Tag Archive for: erosion

HCFCD About to Start Next Phase of Kingwood Diversion Ditch Repairs

On Monday, July 13, Harris County Flood Control District (HCFCD) plans to begin more repairs to the Kingwood Diversion Ditch. In June, HCFCD repaired severe erosion near Walnut Lane between Trailwood and Forest Cove. The new repairs will begin farther down the ditch between Forest Cove and Deer Ridge Estates, just north of Deer Springs Drive. See map below.

Area of new repairs outlined in red. For reference, Kingwood’s Deer Ridge Park is in upper right. The outlined area shows where trees will be removed and is approximate.

Ditch To Be Straightened, Erosion Repaired

HCFCD plans to straighten the ditch and repair erosion. That will require the removal of trees which have grown up in the ditch and along its banks. See below.

In the area to be repaired, erosion and vegetation have made the ditch deviate from its normal course over time. The red line indicates the original path. The purple line indicates the current patch. Source: HCFCD.
Severe erosion threatens trails, safety and homes on both sides of the ditch.
Trees have grown up in the ditch, reducing its conveyance and blocking floodwaters.
To repair erosion and restore ditch, trees will need to be removed.

Bird Survey Finds No Nests Impacted

HCFCD has not specified the number of trees it will remove. However, the District has conducted a Bird Survey to ensure repairs will not impact any active nests near the portion of the Kingwood Diversion Ditch undergoing repair.

Protecting Homes from Future Erosion

“We will work to minimize the impacts to trees and nature, but we need to be able to get our equipment in to make repairs,” said Beth Walters, a spokesperson for HCFCD. “We do not know exactly how many trees will need to be removed. Unfortunately, it will be noticeable, but the repair will protect fences and homes from future erosion.”

Property threatened by diversion ditch erosion. Photo from January 2019.

Posted by Bob Rehak on 7/8/2020

1044 Days since Hurricane Harvey

HCFCD Finishes Repair of Kingwood Diversion Ditch At Walnut Lane

Harris County Flood Control District (HCFCD) has finished construction work on the repair of erosion in the the Kingwood Diversion Ditch near Walnut Lane between Forest Cove and Trailwood. HCFCD still has to plant grass, but the heavy lifting is done.

Before, During and After Photos

The pictures below show the way the ditch near Walnut Lane was and how it looks today.

Kingwood Diversion Ditch south of Walnut Lane in 2009. Giant slabs of the slope were starting to break way and were swept downstream. It got worse after that. Notice distance to power lines in background and compare with last photo.
HCFCD Diversion Ditch repairs in Kingwood in early June 2020.
The “after shot.” How it looked on 6/27/2020
And here’s how it looks from the air. Walnut Lane Bridge on left. Photo taken 6/16/2020. Compare how much closer the erosion eventually got to the power lines in this photo with the first photo above.

Posted by Bob Rehak on 6/29/2020

1035 Days since Hurricane Harvey

Perry Detention Ponds Pass First Modest Test, But Eroded Badly

The official rain gage at West Lake Houston Parkway and the West Fork San Jacinto recorded 2.32 inches of rain between 7 and 9 a.m. this morning. That was officially a 1-year rain. (See Atlas-14 chart below.) As rains go, it was not a severe test; it was more like a pop quiz.

After the rain subsided, Taylor Gully in Elm Grove was less than half full.

The good news: Taylor Gully was well within its banks and no one in Elm Grove or North Kingwood Forest flooded. The bad news: Perry’s detention ponds experienced severe erosion, enough to warrant repairs and perhaps delay the schedule.

The even worse news: Harris County’s meteorologist, Jeff Lindner predicts another one to two inches of rain tonight with isolated totals of three to four.

West Lake Houston Pkwy. Gage Showed 2.32 Inches In 2 Hours

24 hour rain totals for WLHP gage showed bulk fell in 2 hours.

2.32 inches in two hours qualifies as a one-year rain according to the new Atlas-14 rainfall precipitation frequency estimates. Even if you considered the entire 3.12 inches in 24 hours, it would still only be a one year rain.

Atlas 14 Precipitation Frequency Table for the Kingwood Area.

Aerial Images Show How Perry Detention Ponds Performed

These aerial images taken shortly after noon today when the rain stopped show that:

  • The detention ponds are starting to do their work and hold back water.
  • That kept the level in Taylor Gully manageable
  • The overflow spillway between S2 and the concrete-lined channel was apparently not needed.

