Wells most likely to be vulnerable to bacterial contamination after flooding are shallow, have been dug or bored or have been submerged by flood water for long periods of time.
(Wells most likely; to be; vulnerable to bacterial contamination) (Wells most likely to be vulnerable to bacterial contamination; are; shallow; T:after flooding)
Wells most likely Wells most likely to be vulnerable to bacterial contamination
to be are
vulnerable to bacterial contamination
shallow T:after flooding