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HomeMy Public PortalAbout2005 - Stormwater Master Plan - Phase 4 - Mo River and Algoa StudyMissouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 Comprehensive Stormwater Master Plan Update Phase 4: Missouri River & Algoa Study Area Report for the City of Jefferson, Missouri Prepared by: Burns & McDonnell Project Number 36505 9400 Ward Parkway Kansas City, Missouri 64114-3319 Tel: 816 333-9400 www.burnsmcd.com November 18, 2005 Mr. Pat Sullivan City of Jefferson Community Development City Hall 320 East McCarty Street City of Jefferson, Missouri 65101 Comprehensive Stormwater Management Plan Update, Phase 4: Missouri River and Algoa Study Area Report FINAL SUBMITTAL Burns & McDonnell Project No. 36505 Dear Mr. Sullivan, Burns & McDonnell Engineering is pleased to present this draft submittal of the City of Jefferson’s Comprehensive Stormwater Master Plan Update, Phase 4: Missouri River and Algoa Study Area Report. It has been a pleasure working with you and your staff on this project, and we look forward to continued work with your City. If we can be of further assistance, please do not hesitate to call. Best Regards, Galen Miller, P.E. Project Manager Enclosed: Ten Report Binders Ten CD-ROM Electronic Reports Missouri River and Algoa Study Area Stormwater Management Plan City of Jefferson, Missouri CITY OF JEFFERSON, MISSOURI COMPREHENSIVE STORMWATER MASTER PLAN UPDATE PHASE 4: MISSOURI RIVER AND ALGOA STUDY AREA REPORT B&McD Project No. 36505 INDEX AND CERTIFICATION PAGE REPORT INDEX Section Description Page Number of Pages ES Executive Summary ES-1 3 1 Introduction 1 3 2 Data Collection 4 2 3 Hydrologic Modeling 6 8 4 Hydraulic Modeling 14 8 5 Existing System Performance 22 7 6 Recommendations 29 20 7 Glossary of Terms 49 5 Appendix A XP-SWMM Runoff (Hydrologic) Results 4 Appendix B XP-SWMM Surcharging Tables 2 Appendix C HEC-RAS Results for Existing Conditions 20 Appendix D HEC-RAS Results for Future Conditions 20 Appendix E Exhibits 12 I hereby certify, as a Professional Engineer in the State of Missouri, that the information in this document was assembled under my direct responsible charge, and is based on information and data that was available and obtained from the sources described herein. The Engineer cannot be held responsible for added or deleted information once distributed. CERTIFICATION Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 i Missouri River and Algoa Study Area Report City of Jefferson, Missouri TABLE OF CONTENTS EXECUTIVE SUMMARY........................................................................................................ES-1 GENERAL INFORMATION..............................................................................................................ES-1 METHODOLOGY..............................................................................................................................ES-1 Data Collection...........................................................................................................................................................ES-1 Hydrology...................................................................................................................................................................ES-1 Hydraulics...................................................................................................................................................................ES-1 SUMMARY OF RECOMMENDATIONS...........................................................................................ES-2 SECTION 1.0 - INTRODUCTION.................................................................................................1 1.1 PROJECT TEAM..............................................................................................................................1 1.2 STUDY AREA...................................................................................................................................1 1.3 PURPOSE.........................................................................................................................................1 1.4 SCOPE OF SERVICES....................................................................................................................1 1.4.1 Information Review.................................................................................................................................................2 1.4.2 Field Investigations and Inventory...........................................................................................................................2 1.4.3 Existing System Evaluation.....................................................................................................................................2 1.4.4 Watershed Mapping.................................................................................................................................................2 1.5 INFORMATION PROVIDED BY CLIENT.........................................................................................2 SECTION 2.0 - DATA COLLECTION...........................................................................................4 2.1 DATUM AND PROJECTION INFORMATION.................................................................................4 2.2 MAPPING SOURCES......................................................................................................................4 2.3 FIELD INVESTIGATIONS................................................................................................................4 2.3.1 Major Structures (Bridges/Culverts)........................................................................................................................5 2.3.2 Minor Structures......................................................................................................................................................5 2.4 PROJECT PHOTOGRAPHS ............................................................................................................5 2.5 OTHER SOURCES OF INFORMATION..........................................................................................5 SECTION 3.0 - HYDROLOGIC MODELLING..............................................................................6 3.1 INTRODUCTION..............................................................................................................................6 3.2 WATERSHED DELINEATION.........................................................................................................6 3.2.1 Subarea Boundaries..................................................................................................................................................6 3.3 PRECIPITATION..............................................................................................................................6 3.3.1 General.....................................................................................................................................................................6 3.3.2 Rainfall Distribution................................................................................................................................................6 3.3.3 Rainfall Depths........................................................................................................................................................7 3.3.4 Rainfall Duration......................................................................................................................................................7 3.4 RUNOFF...........................................................................................................................................8 3.4.1 Soils.........................................................................................................................................................................8 3.4.2 Land Use..................................................................................................................................................................8 Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 ii 3.4.3 Loss Method...........................................................................................................................................................10 3.4.4 Subarea Lag Time..................................................................................................................................................10 3.4.5 Time of Concentration...........................................................................................................................................10 3.4.6 Hydrographs...........................................................................................................................................................11 3.4.7 Conveyance Routing..............................................................................................................................................11 3.5 MODEL CALIBRATION.................................................................................................................11 3.5.1 APWA 5600 Rational Method...............................................................................................................................12 3.5.2 Conclusion.............................................................................................................................................................13 SECTION 4.0 - HYDRAULIC MODELLING...............................................................................14 4.1 INTRODUCTION............................................................................................................................14 4.2 DIGITAL TERRAIN MODEL...........................................................................................................15 4.3 STREAM NETWORK.....................................................................................................................15 4.4 CROSS-SECTION CUT-LINES......................................................................................................15 4.5 MANNING’S “n” VALUES.............................................................................................................16 4.6 BRIDGES AND CULVERTS..........................................................................................................16 4.6.1 Cross Sections........................................................................................................................................................17 4.6.2 Bridge Deck / Roadway.........................................................................................................................................17 4.6.3 Modeling Approach...............................................................................................................................................17 4.6.4 Internal Bridge Cross Sections...............................................................................................................................17 4.7 INEFFECTIVE FLOW AREAS .......................................................................................................17 4.8 EXPANSION AND CONTRACTION COEFFICIENTS...................................................................17 4.9 FLOW DATA...................................................................................................................................18 4.9.1 Profiles...................................................................................................................................................................18 4.9.2 Flow Change Locations..........................................................................................................................................18 4.9.3 Boundary Conditions.............................................................................................................................................18 4.9.4 Flow Conditions.....................................................................................................................................................18 4.9.5 Detention / Storage.................................................................................................................................................19 4.10 FLOODWAY ANALYSIS..............................................................................................................19 4.11 CALIBRATION.............................................................................................................................19 4.11.1 Previous Studies...................................................................................................................................................19 4.11.2 Stormwater Questionnaire....................................................................................................................................19 4.12 QUALITY CONTROL / DEBUGGING..........................................................................................19 4.13 Digital Models..............................................................................................................................20 