A Holistic CSO LTCP – Balancing WWTP, MS4 and CSO to Maximize Water Quality Benefits: Part 1

The City of Lynchburg, Virginia's current Combined Sewer Overflow (CSO) Long-Term Control Plan (LTCP) recommends complete separation of the entire combined sewer system. Separation of the remaining combined areas which are mostly in increasingly urban areas, including the historic Central Business District, is challenging and expensive. The development of local bacteria Total Maximum Daily Load (TMDL) and the Chesapeake Bay nutrient TMDLs have also shown a spotlight on the City's CSO Program, as sewer separation influences the waste load allocations for both wastewater treatment plant (WWTP) and stormwater. As a result, the City initiated a CSO LTCP update study to ensure that future expenditures provide the maximum benefit to the City and to the water quality. In fall 2009, the City launched a comprehensive rainfall and flow monitoring program and a water quality sampling program to collect data for the LTCP update study. A sophisticated hydrologic and hydraulic model and receiving water quality models have been constructed and are currently being calibrated and validated using the data collected. The modeling tools will be used to evaluate the CSO control alternatives for the LTCP update study. This “Part 1” paper will summarize the findings of the data collection and modeling process. The LTCP update (Part 2) is expected to be completed in early 2012