Last Thursday, July 21, a contractor started laying erosion control blankets along the East Cannon River Trail and other areas of construction from the Babcock Park Lift Station & Interceptor Sewer Project.
When biking the trail, however, I noticed that the silt fence, washed out in more than a dozen places a week earlier by the heavy rains (5 inches?) on July 15, had not been fixed. With thunderstorms in the forecast for the weekend, I wrote to City street/engineering staffers Sean Simonson and TJ Heinricy:
Sean/TJ, I noticed yesterday that the silt fence along the East Cannon River Trail has been washed out in many places since last Friday’s heavy rains. I see the contractor is putting down the erosion blankets rather than repairing the silt fence. And at the south end of the trail, there’s no silt fence at all along the unpaved section of the trail, with several places where they’ve just pushed dirt up to the river’s edge. With the probability of more thunderstorms this weekend, what’s the plan to remedy this?
I got this email back from Brian Hilgardner, Senior Project Manager, for Bolton & Menk, an engineering consulting firm that works with the City:
Griff, Sean is out of town on vacation, however, I was made aware of your concerns for potential erosion control along the Cannon River Trail. The Contractor replaced much of the silt fence along the entire corridor approximately three weeks ago. Obviously, the heavy rains took its toll on some of the silt fence. The Contractor wasn’t able to get any equipment onto the site to make repairs earlier this week because they would have made conditions worse because the soil was still wet and soft.
They are currently placing seed/mulch and erosion control blanket to stabilize the entire site. They will also be repairing silt fence today. The erosion control blanket is actually a much better and preferred erosion control Best Management Practice (BMP’s) according to the Minnesota Stormwater Manual, and as indicated in my training for Erosion and Stormwater Management Certification. In fact, silt fence is one of the least preferred, yet still most commonly used because of its lower cost.
By the end of the day, everything should be stabilized again. Please call me if you have any further questions or comments.
I replied to Brian:
Thanks much for your detailed, quick response, Brian. Good to know that it’ll be stabilized by day’s end.
Will that include along the south, unpaved end of the trail by the old Village School? There’s no silt fence there at all and it doesn’t appear that that section will be ready for erosion blankets for a quite a while… probably until after it’s paved, right?
I did instruct the contractor to get silt fence installed on that end today. You are correct, that end will not be fully stabilized until it is paved, hopefully sometime next week if the weather remains decent. I appreciate your concern for these issues and please feel free to contact me in the future if you have any comments or questions.
The contractor did fix the silt fence by the end of the day on Friday. I was thrilled. The weather did not "remain decent" however; we got nearly 2 inches of rain in about 30 minutes on Saturday morning. I rode the trail to see the results.
As you can see from the above photos, the silt fence along the unfinished south end of the trail did its job.
And with a few minor exceptions, the erosion control blankets did their job.
But on all the inclined areas where the contractor had not placed blankets, the straw/seeding just washed away. In most places, the repaired silt fence caught the runoff.
I wrote to Brian yesterday:
Brian, Nice work! The erosion blankets did their job during Saturday’s deluge, with a few minor exceptions. And the silt fence at the far south end did its job. But all the slightly inclined places where erosion blankets were NOT used, the straw was just washed away/ruined. What’s the plant to fix that?
We are actually driving the site right now. We will likely have them overseed the entire project and mulch again. I will keep you posted.
Kudos to Brian and City Hall for the handling of a challenging situation.