sediment-laden runoff Archives

1/27/25 – The Humble ISD contractor in charge of rebuilding Foster Elementary has taken multiple, positive steps to reduce sediment-laden runoff from the construction site. Neighbors complained in early January about silty runoff from the site.

Chris Parker and Robert Scarfo, two members of the school board, contacted me and facilitated a meeting with contractors and ISD construction supervisors at the site. The meeting was unusual in that the six people present all seemed eager to eliminate the problem, not just convince me that I shouldn’t worry about it.

We spent the next 90 minutes discussing preventive measures they had implemented.

Final Phase of Construction Had Just Started

As it turns out, the project had just recently entered the third phase of the reconstruction effort.

Demolition and utilities/permitting precede new construction. So, the contractors had not yet fully installed all measures designed to prevent sediment-laden runoff when the early January storm struck. However, between the initial incident and the time we met on 1/24/25, they had made considerable progress.

I went back today after a 2″ rain yesterday. I can’t say there was no runoff. But the water left standing in the street was the clearest I have ever seen around a construction site. The turnaround was dramatic.

Multiple Lines of Defense

Measures designed to prevent sediment-laden runoff included:

Three stormwater detention basins, two of which they will later connect into a larger basin
Silt fences around the entire site
Secondary fences to keep people back from the sharp stakes that anchor the silt fences
A novel form of storm-drain-inlet-protection (see pics below)
Wattle rolls (tubular barriers filled with straw) wherever perimeter top soil had been disturbed
Gravel at construction site entrances to knock mud off the tires of trucks leaving the site
A full-time employee dedicated to scraping mud off surrounding streets and sweeping them clean

More on the Way

In addition, they have ordered “track-out matts” to help knock mud off the tires of trucks. The matts replace gravel traditionally used at entrances. However, gravel must constantly be replenished as it gets pushed down into the dirt.

The surface of the new matts features a grid of pyramid-shaped bumps that minimize the amount of mud tracked out of job sites by construction vehicles. They also protect keep gravel from becoming embedded in tires

As an environmental bonus, the HDPE mats are re-usable for up to 10 years.

Pictures of BMPs Now in Place

I took the pictures below on Friday, 1/24/25, and Monday, 1/27/25. On Sunday and Monday morning, we received approximately 2″ of rain.

The old Foster Elementary school had no stormwater detention basins. The new Foster will have two when finished. The construction road separating the two on the left will be removed at the end of construction to connect the two halves.

*Temporary channels lead runoff into the detention ponds for now until the permanent drainage is installed.*

*Note the filtration in front of the pipe leading from one of the ponds to the storm sewer.*

*Note gravel at the construction entrance in the upper right.*

*On Friday, a fresh load of gravel had just arrived for another entrance.*

The black silt fence is semi-porous. It lets water through, but holds sediment back. The bottom is buried to keep water from rushing under it. Note sharp ends on stakes supporting the silt fence. The outer blue fence protects pedestrians from those stakes *and other job site dangers.*

scraper — *Contractor has one employee dedicated to scraping and sweeping up dirt full time.*

*A wattle roll helps protect the sidewalk from erosion in the disturbed area.*

*Multiple layers of protection: 1) silt fence behind blue fence, 2) a wattle roll, and 3) inlet protection (see more below).*

*A wire cage snaps into the storm drain inlet. Porous fabric lets water enter the drain, but traps dirt, leaves and other street debris.* *This is an alternative to the sandbags placed beside inlets at many construction sites. This system does not force water out into the street like the sandbags do.*

Surrounding Streets Looked Much Better Today

Several of the construction managers for the contractor live in Kingwood and helped rescue people during Harvey. After spending 90 minutes with them, I believe they want to avoid a repeat as much as other residents. They fully understand the importance of reducing sediment-laden runoff and seem to do a much better job than competition.

Shortly after the rain ended this morning and before the contractors arrived, I took the two shots below. They show the impact of following best management practices.

*Cystal Springs Drive south of Foster reconstruction site. Note the absence of sediment buildup near the curb.*

*Water near the curb was as clear as any I have seen next to a construction site, thanks to all the measures above.*

Construction experts say we can’t always expect runoff to be this clear. It may contain particles of clay so fine that they migrate through silt fences. But particles that small usually remain suspended and float out into the Gulf without blocking drainage.

However, we do need to prevent larger particles from settling out of suspension in gutters and storm drains, and accumulating into layers of muck.

I plan to revisit this site periodically throughout the construction to monitor progress.

The new building will have enough capacity for 800 students. The artists renderings look beautiful. The Humble ISD says the facility should open for the 2026-2027 school year. I can’t wait to see it.

Posted by Bob Rehak on 1/27/2025

2708 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.

12/29/24 – Several rounds of intense rain in the past week triggered a slew of emails from concerned residents about the need for better construction management practices to control sediment-laden runoff.

