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

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

Evergreen ForestDeciduous/Mixed Deciduous Forest

WetlandsRiparian Forest/Streams

Rock Creek basin has 4 major ecosystem types

Mapped Ecosystem Extent and Quality

Methods of managing urban ecosystems for stormwater treatment are not new

• Riparian Buffers• Conservation areas• Vegetated filter strips• Overland flow systems (NTS design)

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

.

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

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…

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

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

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

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

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)

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

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

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

Potential avenues for research and development

• Treatment effectiveness in varied natural conditions • Infrastructure costs

• Uplift costs

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

Acknowledgements

• City of Damascus, Oregon

• Oregon Department of Environmental Quality

Questions or Comments?

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