A “mouth bar” is a sandbar that builds up at the mouth of a river where it meets a standing body of water, such as Lake Houston. The West Fork of the San Jacinto has a world-class whopper of a mouth bar.
How and Why Mouth Bars Form
A mouth bar forms when water in the river slows down as it spreads out in a standing body of water. The lower velocity of the river can no longer suspend particles of sediment. According to academic and petroleum geologists I talked to, this phenomenon exists in rivers everywhere. In fact, mouth bars are an essential element of delta formation.
Sequence of Events in Formation
As a mouth bar grows in height and emerges from the river, it backs water up and slows it down. This causes the river upstream of the mouth bar to gradually fill with sediment, ultimately choking the river and forcing it to seek a new path. At this point, the higher pressure created by the backwater forces the river to seek new channels. At this point, typically the river splits into two (bifurcates). This accounts for the branching structures found in most deltas.
That is exactly what’s happening where the West Fork of the San Jacinto meets Lake Houston as this series of time-lapse images shows. Note the growth of the mouth bar in areas highlighted in white below.
2011 image of the mouth bar where the West Fork of the San Jacinto meets Lake Houston. Note how bar has formed at tip of main channel.
By 2013, the mouth bar had taken on a triangular shape where it was starting to split the main flow of the river.
Image taken on the last day of 2016. The mouth bar grew considerably in the Tax Day and Memorial Day floods in 2015 and 2016, primarily by extending its length.
October 2017. During Hurricane Harvey, the mouth bar doubled in size. It definitely splits the flow of the river now.
On 9/14/17, the bar looked like this from a helicopter.
Approximately two-thirds of the homes damaged by flooding in the upper Lake Houston area were between this bar and where the U.S. Army Corps of Engineers will stop dredging.
Historical Context: A Lesson in Geomorphology
The growth of this mouth bar was predictable. Brown & Root said in 2000 that it would emerge exactly where it did. What will happen in the future if we don’t dredge it? That, too, is predictable. See this presentation by William Dupré, professor of geosciences at the University of Houston. Professor Dupré’s presentation, given at the Houston Geological Society April conference on flooding, contains excellent illustrations of how rivers migrate laterally over time.
Consequences of Not Dredging
A retired chief geologist for a leading oil company (who specialized in sedimentation) tells me that if this bar is not dredged, we could expect the following consequences. It will, he says:
Continue to grow in height, width and length.
Slow down and back up water behind it.
Force increased sedimentation upstream (including areas soon to be dredged)
Likely also increase the frequency and magnitude of overbank flooding upstream of the mouth bar
Jeopardize homes, bridges, pipelines and other infrastructure on both sides of the river as it branches.
Two Options for Dredging
The contract that the Army Corps of Engineers expects to sign with a dredging vendor does NOT currently include this bar in its scope. I wish it did for all the reasons listed above.
The proposed contract includes a clause that allows expansion of scope if both the Corps and Contractor agree on it. That would be the most cost efficient way to address this problem. Dredges will already be on the river. Millions of dollars of mobilization costs for second dredging project could be avoided and the issue could be addressed sooner.
However, if expanding the scope of the Corps project is not possible, I believe residents of the Lake Houston area should insist that the County covers it in the upcoming flood bond referendum.
Posted by Bob Rehak on 6/23/2018
298 Days since Hurricane Harvey
00adminadmin2018-06-23 09:33:092018-06-23 10:57:33The Case for Dredging the “Mouth Bar”
The U.S. Army Corps of Engineers Galveston District opened three dredging bids today and announced that RLB Contracting, Inc., was the apparent low bidder in the amount of $33,988,050.00 for emergency dredging of the West Fork of the San Jacinto River.
This giant sandbar almost completely blocks the west fork of the San Jacinto River just downstream from River Grove Park. It is one of the shoals that the Corps will remove to restore channel capacity.
Scope and Duration of Project
“This emergency project funded by FEMA involves the removal of 1.8 million cubic yards of material within 270 days,” said Curtis Cole, a contracting official with the USACE Galveston District’s Contracting Division. Cole said there will be a bid and pre-award verification phase with the awardee prior to officially awarding the contract. ”
Pre-Award Verification Needed Due to Wide Variance in Dredging Bids
“Pre-award verification allows the Corps to exercise due diligence to verify awardees can meet the scheduling, production and resource requirements,” said Don Carelock, a USACE Galveston District Chief of Construction. “Once we perform our analysis, a recommendation will be announced to our contracting officials.” Carelock said this process is expected to take between 10-14 days.