Chris Summers, a retired commercial photographer, included pictures of the runoff from the Foster Elementary site in Kingwood’s Trailwood Village. Contractors recently cleared the site for reconstruction of the school. Summer’s photos illustrate the dangers from sediment pollution and the need for better construction management practices.

A Major Source of Sediment Pollution

Construction site runoff is a major source of sediment pollution. Construction typically involves large-scale disturbance of soil, which can significantly increase the amount of sediment carried away by stormwater runoff. This sediment-laden runoff can have serious environmental impacts, especially when it enters local water bodies, such as Lake Houston..

Clearing, excavating and grading disturb soil. Stripping away vegetation makes soil more prone to erosion. So, when it rains, the exposed soil can easily wash away into nearby water systems.

In many cases, vegetation or other stabilization measures (e.g., erosion control blankets, mulching) may not be installed until later stages of construction, leaving the site vulnerable to sediment loss in the meantime.

Construction sites are most vulnerable during heavy rainfalls, which can lead to significant runoff, especially from areas without adequate sediment-control measures.

In many cases, construction schedules are not aligned with seasonal weather patterns, so sites may be left exposed during periods of heavy rain. This can lead to water-quality degradation, increased costs for water treatment, higher water bills, and infrastructure damage.

Excessive sediment can clog stormwater systems, leading to flooding and costly repairs.

Regulations and Best Management Practices

Due to the significant environmental impact of construction-site runoff, many countries and regions have strict regulations and Best Management Practices (BMPs) to control it. In the U.S., for example, the Clean Water Act requires construction sites to control stormwater discharges through permits such as the National Pollutant Discharge Elimination System (NPDES) permit. This often includes implementing sediment control measures like silt fences, sediment basins, and erosion control methods.

Rainfall and Soil Saturation in Last Week

The HCFCD gage at West Lake Houston Parkway and the San Jacinto West Fork shows that the area near Foster Elementary received about 2 inches of rain in the last few days.

That made the soil go from “wet” to “saturated.”

And that radically increased runoff.

Photos of Foster Elementary Construction Site After Heavy Rains

Summers’ photos show the need for better construction management practices to control sediment-laden runoff.

Silty water streamed out of the site after an intense rain.

The flow was steady and strong.

Water exited the site in multiple places and filled half the street.

Inlets had no protection. (See #8 below).

The site had large areas of disturbed and unprotected soil.

Runoff left inches of soil in the street. Imagine what the storm sewer looked like…

…especially since storm-sewer inlets were unprotected by any of the usual methods. (Again, see #8 below.)

Ways to Reduce Sediment-Laden Runoff

Here are several common and effective methods used to minimize silt-laden runoff. They represent best construction management practices.

1. Silt Fencing intercepts and slows down water flow, allowing sediment to settle before water flows off the construction site. It’s normally installed around the perimeter.

2. Sediment Basins & Traps capture sediment from runoff until it settles out of suspension.

3. Erosion Control Mats or Blankets stabilize disturbed soil and prevent erosion. They are most often used during the early stages of construction.

4. Mulching with organic materials – such as straw, hay, or wood chips – helps to protect soil while promoting vegetation growth. They are most effective when applied immediately after soil is disturbed.

5. Planting Vegetative Cover, such as fast-growing grass, can also help stabilize soil and reduce runoff. Plant roots bind the soil, making it less susceptible to erosion. Vegetation also slows down the flow of water, reducing the energy available to carry away sediment.

6. Sediment Control Logs (Wattles) are tubular barriers filled with straw or other materials. When placed along the contours of the construction site, they capture sediment before it leaves the site.

7. Stormwater Diversion Channels direct runoff to sediment-control ponds or a controlled discharge areas.

8. Stormwater-Inlet Protection, such as sandbags, can be placed around stormwater inlets to capture sediment before it enters the storm drainage system.

9. Shallow temporary or Permanent Vegetative Swales collect runoff and allow it to slowly infiltrate into the soil while trapping sediment in the vegetation and soil.

10. Construction Entrance/Exit Stabilization with gravel minimizes the tracking of mud onto roads from construction vehicles. But the gravel must be regularly maintained.

11. Grading can help control water flow and minimize erosion by directing water flow away from disturbed areas towards sediment control features.

12. Geotextiles can also provide erosion control and soil stabilization.

Need for Regular Inspections

Regular inspections and maintenance ensure that all erosion and sediment control measures are installed functioning properly.

Compare the measures in this list to the photos above. With the exception of gravel at the entrance, Summers’ photos show that few of these measures appeared to be implemented at the Foster construction site.

Posted by Bob Rehak on 12/29/24 with photos by Chris Summers

2679 Days since Hurricane Harvey

Tag Archive for: sediment-laden runoff

Humble ISD Contractor Reduces Sediment-Laden Runoff