However, the images also show that:

  • Portions of the detention pond walls severely eroded and appear to have collapsed in places.
  • The water in the N1 pond overcame temporary dirt barricades sending water and silt down to N2.
  • The newly excavated N2 was entirely covered with water for the first time. It also received a significant amount of erosion.
  • N3 merges with Taylor Gully to form one large detention pond that holds water all the way from the northern end of the pond to the county line.
  • Rain has halted construction for the last two days and could delay it into next week.
Expanded, giant N2 detention pond was covered entirely with water for first time. Looking West toward western border of Woodridge Village.
However, erosion re-deposited large amounts of soil within the pond. Looking North along Western Border of Woodridge Village.
Rainwater entering the site from Joseph street in Porter (center left) shows by comparison how much silt the Perry water held. Looking north along western border of Woodridge Village.
Still looking north, but farther up western border, you can see silt slumping into ditch.
Looking SE toward Elm Grove and North Kingwood Forest from the NW corner of site. Water coming in N1 pond from left exited right, down the western border. Water washed out a temporary dirt barrier that appeared designed to hold water in the pond.
Looking east. Note erosion from former utility corridor on left that has turned into a new drainage ditch along northern edge of property.
Looking at western wall of N3 which runs along eastern border of Woodridge Village.
Another portion of the western wall of N3 shows severe erosion.
Standing water from rest of property is slowly making its way into detention ponds.
Looking South along eastern border toward Taylor Gully. At present, N3 (bottom left) simply merges with the concrete channel by S2 (top right). It appears to have nothing to control the outflow.
Looking north along eastern border. Silt fences prove inadequate at stopping erosion. In fact, most of site has no silt fences.

More Rain Likely Tonight

Jeff Lindner, Harris County meteorologist, says that today’s wet pattern should remain in place through the weekend, contrary to earlier predictions that saw rain chances ending by Friday.

Storms currently in the Gulf near Corpus Christi are tracking toward Houston late tonight and Friday morning. They will probably not be as severe as this morning’s storms. With that said…the air mass remains tropical over the region and excessive rainfall rates of 2-3 inches per hour will be possible, warns Lindner.

As of 6 p.m. Thursday, the National Weather Service decided NOT to issue another flash flood watch for tonight, but stay alert to see if a more significant threat may develop.

Expect rainfall amounts of generally 1-2 inches tonight with isolated totals of 3-4 inches.

To Get Up-to-the-Minute Forecasts and Stream Alerts

You can always find up to the minute weather forecasts at this National Weather Service page.

To check on rising rivers and major streams, visit the Harris County Flood Warning System, and click on channels and channel status simultaneously. To see further upstream, click on All Gages. That will show you the status of gages operated by the SJRA in Montgomery County.

Posted by Bob Rehak on 6/25/2020

1031 Days since Hurricane Harvey and 280 since Imelda

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.

Erosion: Sometimes Sudden

Erosion can sometimes be sudden. It’s not always a slow process of water grinding away at dirt and dissolving it, or wearing down rocks. This post will examine several examples around us and look at their implications. I intend it as a continuation of yesterday’s post about ditch maintenance.

The Northpark Woods development (right) on the West Fork San Jacinto River (background)

There are four main types of erosion.

  • Hydraulic action – When rapidly moving water churns against river banks and scours or undermines them.
  • Abrasion – Caused by small pebbles moving along a river bank or bed and knocking other particles loose. Think of sandpaper.
  • Attrition – When rocks carried by the river knock against each other. They break apart to become smaller and more rounded. This is how boulders turn into gravel.
  • Solution – When water dissolves certain types of rocks, for example limestone. We often see this in Florida, where sinkholes frequently develop.

Most of these processes happen slowly. But the first can be sudden. One storm. One flood. And boom. That river bank where you used to sit and quietly contemplate nature is gone.

Now You See It; Now You Don’t

Sometimes large slabs of a river bank or ditch suddenly slump into a river, almost like mini landslides. One flood expert commented on the picture above; he said “The owners of those new homes may suddenly find the ditch in their backyards.”

At other times, the size of a flood forces a river to widen. We saw this during Harvey and Imelda. The relentless pounding of flood waters carries away everything in their path. Cutbanks (the outside of a river bend) are especially vulnerable. Water slams directly into them like a firehose and washes them away. This action actually changes the course of a river over time.

