Pea gravel envelopes for tile drains in Coachella Valley

The average water application on the 60,000 acres being farmed in Coachella Valley is about seven acre-feet per acre per year. Infiltration rates are high, especially on the high ground. As a result practically the entire valley under canal irrigation has a high water table and must be artificially drained. Tile installations were started in 1949. By 1967 there were approximately 1600 miles of drain tile on farms. An extensive outfall system has been installed and maintained by the Coachella Valley County Water District. Both the water distribution system and the drainage system are almost entirely underground. Problems with poor water infiltration through the usual envelope of sand surrounding the tiles, led to this study of the effectiveness of pea gravel as a tile envelope.