Res 2015-012/Wastewater Master Plan

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Wastewater Master Plan Executive Summary City of San Marcos 5.0 WASTEWATER FLOW MONITORING FNI retained ADS Environmental Services (ADS) to conduct flow monitoring at selected points in the existing wastewater system. Evaluating the results of the temporary flow monitoring allow for the characterization of dry weather and wet weather flows within the wastewater system, the ranking of relative severity of observed infiltration and inflow, and the evaluation of key performance indicators to direct subsequent condition assessment and rehabilitation activities. The flow monitoring data was also used in the hydraulic model calibration. Based on the data gathered using 20 temporary flow monitors and two temporary rain gauges from April 13 to June 19, 2012, a detailed analysis of dry weather and wet weather periods was performed and is summarized below: • High dry weather flow depth -to- diameter (d /D) ratios were observed at Sites SM08, SM09, SM16A, and B &N -3 during the study period. • Two locations were defined as Non - Cleansing sewers resulting in silt buildup which was observed during the flow monitoring period: Sites SM04 and SM16A. Silt was also observed during portions of the monitoring period at Sites SM04, SM09, and SM17. The wastewater mains at these locations should be inspected periodically to determine if sewer cleaning is needed. • Wet weather peaking factors greater than 10.00 were observed at Sites SM12 and SM13A. Flow increases occur quickly during wet weather events, but also return to normal quickly. This behavior suggest the presence of inflow sources. Wet weather d/D ratios greater than 100% were observed at 14 locations, including Sites SM03, SM04, SM06, SM07, SM08, SM09, SM10, SM11, SM12, SM14, SM16A, B &N -1, B &N -2, and B &N -3. Many of these locations measured only modest amounts of RDII during storm events, suggesting that (1) hydraulic bottlenecks may exist downstream from these areas, and (2) additional RDII may be observed once these bottlenecks are alleviated. • Three flow monitor basins — SM04, SM06, and SM07 — had normalized net RDII greater than 8 gal /LF for a projected 2.00 -inch storm event. Condition assessment activities, including manhole inspections, smoke testing, and CCTV inspection are recommended to identify individual sources of inflow and infiltration. Consideration should also be given to flow monitor basins SM10 and SM14. These areas exhibit extended recoveries following the last two storm events observed ES -3