This is an assumption that we recognize is not true over periods of time greater than a few months. In this module we assume that the wells G and H have been pumping together for a long enough time that the water table is stationary and flow is steady state. Under transient conditions, water levels at any location in the flow system change with time, which causes hydraulic gradients, flow velocities, and the amount of groundwater in storage (water levels) to change with time. Under steady-state conditions, water levels at any location in the flow system do not change with time, which results in hydraulic gradients and flow velocities at any location not changing with time, and therein no net change in the amount of groundwater in storage. These dynamic changes in water levels result in the groundwater flow system being transient in character - as opposed to being steady state in character. As a result of changes in the pumping rates of wells G and H and their periodic (discontinuous) use, the water table in the buried valley aquifer was dynamic, rising and falling as wells G and H were turned on and off and pumped heavily or lightly. However, pumping records kept by the City of Woburn showed that between 19 the wells rarely operated together and that the two municipal wells were frequently not in use for months at a time. During the 30-day pumping test, wells G and H operated at their average rates of 700 gpm (well G) and 400 gpm (well H). It was also the first time synoptic sets of water levels had ever been measured in the network of monitoring wells surrounding wells G and H. Geological Survey in December 1985 through early January 1986 was the first time wells G and H operated since their closure in May 1979. The 30-day pumping test performed by the U.S. Thus, the interaction of these three wells with the Aberjona River and the groundwater flow system was critical to determining which of the contaminated properties contributed TCE and PCE to wells G and H. If the water table was not drawn down on the west side of the river when wells G and H operated, then it is unlikely that contaminants on the west side of the river valley could flow to wells G and H. If, when wells G and/or H operated, the water table was drawn down on the west side of the Aberjona River, then contaminants from west side of the river valley (Beatrice 15 acres and Olympia Trucking) could flow under the river to wells G and H. One of the important questions raised during the trial centered on the drawdown of the water table when wells G and H were operating and the effects of the Riley tannery well. Let students discover the role of the Aberjona River as a potential source of water to wells G and H, and the role of the bedrock valley walls in limiting groundwater flow to wells G and H and shapes of their cones of depression.Provide students with an overview of groundwater flow wells, formation of a cone of depression, superposition of multiple cones of depression, and creation of groundwater flow divides between wells.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |