S.R. 0944, Section 015 (Wertzville Road) Bridge over the West Branch of Simmons Creek. Silver Spring Township Cumberland County.

Transcription

1 Hydrologic and Hydraulic Report For S.R. 0944, Section 015 (Wertzville Road) Bridge over the West Branch of Simmons Creek Silver Spring Township Cumberland County August 13, 2003 Prepared For Pennsylvania Department of Transportation Engineering District 8-0 Prepared By Lemoyne, PA Mt. Laurel, NJ Mountain Lakes, NJ Export, PA Allentown, PA Richmond, VA Charleston, WV Baltimore, MD New York, NY Columbia, SC Columbus, OH

2 Hydrologic & Hydraulic Report Silver Spring Township, Cumberland County S.R. 0944, Section 015 (Wertzville Road) Bridge over the West Branch of Simmons Creek August 13, 2003 TABLE OF CONTENTS Page I. PURPOSE... 2 II. UTILIZATION...2 III. EXISTING CONDITIONS... 2 IV. UPSTREAM STRUCTURES... 3 V. DOWNSTREAM STRUCTURE... 3 VI. PROPOSED CONDITIONS... 3 VII TEMPORARY STREAM CROSSING... 4 VIII HYDROLOGY... 4 IX. HYDRAULIC ANALYSIS... 5 X. RISK ASSESSMENT... 8 XI. SUMMARY DATA AND RECOMMENDATIONS... 9 PENNDOT SUMMARY DATA SHEET APPENDICES A. MAPS AND PLANS Project Location Map Drainage Area Map Soil Boundary Map Flood Insurance Rate Maps (FIRM) 100-Year Flood Plain in Project Area Stream Profiles Preliminary Structure Drawing Preliminary Roadway Drawings B. HYDROLOGY TR-55 PSU-IV Comparison C. HEC-RAS DATA FOR EXISTING CONDITIONS HEC-RAS Cross-Section Location Plan Stream Profile Plot HEC-RAS Summary Data Sheet Detailed HEC-RAS Output at River Station Rating Curve Plot at Station Stream Cross-Sections D. HEC-RAS DATA FOR PROPOSED CONDITIONS HEC-RAS Cross-Section Location Plan Stream Profile Plot HEC-RAS Summary Data Sheet Detailed HEC-RAS Output at River Station Rating Curve Plot at Station Stream Cross-Sections E. SITE PHOTOGRAPHS F. ELECTRONIC FILES G. TEMPORARY STREAM CROSSING Page 1 of 10 SITE-BLAUVELT ENGINEERS

