APPENDIX 3 TECHNICAL MEMORANDUM NO. 3 – CONCEPTUAL DRAINAGE REPORT 091337118 Final Report and Executive Summary 2008-046, TT005 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study June 2010 Hidden V/aters Parkrvay Corridor Feasibility Study V/atermelon Road to Interstate 10 Contract No.: 2008-046 Work Order No.: T.1005 FINAL Technical Memorandum No.3 Conceptual Drainage Report Prepared by: 7f1t1 \ \I7 Nm¡ey'ñom Ag¡ociatrs. lnc. ad February 2010 0913371 18 Copydght@ 2010, KimÞy-Hom and Associates, lnc. lx¡ro: tlr,fartt TABLE OF CONTENTS FINAL – CONCEPTUAL DRAINAGE REPORT 1. INTRODUCTION .................................................................................................................................. 1 1.1 Study Background ..................................................................................................................... 1 1.2 Project Study Area..................................................................................................................... 2 1.3 Document Purpose and Scope................................................................................................... 2 1.4 Design Drainage Criteria .......................................................................................................... 2 1.5 Drainage Studies ........................................................................................................................ 4 1.5.1 Previous Drainage Studies - Southern Region.................................................................. 4 1.5.2 Previous Studies – Gillespie Dam and Gillespie Dam Bridge .......................................... 6 1.5.3 Previous Drainage Studies - Central Region .................................................................... 6 1.5.4 Previous Drainage Studies - Northern Region ................................................................. 7 1.5.5 Future Drainage Study ..................................................................................................... 7 2. EXISTING LAND USE .......................................................................................................................... 9 3. EXISTING WATERSHED FEATURES ................................................................................................. 10 3.1 Southern Region: Drainage South of the Gila River ........................................................... 10 3.1.1 Gila Bend Canal Watershed ........................................................................................... 10 3.1.2 Rainbow Wash Watershed .............................................................................................. 12 3.2 Central Region: Gila River Crossing ..................................................................................... 13 3.3 Northern Region: Drainage North of the Gila River ............................................................ 13 3.4 Soils ........................................................................................................................................... 14 3.5 Regulatory Floodplains ........................................................................................................... 16 3.6 Potentially Impacted Drainage Structures ............................................................................ 16 3.6.1 Structures along SR 85.................................................................................................... 16 3.6.2 Structures along I-10 and the UPRR .............................................................................. 16 3.6.3 Gila Bend Canal Siphons ................................................................................................ 16 3.6.4 Gillespie Dam Bridge ..................................................................................................... 16 3.6.5 Gillespie Dam ................................................................................................................. 18 3.7 Sedimentation ........................................................................................................................... 19 3.8 Geology ..................................................................................................................................... 19 4. EXISTING HYDROLOGY ................................................................................................................... 21 4.1 4.2 4.3 Gila Bend Canal Floodplain Watershed – Southern Region ............................................... 21 Lower Centennial Wash Watershed – Central Region ........................................................ 22 Luke Wash Watershed – Northern Region ........................................................................... 23 5. SUMMARY AND CONCLUSIONS ........................................................................................................ 24 6. REFERENCES .................................................................................................................................... 25 091337118 Technical Memorandum No. 3 Conceptual Drainage Report i Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 TABLE OF CONTENTS FINAL – CONCEPTUAL DRAINAGE REPORT LIST OF FIGURES Figure 1 – Project Study Area .................................................................................................................... 3 Figure 2 – Area Drainage Studies .............................................................................................................. 8 Figure 3 – Soils ........................................................................................................................................ 15 Figure 4 – Floodplains.............................................................................................................................. 17 Figure 5 – Flood Hazards Map ................................................................................................................. 20 LIST OF TABLES Table 1 – Soil Type Characteristics ......................................................................................................... 14 Table 2 – Summary of Offsite Hydrology Resources .............................................................................. 22 LIST OF APPENDICES Appendix TM3-1. Field Documentation Appendix TM3-2. Potentially Impacted Drainage Structures Appendix TM3-3. Supporting Hydrologic Documentation 091337118 Technical Memorandum No. 3 Conceptual Drainage Report ii Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 1. INTRODUCTION Technical Memorandum No. 3 (TM 3), entitled Conceptual Drainage Report, identifies and summarizes the existing drainage conditions, features, and hydrologic characteristics within the project study area for the Hidden Waters Parkway Corridor Feasibility Study. Offsite concentration points and flow magnitudes prepared in previous studies and reports within the project study area for the 50-year and the 100-year storm events were compiled and are presented in this report. TM 3 is based on initial data gathering; a review of available existing information including previous drainage master plans and studies; roadway drainage reports; and field observations. Additional detailed information is included in the following companion documents: Existing and Future Corridor Features (TM 1), Environmental Overview (TM 2), Development and Evaluation of Candidate Alternative Alignments (TM 4), and Detailed Preferred Alignment (TM 5). 1.1 Study Background In July 2008, the Maricopa Association of Governments (MAG) completed the Interstate 10/Hassayampa Valley Transportation Framework Study (known as the Hassayampa Framework Study), which recommended a comprehensive roadway network to meet the future traffic demands that result when the area west of the White Tank Mountains is completely developed (hereafter referred to as buildout travel demand). This long-range regional transportation network included the “Arizona Parkway” as a new facility type to supplement more traditional roadway classifications in meeting projected travel demand within the study area. The Arizona Parkway utilizes a distinct intersection treatment that prohibits left-turns at major cross-street intersections and controls all traffic movements with simple two-phased signal control. Left-turn movements are made indirectly using directional left-turn crossovers immediately downstream of the crossroad intersection. A north-south Arizona Parkway known as the Hidden Waters Parkway was demonstrated to be needed in the Hassayampa Framework Study that generally is offset about two miles to the west of the Hassayampa River. The northern portion of the Hidden Waters Parkway is proposed to cross Interstate 10 at 339th Avenue (where a traffic interchange already exists) and extend southward to Old U.S. Highway 80 (Old US 80). Similar to the Hassayampa Framework Study, the Interstate 8 and Interstate 10 Hidden Valley Transportation Framework Study (known as the Hidden Valley Framework Study), completed by MAG in October 2009, indicates the need for a system of Arizona Parkways to meet the future buildout travel demand for the area southwest of Interstate 10 (I-10) and north of Interstate 8 (I8). In the Hidden Valley Framework Study, the need was demonstrated for the Hidden Waters Parkway identified previously in the Hassayampa Framework Study to extend further south, generally following the Old US 80 alignment, to Watermelon Road in Gila Bend. In May 2009, the Maricopa County Department of Transportation (MCDOT) retained KimleyHorn and Associates, Inc. (KHA) to conduct a corridor feasibility study for the southern portion of the Hidden Waters Parkway between Watermelon Road and I-10. 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 1 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 1.2 Project Study Area The project study area for the proposed Hidden Waters Parkway is approximately 38 miles in length between Watermelon Road and I-10 and is roughly two miles wide, centered on the northsouth segment of Old US 80. North of the Cactus Rose Road/Old US 80 intersection, where Old US 80 diverges to the east, the study area broadens to a four-mile wide corridor, centered on the 347th Avenue section-line alignment, extending north to the Salome Highway. North of the Salome Highway, the study area width narrows back to two miles, following the 339th Avenue alignment north to I-10. The study area covers approximately 93.9 square miles. The project study area is shown in Figure 1. For the purposes of this memorandum, the project study area has been broken up into three regions of similar drainage characteristics. The approximate extents of each region are described below: ƒ Southern Region – Watermelon Road to Old US 80 Gillespie Dam Bridge; ƒ Central Region – Old US 80 Gillespie Dam Bridge to Intersection of Old US 80 and Arlington School Road; ƒ Northern Region – Intersection of Old US 80 and Arlington School Road to I-10. 