Most of the time, it happens so slowly, we barely notice it. But during large floods, it’s sometimes sudden, large, and devastating to homeowners or businesses near rivers.

Three More Examples of Hydraulic Action

Example A: East End Park
East End Park in Kingwood. In 2019, the San Jacinto East Fork removed approximately 50-100 feet of river bank during Imelda, including this part of the Overlook Trail.
Example B: Balcom House and River Migration
Note a long peninsula south of the Balcom House on the San Jacinto West Fork before Hurricane Harvey.
After one monster storm, the peninsula was gone. The Balcoms lost 175 feet of riverfront property.
Example C: River Aggregate Mine on West Fork in Porter

The third example comes from the abandoned River Aggregates sand mine beyond the new development in the first picture above. It’s a spectacular example of river migration.

In this case, the San Jacinto West Fork migrated 258 feet toward the mine’s dike in 23 years. When I first photographed the dike after Harvey, the river had eaten away an average of 12.4 feet per year. At the time, the dike was only 38 feet wide, and I predicted it could soon fail. It did. Within approximately a year.

Image taken on 9/14/2017, shortly after Hurricane Harvey. At the time, only 38 feet stood between the abandoned mine in the background that the San Jacinto west fork in the foreground.
Note how the pond in the foreground disappeared when the river took the last 38 feet of river bank.

Wait a minute, you say! What happened to the pond. After the river bank collapsed, the pond drained, exposing sediment already within it. And the action of draining concentrated more sediment in it, like all the remnants of food trapped in your sink drain after you’re done washing dishes.

History of Pond

The missing, shallow pond in the foreground above used to be the settling pond for River Aggregates.

This satellite image from 2004 shows that River Aggregates used the missing pond as a settling pond.
This is how the mine looked in 2017 after River Aggregates abandoned it. Note river bank is still intact.
This is how the abandoned mine looked in January of 2019. The river bank was gone. The pond had drained. And a steady stream of silty water from other ponds leaked into the West Fork.

Here’s how it looks today from a helicopter.

River Aggregates mine now leaks a steady stream of silty water into the West Fork San Jacinto. This is the same area as above, but from the reverse angle.

Lessons of Life Near a River

Most people never live long enough to see massive changes such as these in rivers. In most places, river change happens on a geologic time scale. But along the Gulf Coast, hurricanes can create floods that make rivers change on a human time scale, as these examples have shown.

What can we deduce from this?

  1. Around here, we need to give rivers room to roam. Parks, green spaces, and golf courses, often represent the highest and best use of land near a river, bayou or ditch.
  2. Building too close to rivers, bayous and drainage ditches can be costly. Disturbing wetlands and topsoil accelerates erosion. That, in turn, can threaten everything in its path. Be prepared to maintain anything you build near a watercourse, including the watercourse itself. And be prepared to fight what ultimately becomes a losing battle.
  3. We need greater separation between mines and the San Jacinto river. Keep mines out of the meander belt. They worsen downstream sedimentation. And as we have seen, that can contribute to sediment build ups that require public money to remove. The alternative, leaving them in place, contributes to flooding.

Here’s a current list of ditch maintenance projects in the Kingwood area.

Posted by Bob Rehak on 5/18/2020

993 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.

City Completes Repairs on Tree Lane Bridge, But Concerns Remain

The City of Houston has completed repairs on the Tree Lane Bridge over Ben’s Branch…at least for now. The City partially concreted a wing wall and placed riprap in the stream bed to help reduce erosion and scour. However, the root cause of the damage remains. Upstream development without adequate detention is funneling more and more water into Ben’s Branch. The higher volume will continue to contribute to scouring and erosion in major storms unless detention ponds upstream are built and fixed.

Water Under the Bridge

As I struggled to understand what I was looking at, an online search revealed this excellent 196-page, well-illustrated document. It’s titled “AN ILLUSTRATED GUIDE FOR MONITORING AND PROTECTING BRIDGE WATERWAYS AGAINST SCOUR.” Robert Ettema, Tatsuaki Nakato, and Marian Muste from the College of Engineering at the University of Iowa produced it for the Iowa Department of Transportation.

It begins with a maxim: “Person who overlooks water under bridge will find bridge under water.”

