detention pond Archives - Reduce Flooding

Impervious Cover Percentage Raises Downstream Concerns

The Preserve at Woodridge based its detention basin calculations on 65% impervious cover. But photos taken on 11/26/22, a full year after they cleared the land, suggest the impervious-cover percentage may have been dramatically understated.

That affects the amount and speed of runoff. And that raises concerns for downstream residents along Ben’s Branch, many of whom have flooded in recent years, in part because of dense upstream developments like this one.

Looking straight down reveals little dirt between the densely packed rental homes and the concrete surrounding them.

I continue to be amazed at how the developer claims that one third of this dense, concrete bungle is NOT “impervious cover.” And lest you think I selectively cropped the photo above to exaggerate the percentage of concrete, the shot below shows virtually the entire development.

*Taken 11/26/22*. *Area on right still does not have sidewalks.*

Pushing the Limits

At my age, I don’t like the idea of carrying groceries blocks from my car to my house – which I would potentially have to do here.

Nevertheless, to give credit where credit is due, it appears that this developer has a flair for pushing limits. Just look at the development’s website. They offer “unmatched amenities” like vinyl flooring.

And some homes are 660 square feet. Much smaller and you would expect the residents to wear orange jumpsuits.

But still, this new concept in luxury living has its rewards:

No stairs to climb like in apartments.
An extra wall between you and your neighbor’s stereo.
On-street parking, just like Manhattan.
147 parking spaces for 131 homes.
Plenty of nearby food-trucks.
A “Scream Park” and fireworks stand within walking distance.
No leaves to rake.
Your own toilet.

This is way better than life in a frat house. The stainless steel refrigerators are definitely a step up from Igloo coolers.

The only thing missing is a pet run that can accommodate a Chihuahua and Cocker Spaniel at the same time.

But seriously, this developer claims to have identified a niche between sleeping bags and starter homes. Perhaps the company will pioneer a new market and this will be the future of Montgomery County. To see their construction plans, click here.

Will Detention Basin Hold Enough?

I just hope their detention pond is big enough in case their impervious-cover calculations are off.

*Preserve at Woodridge detention basin is built to pre-Atlas 14 rainfall rates. It appears partially fenced in so that residents can’t walk around it.*

Montgomery County’s Subdivision Rules and Regulations specify that outfall ditches, such as the one in the photo above only need to carry a 25 year rain. (See page 9.) With that in mind, it seems that this detention pond would fill up quickly from ditch overflow in a 25-year rain and provide little detention benefit during 50- or 100-year rains. And that’s no joke.

Posted by Bob Rehak on 11/28/2022

1918 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.

KMS Demolition Accelerates

Kingwood Middle School demolition accelerated this week. On Tuesday, November 8, contractors had nibbled their way into a small area near the front door. But on Wednesday, Thursday and Friday, they took down about 20-25% of the building. They’re focusing on the west side right now and moving north.

If your kids enjoy watching big machines at work, share the pictures below.

Photos Taken Week Ending 11/12/22

*Extent of excavation at end of week. Wide shot looking ENE. Pine Terrace on right.*

*This shot gives you some idea of the power of these machines.*

*Photo by John Sedlak shows contractor separating materials for recycling.*

*While two machines tear down building, a third separates material and loads it into dump trucks.*

*Demolition happens much faster than construction. What took months to build will come down in days.*

*KMS demolition in full swing. Reverse shot looking S toward Pine terrace.*

*The temporary detention pond did its job Friday afternoon and evening. It held almost 2 inches of rain.*

*All was quiet Saturday morning. Here you can see steel being separated from the debris for recycling.*

*Sunset by John Sedlak on 11/5/22 shows the gorgeous new KMS on the right. The old KMS on the left will soon become athletic fields and a larger detention pond to reduce flood risk for neighbors.*

To see the history of this project (both construction of the new KMS and old KMS demolition), see the posts below:

Posted by Bob Rehak on 11/12/22

1901 Days since Hurricane Harvey

66% Impervious Cover? Really?

Because the Laurel Springs RV Resort was grandfathered under old drainage regulations, it got away with building a detention pond that was half the size required by current regulations.

But assuming the developers were just shrewd businessmen who legally and successfully exploited the system, did they follow the rest of the rules? Let’s look at two other things.

The percentage of impervious cover on the site
How the number of parking spots increased 25% without the impervious cover increasing.

*Laurel Springs RV Resort as of 10/22/22*. The contractor still has one more “pour” to complete the concrete in the far upper right of the image.

Were Impervious Cover Calculations Correct?

Detention-pond volume calculations begin with impervious cover (i.e., land covered by concrete plus the entire detention pond area). See below.

