Sheetflow Construction Erosion and Sediment Control

November 6, 2019

Sometimes There’s Just Too Much Rain

Filed under: Photo — Tags: , , , , , , , — Sheetflow @ 1:08 pm
November 6, 2006 Sea-Tac, Washington Photo: David Jenkins

We were building a new runway, had several hundred acres of open ground, when the big rains came. We were using the stormwater ponds to collect all of the water for a 10 year 24 hour storm event, or 3 inches of rain. All of the water in the ponds was being treated with chitosan-enhanced sand filtration systems before discharge.

The storm of November 6, 2006 was something over the 50 year 24 hour event and something under the 100 year 24 hour event. With the rainfall and the pond over topping, water was discovered draining from the base of the pond. Rock and ecoblocks were placed as an emergency fix to keep the pond from a catastrophic failure. All of the dirty water drained to a creek, but, nothing we could do.

October 31, 2019

Is This Silt Fence Necessary?

Filed under: Photo — Tags: , , , , , , , , , — Sheetflow @ 1:24 am
Perimeter Silt Fence Photo: David Jenkins

Overlooking the fact that this silt fence installation needs some maintenance, I wonder if it was ever really needed in this location? The slope grades to the fence are minimal and not very long, and the roadside ditch line is graded so that water will drain away from the road.

This type of silt fence installation is appropriate at the base of long, steep slopes, or if there is risk of sediment travelling off site. Also, all of the materials used will likely be land filled and not reused, including the wire backing and the “T” posts.

If this were my site, I would have installed orange safety fence with steel “T” posts, maybe with a compost berm along the base, on the project side. The safety fence can be easily removed and reused later, and the compost could be raked into the ditch line and hydroseeded.

October 30, 2019

Open Catch Basin Fixed Again

Filed under: Photo — Tags: , , , , , — Sheetflow @ 4:59 am
Back where we started, 30 mil PVC blocking the catch basin. Photo: David Jenkins

As of two days ago, there is new 30 mil PVC under the catch basin grate and turbid water is not draining into the catch basin. The contractor told their staff not to puncture the PVC. No word on whether they are thinking more proactively about this. The best measure is to keep the stockpile covered and the area cleaned up. We shall see what’s next.

October 29, 2019

Open Catch Basin Open Again

Filed under: Photo — Tags: , , , , , , — Sheetflow @ 4:55 am
Why, this was flooded yesterday, what happened? Photo: David Jenkins

The saga continues… the next inspection looked like the first inspection. 500 + NTU water draining into the catch basin. What happened?

30 mil PVC punctured to let water drain. Photo: David Jenkins

As suspected, someone didn’t like the flooding, so they punctured the 30 mil PVC. I am wondering why the contractor erosion control lead is not finding this.

October 28, 2019

Open Catch Basin Fixed?

Filed under: Photo — Tags: , , , , , , — Sheetflow @ 4:55 am
Catch Basin Blocked with 30 mil PVC Photo: David Jenkins

I inspected the open catch basin the next day, and this is what the contractor had done to keep turbid water out. I have nothing against doing this, but, since this does keep water out, flooding ensues. Flooding is okay if the catch basin is in a low spot and no one needs to work in the area.

I told the contractor that they might want to look at the storm system and see if there is a point where they can install a concrete plug temporarily and use the system for conveying the turbid water to their treatment system.

October 27, 2019

Open Catch Basin

Filed under: Photo — Tags: , , , , — Sheetflow @ 6:56 pm

I found this open catch basin during a construction erosion inspection. The turbidity of the water draining into it from the stockpile measured at over 600 NTUs. Note that there is an insert in the catch basin; these do nothing to reduce turbidity. I notified the contractor who should have found this in their daily inspections, which I pointed out to them.

October 26, 2019

Rain in the Forecast

Filed under: Photo — Tags: , , , , — Sheetflow @ 1:16 am
Yelm, Washington. Photo: David Jenkins

October 23, 2019

Concrete Pour

Filed under: Photo — Tags: , , , — Sheetflow @ 1:22 am
Always fun to watch someone else working. Photo: David Jenkins

Here we are constructing a large stormwater pond. To keep vegetation from growing and attracting birds (dangerous to aircraft) the bottom is covered with concrete, the sides will be covered with heavy plastic liner, and the whole thing will be covered with a net. Frequently, on large concrete pours, we specify that there be no truck washout on site, both to speed things up and to avoid concrete mess everywhere.

October 21, 2019

“Means and Methods” vs. Best Management Practices

Demolition of landside crane rail on a shipping container terminal.

In my experience, managing contractor “means and methods” is more important than using the “right” best management practices. When turbidity is the standard for measuring water quality compliance, as in Washington state, site cleanliness is the key to prevention and compliance.

This contract requires that catch basin inserts be installed in all catch basins within the project boundaries. However, inserts are not at all effective in reducing turbidity in runoff. While removing the crane rail on this container terminal project, the contractor could clean up as the work progresses, place all material removed from the trench onto plastic for later removal, load into a Bobcat bucket, and pick up small debris with a shop vac. I can require these things in the contract that the contractor bids. It may cost extra; the extra cost may be worth it if it reduces my risk. If I tell the contractor after the contract is awarded, I will pay more.

I can also make suggestions during the work, pointing out that keeping things really clean will keep them in compliance with their NPDES permit. If framed in a way that shows benefit to the contractor, meaning reducing risk and cost, they will probably follow the suggestion.

October 18, 2019

Highway 93 Storm

Filed under: Photo — Tags: , , , , , — Sheetflow @ 1:10 am
Somewhere in Nevada. Photo: David Jenkins
Older Posts »

Powered by WordPress