The document points out that bridge engineers often assume that a stream channel will maintain its course and dimensions. But most channels adjust their alignment and shape in response to floods and land-use changes in their watersheds. That has happened on Ben’s Branch in recent years.

“Channel changes sometimes have severe consequences for bridge waterways,” say the authors.

Scour and Progressive Degradation

A review of the entire paper reveals two types of destructive forces at work on the Tree Lane Bridge.

Long-term scour is one. It occurs over a time scale of several years, and usually includes progressive degradation and lateral bank erosion due to channel widening or meander migration.

Progressive degradation is another. It features the almost permanent lowering of the river bed at a bridge site owing to changes in the watershed [e.g., head-cut progression (head-cutting), or human activities (e.g., channel straightening or urbanization)]. 

The area around the Tree Lane bridge supports has been badly eroding for years. A 12-inch water line that was once buried 5 feet below the stream bed is now at the water surface. See below.

How the area downstream from the bridge looked in December before repairs started.

Scour and erosion under and around bridges are constant problems for engineers. This bridge is a great example. Any time a structure interrupts the flow of floodwater, it creates turbulence (vortices in the flow) that can lead to erosion.

From “AN ILLUSTRATED GUIDE FOR MONITORING AND PROTECTING BRIDGE WATERWAYS AGAINST SCOUR.”

During Harvey, scour destabilized the Union Pacific and US59 bridges across the West Fork. Both had to be replaced for safety.

The Tree Lane Bridge doesn’t appear to be to that point yet. But the heavier load placed on Ben’s Branch by new upstream developments, such as Woodridge Village, Woodridge Forest, and Brooklyn Trails, may be pushing this bridge beyond its design capacity.

Source: FEMA. Bridge constricts water flow (from top to bottom). The pressure of water stacking up behind the bridge forces the water to accelerate under the bridge, causing erosion and scour. See below.
Major storms in the last four years have eroded a large area immediately downstream from the bridge.

Concrete and Rip Rap Should Help in Short Term

To address these problems, the City repaired part of a concrete wing wall. They also placed riprap (boulders) downstream from the bridge and below a stormwater drain.

Riprap breaks up the flow of water and slows it down. This reduces erosion and scour.

Partially concreted wall (left) and riprap at Tree Lane Bridge over Ben’s Branch, Kingwood, TX. Photo courtesy of COH Public Works.
Tree Lane Bridge repairs, Kingwood, TX.
Tree Lane Bridge repairs, Kingwood, TX. Photo courtesy of COH Public Works.

…But Root Causes for Damage Remain

However, problems remain, both here and upstream.

  • That 12-inch water line could be taken out in the next flood by a tree flowing downstream. If the flood lasts for several days as it did during Harvey, the loss of water would be a major inconvenience to the residents of Bear Branch.
  • Inadequate detention upstream will continue to erode both the stream banks and bed at accelerating rates.

Until we can address the root causes of such damage, I fear that maintenance on this bridge will be a constant, long-term issue…despite the City’s best intentions.

Slabs of concrete still lean against water main.
In extreme event, water could still get behind concrete repair and peel it away from bank.

Posted by Bob Rehak on 3/31/2020

945 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.

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

Tree Lane Bridge over Ben’s Branch: Before and After Repairs

Yesterday, I posted about the hidden costs of flooding. Here’s another one: infrastructure repairs. And another one: re-doing infrastructure repairs. Like those to the Tree Lane Bridge over Ben’s Branch.

History of Issue

Upstream development in Montgomery County with insufficient and un-repaired detention pond capacity started dumping excess water into Ben’s Branch. It didn’t take long for the area under the Tree Lane bridge next to Bear Branch Elementary to start eroding badly.

Tree Lane was already a pinch point in the Ben’s Branch floodway. That and the combination of even more water during the Tax Day, Memorial Day, Harvey, May 2019, and Imelda floods all took a toll. The picture below shows what the bridge looked like on December 1, 2019. Hundreds of kids cross this bridge on their way to Bear Branch Elementary every day.

The Before Shot: Taken November 31, 2019

After taking the shot above, I emailed it to the City. To their credit, they sent crews out right away to repair it. Heavy equipment sat at the site for 2.5 months.

After the Repairs

About two weeks ago, the last piece left the job site. So today, I drove by to get an “after” shot. See the improvements below.

The After Shot: Taken 2/29/2020, three months later.