66% impervious cover — *Laurel Springs RV Resort Detention Pond calculations from approved permit plans.*

The total site covers 20.032 acres. The proposed impervious portion, they claim, covers 13.349 acres. That works out to 66.6%. So one third of the site should be grass, trees and other vegetation. But since the entire 5-acre detention pond counts as impervious, mathematically, the remainder of the site can have no more than about 60% concrete and still comply with the percentage they promised.

But just eyeballing that trapezoidal area in the photo above, it seems much more than 60% is covered with concrete.

If my eyeball assessment is correct, then the detention pond is even more undersized than I initially thought because the percentage of impervious cover has increased and with it the amount of runoff.

I wish the developer would show us the basis for those calculations.

Plans Show Increase in Density With No Increase In Impervious Cover

The developer’s permit allows 182 RV spaces, but the plans show 226 – about a 24% increase. However, the impervious cover shown on the plans before and after the permit approval did not change. That could also affect detention pond capacity requirements. And explain why the percentage of concrete appears higher than they claim.

Why Underestimate Impervious Cover?

Why would a developer underestimate the amount of impervious cover? Two reasons:

It would make the detention pond smaller and thus allow the remaining property to produce more income.
By claiming they’re providing more detention than required, they can get a discount on their drainage fees. See page 10.

I’m not alleging they did anything illegal. I’m just saying that much more than 60% of that trapezoid in the photo above appears to be concrete and I sure would like to see how they arrived at their figures. I requested the drainage analysis twice and never got it. That should tell you something.

Posted by Bob Rehak on 10/23/22

1881 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.

Half of Preserve at Woodridge Already Framed Out.

Less than six months ago, Guefen started clearing land for the Preserve at Woodridge. Plans showed that the Preserve would contain 131 Lilliputian-sized homes for rent, some as large as 668 square feet. Already, more than half the homes are framed out. And one fifth have roofs. I counted 73 homes either completely or mostly framed in the photos below.

Photos Taken April 30

Here are some pictures taken of the Preserve at Woodridge last week.

*According to plans, the vertical wall behind the homesites will be a retaining wall. In the pond itself, contractors are to install a 2-foot thick clay liner in 8″ lifts, each compacted to 95%.*

As of last Saturday, *contractors were still pumping silty stormwater* *into this channel which empties into Bens Branch at Northpark Drive.*

*Looking SW across 17 acre site toward Northpark Drive and St. Martha Catholic Church.*

*Not much grass will grow between these homes.* *It will be in shade most of the day.*

*Looking east from over Woodridge Parkway toward Kingwood Park High School and KSA’s Northpark Recreation area.*

The developer claimed 65% impervious cover. But work to date appears much denser.

Preserve at Woodridge Detention Pond Progress Much Slower

If only the pace of work on the detention pond went as fast! Instead, contractors have treated it like an afterthought. They still haven’t come close to finishing it. And grass lining? Plans don’t mention it as far as I can see.

To see the complete plans, click here. You can find the detention basin plans and calculations on pages 18-24.

It’s not clear whether the detention pond will have a grass liner to reduce erosion or simply a compacted clay liner.

The construction plans call for compacted clay. And a search for the word “grass” did not turn up any mentions in the construction docs.

MoCo Drainage Regs Murky on Grass Lining of Detention Ponds

Montgomery County Drainage regulations get murky on whether detention ponds must have a grass lining.

“7.2.7 Erosion Control Measures for Detention Facilities” on Page 113 says:

“The erosion potential for a detention basin is similar to that of an open channel. For this reason the same types of erosion protection are necessary, including the use of backslope swales and drainage systems (as outlined in SECTION 6), proper revegetation, and pond surface lining where necessary.”

The wording in 7.2.7 leaves room for interpretation. It’s not clear whether engineers must specify all or one of the alternatives listed.

So I checked Section 6, which pertains to CHANNEL construction. “6.2.1 Grass Establishment” on Page 85 says:

“A good grass cover must be established on all areas within the right-of-way (except the channel bottom) disturbed by channel improvements or by any type of construction. An adequate grass stand on the banks helps stabilize the channel and minimizes erosion caused by overbank flow and high velocities in the channel.”

There’s certainly a lot of ambiguity in these specifications. Montgomery County has not yet responded to a complaint about the pumping of the silty stormwater down Ben’s Branch. And the only plans the engineering department supplied are those linked above.

Best Practices Vs. Industry Standard Vs. Minimum Requirements

A source knowledgeable about construction reminded me of the tremendous difference that exists between Best Practices, Industry Standards, and Minimum Requirements. Few companies will follow best practices if it costs them money, said the source. Even industry standard practices are optional. Most just follow the minimum requirements.

