Stormwater BMP Effectiveness and the BMPTRAINS Model

Pinellas County Stormwater Management Manual Training

Workshop

BASIC PRINCIPLES FOR LOADING AND REMOVAL

• Loading depends on runoff and land use characteristics• Runoff depends on rainfall and land use characteristics• Removal depends on runoff loading and performance of BMPs • Thus must have reasonable estimates for

• Rainfall• Runoff• Concentrations of pollutants in the runoff• Performance of BMPs and LIDs as individual units and in combination with others• Cost of the BMPs and LIDs.

RAINFALL CHARACTERISTICSPINELLAS COUNTY HISTORICAL DATA

• A predictor of the future is the past

• Rainfall data are based on an evaluation conducted by Harper and Baker (2007) for FDEP which is summarized in the document titled “Evaluation of Current Stormwater Design Criteria within the State of Florida” A extension of the original work done by FDEP in the 1970s.

• Study included an evaluation of rainfall characteristics throughout the State, including• Rainfall depths• Rainfall variability• Inter-event dry periods

METEOROLOGICAL MONITORING SITES

- DATA OBTAINED FOR 1971-2000

- 160 SITES TOTAL- 111 SITES IN FLORIDA

- 49 SITES IN PERIMETER AREAS

- OVERALL ANNUAL MEAN DEVELOPED FOR EACH

SITE

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Available Meteorological Data

- Rainfall isopleths were developed for 1971 – 2000 based

on the annual mean values

- Florida rainfall is highly variable ranging from ~ 38 – 66 in/yr,

depending on location

- Average Annual updated using up to 2014 is about 51inches and is used as rainfall in BMPTRAINS*

Average Annual Florida Precipitation 1971 – 2000

*Not available in any other models:Available from www.stormwater.ucf.edu free of charge

ESCAMBIA COUNTY AVERAGE ANNUAL RAINFALL

- Expanded view plots are available in BMPTRAINS

for the entire State

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SIMILAR METEOROLOGICAL ZONES

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APALACHICOLA

AVON PARK

BOCA RATON

BRANFORD

BROOKSVILLE

CLEWISTON

CRESTVIEW

CROSS CITY

DAYTONA BEACHDELAND

DOWLING PARK

FORT MYERS

GAINESVILLE

GRACEVILLE

HOMESTEAD EXP STN

INGLIS

JACKSONVILLE

KEY WEST

KISSIMMEE

LAKELAND

LAMONT

LEESBURG

LIGNUMVITAE KEY

LYNNE

MARINELAND

MELBOURNE

MIAMI

MOORE HAVEN LOCK 1

NICEVILLE

ORLANDO

PANACEA

PANAMA CITY

PARRISH

PENSACOLA

RAIFORD

ST LEO

ST LUCIE NEW LOCK 1

ST PETERSBURG

TALLAHASSEE

TAMIAMI TRAIL 40 MI

TAMPA

VENUS

VERNON

W PALM BEACH

WOODRUFF DAM

50 0 50 100 Miles

N

EW

S

Clusters1

2

3

4

5

- Cluster analysis used to identify areas with similar

annual rainfall/runoff relationships (C values on an average annual basis)

- Analysis identified 5 significantly different

areas

-

ZONE 4

RUNOFF GENERATION

• Runoff generation is a function of:• Precipitation

• Volume and Intensity• Inter-event dry periods

• Soil types• Land cover

• Understanding all relationships is essential to quantifying runoff

Annual Runoff coefficients (C values) function of rain and ground conditions

• Runoff coefficients reflect the proportion of rainfall that becomes runoff under specified conditions and on annual basis.

• CN are used to reflect the runoff conditions.• Annual simulations using 45 sites in Florida.

.