The City put rip rap across the creek to reduce erosion from water shooting out from the storm sewer in the upper right. They also broke up some of the large slabs of concrete to form additional rip rap.

However, it appears that they:

  • Have done little to stabilize the bridge supports.
  • Left slabs of concrete leaning against an exposed pipeline.
  • Threw a traffic sign and traffic cone into the creek.
  • Left about 50 bags of sand on the large slab at the left.

Someone else could have dumped the construction materials and sign. Crappy looking areas always encourage illegal dumping.

Enlargement of detail from previous shot showing sand that has been left behind or dumped.

I’m guessing that the rip rap may help reduce erosion from the storm sewer. But…

I see little here to stop erosion from upstream of Tree Lane or reduce danger to the pipeline. More important, the City did nothing to increase conveyance under the bridge.

The Tree Lane Bridge still forms a pinch point that restricts conveyance of Ben’s Branch.

Of course, the City may handle the conveyance issue in a second job. That could help build a case for doubling those drainage fees.

Posted by Bob Rehak on 2/29/2020

914 Days after Hurricane Harvey

Hidden Costs of Flooding

When we think about flooding, most of us don’t think beyond the repair costs of homes. But there are more costs to communities that can remain hidden for years. Erosion, for instance, is one of the hidden costs of flooding that we rarely talk about.

You’ve heard me talk about the eroded sediment from sand mines that winds up downstream in the mouth bars of the East and West Forks of the San Jacinto.

The City, County, State and Federal Government have already spent more than $100 million to remove eroded sediment that is blocking the West Fork of the San Jacinto and much more remains.

Likewise, many of you have seen the work being done now to remove approximately 80,000 cubic yards of eroded sediment from Ben’s Branch.

Ben’s Branch became virtually blocked with sand after Harvey. Harris County Flood Control is now removing the excess sediment to restore conveyance of the channel.

We’ve all seen how such eroded sediment can back water up and raise flood levels. And we’ve all seen how much that can cost. Not just from the initial flood, but in terms of remediation.

Look At the Cost of Erosion From the Upstream Side, Too

Ditch erosion can affect homeowners in other ways, too. By threatening their property and community property. Lost property is yet another one of the hidden costs of flooding.

We’ve seen how ditch erosion destroyed riding trails in the Commons on Lake Houston.

Ditch erosion in Commons on Lake Houston. Photo from January 2019.

In Deer Ridge Estates, ditch erosion is creeping inexorably toward back yard fences.

Kingwood diversion ditch where it crosses past Deer Ridge Estates just north of Deer Springs Drive. Photo from Jan. 2019.

On a recent flight down the San Jacinto West Fork, I spotted erosion threatening the back yards of homes still under construction in the new Northpark Woods subdivision.

Erosion can threaten pipelines, too.

Pipelines undermined by erosion at Liberty Materials Mine near Conroe.

Let’s Play Hot Potato

Who is responsible for repairing the upstream erosion when it happens? In Harris County, we’re lucky, we have a flood control district that has assumed responsibility for that. But the ditch two photos above is in Montgomery County. So are the pipelines in the photo above.

Who is responsibly for repairing erosion in these cases? The County? The homeowners? The homeowner association? The developer? The sand mine? The pipelines? A flood control or drainage district? Everyone wants to assume it’s someone else’s problem. No one wants to assume responsibility.

But without someone stepping up, these homes will eventually be threatened. And with the exception noted above, few people or groups are stepping up.

Paul Crowson, a Montgomery County flood activist has posted about this subject on Facebook. Says Crowson, “The county, the flood control district, the neighborhood HOA, the POA, the City, the State, the developers, the engineers … all are passing the blame and responsibility around to each other.”

The problem exists everywhere. Crowson points to the case of Fort Bend County homeowners who are petitioning the Court there to assign responsibility for maintenance of drainage easements.

“These poor people (in the court case) have lost most of their yard, and are in danger of losing their home to the ravages of the drainage easement nightmares,” says Crowson. “Those nightmares are growing every day and will eventually swallow them and their home. Why does it matter to you? I’m thinking right now of Roman Forest, Tavola, New Caney, and Montgomery County.”

It’s Easier to Keep Up Than Catch Up

I would argue that it’s cheaper to prevent a disaster in the making than to remediate a disaster after the fact. Remember those homely homilies your parents and grandparents tried to instill in you? An ounce of prevention is worth a pound of cure. A stitch in time save nine.