3 Hydrologic & Hydraulic Report Silver Spring Township, Cumberland County S.R. 0944, Section 015 (Wertzville Road) Bridge over the West Branch of Simmons Creek August 13, 2003 I. PURPOSE The purpose of this report is to analyze the effects of the 2.33-year, 25-year, and 100-year storm event s flow elevations and velocities on the proposed replacement bridge carrying S.R. 0944, Section 015 (Wertzville Road) over the West Branch of Simmons Creek. The peak discharges for this analysis were determined based on the Soil Conservation Service Technical Release 55 (TR-55) Urban Hydrology for Small Watersheds. II. UTILIZATION This report is provided for those involved in the design and permitting process for the proposed structure discussed herein. The HEC-RAS and HY-8 analysis will provide the necessary information needed for rock lining design, temporary construction activities, and cost effectiveness evaluations. III. EXISTING CONDITIONS This project is located in a rural setting of Silver Spring Township, approximately 0.3 miles west of the town of Wertzville and 2.3 miles east of the town of Donnellytown. This project involves the replacement of an existing bridge carrying S.R. 0944, Section 015 (Wertzville Road) over the West Branch of Simmons Creek. The bridge is located approximately 0.15 miles west of the intersection of S.R and S.R. 0944, approximately one mile from I-81. A project location map is included in Appendix A. The bridge site is bounded by grazed pasture and brush with scattered trees to the north and lawn and ungrazed pasture to the south. (See Photos No. 2, 3 & 4 in Appendix E.) The surrounding land is rural and approximately 50% forested. Wetlands have been identified in the northwest quadrant of the structure. There are aerial utilities but no underground utilities within the project limits. Wertzville Road is a two-lane rural major collector that serves as a principal commuter route for Perry County residents. Consequently, daily traffic volumes are substantial (Current ADT = 12,464). The horizontal alignment through the project is tangent; the vertical alignment is on a sag curve. Traffic speeds are high through the bridge site. Traffic flow is constricted by a narrow bridge width. The existing structure is a single-span concrete slab bridge built in 1951 carrying S.R. 0944, Section 015 (Wertzville Road) over the West Branch of Simmons Creek. (See Photo No. 1 in Appendix E.) The existing bridge cartway is substandard with 2 lanes and no shoulders totaling The bridge has a clear span of 12-0, an underclearance of 6-6 and a skew. Structurally, the bridge is in poor condition, exhibiting concrete deterioration and evidence of scour on the upstream side. In addition, safety features (guide rail, bridge transitions, etc.) are substandard for the traffic volume and speeds. During site reconnaissance, evidence of high water was noted by debris on embankments and minor scouring of the structure walls and underside of the top slab. The stream is a minor mountain stream with moderate slopes and a well-defined channel. Upstream of the structure, the channel meanders with random locations of undercut embankment. Downstream of the structure, the channel is essentially on a tangent. The normal flow depth is approximately 5 inches. The average natural channel top width is between 15 to 20 feet and the channel depth varies from 2 feet to 4 feet. The channel bottom width varies from 4.5 feet to 7 feet and consists of shale bedrock. Upstream of the structure, the bedrock streambed is covered with gravel and cobbles with an average size of 4 to 5. Page 2 of 10 SITE-BLAUVELT ENGINEERS

4 Hydrologic & Hydraulic Report Silver Spring Township, Cumberland County S.R. 0944, Section 015 (Wertzville Road) Bridge over the West Branch of Simmons Creek August 13, 2003 The average channel bank slopes at 2H:1V upstream of the structure and at 4H:1V downstream of the structure. The upstream banks are comprised primarily of clay and silt. The downstream banks are grass covered. The upstream east overbank region is steep with brush and trees. The upstream west overbank is relatively flat with either grazed pasture or brush with trees. The downstream east overbank is lined with mowed grass and the west overbank is lined with tall grass. (See Photos No. 2, 3 & 4 in Appendix E.) Signs of drift and debris accumulation were seen on the embankments indicating high water elevations. The natural channel slope is approximately 1.05%. The West Branch of Simmons Creek is not listed in Design Manual, Part 2, Appendix 10.A as a stockable warm water trout stream. Simmons Creek is however listed in Title 25, Chapter 93 of the Pennsylvania Code Water Quality Standards as a Warm Water Fishery (WWF). From our initial contacts with the Pennsylvania Fish and Boat Commission, Mr. Donald Lauver, Southcentral Region Law Enforcement Manager indicated that there are no restricted dates or special restrictions on construction. A FEMA flood plain is not established for this project area. Copies of the surrounding FEMA maps are included in Appendix A. IV. UPSTREAM STRUCTURES The nearest upstream structure occurs over a private drive 106 upstream from the Wertzville Road project site. The structure location is shown on the Project Location Map in Appendix A. It is two (2) 30 corrugated steel pipes projecting from the embankment, carrying the West Branch of Simmons Creek under a one lane paved driveway. (See Photo No. 5 in Appendix E.) Based upon field observations it appears that the inlet and outlet embankments have scoured due to frequent flooding and overtopping of the road. V. DOWNSTREAM STRUCTURE The nearest downstream structure is located approximately 3000 (0.57 miles) downstream passing beneath S.R The structure location is shown on the Project Location Map in Appendix A. It is a single cell reinforced concrete box culvert under several feet of fill. The culvert has a normal opening 13-0 wide by 10-0 high, has a skew of approximately 80 and has concrete aprons at the inlet and outlet. (See Photo No. 6 in Appendix E.) Based upon field observations it appears that no flood damage has occurred and the crossing is in good condition. VI. PROPOSED CONDITIONS The existing bridge will be replaced by a single cell precast reinforced concrete box culvert having a 13-0 clear span normal to the walls and a 6-0 vertical clearance. The proposed roadway alignment at the new structure will be on a horizontal tangent, and sag vertical curve approximately matching the existing line and grade. The proposed structure will lie entirely within the horizontal tangent and vertical curve. The box culvert will be set parallel to the stream channel, at a skew angle measured with respect to the roadway centerline. The structure will carry one 12-0 left lane, one 12-0 right lane, and 8-0 shoulders with guide rail on the left and right sides. Roadway embankment slopes in the vicinity of the bridge will be 2H:1V. A roadway plan and profile, and preliminary structure drawings are included in Appendix A. Page 3 of 10 SITE-BLAUVELT ENGINEERS

