The Philadelphia Mountain Biking Association - Mud on Demo Trail Follow-up

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:      jill@imba.com
   Subject:    Re: Demonstration trail observation
   Date:    March 17, 2007 4:33:16 PM EDT
   To:      mccarthy@fow.org
   Cc:      ddannenberg@mac.com

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
jill@imba.com

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

www.fow.org

From: Mark Pennington
Sent: Thursday, March 15, 2007 12:15 PM
To: mmccarthy.fow@verizon.net; 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