The Technical Guidance Document is meant to augment the numerous construction quality control and construction quality assurance (CQC and CQA) guidelines that are presently available for geomembrane installation and inspection. It is focused on all current methods of producing geomembrane seams including HDPE and VLDPE, PVC, PVC-R, CSPE, CSPE-R, CPE, CPE-R, EIA and EIA-R. In general, the tone of most of the existing guidelines is to allow the installer almost complete freedom in making seams with the only conditions being that they pass: (1) destructive shear and peel tests to a stipulated strength, and (2) selected nondestructive tests. By developing a report somewhere between the typical CQC/CQA Documents and an installer's training manual, i.e., a 'Technical Guidance Document', it is hoped that this technical guidance document will provide meaningful insight for an inspector as to what the installer is trying to accomplish. At the same time, it might be also helpful to the installer in recognizing that others have an interest in their specific activity. After some introductory material, the manual presents six specific methods used for fabricating field seams of the types of geomembranes being most widely used for environmental control systems. They are the following: (1) extrusion fillet seams, (2) extrusion flat seams, (3) hot wedge seams, (4) hot air seams, (5) chemical fusion seams, and (6) adhesive seams.