City of Morgan Hill Sewer System Master Plan 2017

City of Morgan Hill Sanitary Sewer Flow Monitoring and Inflow/Infiltration Study

INTRODUCTION Scope and Purpose

V&A was retained by Akel Engineering Group to perform sanitary sewer flow monitoring and inflow and infiltration (I/I) analysis within the City of Morgan Hill, California (City). Flow monitoring was performed over a 20-day period at ten open-channel flow monitoring sites within the City. The flow monitoring period began on February 25, 2014, and ended on March 17, 2014. The purpose of this study was to measure sanitary sewer flows at the flow monitoring sites and estimate available sewer capacity and infiltration and inflow (I/I) occurring in the basins upstream from the flow monitoring sites. Flow Monitoring Sites Flow monitoring sites are the manholes where the flow monitors were placed. Flow monitoring site data may include the flows of one or many drainage basins. To isolate a flow monitoring basin, an addition or subtraction of flows may be required 2 . Capacity and flow rate information is presented on a site-by-site basis. The locations and other information for the flow monitoring sites are shown in Table 3 and illustrated in Figure 7. Flow Monitoring Basins Flow monitoring basins are localized areas of a sanitary sewer collection system upstream of a given location (often a flow meter), including all pipelines, inlets, and appurtenances. The basin refers to the ground surface area near and enclosed by the pipelines 3 . A basin may refer to the entire collection system upstream from a flow meter or may exclude separately monitored basins upstream. I/I analysis in this report will be conducted on a basin-by-basin basis. The isolated basins of this project are illustrated in Figure 8. Due to potential cross-connections between basins, the I/I results for Basins 7 and 8 are shown together, labelled “Basin 7/8”. The individual results for Basin 7 and 8 will be presented in future analyses tables as sub-headers and for informational purposes only. For this study subtraction of flows was required to isolate the drainage areas of some flow monitoring basins. Shown in Table 4 are the equations (in which Q refers to flow rate) used to calculate the flow rate results for each basin from the flow rates recorded at the monitoring sites. Detailed descriptions of the individual flow monitoring sites, including photographs, are included in Appendix A . Harding Flow Meter V&A had access to flow monitoring data from the Harding Avenue Flow Meter. This meter measures the total flow from the City of Morgan Hill through a single 21-inch transmission sewer line sewer prior to entering into the City of Gilroy collection system. Flows from this meter during the flow monitoring period are also presented in this report and used to establish system totals. 2 There is error inherent in flow monitoring. Adding and subtracting flows increases error on an additive basis. For example, if Site A has an error of ±10% and Site B has an error of ±10%, then the resulting flow when subtracting Site A from Site B would have an error of up to ±20%. 3 The basin areas (in acres) were provided by Akel Engineering Group.

12-0248 AEG CofMorganHill FM Rpt.docx

Page 10 of 46