Summary of this posting
Below I present evidence, based on my on-site inspections during two rain storms, that Speedway Sand and Gravel is
- not following the sediment control plan, and that
- the plan itself relies too heavily on ineffective measures.
Since complaints after the first rain of 5/26, we note a number of improvements, but by the rain of 6/2, Speedway had again neglected the most basic measure--street sweeping before the forecast rain.
Because of these shortcomings, a noticeable plume of muddy water has been observed twice in Lake Wingra.
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This morning, City Engineering sent an email to persons concerned about the problem of sediment escaping from the Edgewood Av street construction site. I've reprinted most of this email below, and then I'll follow up with evidence for or against statements in the email. This evidence consists of photos and observations I made during the two rain storms (5/26 and 6/2).
"City Engineering has required Speedway to complete an erosion control implementation plan which was completed and submitted to WDNR.
On this project our staff worked with the contractor to implement the plan which included:
- Construction Entrances/Tracking Pads
- Construction Entrance Berm
- Wing dams (along the side of the road where the road has been disturbed)
- Construction Phasing (keeping as much pavement as possible – currently about ½ the pavement is still in place)
- Sweeping of the remaining onsite pavement and pavement surrounding the project
- Inlet filters
- A sediment trap (at the Vilas end)
- Limited siltsock/logs
We will be implementing today the use of polymer on all disturbed surfaces and we are investigating the possibility of inlet filters exceeding the WDNR guidance (more restrictive fabric).
I believe both City Engineering and the Contractor have taken erosion control very seriously."
Construction Entrances/Tracking Pads
This refers to a pad of gravel which helps prevent muddy tracks spreading mud outside the construction site.
The gravel pad is visible in the middle-ground. It is so narrow as to be mostly ineffective--you can see the muddy tracks entering Monroe St. Photo taken 6/1.
It works by shaking off a bit of mud, plus preventing additional mud from being picked up as the vehicle leaves. It can only be truly effective if entering delivery vehicles never go beyond the mud-free pad--in other words, if they stay out of the mud at the site.
On my first inspection before rain on 5/26, there was no "tracking pad" at all on the main entrance, at Monroe and Edgewood. A patch of mud here was causing all trucks to pick up mud as they left the site, spreading it NE on Monroe St. Soon after this, the pad was installed here--it did correct this one muddy spot, but trucks were still traversing the rest of Edgewood, where the pavement was sometimes muddy and not being swept.
Moreover, there are five other streets (including an alley) entering this site, most of them being used by heavy equipment. There were NO tracking pads or berms at these entry points. So, at best, one out of six entry points complied with this part of the plan, and they complied only after the first heavy rain, at least a week after construction started.
Construction Entrance Berm
This refers to a raised area of earth, sufficient to divert runoff from leaving via the construction entrance area.
Of course, if the slope dips back to the construction area, as it does at Monroe and Edgewood, then no berm is necessary. Where paved streets enter the construction zone but slope away from the zone, no berm is possible without ripping up the street, which would only make matters worse.
Obviously, to comply with the spirit of this requirement, something else is needed, such as really effective control of sediment in the gutters here. On the side streets of Madison, Jefferson, Adams, and Vilas, control of sediment leaving the area in the gutters has been mostly limited to sediment traps in the stormwater inlets. But these traps are ineffective--more below.
Wing dams
These are dams of gravel in the gutters.
This wing dam on Madison St. was ineffective because water bypassed it, going into an unfiltered stormwater inlet beyond. Photo 5/26. Click on photos to enlarge.
They slow the rush of stormwater on hills, and they can provide some filtration of the water, depending on the size of the gravel. On the first rain of 5/26, there were only a few wing dams. The most important one, on Madison where most water was leaving, was completely ineffective.
After 5/26, a number of wing dams or gravel berms were added. I would say that most of these ARE effective in slowing the water and filtering large debris, but they cannot be effective in filtering fine particles.