And even if the engineering plans comply with those requirements, there’s no guarantee contractors will follow the plans.

So understand your local regs. And report corner cutting when you see it.

*Best practices call for detention ponds to be among the first things finished on a construction site. MoCo doesn’t mandate that, however. Grass would certainly help reduce erosion here.*

Posted by Bob Rehak on 5/4/2022

710 Days after 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.

Silty Detention Pond Flushed into Bens Branch

Contractors at the controversial mini rent home development called the Preserve at Woodridge Forest flushed a silt-laden detention pond into a stormwater channel leading to Bens Branch this week. The silty water migrated at least two miles downstream. The pictures below show the trail of silt.

On 4/17/22, Easter Sunday, I photographed a full pond and noticed a pump in the upper right (southeast) corner of the pond.

*Looking east over Preserve at Woodridge Forest detention pond on Easter Sunday. Note pump in upper right* *and pond level.*

Three days later, the pump was still going and the pond was nearly empty.

The ditch between the Preserve and Kingwood Park High School was filled with identically colored water.

*Color of water in ditch matches color of water in pond. Note pile of silt in ditch below pump hose in lower left.*

*Looking north past pump and the near-empty detention pond.*

*Equipment apparently cleared paths for northern end of pond to drain toward pump.*

Where did all the silty water go?

*One block downstream,* *Bens Branch at Woodland Hills Drive.*

*Bens Branch at Tree Lane* *approximately 2 miles south of construction site.* *Resident Chris Bloch followed the pollution even farther downstream.*

Fish Story

As I photographed the silty water above going down Bens Branch, two young boys with fishing poles came up to me. They looked at the water in disbelief and then looked at me quizzically. “Do you think it’s safe?” they asked.

“Hard to tell,” I said. “It’s runoff from a construction site upstream.”

They left without even dropping a hook into the water or saying a word. Smart kids.

Dangers of Sediment Pollution

The EPA published this brochure that explains some of the dangers of sediment pollution. Among them, it says, “Sediment in stream beds disrupts the natural food chain by destroying the habitat where the smallest stream organisms live and causing massive declines in fish populations. Sediment increases the cost of treating drinking water and can result in odor and taste problems.” Bens Branch empties straight into Lake Houston, the source of drinking water for 2 million people.

Sediment can also clog streams, reducing their carrying capacity. Harris County Flood Control recently cleaned out Bens Branch in a 4-phase project. According to the Kingwood Area Drainage analysis, it had been reduced to a 2-year level of service in places. That means it would flood on a 2-year rain.

No Permit Posted

For these reasons, the Texas Commission on Environmental Quality closely monitors construction sites. But the Preserve at Woodridge did not have a TCEQ Construction General Permit posted at the street. This web page seems to indicate they should have one. See Step 5. It says, “Before starting construction, post a copy of the Site Notice at the construction site. Leave the notice posted until construction is completed.”

Posted by Bob Rehak on 4/23/22, with thanks to Chris Bloch for alerting me to the story

1698 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.

Laurel Springs RV Resort Turns Into Giant Mud Bath

After a 2 inch rain on 3/22/22, the construction site at the Laurel Springs RV Resort turned into a giant mud bath, now being pumped into the Lakewood Cove storm sewer system. The whole point of the Stormwater Pollution Prevention Plan approved by the TCEQ is to prevent that.

Is This Part of A Bigger Marketing Plan?

Large ponds of muddy water covered the site from north to south and east to west, a tribute to the drainage still not installed after five months of site work. It makes one wonder whether the contractor’s tardiness is part of a marketing ploy.

Do they plan to market this RV resort as a mud bath/spa? Will they offer a special pit for ladies’ mud wrestling on WWF nights? Do they plan to turn part of the site into an all-weather ATV track? Will they rent this place out to kindergarten class reunions? Or will this be a practice range for politicians who want to learn how to sling mud? There’s just no telling. The secretive owners still have not divulged their marketing plans with the local residents.

Pictures Taken After 2″ Rain

Regardless, they have conspired with Mother Nature to create a world-class mud bath, as the pictures below show. I took the pictures below the morning after the gage at the West Fork and 59 recorded a two-inch rain.

*Looking north toward entrance on right.*

*Let’s bring in some more mud. Note dirt piles at top of frame.*

*There’s nothing like mud to slow down work on a construction site. That’s why this must be intentional. Ooops. What happened to those silt fences on the west?*

*The creative approach to construction.*

*Even though they’ve installed a drain, they still haven’t installed pumps.*

They started pumping this pond into the Lakewood Cove storm sewer system today. So much for keeping mud out of the sewers. That’s a major part of the Stormwater Pollution Prevention Plan approved by the TCEQ.

