ASDSO NE Regional 2009 Presentation
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The document summarizes spillway upgrades done for three Pennsylvania high hazard dams - Ironworks Dam, Poe Dam, and Youngman Dam - whose spillway capacities were found to be inadequate. For each dam, the document discusses the dam's history, previous findings of inadequate capacity, alternatives evaluated, and the upgrading approach selected. The selected approaches were raising the dam and expanding the auxiliary spillway at Ironworks Dam, armoring the embankment at Poe Dam, and raising the dam with a vinyl sheet pile parapet at Youngman Dam.
ASDSO NE Regional 2009 Presentation
- 1. When the Cookie Cutter Wont Cut It Case Histories of Spillway Upgrades for Three Pennsylvania High Hazard Dams ASDSO NE Regional Conference State College, Pennsylvania June 14, 2009 Jeremy R. Young, P.E. & Gregory S. Paxson, P.E Schnabel Engineering, West Chester, Pennsylvania
- 2. Introduction - Purpose Discuss 3 Pennylvania High Hazard Dams found to have Inadequate Spillway Capacity Facilities and drainage areas are similar Different Upgrading Concepts Applied to Each Site to Comply with PADEP Dam Safety Regulations
- 3. Project Locations Ironworks Dam Aqua PA Bucks County Youngman Dam WMWA Lycoming County Poe Dam PA DCNR Centre County
- 4. Project Comparison * Top of 3 ft high parapet Ironworks Dam Youngman Dam Poe Dam Max Dam Ht (ft) 51 95 33 Normal Storage (ac-ft) 1900 1600 460 Constructed 1941 1951 1935-38 Drainage Area (mi 2 ) 5.7 2.1 4.9 CN 79 67 65 Lag Time 0.8 0.4 1.2 24-hr PMP (in) 34.4 32.4 33.0 PMF Inflow (cfs) 44,900 20,400 28,000 Spillway Type Masonry Ogee/ Earth Auxiliary Concrete Ogee Masonry Ogee Spillway Length (ft) 110/200 70 60 Normal Freeboard (ft) 7/10* 8 9 Spillway Capacity (% PMF) 40/65* 60 20
- 5. Ironworks Dam Bucks County 51 High Earthen Embankment Masonry Parapet Concrete Corewall to Rock Primary Spillway 110 Long Curved Masonry Ogee Weir Auxiliary Spillway 200 wide Excavated Earthen Channel Concrete Control Section Founded on Rock
- 6. Ironworks Dam Site Layout Primary Spillway Embankment Aux. Spillway Central Dike Intake Tower Photo courtesy of Aqua PA
- 7. Ironworks Dam History Designed by Phila. Suburban Water (Water Supply) Began Construction in 1941 First Filling Completed by 1944 Owned by Aqua Pennsylvania Satisfactory Performance since First Filling Modifications Primary Spillway Outlet Channel Stabilization
- 8. Ironworks Dam Previous Findings 1978 Phase I Inspection Report Spillway Capacity 70% PMF Inadequate Wet Zone at Downstream Toe Displaced/Cracked Parapet July 2000 PADEP Letter Updated Hydrology (HMR 51/52, NRCS) Spillway Capacity <50% PMF Recommended Upgrading Spillway Capacity
- 9. Ironworks Dam 2001 Alternatives Evaluation Updated Hydrology and Hydraulics Spillway Capacity ~ 65% PMF (at top of parapet) Various Alternatives Evaluated Modifying Primary Spillway Not Feasible Embankment Armoring Not Cost Effective Modifying Parapet Required Modifying Aux Spillway Corewall Anchoring Reqd
- 10. Auxiliary Spillway Core Wall
- 11. Ironworks Dam 2001 Concept Raise Training Walls Raise Central Dike Remove Existing Parapet Construct New 6 ft high Parapet (Raise Dam by 3 ft) and backfill 2 ft Anchor Existing Corewall Photo courtesy of Aqua PA
- 12. 2001 Concept Raised Top of Dam and Computed PMF Peak Stage Requires a PADEP Dam Permit and Flood Easements from Upstream Property Owners Design Constraint No Easements Maintain Existing Top of Dam or Maintain Computed PMF Peak Stage Ironworks Dam 2004 Alternatives Evaluation
- 13. Additional Alternatives Evaluated Labyrinth Spillway in Auxiliary Spillway Channel Not Cost Effective Crest Control Devices in Auxiliary Spillway Cost Prohibitive, Maintenance Required Armoring Portion of Embankment + Raising Not Cost Effective Expand Auxiliary Spillway + Raising Ironworks Dam 2004 Alternatives Evaluation
- 14. Ironworks Dam 2005 Design Raise Training Walls Raise Central Dike Remove Existing Parapet Raise Dam Crest 6 Constr. New 5 Parapet (4.5 exposed) to Existing PMF EL Expand Aux. Spillway 100 Anchor New and Existing Corewall Photo courtesy of Aqua PA
