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A Traditional vs. Ecosystem Services Approach to Surface Water
Management
September 16, 2010PRESENTED BY
Carol Murdock, Clackamas County WESMark Anderson, CH2M HILL
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Introduction / Context
• Ecosystem Services Approach to Facilities Planning – City of Damascus, OR
• How are we defining Ecosystem Services?• Could an ES services approach be cost effective in the
long-term?• Business Case Evaluation – cost/benefit analysis
– Environmental benefit – regulatory compliance– Community – livability, healthy environment– Economic – lower long-term cost to ratepayers, economic
growth• WES - Intent of BCE – inform policy decisions; develop
implementation mechanisms; provide information on long-term cost savings
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Clackamas County, Oregon – Rock Creek basin
Pilot Study Area
Rock Creek Basin Graphics courtesy Wikimedia, Clackamas County Service District #1 Rock Creek Watershed Action Plan, Brown and Caldwell
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Evergreen ForestDeciduous/Mixed Deciduous Forest
WetlandsRiparian Forest/Streams
Rock Creek basin has 4 major ecosystem types
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Mapped Ecosystem Extent and Quality
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Methods of managing urban ecosystems for stormwater treatment are not new
• Riparian Buffers• Conservation areas• Vegetated filter strips• Overland flow systems (NTS design)
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The key for basin planning is balancing land resources
• Ecosystems require land area but offer two benefits:– “Passive” benefits when land zoned for development is
preserved.
– “Active” benefits when ecosystem land manages runoff from development.
• When land area is treated as a “facility”, public support and decision-making are essential
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.
Active Benefits: RUSA meets TMDL limits for Roseburg wastewater discharge
• Similar ecosystem mix to Clackamas County
• Up to 70% slopes down to gentle slopes with a creek in incised valley bottom
• Minimal changes to existing ecosystem were required to provide adequate treatment
• DEQ-approved facility at 10% of the cost of built infrastructure
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Prioritization of Stormwater Control Strategies to Meet
Level of Service GoalsPRIORITY STRATEGY 1.
Use ecosystem services of protected areas
PRIORITY STRATEGY 2.Reduce development
footprint
PRIORITY STRATEGY 3.Uplift
PRIORITY STRATEGY 4.Maximize LID stormwater
controls
PRIORITY STRATEGY 5.Implement built infrastructure
We propose an integrated planning approach…
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Prioritization of Stormwater Control Strategies to Meet
Level of Service GoalsPRIORITY STRATEGY 1.
Use ecosystem services of protected areas
PRIORITY STRATEGY 2.Reduce development
footprint
PRIORITY STRATEGY 3.Uplift
PRIORITY STRATEGY 4.Maximize LID stormwater
controls
PRIORITY STRATEGY 5.Implement built infrastructure
LOS Met
Combined 5 Strategies = Total Stormwater
Management Solution
…that meets Level of Service goals
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A business case identifies credible strategies that compare to conventional runoff management
PRIORITY STRATEGY 1.Use ecosystem services
of protected areas
PRIORITY STRATEGY 2.Reduce development
footprint
PRIORITY STRATEGY 3.Uplift
PRIORITY STRATEGY 4.Maximize LID
stormwater controls
PRIORITY STRATEGY 5.
Implement built infrastructure LOS Met
Strategy 5.Business as Usual
LOS Met
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We use a mix of conventional models and new resource balance concepts
• Simple Method (runoff and pollutant load)• TR-55 (peak flows)• Clackamas County Pollutant Loadings Model
• A new land balance tool to manage ecosystem and development area flow and load trade-offs
• A new cost calculator that relates infrastructure, land, restoration, and ecosystem value to find efficient strategies
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Pilot study area characteristics – 167 acres
14% 5%
9%
15%5%
50%
2%
Butte ResidentialRural ResidentialNeighborhood LowNeighborhood MediumVillage EmploymentVillageVillage Core
27.7417%
38.6523%
0.130%
100.1360%
ForestRiparianWetlandsNon-Native/Non-built
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Summary of preliminary results
Strategy 1. Use ecosys-tem services of protected areas; 66%
Strategy 2. Reduce
develop-ment foot-print; 16%
Strategy 3. Uplift, 1%
Strategy 4. Maximize
LID stormwater
controls; 17%
Strategy 1. Use ecosys-tem services of protected areas; 59%
Strategy 2. Reduce de-velopment
footprint; 37%
Strategy 3. Uplift and use ecosystem services
of uplifted areas; 9%
TSS (LOS = 90% volume to 70% removal)
Runoff (LOS = 2x existing)
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Stormwater function by ecosystem type100-year flood
volume (gallons)Annual Runoff Volume
(gallons) 100-year Peak flow (cfs) TSS load (lbs)
Existing condition/LOS 83,343 164,216 0.4 63Zoned development (1 acre) 117,251 549,114 0.6 171Difference - amount that needs to be managed by stormwater system 33,908 384,898 0.2 108
Acres required to manage difference shown aboveEvergreen Forest A N/A 2.5 3.5 0.9Evergreen Forest B N/A 2.7 3.6 0.9Evergreen Forest C N/A 2.9 4.0 0.9
Deciduous Forest A N/A 2.5 3.5 0.9Deciduous Forest B N/A 2.7 3.6 0.9Deciduous Forest C N/A 2.9 4.0 0.9
Riparian corridor A 0.4 2.5 3.5 0.9Riparian corridor B 0.4 2.7 3.6 0.9Riparian corridor C 0.4 2.9 4.0 0.9
Wetlands A 0.4 0.1 <0.4 N/AWetlands B 0.4 0.1 <0.4 N/A
Non-native/non-built N/A 4.1 5.0 0.9
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Some early results
• About 3 acres of natural area will manage impacts from 1 acre of residential development, depending on zoning
• Uplift has little effect on treatment, but more important for volume – heavily dependent on assumptions
• Ecosystem areas can be valued monetarily to help drive market behavior.
• Assumptions about density and EDU buildout are highly sensitive
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General site design considerations
• Pre- and post-developed time of concentration• Typical slope• Limits of treatment area (due to topography, etc.)• Expected treatment infiltration loss (derived from
ClackCo model)• Expected pollutant capture rate• Treatment area characteristics and effectiveness
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Potential avenues for research and development
• Treatment effectiveness in varied natural conditions • Infrastructure costs
• Uplift costs
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Planned next steps
• Develop alternatives for BCE and policy selection
• Refine and implement planning framework for Damascus
• Engage with stakeholders to think about resource economics in a new way
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Acknowledgements
• City of Damascus, Oregon
• Oregon Department of Environmental Quality
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Questions or Comments?
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