Shower Studies at around 10^18 eV with the Surface Detector of the Pierre Auger Observatory

Three months of data taken by the Engineering Array Surface Detector of the Pierre Auger Observatory have been analyzed with the aim of setting a procedure for the study of showers at E_0 ~ 10^18 eV. We present the results, concerning: (i) the selection procedure and the check of its efficiency; (ii) the event rate and its stability; (iii) the characteristics of such events (i.e., angular direction, energy estimator S(1000), rise time vs core distance, correlation with pressure) showing their consistency with the expectations. The performances of the whole Surface Detector of the Auger Observatory are discussed.