Whittling Down the San Jacinto West Fork Mouth Bar

The State of Texas, Harris County and the City of Houston are whittling down the mouth bar of the San Jacinto West Fork – teaspoon by teaspoon. Just kidding; it only feels that way.

At the planned rate, the partners will remove approximately one third to one half of the planned 400,000 cubic yards of sediment by the start of hurricane season. But after waiting two and a half years since Hurricane Harvey, any and all progress is welcome! I’m not complaining.

The Mouth Bar Immediately After Harvey

Harvey deposited massive amounts of sediment in the area where the San Jacinto meets Lake Houston.

The mouth bar two weeks after Hurricane Harvey. With the exception of the treed areas on the extreme right, Harvey deposited virtually all the sand you see here plus more that you can’t see underwater.

The Army Corps of Engineers dredged a 600-acre area south of the mouth bar three feet deeper last summer. However, they barely touched the part of the mouth bar above water.

The mouth bar created a sediment dam behind the Lake Houston Dam that contributed to flooding more than 4100 structures in the Humble, Kingwood, and Atascocita areas.

Why Mouth Bar Formed Where It Did

The mouth bar formed where it did because the river water slows down when it meets the lake. The lower velocity causes sediment to drop out of suspension and accumulate faster.

While the Corps used hydraulic dredging to remove 500,000 cubic yards from the mouth bar in three months, the current phase uses mechanical dredging. Partners hope to remove another 400,000 cubic yards in 12 months. The process resembles whittling in that workers remove small chunks at a time.

Big Machines Dwarfed by Size of Job

Mechanical dredging uses large excavators. They load the sediment on pontoons. Tugs then push the pontoons upriver to a placement area. There, skid loaders remove the sediment and put it in trucks. The trucks cart it inland.

The excavators are currently nibbling away at the southern edge of the bar. I took all photos below on 3/6/2020.

Excavators are nibbling row after row, like from an ear of corn. This shot shows the immensity of the task.
They load one pontoon while another waits. The West Fork now has its own shuttle service. Unfortunately, round trip is still more than two hours.
These double pontoons can carry an estimated 160 cubic yards. Project goal: 400,000 cubic yards. That’s about 2,500 round trips for the pontoons.
Keeping the pontoon balanced requires coordination.
Tugs then push the pontoons upstream.
Dock of the placement area on Berry Madden’s property south of the West Fork, opposite River Grove Park boat dock on north shore.
From there, trucks haul the sediment inland out of the floodway, about a mile from the river. And the cycle repeats itself.

Mechanical vs. Hydraulic Dredging

The whole process resembles a five-mile long conveyor belt. It involves excavators, pontoons, tugs, trucks and more. Both mechanical and hydraulic dredging have advantages and disadvantages. Hydraulic dredging takes more time to mobilize, but re-suspends less sediment, and costs less per cubic yard of sediment removed. Mechanical dredging, on the other hand, can mobilize much faster.

At this point, returning to hydraulic dredging feels like a distant dream. No one is commenting on the possibility. But this picture speaks volumes.

Former Army Corps command post for West Fork Emergency Dredging project

It shows the once-bustling, but now-empty Army Corps command post. Just three months ago, it was filled with dredge pipe, spare parts, construction trailers, pontoons, booster pumps, survey boats, and more. Getting all that equipment back will be difficult.

Posted by Bob Rehak on 3/12/2020

926 Days since Hurricane Harvey

Houston Parks Board Makes Progress on Greenbelt Project South of Hamblen

Houston Parks Board continues making progress on creating a San Jacinto Greenway with a hike-and-bike trail. Their vision: to connect the Spring Creek Greenway to Kingwood’s trail network. They would do that by creating a trail between Hamblen Road and the West Fork. The trail would extend from the US59 pedestrian bridge near Harris County’s planned Edgewater Park to Woodland Hills Drive near River Grove Park.

Location of Demo Work

To clear a path for the greenway, the Houston Parks Board has acquired a property along Northshore Drive. It’s west of Sweet Bay Street and south of Hamblen Road (see map below).

Starting March 19, Houston Parks Board will begin demolishing structures on this property.

Schedule

The contractor will be Cherry Demolition. Their trucks will use Hamblen Road and Northshore Drive.

The job will start Thursday, March 19. It will run through Thursday, March 26, from 7 a.m. to 5 p.m.

If you see heavy equipment in the area, that’s what it is about.

Edgewater Park Still Planned, Just Delayed

Precinct Four still plans to construct Edgewater Park. Their plans have been delayed by reconstruction of the railroad bridge and changing design criteria. More news on the county’s plans in an upcoming post.

Posted by Bob Rehak on 3/12/2020

926 Days after Hurricane Harvey

Five Exposed HVL Pipelines Go Undercover; More Wetlands Drained

Five pipelines carrying highly volatile liquids (HVL) through the utility corridor that crosses the LMI River Road sand mine in Conroe have been buried again. Repairs have almost finished. Last Friday, crews were removing construction equipment and cleaning up. This significantly reduces risk to the public from a pipeline leak, rupture or explosion.

Erosion Triggered by Mining Too Close to Utility Corridor

Erosion from the mine first exposed the pipelines in 2014. The pipelines and mine reportedly argued about the fix in court for years. But after publication in December of aerial photos showing shoddy temporary fixes and badly sagging pipelines, residents lodged numerous complaints with the TCEQ, Mine Safety and Health Administration, Texas Railroad Commission, and the US Pipeline and Hazardous Materials Safety Administration.

Materials Stockpiled by January

Major repairs started in January. Contractors started stockpiling culvert, riprap, sand and other construction materials onsite.

Start of repairs. Photo taken January 20, 2020.

Construction Half Done in Mid-February

Construction was well underway a month later in February.

February 13, 2020

Cleanup Begins Early March

Last Friday, it was all over but the cleanup. Of course, cleanup in a sandmen is a relative term.

Looking north at utility corridor and pipeline repairs from over the mine’s main pit. This photo and those below taken on March 6, 2020.
Looking south toward main pit and river. Water flows from behind the camera position into these inlet pipes. Note the concrete overflow spillway to reduce future erosion.
A ditch not channels water to the new culverts. It also intercepts water flowing south toward the river (upper left).
Where the ditch turns toward the culvert, it appears to be 10 to 15 feet deep.
Reverse shot. Looking NE. Unfortunately, mining and erosion seem to have drained the wetlands.

Clogged Culvert a Future Risk

A big issue in the future may be sediment clogging the culverts.

Looking at all the sediment spewing from the culverts, one has to worry a bit about those culverts becoming clogged with sand and silt. No shortage of that around here!

Sadly, the wetlands lost since this episode started might have prevented some of that erosion.

Thanks to everyone who wrote regulatory agencies and complained about this situation. It helped produce a quick, happy resolution. Let’s chalk one up in the win column.

Posted by Bob Rehak on 3/11/2020

925 Days after Hurricane Harvey