1.3 Document Purpose and Scope The purpose of the Conceptual Drainage Report is to describe the existing drainage conditions and patterns in the project study area. The drainage study was limited to the collection and review of existing drainage reports, roadway drainage reports, area drainage master studies and plans, floodplain studies, and field observations of existing drainage patterns and structures included in and adjacent to the project study area. Hydrologic information from previous drainage and floodplain studies was compiled to present watershed subbasins and previously determined peak flow rates draining to the project study area. An inventory of existing drainage facilities was also prepared. This information will provide an overview of the physical features of the project study area pertaining to drainage, and will be used in the development of feasible alignment alternatives. 1.4 Design Drainage Criteria Drainage design for the proposed parkway shall follow criteria outlined in the Drainage Policies and Standards for Maricopa County, Arizona (Maricopa County, 2007) and Chapter 4.7 of the Roadway Design Manual (MCDOT, 2004). 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 2 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 me Hw y H as sa y amp a R r ive 331st Ave Sa lo 363rd Ave PA L O V E RD E HILLS 339th Ave W H I T E TA N K M O U N TA I N S Gila River B U C K E Y E H IL L S Project Study Area Buckeye GIL A B E ND MO UN TA IN S M AR La Paz County A Project Study Area Gila R P Gila County O Old US 80 IC Yavapai County M O U N TA IN S iver op Maric Watermelon Rd a Rd Yuma County Gila Bend Pinal County 0 1.25 2.5 Maricopa County 5 Miles Pima County Sept. 2009 Figure 1 – Project Study Area 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 3 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 1.5 Drainage Studies Several drainage studies have been prepared for the area surrounding the Hidden Waters Parkway project study area by various agencies such as the Flood Control District of Maricopa County (FCDMC) and the Arizona Department of Transportation (ADOT). A graphic depicting the vicinities of the drainage studies is provided as Figure 2 at the end of this section. Drainage studies potentially impacting the project study area were researched and information compiled to complete the existing conditions analysis detailed in this memorandum. A summary of the most relevant drainage studies is provided in the following sections, organized by region. Floodplain and floodway delineations were based on the Flood Insurance Study, Maricopa County, Arizona and Incorporated Areas, FIS No. 04013CV001A (Federal Emergency Management Agency [FEMA], 2005). 1.5.1 Previous Drainage Studies - Southern Region The following drainage studies were reviewed for study of the watersheds in the southern region of the project study area. The studies included descriptions of existing hydrology, drainage features, and existing drainage patterns. ƒ Hydrology Report, Gila Bend Canal Floodplain Delineation Report, Gillespie Dam to Gila Bend (FCDMC, 1991) The hydrology report presents the hydrologic methods and data used to compute the basin and subbasin discharge rates used in the hydraulic analysis and floodplain delineation portions of the Gila Bend Canal Floodplain Delineation study. The study covers the Gila Bend Canal Watershed and provides 100-year peak flow rates at each subbasin. The basin delineation and the results of the hydrologic analysis were used in this report for the southern (Gila Bend Canal Floodplain) watershed. The discharge rates and the subbasins delineations can be used, with some modifications, to determine appropriate drainage crossings for the Parkway. ƒ Rainbow Wash Floodplain/Floodway Delineation Study TDN Hydraulics (FCDMC, 1994) The Rainbow Wash Flood Insurance Study (FIS), which the Hydraulics Technical Data Notebook (TDN) is a part of, provides floodplain elevations in areas adjacent to Rainbow Wash and its tributary from the Gila River to upstream of SR 85. The study consists of the topographic mapping and hydraulic analysis necessary to determine 100year flood elevations and to map regulatory floodplain boundaries for the area. The Hydraulics TDN focuses on the topographic mapping, hydraulic analysis, and floodplain delineation tasks of the Flood Insurance Study (FIS). The hydrology and basin delineation in this report updated the analysis in the Gila Bend Canal Floodplain Delineation Report (FCDMC, 1991), but the updated results are limited to the Rainbow Wash watershed. 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 4 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 ƒ Initial Drainage Report, SR 85, Gila Bend to I-10, Volume I and Volume II (ADOT, 1999) The report evaluated the existing drainage conditions along the then two lane roadway and recommended improvements for the proposed four lane divided highway. This report was later supplemented by the design stage reports Draft Drainage Technical Memorandum, SR 85, Gila Bend to Lewis Prison, (ADOT 2001), the Final Drainage Report, SR 85, MP 122.58 to 126.08 (ADOT, 2004), and Final Drainage Report, SR 85, MP 126.08 to 130.71, Gila Bend – Buckeye Highway (ADOT, 2003). However, this Initial Drainage Report contains the complete hydrologic and hydraulic analyses for SR 85 and is referenced by the later reports. The hydrology in this report was derived starting with the HEC-1 analysis completed in the Gila Bend Canal Floodplain Delineation Report (FCDMC, 1991). 50-year and 100-year peak flow rates were calculated for the drainage crossings at SR 85. ƒ Draft Drainage Technical Memorandum, SR 85, Gila Bend to Lewis Prison (ADOT, 2001) This memorandum was superseded by the Final Drainage Report, SR 85, MP 122.58 to 126.08 (ADOT, 2004) and Final Drainage Report, SR 85, MP 126.08 to 130.71, Gila Bend – Buckeye Highway (ADOT, 2003). The report includes more information concerning the horizontal alignment of the existing cross culverts, sedimentation, scour, and pipe corrosion. Peak flows for the 50-year storm event were estimated with HEC-1 for the report, but the Rational Method was used for small watersheds. The report includes the SR 85 corridor from Gila Bend to Lewis Prison. Some of the recommendations for drainage improvements described in this document can be utilized for the Hidden Waters Parkway, because the roadways will be nearly parallel to each other in this section. ƒ Final Drainage Report, SR 85, MP 122.58 to 126.08 (ADOT, 2004) and Final Drainage Report, SR 85, MP 126.08 to 130.71, Gila Bend – Buckeye Highway (ADOT, 2003) These reports discussed roadway drainage within the SR 85 corridor and discussed the preliminary design of 28 box culverts to be built during the first phase of the construction for SR 85 (from MP 122.58 to 130.71). These studies were used to update information provided in the Initial Location/Design Concept Report, SR 85, Gila Bend to I-10, (ADOT, 1999). The reports should be used when designing the drainage structures of the Hidden Waters Parkway as a reference for existing conditions along the section. 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 5 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 1.5.2 Previous Studies – Gillespie Dam and Gillespie Dam Bridge The following drainage studies were reviewed to gather information on the Gillespie Dam and Gillespie Dam Bridge (also known as the Old US 80 Bridge). The studies include descriptions of the bridge and dam and discuss the alternatives for replacing the bridge. ƒ Old US 80 Gila River Bridge, Final Design Concept Report (MCDOT, 2007) The Design Concept Report is a comprehensive report that includes an in-depth steel inspection, structural analysis, traffic analysis, drainage/scour analysis, parallel seismic studies as part of the geotechnical evaluation, coating assessment, public involvement, and environmental studies for the Gillespie Dam Bridge. The Design Concept Report preceded the Old US 80 Bridge Rehabilitation Value Engineering Final Report (MCDOT, 2008). However, the analysis findings presented in this Design Concept Report that are relevant to the Parkway should be taken into consideration when designing the Parkway in the area of the bridge. ƒ Old US 80 Bridge Rehabilitation (Gillespie Dam Bridge) Value Engineering Final Report (MCDOT, 2008) The Value Engineering Report described the conclusions of a Value Engineering Workshop to evaluate the Design Concept Report to replace or improve the Gillespie Dam Bridge at the Gila River. The report describes the alternatives considered for the Gillespie Dam Bridge. DT-04 was ultimately chosen as the alternative to move forward on, which consists of a new interim low-flow crossing of the Gila River approximately 1,000 feet south of the existing bridge. The interim low-flow crossing would ultimately be replaced by an all-weather bridge crossing. The alignment of DT-04 will be the assumed alignment of the Parkway for purposes of this feasibility study. 1.5.3 Previous Drainage Studies - Central Region The following drainage studies were reviewed for study of the watersheds in the central region of the project study area. The studies included descriptions of existing hydrology, drainage features, and existing drainage patterns. ƒ Lower Centennial Wash Watershed Zone A Floodplain Delineation Study Phase 1 TDN (FCDMC, 2005a) The purpose of the floodplain study was to delineate the 100-Year Zone A Floodplains for Phase I of the Lower Centennial Wash Watershed. The goal was to delineate floodplains before development occurred to improve upon floodplain management and minimize losses due to flooding. Peak flows for the 100-year, 6-hour and 100-year, 24hour storms were calculated for the study. Subbasin delineations were also prepared for the study, and are presented in this report as the hydrology and subbasins for the watersheds in the central region of the project study area. The discharge rates and the subbasins delineations can be used, with some modification, to determine appropriate drainage crossings for the Parkway. 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 6 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 ƒ Lower Centennial Wash Watershed Zone A Floodplain Delineation Study – Low Level Geomorphic Assessment (FCDMC, 2005b) The purpose of the report was to provide a Low Level Geomorphic Assessment of Lower Centennial Wash and its tributaries. The purpose of the low level geomorphic assessment was to analyze and document the landforms in the Lower Centennial Wash study area, and to identify locations where surface geomorphology may result in distributary flow. The study provided information on the existing watershed drainage features, and explained the alluvial fan nature and presence of split flows in the Lower Centennial Wash Watershed. The information presented in this report can be used for the Parkway design to better understand the existing drainage patterns and land uses. 1.5.4 Previous Drainage Studies - Northern Region The following drainage studies were reviewed for study of the watersheds in the northern region of the project study area. The studies included descriptions of existing hydrology, drainage features, and existing drainage patterns. ƒ Hydrologic Study Report for Luke Wash Watershed Zone AE Floodplain Delineation Study (FCDMC, 2008) The purpose of this study was to develop detailed hydrologic models for the 100-year, 6-hour and 100-year, 24 hour events in order to delineate approximately 85 linear miles of Zone AE floodplains and floodways of Luke Wash and nearby tributaries of the Hassayampa and Gila Rivers. The study covers the Luke Wash Watershed and provides 100-year peak flow rates at each delineated subbasin. The basin delineation and the results of the hydrologic analysis were used in this report for the watersheds in the northern region of the project study area. The discharge rates and the subbasin delineations can be used, with some modification, to determine appropriate drainage crossings for the Parkway. 