Scope

Beginning in 1995, the San Juan Field Office (SJFO) of the Bureau of Land Management has been collecting soil vapor data, at sites near the outcrop of the Fruitland Formation. At present, monitoring continues at approximately 184 sites on the Southern Ute Reservation and on 161 sites on private and public land outside the reservation.

In this preliminary report, we have applied three statistical tests for trend to the measurements of the following variables at each site:

· Methane as a percentage of Lower Explosive Limit (CH₄_LEL);

· Hydrogen sulfide (H₂S) , in parts per million (ppm);

· Oxygen(O₂) , as percentage by volume;

· Gas flow, in ml/min through 1/4" diameter soil vapor tube and 18gauge needle.

We report on those sites at which there appear to be either significant increases or significant decreases in the periods before and after July 1, 1998.