The Pickford St project involves installing a new stormsewer, plus water mains and resurfacing. The street in in an environmentally sensitive area, on a slope close to Lake Wingra.
On Aug. 8, there was a brief but heavy downpour, providing an opportunity to see how erosion control measures were working.
View uphill from Monroe St. At first it seemed there was no escape of muddy water, at least on the surface.
But then, I noticed a cave-in, under the gravel pad. This may have allowed muddy runoff to escape unfiltered into the storm sewer.
Numerous gravel check dams on either side of the street trapped some of the runoff. But additional runoff was directed to the center of the street, where it formed a concentrated flow. This kind of arrangement caused massive erosion in a big storm last year on Edgewood Ave.
This is the outfall of runoff from the Pickford St area, into Lake Wingra. Much muddy runoff was going into the Lake.Overall quality of the erosion control
I give this job a grade of "B" (good but not excellent).
What I liked
- Good gravel pads at either end.
- Large check dams, slanted upstream to capture & store runoff
- Good deployment of inlet filters
What could have been improved
- The dirt surface of the work area did not appear to have been treated with polymer or compacted with a roller, as Parisi Construction did during similar work on Gilmore Street.
- There was no defense against formation of a gulley in the middle of the street.
- Could the cave-in have been foreseen or prevented?
- Muddy runoff did escape into Lake Wingra.
Update 8/23/11: After a very intense morning downpour, I saw that runoff had escaped from the bottom of the Pickford St. site. No additional stormsewer inlets have filters on them, so these need to be added. The pavement below the entrance to Pickford is very dirty.
Debris on the terrace indicates runoff from a storm on 8/23 escaped the site to stormwater inlets that were unfiltered.
No comments:
Post a Comment