CORRESPONDENCE_1992-1993 - Laserfiche WebLink

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Mr. Gabriel Karam -2- 18 October 1993 4. The„report concluded that the SP/SM material did not meet requirements and the County decided not to use the SP material in the final cover. The report did conclude that the ML and SM materials would be satisfactory because the laboratory permeability results were satisfactory. The report concluded that a SDRI test would not be necessary for both of these materials because field permeabilities would be lower. 5. Laboratory permeability for SM and ML were both around 1 x 10' cm/sec. We do not concur with the conclusion in the Kleinfelder report which infers from the SDRI test on the SP/SM soils, which failed to meet the 10.6 cm/sec permeability requirement, that the ML or SM soils will meet the 10-6 cm/sec permeability requirement. Since the laboratory permeability tests results were less than 1 x 10.6 cm/sec (-1 x 10' cm/sec), the report stated that the ML and SM soils would most likely be lower than the laboratory permeability test results and meet permeability requirements. No documentation was included in the report to support this assertion. Regardless, there still has not been a passing field test, as required by Chapter 15, on the materials to be used in the final cover. Liner soils must be classified in the field as either SC, CL, or CH under the Unified Soil Classification System. Prior to proceeding with test pad construction, the County acknowledged that they did not have the above materials present at the site; however, they would import Ione clay to be mixed with onsite soils. This mixture would be tested to see if it met the performance requirements. We requested that all mixtures that would be used in the final cover be tested. However, the County insisted that the mixture of SP/SM soils and Ione clay would meet the performance requirements. If the mixture passed, then the County would submit information which proved that the other mixtures would also meet the required permeability based on the laboratory tests. The SP/SM/Ione clay mixture failed the field permeability test and no information was submitted to suggest that the ML/Ione clay mixture would meet the field permeability requirements. Therefore, the County is required to conduct a field test on the ML or SM with Ione clay mixture, or any other materials to be used in the final cover, to verify that the materials meet the 10.6 cm/sec permeability requirement. It is unclear what procedures would be necessary to ensure the field permeability is less than 10-' cm/sec. The last paragraph of the report provides instructions for the final cover, but the instructions are based on inferences and interpolation of data from a test of materials which failed to meet requirements. The instructions should be based on the same construction materials that will be used in the final cover and which have met performance requirements. One issue that has not been resolved is the amount of each type of construction material available for the final cover. The County has not submitted sufficient data to demonstrate that there is enough silty material (ML) available to mix with the Ione clay to produce the clay barrier layer for the entire cover. Therefore, the County must submit documentation which demonstrates that there is enough ML material to construct the final cover.