In the 1800s wastewater management consisted of releasing untreated wastewater directly into the Trinity River. In 1913 the Texas legislature passed an anti-pollution law that directed all cities with populations greater than 50,000 to cease discharging untreated wastewater into streams. In January 1917 Dallas completed a per day wastewater treatment plant, the Central WWTP, to comply with this law. The plant was expanded to keep up with Dallas’ growth in the 1920s. Service was expanded to Highland Park and University Park in the 1930s. In 1964 the Central WWTP was augmented with a per day Southside Oxidation Pond Facility (now called the Southside WWTP).