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Wastewater Master Plan Executive Summary <br />City of San Marcos <br />3.0 DESCIPTION OF THE EXISTING WASTEWATER SYSTEM <br />The City of San Marcos's wastewater collection system consists of a network of 219 miles of collector <br />mains, interceptors and force mains, 40 lift stations, and a wastewater treatment plant along the San <br />Marcos River. The plant has a current permitted capacity of 9.0 MGD average annual daily flow (AADF) <br />and 31.0 MGD peak 2 -hour flow (P2HF). Lift stations are necessary when wastewater needs to be pumped <br />to a higher elevation where the flow can resume flowing by gravity to the outfall of the system. Due to <br />the varying topography, San Marcos operates 40 lift stations and 27 miles of force main throughout the <br />service area. <br />4.0 LIFT STATION RISK BASED ASSESSMENT <br />A risk based assessment was performed on all of the City's 40 lift stations to develop a prioritized list of <br />maintenance and improvement projects. A risk based assessment consists of a condition assessment and <br />a criticality assessment. The condition assessment included a visual inspection of each lift station. The <br />criticality, or consequence of failure, assessment included an analysis of the proximity of each lift station <br />to critical areas, as well as the residential population served. Each lift station was assigned a condition <br />and criticality score based on the results on the assessments. The condition and criticality scores were <br />used to assign a risk category (high, medium, or low) to each asset. Lift station rehabilitation projects <br />were developed based on the results of the risk based assessment and included in the wastewater capital <br />improvement plan. The risk rating of each lift station is shown in Table ES -2. <br />Table ES -2: Lift Station Risk Rating Matrix <br />ES -2 <br />