Bidding on the last portion of the freeway to be completed in Casa Grande, from Midway Road to I-10, was to begin in January 1969. By November, the freeway east of Yuma was under construction, at a cost of $3.7 million (about $ in dollars). On June 15, 1970, eastbound traffic began on I-8 in Casa Grande, with an exit at both Trekell and Thorton roads, with westbound traffic soon to follow. Businesses did not notice much change with the opening of the eastbound lanes. In 1971, I-8 was nearly complete, including a new alignment east of Yuma built parallel and to the south of the original US 80 alignment. A new alignment was also built to the south of the SR 84 alignment at the eastern end of the highway from southwest of Stanfield to the eastern terminus at I-10 southeast of Casa Grande. The only portions of I-8 not completed at this time were the Gila Bend bypass and the western end near Yuma. The portion east of 16th Street in Yuma was completed in June 1972; the Arizona State Highway Commission authorized the $1.6 million (about $ in dollars) contract to construct the portion through Gila Bend in August. Some Yuma businesses had noticed a decrease in revenue at this time; the Arizona Highway Department agreed to modify some signs to eliminate any confusion. The part of I-8 between 16th and 4th streets was under construction in 1976, which was the only incomplete part of the freeway, along with the bridge over the Colorado River. The water treatment plant in Yuma was to be moved due to the potential of an accident with a vehicle carrying hazardous materials flying off the bridge and contaminating the water supply. The freeway in both states was completed with the opening of the bridge on September 20, 1978.