Tuesday, May 14, 2013

May 2013 BMP Q&A

By: Todd Thomas, Water Resources Forester, Texas A&M Forest Service

Q:  One type of temporary stream crossing that I have heard mentioned, but never seen or even heard discussed in great detail are PVC bundles.  What exactly are these and how can I construct my own?

A:  Excellent question about an innovative stream crossing method.  PVC bundle crossings can be constructed relatively cheap from readily available materials and can be re-used and repaired without issue.  While not suited for large streams, PVC bundles can be used on most ephemeral and intermittent streams with a U-shaped profile that are not more than 10-feet wide and 4-feet deep in channels with low flow.  Think of these bundles as a large handful of straws. 

In order to create a 12-foot wide pipe bundle that is 16-feet long when laid flat, you will need 12 20-foot joints of 4-inch diameter schedule 40 PVC pipe, four 18-foot lengths of 3/16 inch galvanized steel cable, and eight 3/16 inch cable clamps.  The 20-foot joints of pipe should be sawed into 12-foot sections with the remaining eight feet sawed in half so there are two 4-foot joints, per 20-foot joint of pipe.  Next, drill ¼ inch holes completely through the 12-foot long joints at locations 2-feet and four-feet from either end; on the 4-foot long joints, 2 ¼-inch holes should be drilled, each 1-foot from the end.  Alternate one 12 foot long joint with one row made of two 4-foot wide joints placed 2-feet from each other.  Finally, you will connect the joints of pipe.  To do this, string each strand of galvanized cable through the holes in each joint of pipe.  Once strung through, make loops on the ends of each cable and secure them with the cable clamps.  Each cabled section should be loose so pipes can conform to the stream channel.  When you are done there should be 2 4-foot sections of PVC remaining, these can be used at your discretion.   

In order to utilize your newly constructed bundle, begin by lying on end of the pipe bundle at the top of the bank and allow the rest of the bundle to lie in the stream channel slowly piling it back on top of itself.  The ends of the bundle should be resting on banks opposite each other.  The loops in the cable can then be used to tie off the bundle to anchor points on each side of the stream.  You may want to lay boards across the bundle perpendicular to allow for better traction when crossing.  When it is time to remove the crossing, simply undo the anchor points and lift the bundle out by the cables that are attached the pipe on top.  After the bundle is removed be sure to inspect it for any damage and replace any damaged pipes before re-use. 

Once the bundle has been removed, always remember to stabilize your approaches, just as you would with any stream crossing.  Also, keep in mind where appropriate stream crossings should be located: straight sections of stream that can be approached at a 90-degree angle.  This concludes this month’s BMP Q&A, remember you can send any questions to me at tthomas@tfs.tamu.edu, or you can phone them in by calling (936) 639-8180. 

*This article was published in the May 2013 edition of the Texas Logger