This gravel dam, near the top of Edgewood Av, was more effective, stopping larger particles. 5/26.
Construction Phasing
This is retaining as much pavement as possible – currently about ½ the pavement is still in place.
My observations indicate that, as of today, this is being done and is being effective.
Sweeping of pavement
Sweeping of pavement is done with a Bobcat, using a roller brush and a sort of dustpan--rather like an old fashioned carpet sweeper.
Successful measures:
The pavement was swept clean, afternoon of 6/1.
Photo also shows construction phasing--retaining as much pavement as possible to minimize mud. The gravel on left is to protect the terrace, where the curb has been damaged.
Sweeping of pavement, in my estimation, is the simplest and most basic sediment control measure for this type of construction site. It must be done at the end of the day if there's any chance of rain--it takes, perhaps an hour? If this is not being done, it would be a good sign that erosion control isn't being taken seriously.
Sweeping of the remaining onsite pavement had not been done when I inspected before the rain (and during the rain) on 5/26. When I inspected several times between 5/26 and 6/2, the pavement had been swept.
But when I inspected during forecast rain on 6/2,
both the pavement and the gutters were quite dirty.
If sweeping did occur that day, it was "undone" by subsequent work.
According to Tim Troester (emails), contractors are supposed to sweep as far beyond the site as muddy tracks can be found. However, Speedway Sand and Gravel has only swept a short distance down the side streets, no more than 125 feet (I paced it). When noticeable mud was tracked onto Monroe Street on 5/26, there was no sweeping on Monroe.
In fairness to Speedway, I believe that sweeping more than one block beyond the construction area is impractical, even though significant amounts of sediment can escape this way. Instead, I believe that the City should require that tires of trucks exiting muddy sites should be cleaned with a high-pressure water spray, as is done in some other parts of the country.
So, sweeping "pavement surrounding the project," as is called for in the plan, is NOT being done.
Inlet filters
These traps, inserted into the inlet of storm sewers, work like giant coffee filters.
They are frequently the last line of defense against sediment leaving a site. Unfortunately--even if installed correctly--they are mostly ineffective (based on my observations during two rain storms).
Some of these filters were only installed after the first storm, and most of them are installed incorrectly. I believe that most of the sediment escaping the site is via these stormwater inlets, past these failing filters.
Filters work only as long as they do not become overloaded and clogged. Maintenance is required. I have seen no evidence that any of these filters have been emptied since construction began.
The most obvious failure of these filters, visible to anyone during rain, is that (because of clogging or improper deployment of the flaps) they allow water to bypass them and flow to the next unfiltered stormwater inlet.
The ineffectiveness of these filters raises an important question. Even if they are on the plan, even if they are installed correctly at all the necessary spots--still they will not protect the lakes. The Best Management Practices need to be revised.
A sediment trap at the Vilas end
This refers to anything that traps and retains sediment at the bottom of the steep hill on Edgewood, near the lake.
As of 6/2, there were three such structures:
Gravel-filled pit at bottom of Edgewood.
No water is leaking past, except via stormwater inlets. 6/2
A gravel dam and gravel-filled pit in the street. This is being effective--nearly all surface flow from the street directly above is going into this large pit. However, where this part of the plan fails, is that much dirty water above this pit is going into the stormwater inlets, with their failing filters. From there, the muddy water goes directly to Lake Wingra, where you can see the muddy plume spreading.
There are two cloth dams on the W side of the bottom of Edgewood Av, on the terrace.
The one further from the street (left) has been well-built and will function in a severe storm. However, with the storms so far, rain onto the grassy turf above this point is being completely absorbed. So this barrier is doing nothing to absorb any muddy runoff from the streets.
The second cloth dam, where Edgewood meets the lane along the shore, in my estimation serves no good function. There is only a trickle of muddy runoff in the gutter here, and this dam does noting to stop it. 6/2.
