How to lower groundwater table?Learning issue Installation of PVD can lower groundwater table. In order to remove water content by installing PVD, preloading or surcharge is needed to fasten the process of removing water content in the soil. Without preloading or surcharge process can take years or decades. PVD can reduce the pre-loading time from several years to a few months; they are intended to expedite settlement rather than reduce it. Dewatering. Dewatering can control groundwater by pumping, to locally lower groundwater levels in the vicinity of the excavation. Groundwater is allowed to enter the excavation where it is then collected in a sump and pumped away by robust solids handling pumps. Sump pumping can be effective in many circumstances, but seepage into the excavation can create the risk of instability and other construction problems. To prevent significant groundwater seepage into the excavation and to ensure stability of excavation side slopes and base it may be necessary to lower groundwater levels in advance of excavation. This is known as pre-drainage.Pre-drainage methods include: Deep wells Wellpoints Eductors Vacuum wells Horizontal wellsOther specialist dewatering techniques are also sometimes used: Relief wells Artificial recharge Siphon drains

Reference Prefabricated Vertical DrainsThe Squeeze Is On ; By Martin G. Taube, P.E., M.ASCE http://www.wjgl.com/dewatering