Abstract
Most of groundwater in Japan is found in the multi-layered aquifer of Quaternary sediments. It is, therefore, necessary to make drilling of several observation wells in order to determine the essential hydrauric properties of groundwater in each aquifer.
We report here a new pumping method and its equipment of multi-layered groundwater by using a single observation well. This method is divided into the following three steps based on operating proceess.
1) Investigation by using a test boring : (a) identification of sub surface geological features. (b) determination of depth and thickness of each aquifer. (c) making a geological columnar section.
2) Drilling of an observation well and installation of a strainer pipe unit : (a) enlargement of the test boring from 66mm to 115 in diameter. (b) installation of the strainer pipe unit into the observation well. (c) drainage of the strainer pipe unit.
3) Pumpage of groundwater in each aquifer with a water-sampler unit (a) insert of the water-sampler unit into the strainer pipe unit. (b) pumping of groundwater and testing of water quality
The pumping method was tested at Mituhasi area, Fukuoka Pref. The sediments in this area are composed mainly of unconsolidated clay, sand, and gravel beds of Holocene age, and four aquifers has been confirmed by a single observation well. From the results obtained, it has been made clear that this method is the most effective pumping procedure.