SECTION 5.0 - EXISTING SYSTEM PERFORMANCE.............................................................22 5.1 Missouri River and Algoa District Study Area...........................................................................22 5.1.1 Land Use................................................................................................................................................................22 5.1.2 Hydrologic Summary.............................................................................................................................................22 5.1.3 Existing Drainage System......................................................................................................................................24 5.2 EVALUATION CRITERIA...............................................................................................................25 5.3 DRAINAGE SYSTEM PERFORMANCE........................................................................................25 5.3.1 Major Structure Modeling Results from HEC-RAS...............................................................................................26 5.3.2 Minor Structure Modeling Results - Surcharging..................................................................................................27 SECTION 6.0 - RECOMMENDATIONS......................................................................................29 Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 iii 6.1 INTRODUCTION............................................................................................................................29 6.2 SURVEYOR'S OBSERVATIONS...................................................................................................29 6.3 EVALUATION OF PRIORITIES.....................................................................................................30 6.3.1 Methodology..........................................................................................................................................................30 6.3.2 Priority Definitions................................................................................................................................................30 6.4 Cost Opinions for Projects..........................................................................................................32 6.5 PROJECT 1 – Main St. & Circle Dr. (City Project).....................................................................33 6.5.1 Description.............................................................................................................................................................33 6.5.2 Recommended Improvement.................................................................................................................................33 6.5.3 Cost Opinion..........................................................................................................................................................34 6.5.4 Priority...................................................................................................................................................................34 6.6 PROJECT 2 – High Street & Benton Street (City Project)........................................................35 6.6.1 Description.............................................................................................................................................................35 6.6.2 Recommended Improvement.................................................................................................................................35 6.6.3 Cost Opinion..........................................................................................................................................................35 6.6.4 Priority...................................................................................................................................................................35 6.7 PROJECT 3 – Allen Drive (City Project).....................................................................................37 6.7.1 Description.............................................................................................................................................................37 6.7.2 Recommended Improvement.................................................................................................................................37 6.7.3 Cost Opinion..........................................................................................................................................................37 6.7.4 Priority...................................................................................................................................................................37 6.8 PROJECT 4– Delta Place & Riverwood Drive (City Project)....................................................39 6.8.1 Description.............................................................................................................................................................39 6.8.2 Recommended Improvement.................................................................................................................................39 6.8.3 Cost Opinion..........................................................................................................................................................40 6.8.4 Priority...................................................................................................................................................................40 6.9 PROJECT 5 – State Street & Marshall Street (City Project).....................................................41 6.9.1 Description.............................................................................................................................................................41 6.9.2 Recommended Improvement.................................................................................................................................41 6.9.3 Priority...................................................................................................................................................................41 6.10 PROJECT 6– Algoa District (City Project)...............................................................................42 6.10.1 Description...........................................................................................................................................................42 6.10.2 Recommended Improvement...............................................................................................................................42 6.10.3 Priority.................................................................................................................................................................42 SECTION 7.0 - GLOSSARY OF TERMS...................................................................................49 7.1 DEFINITIONS.................................................................................................................................49 7.2 ACRONYMS...................................................................................................................................52 APPENDIX A – XP-SWMM HYDROLOGIC RUNOFF RESULTS APPENDIX B – XP-SWMM SURCHARGING RESULTS APPENDIX C – HEC-RAS RESULTS, EXISTING CONDITIONS APPENDIX D – HEC-RAS RESULTS, FUTURE CONDITION APPENDIX E – EXHIBITS Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 iv Exhibit 1 Missouri River Study Area Exhibit 2 Hydrologic Modeling Data Exhibit 3 Soils Data Exhibit 4 Existing Conditions Land Use Plan Exhibit 5 Future Conditions Land Use Plan Exhibit 6 Existing and Future 100-year Floodplains and Hydraulic Modeling Data Exhibit 7 XPSWMM Hydraulic Modeling Data Exhibit 8A, 8B, 8C Surcharging in XPSWMM LIST OF TABLES Table ES-1 Summary of Recommendations...............................................................................ES-2 Table 3-1 Rainfall Depths for City of Jefferson, Missouri................................................................7 Table 3-2 Runoff Coefficients.............................................................................................................9 Table 3-3 Small Subshed Flow Comparison...................................................................................12 Table 4-1 Summary of Missouri River Study Area HEC-RAS Model.............................................14 Table 4-2 Data Development.............................................................................................................14 Table 4-3 Manning’s Roughness Coefficients ................................................................................16 Table 4-4 Expansion and Contraction Coefficients........................................................................18 Table 4-5 HEC-RAS Models...............................................................................................................20 Table 4-6 XP-SWMM Models.............................................................................................................21 Table 5-1 Land Use Breakdown for Moreau River South...............................................................22 Table 5-2 Hydrologic Characteristics of Moreau River South.......................................................23 Table 5-3 Existing Design Criteria, Culverts...................................................................................24 Table 5-4 Existing Design Criteria, Open Channels.......................................................................24 Table 5-5 HEC-RAS Analysis of Major Structures..........................................................................26 Table 6-1 HEC-RAS Analysis of Major Structures..........................................................................30 LIST OF FIGURES Figure ES-1 Project Locations.......................................................................................................ES-3 Figure 3-1 SCS Rainfall Distribution...................................................................................................7 Figure 6-1 Project 1 Main St. & Circle Dr..........................................................................................43 Figure 6-2 Project 2 High St. and Benton St....................................................................................44 Figure 6-3 Project 3 Allen Dr..............................................................................................................45 Figure 6-4 Project 4 Delta Pl. & Riverwood Dr.................................................................................46 Figure 6-5 State St. & Marshall St......................................................................................................47 Figure 6-6 Algoa District....................................................................................................................48 Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 ES-1 EXECUTIVE SUMMARY GENERAL INFORMATION Burns & McDonnell Engineering Company was authorized by the City of Jefferson, Missouri to study areas of the Missouri River watershed within the city limits that had not been examined in previous studies (see Exhibit 1). These included three small areas on the south bank of the Missouri River that drain directly to the river without entering another creek, and a district known as the Algoa Area. Different portions of the Algoa Area drain to Rising Creek, the Osage River, and the Moreau River. The main stems of the Missouri River, the Moreau River, and the Osage River are excluded from the analyses that were conducted for this report. The area studied included approximately 7.98 square miles of drainage (5,107 acres). The Missouri River and Algoa Study Area Report is part of the fourth and final phase of the City of Jefferson Stormwater Master Plan. The purpose of this study is to perform a hydrologic analysis of this area under existing and future development conditions, and a hydraulic analysis of the stormwater drainage system. The results of these analyses have allowed floodplains to be drawn for these areas, and for culvert and pipe flow demands to be better understood. METHODOLOGY Data Collection Data about the watershed was collected in a geographically referenced database, ESRI’s Geographical Information System (GIS) mapping software. This information was used to generate the input and store the output from XP-SWMM 2000 stormwater modeling software and the U.S. Army’s Corps of Engineers HEC-RAS river analysis program. The GIS database serves as both an inventory of the stormwater system and an easily accessible repository of the results of this study. Hydrology The watershed was classified for soil type, vegetative cover, current, and future land use and divided into subsheds. Hypothetical storms with return periods from two to one hundred years were used to simulate stormwater runoff and generate flow hydrographs from each subshed for both existing and future land use conditions. A FEMA approved hydrologic modeling software, XP-SWMM2000 was used to perform these analyses. Hydraulics Routing of the runoff hydrographs through culverts and pipe systems was computed, and peak flows were evaluated in the major channels and large culverts of the watershed to calculate water surface elevations. Floodplains were then drawn for the 100-year existing and future conditions. XP-SWMM2000, the U.S. Army Corps of Engineer’s HEC-RAS river analysis software, and GIS were used for these tasks. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 ES-2 SUMMARY OF RECOMMENDATIONS Recommendations were developed for those conveyance structures that posed an immediate or future safety concern, or were identified by the City or County as priority projects. The objective of the recommendations is to provide planning level solutions. However not all of the recommendations suggest improvements. The large number of recently built, surcharging structures in the Algoa Area do not warrant recommendations for replacement, but should be carefully monitored for maintenance activities and new development in upstream areas. Many of these surcharging structures are privately owned or owned by the state of Missouri. Based on modeling studies and input from the City, the flooding problems identified in this study were grouped into projects. Two of these projects are not prioritized because no recommendation for City action is made, but they are included to suggest areas where further development must proceed cautiously, and maintenance activities should be systematic. Table ES-1 summarizes these projects. Table ES-1 Summary of Recommendations Project Location Description Construction Cost Priority 1 City Main St. & Circle Dr. Upsize 190’ of pipe $100,449 HIGH 2 City High St. & Benton Dr. Upsize 843’ of pipe $341,804 HIGH 3 City Allen Dr. Upsize 268’ of pipe $131,749 MEDIUM 4 City Delta Pl. & Riverwood Dr. Upsize 115’ of pipe $94,366 LOW 5 City State St. & Marshall Dr. ------ REVIEW DURING FUTURE DEVELOPMENT 6 City Algoa Area ------ REVIEW DURING FUTURE DEVELOPMENT Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 1 SECTION 1.0 - INTRODUCTION In the year 2001, the City of Jefferson embarked on a program to develop stormwater master plans for each of the City’s major watersheds. This program is based on a recognized need to upgrade existing inadequate stormwater conveyance systems and to plan for new systems in developing areas. The economic well being of the City depends on its ability to attract and retain business and industry as well as residents to live in the City. Part of the City’s ability to attract business and residents depends on its ability to provide adequate services such as drinking water, sewers, transportation and stormwater management. Historically, stormwater management has only been a concern when major floods occur. With increased development and the associated increases in impervious area due to development, the volume of runoff from rainfall and the frequency of flooding have correspondingly increased. This has caused the City to focus its attention on the need to provide improved stormwater management facilities in all areas of the City. 1.1 PROJECT TEAM Burns & McDonnell Engineering was the prime contractor for this study. Central Missouri Professional Services, Inc. conducted the field surveys. Burns & McDonnell Engineering 9400 Ward Parkway Kansas City, Missouri 64114 phone: (816) 333-9400 Project Manager: Galen Miller, PE Central Missouri Professional Services 2500 East McCarty Street Jefferson City, Missouri 65101 phone: (573) 634 3455 Contact: Keith Brickey 1.2 STUDY AREA The areas studied for this phase of this report include the Missouri River Study Area and the Algoa Area (see Exhibit 1). The Missouri River Study Area represents three small watersheds that drain to the Missouri River without entering another named tributary. The Algoa Area represents a large area that is predominantly part of an annexation that occurred in November 2003. This area drains to the Missouri River via the Moreau River, Osage River and Rising Creek. However the main stems of these waterways are specifically excluded from the analysis. Together, these areas represent about 7.98 square miles of drainage area. 1.3 PURPOSE The Missouri River and Algoa Study Area Report is part of the fourth and final phase of the City of Jefferson Stormwater Management Plan. The purpose of this study is to model existing and future surface conditions and the ability of the storm drainage system to convey the runoff from various events. 1.4 SCOPE OF SERVICES Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 2 This report presents a description of the services completed for the hydrologic and hydraulic modeling under existing and future surface conditions for the Missouri River and Algoa Study Area watersheds. The report will include supporting text, tables, figures, exhibits, computer models, computer output and appendices to accurately present the services completed. The following major tasks are included in this study: 1.4.1 Information Review A comprehensive review of the existing information and studies provided an understanding of existing conditions and the improvement plans previously proposed and/or implemented. This task involved the assemblage, review and organization of existing mapping, records, reports, ordinances, criteria and floodplain studies available from the City, County and other sources. 1.4.2 Field Investigations and Inventory A survey of the watersheds and drainage system was conducted within the study area. The purpose of this field investigation was to obtain specific information on existing piping systems, channels and structures. Observations were recorded in a standardized format and supplemented with photographic records. Data gathered included the following items: • Measurement of hydraulic parameters • Logging of information in a GIS-compatible format. 1.4.3 Existing System Evaluation Hydrologic and hydraulic models were developed for drainage system components (structures and/or natural and improved channels) beginning where 24 inch or larger culverts were in place. The stormwater system was evaluated under the following two (2) conditions: • Existing conditions with the existing storm sewer system – This plan represents conditions as currently observed within the watershed. • Future surface conditions with the existing storm sewer system – This plan represents fully urbanized conditions in the watershed without changes to the existing sewer system. 1.4.4 Watershed Mapping The FEMA Flood Insurance Study was published October 6, 1981. Since that time, the watershed has experienced considerable urbanization. Additionally, advances in hydrologic and hydraulic modeling, the introduction of Geographical Information Systems (GIS) and new aerial topography allow a more accurate representation of floodplains. For this study new floodplains were developed for the 100-year storm event for existing and future surface conditions. It was not within the scope of this study to prepare a FEMA map revision. 1.5 INFORMATION PROVIDED BY CLIENT Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 3 In the preparation of this report, the information provided by the Client was used to make certain assumptions with respect to conditions which may exist in the future. While Burns & McDonnell believes the assumptions made are reasonable for the purposes of this report, Burns & McDonnell makes no representation that the conditions assumed will, in fact, occur. In addition, while Burns & McDonnell has no reason to believe that the information provided by the Client, and on which this report is based, is inaccurate in any material respect, Burns & McDonnell has not independently verified such information and cannot guarantee its accuracy or completeness. To the extent that actual future conditions differ from those assumed herein or from the information provided to Burns & McDonnell, the actual results will vary from those forecast. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 4 SECTION 2.0 - DATA COLLECTION 2.1 DATUM AND PROJECTION INFORMATION Mapping data was provided by the City in GIS format referenced to the following datum and projection information: Horizontal Datum: 1983 North American Horizontal Datum (NAD83) Vertical Datum: North American Vertical Datum 1988 (NAVD88) Coordinate System: Missouri Central State Plane (FIPS Zone 2402 - Feet) 2.2 MAPPING SOURCES • Topography – 2-foot contour interval • Mass Points and Break Lines • Aerial Photography • Planimetrics • Soils Information – Soil mapping from the University of Missouri Spatial Data Information Service (MSDIS) • Land Use / Land Planning (Zoning) 2.3 FIELD INVESTIGATIONS Elevation and location surveys of the stormwater drainage system were conducted in conjunction with this study. Surveys collected the hydraulic data for drainage structures within the study area identified by the Engineer, City and County Staff. Significant drainage structures were generally identified by the following criteria: • 24 inch diameter (or equivalent capacity) or larger. • Major structures (bridge or culvert) having tributary areas of 160 acres or greater. • Hydraulic structures within close proximity of buildings or other significant land objects. • Other structures of interest identified by City and County staff. A combination of Global Positioning Systems (GPS) and total station technology was used to obtain the required elevations for surveyed structures. Elevation information was collected using a data collector. Additional information, such as shape, material, condition, type, etc. was recorded on standardized forms. The data collected at the various types of drainage structures is listed below. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 5 For those structures that were not surveyed, but are part of the modeled conveyance system, openings were measured and inverts approximated from the available topography. 2.3.1 Major Structures (Bridges/Culverts) • Upstream channel cross-sections • Structure opening dimension information • Low chord and top of road elevations • Top centerline elevation section to define weir flow overtopping the structure • X, Y, and Z coordinate information • Digital photographs consisting of upstream face, looking upstream, downstream face, and looking downstream 2.3.2 Minor Structures • Structure opening dimension information • Overtopping elevations controlling the roadway's level of service • Construction material and condition • Other unusual or pertinent information • Digital photographs 2.4 PROJECT PHOTOGRAPHS As part of the scope of the project, digital photographs were taken of each hydraulic structure (i.e. bridges, culverts, and inlets, etc.) studied during the project. Project photographs are included in this report as digital files. 2.5 OTHER SOURCES OF INFORMATION In addition to the information described above, several other sources of information were consulted during completion of the project: • Q3 floodplain boundaries – FEMA • Flood Insurance Rate Maps (FIRM’s) – FEMA • Flood Insurance Study (FIS) – FEMA Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 6 SECTION 3.0 - HYDROLOGIC MODELLING 3.1 INTRODUCTION The hydrologic analysis for this study was done using XP-SWMM2000 stormwater management modeling software (Version 8.52) from XP Software Incorporated. The software generates runoff hydrographs at desired locations in the watershed for specific storm events based on the specific input parameters for each component of the process. For this study, the RUNOFF module was used to generate hydrographs for return periods of 2, 5, 10, 25, 50 and 100 years. Parameters used in the hydrologic modeling include the Soil Conservation Service’s (SCS) Type II hypothetical storm generated from rainfall frequency data for precipitation, the SCS curve number for the loss rate, the SCS dimensionless unit hydrograph, and physical characteristics of each subshed. 3.2 WATERSHED DELINEATION 3.2.1 Subarea Boundaries The watersheds were divided into sub watershed areas, or subsheds. These subsheds are based on hydrologic and/or hydraulic features, such as terrain, channels, confluences, and culverts or bridges within the Missouri River Study Area. Exhibit 2 shows the subsheds associated with the Missouri River and Algoa Study Area watersheds. Each subshed was assigned a unique identifier in the hydrologic model. 3.3 PRECIPITATION 3.3.1 General Every storm event that occurs within a watershed is unique. Some storms are short and intense and deposit a large amount of rainfall in a short period of time. Other storms have a constant rainfall intensity that occurs over a long period of time. Because there is no means to predict the characteristics of a given storm, a synthetic or design storm is typically used for hydrologic modeling. A design storm is simply an assumed distribution of rainfall over a given amount of time. 3.3.2 Rainfall Distribution For this study, a Soil Conservation Service (SCS) Type II rainfall distribution was used. The SCS distribution was prepared for use in the United States for storms of 6 and 24-hour durations. The Type II storm distribution is applicable to central Missouri. The distribution of rainfall is shown in Figure 4-1. