Sheetflow Erosion and Sediment Control

June 24, 2020

Silt Fence and Trackout Fail Part 2

This is a follow up to Silt Fence and Trackout Fail post from April 6, 2020. Same old !@#$, different month.

Photo: David Jenkins
Photo: David Jenkins

June 17, 2020

Silt Fence Overlap

Photo: David Jenkins
Photo: David Jenkins

This silt fence surrounds a compost (Groco) stockpile, most of which will be used over the next several months. I don’t expect any runoff; this is a very low risk situation. Being low risk, i am okay with how the fence ends were joined. The orange fence ends overlap about 3 or 4 feet. The black is placed at the overlap seam, with about 3 or 4 feet of black fence on either side of the seam. The fence flaps are trenched in and covered with soil.

If this were a high risk situation, I would have required the contractor to use one continuous orange fence with no seams. Another option is to wrap the fence ends several times around a post and drive the post in. this effectively makes the fence one continuous installation.

June 11, 2020

Phasing a Stockpile Project to Prevent Dirty Runoff From Draining to Wetlands

Phase 1-

(A) Install silt fences on perimeter and at base of future stockpile.

(B) Clear, grub, grade, construct drainage ditches and temporary stormwater pond including outlet structure and perforated pipe level spreader drains. Grade to drain water away from outer perimeter silt fence and toward ditch.

(C) Hydroseed and install blankets in ditch line.

(D) NOTE: Background stockpile, built later, used an early generation construction stormwater treatment system and discharged to creek instead of level spreaders into vegetation.

Phase 2-

(A) Place and compact fill material to approximately 20 feet of vertical elevation.

(B) Trackwalk and hydroseed slope.

Phase 3-

(A) Same as Phase 2.

(B) Same as Phase 2.

Phase 4-

(A) Place and compact fill material to approximately 20 feet of vertical elevation. Start base of slope 15 feet in from lower fill and grade to drain away from lower slope and to the stormwater pond.

(B) Trackwalk and hydroseed slope.

(C) No hydroseed on top of the pile as material is continually brought in as available.

May 4, 2020

Drive-by Silt Fence Inspection

Video: David Jenkins

It doesn’t take more than a few seconds to see that this silt fence has problems. While the risk of sediment discharge is low, the condition of the fence says to me ” We don’t really think this TESC stuff is all that necessary.” If it was my job to inspect, I would be making a “U” turn to have a chat.

April 28, 2020

Cool Things to do With Compost

Photo: David Jenkins

The bulk of the work will take place to the right of the silt fence. The grass will be removed and the area re-graded. The grass to the right of the construction fence will remain undisturbed. Some work will occur on the taxiway to the left of the tractor. Rather than use silt fence in this low risk area, compost berm will suffice. When done, the construction fence and stakes will be removed and re-used elsewhere and the compost will be spread out on the grass.

April 21, 2020

Hot Mix Asphalt Berm

Photo: David Jenkins

The work area is the left. All runoff is diverted by silt fence and this asphalt berm to a sump, where it is pumped to a chitosan-enhanced sand filtration treatment system. This system prevented all turbid site water from entering the roadside ditch-outside of the silt fence-from draining to a creek. Note the mud on the left side of the berm and the clean asphalt on the right.

Since this is summer work and perimeter BMPs are containing all site runoff, we are not covering bare soil.

Upon completion and soil stabilization, the asphalt berm will be removed and hauled to an asphalt batch plant for recycle.

April 9, 2020

Good Use of Silt Fence

Photo: David Jenkins

This silt fence is being installed to contain a five acre crushed concrete pile. It is trenched in, staked every six feet, has wire backing and uses zip ties to secure it to the stakes.

Crushed concrete from 16 Center Reconstruction Photo: David Jenkins
Crushed concrete from 16 Center reconstruction with silt fence. Photo: David Jenkins

April 7, 2020

Silt Fence Water Bars Fail

Photo: David Jenkins

Whenever I see something like this, it makes me think that the site owner/contractor either didn’t know what they were doing or bit off more project than they could chew, or both. These guys cleared, grubbed and graded something over 80 acres starting in late summer, failed to phase the work, failed to use soil cover practices, failed to listen to the experts and got nailed by the fall rains.

Erosion control is really about water control: reducing volume, preventing it from becoming turbid, and controlling where it goes. By the time the rains hit this project, there was too much water, it was too dirty, and there were too few options for controlling where it went.

In addition, they refused to set up a chitosan-enhanced sand filtration system to treat and discharge water; this left them no options and too much turbid water that had nowhere to go. As a result, they hammered a wetland, were fined heavily, and were shut down for months.

Silt fences are not meant to control water, convey water, filter water; they are designed to control eroded sediment. Ditches, berms (rock, gravel, triangular silt dikes, etc.) would have been better choices at this location. Not opening up so much area so late in the season would have been the best option. Their means and methods did not save them time or money.

April 6, 2020

Silt Fence and Trackout Fail

Photo: David Jenkins

Just minding my own business last Friday, driving from Fred Meyer to the UPS store and passed this project. 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. 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 being 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. Someone 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!

April 1, 2020

Compost Berm

Photo: David Jenkins

We rarely use silt fence on smaller airfield projects because: the work areas are nearly flat, are surrounded by grass or pavement, the work takes a few months, usually in the summer or fall. Compost berms are frequently used to: contain water, divert water, prevent site runoff. A secondary benefit is filtration; there is some turbidity reduction. Lastly, when done,. we spread the compost out over the disturbed soil and hydroseed it, enhancing grass growth and eliminating the waste of land-filling silt fence.

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