1.5.5 Future Drainage Study FCDMC is initiating the Gillespie Area Drainage Master Study for a 140 square-mile portion of the Gillespie Watershed. This study area consists of the northern portion of the Gila Bend Canal FDS Watershed shown in Figure 2, from the Buckeye Hills divide near Gillespie Dam to one-half mile south of Pierpoint Road. The study is expected to begin in April 2010 and will take approximately 18 months. The primary goals of the future study are to: ƒ ƒ ƒ ƒ Create updated hydrology model utilizing new 2-foot contour mapping and NOAA-14; Determine the impact of existing and planned development; Identify and prioritize watercourses for future floodplain delineation studies; and Establish “planning guidelines” to coordinate future drainage improvements. 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 7 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 Jackrabbit Wash FDS Palo Verde FDS Buckeye Area FDS Lower Centennial Phase III FDS El Rio WMP Lower Hassayampa WMP Lower Centennial Phase II FDS White Tanks/Agua Fria FDS White Tanks Wash FDS Luke Wash FDS Gillespie Dam Lower Centennial Phase I FDS Rainbow Wash FDS Lower Painted Rock FDS Waterman Wash FDS Gila Bend Canal FDS Sentinel Wash FDS Gila Bend FDS Legend 0 Hidden Waters Corridor 100-Year Floodplain 2 4 8 Miles Sept. 2009 Figure 2 – Area Drainage Studies 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 8 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 2. EXISTING LAND USE Exhibit 1A and Exhibit 1B in Appendix TM3-1 provide photographs taken during a field review of the project study area land uses and their associated typical drainage features. The existing land use within the project study area is primarily agriculture and vacant land; however, a few residential, commercial, and industrial land uses also exist within the area. Some portions of the project study area contain parts of the Gila River. The land use features discussed below should be considered when developing Parkway alignment alternatives and when designing drainage conveyance structures during final design. Where existing drainage structures and residential, commercial, and industrial land uses exist within the project study area, care should be taken during final design to not increase flooding or ponding upstream and downstream of proposed drainage structures. In the southern region, State Road 85 (SR 85) runs along the east side of the project study area, paralleling the project study area until approximately the intersection of SR 85 and Woods Road. Land use in this area is predominantly agriculture, including a large dairy farm with sludge ponds located within the project corridor between Watermelon Road and Fornes Road. The Gila Bend Canal flows along the eastern boundary of the project study area from Gillespie Dam to the south end of the project. The canal is elevated and hydraulically separates the project area from lands east of the Corridor. The Old US 80 Bridge is located approximately 500 feet downstream of Gillespie Dam. The bridge is a 9-span steel truss bridge that spans the Gila River. Gillespie Dam has been breached but still acts as a dominant control on the Gila River and the subsequent land uses that result from the water impoundment. The land use in the central region is mostly agricultural lands on the east side of Old US 80, and undeveloped desert lands on the west side of Old US 80. Much of this land is located within the broad Gila River floodplain. The Arlington Canal runs within the project study area, along the east side of Old US 80 from 331st Avenue to West Desert Rose Road. The Arlington Canal then crosses Old US 80 and runs along the west side of Old US 80 from West Desert Rose Road to just north of Agua Caliente Road. The Arlington Canal then crosses Old US 80 again and runs along the east side of the road to Gillespie Dam. In the northern region, much of the land is undeveloped desert featuring numerous regulatory floodplains. The project study area crosses the Union Pacific Railroad (UPRR) approximately 2000 feet south of Elliot Road. Low-density residential areas are located within the project study area between Elliot Road and I-10. More detailed land use observations for the northern region can be found in the recently completed Luke Wash Watershed Zone AE Floodplain Delineation Study (FCDMC, 2008). 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 9 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 3. EXISTING WATERSHED FEATURES The Hidden Waters Parkway project study area lies within the Sonoran Desert region of the Basin and Range geographic province. The region is characterized by alluvial fan, terrace, and basin floor deposits surrounded by rugged, low- to high-relief mountain ranges that include a variety of granitic rocks and volcanic rocks. The area is drained by numerous washes that flow towards the Gila River. Dry washes in the project study area flow only in response to rainfall events, and may overtop during heavy rainfall events. Flooding is more likely to occur during the monsoon season lasting from July through September, but may also occur during the winter storms from December through February (Maricopa County, 2007). The watersheds contributing offsite flows to Hidden Waters Parkway may be addressed by dividing the drainage patterns into three drainage regions within the project study area. These regions are: ƒ ƒ ƒ Southern Region: Drainage south of the Gila River – The project study area in this region is generally oriented parallel to the Gila River but perpendicular to the offsite drainage patterns. Offsite flows come from watersheds to the east of the project study area and flow west to the river, which is a very similar situation that exists along SR 85 in this area. Drainage impacting Hidden Waters will be alluvial fan and distributary in nature, subject to flash flooding and high sediment loading. The drainage region south of the Gila River may be described as associated with the Gila Bend Canal watershed and Rainbow Wash. The Gila Bend Canal watershed borders the east side of the project study area. This watershed originates in the Maricopa and Buckeye Hills Mountains and flows west towards the Gila Bend Canal and SR 85. Central Region: Gila River Crossing – The Gila River provides a separate and distinct riverine challenge for a crossing for the Parkway. A bridged crossing of the river will need to consider high flood flows, a fairly wide floodplain, FEMA floodplain impacts, and long-term river bed elevation changes and local scour countermeasures. The central drainage region may be described as associated with the Lower Centennial Wash (tributary of the Gila River) and the Gila River. The Lower Centennial Wash watershed originates in the Gila Bend Mountains and flows east towards the Gila River. Northern Region: Drainage north of the Gila River – The project study area in this region is generally oriented parallel to the Luke Wash drainage. Luke Wash is a large regional drainage tributary system to the Gila River. The wash is typical of ephemeral desert washes subject to flash flooding and high sediment transport. The project study area crosses Luke Wash and its finger tributaries many times. Drainage facilities for the Parkway will need to accommodate sedimentladen flood flows. The Parkway embankment and earthen diversions may serve to direct and control flows within the project study area. The Luke Wash watershed, which makes up the northern region of the project study area, flows south from the Central Arizona Project (CAP) Canal, is conveyed under I-10 and Salome Highway, and discharges to the Gila River. 3.1 Southern Region: Drainage South of the Gila River 3.1.1 Gila Bend Canal Watershed Flow south of the Gila River in the Gila Bend Canal watershed occurs in wide, shallow sheet-flow patterns with numerous small braided stable washes and one major wash. The Rainbow Wash floodplain is also included in this watershed. Flow is conveyed west across SR 85 to the Gila Bend Canal by box culverts, pipes, and a bridge at Rainbow Wash. Dikes 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 10 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 and ditches have been constructed at some locations to collect and direct both the sheet and the smaller wash flows to the appropriate culvert (ADOT, 1999). The Gila River and floodplain in this area parallel the western side of the southern region project study area for most of the region. The river and floodplain cross into the southern region project study area about 5.2 miles south of Gillespie Dam. The Gila River floodplain in this area is approximately 1.7 miles wide, with roughly 0.6 miles of floodplain width within the project study area. In the Gila Bend Canal Floodplain Delineation Report (FCDMC, 1991) the watershed subbasins were defined by starting the delineation from 11 siphon spillways and the lift station spillway along the Canal. Minor features, including small culverts passing under or into the Canal, and significant ponding areas, also were considered in forming major subbasin divides at the downstream boundary of the watershed. The combined drainage area is approximately 297 square miles. Within the watershed, 18 subbasins were defined and delineated. Subbasins north of Rainbow Wash are relatively small (mostly less than a square mile). These northern areas are hilly with rock outcrops. The southern soils are sandy loam and loamy sand. Vegetation is sparse and consists of desert brush. Subbasins south of the Gila River and south of Rainbow Wash are mostly undeveloped desert, range, or mountainous. Half of the watershed (to the east) is designated as the North and South Maricopa Mountains Wilderness Area. A residential development one mile south of Woods Road abuts the east bank of the Gila Bend Canal inside the project study area. Agricultural fields occupy the land adjacent to SR 85. The Maricopa Mountains are mostly granite, while the other soils are gravelly and coarse textured. Vegetation density varies. In general, the downhill slopes are towards the west and south and reach a maximum of about 15 percent in the Maricopa Mountains and Buckeye Hills along the eastern and northern boundaries of the watershed. Slopes generally decrease moving west towards the Gila Bend Canal. Flatter slopes of 1 percent or less prevail in the western and southern portions of the watershed. Much of the Little Rainbow Valley has slopes in the range of 1 percent to 5 percent. Agricultural areas have been graded by