5 Hydrologic & Hydraulic Report Silver Spring Township, Cumberland County S.R. 0944, Section 015 (Wertzville Road) Bridge over the West Branch of Simmons Creek August 13, 2003 The wing walls will be turned back from the stream at an angle of 30 with the exception of the northwest wing wall which will be turned back 45. R-7 rock scour protection will be placed around the wing walls and along the northwest channel embankment. Minor realignment to the upstream channel will be required due to additional culvert length over the existing to accommodate the increased roadway width. VII. TEMPORARY STREAM CROSSING A temporary crossing of the West Branch of Simmons Creek will be required to construct the S.R Culvert. A temporary road will be constructed downstream of the culvert to maintain traffic. The construction period is anticipated to be less than one year. Therefore, the temporary road is designed to convey the 2.33-year storm event without overtopping and withstand the 25-year event in accordance with S.O.L The temporary road crossing will have a top width of 28 feet (two 11-0 lanes, a 1-0 left shoulders, a 3-0 right shoulder and a 2-0 left traffic barriers) to accommodate two-way traffic with a 1.5:1 left side slope and a 3:1 right side slope. To convey the 2.33-year event without overtopping, one 48 inch diameter corrugated metal pipes is required. See the roadway plans and typical sections in Appendix A and the Temporary Stream Crossing Detail and design information in Appendix G for more detail. In order to minimize disturbance to the natural channel within the footprint of the temporary crossing, the channel will be covered with geotextile fabric on top of which the temporary road will be built. VIII. HYDROLOGY The watershed is part of the Susquehanna River Basin. The watershed drainage area of the West Branch of Simmons Creek to the proposed culvert crossing is square miles. Runoff flows in generally a southern direction to the project site. The drainage area is rural with 50% forest comprised primarily of deciduous trees and brush, grazed pasture, and cultivated and uncultivated fields. A negligible percentage of the area is residential. Carbonate rock is not present. There are no significant water storage areas within the watershed. The watershed consists primarily of hydrologic soil type C with some soil type B. No gage records or information is available for the West Branch of Simmons Creek. No detailed FEMA study has been performed. Based on PennDOT Strike-Off-Letter , the Soil Conservation Service Technical Release 55 (TR-55) Urban Hydrology for Small Watersheds was used for this location for ungaged watersheds. The 24-hour rainfall data was taken from PENNDOT s website. Hydrology computations are included in Appendix B. The following parameters were determined for the TR-55 Method: Drainage Area: sq. mi. U.S.G.S. Quad. Maps: Wertzville, PA BRIDGE Latitude: N Longitude: W WATERSHED Latitude: N Page 4 of 10 SITE-BLAUVELT ENGINEERS

