Culvert Renew Installation Bulletin

Cleaning the Existing Culvert
Depending on the condition of the culvert, and it's location, a variety of cleaning methods and equipment can be used.  Cleaning the culvert may be done with available pipeline/sewer cleaning equipment.  High pressure washers are also effective cleaning tools, as are local fire departments who have been extremely helpful to maintenance departments in cleaning deteriorated culverts.  Regardless of the cleaning equipment employed, the cleaner the culvert is, the easier the culvert rehabilitation projects will be.

Insert A Cable Through The Culvert
Unless the linder is to be pushed through the culvert, it will be necessary to insert a cable through the culvert.  This can be accomplished using a variety of methods including floating a string through the culvert during cleaning.  We know of one highway department that shoots a cord through the culvert with a bow and arrow and then uses the cord to pull the cable through the culvert.

Will The Culvert Liner Fit
To determine of the culvert liner will fit through the culvert, you can pull a plug or pulling head through the culvert.  Be sure to use a tag line so that the plug can be removed in the event that it cannot fit through the culvert.

Dropped Pipe Or Offsets
In many cases the liner will pull through offsets, but if the culvert pipe is bent so that the liner will not fit, in some cases a repair may be made by jacking the bent pipe back into shape to allow the liner to clear the offset.  If a repair is not possible, a smaller liner size may be required.

Pulling Heads or Cones
Pulling heads or nose cones are required in most culvert insert renewal applications.  Even in cases where the liner is to be pushed through the culvert, without a nose cone the liner can catch on the smallest obstruction.  A variety of soft or hard nose cones or pulling heads may be used.  One of the less expensive, and easiest nose cone/pulling heads to construct, can be made from scrap or excess pipe.  Simply cut pie shaped wedges out of the plain end of the pipe, and drill holes in the front of the remaining wedges.  When a cable is inserted through the holes, the wedges can be pulled together into a cone.  Since the other end is threaded the nose cone/pulling head can be used over and over again.

Liner Pipe Insertion
Screw the pulling head to the first section of the liner.  Attach the cable to the pulling head and pull the first section of the liner into the culvert.  Thread the following liner sections using a chain or strap wrench with a four foot bar to turn the pipe.  The previously inserted liner may have to be blocked or wedged in the culvert to prevent it from twisting.

Pushing And Pulling The Culvert Renew Liner
Pulling the liner into the culvert causes some stretching of the liner.  In addition to possible stretching the liner may be expanded from the excess temperature.  It is important to allow the liner to relax and come to the culverts ambient temperature, prior to cutting off the excess liner.  Once the liner has relaxed and the temperature stabilized, the excess liner may be cut off using a chain saw, skill saw, or a carpenters hand saw.

Annular Grout Backstop
A grout ring may be constructed from any material specified by the engineer.  Materials commonly used include wood or plastic grout rings.  Even wadded up newspaper can be used as a grout stop.  The backstop may be any length specified by the engineer but not less than one pipe diameter.

Grouting the Ends (Annular Space)
Once the grout ring or stop is in place, the annular space on the ends of the pipe should be grouted with a  non shrink hydraulic grout, (Dry-Loc or equal).  A variety of grouting methods may be used including the drilling of a hole in the top of the deteriorated culvert on the outside of the grout ring.  A board with a hole drilled on the top of the annular space may be used to prevent the grout from coming out the pipe ends, and to hold the grout in place until it sets.  Once the grout has set, some engineers require the drilling of 3/8" weep holes on the inside top of the grout ring, to allow excess water to escape.  Also this assumes the annular space will silt in over time.

Grouting the Entire Annular Space
This would be required only in rare instances where the deteriorated culvert is in imminent danger of collapse.  The grouting may be accomplished with a wet mud to a slurry cement.  Methods include the blocking of one end of the pipe and using a long grout pipe starting on the far end, and gradually withdrawing the rod as the annular space fills.  Another method would be to drill a grout hole down the center liner of the road, and pumping a wet slurry in the annular space until it comes out both ends.  The profile wall pipe itself can be used as a grout tube.  Drilling holes down the top of the pipe before it is inserted.  The pipe may have to be assembled prior to drilling the holes to determine the top of each section.  Insert a grout tube between the walls of the pipe and grout pumped until it comes out a hole drilled on the top of the other end of the wood stop.  This hole also allows air to escape.  Regardless of the grout method, care should be taken not to collapse the liner due to excess grout pressure.

Slope Boxes
Construction of a slope box is an excellent treatment of the inlet end of the culvert.  A slope box can be mowed over without damage to the culvert or the mower.  A slope box can also be constructed as an improved culvert inlet which substantially improves culvert flows.  Construction of a slope box is easy and inexpensive.  Cut off the "culvert renew" liner at an angle even with the slope.  Using a spade, dig out an area 3 feet by 3 feet and 4 to 6 inches deep.  Seal the pipe end with a non shrink hydraulic grout.  Construct the slope box concrete forms using 2 by 4 boards.  Fill the 3 by 3 area with a heavy concrete and finish by sloping toward the culvert pipe to improve water flow.  Our thanks to Edgar County, Illinois Engineer, Richard Bowles for his input on slope boxes and their construction.