landowners to slopes that are essentially flat. Much of the watershed is drained by small channels which tend to converge and diverge in a braided network. There are a few well-defined channels and three major washes: Rainbow Wash (in the Little Rainbow Valley), Margie’s Cove Wash, and Butterfield Wash. These washes, particularly Rainbow Wash, form significant channels of large capacity as they approach SR 85 and the Gila Bend Canal. In other basins, channels continue to be braided and distributary even as they pass to the west of SR 85, arriving at the Gila Bend Canal berm and cross-drainage structures in many distinct flow paths. In agricultural areas, landowners have constructed a system of drainage ways to convey storm flow around crop land and provide tailwater drainage. Parkway Drainage Considerations: Currently, no structures exist in the area to convey or control the Gila River through this approximately 5.2 mile stretch of land below the Gillespie Dam. Consideration to avoid impacting the Gila River floodplain as much as possible should be given during the alignment alternatives analysis for the Parkway. The 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 11 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 embankment along the Gila Bend Canal will control drainage patterns along the east side of the project study area, so drainage crossings structures will ultimately need to be designed in conjunction with the canal overshoot locations. Because SR 85 parallels Old US 80 in this area, several considerations should be made based on information from the SR 85 Gila Bend to Lewis Prison Drainage Technical Memorandum (ADOT, 2001). Sedimentation will most likely be a problem, as it is currently a problem for SR 85 in this area. Culverts along SR 85 were set below the flow line of the wash, and this has created a foot of more sediment accumulation in the culverts. Care should be taken to set the proposed Parkway culvert inverts at the flow line of the wash to avoid the problems that the SR 85 culverts encounter. Inspectors have also noted corrosion in the corrugated metal pipes along the SR 85 corridor. Soil conditions seem to be corrosive in the area between SR 85 Mile Post (MP) 123 and MP 126; therefore, corrosion-resistant culvert materials for the Parkway should be chosen with soil properties in mind. The ADOT document also suggested using ditches and berms where possible to allow culverts to function as a group, making it more difficult to clog any single culvert. 3.1.2 Rainbow Wash Watershed The Rainbow Wash watershed is included in the Gila Bend Canal Floodplain Watershed, but was studied separately by FCDMC in 1994. The watershed is typical of desert basins of the arid southwest. The northern limits of the watershed lie within the Buckeye Hills. Rainbow Wash flows through Little Rainbow Valley and discharges into the Gila River about 3.5 miles downstream of the Gillespie Dam. The Rainbow Wash floodplain and the Gila River floodplain have a confluence approximately 4.7 miles downstream of the Gillespie Dam Bridge. The 100-year peak discharge at the confluence with the Gila Bend Canal is 11,568 cfs (FEMA, 2005). Vegetation within the watershed consists of creosote bush, palo verde, mesquite, cacti, and acacias. Agricultural land consisting of active and inactive cotton fields are located adjacent to Rainbow Wash downstream of SR 85. There is little development within the floodplain. Floods are characterized by flows which rise and recede quickly. Flows in Rainbow Wash appear to result in substantial transport of sediment as well as cause some bank erosion. Minor scouring occurs along the channel bottom just downstream of SR 85 over the main stem of Rainbow Wash (FCDMC, 1994). Based on observations from the field visit, a bridge once existing along the east side of Old US 80 at Rainbow Wash – only the north abutment is still present, so further research into the fate of this bridge is recommended during final design of the Parkway. Parkway Drainage Considerations: The Rainbow Wash floodplain is approximately 600 feet wide at the point where the floodplain enters the project study area. A bridge or other large drainage structure will likely need to be considered if an alignment is selected that crosses Rainbow Wash in this area. Impacts to the Rainbow Wash floodplain and floodway should be considered and may necessitate a detailed floodway study. 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 12 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 3.2 Central Region: Gila River Crossing The Lower Centennial Wash Watershed is approximately 53.5 square miles of mainly undeveloped upland desert. The confluence of Lower Centennial Wash and the Gila River occurs near Desert Rose Road in the center of the project study area. The watershed is bounded at its far upstream end by mountains and on the north and west by a segment of the UPRR, Centennial Wash, and the Gila River. The watershed incorporates areas of riverine flooding, sheet flooding in areas of alluvial plains, alluvial fan deposition, and stable areas that are underlain by pediments and relict fans. Although sheet flooding may occur in these areas, it does not result in either deposition of widespread erosion. The Lower Centennial Wash watershed contains areas of lowdensity residential, open space, and agriculture land uses. The runoff from the watershed ultimately discharges to the Gila River (FCDMC, 2005b). The Gila River floodplain covers the eastern half of this region of the project study area. The 100-year peak discharge of the Gila River at Gillespie Dam is 235,000 cubic feet per second (cfs). The 100-year water surface of the Gila River at the dam is approximately 11 feet, and the 100year water surface of the Gila River at the ground just upstream of the dam is 16 feet. The Gila River floodplain at Gillespie Dam is approximately 1,750 feet wide, and the Gila River floodplain at Desert Rose Road, just upstream of the confluence with Lower Centennial Wash, is 9,100 feet wide (2,700 feet within the project study area). The depth of flow in this area is 23.5 feet. Parkway Drainage Considerations: The alluvial fans and distributary flow characteristics in the watershed should be considered during the hydrologic analysis for proposed drainage structures along the Parkway in this region. Sediment deposition will probably not be as much of a concern in this section as it is in the southern and northern sections because the area is considered stable. The Parkway is assumed to cross the Gila River at the new crossing location identified by MCDOT approximately 1,000 feet south of the existing Old US 80 Bridge. The Parkway will also need to cross Lower Centennial Wash if the Parkway follows a similar alignment to Old US 80. 3.3 Northern Region: Drainage North of the Gila River The Luke Wash Watershed is located in the western part of Maricopa County, roughly from the 371st Avenue alignment east to the Hassayampa River, and from the Gila River north to the CAP Canal. The watershed has a total area of approximately 75 square miles. The watershed is primarily natural undeveloped desert with portions of agricultural farmland and urban development. Most of the agricultural farmland and urban developments are located within the southern portion of the watershed (south of I-10). Elevations range from approximately 1,360 feet near the CAP Canal to approximately 800 feet near the northern edge of the Gila River. Surface runoff is generally from north to south through a network of ephemeral sand-bed washes. These washes eventually drain into the Gila River with a few directly tributary to the Hassayampa River. The general slope of the watershed is 0.55 percent. Vegetation through the study reaches includes trees, cacti and various shrubs. Dickey Wash and Phillips Wash combine approximately 3 miles south of I-10 and become Luke Wash. Luke Wash is the main wash that runs into the Gila River. A major tributary (to the west of Luke Wash) joins Luke Wash just south of the UPRR. The study area has a wide variety of channel and overbank characteristics, varying from well defined sand-bed and bedrock channels with a majority of the estimated 100-year flow expected 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 13 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 to be contained within the defined channel banks, to shallow distributary reaches with very limited channel conveyance capacity. Split flow can occur as side weir or distributary conditions. Stormwater runoff occurs in the study area only in response to significant rainfall events (FCDMC, 2008). Parkway Drainage Considerations: Drainage structures, such as bridges or culverts, will need to be considered for any Parkway alignments that cross Luke Wash and its tributaries. During the alignment alternatives analysis for the Parkway, consideration should be given to making the least impact on FEMA floodplains. Hydrologic analysis for the proposed culverts along the Parkway should be developed during final design to consider split flows and the distributary nature of the watershed. Upstream ponding and downstream inundation should be analyzed so that property owners are not affected by increased flooding. Sediment and erosion control should also be considered during the design of the proposed drainage system. 3.4 Soils According to the United States Department of Agricultural (USDA) Natural Resource Conservation Service’s soils website, the major soil types within the study area are GunsightRillito-Chuckawalla (approximately 63 percent of the study area), Gilman-Lagunita-Indio (approximately 16 percent of the study area), Carrizo-Brios-Antho (approximately 11 percent of the study area), Denure (approximately 9 percent of the study area) and Quilotosa-Vaiva-Rock Outcrop (approximately 1 percent of the study area). Table 1 lists the characteristics of the soil types and Figure 3 indicates where the soils are located in the study area. These soil types are typically considered suitable for the construction of roadways on top of them. Table 1 – Soil Type Characteristics Typical Location Depth to Restrictive Layer Drainage Comments Gunsight-RillitoChuckwalla Alluvial fans at 0-10% slopes More than 80 inches Well drained to somewhat excessively drained, with a moderately high to high water transmission rate, which makes runoff from this soil type very slow or almost negligible. Gilman-LagunitaIndio Floodplains at 0-1% slopes More than 80 inches Well to excessively drained, with a moderately high to very high water transmission rate - this makes runoff from this soil type almost negligible. Carrizo-BriosAntho Floodplains at 0-1% slopes More than 80 inches Excessively drained with a high water transmission rate, which makes runoff from this soil type almost negligible. Denure Fan terraces at 1-3% slopes More than 80 inches Somewhat excessively drained with a moderately high to high water transmission rate, which makes runoff from this soil type very slow and almost negligible. Quilotosa-VaivaRock Outcrop Complex Mountains at 15-55% slopes More than 80 inches Somewhat excessively drained with a very low to low water transmission rate, which creates a high potential for stormwater runoff. Soil Type Source: United States Department of Agricultural (USDA) Natural Resource Conservation Service’s soils website (http://websoilsurvey.nrcs.usda.gov, accessed June 29, 2009) 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 14 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 10 Sal o wy 379th Ave 339th Ave me H 85 Old Highway 80 Legend Study Area Boundary Soil Name Carrizo-Brios-Antho Cherioni-Hyder-Cipriano Denure Gilman-Lagunita-Indio Gunsight-Rillito-Chuckawalla Marana-Sasco-Denure Momoli-Carrizo-Denure Pahaka-Estrella-Antho Watermelon Rd d opa R Mar ic 8 0 1.25 2.5 5 Miles Quilotosa 85 Sept. 2009 Figure 3 – Soils 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 15 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 3.5 Regulatory Floodplains Several FEMA floodplains are included in the watersheds that drain through the Hidden Waters Parkway project study area. These floodplains ultimately discharge to the Gila River within the project study area. Figure 4 provides a graphic of the 100-year floodplain areas and also displays the Flood Insurance Rate Map (FIRM) panels containing the effective floodplain mapping. Both FEMA effective and FCDMC (typically pending FEMA approval) floodplain limits are shown on this exhibit. Floodplain encroachment will be a limiting factor for the Parkway alignment alternatives. Detailed floodway analysis and coordination with FCDMC and FEMA may be necessary where floodplain encroachments occur. 