The Subsurface Infiltration System (which was tested and evaluated in a practical situation) was designed to be placed in a planting hole with a five-foot minimum diameter. This system is designed for trees with root balls up to 36-inches in diameter and root ball depths no less than sixteen inches. This depth is necessary to ensure that the gravel blanket used is a minimum of 12 inches below the surface and that the water is supplied to the root ball. Depth of the planting hole is equal to the depth of the root ball, plus 6 inches for back-filling as specified in the state planting specifications. The system uses 3/4-inch class 200 PVC or polyethylene pipe and schedule 40 PVC or "Turnseal" fittings in its design. It has adjustable flow control plastic bubbles heads to dispense the water. A 4-inch diameter, non-perforated, corrugated plastic drainpipe used as a sleeve, is placed over the riser and bubbles head assembly. Plastic sheeting is used under the gravel blanket to produce a wider dispersion of the water being applied. A tensiometer and automatic controller may be used with the system. Details are given of the site selection, the plants, installation of the irrigation system, and the data collection. The results of the research effort are detailed. The details are also given of the soil moisture measuring methodology.

  • Corporate Authors:

    Washington State Department of Highways

    Highway Administration Building
    Olympia, WA  United States  98501
  • Publication Date: 1977-10

Media Info

  • Features: Appendices; Figures;
  • Pagination: 41 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00189459
  • Record Type: Publication
  • Report/Paper Numbers: USDOT 32-1 Final Rpt.
  • Contract Numbers: HR 475
  • Created Date: Apr 12 1979 12:00AM