Fort Walton Beach Council agenda — 09-13-11 regular — reading text

the data types required shall generally include but not necessarily be limited to: Comprehensive Plan Documents Local, State or Federal rules, regulations, ordinances and laws Engineering reports, basin studies or other pertinent documents Existing and future land use and zoning information ( including DRI' s, PUD' s, EIS' s, EA' s major subdivision plans) Construction plans ( e.g., design or As- built) for development Control structure information including lake level management schedules Page 7 City of Fort Walton Beach Stonn ater Master Plan Scope. docx Packet Pg. 161  am FDOT, City of Fort Walton Beach and applicable Okaloosa County/municipality roadway construction plans and survey information Most recent NRCS soil survey data Regional Leakance and recharge rates ( if applicable) Stream flow e / levation and lake level data Historic rainfall, evaporation and evapotranspiration data and analysis Historic, measured flood levels or flows Aquifer recharge and potentiomctric data litigation practices Effluent disposal rates City of Fort Walton Beach' s most recent Vertical Control Point & Elevation Data Aerial and topographic maps City of Fort Walton Beach plat, right -of w - ay and easement information Seasonal high water level determinations Tidal information FIRM mapping and Flood Insurance Study reports Citizen questionnaires Data Collection by City with Assistance from HMM From the data and primary drainage system information compiled above, existing drainage structures and conveyances shall be preliminarily mapped and overlaid on contoured aerial maps. HMM will review the data and identify gaps in data and recommend additional critical areas for field verification. A preliminary meeting will be held with City and HMM staff to review the identified data gaps and recommended critical areas for further data collection. HMM shall assist the City as requested in the collection of required data on a time and material compensation basis, up to the limit of the allowance specified. HMM assistance shall not begin without prior City authorization. The City ( or HMM when requested) shall collect the following information for inclusion into the model: L Preliminary invento" Icataloeuine. Field visits to structures shall be conducted and information pertaining to location, dimension and condition shall be provided for inclusion in the cataloguing/ invenmry, of the primary drainage system. The inventory shall include all pipes or drainage ways with conveyance equal to or greater than a 15 -inch diameter pipe, locations of known drainage problems regardless of primary conveyance discharge size, as well as all creeks, ponds and lakes which drain areas in excess of 25 acres. Digital photographs of all structures and water bodies shall be taken at the time of the field visit. 2. Tomeraphic sun" ofDrainage Structures and Subsurface Systems: Based upon the primary drainage system inventory and mapping, HMM shall identify necessary field surveys. Field surveys shall include measurements of cross sections, structure dimensions, material type, inverts, Structure type ( i.e. junction box, inlet, etc) Structure rim elevations and Structure throat elevations. All collected data shall be provided for inclusion in the primary drainage system inventory. City of Fort Walton Beach Stormwater Master Plan Scope. docx Ng, Packet Pg. 162  3. Toyouayh1c s () of Specitic Basin Areas' Areas along channels, streams and creek cross sections which lack adequate defurition from contoured aerial maps, compiled data or survey information shall be identified. Upon completion, the survey data shall be incorporated into the existing GIS contour information. 4. Additional data. City shall provide additional data, if available, to supplement information HMM has obtained from agencies and/ or organizations listed above to include: Water surface elevations Base flow rates in primary drainage system reaches Comprehensive GIS throughout City limits including contours, soil types, existing land use, future land use, flood zones, etc. Roadway elevations at crossing of arterial and collector roadways. Crest lengths for roadway crossings. Critical flooding elevations ( i. e., finished floor elevations for residences, evacuation routes, etc.) Reach cross sections at 1000' intervals maximum and all significant changes in cross- section properties. Data Collection Summary Meeting The data collection phase of the project shall be concluded with a meeting with City staff to identify potential significant remaining data gaps, discuss potential additional survey needs and obtain City approval to proceed to Model Development. This meeting shall include a review of the project map set, identified problem areas and other pertinent data. Any information deemed insufficient or absent shall be discussed along with an approach to remedy those data gaps. Finally, issues regarding key modeling assumptions necessary for model development shall be discussed including initial conditions, curve numbers, directly connected impervious areas ( DCIA) and other pertinent parameter calculations. Task 2 Model DevelopmenC This task will include assisting the City in selecting a comprehensive modeling platform and the development and input of hydraulic and hydrologic data points to replicate real world systems. While the selected system should be capable of performing water quality analysis for future numeric nutrient criteria purposes, the current scope of services shall be limited to rate and volume analyses. In the completion of this task BMM will provide the following efforts: Modeling Platform HMM shall review available surface water /stormwater modeling software packages for consistency with a desired list of attributes developed by the City. HMM shall coordinate with City personnel and the software providers to schedule a one day series of presentations on software capabilities to aid the City in selecting a comprehensive modeling software platform to achieve the City' s needs and desires. The City shall purchase the selected computer model and desired ancillary programs and the rights for HMM to work within the purchased software package( s) to accomplish the work described herein. Page 7 City of Fort Walton Beach Stotmwater Master Plan Scope.docx Packet Pg. 163  Hydraulic Model Development A model node map shall be generated by placing nodes at strategic locations along the primary drainage systems) within the GIS base files. Nodes shall be placed in areas where stage and flow data are required, such as road crossings, ponds, lakes and structures. Nodes shall be located so that channel lengths are generally kept to a maximum of 1000 feet and that segments are approximately uniform in length to the greatest extent possible. Warning elevations shall be identified and entered into node data to identify critical flooding areas such as roadways or homes and used to evaluate the drainage system level of service. Links shall subsequently be created to connect successive nodes in series. Link data shall be entered for drainage structures as well as cross sections based upon the collected or surveyed dam. Hydrologic Model Development Based upon the final node map layout and other pertinent hydrographic features including topographic ridge lines, hydraulic control points or constructions and storage areas), contributing watershed basins shall be delineated. Identified contributing watershed basins shall subsequently be sub -divided to separate significantly different land uses to the greatest extent practicable. Drainage areas, CN numbers, directly connected impervious areas ( DCIA) and time of concentration shall be calculated and entered into the model Okaloosa County Stormwater Master plan Model Integration Where possible, the Okaloosa County Stormwater Master plan model data shall be converted to the selected model software platform and integrated into a single model of the County and City primary drainage systems. All Okaloosa County Model data shall be incorporated on an as -is basis. Review of the accuracy of the Okaloosa County Stormwater Master plan model node map or data entry is not included in this scope of services. Depending on the final model platform selected by the City, full importation of data from the county' s HEC/RAS model may or may not be feasible. If complete data importation is not feasible, then model outputs from the County' s model shall be used to develop new inputs into the City model and manually entered. Preliminary Model Setup Meeting The preliminary model setup phase of the project shall be concluded by a meeting with City staff to discuss model inputs and identify final model revisions that are required prior to proceeding to the next phase of the project. While not being utilized in the current scope of service, the model should be established such that it is readily adapted to accept pollutant loading parameters and perform pollutant loading analysis for use with future water quality based effluent limitations ( WQBEL' s) or numeric nutrient criteria as needed. N" 7 City of Port Walton Beach Stunnwater Master Plan Scope. docx Packet Pg. 764 Task 3 Model Simulations: This task will involve the simulation of the 10, 25, 50 and 100 year frequency recurrent storm events, each with 1, 2, 4, S, 24 and 72 -hr stoma durations in accordance with the SCS Type III rainfall distribution. The goal of these scenarios is to detemdne the critical rainfall event( s). Depths shall be based upon iso-