CSPE Geomembranes for Potable Water & Floating Covers

Installation is carried out to the project CQA plan, referencing GRI GM28, Specification for Test Methods, Test Properties and Testing Frequencies for Reinforced Chlorosulfonated Polyethylene (CSPE-R) Geomembranes. For potable water reservoirs and floating covers, work is additionally governed by ANSI/AWWA D130-11 (R19), Geomembrane Materials for Potable Water Applications, which sets minimum requirements for materials, fabrication, installation and quality assurance, with AWWA Manual M25, Flexible-Membrane Covers and Linings for Potable-Water Reservoirs, as the supporting design and installation reference. Where the project specification conflicts with these documents, the project specification governs and the conflict is raised in writing before deployment.

Subgrade is proof-rolled and formally accepted in writing by the installer before any panel is unrolled. The surface must be free of stones, roots, sharp protrusions, standing water and desiccation cracks exceeding the limits set in the project specification, and anchor trenches must be excavated to profile and free of loose spoil. Panels are deployed from factory rolls in the sequence shown on the approved panel layout drawing, positioned to keep seams running up and down slopes rather than across them, and temporarily ballasted against wind uplift from the moment of deployment until permanent anchorage is complete.

CSPE requires a seaming approach that no polyolefin liner does. The material is manufactured as a thermoplastic but cross-links over time into a thermoset, so newly manufactured sheet can be thermally wedge welded, while cured or aged material must be joined using bodied solvent or contact adhesive systems supplied for the purpose. This governs sequencing: field seams are made while the sheet is still weldable, and any repair, tie-in or extension to previously installed CSPE is treated as an adhesive-bonded seam with the appropriate surface preparation, primer and cure time. Panels are overlapped in accordance with the manufacturer's fabrication instructions, and seaming is suspended outside the ambient temperature and moisture conditions permitted by the CQA plan.

Trial seams are produced on offcut material at the start of each shift, after any break of more than the interval stated in the CQA plan, and following any change of equipment, operator or ambient conditions. Each trial seam is tested before production welding resumes. Destructive seam samples are taken at intervals selected in accordance with GRI GM14, Guide for Selecting Variable Intervals for Taking Geomembrane Destructive Seam Samples Using the Method of Attributes, or GRI GM20 where control charts are specified. Seam shear is evaluated to ASTM D751 in its modified form, consistent with the bonded seam strength property on the manufacturer's data sheet, and ply adhesion to ASTM D413 or ASTM D6636 per GRI GM15. Note that GRI GM19a and GM19b apply to polyolefin geomembranes and do not govern CSPE seams; specifications that cite GM19 for a CSPE liner contain an error worth resolving before award.

All production seams are subject to non-destructive testing across their full length, with methods and acceptance criteria recorded in the CQA plan and evaluated in accordance with GRI GM29, Practice for Field Integrity Evaluation of Geomembrane Seams (and Sheet) Using Destructive and/or Nondestructive Testing. Dual-track seams with an air channel are pressure tested to ASTM D5820. Single-track seams, extrusion welds, patches, penetrations and detail work are vacuum box tested to ASTM D5641, air lance tested to ASTM D4437 or spark tested to ASTM D6365 as appropriate to the detail. Where the specification calls for post-installation leak location, method selection follows ASTM D6747 and exposed-liner surveys are carried out to ASTM D7002.

On completion, penetrations, batten bars, cushion strips and perimeter anchorage are inspected and signed off against the approved details. For potable installations, the reservoir is cleaned and disinfected in accordance with AWWA C652, Disinfection of Water-Storage Facilities, before return to service. The handover package issued to the client comprises mill certificates traceable to the supplied rolls, the subgrade acceptance record, the as-built panel layout, all trial seam, destructive and non-destructive test results, welder and equipment calibration records, the repair register, and the final QA/QC sign-off certificate that starts the warranty period.