In summary, the sediment traps at the Vilas end of Edgewood Av aren't fully working, because the muddy water from higher up is bypassing the barriers by entering stormwater inlets. I believe the gravel pit will work, when the bypass is eliminated.
Limited silt sock/logs
Silt socks are fabric tubes about 18" in diameter, filled with mulch, sand, or other material.
I have watched their use at Sequoia Commons, and note they are quite effective, but only for relatively small flows. They are able to filter out all but the finest particles.
At a street construction site, the biggest problem is muddy water flowing on the remaining pavement, and from there into stormwater inlets where the filters are ineffective. The cloth dams can't be used on pavement. Gravel wing dams don't stop the finer particles. So it appears that creative use of many silt socks could be used to trap the street runoff, and direct this runoff to more robust treatment basins on terraces. The silt socks deployed around stormwater inlets could also augment the failing inlet filters.
Given the effectiveness of silt socks, plus the lack of alternatives, we ask: Why does the plan call for "limited" silt socks?
During the rain on 5/26, no silt socks were deployed.
By the rain of 6/2, a silt sock was employed effectively (along with a wing dam) above the Madison-Edgewood intersection. Effective, except that again the water was doing an end run--this time by flowing into the storm sewer, then upwelling from the storm sewer just beyond the silt sock (at the N corner of Edgewood-Madison).
A second silt sock was deployed on 6/2 at the Edgewood-Jefferson intersection, in the gutter. But with the entire length of sock stuffed into one tiny gutter, it was evident that this had been done hastily, and that most of the sock was wasted. With more forethought, parts of this sock could have been profitably deployed in many other gutters.
Improvements between 5/26 and 6/2
After speaking to Foreman Todd Timmerman before the rain on 5/26, and presenting my photo reports to owner of Speedway Tom DeBeck and City inspector Tim Troester, there were a number of improvements:, for which credit is due:
- Street sweeping was finally begun, including the gutters (but only on-site)
- Gravel wing dams were added in numerous places
- A gravel pit and berm was constructed near the lake
- A silt sock and gravel dam was constructed above the Madison-Edgewood intersection, where much runoff exits the site. A second silt sock was stuffed in one gutter.
- A second inlet filter was added further down Madison (both sides). There were changes to and around some of the inlet filters.
- A gravel pad was added at the Monroe entrance to Edgewood.
- A second cloth dam was added to the terrace at the bottom of Edgewood near the lake (though it doesn't seem to do much).
The email above indicates additional improvements are underway. Construction today was halted after a third rain, and the foreman was onsite, planning improvements.
Are fines called for?
I would like to hope that these improvements mean we should be patient--that Speedway means to comply.
Yet two facts contradict optimism:
- Why did Speedway fail to begin most parts of the required plan--until after complaints, and after the first storm?
- Why did Speedway fail to sweep--before the second storm? Sweeping is the most basic (and simple) aspect of sediment control. It should be taken as an "indicator" of a street contractor's intentions to comply. And if they are unable to comply, then an indicator of their competence.
The photos speak volumes. Speedway has not been in compliance with their sediment control plan. They started late, and implemented some parts poorly or not at all. The plan itself relied on ineffective measures. The only unqualified success was the construction phasing.
The bottom line: Twice, sediment escaped to Lake Wingra. Photo:6/2
Options going forward
- Fine Speedway for non-compliance with plan, which has clearly occurred.
- Place Speedway on a list of "unreliable" contractors, as recommended by the Subcommittee on Construction Site Erosion.
- Amend the plan to include more effective options, such as those mentioned above in Engineering's email, or use the terraces to filter or infiltrate runoff.
Links to additional photos
Edgewood Av Construction before the rain, 5/26/10
Edgewood Av Construction during the rain, 5/26/10
Edgewood Av Erosion Control Improvements, 6/1/10
Edgewood Av street construction during rain, 6/2/10
Edgewood Av Erosion Control Improvements before rain, 6/5/10
All photos on inlet filters from 5/26 and 6/2.
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