During the public opening, three bids were received: CrowderGulf submitted a bid in the amount of $108,887,733.33 and Great Lakes Dredge and Dock Company bid totaled $69,814,060. RLB Contracting, Inc. was announced as the apparent lowest bid of $33,988,050.00. Here is a breakdown of dredging bids.
Purchasing agents in many industries expect that if bidders work off the same specs and have comparable capabilities, bids should come in within 10-20% of each other. Often they come in much closer. In this case, the difference between the high and low bidder was more than 3X, a result that merits verification before awarding the contract.
Restoring to Pre-Harvey Conditions
Under provisions of the Stafford Disaster Relief Act of 1988, FEMA responded to a request from the State of Texas and directed the Corps to begin the initial assessment for the Emergency Project.
Corps officials have stated the FEMA funding scope of the project allows for debris and dredge activity that restores the area to it’s pre-Harvey flood conditions. The project is limited in scope and does not include operations beyond the west fork of the San Jacinto area.
Corps survey teams from the New Orleans District began collecting data in April to determine the level of shoaling and silt accumulation within the West Fork of the San Jacinto River. A six-phase value engineering study was completed in May.
Posted 6/22/2018 by Bob Rehak
297 Days from Hurricane Harvey
00adminadmin2018-06-22 17:29:362018-06-22 18:51:34U.S. Army Corps Opened Dredging Bids Today, but Award Delayed Due to Wide Variance
The U.S. Army Corps of Engineers extended the bid deadline again for its West Fork Emergency Dredging Project. The new bid deadline is Friday, June 22, 2018.
Discussions with potential vendors caused the delay for the FEMA funded project as both vendors and the Corps tried to nail down the exact volume of sediment to be removed. The Corps emphasized that it is restoring a 2+ mile stretch of the West Fork to pre-Harvey conditions. The pre-Harvey requirement comes with FEMA dollars which can only be used to return an area to the condition it was in before the storm.
At River Grove Park, this sandbar blocks the drainage ditch that empties the western third of Kingwood. It grew a quarter mile in length and 12 feet in height during Hurricane Harvey. More than 650 homes flooded in areas north of this sandbar. The Corps’ emergency dredging project will start here and extend past the West Lake Houston Parkway Bridge.
Projected Volume More than Doubles
Forecasted dredging material calculations increased from 748,000 to 1.8 million cubic yards of material that has shoaled. Shoaling is an area of shallow water, especially one that is a navigational hazard. In this case, shoals blocked the main channel of the San Jacinto as well as drainage ditches, such as the one at River Grove Park.
Completion Date Extended 90 Days to Accommodate Extra Volume
Because the volume of sediment to be removed has more than doubled, the Corps has also extended the completion date of the project from 180 to 270 days.
“We’ve encouraged bidders to submit questions and this allowed us to revise dredging quantities,” said Gary Stangeland, Interim Chief of Emergency Management at USACE Galveston District. “We were able to recalculate the volume of material needed and therefore extended the bid deadline and project finish date.”
Extending the project 90 days should allow the winning contractor enough additional time to remove the increased volume of materials.
The Corps’ contracting officers reposted the bid deadline date to a site used by vendors to receive notice on government opportunities. The site is accessible to the public at: Federal Business Opportunities website: https://www.fbo.gov
New Opening Date: Friday at 10 a.m.
“Our process is equitable and efficient as it allows for Corps’ Engineers to interact with vendors that will help us to restore the area to pre-Harvey conditions and help reduce future flooding risks,” said Jeff Neill, USACE Galveston District Contracting Chief, “We’ve publicly posted responses to bidders’ questions to www.projnet.org.” Neill said bids will be opened on June 22, 2018 at 10:00 a.m., local time.
No New Placement Areas for Spoils Anticipated
The physical length of the emergency dredging did not change, just the estimates of the volume of materials within the original area of interest. No additional placement areas for the spoils should be needed, according to the Corps. Stangeland said the two placement areas already identified should be sufficient to store the recalculated increase in forecasted dredged material.
The opening was initially scheduled for May 29, 2018. Even with the delays, this project will be one of the first coming out of Hurricane Harvey that the Corps will complete.
