Water-Resources Investigations Report 92-4147, "Effectiveness of highway edgedrains,"

In Reply Refer To:                                December 2, 1992
Mail-Stop 415


Subject:  Water-Resources Investigations Report 92-4147,
          "Effectiveness of highway edgedrains," by Hillary H.
          Jeffcoat, F. A. Kilpatrick, J. Brian Atkins, and
          J. L. Pearman

The purpose of this memorandum is to announce and transmit the 
subject report, which was prepared in cooperation with the Federal 
Highway Administration.  It details a study performed in 10 States 
to study the effectiveness of retrofitted edgedrains in removing 
surface and subgrade water from highways.

The 10 highway sites were instrumented to measure concurrent 
rainfall and edgedrain discharges, piezometric water levels, and 
soil moisture under the pavement and adjacent shoulders.  Soil 
samples were also collected and their physical and hydraulic 
properties measured; all sites were found to have relatively low 
permeabilities.  Fifty selected rainfall-runoff events were 
analyzed to assess the amount of infiltration reaching the 
pavement subgrades, amounts and timing of edgedrain discharges, 
and the manner of water movement beneath the pavements.  The data 
indicate that retrofitting longitudinal edgedrains to an existing 
highway provides a sink to collect water draining laterally off 
the pavement surface as well as water reaching them from the 
subgrade voids and channels.  The tight, low permeability subgrade 
material found to exist at all 10 sites precluded ready lateral 
drainage with or without edgedrains.  The data indicate that most 
of the lateral subgrade movement of water is through voids and 
channels that develop under the pavements.

In addition to providing data as to the effectiveness of 
edgedrains, this study also developed and tested instrumentation 
and techniques for studying pavement drainage.  A dual-tipping 
bucket gage proved most effective in concurrently measuring 
rainfall and edgedrain discharges.  Pressure transducers were 
effective in measuring piezometric water levels beneath the 
pavements.  Data loggers proved effective in not only recording 
all data but could be programmed to operate the sensors only to 
the extent needed.  The need to acquire and analyze core samples 
of the subgrade material for physical and hydraulic properties in 

Additional copies of this report may be obtained from:

     Hillary H. Jeffcoat       or       F. A. Kilpatrick
     JEFFCOAT                           (703) 648-5010
     (205) 752-8104

                                Ernest F. Hubbard
                                Assistant Chief
                                Office of Surface Water