3.6 Potentially Impacted Drainage Structures Drainage structures that could be impacted by the Hidden Waters Parkway are structures along SR 85, Gila Bend Canal siphons, proposed Gillespie Dam Bridge Alternative DT-4, UPRR bridges, and culverts along I-10. Gillespie Dam could also be impacted by proposed alignment alternatives. 3.6.1 Structures along SR 85 Approximately 49 cross-culverts exist between the Milepost 121.3 and Milepost 133.8 (Woods Road) on SR 85 according to the SR 85 Corridor Study, Gila Bend to I-10 Proposed Drainage Plan (ADOT, 1999). These culverts could potentially be impacted by the proposed Hidden Waters Parkway, and should be considered during final design of the Parkway. 3.6.2 Structures along I-10 and the UPRR There are several box culverts and drainage pipes along I-10 and railroad bridges along the UPRR that drain the Luke Wash Watershed. These should be considered during final design of the Parkway. Exhibit 2A in Appendix TM3-2 is provided to show crossing structure locations and calculations for I-10 and the UPRR that may be impacted by the proposed Parkway. 3.6.3 Gila Bend Canal Siphons Eleven siphon spillways and a lift station spillway exist along the Gila Bend Canal that could be impacted by the proposed Hidden Waters Parkway. The siphon locations are included in the Gila Bend Canal Floodplain Delineation Study HEC-1 Schematic provided as Exhibit 2B in Appendix TM3-2. These siphon locations should be considered during final design of the Parkway. 3.6.4 Gillespie Dam Bridge The existing Gillespie Dam Bridge is a 9-span steel truss bridge that spans the Gila River. The bridge is located approximately 500 feet downstream of the Gillespie Dam. The foundations for the bridge are spread footings supported on igneous bedrock from about 15 feet to over 40 feet below the river bed. The spread footings are about 10 feet wide and 33 feet in length (MCDOT, 2007b). 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 16 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 Hassayampa R i ve r rs Winte 04013C1980G 04013C1985G h Wa s 04013C1995G Ce n t en n Luke Wa s h 04013C1990G 04013C2455G 04013C2460H 04013C2465G 04013C2470H Gila River i al Wa sh W at er n ma 04013C2830F 04013C2835H G il a 04013C2855H 04013C2860H 04013C2865H 04013C2870G 04013C3230G 04013C3235G 04013C3240G 04013C3245G 04013C3480H 04013C3485H sh Wa ow inb Ra Wash ve Ri r Legend FEMA FIRM Panel Boundary Project Boundary River Major Wash 0 1.25 2.5 5 Minor Wash Miles Floodplain Sept. 2009 Figure 4 – Floodplains 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 17 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 In January 1993, a major flood occurred that resulted in the overtopping and subsequent failure of Gillespie Dam. The size of the flood was not recorded due to equipment failure. However, an estimated flow of 200,000 cfs based upon a high water mark recorded on USGS equipment was determined. This corresponds to approximately a 65-year flood (Wikipedia, 2009). The collapse of the dam concentrated flows on the easternmost portion of the bridge. This caused scouring of the east bridge abutment and two of the piers. A repair project was undertaken for three of the piers at the east end of the bridge in late 1995. The repair addressed cracks in some piers and provided a curtain wall around the upstream and the sides of several piers. Alternatives have been proposed by MCDOT to rebuild the Gillespie Dam Bridge. The currently preferred alternative, DT-04, includes constructing a new interim low-flow crossing roadway outside of the bridge ponding area to allow the existing bridge to be converted to a pedestrian crossing or one-way bridge. The new roadway would become a two-lane full service roadway at completion. A new 60-foot single span bridge would allow for conveyance of minor river flows across the lowest point of the Gila River (MCDOT, 2008). An all-weather, 1,800-foot long, 14-span bridge has been proposed to ultimately replace the interim low-flow crossing. For purposes of this study, it is assumed that the Parkway will utilize the same alignment as the proposed new bridge. Sketches of the proposed bridge alignment and roadway are provided as Exhibit 2C in Appendix TM3-2. 3.6.5 Gillespie Dam Gillespie Dam is a privately-owned irrigation water diversion dam located on the Gila River near the midpoint of the Hidden Waters Parkway project study area. It is a multiple-arch concrete dam on a 2-foot thick concrete slab with piling below pier walls and with concrete sheet piling as cut off walls near the upstream and downstream edges of the slab. Diversion structures at the east and west ends of the dam were constructed and include sluice gates. The west diversion structure has been inactivated and its function replaced by a gated opening in the third arch from the west end that releases impounded stream-flow to the 4foot deep water cushion impounded by a concrete weir. A 30-inch diameter corrugated metal pipe has been installed, with inlet submerged below the water cushion, to divert irrigation water to the Enterprise Canal. The transition length of the Gila Bend Canal has been rehabilitated from the diversion gates to the newly lined canal. Gila River surface water has been diverted for agricultural irrigation at Gillespie Dam since its construction in 1921. Two principal canals, the Enterprise Canal and the Gila Bend Canal, transport the diverted water for many miles and have provided a basis for the development of large acreages of cropland and pasture. These canal routes have permitted development of many wells located adjacent to the canals to supplement surface water supply by pumping groundwater. Any modifications to Gillespie Dam must account for the maintenance of adequate diversion capability in the foreseeable future (FCDMC, 1981). In 1993, the dam was overtopped by an approximately 65-year flood and failed. The flood caused extensive scouring at the Gillespie Dam Bridge. The dam has not been repaired since the flood, and a small earthen embankment exists to direct water into nearby canals. 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 18 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 3.7 Sedimentation The alluvial fan and distributary flow characteristics of the watersheds carry significant amounts of sediment during storm events. Sedimentation could impact the drainage facilities and hydraulic structures within the project study area, and may result in erosion and scour at the structures. The level of sedimentation, scour, and erosion expected to occur at proposed drainage structures would be typical the drainage issues commonly experienced along SR 85 and I-10. Sediment deposition, scour, and erosion should be considered during the final design of the Parkway. 3.8 Geology The land surrounding the project study area is characterized by alluvial fans and basin floor deposits. Mountain ranges surround the area, and these ranges include a wide variety of granitic and volcanic rocks. The areas bordered by the Palo Verde Hills to the northwest and the Signal Mountain and Woolsey Peak Wilderness Areas to the south are generally composed of lava, tuff, and fine grained intrusive rock. The east side of the project study area, bordered by the Maricopa Mountains and the Buckeye Hills are generally composed of granitic rock. The eastern portions of the Woolsey Peak Wilderness Area are also composed of granitic rock (Maricopa County, 2007). A map depicting flood hazards based on soil type, surficial geology, and 100-year floodplains is provided as Figure 5. 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 19 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 AZ022 AZ028 AZ022 AZ007 AZ016 AZ005 AZ001 AZ021 W at er n ma AZ021 sh Wa AZ007 AZ021 AZ021 AZ022 AZ003 Legend Hidden Waters Corridor 100-Year Floodplain Landform Descriptions AZ001 Floodplains at 0-1% Slopes AZ003 Floodplains at 0-1% Slopes AZ005 Stream Terraces at 0-3% Slopes AZ007 Fan Terraces at 1-3% Slopes AZ008 Fan Terraces at 0-15% Slopes AZ009 Fan Terrances at 0-3% Slopes AZ016 AZ021 AZ021 AZ003 AZ010 Fan Terrances at 0-3% Slopes AZ016 Alluvial Fans at 0-10% Slopes AZ017 Hills and Mountains at 1-15% Slopes AZ016 AZ021 Mountains at 15-55% Slopes AZ022 Hills and Mountains at 3-55% Slopes AZ028 AZ009 0 1.25 2.5 5 Miles Alluvial Fans at 0-5% Slopes AZ021 Sept. 2009 AZ010 Figure 5 – Flood Hazards Map 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 20 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 4. EXISTING HYDROLOGY Existing hydrology data for the Hidden Waters Parkway project study area watershed was summarized from the following studies. ƒ ƒ ƒ ƒ Hydrology Report, Gila Bend Canal Floodplain Delineation Report, Gillespie Dam to Gila Bend (FCDMC, 1991) Rainbow Wash Floodplain/Floodway Delineation Study (FCDMC, 1994) Lower Centennial Wash Watershed Zone A Floodplain Delineation Study, Phase I TDN (FCDMC 2005a) Hydrologic Study Report for Luke Wash Zone AE Floodplain Delineation Study (FCDMC, 2008) A summary of the hydrologic resources is provided in Table 2. A map depicting the subbasin drainage areas, concentration points, and flow paths is provided as Exhibit 3A in Appendix TM3-3. The storm event discharges at concentration points for the 50-year and 100-year storm events are provided as Exhibit 3B in Appendix TM3-3. As shown in these tables, the highest concentrated flows are expected in the southern and central regions. Washes in these parts of the Corridor typically originate in nearby mountains and flow perpendicular to the proposed parkway, requiring crossing structures. Flows in the northern region are smaller but more numerous, and typically flow parallel to the Corridor. Careful selection of an alignment could reduce the need for drainage structures in the northern region. The floodplain studies listed above only calculated the 100-year discharge for each subbasin. However, a 50-year discharge was provided for concentration points along SR 85 in the SR 85 Initial Drainage Report (ADOT, 1999). A local regression equation was derived from the SR 85 Initial Drainage Report results and applied to the other project study area subbasins to calculate preliminary 50-year discharges. This regression analysis is shown as Exhibit 3C in Appendix TM-3. 