The investigation of the geology of the River Orwell downstream of Ipswich was carried out by the Department of Transport in the period 1973 to 1978. A buried valley in the surface of the Upper Chalk was identified and defined. The depth of the valley is 45 m below sea level and very soft chalk occurs adjacent to the valley.
The methods used to sample and classify the chalk for engineering foundation design purposes are presented. The infill material to the valley is described and the influence of the valley upon the chalk is indicated.