CORRESPONDENCE_1992-1993 - Laserfiche WebLink

Home Browse Search

Mr. Horton Page 5 A mixing table offers a greater opportunity for successful cap construction. The mixing table would allow for better blending of various native soil types and homogenization of the soil and clay mixture. Better moisture control and more absorption time can also be provided on the mixing table. Once the soil is properly mixed and moisture conditioned, the material is delivered to the construction area ready to compact. Lift thickness can be adjusted to fit the compactor' s ability rather than the rotor-tiller's requirements. Better overall CQA control can be achieved because the admixture can be tested in batches before it is delivered to the cap area. CQA Testing Methods and Frequencies - The enclosed checklist shows recommended test frequencies and criteria for clay layer construction programs. The checklist also shows the frequencies and criteria specified by Kleinfelder for the Harney Lane cap project. The proposed frequencies and criteria which the Regional Water Board considers significantly different are shown in bold type. The Regional Water Board staff recognize that not all projects will have the same CQA test frequencies, but the frequencies and parameters shown have been used in numerous, successful construction projects. Borrow material evaluation testing will need to be adjusted to accommodate the requirements of the mixing process. The Regionial Water Board request that Tables 7-1 through 7-4 be revised to provide the test method, absolute frequency, in terms of cubic yards of material or tests per acre per lift (and not relative to another test method) and acceptance criteria on a single page. For example, Table 7-2 specifies lift thickness (distinct from "layer thickness") as a required observation, but Table 7-4 omits lift thickness. In addition, the admixed soil needs to be classified in the CL, CH or SC range with a minimum of 30% passing the No. 200 sieve, in addition to the various criteria shown in Table 7-4 . The revised tables should specify which tests, with associated frequencies and criteria, will be performed on native soil, the admixture and the final compacted cap. Testing frequencies should be increased to meet the recommended frequencies or Kleinfelder should explain why they are not increased. Final Construction Certification - The Regional Water Board needs to be assured that the Engineer of Record is capable and qualified to certify the completed cap pursuant to 23 CCR 2540 (e) , General Construction Criteria. Resumes included in Appendix B do not indicate that certifying personnel have ever had any experience in the construction of low permeability clay liners. 3 . 14 CCR 17781 - Leachate Control and Monitoring During Closure and Postclosure. Again, Board staff requests the operator to address the minimum requirements for leachate monitoring and control. The operator must monitor for