Annual Runoff Coefficients (depth of runoff from rainfall in a period of time)

DIRECTLY CONNECTED IMPERVIOUS AREAS (DCIA)

Annual runoff estimation is the sum of events using separate DCIA and remaining area runoff. Example: Residential area with A type soils, 1/3 acre lots , 30% DCIA, fair grass cover:

DCIA = 30%CN pervious = 49CCN = 64

* Reference: CN method, see Hydrology, Wanielista, et.al, 1997, page 155

DCIA = 30%CN pervious = 49Do not useCCN

R does notExceed 0 until P > 1.12 inches*

At P = 1.12 inchesR= 0.3 x 1.12 = 0.34 inch And of course RunoffFor all rainfalls less than1.12 based on the DCIA*

DIRECTLY CONNECTED IMPERVIOUS AREAS (DCIA)• DCIA includes all impervious areas from which runoff discharges directly into

the drainage system during small events.• Does not include swales as DCIA or any other BMP from which a significant

(generally >4 inches) water volume is abstracted. • Disconnected if the storage (surface and ground) provides capture of

almost all rainfall events; as examples:• Intentional depression storage between parking areas ½ foot water

depth and 2 feet of select media at a water storage capacity of 0.25 = 12 inches calculation is (0.5’+2’x 0.25)x12

• Separation of at least 10 feet for overland flow in Type A soils and slope<5%

• Pervious pavements with sufficient reservoir storage to exceed 4 inches.• Separation of at least 20 feet for overland flow in other than Type A soils.

• NOTE: BMPTRAINS will adjust runoff volumes when BMPs are used. • AND WHY 4 inches? 4 inches retention results in captures > 99% volume.

Comparison of State-Wide Annual C Values forA Hypothetical Residential Development

DCIA = 40%Non-DCIA CN = 70

O.396

O.358

O.365

O.372

O.379

SUMMARY RUNOFF CONDITIONS

• Like rainfall, runoff in Florida is highly variable, depends on• Impervious area

• Direct relationship between runoff and impervious percentage• Non-DCIA CN value (soils and cover crop)

• Exponential relationship between CN value and runoff• Characteristics of rain events

• BMPTRAINS Model is the only one that calculates annual C value and runoff volume based on site and rainfall characteristics characteristics of the project site.

HOW DO WE CALCULATED THE LOADINGS

• Runoff concentrations are commonly expressed in terms of an event mean concentration (EMC):

• An annual EMC value is generally determined by evaluating event values over a range of rainfall depths and seasons• Generally estimated based on field monitoring• Usually requires a minimum of 7-10 events collected over a range of conditions

• Annual mass loadings are calculated by:

EMC = pollutant loading

runoff volume______________

Annual mass loading = annual runoff volume x EMC

HISTORY OF FLORIDA EMC DATABASE• The original database was developed by ERD in 1990 in support of the Tampa Bay

SWIM Plan• A literature review was conducted to identify runoff emc values for single land use

categories in Florida• Approximately 100 field studies were identified

• Each study was evaluated for adequacy of the data, length of study, number of monitored events, completeness, and monitoring protocol

• Selection criteria• Monitoring site included a single land use category – most difficult criterion• At least 1 year of data collection; minimum of 5 events monitored in a flow-weighted fashion• Wide range of rainfall depths and antecedent dry periods included in monitored events• Seasonal variability included in monitored samples

• 59 studies were selected for inclusion in the data base for post development• Values were summarized by land use category and includes runoff from all sources, ie

roof tops included in commercial and residential areas.• First known compilation of EMC data for Florida• EMC values calculated as simple arithmetic means

FLORIDA DEVELOPED LAND STUDIES IN EMC DATA BASE

LAND USE NUMBER OF FIELD SITES

Single Family Residential 17

Multi-Family Residential 6Low Intensity Commercial 9High Intensity Commercial 4Industrial 4Highway 15Parks/open space 4

• Runoff EMC values are available for a wide range of land use categories in Florida• Urban land uses• Natural land uses

• Estimation of annual runoff loadings requires• Estimation of annual runoff volume• Runoff EMC value which reflects ground cover runoff characteristics