Posted by Bob Rehak on 3/23/2022

1667 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.

RV Resort Getting Ready to Pour Concrete, Baffling Activity at Detention Pond

Construction activity at the Laurel Springs RV Resort near Lakewood Cove kicked into overdrive today as workers laid forms to prepare for concrete and more pipes went into the ground. Also, the detention pond seemed to change shape in ways that could reduce its capacity.

Getting Ready for Concrete

The shot below shows what will become the main entrance/exit opposite Mystic Glen Loop in Lakewood Cove.

*Entrance/Exit to RV Resort. Concrete building pad for recreation center. The two rectangular areas in front of the three cargo containers will be the first RV pads. Blue pipes will carry fresh water*.

*Plans that correspond to the photo above.*

*Concrete forms also extend south toward the detention pond*, *out of sight at bottom of frame.*

Baffling Work at Detention Pond

The work at the detention pond today was hard to explain. For the last few days, workers have pulled dirt and tree debris up onto the southwestern wall of the detention pond. Here’s how it looked yesterday around noon.

*SW wall of RV Resort detention pond photographed on 2/17/2022.*

Trucks have moved a portion of it to the western wall.

*Looking east. Excavator loading debris onto truck which will back it around to the western wall (out of frame to the lower left). This and all photos below taken 2/18/22.*

*Truck transplanting debris on western wall.*

The wide shot below shows where they have been piling it on the western wall and puts the activity in context.

*Looking South toward Edgewater Park in background.*

*But it wasn’t all going to the western wall. Bulldozers spread some into the Laurel Springs RV Resort detention pond.*

*The area where contractors laid pipe between the pond (left) and ponding water (right).*

*Meanwhile, another bulldozer seemed to push dirt from the outside of the pond’s southern wall to the inside.*

*It appeared as though contractors were attempting to shift the entire wall to the north. If accurate, that could reduce the pond’s already constrained capacity.*

Did the developer’s surveyors make a mistake initially? We shall know soon enough if the County conducts its own survey.

*If that tree debris gets plowed into the pond wall, it could weaken the structural integrity of the pond as the woody material decays.*

Reducing Pond Capacity?

I’m especially concerned about the potential loss of capacity in the detention pond. It already had only half the current capacity required to meet current City of Houston standards.

The further along construction gets, the harder it is to undo mistakes if they happen. So we need to monitor this closely.

Posted by Bob Rehak on 2/18/22

1634 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.

Photos of Kingwood’s First RV Resort after Heavy Rains Last Weekend

One thing became immediately clear after reviewing aerial photos of the Kingwood area’s first RV resort last Monday. The heavy rains created a mud pit. After removing every tree and blade of grass on these 20 acres, the owners of this project will have to pave over virtually the entire site to make it useable.

I took all photos below on Sunday morning 1/9/22 after heavy rains stopped, but between sporadic light rains.

Laurel Springs RV Resort after Heavy Weekend Rains

*Looking NW from over Laurel Springs Lane at Kingwood’s first RV resort and its detention pond after a 5.5 inch rain.*

*Silt seems to be piling up along silt fence on right, an indication of how site is sloped.*

*Contractors are starting to build roads. But look at ponding on either side of first one.*

*Looking SSE across RV resort from over UP railroad tracks at Lakewood Cove.*

*Rains can delay construction by making it difficult to work the ground.*

*Note drainage running down Centerpoint utility corridor.*

*Note heavy erosion and debris in detention pond.*

*Currently lip of detention pond is below road level. Overflow from pond will likely go into Edgewater Park’s cypress ponds below hill.*

Bad News, Good News

Most of the initial fears that Lakewood Cove residents had about this site remain valid. Railroad noise. Traffic safety. Road destruction. School impact. And more.

However, after seeing the response of the site to last weekend’s heavy rains, I’m less concerned about the site flooding Lakewood Cove if the southern lip of the detention pond remains at its current height.

Presently, the pond lip is much lower than the road as you can see in the photo above. If it stays that way, overflow stormwater will go down the hill west of Laurel Springs into what will soon become Precinct 4’s new Edgewater Park.

It’s important to keep in mind that last weekend’s storm was a 2- to 5-year storm, according to Jeff Lindner, Harris County’s meteorologist. So this wasn’t a very big test of the resort’s drainage systems. A hundred year storm would drop three times the rainfall.

The pond currently has half the required capacity to meet current rainfall standards. Still, last weekend was significant. Kingwood was among the hardest hit areas in Harris County.

