HYDRO31599 - Laserfiche WebLink

Home Browse Search

December 23, 1999 ~ • Puge 7 Three new alluvial monitoring wells were drilled in 1999, bringing the total to four wells ' (19-3, 21-2, 21-5, and 28-1). Three of the four existing alluvial monitoring wells (21-2, 21-5, and 28-1) will be used to monitor the water level and water quality of the Alluvial Aquifer adjacent to ' Piceance Creek. The fourth alluvial monitoring well is located downstream of the proposed location of the upper plant evaporation pond. It will be used to monitor for potential leakage from ' the pond. There are three multiple-completion monitoring wells {21-3, 21-4, and 29-4), which were ' installed in 1999. These multiple-completion monitoring wells provide nested or co-located monitoring locations for the alluvium, Uinta Formation, A-Groove, B-Groove, and Dissolution ' Surface. The multiple-completion monitoring wells were constructed in large-diameter boreholes ~ to allow a grout mixture to flow freely and fully seal the borehole between the completion zones. ' All well construction materials (sand, bentonite, and grout) were placed from the bottom of the borehole by the tremmie method. Each completion is constructed of 2-inch-diameter, PVC or ' fiberglass well casing and well screen. A diagram of a typical multiple-completion monitoring well is shown on Figure 3. Well 21-3 is located down-gradient of the first-phase mine panel and ' has four nested completion zones (Uinta, A Groove, B Groove, and Dissolution). Another well, designated as well 29~, is located up-gradient of the first-phase mine panel and has three nested ' completion zones (Uinta, A Groove, and Dissolution Surface). A separate B-Groove completion is located adjacent to the 29-4 nest (29-4B). The third multiple-completion monitoring well, t designated as well 21-4, is located inside the northeast boundary of the first-phase mine panel and is down-gradient of the assumed flow directions. Monitoring well 21-4 has three nested ' completion zones (A Groove, B Groove, and Dissolution Surface), and an adjacent Uinta well completion (21-4U). According to published and site-specific data, this layout provides for up- ' gradient, down-gradient, and cross-gradient groundwater monitoring. In addition to the three multiple-completion well locations, there are a number of single- ' completion wells at the Piceance Site. The majority of these wells were constructed to monitor the test mine phase and are incorporated into the 0-5 year commercial monitoring plan. Recent ' changes to the network of single-completion wells included re-completing 20-4 (formerly a B Groove monitoring well) as an A Groove well (now called 20-4A) and installing a new ' B Groove well (20-4B) adjacent to well 20-4A. Well 29-2, which was a Dissolution Surface 1 ' Agapito Associates, Inc.