This report covers the electrical resistance tomography (ERT) work performed at the Hanford Reservation, 200 East Area Vadose test (Sisson and Lu) site during the period March 23 through May 5, 2001. The purposes of the ERT work were to: (1) compare and contrast the development of the highly concentrated sodium thio-sulfate plume (FY01 work) with the fresh river water plume observed during FY00; (2) use the resistance images to infer the dynamics of the plume during two or three of the sodium thiosulfate releases and during the water ''chaser'' release; (3) determine the influence of the site's steel casings on the capability to construct reliable ERT images; (4) determine if the steel casings at the site can be used as long electrodes to provide useful images of at least one release; and (5) develop quantitative estimates of the noise in the data and its effect on reconstructed images.