Hydraulic Report. County Road 595 Bridge over Mulligan Creek. Prepared By AECOM Brian A. Hintsala, P.E

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1 Prepared for: Prepared by: Marquette County Road Commission AECOM Ishpeming, MI Marquette, MI December Hydraulic Report County Road 595 Bridge over Mulligan Creek Prepared By AECOM Brian A. Hintsala, P.E

2 AECOM i Contents 1.0 Introduction Method of Analysis Variables and Coefficients Starting Point Discussion Conclusion... 2 List of Appendices Appendix A HEC-RAS Computations Appendix B Profile Sheets Appendix C Topographic Map HEC-RAS River Sections Appendix D Bridge Plans Appendix E Cross Sections Appendix F Damage Waivers Appendix G Flow Rates Appendix H Site Photographs Appendix I USGS Topographical Map and River Gradient Calculations

3 AECOM Introduction This hydraulic report is being prepared for the Marquette County Road Commission concerning the proposed County Road 595 crossing of Mulligan Creek. The site is located in Section 26 of T50N, R29W, Quad Map Name Bulldog Lake (Lat /Long ) in Michigamme Township, Marquette County. Multiple road alignments were investigated and the chosen alignment requires construction of a new bridge at this site. There is no existing bridge at the site. 2.0 Method of Analysis The hydraulic analysis was performed using the HEC-RAS River Analysis System computer program, Version developed by the U.S. Army Corps of Engineers Hydraulic Engineering Center. The steady flow data for the flood events were obtained from the Michigan Department of Environmental Quality (MDEQ). 3.0 Variables and Coefficients The river sections near the bridge use an expansion coefficient of 0.30 and contraction coefficient of 0.50 which are suitable for a typical bridge per Table 3.3 of the HEC-RAS Hydraulic Reference Manual. The Manning s n-values for friction loss were selected using Table 3.1 of the HEC-RAS Hydraulic Reference Manual. The main channel is fairly uniform with some weeds so a value of was chosen. The overbanks are swampy areas covered with light to medium brush so a value of was chosen. Representative photographs of the site are included in Appendix H. 4.0 Starting Point The starting point of the analysis was a surveyed river section about 120 feet downstream of the proposed road. This location was chosen because it was far enough downstream to be outside of the influence of the proposed bridge. The starting water surface elevation was calculated by HEC-RAS using the slope-conveyance method. An average channel slope of was estimated from a USGS quadrangle map and used for the normal depth boundary condition. The calculations are included in Appendix I. 5.0 Discussion The main channel of the Mulligan Creek is variable in width and conveys about 50% of the flow up to the 10-year flood event. At the 100-year flood event, 60% to 70% of the flow is carried by the overbank floodplain. The river gradient is relatively flat and the flow regime is sub-critical for all flood events. The proposed bridge is a pre-cast concrete, three-sided culvert (ConSpan) with a span of 36 feet. Since the culvert is a buried structure, the normal road section is continued over the bridge. The concrete footings will be placed on the natural soils at the site which is likely to be ledge rock. The restored stream banks will be treated with heavy riprap which is sized and placed in accordance with the Michigan Department of Transportation 2003 Standard Specifications for Construction.

4 AECOM 2 The river cross sections are placed in HEC-RAS at the distances measured along the center line of the channel. In some cases the surveyed sections on each side of the bridge were adjusted up or downstream as required to model the bridge using the standard bridge/culvert input section of HEC- RAS. This is required because the actual location of the bridge was not known when the survey was performed. The final positions of the sections are shown in the plan view in Appendix C. The ConSpan three-sided arch can be modeled either as a culvert or as bridge in HEC-RAS. For this project, it was modeled as a bridge to better represent the natural stream channel. In addition, since HEC-RAS does not perform scour calculations for culverts, modeling the ConSpan as a bridge allowed scour calculations using HEC-RAS. Although the bridge spans the main channel without restriction, the proposed road approaches on each side of the bridge cut off a portion of the overbank flow during the higher flow events. Ineffective flow areas were included in the overbank portions of the cross sections upstream and downstream of the bridge as suggested in chapter 5 of the HEC-RAS Hydraulic Reference Manual. Placing the proposed road across the floodplain reduces the overbank conveyance and increases the water elevation upstream of the proposed bridge. With the proposed bridge in place there is an unacceptable increase in the water elevation at the last surveyed cross section upstream of the proposed bridge (HEC-RAS river station 424.) In order to gauge the severity of this problem, additional cross sections were extrapolated upstream using the last surveyed cross section and the estimated river gradient. The last extrapolated section is at river station 2013 where Mulligan Creek crosses the west boundary of Section 26. This is the limit of the property for which damage waivers related to an increase in flood stage have been obtained. At this location, there is no increase in 100- year flood stage for the proposed bridge when compared to the existing condition. Table 1 on the following page summarizes the key model results for two configurations: 1. The existing channel. 2. The proposed 36 span bridge. 6.0 Conclusion Analysis results indicate no increase in water surface elevation for the 100-year flow event for the proposed bridge. There is a minor increase in the channel velocity at the bridge for up to a 10-year flow event.

