why is storm water a problem?
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Stormwater, Floodplain and Wetlands Newly Elected Officials Course January 28, 2006 Andrew W. Blenko, P.E., J.D. Why is Storm Water a Problem?. Increased runoff due to development (quantity and flooding). Why is Storm Water a Problem?. Development = Impervious Surfaces = Increased Runoff = - PowerPoint PPT PresentationTRANSCRIPT
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Stormwater, Floodplain and Wetlands
Newly Elected Officials Course
January 28, 2006
Andrew W. Blenko, P.E., J.D.
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Why is Storm Water a Problem?
Increased runoff due to development (quantity and flooding)
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Why is Storm Water a Problem?
Development =
Impervious Surfaces =
Increased Runoff =
Flooding
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Why is Storm Water a Problem?
Damage to your infrastructure:
Damage to your residents:
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Why is Storm Water a Problem?
Pollution from contaminants
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Why is Storm Water a Problem?
Pollution from illicit discharges
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Why is Storm Water a Problem?
Erosion and Sedimentation
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Why is Storm Water a Problem?
Reduced Groundwater Recharge
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Why is Storm Water a Problem?
Reduced Groundwater Recharge
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Persons who develop land must:• Assure the maximum rate of runoff is no greater after
development than before OR;
• Manage quantity, velocity and direction of resulting storm water runoff in a manner which otherwise adequately protects health and property from possible
injury.
Act 167 of 1978Pa. Stormwater Management Act
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Reading a Stream Hydrograph A hydrograph presents a picture of what is happening to the volume of
water in a stream during and after a rainfall event.
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Development increases the Amount of Runoff and Decreases Infiltration
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Development Increases the Velocity (Rate) of Runoff
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Development increases the Peak Flow Rate and decreases the Travel Time
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Traditional Approach has been to Detain Runoff so Peak Rate of Runoff is Maintained
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Traditional Approach has been to Detain Runoff so Peak Rate of Runoff is
Maintained
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New Approach Looks at Reducing Runoff Volume and Maintaining Quality of Stormwater
Runoff
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What is a Watershed?
• A contiguous land area that drains to a common point
• A Geographic Boundary, not a Political Unit
• Encompasses all water systems• Storm Water• Sanitary• Water Supply
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Watershed Characteristics:
• Slopes
• Vegetation
• Land Cover• Forest• Meadows• Pavement• Floodplains• Wetlands
•
• Hydrology
• Soils
• Land Use• Agriculture• Residential• Industrial• Open
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Many Municipalities are Living with Recurring Problems due to Poor
Stormwater Management in the Past –
Solutions must involve all communities in a watershed since
the problems cross municipal boundaries.
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Maintain Stream Capacity
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Stormwater Management Philosophy
Comprehensive
• Based on a Plan• Preventative• Multi-Purpose• Volume and Rate
Control Oriented
Traditional
• Remedial• Site Oriented• Conveyance
Oriented• Single
Purpose• Piecemeal
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Alternative Management Techniques
Municipal and Regional PlanningMunicipal and Regional Planning• Comprehensive Planning
• Open/Green Space• “Stormwater Space”• Acknowledge Act 167 SMPs in Plans• Regional Stormwater Facilities
• Zoning and Ordinances• Long-Term Property Buy-Out Plans in Floodplains• Law Suits over Upstream Stormwater Management
Practices
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Making Up for Past Sins:
Penn Township, Westmoreland County
Berlin Road Dam• Built to alleviate flooding of
approximately 20 homes, (including first floor flooding of 5 homes)
• Phase I included elliptical drainage pipes and wetland mitigation; construction costs were $238,000
• Phase 2 included a 5-acre detention facility to control stormwater from approximately 100 upstream acres
• Total Phase 2 construction cost of $451,000
• One of the first stormwater projects funded by PennVest
• Completed in 2002
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Making Up for Past Sins:
Penn Township, Westmoreland County
Cortina Marie Detention Pond
• Resulted from a law suit by 9 property owners repeatedly flooded
• Township purchased 5 acres of prime real estate for $404,000
• Total project cost including land acquisition, engineering, and permitting - $1.14 million
• Funded with a PennVest loan
• Completed in 2003
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Making Up for Past Sins:
Kennedy Township, Allegheny County
Pine Hollow Detention Basin• Protects the Township of Stowe
and the Borough of McKees Rocks
• Constructed 1998-99
• Cost $237,000
• Financed by the Allegheny County Authority for Improvements in Municipalities
• 5-year term
• All costs born by the Township of Kennedy
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Good Stormwater Management Saves Money!!!
We Need to be Creative and Think Outside the Box
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Stormwater Phase II Program
(Cities with <100,000 Population)
•MS4 – Municipal Separate Storm Sewer System
•Storm Sewer Discharges must be Permitted in Urban Areas
•Requires General or Individual Permit from PADEP
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Stormwater Phase II Program
Six Minimum Controls:
• Public Education and Outreach
• Public Participation and Involvement
• Illicit Discharge Detection and Elimination
• Construction Site Runoff
• Post-Construction Runoff
• Pollution Prevention/Good Housekeeping
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Stormwater Phase II Program
Public Education, Participation & Outreach
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Stormwater Phase II Program
Illicit Discharge Detection and Elimination
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Stormwater Phase II Program
Post-Construction Runoff Controls
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Stormwater Phase II Program
Municipal Good Housekeeping
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Wetlands
Rule One: Avoid Them!
• Wetland issues are regulated jointly by PADEP and the USACOE
• Wetlands are Beneficial
• Even a small disturbance requires regulatory review
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• 100 and 500-Year Floodplains delineated by FEMA in Flood Insurance Rate Study Maps
• Original maps in our area done in late 1970s
• Generally Updated every ten years
Floodplains
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LOMR – Letter of Map Revison
LOMA – Letter of Map Amendment
Floodplains
• Issued by FEMA as a result of Changed Condition
• Requires a HEC-RAS or other hydraulic study to Justify
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Floodway – cross section needed to convey runoff from design storms
Floodplain – Areas inundated with water during design storms
Floodplains
Never build in Floodway; Okay to build in Floodplain as long as first floor is above flood elevation and structure designed to withstand flooding
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Questions?
Thank you for your interest in serving your communities and making them a
better place to live and work!