what’s in your baffle box? - florida stormwater€¦ · evaluation overview gross pollutant...

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

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)


with media filter (1) CDS unit (1)


with media filter (1) CDS unit (1) Inlet Baskets (3)


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


Pollutants enteringReceivingWaterbody: dissolved pollutants + uncapturedgross pollutants, sediment/ TSSInput Mass = Discharge Mass + Mass of Sump Solids

Conventional inflow concentration sampling not used


Calculated Measured Measured

Sump

ScreenCylinder

SeparationCylinder

Gross pollutants, sediment/ TSS

Method for 2nd Generation Baffle Box w/ Media Filter


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


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


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


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


19.37 3.8 11% 0.042 0.20 0.022

Lake Hodge


20.98 7.2 57% 4.09 0.343 0.195


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


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


19.37 742 63 467 38.3 24

Lake Hodge


20.98 1,629 80 1,303 77.6 62


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%


1,268 287 -77%


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


$140,915 $2,430 $16,776 $15.09


$197,968 $4,925 $2,420 $7.60


$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 [email protected] (407) 262 7725 ext 1235

what’s in your baffle box? - florida stormwater€¦ · evaluation overview gross pollutant...

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