5 Hydraulic Comparison of Various Bridge Options 3 County Road 595 Bridge Design Mulligan Creek 4/4/2010 Table 1 HEC-RAS Analysis Results Velocity in Channel at Bridge Flow thru Bridge Water Surface Elevation at Upstream Face of Bridge River Station 251 Energy Gradient Elev at Upstream Face of Bridge Energy Gradient Elevation at 194' Upstream of Bridge Energy Gradient Elevation at 1783' Upstream of Bridge River Station 2013 River Station 230 River Station 251 River Station 424 (ft/sec) (cfs) (feet) (feet) (feet) (feet) 100 Year 10 Year 100 Year 100 Year 200 Year 100 Year 100 Year 100 Year Model Configuration (490 cfs) (200 cfs) (490 cfs) (490 cfs) (600 cfs) (490 cfs) Change (490 cfs) Change (490 cfs) Change Existing Condition Proposed Bridge

6 AECOM Appendix A HEC-RAS Computations

7 AECOM Computations The HEC-RAS data files are included in a separate electronic folder named: HEC-RAS_Mulligan.zip In order to provide a brief summary of the analysis results, a Profile Output Table for the existing and proposed conditions are included on the following pages.

8 HEC-RAS Plan: Exist River: MULLIGAN Reach: MAIN Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) MAIN Year MAIN Year MAIN Year MAIN * 10 Year MAIN * 100 Year MAIN * 200 Year MAIN * 10 Year MAIN * 100 Year MAIN * 200 Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year

9 HEC-RAS Plan: CNSPNRV21710 River: MULLIGAN Reach: MAIN Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) MAIN Year MAIN Year MAIN Year MAIN * 10 Year MAIN * 100 Year MAIN * 200 Year MAIN * 10 Year MAIN * 100 Year MAIN * 200 Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN 230 BR U 10 Year MAIN 230 BR U 100 Year MAIN 230 BR U 200 Year MAIN 230 BR D 10 Year MAIN 230 BR D 100 Year MAIN 230 BR D 200 Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year MAIN Year

10 AECOM Appendix B Profile Sheets

11 MULLIGAN CREEK Plan: Existing 4/5/2010 MULLIGAN MAIN Legend EG 200 Year WS 200 Year EG 100 Year WS 100 Year EG 10 Year Crit 200 Year WS 10 Year Crit 100 Year Crit 10 Year Elevation (ft) Ground Main Channel Distance (ft)

12 MULLIGAN CREEK Plan: CONSPAN-BRIDGE REVISED /5/2010 MULLIGAN MAIN Legend EG 200 Year WS 200 Year EG 100 Year WS 100 Year EG 10 Year Crit 200 Year WS 10 Year Crit 100 Year Crit 10 Year Elevation (ft) Ground Main Channel Distance (ft)

13 AECOM Appendix C Topographic Map HEC-RAS River Sections

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15 AECOM Appendix D Bridge Plans

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18 AECOM Appendix E Cross Sections

19 AECOM Cross Section Cross sections are included for the existing condition and the proposed bridge condition.

20 AECOM Existing Channel Condition

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29 AECOM Proposed Bridge Condition

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39 AECOM Appendix F Damage Waivers

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41 AECOM Appendix G Flow Rates

42 DEQ - Flood Frequency Discharges Page 1 of 1 12/6/2011 Joint Permit Application DEQ Home CIWPIS Online Services Permits Programs Site Map Contact DEQ Flood Discharge Request Record /6/2011 Home Water Management Lowflows Discharge Requests Watersheds Map Discharge Information Watercourse: MULLIGAN CREEK Location: Trail 5 Drainage Area: 3.87 mi 2 Basin Name: 45 - Dead Contributing Area: 3.87 mi 2 County: Marquette Tn/Rng/Sec: 50N29W/26 Township: Michigamme Latitude: Quad Name: Bulldog Lake Longitude: Quad ID: D11NW Requested By: Sheila Meier (DEQ-LWM- Received Date: 11/23/2011 Ishpeming) Request Type: Trans. - County Issued Date: 12/5/2011 File Number: Reference Number: U Discharge Frequencies: Volume Frequencies: 10%: 200 cfs 2%: 380 cfs 1%: 490 cfs 1%: 550 acre-ft 0.5%: 600 cfs 0.5%: 650 acre-ft 0.2%: 800 cfs Access to the Flood Flow Database is provided as a service to allow you to check the status of your flood flow requests or to view discharges from previous requests for preliminary design purposes. The discharges values are only valid for the original requestor and for one year after the original request date. To obtain discharge information from the Hydrologic Studies Program, a flood flow discharge request form may be submitted electronically to the DEQ. A written or response to your request will be returned to you and must accompany your permit application. Michigan.gov Home DEQ_Home Online Services Permits Programs Site Map Contact_DEQ State Web Sites Privacy Policy Link Policy Accessibility Policy Security Policy Copyright 2011 State of Michigan

43 AECOM Appendix H Photos

44 County Road 595 over Mulligan Creek 430 Downstream of Proposed Bridge Looking Upstream 430 Downstream of Proposed Bridge Looking Upstream

45 County Road 595 over Mulligan Creek 430 Downstream of Proposed Bridge Looking Upstream

46 AECOM Appendix I USGS Topographical Map and River Gradient Calculations Map includes portions of Quadrangle maps: Bulldog Lake Silver Lake Basin

47 087 56' 0.00" W ' 0.00" W ' 0.00" W ' 0.00" W ' 0.00" N CR 595/Mulligan 5m Intv. 5m Diff =16.4' dist = 1.34 Mi 7158' 16.4/7158= or 0.23% ' 0.00" N 16.4/6099'= or 0.27% ' 0.00" N ' 0.00" N ' 0.00" N ' 0.00" N ' 0.00" N ' 0.00" N W ' 0.00" W ' 0.00" W ' 0.00" W ' 0.00" W Copyright (C) 1999, Maptech, Inc.