6 Hydrologic & Hydraulic Report Silver Spring Township, Cumberland County S.R. 0944, Section 015 (Wertzville Road) Bridge over the West Branch of Simmons Creek August 13, 2003 Longitude: W Twenty-Four Hour Rainfall: 2.33 yr. = yr. = yr. = 7.35 Weighted CN Number: East Watershed = 58 West Watershed = 70 Flood discharges were determined as follows: Expected Discharge, Q (cfs) Recurrence Interval (Years) East Watershed West Watershed Total Watershed IX. HYDRAULIC ANALYSIS Existing Conditions The hydraulic analysis for the existing condition was completed using the Hydraulic Engineering Center U.S. Army Corp of Engineers HEC-RAS, Version 3.0 computer program. Peak discharges were taken from the TR-55 analysis. The flows of 91 cfs, 690 cfs and 1283 cfs were used for the 2.33, 25 and 100- year storms, respectively. This information, along with field survey data provided by GTS Technologies, Inc. was entered into the HEC-RAS computer program. The existing analysis was performed using surveyed cross sections starting from 469 downstream to 501 upstream of the proposed bridge replacement. A roughness coefficient of n=0.045 was used for the upstream channel and n=0.035 was used for the downstream channel based on field reconnaissance observation and values published in Open Channel Hydraulics (Chow 1959). For the upstream overbank conditions with brush and trees, a Mannings n of was used. For the upstream overbank conditions with grazed pasture and random scattered brush, a Mannings n of was used. For the downstream overbank conditions with uncultivated grassy fields and lawn, a Mannings n of was used. An expansion coefficient of 0.3 and a contraction coefficient of 0.1 were used for the natural channel. An expansion coefficient of 0.5 and a contraction coefficient of 0.3 were used to model the existing bridge. The starting normal depth upstream of the bridge is based on a channel slope of 1.05% and the starting normal depth downstream of the bridge is based on a channel slope of 1.05%. Mixed flow conditions were assumed for the hydraulic analysis as is verified by the results. The energy method was used to model channel flow and FHWA HDS 5 methodology was used to model the slab bridge as a culvert. Weir flow occurs over the roadway and pressure flow occurs at high water elevations. Weir flow is initiated at a flow of approximately 770 cfs which is slightly greater than the 25 year design storm frequency. The existing opening is 78.0 sf. Page 5 of 10 SITE-BLAUVELT ENGINEERS

7 Hydrologic & Hydraulic Report Silver Spring Township, Cumberland County S.R. 0944, Section 015 (Wertzville Road) Bridge over the West Branch of Simmons Creek August 13, 2003 Proposed Conditions The hydraulic analysis for the proposed condition was also completed using the HEC-RAS, Version 3.0 computer program. The field survey data and stream cross-sections prepared for the existing condition analysis were utilized for the proposed conditions, with data generated for the proposed structure replacing the existing bridge data. The same flows and stream conditions were used as for the existing condition analysis. The same expansion and contraction coefficients were also used. The proposed box culvert has a clear normal span of 13-0 and a minimum underclearance of 6-0 for a total opening of 78 sf which matches the existing total opening. The energy method was used to model channel flow and FHWA HDS 5 methodology was used to model the box culvert. Weir flow occurs over the roadway and pressure flow occurs at high water elevations which is not uncommon for culvert structures. Weir flow is initiated at a flow of approximately 810 cfs, which is slightly greater than the 25 year design storm frequency and slightly greater than existing conditions. Based on the requirements of PennDOT SOL and DM-2 Section for drainage areas between 0.5 and 1.5 square miles, the 25-year storm is the minimum frequency the culvert must pass. The proposed roadway alignment approximately matches the existing. The proposed box culvert was sized to pass the 25-year flood and meet FEMA flood plain requirements which allow no increase in the 100-year flood elevation (reference Chapter (e) of the Pennsylvania Code). As can be seen in Table 1 and 2 below, the stream profile in Appendix A, and additional HEC-RAS data provided in Appendices C and D, the proposed 100-year flood elevations are either identical or lower than the existing. For both the existing and proposed conditions, the maximum channel velocities are within the structure limits. For the existing condition, a maximum velocity of fps occurs through the bridge during the 100-year storm event. The proposed box culvert reduces this maximum velocity to fps by widening the opening and slightly reducing the slope. The upstream channel velocities in general are very similar to existing conditions. Downstream channel velocities are identical to existing conditions. Therefore, aggradation and degradation affects should not be significant. To protect the roadway embankment at the structure and upstream west stream bank, R-7 rock or equivalent scour protection will be provided around the wing walls and along the upstream west realigned channel. Page 6 of 10 SITE-BLAUVELT ENGINEERS

