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Mr. Ross Atkinson September 3, 2002 Interim Construction Certification Letter,WMU-D02 Construction Page 3 or technician was allowed to begin work unless a start-up weld was conducted and approved by Vector's CQA Monitor. HDPE panels were seamed in the field using double fusion wedge and extrusion welding techniques by the Contractor. The majority of seams were joined using double-wedge welders, with difficult geometries and repairs made using extrusion welders. Vector's CQA Monitor observed all of the seaming activities and observed for proper panel overlap, cleanliness of the seams, grinding where required, and the speed and weld temperatures of the equipment used. Seam continuity was tested by the Contractor using the air pressure method for the double wedge welded seams and the vacuum box method for extruded seams. Vector's Monitor observed the seam continuity testing performed by the Contractor and maintained documentation of this procedure. This documentation included recording the seam number, QC technician, test type, number of repairs and their locations, dates of repairs and retests, and the CQA Monitor observing the testing. In addition to nondestructive quality control, destructive samples were obtained at random intervals of approximately one sample per 500 linear feet of seam as determined and located by the Vector CQA Monitor. A sample at least 12 inches wide by 46 inches long was cut by the Contractor and provided to Vector for determination of bonded seam strength in shear and peel according to ASTM D-6392. All final field seams tested met the requirements of the specifications for shear and peel strength. After the 60-mil HDPE geomembrane was installed and accepted, HDPE pipe and granular material were placed on the floor as the LCRS system along with geotextile and 12-inches of the protective soil layer material. Vectors CQA Monitor carefully observed the placement of the materials to ensure that the underlying geomembrane was not damaged. Based on our observations, testing, and review of project data, it is Vector's opinion that waste placement can begin within WMU -02. A final CQA documentation report is presently being prepared and will be submitted to you within 30 days of completion. If you have any questions or require additional information, please do not hesitate to call me at (530) 272-2448. Regards, . VECTOR EN EERIN /NC. Bryan AFritzler, P. RCE 055568 3 •31�oq Director of Technical Services 10 cc. Butch Stefani — Forward Inc. Lochlin Caffey—Allied Waste Inc. \\Vector-gv\Projects\Forward\021605.00-Fwd WMU D02 CQA\Certification Letter.doc ECL O l ENGINEERING,INC.