- 15. Ironworks Dam Construction (2006-2007) Construction Cost: $1.6M (Bid=$1.5M) Additional Work Downstream Drainage System Riprap on Downstream Slope Misc Site Drainage
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- 19. Poe Dam Centre County 33 High Earth Embankment Zoned Embankment w/ a Rock Toe Rock Toe not Clearly Identified During 2005 Investigation Primary Spillway 60 Long Masonry Ogee and Chute Rock Cut Outlet Channel 30 Dia. CMP Outlet Conduit Encased in Concrete
- 20. Poe Dam Site Layout Outlet Tower Primary Spillway Photo from Windows Live Local Embankment
- 21. Poe Dam History Constructed 1935-38 by the Civilian Conservation Corps Owned by PA DCNR Poe Valley State Park Reports of Embankment/Spillway Seepage Since Late 1960s No Major Post Construction Modifications
- 22. Poe Dam Previous Findings 1980 Phase I Inspection Report Spillway Capacity 75% PMF Inadequate Seepage Near Outlet Conduit and Spillway Corrosion of CMP Outlet Conduit ~2000 PADEP Requested a Seepage Evaluation Recommended Upgrading Spillway Capacity
- 23. Poe Dam 2002 Evaluation Updated Hydrology and Hydraulics Spillway Capacity ~ 20% PMF Various Alternatives Evaluated Expanding Primary Spillway Not Cost Effective Excavated Earthen Spillway Not Feasible Labyrinth Spillway Not Cost Effective Embankment Armoring Low Visual Impact + Maintained Existing Hydraulics
- 24. Poe Dam Upgrading Approach RCC Armoring Replace Outlet Tower Parapet Photo from Windows Live Local Slipline and Extend Conduit Grout Spillway
- 25. Poe Dam Construction (2008 2009) Bid = $3.7M Additional Work Seepage Collection & Monitoring Amphitheater Boat Ramp Access Bridge to Tower
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- 29. Youngman Dam Lycoming County 95 High Earth Embankment Primary Spillway 70 Long Concrete Ogee w/ Concrete Chute on Right Abutment
- 30. Youngman Dam Site Layout Outlet Tower Primary Spillway Photo from Google Earth Embankment
- 31. Youngman Dam History 1951 Construction Owned by Williamsport Municipal Water Authority as a Water Supply Facility History of Seepage in Spillway and at Downstream Toe Spillway Grouting Program in 1980
- 32. Youngman Dam Previous Findings 1977 Phase I Inspection Report Adequate Spillway Capacity* Seepage recommended instrumentation 2001 PADEP Letter Updated Hydrology (HMR 51/52) Spillway Capacity ~60% PMF Identified Seepage in Spillway and Possible Undermining Recommended Evaluation of Spillway Integrity and Capacity
- 33. Youngman Dam 2003 Spillway Integrity Evaluation Coring Program and Geophysical Survey Clogged Drainage System Failure of Waterstops at Some Joints Significant Undermining not Observed Recommended Improving Slab Stability at Joint Below the Ogee Repair Leaky Joints Rehab Drainage System
- 34. Youngman Dam 2003 Alternatives Evaluation Replacement Labyrinth Spillway Not Cost Effective Embankment Armoring Not Cost Effective Given Embankment Ht. Raising Top of Dam (~4 ft) Earthfill was not Feasible due to Crest Width Concrete Parapet Vinyl Sheet Pile Parapet
- 35. Youngman Dam Upgrading Approach Parapet Replace Pedestrian Bridge Photo from Google Earth Grout Spillway Repair Joints Slipline Wall Drain Additional Slab/Wall Drain
- 36. Youngman Dam Construction (2007-2008) First use of Vinyl Sheet Pile Parapet in PA Bid=$1.1M Additional Work Weighted Filters at Downstream Toe Work Coincided with Spillway Repairs and Replacement Control House at Heller Dam
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- 41. Case Study Comparison Ironworks Poe Youngman Selected Rehab Alternative Raise Dam + Expand Aux. Spillway RCC Embankment Armoring Raise Dam with Vinyl Sheet Pile Parapet Cost $1.6M $3.7M $1.1M Design Constraints & Objectives Modifications to Parapet and Aux. Spillway Reqd Seriously Inadequate Spillway Capacity Large Drainage Area, Small Lake Small Drainage Area, Large Lake Cost effective, low impact solution
- 42. Questions