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 7 3.3.3 Rainfall Depths Technical Paper No. 40 Rainfall Frequency Atlas of the United States (TP-40) was used to determine the rainfall depths for various storm recurrence periods and various time periods. The TP-40 based data is shown in Table 4-1 below: Table 3-1 Rainfall Depths for City of Jefferson, Missouri Depth (inches) Time 2-yr 5-yr 10-yr 25-yr 50-yr 100-yr 5 min 0.45 0.54 0.6 0.69 0.77 0.84 10 min 0.71 0.87 0.98 1.14 1.27 1.4 15 min 0.89 1.1 1.24 1.45 1.62 1.78 30 min 1.19 1.5 1.71 2.02 2.26 2.5 1 hr 1.5 1.92 2.2 2.61 2.93 3.25 2 hr 2 2.5 2.9 3.3 3.75 4.2 3 hr 2.25 2.75 3.25 3.75 4.15 4.65 6 hr 2.65 3.3 3.85 4.45 4.9 5.55 12 hr 3.25 3.85 4.55 5.2 5.8 6.55 24 hr 3.5 4.55 5.35 6.1 6.7 7.5 3.3.4 Rainfall Duration The design storm used in the analysis of a drainage system is the pattern of rainfall over a specific duration for a given return period. The duration that puts the greatest demand on the system is termed the SCS Rainfall Distribution 0% 20% 40% 60% 80% 100% 0%20%40%60%80%100% Percent of Storm Duration Cu m m u l a t i v e P e r c e n t o f Ra i n f a l l Figure 3-1 Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 8 “critical storm duration” and is roughly equal to the time of concentration of the watershed. Time of concentration, Tc, is the time at which the entire drainage area begins to contribute runoff. It may also be defined as the time required for runoff to flow from the farthest point in the watershed to the outlet. The “critical” duration represents the minimum time required to insure that runoff from all parts of the drainage area is included in the peak discharge measured at the outlet. The design storm duration used in this project was the 6-hour storm for all return periods. 3.4 RUNOFF 3.4.1 Soils NRCS soils information used for calculating hydrologic parameters was obtained in an electronic format from the Missouri Spatial Data Information Service (MSDIS)1. According to the source, soil scientists manually compiled field maps on 1:24000 scale one-third-quadrangle ortho-photography in the 1927 North American Datum (see Exhibit 3). 3.4.2 Land Use 3.4.2.1 Existing Conditions In order to determine the parameters needed for the hydrologic model, a land use map was developed for the watershed (see Exhibit 4). Land use parameters influencing runoff were estimated from aerial photography and field observations. The curve numbers shown in Table 4-2 were taken from TR-55, Urban Hydrology for Small Watersheds2. Curve numbers represent antecedent moisture condition II. 1 University of Missouri, Department of Geography, Missouri Spatial Data Information Service, http://msdis.missouri.edu/ 2 U.S. Department of Agriculture, Natural Resource Conservation Service, Conservation Engineering Division, Urban Hydrology for Small Watersheds, Technical Release 55, June 1986. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 9 Table 3-2 Runoff Coefficients Cover Type / Land Use Curve Numbers for Hydrologic Soil Group A B C D Agricultural 60 72 80 84 Brush 30 48 65 73 Commercial 89 92 94 95 Floodplain 60 72 80 84 High Density Residential 77 85 90 92 Impervious Area 98 98 98 98 Industrial 81 88 91 93 Low Density Residential 54 70 80 85 Meadow & Pasture 39 61 74 80 Medium Density Residential 61 75 83 87 Parks & Open Space 39 61 74 80 Public & Semi Public 77 85 90 92 Right of way 68.5 79.5 86 89 Steep (too steep for development) 30 48 65 73 Wooded Areas 30 55 70 77 3.4.2.2 Future Surface Conditions Hydrologic parameters for the future surface condition were based on planning information provided by the City and engineering judgment (see Exhibit 5). Several areas were assigned land uses equivalent to their proposed zoning designation. Additional criteria used to fill out the future surface condition map are as follows: • Adjacent to state routes, a 330 foot strip on each side of roadways defined as commercial. • Adjacent to major intersections involving state routes or major arterials, a 660 foot strip on each side of each intersecting roadway defined as commercial while extending 660 foot in all directions from the intersection. • For large contiguous areas that have been developed with multiple residential properties, define these areas as residential (low, medium or high density where appropriate). • For existing or developing subdivision areas, define with no change for the future surface condition. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 10 • On presently undeveloped ground, defined as undeveloped if in a flood plain, if too steep to develop (delineated when an acre or more is steeper than 15%), or zoned as open space, park or recreational. In all other cases, define as low or medium residential, or commercial or industrial based on the area proposed zoning (in those areas outside of the City but within the proposed annexation area). 3.4.3 Loss Method The SCS Curve Number Loss Method was utilized according to the technical guidelines prescribed by the TR-55 Manual. Based on the combinations of soils types and land use characteristics shown in Table 4- 2, a weighted runoff curve number was estimated for each subarea. This was done by subdividing each subarea into polygons representing every combination of land use and soils type. With a curve number assigned to each polygon, a weighted curve number was calculated for the entire subarea as follows. Weighted Curve No. = ∑(Ai x CNi) / ∑AI Where Ai = area of each shape AI = area of the subarea, acres CNi = Curve No. assigned to a given polygon 3.4.4 Subarea Lag Time For each subarea, a lag time was estimated using the SCS lag equation: Where: TL = lag, hrs L = length of mainstream to farthest divide, ft S = potential maximum retention, in (1000 / CN – 10) CN = SCS curve number Y = average slope of watershed, % 3.4.5 Time of Concentration For each subarea, a time of concentration was calculated based on the following SCS relationship: Where: TL = lag time, hrs TC = time of concentration, hrs () 5.0 7.08.0 1900 1 Y SlTL += CLTT6.0= Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 11 3.4.6 Hydrographs For each subarea, a flow hydrograph was calculated using the SCS dimensionless curvilinear unit hydrograph method. 3.4.7 Conveyance Routing XP-SWMM performs hydraulic flow routing for open channel and/or closed conduit systems. This software is a modified and FEMA approved version of EPASWMM v.4.4h. The Hydraulic module receives hydrograph input from the Runoff module and performs dynamic routing of stormwater flows through the storm drainage system to an outfall. The program will model branched or looped networks, backwater conditions, free-surface flow, pressure flow or surcharge, flow reversals, flow transfer by weirs, orifices and pumps, and storage facilities. Conveyance elements (channels, pipes, etc.) were given a value for the Manning’s roughness coefficient, which is a measure of the roughness of the element and is used in both XP-SWMM and HEC-RAS to calculate flows and water surface elevations. These ‘n’ values were selected using field observations, project photos, aerial photos, and engineering judgment. Additionally, selected channels were idealized and modeled with trapezoidal or 8-point cross-sections within the Hydraulic module. Where trapezoidal cross sections were used to represent both channel and overbank a composite ‘n’ value was derived from a preliminary 100-year storm processed in HEC-RAS. Overland flow channels were used above all closed conduits to eliminate ponding and facilitate the movement of surface flow downstream allowing for more conservative peak flows. Each overland flow channel simulated a cross sectional shape appropriate for its location. This cross sectional shape could represent a roadway sag over a culvert, a gutter section, a backyard swale, or a side yard swale between properties. 3.5 MODEL CALIBRATION The Missouri River and Algoa Study Area encompasses a collection of small watersheds that flow to the Missouri River, the Moreau River, or the Osage River. None of these streams is gaged, so it is not possible to calibrate the models to known flows. There are no past studies that examined any of these areas, and because this study area is a disjoint collection of small watersheds, the USGS Regression equations are unsuited to evaluate XP-SWMM’s validity. The range of drainage areas for which the USGS equations are valid is 0.13 to 14,000 square miles for rural areas, and 0.28 to 38.9 square miles for urban areas in Missouri. The largest subsheds available from this study range from 0.31 to 0.80 square miles (except for the Algoa area) which places the available watersheds and subsheds at the very bottom of the valid range. Because “Errors increase appreciably when any of the basin characteristics used in the equations are near or beyond the range limits,”3 the USGS equations are seen as not reliable for use for this study. 3USGS Fact Sheet 015-01, The National Flood-Frequency Program—Methods for Estimating Flood Magnitude and Frequency in Rural and Urban Areas in Missouri, 2000, March 2001 Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 12 3.5.1 APWA 5600 Rational Method A collection of subsheds with less that 200 acres was chosen randomly for this comparison. These subshed areas were selected and analyzed using the Storm Drainage Design Manual of the City of Jefferson and the APWA Section 5600’s rational method for calculating peak flows. The Rational Method 10-year and 100-year peak flows were then compared to the XP-SWMM 10-year and 100-year peak flows. The results are listed in Table 4-4. Table 3-3 Small Subshed Flow Comparison Area Number Acres Rational 10-year flow (cfs) SWMM 10-year flow (cfs) 10-year Percent Difference Rational 100-year flow (cfs) SWMM 100-year flow (cfs) 100-year Percent Difference MZ57052 0.97 2.5 4.2 68% 3.1 7.2 128% ME00022 2.95 4.2 6.1 48% 5.2 11.6 123% MZ57510 4.23 12.9 16.1 25% 16.1 27.3 70% MZ57010 4.46 18.9 28.6 51% 23.6 45.4 92% MZ57053 5.55 14.0 26.5 89% 17.5 45.0 157% MZ57559 6.81 13.4 20.4 52% 16.8 36.5 117% ME58501 7.92 11.5 19.5 69% 14.4 32.0 123% ME58092 11.58 22.4 15.4 -31% 28.0 27.8 -1% ME58013 15.29 26.8 30.0 12% 33.5 52.1 55% MZ57071 15.96 43.7 51.3 18% 54.6 87.1 60% MZ57549 17.25 31.4 36.7 17% 39.3 66.5 69% ME00014 17.40 28.8 28.8 0% 36.0 51.9 44% ME00021 23.62 41.8 31.2 -25% 52.3 57.4 10% ME58087 29.26 117.4 65.2 -44% 146.7 103.0 -30% MZ00003 31.94 75.6 81.1 7% 94.5 142.4 51% ME00033 33.95 55.8 25.4 -55% 69.8 47.1 -33% ME58023 39.25 63.3 61.9 -2% 79.2 110.4 39% ME00189 49.45 80.4 74.0 -8% 100.4 130.0 29% Average difference 16% Average difference 25% There are large individual variations, but the average differences are +16% for the 10-year flows and +25% for the 100-year flows. Because the Rational Method is a much simpler method for calculating flow, these types of variations are expected. However, these comparisons are useful in monitoring the SWMM models. In the course of this evaluation, a large number of checks were made between the collected variables and the actual numbers in the study models, such as soil type, slope, land use, conduit statistics, etc., and these helped to verify the accuracy of the model building procedure. When the results are ordered by size it can be seen that the Rational Method tends to understate runoff from smaller areas and overstate runoff from larger areas. This lends credibility to the SWMM models developed for this study because this is an expected result from the Rational Method. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 13 The subsheds analyzed for this study were aggregated into bins of roughly similar size to eliminate the expected scatter. When a logarithmic regression curve is plotted with these points, there is a very good fit with a high correlation coefficient. 3.5.2 Conclusion Although it is never desirable to proceed without gage data for calibration, it was done here, as it is commonly done elsewhere due to the scarcity of gaged streams. Lacking this validation, the process of checking different methods against one another is useful because it allows the model builder to demonstrate that the model results are consistent with generally accepted practices in calculating these statistics. The Rational Method comparisons showed pretty good accuracy and expected trending when large and small areas were compared. There were more checks performed for the other models constructed for previous phases of this study, and in each instance the model results were found to be valid. Because this study examines neighboring areas with similar geographic and hydrologic characteristics, and uses similar methodology, the same software, and the same modeler, the integrity of the results of this study are seen to be valid with only Rational flows for comparison. