2015/08/05 Council Agenda Packet

formal "Request for Information" and coordinate with the City during data collection to ensure necessary information, if available, is gathered for the project. Requested information may include, but not limited to, the following: • Plow monitoring data within the Basin. • Updated sewer model and supporting information • Identifying and defining parameters that will be used in the modeling. 5.2 Existing Hydraulic Model Validation — Perform a model validation of the existing sewer model using specific storm events and the existirig conditions scenario, comparing the wastewater- flow and level results with those documented in the City's Comprehensive Plan and reported flooding locations. • Existing Model Coordination Conference — Conduct a meeting, in person or via conference call, with City staff and HDR or Jacobs, to discuss the existing combined system InfoSWMM hydraulic model and the design storms) to use in the recent modeling for Sewer M and for the Comprehensive Sewer Plan update. • Dry Weather Validation — Using flow monitoring information provided by the City, model the existing system under average and peak dry weather flows to confirm it accurately predicts current conditions. • Wet Weather Validation — Using flow monitoring and rainfall information provided the City, model the existing system under the design storm (design storm will be provided by the City) to confirm it accurately predicts flows and areas of flooding identified during recent wet weather events. • Existing Model Adjustment — If the model doesn't reflect the observed dry/wet weather conditions, adjustment of the model parameters will be conducted. 5.3 Proposed Improvements Evaluation — Conceptual improvements had been identified by the City to address overflows in Basin C. The project includes a separate stormwater collection network, a detention structure (one or two ponds) and a flow control structure before discharging to Trunk C. MSA will utilize the City's InfoSVVVMNI hydraulic model to determine the size and effectiveness of the proposed Northwest Stormwater Separation improvements. A sensitivity analysis will be conducted to determine the impact of extreme storm occurrence conditions. • Design.Scenario — Develop Northwest Stormwater Separation design flow conditions, discuss with the City for approval. Design scenario parameters include the design storm intensity (likely 100yr/30min) and distribution, adjustment parameters to account for climate change, dry weather parameters, and the assumption on percentage of roof drains discos-mected from the combined system. `vet weather parameters will be updated in the sewer model to represent the percentage of separation. • ��etenti077 h0779s SiZi77g — Confirm the ponds volume and location defined in Task 2 using WNVI VI. The pond volume must Le sufficient to eliminate flooding in h-1 Current cor biased system uncle lhe. Gay's selectp-d deslgiE stol'ill ConcilEloils 24 QRAITk-1 '-'- GG�:,f'T 3'TF 7T\Jf \Tnrthv.r�it `Tnrn��:-af-r �=i�a�aiinn