what’s in your baffle box? - florida stormwater€¦ · evaluation overview gross pollutant...
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What’s In Your Baffle Box?
Evaluation of Baffle Boxes with Media Filters and Other
BMPsKelly H. Brock, Ph.D., P.E., CFM, LEED AP
City of Casselberry, FL
Florida Stormwater Association 2014 Winter Conference - December 11, 2014
Evaluation Overview Gross Pollutant Separators (GPS’s)
covered: 4 baffle boxes with varying features
(media filters, calcium peroxide) 1 CDS (continuous deflective
separation) unit 3 inlet baskets Multiple parameters Sampling mid 2013 to early 2014
Final report October 2014
Typical Stormwater Outfall Retrofit Opportunities
Existing Storm Pipe
Runoffsource
Receivingwaterbody
Typical Stormwater Outfall Retrofit Opportunities
Existing Storm Pipe
Runoffsource
Receivingwaterbody
Typical Stormwater Outfall Retrofit Opportunities
Runoffsource
Receivingwaterbody
Gross Pollutant Separator
inserted in line w/ existing storm pipe
GPS: 2nd Generation Baffle Box (1)
Runoffsource
Receivingwaterbody
Screen
Chambers
Skimmer
GPS: 2nd Generation Baffle Box with Media Filter (1)
Runoffsource
Receivingwaterbody
Screen
Chambers
Skimmer
Vertical Alumino silicate-based Media Filter
GPS: 2nd Generation Baffle Box with Media Filter & Calcium Peroxide (2)
Runoffsource
Receivingwaterbody
Screen
Chambers
Vertical Alumino silicate-based Media Filter
PVC tubes with Calcium Peroxide based additive
GPS: CDS Unit (1)
Runoffsource
Receivingwaterbody
Sump
ScreenCylinder
SeparationCylinder
GPS: Inlet basket (3)
Runoffsource
Receivingwaterbody
Existinginletstructure
MultipleSieve ScreenBasket
Hydrocarbon boom
Evaluation Locations
Evaluation Locations: Lake Concord 2nd gen baffle box
(1)
Evaluation Locations: Lake Concord 2nd gen baffle box
(1) Treatment Area:
5.6 ac
Evaluation Locations: San Pablo 2nd gen baffle box
with media filter (1)
Evaluation Locations: San Pablo 2nd gen baffle box
with media filter (1) CDS unit (1)
Evaluation Locations: San Pablo 2nd gen baffle box
with media filter (1) CDS unit (1) Inlet Baskets (3)
Evaluation Locations: San Pablo 2nd gen baffle box
with media filter (1) CDS unit (1) Inlet Baskets (3) Treatment Areas Baffle box: 19.4 ac CDS: 4.9 ac Baskets: 4.7 ac
Evaluation Locations: Lake Hodge/Gee Creek
2nd gen baffle boxes w/ media filter & calcium peroxide (2)
Evaluation Locations: Lake Hodge/Gee Creek
2nd gen baffle boxes w/ media filter & calcium peroxide (2)
Treatment Area: Lk Hodge 21 ac Gee Crk 30 ac
Evaluation Protocol Quality Assurance Project Plan
(QAPP) approved by FDEP Rainfall Volumetric inflow/outflow Stormwater autosampling Grab samples Solids/sediment sampling Multiple Parameters
Focus: TP, TN, TSS, Fecal Coliform
Method for 2nd Generation Baffle Box
RunoffPollutant constituents: leaves, litter, debris, sediment/TSS, dissolved pollutants
Pollutants enteringReceivingWaterbody: dissolved pollutants + uncapturedgross pollutants, sediment/ TSS
Screen
Chambers
Skimmer
Leaves, litter, debris
Sediment
Input Mass = Discharge Mass + Mass of Sump/Screen Solids
