stormwater: a new environment a new strategy
TRANSCRIPT
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Stormwater: A New Environment
A New Strategy
Overview
• Norfolk leading in developing adaptation strategies
• Current infrastructure conditions
• New normal—rainfall conditions are changing
• Adaptation approach
• Prioritization discussion
2
Government Funding Focus
• Federal Government• Coastal & river flood risk reduction
• US Army Corps of Engineers assists local gov’t to fund floodwalls, berms, etc.• Requires 35% local match
• Commonwealth of Virginia• Stormwater
• No-interest loans and small grant program to improve water quality and control water quantity
• Local Government• Stormwater quality and quantity management
• Coastal flood management
3
Norfolk Leadership: Innovation in Action
Dutch Dialogues VIRGINIA
4
Overdue for an Upgrade
• Design Standard➢ 10 year rain event—5.5
inches of rainfall within a 24 hour period
• Current System Capacity➢ 2 year rain event—3.5 inches
of rainfall within a 24 hour period
Current Stormwater System
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Rainfall Exceeding 2-year Rain Event
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The New Normal
• Heavy rainfall events are increasing
• Potential 20% increase in design standard➢Today’s 10yr is tomorrow’s 6yr
event
• More than 50% of rainfall events occur during elevated tidal events➢Making it difficult to clear the
systemP. Pomerenk Dec. 2016, Trends in Rainfall…
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Ground Conditions
PercentImpervious
Surface
• The yellow, orangeand red areas are mostly paved or hard—causing more water to run off more quickly
Current Conditions
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Citywide Trunk-line Capacity & Condition Analysis
Low PriorityMedium PriorityHigh Priority
Current Conditions
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Constrained Under Ground
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Storage Zone
Infiltration Zone
Green Infrastructure Best Practices Zones
Current Conditions
• Purple areas show where water can move into the ground using raingardens, pervious pavers, etc.
• Green areas show where the water table is high so that water will sit on top rather than move into the ground.
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Resilient Layered Strategy
Goal is to hold as much rain as close to where it falls as possible
• Retain
• Absorb
• Clean
• Release
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New Stormwater Retention Strategy• Increase underground capacity
• Pipes to increase flow and storage
• Cisterns
• Increase above ground capacity• Ponds/Wetlands
• Restored Creeks
• Bioswales
• Rain Gardens/Corner bumpouts
• Pervious Pavement
• Cisterns
• Rain barrels
• Increase system clearing ability• Pumps and force mains
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City Council Policy & Citizen Engagement Leading the Way
• Green Infrastructure Plan
• New Zoning Code
• Stormwater Fee Reduction program
• Vision 2100
• Retain Your Rain grants
• Adopt a drain program
• WAZE Connected Citizens Program
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Prioritization of Stormwater Projects
Current Methodology• Problem areas
• Capacity of existing systems
• Existing infrastructure
• Location of recently completed CIP or large projects
• Private property values
• Infrastructure conditions
• Classification of road
• Critical city infrastructure
• Economic development focus area
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Combined FY 2019 Operating and CIP Budget
Capital Projects$8,600,000
Infrastructure O&M$5,284,354
Debt Service$3,727,006
Street Sweeping$2,082,128
Engineering Program$1,883,541
Administrative Costs$1,330,571
Environmental Program$955,494
36%
4%
6%
22%
16%
9%
8%
Total FY 2019 Investment
$23.9 Million
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Council Discussion
What keeps Norfolk viable?
• Resident Concerns• Keep our houses from flooding
• Keep mobility
• Reduce neighborhood flooding
• City Prioritization?• Keep critical transportation networks clear
• Transformational projects
• Coordinate invest with large infrastructure projects
St. Paul’s Area Transformation
Ohio Creek: Upgrading existing systems
Fairmount Park
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New Revenue Investments
• $5M • 2 neighborhoods – master plan, trunk lines, 2 phases of construction
• St. Paul’s design & construction
• Upgrade equipment, operations and maintenance
• $10M• 4 neighborhoods - master plan, trunk lines, 3 phases of neighborhood construction
• St. Paul’s design & construction
• Upgrade equipment, operations and maintenance
• $15M• 4 neighborhoods - master plan, trunk lines, 4 phases of neighborhood construction
• St. Paul’s design & construction
• Add check valves to outfalls
• Upgrade equipment, operations and maintenance
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