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 14 SECTION 4.0 - HYDRAULIC MODELLING 4.1 INTRODUCTION The HEC-RAS program (Version 3.1.2) was used to calculate water surface profiles for steady, gradually varied flow in natural and improved open channels. The model was also used to evaluate the effects of various obstructions such as bridges, culverts, weirs and structures within the floodplain of the modeled stream. HEC-RAS estimates water surface elevations in a river reach based on flows from the hydrologic block (RUNOFF) of XP-SWMM. This section discusses the procedures used for this project and guidelines developed during previous studies for developing HEC-RAS models. This section describes in detail data development, model development, model-input parameters, data format, naming conventions, and calibration. Table 5-1 summarizes some of the watershed characteristics incorporated into the HEC-RAS model. Table 4-1 Summary of Missouri River Study Area HEC-RAS Model Number of Reaches Modeled 7 Total Miles of Stream Network Modeled 6.45 Total Number of Cross-Sections 175 Average Cross-Section Spacing (ft) 195 Total Number of Hydraulic Structures Modeled 14 Number of Culverts Modeled 11 A summary of input parameters is presented in Table 5-2 and developed as follows: Table 4-2 Data Development Model Parameter Data Development Method Requirements Stream Network ArcView/GIS and HEC GeoRAS Stream network shapefile with stream reach identifiers Cross-Sections ArcView/GIS and HEC GeoRAS TIN, cross-section cut-line shapefiles Flow Lengths ArcView/GIS and HEC GeoRAS Channel and overbank (left and right) flow path shapefiles Channel Manning’s “n” Values ArcView/GIS and Manual Input Assigned by engineer and adjusted during calibration, aerial photos Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 15 Table 4-2 Data Development Model Parameter Data Development Method Requirements Overbank Manning’s “n” Values ArcView/GIS and Manual Input Land surface shapefiles created from aerial photos Roadway Crossings Field Survey, ArcView/GIS and Manual Input Roadway profile and bridge or culvert opening Expansion and Contraction Coefficient Manual Input Photos, contour and cross-section shapefiles Boundary Conditions Manual Method and HEC-RAS Normal depth calculations Ineffective Flow Areas Manual Input Photos, contour and cross-section shapefiles Channel Bank Stations ArcView/GIS and Manual Input Cross-section shapefiles Exhibit 6 shows the basic structure of the hydraulic model as well as the newly established floodplains. 4.2 DIGITAL TERRAIN MODEL A digital terrain model (DTM) was developed from the mapping data provided by the City. The DTM’s purpose for this study was to allow computer software to extract channel centerlines and cross section data. Using HEC-GeoRAS, the information contained in the mapping was extracted from the DTM and imported into the HEC-RAS model. 4.3 STREAM NETWORK The stream network was derived from the hydrography information contained in the City data. In effect, the stream network represents the channel centerlines of the streams modeled in HEC-RAS. 4.4 CROSS-SECTION CUT-LINES Placement and alignment of cross sections are determined by engineering judgment. The maximum spacing between cross sections is 500 feet. Additional cross sections are added at bridges and culverts. As prescribed in the HEC-RAS Hydraulic Reference Manual4, four cross sections are associated with each hydraulic structure as follows: 4 HEC-RAS River Analysis System Hydraulic Reference Manual, United States Army Corps of Engineers Hydrologic Engineering Center, Version 3.1, November 2002 Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 16 • Cross Section 1 is placed approximately 4 times the opening width downstream of the structure. • Cross Section 2 is placed at the downstream face of the structure, just outside of the roadway embankment. • Cross Section 3 is placed at the upstream face of the structure, just outside of the roadway embankment. • Cross Section 4 is placed approximately 1 times the width of the opening upstream of structure. Cross sections were delineated from left to right looking in the downstream direction and were drawn so that each end projected beyond the maximum extent of the 500-year floodplain. Cross section stations reflect the distance in feet from confluence. 4.5 MANNING’S “n” VALUES Manning’s “n” values are empirical coefficients used to relate surface conditions to conveyance friction losses in the HEC-RAS model. Table 5-3 below shows the relationship between land cover and Manning’s “n” values. Typically, roughness coefficients used for this study were taken from the HEC- RAS Reference Manual. Table 4-3 Manning’s Roughness Coefficients Land Cover Manning's “n” Value Urban residential (high/low density) 0.060 Urban commercial 0.050 Pavement 0.013 Floodplain; no brush 0.035 Floodplain; brush and trees 0.090 Dense trees 0.11 to 0.15 Light brush and trees 0.060 Grass, no brush 0.035 Crops 0.035 4.6 BRIDGES AND CULVERTS For this study, 14 culverts were modeled in accordance with the recommended procedures outlined in the HEC-RAS Hydraulic Reference Manual and summarized below. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 17 4.6.1 Cross Sections Cross-sections 1 and 4 were located sufficiently upstream and downstream from the structure to represent undisturbed flow in the channel. Cross-section 2 was located just downstream of the bridge face outside of the roadway embankment. And finally, Cross-section 3 was located just upstream of the bridge face beyond the limits of the roadway embankment. 4.6.2 Bridge Deck / Roadway Bridge Deck/Roadway information was acquired from the topographic survey. Where survey data proved to be insufficient, the data was supplemented with information from the base mapping. 4.6.3 Modeling Approach Typically, the highest energy answer between Energy (Standard Step) and Momentum method was selected for low flow calculations. For high flow calculations, the Pressure and/or Weir method was used. As an exception, perched bridges and culverts were modeled using Energy methods. It should be noted that this approach to bridge modeling was a general philosophy, but not a hard and fast rule. The results from each bridge were evaluated, and engineering judgment was used to obtain reasonable results. 4.6.4 Internal Bridge Cross Sections As general rule, internal bridge cross sections were not modified. However, some revisions to internal cross sections may have been necessary. Specifically, when Cross Sections 2 and 3 were not cut perpendicular to the bridge face, the deck / roadway would be obscured by the cross-sections. With weir area (roadway) obscured, HEC-RAS uses the cross section points as the weir. As a result, the calculated head on the weir is often overestimated. Where this conservatism was of particular concern, the internal bridge cross section was modified so that the all of the roadway points were used for weir flow. 4.7 INEFFECTIVE FLOW AREAS Ineffective flow areas were determined using cross-section plots, contour information and photos. Ineffective flow area examples include: • Floodplain areas significantly below the top of the channel bank not hydraulically connected to the channel downstream • Floodplain areas within hydraulic shadow of roadway encroachments caused by contraction and expansion of flow through bridge or culvert openings • Floodplain areas within hydraulic shadow of other obstructions or irregularities in the stream valley floodplain 4.8 EXPANSION AND CONTRACTION COEFFICIENTS Expansion and contraction coefficients were estimated based on the ratio of effective flow area in the floodplain occurring at stream valley cross-sections, roadway crossings, and dams. Table 5-4 lists typical coefficients used in the model. For roadway crossings, expansion and contraction coefficients were applied to the first two cross-sections upstream and one cross-section downstream of the structure. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 18 Table 4-4 Expansion and Contraction Coefficients Transition Type Expansion Coefficient Contraction Coefficient Gradual 0.3 0.1 Roadway Crossing 0.5 0.3 Abrupt 0.8 0.6 Data from HEC-RAS Hydraulic Manual 4.9 FLOW DATA For this study, one-dimensional, steady state flows is used as a basis for hydraulic modeling. The peak flow rates at points of interest in the watershed are estimated using the Runoff module described in Section 4 of the report. 4.9.1 Profiles Peak flow rates from the 2, 5, 10, 25, 50, and 100-year storms were used in the hydraulic analysis. 4.9.2 Flow Change Locations At a minimum, HEC-RAS requires a flow rate to be established at the top of each reach. Theoretically, flow rates increase continuously along a reach because of lateral inflow of runoff. While it would be impossible to account for continuous increases in flow rate, it is appropriate to increase the flows at particular cross section locations. These locations in the hydraulic model are reflective of hydrograph calculations in the hydrologic model. 4.9.3 Boundary Conditions Because all of the streams modeled are controlled by the stream or river they discharge to, boundary conditions are set to normal flow conditions. 4.9.4 Flow Conditions Floodplain information was calculated for two types of land uses: existing conditions and future surface conditions as discussed in Section 3. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 19 4.9.5 Detention / Storage Because HEC-RAS is a steady state model it cannot inherently model attenuation created by ponds, lakes, and some highway embankments. Attenuated flow locations were modeled in XP-SWMM, and the results were incorporated into HEC-RAS. 4.10 FLOODWAY ANALYSIS Floodway limits were not determined as part of this study. 4.11 CALIBRATION Due to the lack of any physical data (such as gage records) indicating high water elevations for a known flow recurrence interval, true calibration (as defined in the scientific community) could not be performed. Therefore, a comparative analysis was completed using several available sources of information. 4.11.1 Previous Studies Several previous hydrologic and hydraulic studies have been performed in and around the City of Jefferson including the FEMA FIS for Cole County and the City of Jefferson. These studies were reviewed and pertinent information used. 4.11.2 Stormwater Questionnaire A stormwater questionnaire distributed in July of 2001 for Phase I of this study proved to be helpful as well. Using GIS, the results of the questionnaires could be plotted on the mapping with the floodplain. Results of the model generally corroborated the problem areas revealed by the questionnaire. Clusters of reported flooding indicated major areas of concern caused by obstructions or undersized channels. Scattered areas of reported flooding were more indicative of localized problems such as downspouts and clogged drainage systems. A thorough discussion and analysis of this survey is available in the Phase I/II study5. 4.12 QUALITY CONTROL / DEBUGGING Once the HEC-RAS models were calibrated, a final examination of the input parameters was made using the Check-RAS program distributed by FEMA (Version 1.1). According to the documentation accompanying the program: Check-RAS is a program designed to check the reasonableness of the data found in HEC-RAS. Geometric, steady flow, and output data are three types of data used to verify that hydraulic estimates and assumptions made in the model appear to be justified and are in accordance with the assumptions and limitations of the HEC-RAS program and applicable FEMA requirements. Check-RAS allows users to examine a variety of parameters from HEC-RAS data files, as well as generate, view, and print reports, which include tables and messages. Using the HELP message database can reference additional information about the messages identified. 5Burns & McDonnell, Comprehensive Stormwater Master Plan Update Phases 1 & 2, October 2003 Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 20 Although the HEC-RAS program provides several messages, CHECK-RAS differs from HEC-RAS in several ways. Only, CHECK-RAS does the following: • Categorizes floodplain modeling into five distinct areas of checks • Provides a summary table and messages for each area of check • Assesses the suitability of roughness coefficients and transition loss coefficients • Assesses the suitability of starting water-surface elevations • Assesses bridge and culvert modeling • Provides a detailed floodway analysis • Compares important parameters among multiple profiles • Proposes solutions through the use of the Help screens Each Check-RAS warning was reviewed and evaluated for applicability. Necessary changes were made to the HEC-RAS model. 4.13 Digital Models Table 4-5 HEC-RAS Models Plan Geometry Flow Description Existing Conditions Missouri River Area – Existing Conditions Existing Conditions Flow P4.p01 P4.g01 P4.f01 Model represents flows for existing land use conditions and the existing conveyance system. Future Surface Conditions Missouri River Area – Existing Conditions Future Surface Conditions Flow P4.p02 P4.g01 P4.f02 Model represents flows for future land use conditions and the existing conveyance system. Table 4-6 XP-SWMM Models Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 21 Name Study Area Description MoRiv&AlgoaEX.xp Missouri River and Algoa District Existing Conditons model for 2, 5, 10, 25, 50, and 100-year storms. MoRiv&AlgoaFU.xp Missouri River and Algoa District Future Conditons model for 2, 5, 10, 25, 50, and 100-year storms. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 22 SECTION 5.0 - EXISTING SYSTEM PERFORMANCE 5.1 Missouri River and Algoa Study Area The Missouri River and Algoa Study Area (see Exhibit 1) is made up of areas of the Missouri River watershed within the city limits, including an area identified as the Algoa Area (see Exhibit 1). Different parts of the Study Area drain to the Missouri River, Moreau River, Rising Creek, and Osage River. 5.1.1 Land Use Portions of the study area are city neighborhoods that are fully developed in residential or commercial use. These areas are along the Missouri River on either side of the Capitol Building. Although there is redevelopment occurring at the site of the old prison, the hydrologic characteristics do not change, and no changes are expected between current and future land use in these areas. Other parts are near-rural and subject to future industrial development, primarily in the Algoa Area. The Algoa Area is already home to several large industrial and several large public facilities, but these account for only about 35% of this area (about 1,250 acres)—there remains 2,300 acres available for development. Because of this, future land use for this area shows a large increase in the industrial classification with an accompanying increase in stormwater runoff. The land use classifications used to calculate the hydrologic parameters that drive this study are shown below in Table 5-1, and in Exhibits 4 and 5. Table 5-1 Land Use Breakdown for Missouri River & Algoa Study Area Land Use Designation Total Area (acres) Percent of Watershed Existing Surface Conditions (observed from aerial photography) Agricultural 2023.732.80% Brush 862.314.00% Commercial 277.64.50% High Density Residential 19.40.30% Impervious 61.61.00% Industrial 543.18.80% Low Density Residential 97.91.60% Medium Density Residential 629.610.20% Meadow & Pasture 415.26.70% Right of Way 329.55.30% Wooded 906.314.70% Table 5-1 Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 23 Land Use Designation Total Area (acres) Percent of Watershed Future Surface Conditions Commercial 575.210.30% Floodplain 1112.819.90% High Density Residential 19.40.30% Impervious 32.60.60% Industrial 2181.239.10% Low Density Residential 731.30% Medium Density Residential 753.313.50% Meadow & Pasture 29.60.50% Right of Way 278.75.00% Steep 106.11.90% Wooded 423.67.60% 5.1.2 Hydrologic Summary A summary is on the next page of the major hydrologic characteristics of the watershed. The differences between existing and future flows highlights the places in the watershed where the most development is expected, and the unit flows are a useful measure for assessing the validity of the model. The table shows the model outflows from the larger outfalls in the study area (shown in Exhibit 7). Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 24 Table 5-2 Hydrologic Characteristics of Missouri River and Algoa Study Area Total Drainage Area (ac) 7735.4 Total Drainage Area (sq mi) 12.09 Number of Subsheds Modeled 218 Average Subshed Size (ac) 35.5 SCS Composite Curve Number Existing 76.52 Future 81.68 10-year Event 100-year Event Outfall * Area (ac) Existing Future Increas e Existin g Future Increas e Peak Flow Rate (cfs) 360.15 363.43 639.92 647.29 1 200.72 Unit Discharge (cfs/ac) 1.79 1.81 0.9% 3.19 3.22 1.2% Peak Flow Rate (cfs) 233.12 235.57 376.03 381.79 2 88.24 Unit Discharge (cfs/ac) 2.64 2.67 1.1% 4.26 4.33 1.5% Peak Flow Rate (cfs) 380.126379.596678.68 678.541 3 140.09 Unit Discharge (cfs/ac) 2.71 2.71 -0.1% 4.84 4.84 0.0% Peak Flow Rate (cfs) 185.19 195.17 339.83 356.91 4 206.81 Unit Discharge (cfs/ac) 0.90 0.94 5.4% 1.64 1.73 5.0% Peak Flow Rate (cfs) 332.24 548.92 472.42 754.04 5 286.72 Unit Discharge (cfs/ac) 1.16 1.91 65.2% 1.65 2.63 59.6% Peak Flow Rate (cfs) 1465.26 2226.04 2433.64 3270.33 6 5119.00 Unit Discharge (cfs/ac) 0.29 0.43 51.9% 0.48 0.64 34.4% Peak Flow Rate (cfs) 349.92 651.35 580.87 994.06 7 515.33 Unit Discharge (cfs/ac) 0.68 1.26 86.1% 1.13 1.93 71.1% *See Exhibit 7 5.1.3 Existing Drainage System Within this Study Area there are 12 hydraulic structures modeled in HEC-RAS and 181 'links' (culverts or pipe runs) modeled in XP-SWMM. These links comprise about 4.7 miles of stormwater conduits 24 inches and larger. The link names do not correspond exactly with the surveyed conduit names because of modeling constraints. Therefore the GIS and XP-SWMM files furnished to the City and County must sometimes be used to find the locations and statistics associated with each. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 25 5.2 EVALUATION CRITERIA The design criteria for system performance currently observed by the City of Jefferson is based on land use or zoning. These criteria have been taken from the Storm Drainage Design Manual6 and are as follows: Table 5-3 – Existing Design Criteria for Enclosed Systems and Culverts Land Use / Zoning Designation Return Frequency the System Must Accommodate Residential 10 yr Commercial 25 yr Industrial 25 yr Government and Institutional 25 yr Floodway in 100-yr Floodplain 100 yr Table 5-4 – Existing Design Criteria for Open Channels Land Use / Zoning Designation Return Frequency the System Must Accommodate Residential 25 yr Commercial 25 yr Industrial 25 yr Government and Institutional 25 yr All Others 10 yr Floodway in 100-yr Floodplain 100 yr For various reasons these design criteria cannot be the sole criteria for evaluating the system. Much of this study examines older elements of the stormwater conveyance system as well as portions of it that are outside the City limits and were not subject to City regulation when built. In addition, these are design criteria, meant to be applied to new construction. Hence evaluating the performance of the system is more complicated than simply flagging elements that do not pass the runoff from the applicable event. 5.3 DRAINAGE SYSTEM PERFORMANCE The drainage system was evaluated as two separate parts: enclosed system and open channels. An enclosed system was defined as multiple, connected pipes. As such, all of the elements considered as enclosed systems were in the upper reaches of the watersheds and were modeled in XP-SWMM. These enclosed systems then discharged into open channels and were modeled in HEC-RAS. This combination of modeling techniques was used because XP-SWMM models enclosed systems better than HEC-RAS, and HEC-RAS better represents extended open channel systems. 6 Storm Drainage Design Manual, Public Works Department, City of Jefferson, Missouri, 1985. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 26 5.3.1 Major Structure Modeling Results from HEC-RAS Table 5-5 summarizes the major structures analyzed in the Missouri River Study Area with HEC-RAS. The table provides a brief description of the structure, its length and a listing of the hydrologic conditions examined. “Existing” indicates the flow at each structure with the current ground cover and land uses observed in the watershed. “Future” is the future flow predicted to occur as the watershed develops. The table also provides an indication of whether modeling predicts overtopping of the structure for three key runoff events. These structures can be located in Exhibit 6 and the results can be examined more closely in the HEC-RAS model digital files furnished with this report. The City's design criteria require that structures in residential streets convey a 10-year event without overtopping. Bridges and culverts on commercial streets must convey a 25-year event without overtopping. Table 5-5 HEC-RAS Analysis of Major Structures 10-yr Event 25-yr Event 100-yr Event Struct . No. City or County Descriptio n (dimension in feet) Lengt h (ft) Hydrologi c Condition Flow (cfs) Overto p (ft) Flow (cfs) Overto p (ft) Flow (cfs) Overto p (ft) Existing 151 0 171 0 215 0.29 ME- 002 City, commercial 6.0 CMP 22 Future 335 0.53 395 0.62 499 0.75 Existing 165 0.38 193 0.67 239 1.01 ME- 003 City, commercial 6.0 CMP 140 Future 358 1.56 424 1.77 531 2.05 Existing 1407 0 1807 0 2539 0 ME- 005 City, commercial 2 - 12.0 x 18.0 RCB 720 Future 1515 0 1923 0 2706 0 Existing 1407 0 1803 0 2524 0 ME- 006 City, commercial 2 - 15.0 x 12.0 RCB 464 Future 1512 0 1918 0 2691 0 Existing 457 0 561 0 769 0 ME- 007 City, commercial 8.0 x 7.0 RCB 168 Future 666 0 776 0 941 0 Existing 1457 0 1858 0 2548 0 ME- 008 City, commercial Bridge 12 wide Future 1557 0 1966 0 2683 0 Existing 220 0 453 0 584 0 ME- 009 City, commercial 8.0 x 8.0 RCB 117 Future 510 0 591 0 692 0 Existing 1481 0 1864 0 2532 0 ME- 010 City, commercial Bridge 23' wide Future 1766 0 2029 0 2664 0 Existing 1508 0 1888 0 2556 0 ME- 011 City, commercial 2 - 15.0 x 12.0 RCB 109 Future 1810 0 2131 0 2697 0 Existing 1551 0 1910 0 2578 0 ME- 012 City, commercial Bridge 28' wide Future 2247 0 2643 0 3305 0 Existing 187 0 237 0 342 0 ME- 013 City, commercial 7.0 x 7.0 RCB 107 Future 193 0 244 0 352 0 Existing 364 0 460 0 647 0 ME- 014 City, commercial 10.0 x 23.0 Stone Arch 50 Future 364 0 460 0 647 0 Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 27 The analysis suggests that the following structures lack sufficient capacity to current design standards: • ME-002 goes under a dirt road that provides access below the Algoa landfill west of Shamrock Road • MR-003 is under a dirt road that provides access to the fields west of Shamrock Road and south of Algoa Road. 5.3.2 Minor Structure Modeling Results - Surcharging The performance of the pipes that make up the minor systems is reported in Appendix B and in the GIS and XP-SWMM files furnished digitally with this report. In Appendix B the occurrence and depth of overtopping and the time of surcharging in minutes is reported. The locations of these pipes are shown in Exhibit 8 and the GIS files. 5.3.2.1 Overtopping The depth of overtopping was determined by modeling an aboveground channel above each pipe so that runoff was allowed to travel downstream when pipe capacities were exceeded. Four types of overland channels were modeled: street and gutter flow; flow over a sag in the road above a culvert; flow between houses through a side yard swale; and the flow through backyard swales. The overtopping elevation, the slope, and the sides of each of these trapezoidal channels is estimated for each different type and location. Due to the accuracy and resolution of elevations and topographic data these overland channels and depths only approximate actual conditions, but are still useful measures of performance. The model suggests that six percent of the links fail to pass the existing 10-year flow without overtopping, and in the future conditions scenario ten percent will overtop. 5.3.2.2 Surcharging Surcharging is an important parameter to examine when evaluating the capacity of stormwater systems, but it is not a completely straightforward process to obtain or to report. Broadly speaking, surcharging occurs when a pipe begins to run full, so the overland flow reported in Appendix B indicates surcharging. However it is also useful to report the amount of time that a pipe is in the surcharged condition. If a pipe is surcharged for an hour, then it presents a quite different warning flag than one that is only surcharged for a few minutes. In order to measure this in XP-SWMM the overland links are removed and the duration of surcharging is directly reported. The weakness of this model is that without the overland path, the water can remain at a node when it could be traveling downstream, so the succeeding channels and pipes do not receive the same peak flows as they do in the more complete model. The statistics reported from this model are length of surcharged time for ten-year and twenty-five-year events for existing and future conditions. Both overland depth and duration of surcharging are reported in Appendix B and in the GIS database files associated with those links. Additional information is available directly from the XP-SWMM model, such as animated graphics and more technical measures. Exhibit 8 shows the surcharged pipes. However, the elements shown as surcharged are only those that meet the following criteria: if residential, Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 28 they have more that 0.5 feet of depth at either end of the overland channel or are surcharged for more that 30 minutes in the 10-year event. If commercial or industrial, then they must have more than 0.5 feet of depth at either end or surcharge for more than 30 minutes in the 25-year event. These threshold parameters are somewhat arbitrary and are only for the purposes of graphic representation in the exhibit. It should be noted that there are elements that report a depth of flow in the overland channel (from the first model), but do not show a surcharged time (from the second model). This apparent inconsistency occurs because not all of the water is transmitted downstream at the same time in both models, so peak flows, depths, and times are not expected to match perfectly. The recommendations made in Section 6 factor in field investigations by the Engineer, complaints, staff feedback, special conditions, and the age and condition of the system; hence these surcharge statistics simply offer a fuller picture of the performance of the minor system. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 29 SECTION 6.0 - RECOMMENDATIONS 6.1 INTRODUCTION The recommendations made in this section are generated from a combination of model results, observations (Engineer, City, County, and Surveyor), and reports from City officials and citizen questionnaires. Most of these recommendations are structural and are intended to fix problems that already have some urgency with respect to structure flooding, erosion, or street flooding. Some of these have arisen because of the aging infrastructure and associated problems. There are other issues that exist because of the increasing urbanization in the watersheds, both from increased runoff and floodplain encroachment. Also noted in this section are sites that are currently at or beyond their capacity, but for which no recommendation is made for improvement. These sites are either recently constructed or are on private or State property. They do not appear to be safety hazards nor do they place occupied buildings at risk. 6.2 SURVEYOR'S OBSERVATIONS The need for maintenance of each surveyed structure was noted by the Surveyor. A numerical rating of 1 (no maintenance), 2 (routine maintenance), or 3 (critical maintenance) was given to each structure. Comments were appended to about half of the structures (although many comments concerned connections or structural details) in the GIS database, and one or more digital photographs are available for examination for each structure. It should be noted that because the Surveyors examined only portions of the system visible from aboveground, and because their ratings may not agree with the ratings of an experienced maintenance person, then the Surveyors' judgment of "no maintenance" may not be meaningful in all cases. The structures that received a numerical rating of 2 or 3 are shown below in Table 6-1: Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 30 Table 6-1 Surveyors Maintenance Comments Node ID Type of Maintenance Surveyor's Comments MZ57007 3 Pipe is over 1/2 filled with concrete. MZ57045 3 Channel & pipe are extremely clogged MZ57046 3 Pipe is half full of debris MZ57541 3 Manhole cover is broken MZ57563 3 Pipe has been silted over ME58065 3 P-3 is smashed & full of mud, area around is a sink hole ME58513 3 Silted in MZ57011 2 Bottom is showing rust MZ57012 2 Bottom is showing rust MZ57015 2 (none) MZ57016 2 Pipe out of ground MZ57017 2 Looks like where pipe pi's MZ57075 2 (none) MZ57570 2 Needs to be cleaned MZ57582 2 (none) ME58005 2 Ditch need to be cleaned out to uncover pipe ME58015 2 Structure need to be cleaned out ME58040 2 Ditch needs to be cleaned out MZ57530 2 Pipe is underwater MZ57576 2 Needs to be opened up ME58066 2 Area around box is collapsing in MZ57l061 2 Pipe is blocked 6.3 EVALUATION OF PRIORITIES 6.3.1 Methodology The improvements suggested as part of this study will be discussed and ranked based on the estimated level of service, potential flooding, frequency of flooding, and engineering judgment. Rather than a numerical ranking suggesting an order for which improvements should be made, a ranking of high, medium, low, or future priority will be used to prioritize the projects. This will provide the City the flexibility to evaluate and fund projects as the need arises. 6.3.2 Priority Definitions 6.3.2.1 HIGH Priority A HIGH priority is assigned to those areas meeting one of the following: Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 31 • Habitable buildings are located in the floodplain and flooding is frequent. • Flooding could pose an immediate threat to public safety. • Opportunities for proactive, non-structural measures will be lost if not initiated expeditiously. 6.3.2.2 MEDIUM Priority A MEDIUM priority is assigned to those areas meeting all of the following criteria: • There is a flooding problem that does not involve a habitable building located in the floodplain. • There is a flooding problem that does not pose an immediate threat to public safety. • The required level of service for a bridge or culvert on a major roadway is expected to be exceeded. 6.3.2.3 LOW Priority A LOW priority is assigned to those areas meeting either of the following criteria: • The required level of service for a bridge or culvert on a minor roadway is expected to be exceeded. • A stormwater issue exists due to erosion or yard flooding. 6.3.2.4 FUTURE Priority A FUTURE priority is assigned to the areas meeting one or all of the following: • Modeling indicates no flooding problem for existing conditions. • Modeling indicates a possible problem (generally a decrease in the level of service) as the upstream tributary area becomes urbanized. • A low water crossing exists in an area subject to increasing urbanization and its eventual replacement should be considered. 6.3.2.5 REVIEW During Future Development There are parts of the system that exhibit surcharging (pipe-full or bank-full flow) or minimal overland flow, but are not a hazard. However, these areas may be sensitive to upstream development or degradation of the system, and are included in the Recommendations section of the report and are meant to serve as warning flags for future planners. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 32 A REVIEW DURING FUTURE DEVELOPMENT priority is assigned to the areas meeting all of the following: • The system is surcharging in this location. • There is no hazard to occupied dwellings. • There is little or no degradation in the level of service of roadways. 6.4 Cost Opinions for Projects In the following recommendations a cost opinion is included with most projects. An attempt was made to present realistic costs in 2005 dollars. The costs of concrete and steel have both risen considerably in the last year, and it is impossible to predict what they will happen to these prices in the future. The costs of RCP and structural concrete were estimated generously, and to arrive at these numbers, it was assumed that demolition of existing structures would be required, that additional excavation and hauling, bedding, backfill, compaction, finish grading, seeding, and purchase and transportation of the pipe or RCB. Judgments were made for traffic control and utility relocation, and a healthy contingency amount was added to each estimate. The estimated cost to Remove and Replace portions of the roadway so that culverts can be installed includes pavement removal and disposal; new base material, grading and compaction; curbs and gutters; and 6” of asphalt concrete. The estimates and projections prepared by Burns & McDonnell relating costs are based on our experience, qualifications and judgment as a professional consultant. Because Burns &McDonnell has no control over weather, cost and availability of labor, material and equipment, labor productivity, construction contractor's procedures and methods, unavoidable delays, construction contractor's methods of determining prices, economic conditions, government regulations and laws (including the interpretation thereof), competitive bidding or market conditions and other factors affecting such estimates or projections, Burns & McDonnell does not guarantee that actual rates, costs, performance, schedules, etc., will not vary from the estimates and projections prepared by Burns & McDonnell. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 33 6.5 PROJECT 1 – Main St. & Circle Dr. (City Project) 6.5.1 Description There is severe damage from flooding reported at the second house on Circle Drive (see Figure 6-1). There are two houses located in a local sump, and about 15 acres drains through this small system. A 24- inch pipe transitions to a 20-inch pipe which feeds larger downstream pipes. At this transition (to the smaller pipe), there is a grated drop inlet in the complainant's back yard, and this makes these residences susceptible to flooding from the grate inlet whenever the pipes surcharge. In the 25- event, this surcharging lasts for about an hour. There is no hydraulic problem with the downstream infrastructure. The 20-inch pipe opens up to a 3-foot x 2.7-foot, then a 4-foot x 3-foot box culvert, and then a 360-foot long run of 3.5-foot corrugated metal pipe that discharges into an open channel. However, it is reported that the inlet on the east side of Circle Drive is caving in. The basic problem is that there is an opening for water to leave the system in a sump and the next pipe downstream from this grate inlet is undersized. 6.5.2 Recommended Improvement The backyard inlet (MZ57545), and inlets on both sides of Circle Drive (MZ57075 and MZ57074) should be replaced. The 20-inch pipe (MZ65) should be upsized to a 24-inch pipe, and the pipes connecting the street inlets (MZ64) and the junction box (MZ63) can also be replaced with 24-inch pipes. The pipes and inlets along Main Street appear to be properly sized and should not have to be replaced. However there is a buried junction (MZ57073) leading to a steep slope into the backyards that will have to be examined in the design phase of this project. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 34 6.5.3 Cost Opinion Description Quan. Unit Unit Price Total Cost Main St. & Circle Dr. Remove Existing Pipe 190 LF $10.50 $1,995 Excavation 426 CY $4.92 $2,096 Bedding 64 CY $40.00 $2,560 Material to be hauled off site 39.2 CY $9.70 $380 Backfill and compaction 341 CY $28.15 $9,599 RCP 24" 190 LF $25.00 $4,750 Inlet Structures 4 EA $5,090.00 $20,360 R&R Pavement 69.2 SY $43.00 $2,976 Finish Grading 570 SY $4.00 $2,280 Hydromulching 5100 SF $0.44 $2,244 Subtotal $49,240 Erosion Control 2 % $985 Mobilization / Demobilization 5 % $2,462 Traffic Control 2 % $985 Utility Relocation 2 % $985 Subtotal $54,656 Contingency 25 % $12,310 Construction Total $66,966 Engineering, Surveying, Geotechnical, Permitting & Construction Management 50 % $33,483 PROJECT TOTAL $100,44 9 6.5.4 Priority A HIGH priority is assigned to this project because of the history of home flooding. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 35 6.6 PROJECT 2 – High Street & Benton Street (City Project) 6.6.1 Description There are reports of house flooding, yard flooding, street flooding, and erosion problems in this neighborhood (see Figure 6.2). The modeling suggests that there is surcharging and overland flow due to undersized pipes throughout the system. 6.6.2 Recommended Improvement To correct the problem the modeling suggests that the upper part of this small system (the pipes labeled MZ33, MZ34, and MZ20) could be replaced with 30-inch pipes to adequately increase capacity. In the lower part the pipes labeled MZ35 and MZ36 are currently 24-inch and 36-inch diameter pipes, and could be replaced with 42-inch pipes. It should be noted that the smaller, collector pipes that also comprise the system but were not analyzed in detail will need to be examined for inclusion in this project. 6.6.3 Cost Opinion Description Quan. Unit Unit Price Total Cost High St. & Benton Dr. Remove Existing Pipe 843 LF $12.98 $10,942 Excavation 2546 CY $4.92 $12,526 Bedding 527 CY $40.00 $21,080 Material to be hauled off site 273 CY $9.70 $2,651 Backfill and compaction 1828 CY $28.15 $51,458 30" RCP 679 LF $40.20 $27,296 42" RCP 164 LF $58.90 $9,660 Inlet Structures 5 ea $5,090 $25,450 R&R pavement 366 SY $43.00 $15,738 Finish Grading 2680 SY $4.00 $10,720 Hydromulching 24150 SF $0.44 $10,626 Subtotal $198,147 Erosion Control 2 % $3,963 Mobilization / Demobilization 5 % $9,907 Traffic Control 3 % $5,944 Utility Relocation 5 % $9,907 Subtotal $227,869 Contingency 25 % $56,967 Construction Total $284,836 Engineering, Surveying, Geotechnical, Permitting & Construction Management 20 % $56,967 PROJECT TOTAL $341,804 Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 36 6.6.4 Priority A HIGH priority is assigned to this project because of complaints and the potential for structure flooding in several places. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 37 6.7 PROJECT 3 – Allen Drive (City Project) 6.7.1 Description The modeling suggests that there is substantial overland flow in both the existing and future 10-year storm events (see Figure 6-3). Damage to property is problem for at least one homeowner, but depths of water in Allen Court and Cole Drive could be hazardous. According to the stormwater survey, yard flooding and street flooding occur frequently in this area. 6.7.2 Recommended Improvement According to the model, all of the surcharging and overland flow can be eliminated if two downstream pipes (MZ67 and MZ69, currently 30-inch and 36-inch pipes) are replaced with 42-inch pipes. There is nothing reported by the Surveyor with respect to condition, so if the rest of the pipes and inlets are in satisfactory condition, then this partial replacement of the system should solve the problem. 