Conventional inflow concentration sampling not used
Outflow concentration sampling used
Calculated Measured Measured
Method for CDS unit
RunoffPollutant constituents: leaves, litter, debris, sediment/TSS, dissolved pollutants
Pollutants enteringReceivingWaterbody: dissolved pollutants + uncapturedgross pollutants, sediment/ TSSInput Mass = Discharge Mass + Mass of Sump Solids
Conventional inflow concentration sampling not used
Outflow concentration sampling used
Calculated Measured Measured
Sump
ScreenCylinder
SeparationCylinder
Gross pollutants, sediment/ TSS
Method for 2nd Generation Baffle Box w/ Media Filter
RunoffPollutant constituents: leaves, litter, debris, sediment/TSS, dissolved pollutants
Pollutants enteringReceivingWaterbody: uncapturedgross pollutants, sediment/ TSS, dissolved pollutants
Screen
Chambers
Leaves, litter, debris
Sediment
Input Mass = Discharge Mass + Mass of Sump/Screen Solids + Mass Retained in Filter
Conventional inflow concentration sampling used
Outflow concentration sampling used
Partially Measured Measured Measured
Vertical Media Filter
Calculated
Method for Inlet Baskets
Existinginletstructure
MultipleSieve ScreenBasket
Hydrocarbon boomRunoffPollutant constituents: leaves, litter, debris, sediment/TSS, dissolved pollutants
Pollutants enteringReceivingWaterbody: dissolved pollutants + uncapturedgross pollutants, sediment/ TSS
leaves, litter, debris, sediment
Basket contents sampled
No flow sampling
Summary of Results Summary of Measured Removal Efficiencies
Location Type TN TP TSSLake Concord 2nd gen 1.6% 2.6% 66%
San Pablo 2nd gen w/ filter 14% 11% 63%
Lake Hodge 2nd gen w/ filter and additive
14% 57% 80%
Gee Creek 2nd gen w/ filter and additive
2% 41% 78%
San Pablo CDS 4.2% 9.3% 92%
Summary of Results Annualized Load Removal Estimates - TN
Location TypeTreatment Area (ac)
TN Load (kg/yr)
TN Removal
Efficiency (%)
TN Removal (kg/yr)
TN Load/ area
(kg/ac-yr)
TN Removal/
area (kg/ac-yr)
Lake Concord
2nd gen 5.64 10.9 1.6% 0.17 1.93 0.030
San Pablo 2nd gen w/filter
19.37 20.6 14% 2.9 1.06 0.15
Lake Hodge
2nd gen w/ filter and additive
20.98 14.4 14% 2.01 0.686 0.0958
Gee Creek 2nd gen w/ filter and additive
29.98 11.7 2% 0.21 0.390 0.0070
San Pablo CDS 4.90 4.8 4.2% 0.20 0.98 0.041
Subtotal 80.87 62.4 7.2% avg 5.5 1.01 avg 0.065 avg
San Pablo Baskets 4.71 -- -- 0.037 -- 0.0079
Summary of Results Annualized Load Removal Estimates - TP
Location TypeTreatment Area (ac)
TP Load (kg/yr)
TP Removal
Efficiency (%)
TP Removal (kg/yr)
TP Load/ area
(kg/ac-yr)
TP Removal/
area (kg/ac-yr)
Lake Concord
2nd gen 5.64 1.3 2.6% 0.03 0.23 0.005
San Pablo 2nd gen w/filter
19.37 3.8 11% 0.042 0.20 0.022
Lake Hodge
2nd gen w/ filter and additive
20.98 7.2 57% 4.09 0.343 0.195
Gee Creek 2nd gen w/ filter and additive
29.98 1.7 41% 0.71 0.057 0.024
San Pablo CDS 4.90 0.5 9.3% 0.05 0.10 0.01
Subtotal 80.87 14.5 24% avg 5.3 0.19 avg 0.05 avg
San Pablo Baskets (3) 4.71 -- -- 0.012 -- 0.0025
Summary of Results Annualized Load Removal Estimates - TSS
Location TypeTreatment Area (ac)
TSS Load (kg/yr)
TSS Removal
Efficiency (%)
TSS Removal (kg/yr)
TSS Load/ area