However, there’s also a significant amount of dirt piled on the northern lip of the pond. It’s unclear where contractors will put that. If they use it to build up the southern lip, that could change the game.

Clearly, the owners lucked out with the timing of this storm. They substantially completed the detention pond before the storm. Otherwise, this could have turned into another Woodridge Village/Elm Grove situation.

Posted by Bob Rehak on 1/14/2022

1599 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.

Kingwood Middle School: November Construction Update

Construction of the new Kingwood Middle School appears on schedule for opening with the next school year in 2022. Compared to my October update, no new major milestones have been reached. Everything just looks a little further along.

Kingwood Middle School Construction Sequencing

Construction started on the west and is moving toward the east. As subcontractors finish one phase such as foundations or structural , the next group picks up the baton and works on roofing, exterior walls, windows, etc.

The most visible change between October and November: progress on exterior walls and roofing.

I took all the pictures below on Saturday, November 6, 2021.

*Looking W.* Judging from the amount of erosion around the banks, the temporary detention pond appears to be getting a lot of use. This pond will be replaced with a larger permanent one after the old school is demolished to make room for it.

*Insulation, vapor barriers, brick and glass now surround more than half the site now. Roofing on the westernmost section looks complete. But many roofing materials remain stacked on other sections.*

*Looking south with the old school visible in the top of the frame.*

*Masons have completed the brickwork on large portions of the westernmost section. Shot taken from over Woodland Hills, looking east.*

*Portions of the exterior at the west end still need work, but it’s more done than not.*

*A view from the SE looking NW clearly shows the degree of finish evident in the left, middle and right sections.*

*Low level shot shows middle section on left.*

Next Steps for KMS

Next steps will be to dry-in the structure by completing the exterior walls, windows and roofs. The other trades will then start working on interior walls, electrical, wallboard, paint and flooring – all the things that could be destroyed by blowing rain.

I put two kids through the old Kingwood Middle School who became happy, healthy, successful adults. As I look at these pictures, fond memories of plays, recitals, teacher conferences, and athletic contests come to mind. Each month, as the old school comes closer to demolition, I become increasing nostalgic. We will soon witness the end of one era and the start of another in Kingwood.

Architectural renderings on the Humble ISD site inspire confidence that the next generation of Kingwood Middle School students will have an even better learning environment than the last.

And cross your fingers! Despite double the impervious cover now on the site, I have received no reports of flooding from neighbors.

Posted by Bob Rehak on 11/11/2021

1535 Days since Hurricane Harvey

Another Massive Detention Pond Going In Next to Halls Bayou

Construction has begun on another massive detention pond along Halls Bayou. It stretches south from Isom Street to the bayou between Chrisman and Aldine-Westfield Roads. It covers approximately 26 acres and when complete will hold 180-acre feet of stormwater to reduce the risk of flooding. This is just one of 11 projects comprising the Halls Implementation Program. Together they have a total current value of $212 million dollars.

*Looking NNW across the new detention pond. Construction started in August 2021. HCFCD expects completion by March 2022.*

Such basins take in excess stormwater during heavy rain events and then release it slowly back to the channel when the threat of flooding has passed. Part of the basin will have a wet bottom and another part will have a vegetated shelf. Yet another part will go in between Isom and Aldine Mail Route Road, although that portion has not yet begun construction. (See below).

*Map on left shows current extent of construction work. Eventually, project will also include channel conveyance improvements (right) for a tributary that will be directed into the new pond.*

Harris County Flood Control District (HCFCD) lists the project as C-25 on its website. But the Flood Bond Program ID is P518-11-00. Ultimately, this will become part of a much larger project area that includes P118-21-00. Together, they will improve drainage in a large part of east Aldine.

Each of these projects falls into Commissioner Adrian Garcia’s Precinct 2. The description that accompanies the project in the flood-bond spreadsheet says, “This project could reduce the risk of flooding for over 90 buildings and could reduce the 1% floodplain for over 100 acres.” The HCFCD spreadsheet and website indicate a total cost of more than $14 million.

But keep this in mind. Project C-25 will work in conjunction with two proposed Harris County Engineering Department projects: neighborhood drainage improvements in the Western Homes subdivision and proposed roadway and drainage improvements along Aldine Mail Route Road. The detention capacity in the pond you see here will accommodate drainage improvements in those areas without flooding other areas. Thus, the pond will really help more than 90 structures.

*The project shown in these photos is P-518. P-118 is still in preliminary engineering review.*

C-25 is a partnership project. HCFCD received an approximately $9.5 million Community Development Block Grant for Disaster Recovery (CDBG-DR) from the US Department of Housing and Urban Development (HUD). Approximately $5.4 million comes from local funding.