4.1 Gila Bend Canal Floodplain Watershed – Southern Region The Gila Bend Canal Floodplain watershed was modeled using the U.S. Army Corps of Engineers HEC-1 computer program. The models were formulated to compute flows arriving at the Gila Bend Canal at 18 concentration points. Subbasins were delineated using United States Geological Survey (USGS) 7.5 minute topographic maps. Basin boundaries were traced upstream starting from the spillway siphons or ponding areas. The delineation proceeded eastward of SR 85 and the UPRR to the watershed divide. The 100-year, 6-hour and 24-hour precipitation events were derived from National Oceanic and Atmospheric Administration (NOAA) II rainfall depths. The time distribution was based on FCDMC design procedures for the 6-hour storm and the SCS Type II distribution for the 24-hour storm. Runoff rates from individual subbasins were determined by application of Green and Ampt precipitation loss procedures. Flows were generated using unit hydrographs based on either the FCDMC standard procedures for the 6-hour storm or the Phoenix Valley S-hydrograph method for the 24-hour storm. Subbasins flows were combined and routed as appropriate for the flow pattern in each subbasin. Normal depth routing procedures were used. Transmission losses in channel flow due to infiltration were included in all routings. Flows were assumed to be able to split and jump across basin or subbasin divides at five locations in the watershed. Each of these locations was represented as a diversion in the HEC-1 model (FCDMC, 1999). 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 21 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 Table 2 – Summary of Offsite Hydrology Resources Drainage Area Study Reach Length (mi2) (mi) Gila Bend Canal Floodplain Delineation Study Gillespie Dam to Gila Bend 297 23 NOAA 6-hr, 24-hr HEC-1 Green and Ampt Clark, S-graph UH 7.5' quad maps 1991 Rainbow Wash FIS Gila River through S.R. 85 50 11? NOAA 6-hr, 24-hr Modified GB Canal HEC-1 aerial survey 1994 Lower Centennial Wash Watershed Zone A Floodplain Delineation Study Phase I 53.5 80.5 NOAA 2 6-hr, 24-hr HEC-1, Local Regression 10-ft DEM 2005 Luke Wash Zone AE Floodplain Delineation Study 90 85 NOAA 14 6-hr, 24-hr HEC-1 Green and Ampt S-graph UH 2-ft contours 800-1360 ft elevations 2008 Study 4.2 Rainfall Hydrology Methodology Topography Year of Study Lower Centennial Wash Watershed – Central Region Peak flows for the Lower Centennial Wash watershed were determined for the 100-year, 6-hour and 24-hour storms using HEC-1 software. Subbasin delineation was performed with the aid of the Watershed Modeling System (WMS), version 7.0, using a digital elevation model (DEM) produced from digital orthophotos. The HEC-1 model parameters were determined using WMS. The FCDMC provided a DEM that contained data points on 10-foot grid elements. WMS analyzed the DEM, SCS soils data, and land use data in order to create a HEC-1 model based on the FCDMC’s criteria. NOAA Atlas II was used to obtain the 100-year, 6-hour and 24-hour point precipitation values for the HEC-1 model. The Green and Ampt precipitation loss procedures were used to determine runoff rates based on the FCDMC guidelines. The Phoenix Mountain S-Graph was used to obtain the unit hydrographs for the watershed because the total drainage area is greater than 10 square miles. 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 22 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 Eleven reaches required channel routing. Normal depth routing was performed in HEC-1 for these reaches. There were two locations within the watershed along the UPRR where the runoff could back up at trestles, causing a need to perform reservoir storage routing. Reservoir storage routing was not performed due to its nature of being a Zone A Delineation Study, and the large area of the trestles compared to the contributing watershed (FCDMC, 2005a). 4.3 Luke Wash Watershed – Northern Region The 100-year, 6-hour and 24-hour storm events were modeled for the Luke Wash watershed using HEC-1 software, in conjunction with methods and procedures described by FCDMC. WMS software was used to develop the preliminary subbasin boundary delineations. Drainage Design Management System for Windows software (DDMSW) was utilized to prepare the input parameters for the HEC-1 models. ArcGIS was applied to transfer databases available from FCDMC to prepare parameters for modeling purposes. NOAA 14 rainfall data was used to estimate the design rainfall depth for this study. The FCDMC 6-hour local storm distribution for 6-hour model and SCS Type II precipitation distribution for the 24-hour model were used for the HEC-1 rainfall distributions. The Green and Ampt Method was utilized for the estimation of rainfall losses. The S-Graph method was used for the development of unit hydrographs. Normal depth channel routing methodology was utilized in the hydrologic model to route surface runoff through subbasins. An 8-point composite channel cross-section was developed to represent typical wash cross-section conveyance using 2-foot contour mapping. The longitudinal slopes were estimated based on general existing wash slopes and Manning’s “n” values were based on field reconnaissance estimates. Storage routing along I-10 and the UPRR were modeled using the Modified Puls reservoir routing option of HEC-1. The storage-elevation discharge relationship curves for storage facilities were developed using 2-foot contour mapping, as-built plans, and survey data. Initial rating curves were developed using Dodson software. The HEC-1 models were executed to obtain preliminary 100-year peak flows. HEC-RAS models were developed for the study washes and preliminary floodplains were delineated to evaluate if lateral flows occur along I-10 and the UPRR. The lateral flow conditions were further verified by field reconnaissance. Hydrologic models and storage routing curves were revised to represent the lateral flow (multiple washes merged flow) conditions. The final storage routing curves were developed using HEC-RAS models for the study washes. The rating curves for non-study washes were refined with Dodson software. Surface runoff from the subbasins has the potential to concentrate at more than one point. It was assumed that the concentration point was located at the hydrologic low point of the subbasin. A potential split flow from Jackrabbit Wash was identified to one of the study washes. The FCDMC provided both hydrologic and hydraulic models for the Jackrabbit Wash. A rating curve was developed using the HEC-RAS models for Jackrabbit Wash to determine the diverted flow. The diverted flow hydrograph was coded into the 100-year, 24-hour HEC-1 model. There was no split flow for the 100-year, 6-hour storm model (FCDMC, 2008). 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 23 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 5. SUMMARY AND CONCLUSIONS The purpose of the Conceptual Drainage Report is to describe the existing drainage conditions and patterns, including peak flows, for the Hidden Waters Parkway project study area. The findings of this memorandum can help determine the best alignment for the proposed Parkway. Drainage structures and features in and around the project study area have been identified and should be considered during the design of the future Parkway. Peak flows reported in this memorandum have been compiled for planning purposes only. Discharges should be evaluated based on FCDMC drainage criteria during final design of the Parkway. The impacts of crossing the Gila River and the numerous washes discussed in this memorandum should be considered when developing and evaluating potential Parkway alignment alternatives. Alignment considerations will need to include the structures (such as bridges and box culverts) that may be necessary to include in the Parkway design to convey flood flows under the proposed Parkway. Floodplain impacts and the potential need for detailed floodway studies should also be considered where applicable. The watersheds are often comprised of alluvial fans. Hydrologic analyses considered for proposed drainage structures along the Parkway alignment will need to accommodate the split flows that occur due to the alluvial fans in the watersheds in which the Parkwayalignment may be located. Sedimentation should also be taken into account when designing the proposed drainage structures. Adequate erosion control and correct placement of structures to minimize sedimentation will be necessary for the proposed drainage structures to convey flows properly throughout the service life of these structures. The proposed Parkway may cause increased ponding and inundation in the area. The watershed is mostly undeveloped desert, but there are a few residential, industrial, and agricultural developments, especially along the Gila River. Increased inundation and ponding on developed land should be avoided where feasible. Care should be taken not to adversely affect the functions of the Arlington Canal, Enterprise Canal, Gila Bend Canal, Gillespie Dam Bridge, Gillespie Dam, and culverts along SR 85 and I-10 during the drainage design for the Parkway. In summary, the following issues should be considered during the alignment alternatives analysis. A “major” issue to be considered is the placement of bridges over the washes and the Gila River. Several crossings of washes will most likely be required, and bridges may be necessary at all of these crossings. Cost considerations for possible bridges, and the upstream and downstream impacts of a bridge crossing, should be part of the alignment alternatives analysis. FEMA and FCDMC collaboration will likely be a “moderate” issue to consider during the alignment alternatives analysis and the drainage design. Impacts to the floodplains could lead to detailed floodway studies, and such impacts probably cannot be completely avoided within the project study area. Floodway studies may need FEMA and FCDMC approvals. The time, effort, and collaboration to obtain these approvals will need to be considered during the alignment alternatives analysis. A “minor” issue to be considered during final design of the Parkway is possible sedimentation. Drainage systems will need to account for the sediment deposition that will most likely occur within the project study area. 