6.7.3 Cost Opinion Description Quan. Unit Unit Price Total Cost Allen Dr. Remove Existing Pipe 357 LF $13.27 $4,737 Excavation 1428 CY $4.92 $7,026 Bedding 370 CY $40.00 $14,800 Material to be hauled off site 81 CY $9.70 $786 Backfill and compaction 926 CY $28.15 $26,067 42" RCP 357 LF $59.00 $21,063 Inlet structure 1 EA $5,090.00 $5,090 Outlet structure 300 SF $10.00 $3,000 Finish Grading 1520 SY $4.00 $6,080 Hydromulching 13700 SF $0.44 $6,028 Subtotal $82,569 Erosion Control 2 % $1,651 Mobilization / Demobilization 3 % $2,477 Traffic Control 1 % $826 Utility Relocation 5 % $4,128 Subtotal $91,651 Contingency 25 % $22,913 Construction Total $114,564 Engineering, Surveying, Geotechnical, Permitting & Construction Management 15 % $17,185 PROJECT TOTAL $131,749 Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 38 6.7.4 Priority A MEDIUM priority is assigned to this project because of the depth of street flooding. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 39 6.8 PROJECT 4– Delta Place & Riverwood Drive (City Project) 6.8.1 Description At the upstream end of this small system there is a 4 foot x 4 foot box culvert (MZ57) with a collapsed inlet. The box culvert empties into a 15 foot long improved open channel (MZ117) that leads to a 30 inch corrugated metal pipe (MZ56). Modeling predicts that this last link surcharges in the 10-year event and that the stormwater flows overland during events greater than the 25-year storm. However modeling may not be predicting the true extent of the problem as the homeowner on the east side of this small system reports yard flooding more than ten times in ten years, and water has gotten into the house through a low walkout door on the back side of the house. This excessive flooding is probably due to the obstructed box culvert and the lack of a well defined swale that would convey the water downstream. 6.8.2 Recommended Improvement This small system should be replaced from the uphill inlet to the far side of Delta Place with 36 inch pipe. This will give the City an opportunity to bury the open channel portion of the system, establish an inlet with proper elevation, headwall, and grading, and provide a side yard swale so that it can handle flow when the system becomes obstructed or when larger storms than the design storm occur. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 40 6.8.3 Cost Opinion Description Quan. Unit Unit Price Total Cost Delta Place Remove Existing Pipe 230 LF $14.05 $3,232 Excavation 774 CY $4.92 $3,808 Bedding 174 CY $40.00 $6,960 Material to be hauled off site 48 CY $9.70 $469 Backfill and compaction 540 CY $28.15 $15,201 36" RCP 230 LF $50.50 $11,615 Inlet structure 3 ea $5,090.00 $15,270 Finish Grading 816 SY $4.00 $3,264 Hydromulching 7350 SF $0.44 $3,234 Subtotal $63,052 Erosion Control 5 % $3,153 Mobilization / Demobilization 1 % $631 Traffic Control 2 % $1,261 Utility Relocation 2 % $1,261 Subtotal $69,357 Contingency 25 % $17,339 Construction Total $86,697 Engineering, Surveying, Geotechnical, Permitting & Construction Management 10 % $8,670 PROJECT TOTAL $95,366 6.8.4 Priority A LOW priority is assigned to this project because the problem is primarily yard flooding. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 41 6.9 PROJECT 5 – State Street & Marshall Street (City Project) 6.9.1 Description The modeling suggests that this system exceeds the desired capacity for events greater than the 10-year storm event, as indicated by surcharging (see Figure 6-5), however no complaints have been reported. This would not necessarily be a problem, except that there is no alternative pathway for water to drain from the site. There is a difference of about twelve feet between the elevation of State Street and the area drain in this sump, but only about two feet of elevation before ponding water can enter the basement of the warehouse. 6.9.2 Recommended Improvement This site is sensitive to obstruction from silt and debris and should be inspected regularly. 6.9.3 Priority A REVIEW DURING FUTURE DEVELOPMENT priority is assigned to this project because the system is surcharging in this location. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 42 6.10 PROJECT 6– Algoa Area (City Project) 6.10.1 Description Surcharging occurs in the 25-year event at a number of locations in the Algoa area. Most of these sites are private or state owned facilities and were not subject to City regulation when they were built. See Figure 6-6, or see Exhibits 8B and 8C for a larger view of these sites. 6.10.2 Recommended Improvement Future development should not add any demand to these conveyances that are already at or beyond their capacities. 6.10.3 Priority A REVIEW DURING FUTURE DEVELOPMENT priority is assigned to this project because the system there is surcharging in this location. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 49 SECTION 7.0 - GLOSSARY OF TERMS 7.1 DEFINITIONS 10-year Event - An event (such as rainfall or runoff) having a 10% (1/10) probability of being exceeded in any given year. 25-year Event - An event (such as rainfall or runoff) having a 4% (1/25) probability of being exceeded in any given year. 50-year Event - An event (such as rainfall or runoff) having a 2% (1/50) probability of being exceeded in any given year. 100-year Event - An event (such as rainfall or runoff) having a 10% (1/100) probability of being exceeded in any given year. Design Criteria - Guidelines upon which planning and engineering decisions and judgments are based. Design Storm - A precipitation event that, statistically, has a specified probability of occurring in any given year (expressed either in years or as a percentage). Detention Facility - Any structure, device or combination thereof, that functions to accept inflow from surface runoff and discharge it at a controlled rate less than the peak inflow rate. Development - Any activity that alters the surface of the land that generally creates additional impervious surfaces including, but not limited to, pavement, buildings and structures. Drainage - Interception, collection and removal of excess stormwater from an area into another area or into a receiving water body. Enclosed Drainage System - A drainage system consisting of essentially continuous pipes and/or box culverts below the ground surface. Erosion - The removal of soil particles by the action of flowing water. Excess Runoff - Direct surface runoff that cannot be accommodated satisfactorily by the existing or planned drainage system. Flood Control - Preventing the entry of stormwater into an area from another area, or from a stream or other water body. Floodplain - The area surrounding a watercourse that is inundated with floodwater. Flood Routing - An analytical technique used to compute the effects of system storage and system dynamics on the shape and movement of a flood wave. Floodway - A tool or concept used by local communities for flood plan management. The area of the 100-year flood plain is divided into a floodway and floodway fringe. The floodway is the Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 50 channel of the stream plus any adjacent flood plain areas that must be kept free of encroachment to that the 100-year flood can be carried without substantial increases in flood height. Minimum Federal standards limit such increases to 1.0 foot, provided hazardous velocities are not exceeded. Freeboard - The vertical difference in elevation between the hydraulic gradient and a referenced point. Examples are the difference between the maximum water surface level behind a dam and the top of a dam, or the difference in elevation between the water surface at a culvert beneath the roadway and the surface of the roadway. Head - The difference in depth of a liquid at two given points; a depth generally expressed in feet. HEC-RAS - United States Corps of Engineers Hydrologic Engineering Center’s program for modelling water surface profiles in open channels, River Analysis System. Hydraulic Gradient - The elevation of the surface of the water in the drainage system at any point. Hydrograph - A graph of runoff rate, inflow rate or discharge rate, versus time. Hydrologic Soil groups - A soil characteristic classification system defined by the U.S. Soil Conservation Service in which a soil may be categorized into one of four soil groups (A, B, C, or D) based upon infiltration rate and other properties. Impervious Surface - Any surface that does not readily permit water to infiltrate. Examples are roofs and concrete or asphalt-paved surfaces. Improved Channel - Any channel whose characteristics are changed by either grading or construction of lining materials. Interception - Rainfall that is caught by foliage, branches, leaves, and other aboveground objects. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 51 Lag - The time interval from the center of mass of excess rainfall to the peak rate of runoff. Level of Service - The return period for which a drainage system, or an individual element of that system, has adequate hydraulic capacity. Master Planning - A “systems” approach to the planning of facilities, programs and management organizations for comprehensive control and use of stormwater within a defined geographical area. Natural Channel - An existing channel that has not been appreciably altered by grading, lining or changing its course. Open System - A drainage system consisting of open channels, either natural or improved, with only comparatively short lengths enclosed by pipes or culverts. Pervious Surfaces - Surfaces that absorb water such as undeveloped areas, fields, yards and other unpaved areas. Reach - A specific length of the storm drainage system between two points. For example, a reach may consist of a single culvert or may consist of several connected pipes or channel sections. The term "line" may also be used synonymously within the report. Receiving Waters - Streams, lakes, bays, etc., into which stormwaters are discharged. Return Period - A statistical term for the average frequency that a given event may be expected to occur, although it does not imply that the event will occur regularly at even intervals. It can also be defined as the reciprocal of the probability of an event. For example, a storm having a 10-year return period statistically can be expected to occur once in a period of 10 years, a probability of occurrence of 0.10, or 10%. However, the event may occur at any time, and two such events may actually occur on successive days. Sediment - Soil particles eroded by flowing water; either in suspension in that water or as deposited. Storm Drainage System - Natural or constructed facilities and appurtenances, such as ditches, natural channels, pipes, culverts, bridges, improved channels, street gutters, inlets and detention facilities, which serve to collect and convey surface drainage. Storm Sewers - Usually, enclosed conduits that transport excess stormwater runoff toward points of discharge (sometimes call “storm drains”). Stormwater Management - Encompasses both “control” and “developmental” activities in which there is physical interaction with stormwater (a broader interpretation includes activities of an institutional nature – financing, staffing, etc.). Stormwater Storage - Temporary storage of excess runoff on, below, or above the surface of the earth for the purpose of attenuating excess runoff. Time Of Concentration - The time period necessary for surface runoff to reach the outlet of a sub- basin from the hydraulically most remote point in the tributary drainage area. Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 52 Travel Time - The sum of the time intervals for overland flow, sewer or gutter flow, and pipe and channel flow from the hydraulically most remote point in the tributary to the discharge point of interest. Watershed - All land draining to the storm drainage system at any given point. This term is used synonymously with the terms tributary area, drainage area, drainage basin, catchment area, subwatershed and subarea. Water Surface Profile (Existing) - the “Existing” water surface profiles represent flooding conditions based on current land use conditions within the study area. Water Surface Profile (Future) - the “Future” water surface profiles represent flooding conditions based on future land use conditions within the study area. 7.2 ACRONYMS APWA - American Public Works Association cfs – Cubic feet per second CMP - Corrugated metal pipe CMPA – Corrugated metal pipe arch DTM - Digital Terrain Model EPA – Environmental Protection Agency FEMA - Federal Emergency Management Agency FIS - Flood Insurance Study GIS - Geographic Information System HEC – Hydrologic Engineering Center (U.S. Army Corps of Engineers) MDNR – Missouri Department of Natural Resources MoDOT – Missouri Department of Transportation NFIP - National Flood Insurance Program RCB – Reinforced Concrete Box RCP – Reinforced Concrete Pipe SWMM – Storm Water Management Model Missouri River and Algoa Study Area Stormwater Master Plan City of Jefferson, Missouri November 18, 2005 53 TIN - Triangulated Irregular Network USACE - Unites States Army Corps of Engineer