• Any calculations should be based on user input data for• Location• Annual rainfall• Project physical land and soil characteristics• Pre/post Land use and cover

SUMMARY OF EMC AND LOADINGS

B Y : C L AR K H U L L , E R I C L I V I N G S T O N AN D M AR T Y W AN I E L I S T A

QUESTIONS, REMARKS AND DISCUSSION

2017Pinellas County

Pinellas County Stormwater Management Manual Training

Workshop

HOW DO WE ASSIGN EFFECTIVENESS TO THE LID BMPS IN THE COUNTY STORMWATER MANUAL?

Many reduce the volume of runoff, thus reduce TMDL1. Reduce impervious areas: These reduce the area from which there is discharge

and thus reduce the stormwater volume and the amount of mass discharged.2. Pervious pavements: Storage in reservoir resulting in a reduction in the volume

of discharge which reduces the pollutant loading.3. Bioretention areas: promotes infiltration resulting in a reduction in volume

discharge and pollutant loadings.4. Swales: transport and infiltrate stormwater, thus a reduction in volume of

discharge and pollutant loadings.5. Vegetated greenroofs, promotes evapotranspiration and thus a reduction in the

volume of discharge and pollutant loadings.

THREE LID RETENTION OPTIONS PERVIOUS PAVEMENTS, SWALES, AND RAIN GARDENS

All three together

Note: greenroofs also retain about 0.1 inch of water per inch of media depth

Street and Parking Lot Depression Areas or Rain Gardens

• An evaluation of the efficiency of retention practices was conducted by Harper and Baker (2007) for FDEP which is summarized in the document titled “Evaluation of Current Stormwater Design Criteria within the State of Florida”

• Based on a continuous simulation of runoff

RETENTION EFFICIENCYWITH APPLICATION TO PERVIOUS PAVEMENTS AND BIO-RETENTION

Bioretention area in pervious parking lotat Central Office Complex

Modeled Dry Retention Removal Efficiencies

Source: Harper and Baker (2007) - Appendix D

Tables were generated of retention efficiency for each meteorological zone in 0.25 inch intervals from 0.25 - 4.0 inches - 16 separate tables per zone

NDCIA 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0 65.0 70.0 75.0 80.0 85.0 90.0 95.0 100.0

30.0 94.00 94.20 92.10 88.80 84.80 80.50 76.30 72.40 68.60 65.20 62.00 59.10 56.40 53.90 51.70 49.50 47.60 45.80 44.10 42.6035.0 91.10 92.30 90.70 87.70 84.00 79.90 75.90 72.00 68.40 65.00 61.90 59.00 56.30 53.90 51.60 49.50 47.60 45.80 44.10 42.6040.0 87.80 90.00 88.90 86.40 82.90 79.10 75.30 71.50 68.00 64.70 61.60 58.80 56.20 53.80 51.50 49.40 47.50 45.70 44.10 42.6045.0 84.00 87.20 86.80 84.70 81.60 78.10 74.50 70.90 67.50 64.30 61.30 58.60 56.00 53.60 51.40 49.40 47.50 45.70 44.10 42.6050.0 79.90 84.00 84.30 82.70 80.10 76.90 73.50 70.20 66.90 63.90 61.00 58.30 55.80 53.50 51.30 49.30 47.40 45.70 44.10 42.6055.0 75.60 80.40 81.40 80.40 78.20 75.40 72.30 69.20 66.20 63.30 60.50 57.90 55.50 53.20 51.10 49.20 47.30 45.60 44.00 42.6060.0 71.30 76.50 78.10 77.60 75.90 73.60 70.90 68.00 65.20 62.50 59.90 57.40 55.10 53.00 50.90 49.00 47.20 45.60 44.00 42.6065.0 67.10 72.40 74.40 74.50 73.30 71.40 69.10 66.60 64.10 61.60 59.20 56.90 54.70 52.60 50.60 48.80 47.10 45.50 44.00 42.6070.0 63.00 68.10 70.30 70.80 70.20 68.90 67.00 64.90 62.70 60.50 58.30 56.10 54.10 52.10 50.30 48.60 46.90 45.40 43.90 42.6075.0 59.20 63.70 65.90 66.70 66.60 65.70 64.40 62.70 60.90 59.00 57.10 55.20 53.30 51.50 49.80 48.20 46.70 45.20 43.80 42.6080.0 55.80 59.40 61.40 62.30 62.40 61.90 61.10 59.90 58.60 57.10 55.50 53.90 52.30 50.70 49.20 47.80 46.40 45.00 43.80 42.6085.0 52.70 55.20 56.70 57.50 57.70 57.60 57.10 56.40 55.50 54.50 53.30 52.10 50.80 49.60 48.30 47.10 45.90 44.70 43.60 42.6090.0 49.70 51.10 52.00 52.50 52.80 52.80 52.60 52.20 51.70 51.10 50.30 49.60 48.70 47.90 47.00 46.10 45.20 44.30 43.40 42.6095.0 46.70 47.10 47.40 47.50 47.60 47.60 47.50 47.30 47.10 46.80 46.50 46.20 45.80 45.40 44.90 44.50 44.00 43.50 43.00 42.6098.0 44.90 44.90 44.80 44.80 44.70 44.70 44.60 44.50 44.30 44.20 44.10 44.00 43.80 43.60 43.50 43.30 43.10 42.90 42.70 42.60

