Due to high growth in the area, the City of Midlothian’s 0.9 MGD wastewater treatment facility is operating at approximately 90% rated capacity. The City contracted with the Wallace Group in 1999 to prepare a study on treatment alternatives. Recommendations included expanding the treatment capacity to the existing facility by 2.0 MGD.

At that time, the City of Grand Prairie expressed a desire for Midlothian to treat 1.0 MGD of wastewater from the southern portion of the City lying in Ellis County. In a cooperative effort the City of Midlothian and the City of Grand Prairie contracted with the Trinity River Authority (TRA) to construct a regional wastewater treatment plant for the two cities. The agreement includes the TRA taking ownership of the existing 0.9 MGD wastewater treatment plant.

The TRA contracted with the Wallace Group to design a 3.0 MGD treatment facility to work in connection with the existing 0.9 MGD treatment facility. Designated as the Mountain Creek Regional Wastewater Treatment Facility, this facility will serve southern Dallas and northern Ellis counties, including Midlothian and Grand Prairie. The facility is designed for future expansion to a 9.0 MGD plant to handle flows from additional entities and growth in the area.

The new Mountain Creek Regional WWTP is designed to treat 3.0 MGD at 10 BOD5, 15 TSS, 2NH4-N, and 4 D.O. The facility will have fine screening, extended aeration, aerobic digestion belt press, and UV disinfection. Besides the WWTP, this joint effort has produced one new lift station and force main that will serve both cities and the purchase of 68 acres of land immediately adjacent to Midlothian’s 0.9 MGD wastewater plant where the new plant will be located.

All of these assets, plus other existing lift stations and force mains, will be assigned to the new regional wastewater system. TRA assumed operation control of the systems’ pipeline, pump stations, and wastewater treatment plant when the new plant went on line.

Author: Bob Wallace, P.E.