Field tests in western Fresno County have confirmed laboratory tests indicating that glass fiber filtering materials can be used to satisfactorily replace the sand filters which have been standard practice in drain tile installations, but which may be quite costly in some areas. No information is yet available on the life of glass fiber filters. It was hoped to obtain quantitative evaluation of the effectiveness of several types of glass fiber filters in comparison with sand filters, but comparisons were masked by extreme variation in the sodium status of the soil. Glass fiber filters generally filtered out more of the fines than did sand filters.

This work was a cooperative endeavor of the Department of Irrigation and Soil Science, UCLA; the J and J Ranch of C. W. Jones, Firebaugh; the Land Improvement and Development Corporation, Dos Palos; the Owens-Corning Fiberglas Corporation, Santa Clara; and the USDA Soil Conservation Service, Firebaugh.