1990 Interstate 75 fog disaster

The stretch of I-75 where the collision occurred consists of an approximately section in Bradley and McMinn counties between mileposts 29 and 39 that is prone to dense fog, which often appears rapidly. It is located about northeast of Chattanooga and southwest of Knoxville. The stretch is located within two separate valleys bounded by ridges within the Ridge and Valley Appalachians and is bisected by the Hiwassee River, which forms the boundaries between the two counties. Multiple creeks that span both the valleys that the Interstate is in and adjacent valleys flow into the Hiwassee River near where the Interstate crosses. The Chickamauga Dam, located downstream from this section of the Hiwassee on the Tennessee River, creates a reservoir which backs up into this section of the Hiwassee River, and as a result creates large lakes near the Interstate where creeks run into the Hiwassee. The Hiwassee River bridges are at one of the lowest elevations on I-75 in Tennessee. A paper mill operated by Resolute Forest Products, formerly Bowater, is located on the north bank of the Hiwassee about east of the Interstate in Calhoun. The plant operates wastewater treatment settling ponds adjacent to the Interstate and owns land on both sides of the Interstate at the accident site. All of these factors have been provided as explanations for why fog is unusually common in this area. The first multi-vehicle collision during heavy fog on this section occurred on March 9, 1974. This collision involved 18 vehicles, and resulted in three deaths and 10 injuries. The final multi-vehicle collision along this stretch before the 1990 collision occurred on April 15, 1979. As a result of the 1979 pileup, the Tennessee Department of Transportation (TDOT) installed dual warning signs the following year which read "Extreme Dense Fog Area Next 5 Miles" along this stretch in each direction, which contained flashing lights that would activate if fog was detected. The northbound sign's lights were reportedly not working on this day, and the southbound sign's lights had been flashing continuously for the past three days, which was believed to have caused some motorists to ignore them. ==Collision and response==

The collisions began on December 11, 1990, around 9:10 a.m. Eastern Time when a tractor-semitrailer slowed in the southbound lanes of I-75 near the State Route 163 (SR 163) interchange (exit 36) in McMinn County less than north of the Hiwassee River Bridges. The crash site extended north and south of where the crash began. Of the 99 vehicles involved in the crash, 72 had been traveling in the southbound lanes, and 27 in the northbound lanes. Many of the vehicles involved in the collision were damaged or burned beyond recognition, while others received only minor damage. He immediately radioed for back up and emergency medical services. He also sent out a plea for the Interstate to be closed. Within minutes, additional law enforcement and EMS personnel from multiple agencies arrived on the scene. More than 200 rescue personnel, some from as far away as Chattanooga and Knoxville, eventually arrived on the scene. Injured victims from the crash were taken to hospitals in nearby Cleveland and Athens, as well as in Chattanooga and Knoxville. A team of investigators from the NTSB later arrived to investigate the cause of the disaster. ==Investigation==

Multiple survivors described the fog as rapidly appearing, with one survivor stating "it was like somebody throwing a blanket across your windshield". Initial reports stated that at least 15 people were killed and more than 50 injured, but investigators later determined that 12 people had been killed and 42 people treated for injuries. ==Aftermath==

Bowater denied any responsibility for the fog that formed on the day of the collision, and instead claimed that dense fog had been a natural occurrence even before the plant had been constructed. They also agreed to limit the usage of the pond closest to the Interstate. The stretch of I-75 between mileposts 31 and 39 was designated as a "fog advisory zone" or "fog advisory area", which contains large warning signs on both sides of the road in both directions that warn motorists when they are entering and leaving the area. The swing gates at the entrance ramps activate when visibility drops below . and in 2006, a $6.6 million (equivalent to $ in ) upgrade was completed which installed the video cameras. ==In popular culture==

The collision was the subject of a 1997 Forensic Files episode titled "Killer Fog". A chapter about the event is included in the 2012 book Tennessee Tragedies: Natural, Technological, and Societal Disasters in the Volunteer State, written by former TEMA official Allen R. Coggins. The first chapter in author Dewaine A. Speaks' 2019 book Historic Disasters of East Tennessee chronicles the event. ==References==