Design, Installation, and Uses of Combination Ground Water and Gas Sampling Wells

Abstract

Waste disposal sites with volatile organic compounds (VOCs) frequently contain contaminants that are present in both the ground water and vadose zone. Vertical sampling is useful where transport of VOCs in the vadose zone may effect ground water and where steep vertical gradients in chemical concentrations are anticipated. Designs for combination ground water and gas sampling wells place the tubing inside the casing with the sample port penetrating the casing for sampling. This physically interferes with pump or sampler placement. This paper describes a well design that combines a ground water well with gas sampling ports by attaching the gas sampling tubing and ports to the exterior of the casing. Placement of the tubing on the exterior of the casing allows exact definition of gas port depth, reduces physical interference between the various monitoring equipment, and allows simultaneous remediation and monitoring in a single well. The usefulness and versatility of this design was demonstrated at the Idaho National Engineering and Environmental Laboratory (INEEL) with the installation of seven wells with 53 gas ports, in a geologic formation consisting of deep basalt with sedimentary interbeds at depths from 7.2 to 178 m below land surface. The INEEL combination well design is easy to construct, install, and operate.

Versatile direct push profiler for the investigation of volatile compounds near the water table

“…When collecting vadose zone gas samples the profiler operation is essentially a peristaltic pump drawing on an open tube terminated at the sampling depth. This is an established method of collecting vadose zone gas samples for a variety of volatile components [ Hult and Grabbe , 1988; Hubbell et al , 1998; Chaplin et al , 2002; Amos et al , 2005]. This is a fairly fail‐safe method with little potential for alteration of the samples.…”

“…Geochemical investigations involving volatile components are not limited to the groundwater zone. At many sites vapor phase contaminants are present in the vadose zone, above the contaminated groundwater, making it desirable to sample vertically through the vadose zone and into the saturated zone to investigate transport processes across the water table [ Forbes et al , 1993; Hubbell et al , 1998; Amos et al , 2005]. Furthermore, the immediate area near the water table is a particularly interesting area for investigation because of the sharp geochemical gradients and potential for enhanced reactivity in this zone [ Sinke et al , 1998; Groffman and Crossey , 1999; Williams and Oostrom , 2000; Amos and Mayer , 2006].…”

Well Design to Reduce Barometric Pressure Effects on Water Level Data in Unconfined Aquifers

“…observation well was screened across the water table from 179.9 to 185.3 m bls, adjacent to basalt. Above the water table, four vapor extraction ports were added to the outside of the casing for monitoring the basalt (Hubbell et al, 1998). The borehole was packed with coarse sand (2–5 mm diameter) over intervals adjacent to the screen and the vapor ports, with the remainder of the annular space sealed using bentonite and neat cement (Fig.…”

“…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).…”