Res 2015-010/agreement between the City and Freese and Nichols, Inc. for the provision of Professional Engineering Services in connection with The Hopkins Street: Bishop to Moore Improvements Project

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Hopkins Street— Preliminary Engineering Attachment A January 22, 2015 4. Drainage Study Because the storm drainage system is limited in size and extents, it is recommended that a dynamic, two - dimensional (2D) model of the drainage system be developed to identify extents of existing conditions flooding, as well as the benefits of proposed improvement alternatives. This scope anticipates creation of hydrologic and hydraulic (H &H) models of the storm drainage system utilizing XPSWMM to evaluate the systems crossing the proposed roadway. Tasks are further defined below. A. Data Collection (1) Obtain the FEMA Effective Models for Purgatory Creek from FEMA. (2) Obtain existing master plans, models, reports, as -built construction plans and /or studies of the drainage features within the project limits from the City. Coordinate with RPS Engineers regarding the City's ongoing Stormwater Master Plan to ensure there is no duplicity in efforts. (3) Obtain past drainage work -order and property owner complaint documentation. (4) Conduct engineering site visit to obtain visual confirmation of hydraulic features and existing drainage conditions. (5) Obtain aerial photographic and topographic information for use in developing hydrologic and hydraulic models. B. Public Involvement (1) Coordinate drainage study with Project Public Involvement efforts —see Task 6. (2) Create a GIS Database to evaluate geographic location of historical drainage complaints and work order locations. (3) Prepare public input forms for distribution to project stakeholders. (4) Obtain, tabulate and populate public input into GIS Database. C. Hydrologic Analysis (1) Review existing studies and hydrologic models. (2) Compare existing watershed delineations with topographic and field survey information obtained for this project. (3) Verify hydrologic parameters within existing HEC -HMS models. Utilize, as appropriate, hydrologic parameters from existing hydrologic models in creation of the existing conditions H &H model. (4) Coordinate with TxDOT to determine acceptable hydrologic parameters and appropriate design criteria. (5) Hydrologic calculations will be based on SCS Curve Number methodology and SWMM routing. (6) Precipitation inputs will be based on synthetic frequency events. (7) All hydrologic calculations will be performed within the combined H &H model environment. (8) Models will be executed for a range of storms, including 1 -, 2 -, 5 -, 10 -, 25 -, 50- and 100 - year return event storms for 24 -hour duration hydrographs D. Hydraulic Analysis (1) Existing Conditions (a) Review existing studies and available hydraulic models. Utilize effective FEMA models of Purgatory Creek as downstream starting conditions for any systems that tie into the Creek. [OFF14041] L: \OLCR \San Marcos