Posted June 21, 2018, by Bob Rehak
296 Days since Hurricane Harvey
00adminadmin2018-06-20 19:51:102018-06-21 06:28:16Army Corps Extends Bid Deadline Again; Opening Now Expected June 22
The Case for Dredging the “Mouth Bar”
A “mouth bar” is a sandbar that builds up at the mouth of a river where it meets a standing body of water, such as Lake Houston. The West Fork of the San Jacinto has a world-class whopper of a mouth bar.
How and Why Mouth Bars Form
A mouth bar forms when water in the river slows down as it spreads out in a standing body of water. The lower velocity of the river can no longer suspend particles of sediment. According to academic and petroleum geologists I talked to, this phenomenon exists in rivers everywhere. In fact, mouth bars are an essential element of delta formation.
Sequence of Events in Formation
As a mouth bar grows in height and emerges from the river, it backs water up and slows it down. This causes the river upstream of the mouth bar to gradually fill with sediment, ultimately choking the river and forcing it to seek a new path. At this point, the higher pressure created by the backwater forces the river to seek new channels. At this point, typically the river splits into two (bifurcates). This accounts for the branching structures found in most deltas.
That is exactly what’s happening where the West Fork of the San Jacinto meets Lake Houston as this series of time-lapse images shows. Note the growth of the mouth bar in areas highlighted in white below.
2011 image of the mouth bar where the West Fork of the San Jacinto meets Lake Houston. Note how bar has formed at tip of main channel.
By 2013, the mouth bar had taken on a triangular shape where it was starting to split the main flow of the river.
Image taken on the last day of 2016. The mouth bar grew considerably in the Tax Day and Memorial Day floods in 2015 and 2016, primarily by extending its length.
October 2017. During Hurricane Harvey, the mouth bar doubled in size. It definitely splits the flow of the river now.
On 9/14/17, the bar looked like this from a helicopter.
Approximately two-thirds of the homes damaged by flooding in the upper Lake Houston area were between this bar and where the U.S. Army Corps of Engineers will stop dredging.
Historical Context: A Lesson in Geomorphology
The growth of this mouth bar was predictable. Brown & Root said in 2000 that it would emerge exactly where it did. What will happen in the future if we don’t dredge it? That, too, is predictable. See this presentation by William Dupré, professor of geosciences at the University of Houston. Professor Dupré’s presentation, given at the Houston Geological Society April conference on flooding, contains excellent illustrations of how rivers migrate laterally over time.
Consequences of Not Dredging
A retired chief geologist for a leading oil company (who specialized in sedimentation) tells me that if this bar is not dredged, we could expect the following consequences. It will, he says:
Two Options for Dredging
The contract that the Army Corps of Engineers expects to sign with a dredging vendor does NOT currently include this bar in its scope. I wish it did for all the reasons listed above.
The proposed contract includes a clause that allows expansion of scope if both the Corps and Contractor agree on it. That would be the most cost efficient way to address this problem. Dredges will already be on the river. Millions of dollars of mobilization costs for second dredging project could be avoided and the issue could be addressed sooner.
However, if expanding the scope of the Corps project is not possible, I believe residents of the Lake Houston area should insist that the County covers it in the upcoming flood bond referendum.
Posted by Bob Rehak on 6/23/2018
298 Days since Hurricane Harvey
U.S. Army Corps Opened Dredging Bids Today, but Award Delayed Due to Wide Variance
The U.S. Army Corps of Engineers Galveston District opened three dredging bids today and announced that RLB Contracting, Inc., was the apparent low bidder in the amount of $33,988,050.00 for emergency dredging of the West Fork of the San Jacinto River.
This giant sandbar almost completely blocks the west fork of the San Jacinto River just downstream from River Grove Park. It is one of the shoals that the Corps will remove to restore channel capacity.
Scope and Duration of Project
“This emergency project funded by FEMA involves the removal of 1.8 million cubic yards of material within 270 days,” said Curtis Cole, a contracting official with the USACE Galveston District’s Contracting Division. Cole said there will be a bid and pre-award verification phase with the awardee prior to officially awarding the contract. ”
Pre-Award Verification Needed Due to Wide Variance in Dredging Bids
“Pre-award verification allows the Corps to exercise due diligence to verify awardees can meet the scheduling, production and resource requirements,” said Don Carelock, a USACE Galveston District Chief of Construction. “Once we perform our analysis, a recommendation will be announced to our contracting officials.” Carelock said this process is expected to take between 10-14 days.
