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ASDSO NE Regional 2009 Presentation


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When the Cookie Cutter Won’t Cut It

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ASDSO NE Regional 2009 Presentation

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