built. Construction continues.
The Colonies in Plum Grove
North of SH99 in Plum Grove and east of the East Fork in Liberty County, lies one of the largest developments in the Houston region without detention ponds.
In January of 2017, the Houston Chronicle wrote about how La Colonia was transforming Plum Grove. They interviewed local residents who lamented the loss of forests. ABC13 ran a story about the squalid living conditions. Yet the area continues to expand.
Formally known as Colony Ridge, some locals call it “The Colonies.” Colony Ridge bills itself as a “master-planned” community with six major subdivisions: Sante Fe, Camino Real, Grand San Jacinto, Rancho San Vincente, Montebello, and Bella Vista. Together they comprise 30,478 lots on approximately 10,000 acres at present. And they’re still growing!
Colony Ridge advertises itself as “an escape from the city, land on which to grow and build a home, no restrictions and easy credit.” Aerial photos reveal people scratching out hardscrabble lives on barren lots.
This is a blue collar neighborhood. The developer says his target market is poor Latino laborers. They see this as a step up from apartment living and a chance to own a part of the American dream.
As SH99, the Grand Parkway, pushes east from 59, this area will boom. Without better drainage regulations, Liberty County and Plum Grove will heap their drainage problems on those downstream.
The good news is that Liberty County has joined with seven other counties to form a Southeast Texas Drainage District. The bad news is that Harris County is not one of the seven.
Posted by Bob Rehak on 5/3/2020
978 Days after Hurricane Harvey
FEMA Reforming Flood Insurance Risk, Rate Structure
Since the National Flood Insurance Plan’s (NFIP) inception in 1968, additional legislation has been enacted to strengthen the program, ensure its fiscal soundness, create better maps, and tie rates closer to risk. Next year, FEMA will transform the NFIP with something called Risk Rating 2.0, a major change.
FEMA says that with Risk Rating 2.0, NFIP is leveraging industry best practices and current technology to deliver rates that are fairer, easier to understand, and better reflect a property’s unique flood risk.
Unsustainable NFIP Losses
NFIP continues to pay claims in excess of revenues, and borrows increasingly from the U.S. Treasury.
Last October, Michael D. Berman wrote an article titled “Flood Risk and Structural Adaptation of markets: An Outline for Action” in the Federal Reserve Board’s Community Development Innovation Review. In it, he says, “On September 22, 2017, after borrowing $5.825 billion to fund claims from Hurricanes Harvey, Irma and Maria, the NFIP had reached its maximum U.S. Treasury borrowing authority of $30.425 billion in program debt. On October 26, 2017, Congress cancelled $16 billion of NFIP debt—the first time in the history of the NFIP that has occurred. Then on November 9, 2017, the NFIP borrowed another $6.1 billion to fund additional 2017 losses, including additional losses from Hurricanes Harvey, Irma and Maria.”
Rating Flood Risk at Property Level
Berman claims, “The NFIP is clearly not properly pricing flood risk, nor is it adequately influencing prudent behavior by property owners and municipalities to sufficiently reduce or otherwise mitigate this risk…This new rating system, known as Risk Rating 2.0, is expected to include repricing of premiums based on flood risk at the property level.”
What Risk Rating 2.0 Involves
FEMA says its current risk-rating methodology has not fundamentally changed since the 1970s. It is now heavily dependent on the 1-percent-annual-chance-event (100-year floodplain).
Risk Rating 2.0 will incorporate a broader range of flood frequencies, new mapping data, and new technologies, more individual rating characteristics, such as:
• Distance to the coast or another flooding source;
• Different types of flood risk; and
• The cost to rebuild a home.
Rates that Promote Mitigation Efforts
FEMA also plans to offer mitigation credits to help incentivize risk-reduction efforts and reduce the cost of future flood events. Risk Rating 2.0 will initially provide credits for three mitigation actions:
FEMA is not yet saying how many premiums will increase or decrease, or by how much. Two things ARE clear though.
6:1 Payback on Flood Mitigation Investments
First, the old system is broken and unsustainable. Flood maps were outdated and based on data decades old in many cases. They contained many unmapped areas and the mapped areas were strongly influenced by local politicians and developers. Maps also did not reflect the effects of upstream development or more intense, frequent storms.
Second, the new system has a chance to incentivize risk-reduction. The old system encouraged people and communities to rebuild things the way they were after a disaster. We need a new system that encourages more prudent behavior.
Rebuild to Fail or Rebuild to Adapt?
The current federal flood insurance program promotes rebuilding in flood prone areas. Hopefully, the new system will promote adaptation to help mitigate increased risk.
Flood insurance rates that better reflect risk may promote more prudent behavior by developers, lending institutions, property owners, buyers, and real estate agents who will all “follow the money.”
