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Fig. 3. Stratigraphy and well completion for Well USGS-118, which was used to evaluate the isobaric technique. The 5-cm casing was slotted with 1-mm saw cuts over the screened interval, and four vapor ports were added to the outside of the casing. Vapor ports were fabricated from lengths of 9.5-mm-diam. tubing. The bottom of each tube was crimped to prevent backfill from entering, and the next 1.5 m was perforated with 2-mm-diam. holes. Individual vapor ports were attached to the outside of the casing, then routed to the surface. The annular region was backfilled with coarse sand around the screened interval and vapor ports, the remainder of the borehole was sealed with bentonite and neat cement (Hubbell et al., 1998).
