Vertical barriers for the hydraulic control of groundwater

The hydraulic control of a plume of contaminated groundwater is commonly achieved through the use of pumping wells. A pumping well creates a capture zone that helps to isolate contaminants from uncontaminated areas of the aquifer. A vertical barrier wall is often used in conjunction with groundwater extraction wells to provide hydraulic containment at significantly lower pumping rates than can be achieved without a barrier wall.;An analytical model describing the local flow field due to wells operating near an impermeable barrier wall is developed. The model is used to investigate the effect of an open barrier wall on the groundwater flow field, and to determine its effectiveness in decreasing the discharge rates required to control a contaminant plume. The range of aquifer parameters over which the solution is applicable is also determined.;The analytical solution is developed by application of conformal mapping, the method of images, and the analytic element technique. A new analytic element is developed to obtain the solution. The element is an arc-shaped doublet with a constant normal component of flow. The model is formulated in terms of the discharge potential and the discharge vector and is applicable to confined and unconfined aquifers. The model includes steady-state groundwater flow, a vertical barrier wall, pumping wells, a uniform regional flow, and a uniform recharge.;The model is used as a tool for the hydraulic analysis of barrier-well systems to obtain information useful in groundwater modeling and engineering design. Criteria are developed for quantifying the effectiveness of a barrier wall at reducing the discharge required to control a contaminant plume. A parametric study and dimensionless charts are developed that display the shapes and sizes of capture zone envelopes and isochrones generated by a combination of an open vertical barrier wall and a discharge well over a range of aquifer and barrier wall parameters. Capture zones are delineated analytically for the case of no recharge, while particle tracking is used to delineate capture zone envelopes and travel time isochrones for cases with recharge. The examples and charts are analyzed to obtain guidelines for choosing a good barrier-well setting for hydraulic containment when significant recharge is presented. The charts are appropriate for use as a screening tool in preliminary design and cost estimating of remedial systems.