SUSTAIN Pilot Study April 25, 2012 Curtis DeGasperi King County

System for Urban Stormwater Treatment and Analysis INtegration SUSTAIN

What is SUSTAIN? An ArcGIS-based framework designed to support evaluation and decision making: – How effective are green and/or gray treatment BMPs in reducing runoff and pollutant loadings? – What are the most cost-effective BMP options to meet specified water quantity and quality objectives?

Data Needs Land Use/Land Cover map in GIS Watershed model – Internal model in SUSTAIN – External model (Examples: HSPF, SWMM) BMP types, design configurations, costs Instream targets

Cost-Effectiveness Optimization Cost in Millions of Dollars Effectiveness (%Reduction)

Cost-Effectiveness Optimization Effectiveness (%Reduction) Cost in Millions of Dollars

SUSTAIN BMP Modeling Assumptions

SUSTAIN Aggregate BMPs On-site interception – Rain barrel – Cistern – Green roof On-site treatment – Bioretention – Porous pavement – Infiltration trench Routing attenuation – Vegetative swale – Conduit Regional storage/treatment – Wet Pond – Dry Pond

Land Use-BMP Treatments Natural Drainage Design

Land Use-BMP Treatments Natural Drainage Design + Gray Infrastructure

50 gallon rain barrel $220 unit cost including construction $ per yr I&E O&M assumed negligible Total Present Value unit cost = $1,533 ~3,000 gallon cistern $1,600 unit cost including construction $ per yr I&E O&M assumed negligible Total Present Value unit cost = $2,913 Residential On-site Detention Facilities 30-yr lifecycle cost assuming 5% discount rate

Bioretention Facilities 1 Unit is 100 ft 2 $20/ft 2 Design, permitting, and construction Rain Garden $ 1.10/ft 2 -yr O&M $ per yr I&E TPV cost = $69.73/ft 2 Roadside Bioretention $ 1.10/ft 2 -yr O&M $170 per yr I&E TPV cost = $63.04/ft 2 30-yr lifecycle cost assuming 5% discount rate

Porous Parking Areas 1 Unit is 100 ft 2 $ 20/ft 2 design, permitting, and construction $ 0.02/ft 2 O&M $ per yr I&E TPV = $85.95/ft 2 30-yr lifecycle cost assuming 5% discount rate

Detention Pond 1 Unit is ~13,000 ft 3 $ 3.43/ft 3 construction cost $ 1.20/ft 3 design and permitting $ 0.01/ft 3 O&M TPV Cost = $ 25.81/ft 2 or $ 4.78/ft 3 Land cost = $18.25 ft 2 30-yr lifecycle cost assuming 5% discount rate

BMP Cost Estimates Residential On-site Detention Facility Bioretention Porous Pavement Rain BarrelCustom designRain Garden Linear Roadside Design Unit Size 6.75 ft 3 (50 gal) 393 ft 3 (2,938 gal)100 ft 2 Total Present Value$ 1,533 /unit$ 2,913 /unit$ /ft 2 $ /ft 2 $85.95 / ft 2 Inspections/Enforcement$ /yr $ /yr$ /yr$ /yr Design and Permitting CostNA aaa Construction Cost$ 220/unit$ 1,600 /unit$ 20 /ft 2 Annual Operation and Maintenance Cost NA $ 1.1 /ft 2 $0.02 /ft 2 Land CostNA Table 1 Cost Assumptions for Low Impact Development BMPs (30-yr planning horizon with 5% discount rate) NA = Not applicable or assumed to be negligible.

Detention Pond Cost Estimates Detention Pond Commercial /Industrial Medium Density Residential Low Density Residential Design Unit Volume19,110 ft 3 12,852 ft 3 8,690 ft 3 Design Unit Area3,539 ft 2 2,380 ft 2 1,704 ft 2 Total Present Value (Design, Construction and O&M) $4.78 /ft 3 Design and Permitting Cost$ 1.20 /ft 3 Construction Cost$ 3.43 /ft 3 Annual Operation and Maintenance Cost $ 0.01 /ft 3 Land Cost a$ /ft 2 $ /ft 2 $ 6.50 /ft 2 Table 2 Cost Assumptions for Detention Ponds (30-yr planning horizon with 5% discount rate) NA = Not applicable or assumed to be negligible. a Land costs for wet ponds will vary depending on predominant level of development in basin, which is highly correlated with average land cost. There are three development level categories and three associated land costs.

Questions ?

SUSTAIN Pilot Catchment Study Results

Objectives Documentation – BMPs to be considered and associated treatment trains – BMP designs used in SUSTAIN – Cost assumptions used in model – Methods used to estimate road, rooftop and parking areas – Application of hydrologic target used in model – Extrapolation methods to biological and water quality improvements Describe general approach for expanding modeling effort beyond pilot catchment

Pilot Catchment Scale Study Green-Duwamish River Watershed Quality Assessment

Newaukum Urban Sub-basin Pilot study area Catchment NEW151

Newaukum Urban Sub-basin

Residential Rooftop and Commercial Parking Area Output Building Height Model Land Use/Land Cover

SUSTAIN Aquifers

Optimization Decision Variables High Pulse Count

Till Scenarios

Catchment NEW151 Very Poorly Drained Type D Soils

Rain BarrelsCisterns EIA only+80% PEIA only+80% PEIA only+80% PEIA only+80% P Rain BarrelsCisterns Green + Gray on Till Scenarios

BMP Cost Breakdown Green+Gray Treatment Train on Till Rain BarrelsCisterns EIA only+80% PEIA only+80% P

Green+Gray on Till Cost Breakdown Rain BarrelsCisterns EIA only+80% PEIA only+80% P

Cost-Effectiveness Curve Green+Gray on Till Scenario 15

In terms of High Pulse Count

In terms of Log-Linear Regression Model relating HPC to B-IBI

In terms of %ofMaximum B-IBI including uncertainty bounds (80% CL)

Water Quality Extrapolation SUSTAIN model includes TSS Extrapolate to turbidity, Cu and Zn using 95% Upper CL regression equations Calculate TSS, Total Cu and Total Zn load reductions Calculate frequency of exceedance of turbidity, Dissolved Cu and Dissolved Zn standards

Water Quality Extrapolation Selected “Best” of Best Scenarios Up to ~80% reduction in TSS loads Copper and Zinc loads reduced 30-40% Frequency of exceedance of turbidity standard reduced ~85% Copper was not predicted to exceed standards under current conditions A low frequency of exceedance of the Zn standard was effectively eliminated

Fully-forested (Pre-Dev) 50-yr return flow Fully-forested (Pre-Dev) 2-yr return flow x 0.5 Fully-forested (Pre-Dev) 2-yr return flow x 0.08 Flow Duration Curves Green+Gray on Till Scenario 15 EIA+80% Impervious RC = 0.0/hr

Fully-forested (Pre-Dev) 50-yr return flow Fully-forested (Pre-Dev) 2-yr return flow x 0.5 Fully-forested (Pre-Dev) 2-yr return flow x 0.08 Flow Duration Curves Green+Gray on Till Scenario 16 EIA+80% Impervious RC = 0.1/hr

Conclusions A variety of BMP treatment systems can meet similar targets at a variety of costs Generally, Green+Gray treatment trains performed better than Green only Effectiveness is highly dependent on assumptions regarding the fate of BMP infiltration

Recommendation Extend catchment modeling approach to a number of other catchments with relatively homogeneous land use/land cover

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Approach to Scaling Up

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