Here's Cryptome's archive of the Department of Homeland Security's morning brief for October through January. Examples of infrastructure related activity:
New Hampshire. According to ConEd Energy security personnel, on 16 October, at the Newington Power Plant, a ConEd employee observed two white males in a parked vehicle near the Plant fence line. Reportedly, the vehicle’s passenger was taking photographs of the Plant using a telephoto lens. The area being photographed included Anhydrous Ammonia storage tanks and the loading dock area.
Louisiana. According to the Shell Chemical Company, on 13 October, in Geismar, Shell Chemical security personnel observed two males taking photographs of the Shell Chemical facilities including the electrical grid and chemical tanker trucks. The security personnel contacted local authorities who responded to question the individuals. Their investigation revealed that both individuals—one Asian and one Caucasian—were British citizens with valid U.S. visas who stated they were on a one month vacation and were fascinated by chemical plants. They were driving a rental car with Florida tags which they had rented in New York. The Asian male had several visa stamps in his passport for countries in the Middle East. Reportedly, in their possession, they carried several newspaper clippings related to the 9/11 attacks.
Wisconson. According to USCG reporting, on 11 October, at the Port of Milwaukee, a petroleum storage tank facility employee observed an unidentified male photographing the area with a large telephoto lens. The unidentified male photographed two neighboring petroleum facilities and the railroad tracks adjacent to both facilities. The employee attempted to confront the male and when the male noticed him approaching, he returned to his vehicle and departed the area.
UTAH. According to Chicago Police Department reporting, silhouettes of machine guns have been stenciled on electrical boxes in Iowa and Utah (pictured below).
Texas. According to reporting from the Texas Department of Public Safety, on 16 November, at the water treatment plant in Itasca, an unidentified individual broke into the water treatment plant and increased the chlorine input in the water—making the water poisonous.
Michigan. According to USCG reporting, on 10 November, in Detroit, while performing a training dive, Detroit Police Department (DPD) divers found a second improvised explosive device (IED) in the Rouge River. On 3 November, DPD divers found the first IED near a water in-take valve, approximately one-half mile from a waste water treatment plant. The DPD divers found the second IED in the same location as the first; however, the second IED was much smaller.