Below from Jill Van Winkle who headed up construction and design of the Demonstration Trail. This is a bit of a follow-up of the discussion from a week or two ago, and echoes much of what was written then.
David, FOW
From:
Subject: Re: Demonstration trail observation
Date: March 17, 2007 4:33:16 PM EDT
To:
Cc:
Hi Maura,
It's unfortunate that they are experiencing mud along the new trail. However, given the newness of the trail and the weather conditions, it is not too surprising.
Trails need to "cure" and this process takes time and compaction. Time allows constructed tread to settle and harden. Use causes compaction, which reduces soil permeability, helping water to run across a properly outsloped trail, rather than percolating into the soil or scouring the tread. The existing trails in the park have had decades of heavy use and time to compact, becoming virtually impermeable (which is why, when closing these trails, we "rip" them, de-compacting the soil to allow water to percolate and plants to root). During the wet winter and freeze-thaw conditions, water saturates the not-sufficiently compacted tread and expands and contracts during the freeze-thaw cycles causing muddiness.
We did use a vibratory compactor on the tread, which helps to hurry the process, but time and continued use are the best cure. This process can take up to a year, depending upon weather conditions. On National Forest trails, where use can be more easily restricted, a newly cut trail often has at least a winter and spring to sit without use.
Some Parks limit use when trails are muddy, but this is not a very reasonable option for the heavily used trails in the Wissahickon (though signs and user education can reduce the number of users or steer them to other trails).
I'll take a look at the demo site while I'm at the Park this week to see if there are any other factors that might be affecting the drainage.
I hope this is helpful and that the trail dries out soon!
Best,
Jill
Jill Van Winkle - Trail Specialist
IMBA Trail Solutions
Hood River, OR
303/330-7888
On Mar 15, 2007, at 12:37 PM, Maura McCarthy wrote:
Jill, any ideas why this might be?
Maura McCarthy
Executive Director
Friends of the Wissahickon
8708 Germantown Avenue
Philadelphia PA 19118
215-247-0417, Fax: 215-247-9329
From: Mark Pennington
Sent: Thursday, March 15, 2007 12:15 PM
To: ; David Dannenberg
Subject: Demonstration trail observation
David and Maura:
I don't know if anyone has mentioned this condition to you yet but I thought I'd pass on an observation on the demonstration trail.
I rode the yellow trail yesterday from Belle's Mills to Lincoln Drive (on the Inn side of the creek) hoping that the trails would have dried out since the rain last weekend. Generally the trails had dried out well, just a few spots of mud here and there. Surprisingly, though, the demonstration trail was all mud--muddier than I've ever seen it and way more muddy than any other stretch of trail. I'm not sure why it would have retained water so much more than the rest of the trail system particularly since it always seemed to drain so well previously. Possibly something to do with the freeze/thaw cycle, maybe the trail design lends itself to retaining more water? Just a guess but it may be a good question to pose to the IMBA folks. If the whole trail system would have been in that shape, particularly with the number of riders who were taking advantage of the good weather yesterday, the trails would have been trashed.
I'd be curious to hear if the IMBA folks have any ideas.
Mark Pennington
Very interesting. So does this mean that muddy conditions on the new sections will be unavoidable this time of year. I wonder how much of a negative effect the heavy use will have on the shape of the tread. Maybe it will be necesary to do some maintenence on that section to help the drying process? Maybe it would be better left alone? We may see some outside berming on some of the tread surface.
This is a good learning experience for us to see the cause and effects of heavy use on such a new tread. Time will tell.
"Trails help humans make sense of a world increasingly dominated by pavement. They allow us to come more closely in touch with our natural surroundings, to soothe our psyches, to challenge our bodies, and to practice ancient skills"
Tom Coyle