Salt contaminations for the coastal confined groundwater in Chiba City have been considered on the basis of the results of investigation made on August 1974. The conclusions obtained may be summarized as follows:
1. Although local, yet groundwater contaminations with salt water are recognized at the adjacent area of the mouth of River Miyako.
2. It seens that the salt contamination is mainly induced by the direct intrusion of sea water into an aquifer originated in a disparity of the amount between recharge and pumpage.
3. The chloride ion concentration of contaminated groundwater keeps up increasing from the year around 1965, and the area with relatively high concentration of chloride has enlarged its extent landwards year by year.