Congressman Dan Crenshaw says the Navy Seals have a similar saying for those who fall behind on those long training runs they take. “It’s easier to keep up than catch up.” They’re all true! And the same holds true for deferred maintenance.

When Deferred Maintenance Turns into a Disaster Area

Montgomery County does not have a flood control district. Nor does it seem especially eager to address problems, such as those in the photo above.

As we saw with the mouth bar on the West Fork that had been building up under water for decades, maintenance can be deferred for only so long.

Then a monster flood comes along like Harvey. It finds the weak points in systems…and boom. Deferred maintenance turns into a disaster area.

Posted by Bob Rehak on 2/28/2020 with input from Paul Crowson

913 Days after Hurricane Harvey

Detention Pond Construction: Montgomery vs. Harris County

Below are aerial images from two new developments under construction. They show two detention ponds in two different counties. Can you tell which is in Montgomery County and which is in Harris County? I took both photos on the same day, 2/13/2020.

Detention Pond A
Detention Pond B

Clue

Look where the grass has established itself:

  • In A, the land was cleared before the detention pond was completed.
  • In B, the detention pond was completed before the land was cleared.

And the Answer Is…

If you guessed that Pond A is in Montgomery County, you guessed correctly. Pond A is in Woodridge Village, just north of Sherwood Trails and Elm Grove. It is their S1 detention pond (first southern).

Pond B is in Harris County just north of Bush Intercontinental Airport and Mercer Botanic Gardens.

How You Can Tell

Montgomery County does not require developers to install detention ponds before they clearcut the whole development. So they sometimes come long AFTER clearcutting.

Also, even though Page 44 of Montgomery County’s Drainage Criteria Manual says that “slopes must be revegetated immediately after construction to minimize erosion,” no one apparently enforces the regulation. The sides of Pond A have gone without grass for about a year. See close up below.

Erosion on the sides of Pond A shown above, the Woodridge Village S1 detention pond.

All 268 acres of Woodridge Village have been clearcut for the better part of a year. Meanwhile Perry Homes and its engineering firm LJA are just now taking bids on additional detention ponds for the northern section. And the sides of Pond A still have yet to sprout grass.

Harris County Regs Differ

Note in the Pond B photo how the sides of the channel have been stabilized with grass before the developer has even finished clearing the land.

Harris County employs low-impact development procedures (LID). Harris County Stormwater Quality Management regulations discourage clearcutting giant sites like Woodridge Village all at once. See section 4.2.3.1, Stormwater Pollution Prevention (SWPPP) During Construction.

The text states, “The clearing, grubbing and scalping (mass clearing or grading) of excessively large areas of land at one time promotes erosion and sedimentation problems. On the areas where disturbance takes place the site designer should consider staging construction [emphasis added], temporary seeding and/or temporary mulching as a technique to reduce erosion. Staging construction involves stabilizing one part of the site before disturbing another [emphasis added].”

Two Different Approaches

You would think that preventing erosion would be cheaper than cleaning it up. Why do a job once when you can do it twice? Right?

Close up of remediation work in Pond A, from a slightly different angle. Photo taken 2/13/2020.

Evidently, Perry Homes prefers it that way. Last Thursday, I spotted men digging out the pilot channel of Pond A and restoring slopes…again. This was at least the third or fourth time. No wonder those Perry Homes are so expensive.

Posted by Bob Rehak on 2/16/2020

901 Days After Hurricane Harvey and 150 after Imelda

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.

Don’t Dig Near Pipelines: A TACA Safety Moment

The Texas Aggregate and Concrete Association (TACA) brags that its members uphold the industry’s highest standards for safety. Or did they mean daring? Let’s have a safety moment.

Myth Meets Reality on the West Fork

To shine a light on the difference between the myth and reality, I’ve taken up a new hobby: sand-mine photography from a helicopter. On my December flight up the West Fork of the San Jacinto, I flew over this mine. Note the wetlands and utility corridor in the middle. Also note the trench leading through the trees on the right to that open gap in the tree line along the utility corridor.

I was curious about that gap. So I asked the pilot to go closer and got the photo below. How strange, I thought! The pipeline corridor has washed out, like at the Triple PG Mine. But this was a little different. The mine appeared to be draining the wetlands. Note the river of muck in the photo below.

