Greening the Region Using Stormwater Infrastructure

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Greening the Region Using Stormwater

Infrastructure

May 7, 2014Jim Simmonds

King County Water and Land Resources [email protected]

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Stormwater ParadigmTime Period Paradigm Description

Prior to 1992 Drainage Efficiency

Convey water downhill as efficiently as possible

1992 – 2013 Reduce New Impacts

Reduce harm from new construction with flow control and treatment

Future Reduce New and Existing Impacts

Capture, infiltrate, detain, and treat stormwater everywhere to protect and rehabilitate receiving waters

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Parcels Built Before

Stormwater Controls Required

About three-fourths of urban lands lack stormwater facilities5/7/2014

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Stormwater Retrofit Examples

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Ponds

Bioswales

Check Dams

Cisterns

Pervious Pavement Rain Gardens

Green Roofs

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Estimated Stormwater Needs $3B - $15B for treatment in Puget Sound

Capital costs, no O&M, no land costs $1.4B for Juanita Creek basin (7 sq miles)

Full lifecycle cost $1.1B for 64 small basins in

unincorporated King County Full lifecycle costs

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Stormwater Retrofit Planning for WRIA 9

$1M grant from EPA, $335K match 4 years Model stormwater retrofit needs in WRIA 9 Work with stakeholders Present retrofit options analysis to WRIA 9

Watershed Ecosystem Forum Extrapolate cost estimates to all Puget

Sound

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Project Benefits

Planning-level estimate of facility and funding needs

Cost vs stream improvement Demonstrate use of modeling tools Influence capital project planning Influence future NPDES permits Influence discussion on new funding

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Approach

Gather geospatial data about existing stormwater facilities, soil, precipitation

patterns, slope, impervious area, development type, land costs, stream channels

Conduct hydrologic modeling Model hydrologic improvements with

stormwater facilities

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Future Development2007 Satellite-Derived Land Use (UW 2007)

2040 Simulated Land Use (Alberti 2009)

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SUSTAIN: System for Urban Stormwater Treatment and INtegration

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Modeling Approach

Study area: 278 mi2, 446 catchments Model 135 hypothetical 100-acre catchments

representing combinations of: 5 generic land uses 3 soil types 2 slopes 3 precipitation zones 2 land costs

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SUSTAIN Optimization Target: Reduce Stream Flashiness

High Pulse Count: Number of times mean daily flows ≥ high-flow threshold set at 2 X long-term mean daily flow rate

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High Pulse Count and

Biology

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Biological Condition B-IBI RangeExcellent 46 – 50

Good 38 – 44

Fair 28 – 36

Poor 18 – 26

Very Poor 10 – 16

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Addressing Redevelopment Redevelopment improves stormwater

management Nearly ½ of project area to have new or re

development by 2040 More expected beyond 2040 Decreases estimated need

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Addressing Climate Change Three approaches for assessing impacts

Analysis of precipitation patterns for downscaled global climate model output

Impacts of climate change on hypothetical pond sizing

Impacts of climate change on high pulse count in hypothetical basin

Likely need about 10% more flow control, but model variability is large

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2040 Potential B-IBI ScoresNo Stormwater Management

Full Stormwater Management

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Policy and Planning Horizon are Everything

How stringent are stormwater requirements for redevelopment?

How aggressively do public programs build facilities?

How long in the future do we aim for success?

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What If?

Assume new and redevelopment builds on-site facilities and developers contributes funds to build off-site facilities (ponds)

Assume public funds used to build everything else

Assume all stormwater facilities built within either 30 years

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Annual Public CostsCapital Operation

and Maintenance

Inspection and Enforcement

New and Re-Development

$88M $4M $320M

Roads and Highways

$21M $19M $28M

Everything Else

$98M $89M $170M

Total $207M $112M $518M

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The Big Questions

How quickly do we want to improve stream flows and water quality?

To what degree do we want to improve stream flows and water quality?

Where does capital funding come from? Where does operating funding come from?

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Project Team Don Robinett, SeaTac Ben Parrish, Covington Chris Thorn, Auburn Jeff, Burkey, Curtis DeGasperi, David Funke, Larry

Jones, Chris Knudson, Beth leDoux, Doug Navetski, Elissa Ostergaard, Giles Pettifor, Dan Smith, Allison Vasallo, Mark Wilgus, Olivia Wright, King County

Rich Horner, Erkan Istanbullouglu, UW Ed O’Brien, Mindy Roberts, Ecology Dino Marshalonis, Michelle Wilcox, EPA Tamie Kellogg, Kellogg Consulting5/7/2014