During the public opening, three bids were received: CrowderGulf submitted a bid in the amount of $108,887,733.33 and Great Lakes Dredge and Dock Company bid totaled $69,814,060. RLB Contracting, Inc. was announced as the apparent lowest bid of $33,988,050.00. Here is a breakdown of dredging bids.
Purchasing agents in many industries expect that if bidders work off the same specs and have comparable capabilities, bids should come in within 10-20% of each other. Often they come in much closer. In this case, the difference between the high and low bidder was more than 3X, a result that merits verification before awarding the contract.
Restoring to Pre-Harvey Conditions
Under provisions of the Stafford Disaster Relief Act of 1988, FEMA responded to a request from the State of Texas and directed the Corps to begin the initial assessment for the Emergency Project.
Corps officials have stated the FEMA funding scope of the project allows for debris and dredge activity that restores the area to it’s pre-Harvey flood conditions. The project is limited in scope and does not include operations beyond the west fork of the San Jacinto area.
Corps survey teams from the New Orleans District began collecting data in April to determine the level of shoaling and silt accumulation within the West Fork of the San Jacinto River. A six-phase value engineering study was completed in May.
Posted 6/22/2018 by Bob Rehak
297 Days from Hurricane Harvey
Army Corps Extends Bid Deadline Again; Opening Now Expected June 22
The U.S. Army Corps of Engineers extended the bid deadline again for its West Fork Emergency Dredging Project. The new bid deadline is Friday, June 22, 2018.
Discussions with potential vendors caused the delay for the FEMA funded project as both vendors and the Corps tried to nail down the exact volume of sediment to be removed. The Corps emphasized that it is restoring a 2+ mile stretch of the West Fork to pre-Harvey conditions. The pre-Harvey requirement comes with FEMA dollars which can only be used to return an area to the condition it was in before the storm.
At River Grove Park, this sandbar blocks the drainage ditch that empties the western third of Kingwood. It grew a quarter mile in length and 12 feet in height during Hurricane Harvey. More than 650 homes flooded in areas north of this sandbar. The Corps’ emergency dredging project will start here and extend past the West Lake Houston Parkway Bridge.
Projected Volume More than Doubles
Forecasted dredging material calculations increased from 748,000 to 1.8 million cubic yards of material that has shoaled. Shoaling is an area of shallow water, especially one that is a navigational hazard. In this case, shoals blocked the main channel of the San Jacinto as well as drainage ditches, such as the one at River Grove Park.
Completion Date Extended 90 Days to Accommodate Extra Volume
Because the volume of sediment to be removed has more than doubled, the Corps has also extended the completion date of the project from 180 to 270 days.
“We’ve encouraged bidders to submit questions and this allowed us to revise dredging quantities,” said Gary Stangeland, Interim Chief of Emergency Management at USACE Galveston District. “We were able to recalculate the volume of material needed and therefore extended the bid deadline and project finish date.”
Extending the project 90 days should allow the winning contractor enough additional time to remove the increased volume of materials.
The Corps’ contracting officers reposted the bid deadline date to a site used by vendors to receive notice on government opportunities. The site is accessible to the public at: Federal Business Opportunities website: https://www.fbo.gov
New Opening Date: Friday at 10 a.m.
“Our process is equitable and efficient as it allows for Corps’ Engineers to interact with vendors that will help us to restore the area to pre-Harvey conditions and help reduce future flooding risks,” said Jeff Neill, USACE Galveston District Contracting Chief, “We’ve publicly posted responses to bidders’ questions to www.projnet.org.” Neill said bids will be opened on June 22, 2018 at 10:00 a.m., local time.
No New Placement Areas for Spoils Anticipated
The physical length of the emergency dredging did not change, just the estimates of the volume of materials within the original area of interest. No additional placement areas for the spoils should be needed, according to the Corps. Stangeland said the two placement areas already identified should be sufficient to store the recalculated increase in forecasted dredged material.
The opening was initially scheduled for May 29, 2018. Even with the delays, this project will be one of the first coming out of Hurricane Harvey that the Corps will complete.
Posted June 21, 2018, by Bob Rehak
296 Days since Hurricane Harvey