View
645
Download
0
Category
Tags:
Preview:
Citation preview
Urban Subwatershed Stormwater Retrofit Analysis (SRA)
Shawn TracyRestoration SpecialistMetro Conservation Districts (MCD)
MCD SWCD’sAnoka – Carver – Chisago – Hennepin – Isanti – Ramsey – Scott – Sherburne – Washington - Wright
MCD
Anoka
Carver
Chisago
Hennepin
Isanti
Ramsey
Scott
Sherburne
Washington
Wright
MCDLRP
Ecological Restoration
Stormwater BMP Design
Education
Subwatershed Stormwater Assessment
Conservation District
WMO/WD
Cities &
Residents
Sub-WSRestoration
Urban
Rural/Ag
Dan Anderson: http://www.flickr.com/photos/stonebridgedapper/
Google Earth
Defining our task
What it isUrban stormwater retrofittingIdentification of the highest value stormwater BMP retrofit practices by location (e.g., $/LB-TP/YR)A Water Quality planning toolSupplement to existing analysesOne (major) consideration in Capitol Improvement planningA Precise and relative modelLabor investment and quantity/quality of geospatial and W.Q. data affects accuracy
It is not…a hydraulic or storm sewer analysis/planning tool…primarily used for street-scaping or park development (secondary benefit)…an elaborate excuse just to get in more raingardens
Defining our task
Why an SRA?Massive effort needed to affect change in WQDisproportionate (insufficient) funding resourcesDisproportionate (insufficient) labor resourcesTMDL implementation guidanceAssurance of “bang-for-buck”
ChallengesLittle-to-no outfall and source-area field dataLimited time and budgets
25 SRA’s completed in 2.5 years by SWCD’s withat least 5 more currently being worked on
Defining our task
The Plus Side>30 years of pollutant accumulation, behavior and washoff data available>20 years of BMP performance data with more recent, state-of-science research (bench and field)Midwest city data (loading)Several water quality models based on this researchIf outfall data exists, can be calibrated to improve accuracyCan easily be modified (build-scenarios)Repeatable (precise)Multiple-year to-do-list based on value (lbs/$/yr)
25 SRA’s completed in 2.5 years by SWCD’s withat least 5 more currently being worked on
Scope
3-Analysis of BMP’s by site
2-Ananlysis of SW’s Catchments
1-Selection of Subwatershed
Process Overview
Scoping and Remote Data collectionDesktop AnalysisField ReconnaissanceTreatment modeling and cost analysisReport
Process Overview
ScopingWater body needsLGU needsExisting data review (quality and needs)Budgets and timeframesStakeholder consensus
Desktop AnalysisField ReconnaissanceTreatment modeling and cost analysisReport
Process Overview
Scoping and Remote Data collectionDesktop Analysis
Catchment and/or pipeshed delineationDelineate and classify land usesDelineate and classify permeable surface soilsAnalyze existing WQ treatment / base load modelFirst-tier elimination of catchments for retrofittingFirst-tier determination of WQ potential treatments
Field ReconnaissanceTreatment modeling and cost analysisReport
Process Overview
Scoping and Remote Data collectionDesktop AnalysisField Reconnaissance
Visit existing BMPsConfirm/modify land-use and storm sewer dataConfirm/modify initial BMP-family selectionSelection of 1° and 2° BMP sites (parcels)Site-specific data collection
