major retrofits – reducing pollutant loading to comfort lake using iron filings d avid f ilipiak...
TRANSCRIPT
MAJOR RETROFITS – REDUCING POLLUTANT LOADING TO
COMFORT LAKE USING IRON FILINGS
DAVID FILIPIAK & JEREMY NIELSEN, SRF
PRESENTATION OUTLINE
• PROJECT OVERVIEW
• DESIGN GOALS/CONSIDERATIONS
• CONSTRUCTION/TECHNIQUES
• MONITORING RESULTS
• CONCLUSIONS/LESSONS LEARNED
PROJECT OVERVIEW
PROJECT OVERVIEWSITE PARAMETERS
64.9 ACRES OF EXISTING COMMERCIAL/RESIDENTIAL DRAINAGE AREA (60% IMPERVIOUS SURFACE)
36.5 ACRES OF PROJECT AREA (50% IMPERVIOUS SURFACE)
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
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%
DESIGN
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
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%
CONSTRUCTION/TECHNIQUES
CHALLENGING SUBGRADE SOILS
CONSTRUCTION/TECHNIQUES
BURIED CONSTRUCTION DEBRIS
CONSTRUCTION/TECHNIQUES
FINE FILTER AGGREGATE
CONSTRUCTION/TECHNIQUESMIXING OF IRON ENHANCED SAND
CONSTRUCTION/TECHNIQUESMIXING OF IRON ENHANCED SAND
CONSTRUCTION/TECHNIQUES
PLACEMENT OF TILE/FILTER AGGREGATE
CONSTRUCTION/TECHNIQUES
PLACEMENT OF IRON ENHANCED SAND
FINAL PRODUCT – 1 YEAR LATER
PRETREATMENT BASINFILTRATION BASIN
MONITORING/RESULTS
MONITORING LOCATIONS• INLET
• CONNECTION BETWEEN THE POND/FILTRATION BASIN
• TILE OUTFALL
• FIRST YEAR OF A 3 YEAR PROGRAM
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
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
PROJECT PARTNERS
