schoharie creek and gilboa dam - welcome to … dam • impounds the waters of schoharie creek •...
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SCHOHARIE CREEK AND GILBOA DAM
SCHOHARIE CREEK AND GILBOA DAM
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GILBOA DAMGILBOA DAM
DAM IS COMPRISED OF AN EARTHEN EMBANKMENT AND CONCRETE SPILLWAY
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GILBOA DAMGILBOA DAM
• Impounds the waters of Schoharie Creek • 314 sq. mi. of watershed area• 19.5 billion gallons of useable capacity• Spillway/Dam crest elevation = 1130’
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• 1130.0 feet - cresting of reservoir
• 1132.0 feet - flood stage - minor
• 1133.0 feet - moderate flood stage
• 1135.0 feet - major flood stage
• 1136.6 feet - historic flood elevation
CRITICAL RESERVOIR ELEVATIONSCRITICAL RESERVOIR ELEVATIONS
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DAM ANALYSIS - BACKGROUNDDAM ANALYSIS - BACKGROUND
1998-2003 Gilboa dam analysis as part ofDEP review of all dams
• 2004 - design phase began
• 2005 - review of safety factors• 1996 - historical flood factor
• Re-evaluation of safety factors in light of recent climatological events
• Findings yield safety factor less than minimum recommended
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ACTIONS IN RESPONSE TO RISKACTIONS IN RESPONSE TO RISK
• IMMEDIATE
• SHORT TERM - 30 days to 18 months
• LONG TERM - total dam reconstruction -scheduled for 2010 (under review)
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ACTIONS IN RESPONSE TO RISKIMMEDIATE
ACTIONS IN RESPONSE TO RISKIMMEDIATE
• Reduction of reservoir level
• Monitoring• NWS - advanced hydrological production service (AHPS)
• Heightened with DEP police every two hours
• WOH every shift
• Borings• Mobilizing now; completed in 10 weeks
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ACTIONS IN RESPONSE TO RISKSHORT TERM
ACTIONS IN RESPONSE TO RISKSHORT TERM
• Install extensive monitoring equipment• Flow and pressure gauges• Alarms• Lighting• Monuments
• Strengthening by vertical anchors
• Notching
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SPILLWAY REPAIR SCHEDULESPILLWAY REPAIR SCHEDULE
• Design Basis• Meet DEC Dam Safety Stability Criteria• Subsurface Borings/Testing in North Lawn Area
• Interim Repair Construction Schedule• Design/Permitting Phase: 10 weeks• Contractor Ready to Mobilize: Mid-January• Anchor Installation*: 6-9 months• Spillway Notch Construction**: 1 month
• Total dam reconstruction 2010 (under review)
* Anchor Installation dependant on non-spill condition** Spillway Notch construction requires reservoir level to be below crest
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EMERGENCY ACTON PLAN (EAP)EMERGENCY ACTON PLAN (EAP)
“EAP sets forth basic procedures, duties, and responsibilities to be implemented by DEP and other public safety personnel in the event of an emergency condition at the dam.”
Emergency Condition: “an impending or actual sudden, uncontrolled release of water caused by an incident or accident to, or failure of project structures.”
EAP Definition
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EMERGENCY ACTON PLAN (EAP)EMERGENCY ACTON PLAN (EAP)
EMERGENCY SITUATIONS – A & B• Situation “A”
• Failure of the dam is imminent or has occurred
• Initiate Notification procedures immediately with the highest warning (evacuate impacted downstream areas)
• Situation “B”• A potentially hazardous situation at the dam is developing
• Recommend initiating Notification procedures (partial evacuationof areas where reaction time is limited) and emergency repair activities
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Q&AQ&A