NDCIA 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0 65.0 70.0 75.0 80.0 85.0 90.0 95.0 100.0

30.0 95.60 96.40 95.60 94.10 92.10 89.60 86.80 83.90 81.00 78.10 75.30 72.70 70.10 67.70 65.40 63.30 61.20 59.30 57.40 55.7035.0 93.50 94.90 94.50 93.20 91.30 89.00 86.30 83.50 80.70 77.90 75.10 72.50 70.00 67.60 65.40 63.20 61.20 59.30 57.40 55.7040.0 91.00 93.10 93.00 92.00 90.30 88.10 85.70 83.00 80.20 77.50 74.90 72.30 69.80 67.50 65.30 63.10 61.10 59.20 57.40 55.7045.0 88.10 90.90 91.30 90.50 89.10 87.10 84.80 82.30 79.70 77.10 74.50 72.00 69.60 67.30 65.10 63.00 61.10 59.20 57.40 55.7050.0 85.00 88.40 89.20 88.80 87.60 85.90 83.80 81.50 79.00 76.50 74.10 71.70 69.30 67.10 65.00 62.90 61.00 59.10 57.40 55.7055.0 81.70 85.70 86.80 86.80 85.90 84.50 82.60 80.50 78.20 75.90 73.50 71.20 69.00 66.80 64.80 62.80 60.90 59.10 57.40 55.7060.0 78.40 82.60 84.10 84.40 83.90 82.70 81.10 79.20 77.20 75.00 72.80 70.70 68.60 66.50 64.50 62.60 60.80 59.00 57.30 55.7065.0 75.00 79.30 81.10 81.70 81.50 80.70 79.40 77.80 76.00 74.00 72.00 70.00 68.00 66.10 64.20 62.30 60.60 58.90 57.30 55.7070.0 71.70 75.90 77.90 78.70 78.70 78.20 77.30 76.00 74.40 72.70 71.00 69.10 67.30 65.50 63.80 62.00 60.40 58.80 57.20 55.7075.0 68.70 72.50 74.40 75.40 75.60 75.30 74.70 73.70 72.50 71.10 69.60 68.00 66.40 64.80 63.20 61.60 60.10 58.60 57.10 55.7080.0 65.90 69.00 70.80 71.70 72.10 72.10 71.70 71.00 70.10 69.00 67.80 66.60 65.20 63.90 62.50 61.10 59.70 58.30 57.00 55.7085.0 63.50 65.70 67.10 67.90 68.30 68.30 68.10 67.70 67.10 66.40 65.50 64.60 63.60 62.50 61.40 60.30 59.10 58.00 56.80 55.7090.0 61.20 62.40 63.20 63.80 64.10 64.20 64.10 63.90 63.60 63.20 62.70 62.10 61.40 60.70 59.90 59.10 58.30 57.40 56.60 55.7095.0 58.70 59.10 59.40 59.60 59.70 59.70 59.70 59.70 59.50 59.40 59.10 58.90 58.60 58.20 57.90 57.50 57.10 56.60 56.20 55.7098.0 57.50 57.50 57.50 57.50 57.50 57.40 57.40 57.30 57.20 57.10 57.00 56.90 56.80 56.60 56.50 56.40 56.20 56.00 55.90 55.70