For More Information
For more information, see:
Risk Rating 2.0 FAQs
Federal Reserve Board Community Development Innovation Review
Cheaper Flood Insurance: Five Ways to Lower the Cost of Your Flood Insurance Premium
NFIP Community Rating System: A Local Official’s Guide to Saving Lives, Preventing Property Damage, and Reducing the Cost of Flood Insurance
FEMA Discussion of Property Insurance Reform
FEMA Discussion about Reducing Risks and Rates
National Institute of Building Sciences 2019 Report on Mitigation
Posted by Bob Rehak on 4/2/2020
977 Days since Hurricane Harvey
Preliminary Engineering Starts for Adding More Gates to Lake Houston Dam
In early April, the Coastal Water Authority (CWA) quietly finalized the scope of work for engineers working on adding more gates to the Lake Houston Dam. Engineering firm Black & Veatch’s contract was approved. And their work has now begun. Here’s what it involves.
Background: Why More Gates?
After Hurricane Harvey, a pilot study by HCFCD and Freese & Nichols showed additional gates could have helped lower floodwaters.
The current gates on Lake Houston’s dam have one fifteenth the discharge capacity of Lake Conroe’s – 10,000 cfs vs. 150,000 cfs.
Additional gates could help synchronize the release rates of the two dams and thus reduce flood risk. More/bigger gates could lower the Lake Houston faster in advance of a storm and add width to the spillway during a storm. Both help reduce flooding.
Avoiding Unnecessary Releases
Currently, it takes several days to lower Lake Houston enough to significantly reduce flood risk. During that time, approaching storms can veer away or dissipate. So a conservation angle exists here, too. More gates release water faster. That lets CWA wait until weather-forecast certainty is higher before lowering the lake. And that, in turn, helps avoid unnecessary discharges and conserve water.
18-Month Project Starting from April 8th
The addition of gates is a three-year project broken into two 18-month phases.
Phase 1 involves preliminary design of conceptual alternatives, selecting the “best” based on criteria described below, and permitting.
Phase 2 involves final design and construction. Assuming all goes well, we could have more discharge capacity at the Lake Houston dam by March 2023 at the earliest. However, there will be an evaluation period between the two phases that could push the completion date out further. Also…
Phase 2 Depends on Outcome of Phase 1
One objective of Phase 1 is to prove up the concept, the budget, and the benefit/cost ratio.
Proceeding to construction in Phase 2 will depend on the outcome of Phase 1. In Phase 1, engineers will examine several possible designs to determine the most effective alternative. They will consider flood reduction benefits, downstream impacts, cost, environmental impact, constructibility and more.
Then FEMA will evaluate the benefit/cost ratio of the winning design to ensure it meets or beats initial projections in the grant request.
FEMA does not guarantee Phase 2 funding at this time.
What Happens Now?
The scope of work document reveals who will do what in the next 18 months on the Lake Houston Spillway Improvement Project (LHSIP).
Modifications could include (but are not limited to):
Unlike tainter gates which swing up from a radial arm, crest gates swing down from a bottom hinge.
After defining alternatives and constraints, the contractor, Black & Veatch, will analyze the alternatives to quantify and compare costs and benefits of each configuration.
Five Major Tasks in Phase 1
Preliminary engineering involves five major tasks:
Let’s look at each.
Management Plans
Black & Veatch will begin Phase 1 by developing project-, quality-, and risk-management plans.
H&H Studies
Hydrology and hydraulics (H&H) studies will evaluate the ability of the various concepts to reduce upstream flooding and downstream impacts. Black & Veatch will develop H&H models that combine both the San Jacinto River and Buffalo Bayou basins to evaluate downstream impacts of any dam.
The combined model will extend all the way to Galveston Bay and evaluate design alternatives for up to nine events:
The process includes collecting, reviewing, adjusting and validating existing models before performing simulations.
Permitting Gauntlet
To save time, permitting will begin concurrently with design. The permitting schedule is aggressive and may spill over into Phase 2 as details are refined. Permitting includes (but is not limited to) coordination with federal, state and local agencies for:
The environmental team will also consider:
Field Investigations
Black & Veatch will also conduct site surveys and a geotechnical investigation, complete with borings, to evaluate soil conditions, depth-to-water, permeability, and seepage control.
A bathymetry team will measure water depth and develop contour maps for an area that extends 500 feet upstream from the dam.
Preliminary Engineering/Conceptual Design
Finally, preliminary engineering will develop conceptual layouts and site plans for several alternatives.
This exercise will also evaluate areas of impact, site access and utilities, staging and borrow areas, dewatering extents, existing structure tie-in, general facilities layout, and downstream channel alignment.
These site plans will be used for costing and evaluating the feasibility for each alternative.
Criteria for Choosing Best Alternatives
The engineers will also develop an evaluation matrix that includes, but is not limited to:
From all the feasible options, engineers will then chose the three best based on:
Timing on Phase 2
Assuming we get to Phase 2, the second 18 months may not start immediately. FEMA will need time to evaluate Phase 1 results. And the CWA will need to develop bid specs, bid the job, select a winner, and develop a contract with a scope of work, just as they did for Phase 1. That could talk several months and push completion well into 2023.
For More Information
All that, just to figure out what to do! To read the full 27-page Scope of Work, click here. I will also post this document for future reference in the Reports page of this web site under a new tab titled Lake Houston Dam Spillway Improvement Project.
Posted by Bob Rehak on 5/1/2020
976 Days after Hurricane Harvey