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' RIVERPOINTlGILHAM ROAD STORMWATER MANAGEMENT PROJECT <br /> CH2M HILL will compile a request for information to be submitted to the City. A summary <br /> of the review will be incorporated into the technical memorandum (TM) prepared for Task 2 <br /> <br /> ~r as described below. <br /> Task 2 -Hydrologic and Hydraulic Evaluation <br /> Task 2.1 Preliminary Hydrogeological Evaluation - Asemi-quantitative evaluation of site <br /> conditions and available groundwater data will be performed by a hydrogeologist. The <br /> objective of the evaluation is to characterize the wet- and dry-season subsurface conditions, <br /> characterize the influence of the Willamette and McKenzie Rivers on groundwater flows, <br /> and to evaluate likely surface water/groundwater interactions. Information to be gathered, <br /> as available, includes: well logs, geologic logs (boring logs from water wells and sand and <br /> gravel exploration if available), water rights and state well records to identify any additional <br /> existing wells in the project area; water level data, staff gage data, USGS water supply <br /> papers, and other relevant information. During this phase, it is assumed that no <br /> mathematical groundwater modeling will be performed, however, the need for additional <br /> data gathering and/or analysis of groundwater or surface water/groundwater interaction <br /> will be assessed. <br /> Task 2.2 Existing SWMM Model Update - CHZM HILL will perform necessary updates to <br /> the existing SWMM hydraulic model. CHZM HILL will consult with City staff to determine <br /> pazameters for model updates, specifically the range of pipe diameters, and other open <br /> . channel features for inclusion. Land use will be updated and other model parameters <br /> checked and verified. As-built drawings for new developments will be used to add new <br /> storm sewer, culverts, and other drainage facilities not contained in the current model. <br /> Task 2.3 Preliminary Hydrologic and.Hydraulic Evaluation -Based on a review of the <br /> Stormwater Management Master Plan, the SWMM hydraulic model of the <br /> Riverpoint/Gilham Road area, the hydrogeologic evaluation, and other information, CH2M <br /> HILL will develop a conceptual model of hydraulic function of the Riverpoint/Gilham Road <br /> area. This conceptual model will provide the basis for assessing the need for gathering <br /> additional quantitative data in order to address the specific questions posed: <br /> Deliverables <br /> Results of the hydrogeologic evaluation and the preliminary surface water <br /> hydrologic/hydraulic evaluation will be sununarized in a draft TM. The draft TM will <br /> describe the conceptual model of hydraulic function of the project area, and based on that <br /> model, make recommendations for either further data collection, or to undertake <br /> quantitative hydraulic modeling. The TM will be finalized following review anti! comment <br /> by the City. <br /> Task 2.4 Hydraulic Modeling -When it has been determined that sufficient information <br /> exists to develop a surface water and/or groundwater model, hydrologic and hydraulic <br /> analyses will be performed . It is assumed that two land use scenarios will be developed, <br /> including a current condition and a future land use condition. Our anticipated approach is <br /> to utilize modeled surface water outputs from SWMM as input to a stand-alone <br /> groundwater model, then update the SWMM model with a new rating curve, modified <br /> PDXIC:1DOClNAENTSAND SETTINGSIBDONNERBILOCAL SETTINGS\TEMPORARYINTERNET FILES40LK2WIVERPOINT GILHAM STORMWATERSCOPE <br /> REVISED.DOC 3 <br /> <br />