(kg/ac-yr)
TSS Removal/
area (kg/ac-yr)
Lake Concord
2nd gen 5.64 180 66 119 31.9 21
San Pablo 2nd gen w/filter
19.37 742 63 467 38.3 24
Lake Hodge
2nd gen w/ filter and additive
20.98 1,629 80 1,303 77.6 62
Gee Creek 2nd gen w/ filter and additive
29.98 652 78 509 21.7 17
San Pablo CDS 4.90 36 92 33 7.3 6.7
Subtotal 80.87 3,239 76 avg 2,431 35.4 avg 26 avg
San Pablo Baskets 4.71 -- -- 42.4 -- 9.00
Summary of Results Fecal Coliform – Geometric Mean
Location TypeInflow FC
(cfu/100mL)Outflow FC(cfu/100mL)
Percent Change (%)
Lake Concord 2nd gen -- 529 --
San Pablo 2nd gen w/ filter 5,581 3,883 -30%
Lake Hodge 2nd gen w/ filter and additive
1,268 287 -77%
Gee Creek 2nd gen w/ filter and additive
314 82 -74%
San Pablo CDS -- 161 --
Lifecycle Cost/Benefit Analysis Funded by Casselberry Stormwater Utility &
FDEP TMDL Water Quality Restoration Grant Assumptions: Lifecycle: 20 years Interest: 4%
Calculated on present worth basis using total load removed and total cost over 20 years
Efficiency evaluation cost NOT included in lifecycle cost/benefit analysis
Lifecycle Cost/Benefit Analysis Implementation costs included estimates for: Permitting Design Construction Construction inspection Staff time Supplies
Lifecycle Cost/Benefit Analysis Annual O&M costs included: Cleanout (2X/yr for all) Hydrocarbon boom replacement (2X/yr for
2nd gen box and inlet baskets) Media filter replacement (1X/yr for each 2nd
gen box with media filters) Calcium peroxide additive replacement (4X/yr
for each 2nd gen box with additive)
Lifecycle Cost/Benefit AnalysisLocation Type
20 year present worth ($)
TN Removal cost ($/kg)
TP Removal cost ($/kg)
TSS Removal cost ($/kg)
Lake Concord 2nd gen $70,510 $20,738 $117,517 $29.63
San Pablo 2nd gen w/filter
$140,915 $2,430 $16,776 $15.09
Lake Hodge 2nd gen w/ filter and additive
$197,968 $4,925 $2,420 $7.60
Gee Creek 2nd gen w/ filter and additive
$197,968 $47,135 $13,941 $19.45
San Pablo CDS $91,751 $22,938 $91,751 $139
San Pablo Baskets (3) $6,952 $9,365 $28,967 $8.20
AVERAGE $17,922 $45,229 $36
Caveats for Comparisons and Broader Applicability
Limitations of evaluation methods Differences between treatment devices
Statistical significance Differences in sub-basin characteristics/loads Seasonal variability in load characteristics Cost differences (market conditions, site
constraints, scale, etc.)
Lessons Learned…
Existing Conditions Can Cause Difficulties
Baffle Boxes can be BIG…
…and Heavy!
Stormwater Can Be Messy & Gross!
Fecal Coliform: TNTC
Maintenance Matters Most
Grants may be free, but they aren’t always easy
Focus on low hanging fruit… lifecyle cost is key
Best performing GPS unit for TP cost/benefit: $2,420/kg TP removed
Compared to: Casselberry whole lake alum treatments:
$127/kg TP Casselberry Streetsweeping: $252/kg TP Conventional capital BMPs: highly variable
and site specific
Questions?
More Information
Full report available at: www.casselberry.org/lakes
Kelly Brock, Ph.D., P.E., Assistant Public Works Director/City Engineer kbrock@casselberry.org (407) 262 7725 ext 1235
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