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 24 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 6. REFERENCES Arizona Department of Transportation, “Final Drainage Report, SR 85, MP 122.58 to 126.08, Gila Bend – Buckeye Highway”, February 2004. Arizona Department of Transportation, “Final Drainage Report, SR 85, MP 126.08 to 130.71, Gila Bend – Buckeye Highway”, September 2003. Arizona Department of Transportation, “Draft Drainage Technical Memorandum, SR 85, Gila Bend to Lewis Prison”, prepared by Kimley-Horn and Associates, Inc., December 2001. Arizona Department of Transportation, “Initial Drainage Report, SR 85 Gila Bend to I-10, Volume I and Volume II,” prepared by BRW, November 1999. Federal Emergency Management Agency, “Flood Insurance Study, Maricopa County, Arizona and Incorporated Areas, Volume 1 of 17”, FIS No. 04013CV001A, April, 1988, revised September 2005. Flood Control District of Maricopa County, “Hydrologic Study Report for Luke Wash Watershed Zone AE Floodplain Delineation Study”, prepared by Wood, Patel, and Associates, Inc., September 2008. Flood Control District of Maricopa County, “Lower Centennial Wash Watershed Zone A Floodplain Delineation Study Phase 1 TDN”, prepared by RBF Consulting, July 2005. Flood Control District of Maricopa County, “Final Report, Lower Centennial Wash Watershed Zone A Delineation Study – Low Level Geomorphic Assessment”, prepared by Earth Consultants International, May 2005. Flood Control District of Maricopa County, “Hydrology Report, Gila Bend Canal Floodplain Delineation Report, Gillespie Dam to Gila Bend, prepared by Donahue and Associates, September 1999. Flood Control District of Maricopa County, “1981 Report on Salt-Gila River Clearing Gillepsie Dam Analysis”, prepared by John Carollo Engineers, May 1981. Flood Control District of Maricopa County, “Rainbow Wash Floodplain/Floodway Delineation Study TDN Hydraulics”, prepared by Simons, Li, and Associates, May 1994. Maricopa Association of Governments, “Draft Interstate 8 and 10 Hidden Valley Transportation Framework Study”, prepared by DMJM Harris/AECOM, June 2009. Maricopa County, “Old US Highway 80 Area Plan”, adopted May 2007. Maricopa County and Flood Control District of Maricopa County, “Drainage Policies and Standards for Maricopa County, Arizona”, adopted April 2007. Maricopa County Department of Transportation, “Old US 80 Bridge Rehabilitation (Gillespie Dam Bridge) Value Engineering Final Report”, prepared by RH & Associates, Inc., May 2008. Maricopa County Department of Transportation, “Roadway Design Manual”, revised April 2004. 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 25 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 Maricopa Association of Governments, “Interstate 10/Hassayampa Valley Transportation Framework Study”, prepared by DMJM Harris/AECOM, September 2007. Maricopa County Department of Transportation, “Old US 80 Gila River Bridge, Final Design Concept Report”, prepared by TranSystems, September 2007. U.S. Department of Agriculture, Soil Conservation Service. http://websoilsurvey.nrcs.usda.gov, accessed June 29, 2009. Wikipedia. http://en.wikipedia.org/wiki/Gillespie_Dam, accessed August 29, 2009. 091337118 Technical Memorandum No. 3 Conceptual Drainage Report 26 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 APPENDIX TM3-1 FIELD DOCUMENTATION 091337118 Technical Memorandum No. 3 Conceptual Drainage Report Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 K:\PHX_Systems\091337118 MCDOT Hidden Waters Pkwy\CADD\GIS\maps\Drainage\Ex1A_PhotoLoc.mxd Hass aya m pa R $ a " ! ive r rs Win te h Was Luke Was h 0341 # 0 Gila River Centen ni a l Wash 0338 # 0 W at er n ma # 0# 0 R 0333 sh Wa 0336 Wash bo w n i a Í ? 0319 # 0 0314 # 0 0309 # 0 # 0 0302 0 0364 # 0296, 0298, 0363 Gil a # 0 # 0 0295 R iv er # 0 Legend # 0 # 0 Photo Location 0283 Hidden Waters Corridor Wash River 0288, 0361 $̀ " ! Hidden Waters Parkway Maricopa County, Arizona µ 0 1.25 2.5 5 Miles Sept. 2009 Field photos taken: August 5, 2009 Exhibit 1A: Drainage Photo Locations 091337118 Photo 0295: At-grade wash crossing of Old US 80 Photo 0283: Downstream side of Old US 80 at-grade crossing Photo 0296: Constructed earthen channel towards Gila River Photo 0288: Downstream section and erosion at Gila Bend Canal... Kimley-Horn and Associates Maricopa County Department of Transportation EXHIBIT 1B. DRAINAGE FIELD PHOTOS 1 Photos Date: August 5, 2009 091337118 Photo 0309: Typical roadway section of Old US 80 Photo 0298: Typical agricultural land use in Gila River valley Photo 0314: New Box Culverts Crossing of Old US 80 at Layton Wash Photo 0302: Overflow overshoot of Gila Bend Canal Kimley-Horn and Associates Maricopa County Department of Transportation EXHIBIT 1B. DRAINAGE FIELD PHOTOS 2 Photos Date: August 5, 2009 091337118 Photo 0336: Looking downstream at Gillespie Dam and Old US 80... Photo 0319: Looking downstream at former bridge and Old US 80... Photo 0338: Overgrown box culvert entrance along Old US 80 Photo 0333: Looking upstream at Gillespie Dam breach Kimley-Horn and Associates Maricopa County Department of Transportation EXHIBIT 1B. DRAINAGE FIELD PHOTOS 3 Photos Date: August 5, 2009 091337118 Photo 0363: Looking west through olive tree plantation Photo 0341: Typical roadway section looking north at 339th Avenue Photo 0364: At-grade crossing of Gila River at Pierpoint Road Photo 0361: Looking north at Gila Bend Canal overshoot Kimley-Horn and Associates Maricopa County Department of Transportation EXHIBIT 1B. DRAINAGE FIELD PHOTOS 4 Photos Date: August 5, 2009 APPENDIX TM3-2 POTENTIALLY IMPACTED DRAINAGE STRUCTURES 091337118 Technical Memorandum No. 3 Conceptual Drainage Report Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 HIDDEN WATERS PARKWAY CORRIDOR STUDY EXHIBIT 2A T O 36 HIDDEN WATERS PARKWAY CORRIDOR STUDY FCDMC Contract 2007C020 Task - Luke Wash Watershed Zone AE Floodplain Delineation Study Structure Detail Worksheet Wood/Patel Project #073087 Type of Structure: File Name: Description Name: Ibr c ~ w w IO'XS' Date: I-U-W~ WAS/-t 5 - lo S T ~ . 5 Y o L 1-36 General Condition of Structure Goo0 Party Chief: TGPF &f-64 EXHIBIT 2A HIDDEN WATERS PARKWAY CORRIDOR STUDY FCDMC Contract 2007C020 Task - Luke Wash Watershed Zone AE Floodplain Delineation Study Structure Detail Worksheet Wood/Patel Project #073087 Type of Structure: File Name: 72." L ~ P LL/W 1-tz-zao8 WASH - Description Name: x r o I Date: 57~1. General Condition of Structure JL(os+. 30 hi) Party Chief: JEFF MLIEA EXHIBIT 2A HIDDEN WATERS PARKWAY CORRIDOR STUDY FCDMC Contract 20076020 Task - Luke Wash Watershed Zone AE Floodplain Structure Detail Worksheet Wood/Patel Project #073087 Type of Structure: l u Kc File Name: + 00 s r ~ SY . 70 Photo Taken . . . . . . . . . . . . . . . . . . . . . . . . . . . . , , , . . . . I . ... . . , . . . .. . . . .. . . ., . . . . . . . .:. -.:. .. -: ... . . . . , j m . . . . . ,. . . . . .'. . . . . .,: . . . . . I. .. . .... ,. . . ..: . : I : ....:. .. . ,, . . , .' 3 >.. 1 . . . .......... , I . . . '. , , . .... . " ' ; i. . . ' i .j '. ,, . . . ...-:.. -.. . , , , . , ........ . . , t / , , . ! ; ..... ... . ,. : ; . . .:.. . ; I . ..: {&,?-0;l I . . .. . , , ...a......,.... . . . ....... . ..... ..:, .....,! , , r , . . . ;. ......... , % ........... .. : . ...... , . . . ... . . . . . ...: . . . . . . . , ..... -.. . . I . . . . . . . :. . . . . .. . . 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Task - ~ u k Wash e Watershed Zone AE Floodplain Delineation Study Structure Detail Worksheet WoodIPatel Project #073087 . ., Type of Structure: File Name: . Date: CUNELT &% ( -21-2008 wfi~ E Description Name: T- 10 Party ChieE J ~ F . 55oq +YO General Condition of Structure LAUE.Q &ZOO Photo Taken . , . . a . a . . , . . . . ..* . . .:... ,.--................... ............. . . . .,. .. . - b . -/ . . . . . , , ,. . . _ _ . _ . . .,, . . . . . . . . . . .. . . . . . . . . . . . . . . . ,. . . . . ,. . . . . .' . . . , .. , , . . - ,, - . # . . ' U . ; . 3 , General condition of structure , . . . . . L . . . . 6000 / , 1....... , .......... :.. . . . . . . I . ... . . . .. 0 I / 1 . .-. , . , .... '.;-".." .... :....,..: ., ,. . ,& :. . ........ , r ... , a .......... ;. , , i : , . , . - " '& .. ,, J. I L ........................... . , . i . I. , .....'.'.. 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HIDDEN WATERS PARKWAY CORRIDOR STUDY uPA3 EXHIBIT 2A FCDMC Contract 2007C020 Task - Luke Wash Watershed Zone AE Floodplain Delineation Study Structure Detail Worksheet WoodPatel Project #073087 Type of Structure: File Name: I C E Date: RRI(UE 7 - ~ czm6 - ,,,, Description Name: Party Chief: TEFF iz 7 .pp Photo Taken ......................................................................... . . . . . . . . ,. . .. . / (UPSTREAM) .. . Y a m . ................................................................. . s I a b . . . . , . / General Condition of Structure 0k W L L I6 4 / . , . . . . s . . , , - - vPA 4 FCDMC Contract 2007C020 Task - Luke Wash Watershed Zone AE Floodplain Delineation Study Structure Detail Worksheet Wood/Patel Project #073087 HIDDEN WATERS PARKWAY CORRIDOR STUDY Type of Structure: File Name: L ~ _ . .. . . . A . .- Party Chief: z w p c ~q ~ e n k r aCondition l of Structure , Date: t-y-ZWB w f i ~ ~ ~,I&F, DescriptionName: I RRIOGC OK . ... General condition of Structure o LALQGG EXHIBIT 2A uPR 5 HIDDEN WATERS PARKWAY CORRIDOR STUDY Task - Type of Structure: wwn File Name: ,J~~,., LOILE Description Name: EXHIBIT 2A FCDMC Contract 2007C020 Luke Wash Watershed Zone AE Floodplain Delineation Study Structure Detail Worksheet WoodfPatel Project #073087 Date: ,,PC - z - y - ~ e Party Chief: z ~ wMCLI 6& ; ~ f5 aRta,~ -- Photo Taken .& .................................................... % . .. ) ..... , ! L '. . . . i . . . : . ; : ! ; a I s . / . (UP ST;RE : ,'W , ~i :, : : ..... :.- ..:...- .!. ....:...... . " n . . , . ,. 9 / ....-. . ...r . . . ............ . , / , ;9.................................................... : 2: : : . .: , .... . I . , . .'... - - 1,... . . . > . . I . ...... :.. .r .. .. , 8 . , . . . . General Condition.of Structure . . , . . . , . . , . . . . . ole. . . . , I I ' :: ,,. . . .., .....,, Photo Talten . . . . . . . ,r ............. . !. . .., . <. 