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r ., <br />2 <br />STATE OF CALIFORNIA GEORGE DEUKMEJIAN, Governor <br />CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— <br />CENTRAL VALLEY REGION <br />3443 ROUTIER ROAD <br />SACRAMENTO, CA 95827-3098 <br />21 April 1989 <br />Mr. Greg Basso <br />Forward Inc. <br />P. O. Box 6336 <br />Stockton, CA 95206 <br />FORWARD LANDFILL, SAN JOAQUIN COUNTY (CASE NO. 2209) <br />We have reviewed the construction report for the expansion of <br />landfill waste management unit (WMU) D, referred to as <br />WMU D-88, submitted by EBA and the supplemental data provided <br />by Kleinfelder. The landfill was proposed as a Class III <br />with a bottom liner consisting of 4 feet of clay compacted to <br />90 percent, or greater, of maximum density. Laboratory per- <br />meability tests were to be conducted on liner samples to <br />correlate permeability to density (see letter and report from <br />EBA dated 8 November 1988). <br />The data provided in the construction report included the <br />results of three laboratory permeability tests on a block of <br />compacted soil cut from the finished liner, 92 moisture <br />/density measurements made on the liner using a nuclear gage, <br />and certified design and construction drawings. The <br />permeability test results were 6.3 x 10-8 cm/sec at a depth of <br />1.0 to 1.8 feet, 1.1 x 10-6 at a depth of 1.8 to '2. 8 feet, and <br />4.6 x 10"4 cm/sec at a depth of 3.0 to 4.0 feet. <br />The nuclear gage data indicate that the liner was compacted <br />to densities between 95 and 110 pounds per cubic foot or <br />approximately 90 to 98 percent of maximum dry density for the <br />soil types used in construction. Moisture contents ranged <br />from about 14 to 28 percent. Optimum moisture contents for <br />these soils range from 16 to 2u percent. In the future, <br />laboratory oven -dried moisture contents on the soils also <br />need to be determined to verify the nuclear gage moisture <br />measurements. Density measurements should also be verified <br />with sand cone or similar tests. Calibration data for the <br />nuclear gage should be submitted with future construction <br />reports. <br />EBA did not provide a plot to relate compacted soil densities <br />to permeability. <br />In order to use density tests as a control to determine when <br />a clay liner meets the regulatory requirement for a maximum <br />permeability of 1.0 x 10-6 cm/sec, permeability tests must be <br />