Major retrofits – reducing pollutant loading to Comfort Lake using iron filings
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Transcript of Major retrofits – reducing pollutant loading to Comfort Lake using iron filings
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MAJOR RETROFITS – REDUCING POLLUTANT LOADING TO
COMFORT LAKE USING IRON FILINGS
DAVID FILIPIAK & JEREMY NIELSEN, SRF
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PRESENTATION OUTLINE
• PROJECT OVERVIEW
• DESIGN GOALS/CONSIDERATIONS
• CONSTRUCTION/TECHNIQUES
• MONITORING RESULTS
• CONCLUSIONS/LESSONS LEARNED
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PROJECT OVERVIEW
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PROJECT OVERVIEWSITE PARAMETERS
64.9 ACRES OF EXISTING COMMERCIAL/RESIDENTIAL DRAINAGE AREA (60% IMPERVIOUS SURFACE)
36.5 ACRES OF PROJECT AREA (50% IMPERVIOUS SURFACE)
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DESIGN GOALS/CONSIDERATIONS
DESIGN GOALS/CONSTRAINTS
GOALSo MATCH PRE-DEVELOPMENT DISCHARGE RATESo NO NET INCREASE IN RUNOFF VOLUME (FROM PRE-DEVELOPMENT
CONDITIONS) FOR A 2-YEAR 24-HOUR STORMo NO NET INCREASE IN TOTAL PHOSPHOROUS LOADING
CONSTRAINTSo HIGH GROUND WATERo SHALLOW STORM SEWERo FLAT TOPOGRAPHY
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IRON FILING SAND ENHANCEMENT
ENHANCED DESIGN
ADDED IRON FILINGS SAND INTO THE FILTRATION BASIN DESIGN BIOENGINEERED SOIL PRIMARY FILTER MECHANISM/IRON FILING
SAND SECONDARY FILTER MECHANISM INCREASE THE DEPTH OF WATER THAT WILL PERMEATE THROUGH THE
FILTER MATERIAL BY 50%
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DESIGN
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DESIGN GOALS/CONSIDERATIONS
ENHANCED DESIGN CONSIDERATIONS
o STANDING WATER IN UPSTREAM PIPES – ADDED MECHANICAL VALVE TO DRAIN DOWN POND IN FALL
o VEGETATED BASIN DRAWN DOWN – MODIFIED SOIL TO HIGHER SAND CONTENT TO ASSIST DRAINAGE GIVEN ADDED WATER
o IRON FILING CONTENT – USED MECHANICAL MIXING FOR CONSISTENT MIX
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DESIGN GOALS/EXPECTATIONS
EXPECTED PERFORMANCE
DescriptionTotal Drainage Area/ Project
Area ac
% Total Impervious/
(Project Impervious)
TP Loadinglbs/yr
TP Removedlbs/yr TP Reduction, %
Existing Conditions 64.9 (36.5) 53.7% (40%) 54 5.2 9.6%
Proposed Conditions 64.9 (36.5) 59.8% (50%) 59.6 41.5 69.6%
Enhanced Conditions 64.9 (36.5) 59.8% (50%) 59.6 46.7 78.4%
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CONSTRUCTION/TECHNIQUES
CHALLENGING SUBGRADE SOILS
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CONSTRUCTION/TECHNIQUES
BURIED CONSTRUCTION DEBRIS
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CONSTRUCTION/TECHNIQUES
FINE FILTER AGGREGATE
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CONSTRUCTION/TECHNIQUESMIXING OF IRON ENHANCED SAND
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CONSTRUCTION/TECHNIQUESMIXING OF IRON ENHANCED SAND
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CONSTRUCTION/TECHNIQUES
PLACEMENT OF TILE/FILTER AGGREGATE
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CONSTRUCTION/TECHNIQUES
PLACEMENT OF IRON ENHANCED SAND
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FINAL PRODUCT – 1 YEAR LATER
PRETREATMENT BASINFILTRATION BASIN
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MONITORING/RESULTS
MONITORING LOCATIONS• INLET
• CONNECTION BETWEEN THE POND/FILTRATION BASIN
• TILE OUTFALL
• FIRST YEAR OF A 3 YEAR PROGRAM
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MONITORING/RESULTS
FIRST YEAR RESULTS • INCREASE ON CONCENTRATIONS AND LOADS OF TP, SRP AND TSS FROM THE
INLET OF THE IRON-ENHANCED INFILTRATION BASIN TO ITS OUTLET
• THE POND OPERATES WITHIN EXPECTED REMOVAL RATES
• SOME ORANGE WATER HAS BEEN DETECTED PERIODICALLY AT THE OUTLET, INDICATING POTENTIAL FERRIC HYDROXIDE COMING OUT FROM THE IRON FILLINGS
• INCREASES IN LOADING DECREASED WITH SIMILAR STORM EVENTS OVER THE COURSE OF THE YEAR
• ANY FINAL CONCLUSIONS ABOUT THE EFFECTIVENESS OF THE FILTRATION BASIN BASED ON THE FIRST YEAR MONITORING IS PREMATURE SINCE THESE SYSTEMS TYPICALLY REQUIRE AT LEAST A YEAR TO STABILIZE (VEGETATION/SOILS SETTLING) AND REACH STEADY STATE OPERATION
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CONCLUSIONS/LESSONS LEARNED
• IRON SYSTEMS NEED TO DRY OUT – CHALLENGING IN WET CONDITIONS OR IN POOR SOILS
• TAILWATER CONDITIONS FOR OUTLET COULD IMPACT PERFORMANCE
• DRYING OUT IRON MAY IMPACT VEGETATION OVER THE TILE SYSTEM (MAY IMPACT LONG-TERM VIABILITY OF VEGETATION)
• IT TAKES TIME TO SEE RESULTS WITH VEGETATED FACILITIES
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PROJECT PARTNERS