NEW CASTLE, Del. (AP) — Delaware's largest residential water supplier says it has shut down a well near New Castle after high levels of a toxic chemical were detected. The News-Journal of Wilmington (http://delonline.us/UlL5Bw ) reported Tuesday that state public health regulators posted a notice in mid-June of an elevated level of perfluorooctane sulfonate (PER'-floor-oh-ok-tayne SUL'-fan-ayt) in the Wilmington Manor supply well owned by Artesian Water.