Treatment modeling and cost analysisReport
Process Overview
Scoping and Remote Data collectionDesktop AnalysisField ReconnaissanceTreatment modeling and cost analysis
Development and optimization of BMP designIterations of “train” and/or level of treatment by BMP quantity – load reduction estimatesEstimates of installation and life-cycle costsLife-Cycle Cost analysis
Report
Process Overview
Scoping and Remote Data collectionDesktop AnalysisField ReconnaissanceTreatment modeling and cost analysisReport
Summary table – catchments ranked based on performance ($/lb/LCyr)Catchment profilesAnalysis methods and dataReferences
SiteCatchmentSubwatershed
SW #1C1
S1
S2
S3
S4
S5
S…
C2
C3
C…
STORMWATER BMP LOCATION
ANALYSIS
Existing Stormwater
Ponds
Storage Above Roadway Culverts
Storage Below Outfalls
Within Conveyance
SystemStorage in ROW
Large Parking Lots
Public Land
Catchments
BMPS
Extended Detention
Wet Ponds
Wetlands
Bioretention
FiltrationInfiltration
Swales
Other
Existing Pond Modification
Sites
Pleasant Lake Stormwater Retrofit Assessment, 2011
Laek McKusick existing stormwater routing diagram, MSCWMO
Lily Lake Stormwater Retrofit Assessment, 2009, Middle St. Croix WMO
Pleasant Lake Stormwater Retrofit Assessment, 2011
Pleasant Lake Stormwater Retrofit Assessment, 2011
Pleasant Lake Stormwater Retrofit Assessment, 2011
Pleasant Lake Stormwater Retrofit Assessment, 2011
Howard Lake Stormwater Retrofit Assessment
34-Acre Medium Density Residential Area
Pollutant Amt/year
Water Runoff 963,715 ft3
TSS 12,900 lbs
TP 35 lbs
TKN 128 lbs
Copper 0.73 lbs
Lead 1.34 lbs
Zinc 5.80 lbs
First Tier possible BMP locations
Lindstrom Retrofit Assessment, 2009,
Chisago SWCD
Catchment-based Cost/Benefit Analysis
EXISTING CONDITIONS RETROFIT OPTIONS
Base Loading Treatment
Marginal Network Treatment By BMP
Level 1 Level 2 Level 3
Treatmen
t
Existing BMP performance (%TP) 54% New Net % New Net % New Net %TP (lb/yr) 25.2 13.7 1.0 58% 1.9 62%TSS (lb/yr) 7887 6698 261 88% 357 89%Volume (acre-feet/yr) 21.90 0.00 0.00 0% 2.40 11%
Square feet of practice (or, CU FT of storage for WP, ED, SW) Exc. 3 ft below
outlet 1500
Marginal Cost
s
BMP Type Wet Pond Extended Detention
Moderately Complex
BioretentionNot yet advised
Materials/Labor/Design $30,000 $51,000
Unit Promotion & Admin Costs* $250 $254
Total Project Cost** $30,250 $54,803Annual O&M $0 $1,125Term Cost/lb/yr (30 yr) $1,008 $1,554
Retrofit Scenario: exc 3 ft on P27add 6 RG in
19
Catchment or Pond ID
Retro Type Qty of 100 ft3 BMPs
TP Reduction
(%)
TP Reduction
(lb/yr)
Volume Reduction (ac-ft/yr)
Overall Est. Cost1
O&M Term
(years)
Total Est. Term Cost/lb-
TP/yr
LILY-03 B 12 10 5 4 $19,900 30 $313
LILY-04 B, PS, VS 8 10 3.3 2.9 $14,150 30 $313
LILY-01 B 11 10 4.4 3.6 $17,650 30 $315
LILY-02 B 11 10 4.5 3.7 $18,000 30 $315
LILY-12 B 18 10 3.2 2.5 $12,000 30 $316
LILY-07 B, VS 20 20 7 5.8 $24,000 30 $318
LILY-09 B 11 20 4.3 3.6 $18,450 30 $337
LILY-22 B 14 20 2.5 4.2 $22,320 30 $352
LILY-10 B, PS, F 7 10 2.9 2.4 $15,225 30 $353
LILY-21 B 12 20 2.2 3.6 $19,325 30 $353 2P13-W PM n/a 50 20 0 $130,000 15 $433 2P18-W PM n/a 50 30 0 $265,000 15 $589
Lily Lake Stormwater Retrofit Assessment, 2009, Middle St. Croix WMO
Report
http://www.metrocd.org/
Questions
Recommended