In 1936 the city decided to develop a plan for sewerage improvements because at the time the city's raw sewage poured directly into the Sandusky River. The study done by H.P. Jones and Company came to the conclusion the city needed to build a primary treatment plant. Not until 1955, however, were the recommendations followed and a primary treatment plant built. In 1964 the city realized it needed more thorough treatment of the sewage so it retained Floyd G Browne and Associates to study the problem. They determined the plant needed to add secondary wastewater treatment facilities and sludge filtration. At the time of this addition to the plant, the estimated population was 40,000 people by the year 1990. In 1988 the city added a third digester to the sludge treatment and a chlorine building to house the cylinders of chlorine that are used to disinfect the water before it is discharged into the Sandusky River. The last upgrade was started in 2015 which included new mechanical bar screens and upgrading the aeration tanks with fine bubble diffusers and adding anoxic zones to help with nutrient removal. In 2017 the city reached an agreement with the Ohio EPA on its new Long Term Control Plan which includes in it upgrading the wastewater treatment plant to be capable of handling flows up to 13MGD by adding another larger 80’ diameter secondary clarifier and a 13 million gallon equalization basin to help eliminate combined sewer overflow activations which dump raw sewage into the Sandusky River.