5 HIDDEN WATERS PARKWAY CORRIDOR STUDY EXHIBIT 2B HIDDEN WATERS PARKWAY CORRIDOR STUDY EXHIBIT 2C VALUE ANALYSIS PROPOSAL DT-04 Old US 80 Bridge Gillespie Dam Bridge PROPOSAL DESCRIPTION: May 2008 New interim roadway, at-grade, located 1200’ +/downstream of existing bridge SKETCH OF BASELINE ASSUMPTION HIDDEN WATERS PARKWAY CORRIDOR STUDY EXHIBIT 2C VALUE ANALYSIS PROPOSAL DT-04 Old US 80 Bridge Gillespie Dam Bridge PROPOSAL DESCRIPTION: May 2008 New interim roadway, at-grade, located 1200’ +/downstream of existing bridge SKETCH OF PROPOSED ALTERNATIVE APPENDIX TM3-3 SUPPORTING HYDROLOGIC DOCUMENTATION 091337118 Technical Memorandum No. 3 Conceptual Drainage Report Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 , % , % %% , , , % , % C70b C30b C71a 79a CC30b CC70b 33a 35a C70a C30a 23a K:\PHX_Systems\091337118 MCDOT Hidden Waters Pkwy\CADD\GIS\maps\Drainage\Ex3A_OffsiteHydro.mxd 2 1 1C1 , % 2C1 Legend 4 3 , % R b ain ow as W , % h Concentration Points Hidden Waters Corridor Flowpaths 100-Year Floodplain Luke Wash Sub-Basin Boundaries , % 4C6 Lower Centennial Sub-Basin Boundaries 5 Gila Bend Canal Sub-Basin Boundaries Gila 6 Rive 7 r 6C3 , % 0 7C4 , % 7C5 , % 8 8C6 , % 9 9C2 , % 10 10C2 , % , % 11 11C2 12 12C3 13C3 14C2 15C14 15C15 16C4 17C2 18C1 , % 13 , % , % , % 14 , % , % , % , % 16 Sa 18 nd n Ta 15 as kW 17 h PROJECT NO. 091337118 DRAWING NAME SHEET 1 OF 2 EX3A_OFFSITEHYDRO HIDDEN WATERS PARKWAY CORRIDOR FEASIBILITY STUDY EXHIBIT 3A. OFFSITE HYDROLOGY WORKMAP SCALE(H): 1"= 12,000' SCALE(V): NONE DESIGNED BY: BML DRAWN BY: JAG CHECKED BY: RAE DATE: 09/11/09 © 2009 KIMLEY-HORN AND ASSOCIATES, INC. Engineering, Planning and Environmental Consultants 7878 North 16th Street, Suite 300 Phoenix, Arizona 85020 (602) 944-5500 6,000 12,000 Feet ° THIS DOCUMENT, TOGETHER WITH THE CONCEPTS AND DESIGNS PRESENTED HEREIN, AS AN INSTRUMENT OF SERVICE, IS INTENDED ONLY FOR THE SPECIFIC PURPOSE AND CLIENT FOR WHICH IT WAS PREPARED. REUSE OF AND IMPROPER RELIANCE ON THIS DOCUMENT WITHOUT WRITTEN AUTHORIZATION AND ADAPTATION BY KIMLEY-HORN AND ASSOCIATES, INC. SHALL BE WITHOUT LIABILITY TO KIMLEY-HORN AND ASSOCIATES, INC. Maricopa County K:\PHX_Systems\091337118 MCDOT Hidden Waters Pkwy\CADD\GIS\maps\Drainage\Ex3A_OffsiteHydro.mxd THIS DOCUMENT, TOGETHER WITH THE CONCEPTS AND DESIGNS PRESENTED HEREIN, AS AN INSTRUMENT OF SERVICE, IS INTENDED ONLY FOR THE SPECIFIC PURPOSE AND CLIENT FOR WHICH IT WAS PREPARED. REUSE OF AND IMPROPER RELIANCE ON THIS DOCUMENT WITHOUT WRITTEN AUTHORIZATION AND ADAPTATION BY KIMLEY-HORN AND ASSOCIATES, INC. SHALL BE WITHOUT LIABILITY TO KIMLEY-HORN AND ASSOCIATES, INC. Maricopa County 46k 46j 54b 46i 54a 46h 52a 50g 83l 83k 44e 44f 46g 83j 88a 89a 50f 46f 21d Legend 83h 50e 44d 50c , % 83i 64d 50b 21c 44c Flowpaths 46c 46d 83e 64c 21b 46b 44b 86a 85b 21a 83b % , , % ,C62a % C60c 20g 82a , % 81b C82a 36c , % 80b ,C60b% % , 40b 36c 60a , % , % ,% % ,80b , % , % 81b 80a C81a 81a C80a 36b , % , % % , , , % ,% % , % ,% % , Has , % , % mpa %% , , , % saya % , Riv ,% % , , , % % , % , % , % , % , % , % % , , % % , , %% , , % , % , % n ia l W ash , % , % % , , % , % 10a , % , % , %% , , % , % n % , , ,% % , % er , % C ent e ° 12,000 Feet CC83a C36b 34b C60a 36a C40b CC40b 78b 77b 20f 70g 40a C40a C36a 77a 34b 78b CC36a 77b C20f 34a 70h 30g C78a C77a 20e CC77a C34a 74b 70f 30f C20e C30g 70g C70h 75a 20d CC30g 74b C70g C70f 75a C20d 74a C75a C74a CC74a 20c C30f 73b 70e 14e 73a 30e C20c C70e 70d 73b C73a 20b C30e 32b CC70e 14e 30d C70d 14d 72b C20b 32b C14d 32a 70c C30d 14c CC20a 72b 71b C14c 20a C20a 72a 79b C32a C30c 10b C14b C70c C72a 12b CC70c 71a CC30c 14a C70b 79a 30b C30b C71a CC30b 12b 12a 35a CC70b 10b C10b 33a 15a C70a C12a C30a C14a 16a CC12a C20g 6,000 60b 40c C40c 0 % , , %% , C83a C84a C82b 60c 42a 83a 82b 82b CC62a 20i 20h Gila Bend Canal Sub-Basin Boundaries 84b C64a 40d Lower Centennial Sub-Basin Boundaries 85a 64a 62a 22a 92a 91a 62b 48a 46a 22c 20j 22b 20l 42b Luke Wash Sub-Basin Boundaries 83c 64b 44a 100-Year Floodplain 83d 87a 48b 22d 92b 87b 91b 50a 20k Hidden Waters Corridor 83g 83f 50d 24a Concentration Points 56a 46e 24b 89b , % % , , % , % , % ,% % , , % , % , % C10a B31 B26 B29 B32 B30 B25 B17 CP17 CP16 CP11 B18 B9 B11 B16 CP1 CP3 B13 B24 CP9 , %B10 % , CP10 B27 B28 , % % , ,B1 % , % CP2 B3 B15 B19 B12 2 B2 1 B23 B20 B4 1C1 B6 B22 B21 4 3 B14 , % 2C1 , % R ain bo w as W h B5 B8 , % 4C6 B7 5 Gila 6 Rive r 6C3 , % 7 8 PROJECT NO. 091337118 DRAWING NAME SHEET 2 OF 2 EX3A_OFFSITEHYDRO HIDDEN WATERS PARKWAY CORRIDOR FEASIBILITY STUDY EXHIBIT 3A. OFFSITE HYDROLOGY WORKMAP SCALE(H): 1"= 12,000' SCALE(V): NONE DESIGNED BY: BML DRAWN BY: JAG CHECKED BY: RAE DATE: 09/11/09 © 2009 KIMLEY-HORN AND ASSOCIATES, INC. Engineering, Planning and Environmental Consultants 7878 North 16th Street, Suite 300 Phoenix, Arizona 85020 (602) 944-5500 Gila Bend Canal FDS (1991) Hydrology Results EXHIBIT 3B Conc. Point Drainage Area 2 (mi ) 7.31 3.78 50.49 3.17 13.74 22.51 0.64 18.39 3.51 9.41 11.43 18.22 36.41 10.2 65.15 1.36 11.54 7.59 1.85 1C1 300 4C6 500 6C3 7C4 7C5 8C6 9C2 10C2 11C2 12C3 13C3 14C2 15C14 15C15 16C4 17C2 18C1 Notes: * Q50 * (cfs) 2,173 1,819 8,671 1,218 3,984 2,157 1,306 4,073 1,224 3,675 2,024 2,084 2,513 1,430 3,740 653 1,989 1,814 993 Q100 (cfs) 2,876 2,403 11,565 1,599 5,297 2,854 1,717 5,417 1,607 4,885 2,676 2,757 3,330 1,882 4,971 843 2,630 2,396 1,298 Storm Duration Notes 6-HR 6-HR 24-HR 24-HR 24-HR 24-HR 6-HR 24-HR 6-HR 24-HR 24-HR 24-HR 24-HR 24-HR 24-HR 6-HR 6-HR 6-HR 6-HR Rainbow Wash FIS Q100=11,568 cfs (SLA 1994) From local regression, Q50 = 0.7478 * Q100 + 22.41 091337118 Technical Memorandum No. 3 Conceptual Drainage Report Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 Gila Bend Canal FDS (1991) Hydrology Results EXHIBIT 3B Conc. Point Drainage Area 2 (mi ) 12.98 12.54 10.55 0.52 10.08 6.30 9.73 0.75 CP1 CP2 CP3 CP9 CP10 CP11 CP16 CP17 Notes: * Q50 * (cfs) 4,263 4,393 4,325 489 4,253 3,332 4,470 618 Q100 q (cfs) 5,671 5,845 5,754 624 5,658 4,426 5,947 796 (csm) 437 466 545 1,200 561 703 611 1,061 Storm Duration Notes 24-HR 24-HR 24-HR 6-HR 24-HR Does not include flow split from B5 24-HR Does not include flow split from B5 24-HR 6-HR From local regression, Q50 = 0.7478 * Q100 + 22.41 091337118 Technical Memorandum No. 3 Conceptual Drainage Report Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 Gila Bend Canal FDS (1991) Hydrology Results EXHIBIT 3B Conc. Point Drainage Area 2 C70a C30b C73a C60c C82a C83a CC83a 75a C10b 10b C82b C74a CC30g C10a CC30c C32a C30c CC12a C14a C12a 12b C14b C14c C14d 73b C70e C20c CC74a C75a C70f C20f C20g C36b C60a CC40b C40b C60b C40c C64a 091337118 Technical Memorandum No. 3 Conceptual Drainage Report (mi ) 54.17 42.91 1.11 3.87 1.42 6.74 7.31 0.46 5.46 0.86 0.83 0.97 24.96 6.30 42.41 0.76 41.64 4.61 3.33 1.28 0.45 2.96 2.70 1.61 0.61 6.44 12.13 5.07 4.09 3.63 8.55 7.21 2.14 5.75 19.95 14.20 4.98 13.79 1.99 Q50 * (cfs) 2,966 2,444 502 1,021 632 1,008 1,020 363 1,471 562 459 433 1,923 1,434 2,465 440 2,465 1,250 945 711 420 980 1,007 789 490 1,255 927 1,236 1,038 1,004 850 874 698 1,149 1,700 1,573 1,197 1,598 629 Q100 q Time to Peak (cfs) 3937 3238 641 1336 815 1318 1334 455 1937 721 584 549 2541 1887 3266 559 3266 1642 1234 921 532 1281 1316 1025 625 1648 1209 1623 1358 1312 1107 1139 904 1507 2244 2074 1571 2107 811 (csm) 73 75 577 345 574 196 182 989 355 838 704 566 102 300 77 736 78 356 371 720 1182 433 487 637 1025 256 100 320 332 361 129 158 422 262 112 146 315 153 408 (hr) 15.67 16.75 5.00 12.75 4.58 14.17 14.17 4.58 12.92 4.58 4.67 4.92 14.50 13.42 16.08 4.75 16.08 5.17 5.50 4.83 4.50 5.00 4.75 4.75 4.50 13.50 13.83 13.08 5.33 5.42 14.00 13.08 4.67 13.58 15.75 16.00 13.08 15.58 5.00 Max Flow Model EC24NODK EC24NODK EC06DIKE EC24NODK EC06NODK EC24DIKE EC24DIKE EC06NODK EC24NODK EC06NODK EC06NODK EC06NODK EC24NODK EC24NODK EC24NODK EC06NODK EC24NODK EC06NODK EC06NODK EC06NODK EC06NODK EC06NODK EC06NODK EC06NODK EC06NODK EC24NODK EC24DIKE EC24NODK EC06NODK EC06NODK EC24DIKE EC24DIKE EC06NODK EC24NODK EC24NODK EC24NODK EC24NODK EC24NODK EC06NODK Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 Gila Bend Canal FDS (1991) Hydrology Results EXHIBIT 3B Conc. Point Drainage Area 2 C62a CC62a 82b C84a 36c 80b 81b C81a C80a 77b 78b 34b CC36a C36a C40a CC77a C77a C78a 74b C70g 70g C30g C34a C20d C30f CC20a C20a 72b C30a CC70b CC30b C71a C70b C70c C72a CC70c C20b C30d 32b 091337118 Technical Memorandum No. 3 Conceptual Drainage Report (mi ) 0.83 2.83 0.26 0.57 1.09 0.28 0.51 0.59 0.62 0.44 0.48 0.63 23.04 2.82 20.22 1.32 0.69 0.63 0.67 3.24 1.63 23.89 1.08 10.71 26.74 41.40 41.40 1.05 54.21 54.07 53.52 0.55 10.61 8.78 1.49 10.27 13.27 27.75 0.48 Q50 * (cfs) 514 793 298 308 547 325 393 370 484 421 458 378 1,879 803 1,695 656 382 388 481 1,047 629 1,850 363 901 1,896 2,472 2,423 709 2,966 2,973 2,973 289 1,439 1,404 628 1,454 894 1,866 520 Q100 q Time to Peak (cfs) 657 1031 368 382 702 404 495 465 617 533 582 476 2483 1044 2237 847 481 489 613 1370 811 2444 455 1175 2505 3276 3210 918 3937 3946 3946 357 1895 1847 810 1915 1165 2465 665 (csm) 792 364 1415 670 644 1443 971 788 995 1211 1213 756 108 370 111 642 697 776 915 423 498 102 421 110 94 79 78 874 73 73 74 649 179 210 544 186 88 89 1385 (hr) 4.50 4.83 4.33 4.58 4.75 4.33 4.50 4.67 4.50 4.42 4.42 4.67 14.00 4.83 16.08 4.83 4.75 4.83 4.50 5.08 5.00 14.58 5.42 13.17 15.00 15.83 16.33 4.42 15.67 15.50 15.50 4.25 14.50 14.33 4.75 14.25 14.75 15.75 4.33 Max Flow Model EC06NODK EC06NODK EC06NODK EC06NODK EC06NODK EC06NODK EC06NODK EC06NODK EC06NODK EC06NODK EC06NODK EC06NODK EC24NODK EC06NODK EC24NODK EC06NODK EC06NODK EC06NODK EC06NODK EC06NODK EC06NODK EC24NODK EC06DIKE EC24DIKE EC24NODK EC24NODK EC24UPRR EC06DIKE EC24NODK EC24NODK EC24NODK EC06NODK EC24NODK EC24DIKE EC06DIKE EC24DIKE EC24I-10 EC24NODK EC06NODK Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 Gila Bend Canal FDS (1991) Hydrology Results EXHIBIT 3B Drainage Area Conc. Point 2 (mi ) 8.04 7.56 10.09 27.14 1.10 1.61 C70d CC70e C20e C30e 14e C70h Notes: 091337118 Technical Memorandum No. 3 Conceptual Drainage Report * Q50 * (cfs) 1,437 1,444 923 1,880 722 606 Q100 q Time to Peak (cfs) 1892 1901 1204 2484 936 780 (csm) 235 251 119 92 851 484 (hr) 13.58 13.42 13.00 15.42 4.50 5.17 Max Flow Model EC24DIKE EC24DIKE EC24NODK EC24NODK EC06NODK EC06NODK From local regression, Q50 = 0.7478 * Q100 + 22.41 Maricopa County Department of Transportation Hidden Waters Parkway Corridor Feasibility Study February 2010 Hidden Waters Parkway Corridor Study: Watermelon Rd to I-10 EXHIBIT 3C. Derivation of Local Q50 vs Q100 Regression Equation 10C1 HEC-1 8C5 HEC-1 4C2 HEC-1 AVERAGE 9.12 4.76 16.93 5,503 4,311 5,994 4,544 7,252 5,523 24-HR 24-HR 24-HR 0.78 0.76 0.76 0.76 For studies with Q100 values but no Q50 results, recommend regression: Q50 = 0.7478 * Q100 + 22.41 (cfs) SR 85 HEC-1 Conc Pts 6,000 y = 0.7478x + 22.41 R² = 0.9913 5,000 4,000 Q50 (cfs) SR 85 Initial Drainage Report (1999) Flow Comparisons Drainage Area Q100 Q50 Storm Q50/ Conc. Analysis 2 (mi ) (cfs) (cfs) Duration Q100 Point Method 10.2-A2 HEC-1 0.30 186 148 0.80 7.5-H HEC-1 0.34 231 189 0.82 405 HEC-1 0.53 668 545 6-HR 0.82 15.20 HEC-1 1.09 914 733 6-HR 0.80 16C2 HEC-1 5.97 994 639 6-HR 0.64 1801 HEC-1 1.64 1,431 1,138 6-HR 0.80 408 HEC-1 6.47 1,619 1,229 6-HR 0.76 15C12 HEC-1 27.40 1,957 1,465 24-HR 0.75 9C1 HEC-1 4.83 1,973 1,571 6-HR 0.80 14C1 HEC-1 9.92 2,021 1,570 24-HR 0.78 404 HEC-1 3.87 2,149 1,685 6-HR 0.78 603 HEC-1 2.28 2,356 1,824 6-HR 0.77 16C3 HEC-1 5.05 2,371 1,803 6-HR 0.76 601 HEC-1 3.68 2,539 1,970 6-HR 0.78 1701 HEC-1 7.09 2,614 2,007 24-HR 0.77 411 HEC-1 6.03 2,767 2,139 6-HR 0.77 606 HEC-1 3.64 3,345 2,712 6-HR 0.81 13C2 HEC-1 36.11 3,383 2,498 24-HR 0.74 12C2 HEC-1 17.61 3,427 2,636 24-HR 0.77 15C13 HEC-1 37.41 4,032 2,576 24-HR 0.64 CD5 HEC-1 20.41 4,360 3,200 24-HR 0.73 11C1 HEC-1 10.84 4,451 3,159 24-HR 0.71 3,000 2,000 1,000 0 0 2,000 4,000 6,000 8,000 Q100 (cfs) Check against Precipitation Comparisons Storm 50-Yr 100-Yr Duration Precipitation Precipitation (hrs) (in) (in) 6 3.10 3.45 24 3.70 4.20 6 2.57 2.91 24 3.26 3.69 KHA Project No. 91337118 K:\PHX_Systems\091337118 MCDOT Hidden Waters Pkwy\Drainage\Spreadsheets\Offsite_Flows.xls P50/ P100 0.90 0.88 0.88 0.88 Study SR 85 Initial Drainage Report SR 85 Initial Drainage Report Luke Wash FDS Luke Wash FDS Page 1 of 1