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City of Redwood City - Sewer System Modeling, Capacity Assessment, and Master Planning Draft Scope of Work Redwood Shores system and two in the Seaport Centre/Pacific Shores system) and associated piping would likely be included in the model. The SBSA Maple Street Pump Station will be treated as an "outfall" of the main system trunk sewer model. Operating data for the pump station will be obtained to develop an appropriate level hydrograph at the pump station to accurately represent the downstream hydraulic gradeline in the system. A similar methodology will be used for the outfall of the Redwood Shores system at the SBSA WWTP. Data for the modeled network will be drawn from available GIS data, sewer maps, and sewer project record drawings. Based on RMC's previous cursory review of the City's sewer system GIS, it appears that nearly 30 percent of the 10-inch and larger pipes in the City's GIS (which also contains a substantial number of County SSMD sewers) are missing invert data. Additionally, roughly 40 percent of the manholes in the GIS are missing rim elevation data. As such, portions of the model construction process will rely on record drawing investigation. A limited amount of record drawing research (approximately 40 hours) is included in this scope of work. Depending on the availability of record drawings, this effort may also need to include some field surveying. Field surveying and any additional data collection work are considered to be an optional task. Following the construction of the model database, a QA/QC process called "model validation" will be used to verify the data before beginning any model runs. The validation process includes checking network connectivity and data completeness and reasonableness for apparent discrepancies, e.g., negative pipe slopes, outlet pipe invert elevations higher than inlet invert elevations, etc. Subtask 5.2 - Delineate and Populate Subbasins and Loadings RMC will delineate loading areas (called "subbasins") and assign the flows in the system to network nodes. City staff has already delineated the major system basins, which will serve as the basis for further subdivision of the system into smaller subbasins. Loading data developed under Task 3 will be aggregated by subbasin for loading into the model network. Subtask 5.3 - Calibrate Model Calibration is a process by which modeled flows are compared to actual observed flows (from flow monitoring data), and refinements in model parameters are made to achieve a reasonable match to the observed flows. RMC will calibrate the model first for dry weather conditions, and then to monitored wet weather events. Calibration for dry weather conditions focuses on confirming unit flow factors and diurnal profiles. For wet weather calibration, RMC will identify appropriate wet weather events based on an assessment of the City's available flow monitoring data from 2004 and 2005, to which the model will be calibrated. Data assessment will consist of a review of the data collected at each flow monitoring site, and will address the reasonableness of wet weather flow responses with respect to the intensity and duration of measured rainfall, as well the relative quality of the data that could impact the integrity of calibration results. RMC may also recommend additional flow monitoring if needed to improve model calibration. Once calibrated, the model will be ready to be used to simulate hypothetical design conditions and identify capacity problems in Task 6. Subtask 5.4 - Prepare Model Documentation RMC will prepare documentation of the basis for model construction and calibration. This documentation will focus on the sources of data used and how the model was developed 4