Enlargement Shows Makeshift Supports

Someone had rigged “supports” under five pipelines. See the enlargement below. I put supports in quotes because they don’t seem to be working very well; note the sagging. Some look more like clotheslines than pipelines under pressure.

Pipelines Carry Highly Volatile Liquids

Investigation showed this is the SAME utility corridor bisecting the Triple PG mine miles to the southeast in Porter. These are the same five pipelines carrying highly volatile liquids (HVL). This mine, however, lies on the West Fork of the San Jacinto in Conroe near 242.

The channel under the five pipelines is up to a 100 feet wide.

Historical Images in Google Earth Show How This Happened

An investigation of historical satellite images in Google Earth shows that erosion has been a problem in this area at least since 1995 – the date of the earliest available image. Water overflowing the wetlands tried to make its way to the river on the other side of the utility corridor. The problem was manageable, however, as long as the land was flat. That was until 2014.

In 2014, when the mine first started excavating next to the corridor, a process called headward erosion started. Water flows from top to bottom. Notice how much deeper and wider the erosion is below the corridor than above. See explanation below.

In 2014, two things happened. The mine started excavating right up to the edge of the pipelines (just as Triple PG did).

Next, three back-to-back-to-back monster storms in 2015, 2016 and 2017. They were “perfect storms” where the right combination of circumstances came together: Heavy rain. Exposed, loose soil. Steeper gradient.

How “Headward Erosion” Happens

The fact that miners had excavated up to the pipeline corridor with some very deep pits created a steep drop at the edge of the pipelines. That meant water crossing the corridor tended to accelerate and erode the sandy soil beneath the pipelines faster. The soil then sagged into the pit, much as you see in the pictures above. This process is well documented and has a name: headward erosion.

Here’s an illustration of how the process of headward erosion works

From Arizona’s Pinal County Dept. of Public Works, Page 123.

Here’s a 43-second YouTube video showing the process in action in a table-top flume experiment.

Makeshift Repairs Not Working All That Well

Trying to make the best of a bad situation, it appears that either the miners or the pipeliners tried to shore up their pipelines with supports. But it’s not working. They keep trying to plant grass. They keep using erosion control blankets. The supports keep sinking. And the pipelines keep sagging. Here’s an even bigger blowup.

It looks as if some of these supports are anchored in quicksand. Notice the extreme difference in their heights. The cross braces supporting the weight may be adjusted as the supports sink. But not on this day.

Another factor here: What if a tree washes down this chute during a torrential rain? It happens. Regularly.

I have a hard time imagining the stress on these pipelines. An engineer calculated a range of weights for me. He made some assumptions about the thickness of the pipes and the weight of liquids inside them. Then he calculated the weight of 100 feet. The range: 20,000 to 30,000 pounds. No wonder they’re sagging. That’s more than I weigh after a dinner at Carrabbas!

Probably No Imminent Danger, But Just in Case…

They’re probably not an imminent danger. But what happens in the next big storm? We’re overdue. It’s been more than two months!

Hundreds of thousands of gallons of flammable liquids. Under high-voltage electric lines. Pipes under stress. Erosion that widens with every storm. This should be a wake up call. But…

TACA has resisted all attempts at sensible regulation. They don’t even want to define and publish best practices. And it has long been known that you can’t legislate common sense. So I guess we are just stuck living on the edge with connoisseurs of edge work.

Where to File Complaints

If you would like to complain to someone, these people may be willing to listen.

TCEQ

Mine Safety and Health Administration (this puts miners at risk)

Texas Railroad Commission (responsible for pipelines in Texas)

US Pipeline and Hazardous Materials Safety Administration

Location of exposed pipelines: 30º11’56.63″N, -95º21’57.78″W

Office on 18214 East River Road in Conroe, TX

Highly Volatile Liquid (HVL) Pipelines Involved:

  • Plains Pipeline – Red Oak Pipeline (20”) moving crude
  • Enterprise Products Operating – Chapparral System (12.75”) – HVL Liquid (probably crude)
  • Mustang Pipeline – GLPL System (6”)  – HVL Liquid
  • Enterprise Products Operating – Texas Express Pipeline System (20”) – HVL Liquid
  • Phillips 66 Pipeline LLC – 8″ Products Pipeline

That concludes our safety moment.

Posted by Bob Rehak on 12/9/2019 with help from Josh Alberson

832 Days after Hurricane Harvey and 80 since Imelda

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.