Re: Building bridges

["Judy A. Worley" <aussie@aa.net>]

The Wash. state DNR  has a handbook Recreation Trail Maintenance.  Puncheon
bridges are constructed of hand split Douglas fir, or cedar 6" min. dia..
with 6" or more curb
logs installed on top, along the sides, secured with large wood stakes.
They also have "Trails Management Handbook".  Both are for volunteers, but
still require a DNR engineer to assess the requirements.   I hope this
helps.  Judy Worley, Duvall, Wa.
-----Original Message-----
From: BMcCrary27 <BMcCrary27@aol.com>
To: Weetreefan@aol.com <Weetreefan@aol.com>
Cc: ridecamp@endurance.net <ridecamp@endurance.net>
Date: Tuesday, April 14, 1998 9:43 PM
Subject: Building bridges


><<My son, for an eagle scout project, will be building a bridge across a
>stream
>to extend a trail on Department of Natural Resources land.  The stream
banks
>have become too eroded for the horses to ford easily so entire loop of
trail
>has been unused for over two years.  he has the assistance of the DNR as
well
>as local riding groups.  These trails are considered multiuse but no
motorized
>vehicles are allowed and they are too narrow for carts.  We now need to
come
>up with the specs for width and weight holding capacity.  Does anyone have
any
>idea if there is a standard out there that we can present to the DNR as a
>guidline.  Something that says "for safty purposes all bridges expected to
be
>crossed on horseback should be at least ______ feet wide and be able to
>support ________pounds.  Both we and the DNR are at a loss for how much
these
>figures are.  I'm assuming the width will be between five nad six feet but
the
>weight part has me stumped.  I've ridden these trails and really hope to
have
>the whole section open again soon.>>
>
>We've built a number of bridges on our own and on California State Parks
>trails. Of course, the length of the bridge would dictate the of size of
the
>stringers and whether a bent was needed to help support the center and
dimish
>the "bounce" in the bridge. Five to six feet wide is adequate and a
carrying
>capacity of about three tons would give a good margin of safety. Most of
these
>bridges are built with at least 6" X 8" timbers or similar size logs for
>stringers and with 3" thick planks for decking. If the bridge is fairly
close
>to the stream bed, it wouldn't need rails, but if it is high above the
stream,
>rails would offer a sense of security.
>
>Lud McCrary
>