8 Hydrologic & Hydraulic Report Silver Spring Township, Cumberland County S.R. 0944, Section 015 (Wertzville Road) Bridge over the West Branch of Simmons Creek August 13, 2003 Cross-Section From Bridge TABLE 1 SUMMARY OF HEC-RAS DATA 2 nd X-Sect. Water Surface Elevations Velocities (ft./s) Upstream Downstream Upstream Downstream 1 st X-Sect. 1 st X-Sect. 2 nd X-Sect. 2 nd X-Sect. 1 st X-Sect. 1 st X-Sect. 2 nd X-Sect. River Station RS 1520 RS 1510 RS 1460 RS 1450 RS 1520 RS 1510 RS 1460 RS YEAR STORM Existing Condition Proposed Condition YEAR STORM Existing Condition Proposed Condition YEAR STORM Existing Condition Proposed Condition Minimum Elevation at Top of Existing Road = Minimum Elevation at Top of Proposed Road = Year Flood Velocity Through Proposed Bridge = ft./s Temporary Crossing Based on SOL , the temporary crossing must be designed to pass the 2.33-year event and withstand the 25-year event. The construction period will be less than one year. The hydraulic analysis for the temporary structure, required to maintain traffic, was completed using the FHWA Hydraulic Design of Highway Culverts HY-8, Version 6.1. The temporary structure will utilize one 48 diameter corrugated metal pipe. For analysis, the pipe invert was set 0.1 above the stream invert. The contractor can adjust this elevation as necessary. The high water elevation at the inlet is 5.40 above the pipe invert. The top of the temporary road at the inlet is 0.92 above the 2.33-year flood elevation, which is approximately equivalent to the desired 1.0. The top of the temporary road at the outlet is much higher than the top of pipe. The temporary embankment must be designed to withstand the 25-year storm event. The 25-year storm weir velocity is only 3.48 fps but the pipe outlet velocity is fps. Therefore, R-5 rock or larger with a permissible velocity of 11.5 fps should be used to line the temporary road embankment in accordance with the PA DEP Erosion and Sediment Pollution Control Program Manual. See Appendix G for a drawing and design information for the temporary structure. See the roadway plans and typical sections in Appendix A for additional information. Page 7 of 10 SITE-BLAUVELT ENGINEERS

9 Hydrologic & Hydraulic Report Silver Spring Township, Cumberland County S.R. 0944, Section 015 (Wertzville Road) Bridge over the West Branch of Simmons Creek August 13, 2003 X. RISK ASSESSMENT The proposed construction, embankment placed across the floodplain and relocated channel at the culvert inlet impacts the upstream water surface profiles and channel velocities. As can be seen in Table 2 below, the proposed construction has no increase in water surface elevations. Therefore, the proposed construction poses no additional risk. The proposed bridge will pass all floods up to and including the 25- year flood without overtopping the roadway. The total flow that can be passed is a slight improvement over existing conditions. Refer to Appendices C and D for additional tables comparing water surface elevations. Upstream Downstream Table Year Flood Comparison Flood Elevations (ft) River Station Existing Condition Proposed Condition Water Surface Change from Existing PIPES BRIDGE Channel velocities through the structure are reduced. The upstream channel velocities in general are very similar to existing conditions. Downstream channel velocities are identical to existing conditions. Page 8 of 10 SITE-BLAUVELT ENGINEERS

10 Hydrologic & Hydraulic Report Silver Spring Township, Cumberland County S.R. 0944, Section 015 (Wertzville Road) Bridge over the West Branch of Simmons Creek August 13, 2003 Therefore, aggradation and degradation affects should not be significant. To protect the roadway embankment at the structure and upstream west stream bank, R-7 rock or equivalent scour protection will be provided around the wing walls and along the upstream west realigned channel. XI. SUMMARY DATA AND RECOMMENDATIONS Summary Data: Drainage Area: Sq. Mi Year Flood: Magnitude 91 cfs 25-Year Flood: Magnitude 690 cfs Water Elev Velocity fps 100-Year Flood: Magnitude 1283 cfs Water Elev Velocity fps Recommendations: 1. Based on the roadway alignment and profile presented in this report, a precast reinforced concrete box culvert will be constructed meeting the following criteria: Single cell box with a 13-0 normal clear span, a 6-0 minimum vertical clearance and a 78 sf opening. Skew: Roadway width of 40-0 clear between guide rail. 2. Provide wing walls angled at 30 and Provide R-7 Rock or equivalent scour protection around the wing walls and along the northwest channel. Page 9 of 10 SITE-BLAUVELT ENGINEERS

