Construction Specification 444—Subsurface Drainage
The work consists of furnishing and installing tubing and the necessary fittings and
appurtenances as shown on the drawings and as outlined in this specification.
Corrugated polyethylene tubing and fittings shall conform to the material requirements
of ASTM F 405, ASTM F 667, ASTM F 894, AASHTO M 252, or AASHTO M 294. All
corrugated polyethylene tubing shall be heavy duty unless otherwise specified on the
plans. The tubing shall be appropriately marked with ASTM or AASHTO designation.
When perforations are specified, the water inlet area shall be a minimum of 1 square
inch per lineal foot of tubing. The inlets either shall be circular perforations or slots
equally spaced along the length and circumference of the tubing. Unless otherwise
specified, circular perforations shall not exceed 3/16 inch in diameter, and slot
perforations shall not be more that 1/8 inch wide.
Geotextile filter socks, when required, shall meet the material requirements specified.
Outlet pipe shall be 10 feet of schedule 40 PVC or equivalent strength of the same
diameter as the tubing.
Granular filter/envelop material, when specified, shall consist of a clean, well graded,
coarse sand-gravel mixture. The maximum size shall be ½ inch. No more than 5
percent shall pass the No. 200 sieve. Crushed or processed stone that is ½ inch or less
is also acceptable.
Bedding/ blinding material, when specified, shall consist of material free of hard clods,
rocks greater than 1 ½”, frozen soil, or fine material that will cause a silting hazard to the
drain (typically not more than 10% shall pass the No. 60 sieve).
Unless otherwise specified or approved by the engineer, excavation for and subsequent
installation of each tube line shall begin at the outlet end and progress upgrade. The
trench or excavation for the tubing shall be constructed to the lines, depths, cross
sections, and grade shown on the drawings, or as ap