Sheet Flow Construction Erosion Control

November 6, 2020

Blowin’ in the Wind

Filed under: Photo — Tags: , , , , , , — Sheetflow @ 4:04 am
Photo: David Jenkins-Sheetflow Erosion Control

Blowin’ in the wind is what happens to your plastic stockpile cover when you don’t use enough sand bags. The contractor has been pulling material from the pile daily and hasn’t been using enough sand bags on the overlapped seams.

October 13, 2020

Plastic Covered Slope

Here is a nice, plastic covered slope. They have placed sand bags on the seams, the seams are overlapped at least 12 inches and the plastic is run all the way to the bottom of the slope. This is a riverbank habitat restoration project on the Duwamish Waterway.

Video: David Jenkins

September 30, 2020

Slope Covered with Plastic

View of slope on Site 25 Habitat Restoration Project. Photo: David jenkins

We have covered a slope above the Duwamish Waterway with plastic until landscaping occurs in December. The contractor has done a great job overlapping the plastic sheets and securing them with sand bags.

April 6, 2020

Silt Fence and Trackout Fail

Photo: David Jenkins

I was just minding my own business last Friday, driving from Fred Meyer to the UPS store and passed this project. I told my wife I have to get a photo; she says okay since she knows me and my habit of stopping to take TESC photos.

I made a u -turn at the Wal Mart, drove back a block and stopped in the middle of the street to get this shot.

There is so much wrong here, where do I start? Clearly, dirt is tracked off of the project in the background, as you can see the sediment build up in the curb line. Someone told someone to put something in the swale to keep dirt out, then someone else installed this silt fence.

First off, silt fence needs to be trenched in and this just has a few rocks placed on the flap.

Second, they probably couldn’t trench this in anyway without tearing up the drainage swale.

Third, only two of the three curb cuts are backed by the silt fence.

Fourth, silt fence is a barrier, not a filter, and with the volume of water draining off the asphalt during a rain event, dirty water would just blow around and under the silt fence.

Conclusion, silt fence is never used in a water flow situation; it is only to contain eroded sediment from a sloped area. A better BMP here is a compost berm or something similar that would allow some water to pass but filter some sediment. Sand bags would work to keep everything out of the swale but then the dirty water would bypass to the next catch basin, which probably has a catch basin insert, which would collect sand and such but would not do anything for turbidity. So, what is the best BMP? Stop the !@#$ ing trackout in the first place!

March 30, 2020

Before and After

Photo: David Jenkins
Photo: David Jenkins

The contractor had to connect a new storm system from up the hill into an existing catch basin in the foreground. After they completed the connection but before paving, they covered the pipe run with plastic and sand bags to protect from dirty water entering the catch basin. Work was completed during dry summer weather. Paving took place a couple of months later.

September 17, 2019

Can’t Get Away From It

I can’t get away from it. It doesn’t matter where I go, I always see some type of construction erosion issue. I went to visit relatives in Portland, Maine, flying in and out of Boston Logan International. In the terminal, waiting for my flight back home, I saw a construction project on the ramp; it had rained a few says before, hard. Obviously, the stockpile had not been covered before the storm and sediment washed off the pile into the drain.

I work at an airport that operates under strict turbidity effluent limits; here is how we do this kind of work:

(1) rarely do we allow stockpiles on the ramp because we rarely reuse the excavated material (it is either contaminated, unsuitable or doesn’t meet current FAA requirements); it is direct loaded into trucks and hauled off. When we do stockpile, we place dirt on plastic and cover it with plastic, using lots of sand bags to secure it from jet blast and wind.

(2) work areas are always isolated so there is no runoff from the site. Normally, we use four-inch extruded asphalt curbing along the base of the jersey barriers. Rolled hot mix asphalt (HMA) is used at the entrance point so water is contained but vehicles can access the site.  Water that builds up inside the curbing is pumped back into the excavation if clean, or a tank if contaminated.

I should have mentioned that we also have strict sediment trackout requirements: no visible sediment leaves the site at any time.  This is both because of the effluent limits and for safety reasons; dirt and debris that gets sucked up into a jet engine is damaging and possibly deadly.

Lastly, I am not casting aspersions on the folks at Logan; I don’t know their situation, permits, drainage system, or tolerance for risk.  Because of my situation, I have low risk tolerance for potential non-compliance with our permit and I notice when something would cause me grief at my airport.

October 21, 2018

Creek Diversion for Restoration Work

This shows step by step instructions for a creek diversion when working in a salmon-bearing stream including:

setting up fish screens,

electroshocking fish,

diversion pumping,

and sand bag dams.

 

Video: David Jenkins

July 3, 2018

Barrier and Asphalt Berm

Barrier and Asphalt Berm – The more clean water you keep from flowing into your job site, the less dirty water you will have to manage. Placing a berm along the base of “Jersey Barrier” is one way to accomplish this.

Materials you can use include cold patch, extruded asphalt curbing, or sand bags.

Video: David Jenkins

July 7, 2016

Water Flow Over Slope Causes Erosion

Inspecting a project during a rainstorm is sometimes the best way to determine how storm water will flow around the site. It was clear, during this inspection, that the flat area above the slope was graded toward the slope face , which allowed water to flow over and down the slope, causing it to erode. If it was not possible to grade the area above away from the slope, a sand bag berm and a pipe slope drain could have been used to collect the water and convey it to the base of the slope.

 

Video: David Jenkins

May 17, 2016

Inspecting-Check Dams Need Low Center Point

Check dams need to be installed with a low center point.  This means  that the center of the dam is at least 6 to 8 inches lower than the outside edge; 12 inches in areas where intense rainfall occurs. If the center is higher than the outer edges, water will run around the dam and erode the side slopes of the ditch, causing erosion. If the ditch is shallow and you are using triangular silt dikes, you might need to add sand bags to create a point that is lower than the center.

Video: David Jenkins
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