11 Summary Data Sheet Location Data County Cumberland Municipality Silver Spring Twp. Location - U.S.G.S. Map Wertzville State Route - Section SR Latitude N 40 17' 00" Station Longitude W 77 02' 45" Segment/Offset 0520/0000 Present ADT: 12,464 Year: 2003 Future ADT: 18,891 Year: 2024 River Basin (US-ACOE) Ohio, Delaware, Susquehanna, Great Lakes Channel Data Stream Name West Branch of Side Slope Left: 4H:1V Simmons Creek (looking downstream) Right: 2H:1V Stream Slope 1.05% Type of Channel Trapezoid Normal Stream Flow Depth 5" Average Top Width 15' to 20' Stream Bed Elevation at Inlet 484.6' Average Bottom Width 4.5' to 7' Stream Bed Elev. Exact Dist ' Stream Bed Elev. Exact Dist ' ~500' upstream Elevation ' ~500' downstream Elevation 480.5' Average Stream Channel Depth 4' High Water Elev. and Date Unknown Hydrology Hydrology Method Used Drainage Area Q2.33 (CFS) Q25 (CFS) * Q100 (CFS) PennDOT Study TR sq. mi. 91 cfs 690 cfs 1283 cfs FEMA (if applicable) Other: Hydraulics EXISTING STRUCTURE PROPOSED STRUCTURE Bridge Type Single Span Slab Bridge Type Box Culvert Clear Span - Centerline 12'-0" Clear Span - Centerline 13'-0" Clear Span - Normal 12'-0" Clear Span - Normal 13'-0" Skew 90 00' 00" Skew 90 00' 00" Minimum Underclearance 6'-6" Minimum Underclearance 6'-0" Length of Channel Impacted 29'-0" Length of Channel Impacted 44'-6" Number of Spans 1 Number of Spans 1 Low Chord Elevation ' Low Chord Elevation 490.6' Hydraulic Method Used Energy Hydraulic Method Used Energy (HEC-RAS) Return Period* Q WSE Velocity Return Period* Q WSE Velocity cfs ' 5.57 '/s cfs ' 3.95 '/s cfs ' '/s cfs 492.1' '/s cfs ' '/s cfs ' '/s Overtopping 770 cfs ' '/s Overtopping 810 cfs ' '/s *Indicate Design Return Period with a at the appropriate year. Or if year is not shown, fill in Design Return Period in blank row. Form Version: 7/16/2001 Page 10 of 10

12 APPENDIX A MAPS AND PLANS

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21 SR944 Plan: 1) New Box 2) Existing Legend WS 100-Year - New Box WS 100-Year - Existing WS 25-Year - Existing WS 25-Year - New Box Ground Elevation (ft) Main Channel Distance (ft)

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29 APPENDIX B - HYDROLOGY

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64 APPENDIX C HEC-RAS DATA FOR EXISTING CONDITIONS

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87 APPENDIX D HEC-RAS DATA FOR PROPOSED CONDITIONS

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108 APPENDIX E SITE PHOTOGRAPHS

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110 Hydrologic & Hydraulic Report Silver Spring Township, Cumberland County S.R. 0944, Section 015 (Wertzville Road) Bridge over the West Branch of Simmons Creek August 13, 2003 Photo 1 - Downstream Face of S.R Structure, Looking North Photo 2 Looking Upstream (North) from S.R Structure

111 Hydrologic & Hydraulic Report Silver Spring Township, Cumberland County S.R. 0944, Section 015 (Wertzville Road) Bridge over the West Branch of Simmons Creek August 13, 2003 Photo 3 - Looking Upstream (North) at Tributary from S.R Structure Photo 4 Looking Downstream (South) from S.R Structure

112 Hydrologic & Hydraulic Report Silver Spring Township, Cumberland County S.R. 0944, Section 015 (Wertzville Road) Bridge over the West Branch of Simmons Creek August 13, 2003 Photo 5 Upstream Face of Nearest Upstream Structure Photo 6 Upstream Face of Nearest Downstream Structure

113 APPENDIX F ELECTRONIC FILES

114 APPENDIX G TEMPORARY STREAM CROSSING

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