It could have been much worse, but the combination of an effective emergency response plan and what can only be called acts of God prevented an environmental nightmare when a tanker truck carrying a toxic chemical overturned on Union Avenue Wednesday afternoon.

The tanker was traveling down Union Avenue toward the North Boroughs about 3 p.m. when the driver attempted to turn onto the I-279 southbound on-ramp. Officials believe several tires hit a rut beside the ramp, the driver overcompensated, and the tanker flipped.

The tanker was carrying sodium hydrosulfide, a chemical used for pollution control in water removed from mines. Although the substance is not lethal to people, it can be an irritant and produces a noxious odor.

A break in the tank allowed a small amount of the substance to leak out. Officials said that the tank was leaking about one quart to one gallon of the chemical per hour at its worst.

Although about 50 homes in the area were evacuated, along with the Avalon swimming pool and park, Northgate High School and several businesses along Union Avenue, the major threat to the area came from the proximity of the leak to the Spruce Run Creek.

Avalon borough manager Harry Dilmore said that because the chemical reacts strongly with water, county emergency hazardous materials teams immediately took steps to prevent or limit the chemical from reaching the creek. This included setting up dams along the creek, and constant monitoring of the water in the stream at various points.

Water also comes in the form of rain, however, and officials monitored weather reports that had rain falling as close as Franklin Park. Dilmore said that the county brought in a tent to cover the tanker in case of rain. Fortunately, the rainfall held off.

The effort to protect the creek also was helped by the fact that the tanker was located on the good end of a slope and at least some distance from the creek, Dilmore said. The ground in the area around the truck will have to be excavated in the coming days, he said.

Officials hesitated to lift the tanker onto its wheels, fearing stress might cause other areas to break. Emergency personnel waited while a truck was brought in from Clarion and the chemical inside the tanker could be transferred. That occurred by about 7:30 p.m., and the tanker itself was removed by about 10:30 p.m.

About 32 people evacuated from their homes went to the Avalon borough hall, Dilmore said, while most went to the Quaill fire hall. Spencer and Friends set up an area in the borough hall for people with pets. Area restaurants donated food and beverages, Dilmore said.

The Avalon borough hall became the headquarters for the emergency response teams from the county. Dilmore said the administrative office provided the telephones and office equipment county officials needed, while the emergency manager’s office was equipped with a radio system designed for use in just such an instance.

The hall was a bit crowded, Dilmore said, because officials opted not to use Avalon’s back-up emergency center -- Greenstone Church -- because the building is not air conditioned.

Dilmore said that the evacuation of the swimming pool and park went smoothly, and the boroughs firetrucks and some public works vehicles were moved to California Avenue because personnel was not permitted in the area of the fire hall/street department building on New Brighton Road.

“It worked well,” Dilmore said of the borough’s emergency response plan. “I was proud of everybody.”