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To identify the probe casings, the labcocks were staggered <br /> vertically to differentiate between shallow, intermediate, and deep <br /> probes. The deep probe is set the lowest, the shallow probe is set <br /> the highest, and the intermediate probe is in between. The labcock <br /> handles were also coded with colored tape to further identify the <br /> ' monitored intervals. The deep probe handle is blue, the <br /> intermediate probe handle is red, and the shallow probe handle is <br /> yellow. <br /> The gas probe wells were constructed by installing each section of <br /> slotted PVC screen in a high-permeability gravel pack separated by <br /> intervals of low-permeability bentonite. First, gravel was placed <br /> in the bottom of each boring to serve as the base for the deep gas <br /> probe. After the deep probe was installed, the annular space <br /> surrounding the screened interval was filled with 1/4-inch gravel. <br /> A 5-foot-thick seal of granular bentonite was poured over the <br /> gravel pack and hydrated with clean water. The intermediate level <br /> ' gas probe was then installed above the bentonite seal, and the well <br /> construction procedure was repeated. When the gravel pack for the <br /> shallow gas probe was completed, a bentonite seal was placed up to <br /> the ground surface. Six-inch-diameter locking steel casings were <br /> installed in concrete at the surface to house and protect the gas <br /> probes. The steel casings were painted orange so they would be <br /> visible to site operating personnel. <br /> 8 <br />