Percent DCIA

Percent DCIA

Mean Annual Mass Removal Efficiencies for 0.75-inches of Retention for Zone 4

Mean Annual Mass Removal Efficiencies for 0.50-inches of Retention for Zone 4

Retention Depth Required for 80% RemovalState-wide Average

RETENTION EFFECTIVENESS FUNCTION OF DEPTH: EXAMPLE 1.5 INCHES CAPTURE

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0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00

Trea

tmen

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Retention depth (inch):

Efficiency Curve: System Efficiency (N $ P) CAT 1:System Efficiency (N $ P) CAT 2: System Efficiency (N $ P) CAT 3:System Efficiency (N $ P) CAT 4:

Going from a residentialArea to a multifamily areawith net improvement andsandy soils, need 68% TN and 77% TP removal.

Result using BMPTRAINS80% removal for 1.5 inchDepth of treatment.

EXAMPLE OUTPUT GREENROOF DESIGN(USING BMPTRAINS SCREEN CAPTURE)

2 inches of cistern storagePinellas County location With 51 inches of rain /year

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95

0.50 1.50 2.50 3.50 4.50Re

tent

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effic

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):

Retention depth (inch):

Efficiency Curve (N $ P) Sys Eff (N $ P) CAT 1 Sys Eff (N $ P) CAT 2

Sys Eff (N $ P) CAT 3 Sys Eff (N $ P) CAT 4

SAVE THE SWALES

GRAPH TO AID IN SPACING80% Capture

5% slope

Downstream Upstream

PROGRAMMING OF EQUATIONS( AN EXAMPLE)

EXAMPLE OUTPUT SWALE DESIGN(SCREEN CAPTURE FROM BMPTRAINS)

REMOVE MORE TN & TP FROM SURFACE DISCHARGES

• Add Biosorption Activated Media (BAM)to the discharge of an LID, such as from rain gardens (depression areas), in swale blocks, and the discharge from wet detention ponds.

• Already being used in greenroofs, which specify the use pollution control media.

AVAILABLE BAM ANDCAN ALSO USE OTHERS AS APPROVED

DESCRIPTION OF MEDIA

Media and Typical Location in BMP Treatment Train MATERIAL TSS REMOVAL EFFICIENCY

TN REMOVAL EFFICIENCY

TP REMOVAL** EFFICIENCY

B&G ECT (ref A) Expanded Clay2

A first BMP, ex. Up-Flow Filter in Baff le box and Tire Chips1

a constructed w etland# (USER DEFINED BMP) 70% 55% 65% 96 in/hrB&G OTE (ref A,B) Organics8

Up-flow Filter at Wet Pond or Dry Basin Outflow Tire Chips1

(FILTRATION) Expanded Clay4 60% 45% 45% 96 in/hrB&G ECT3 (ref C) Expanded Clay4

After Wet Detention using Up-flow Filter Tire Chip1 60% 45% 45% 96 in/hr

SAT (ref D) Sand3

A first BMP, as a Dow n-flow Filter (FILTRATION) 85% 30% 45% 2 in/hrB&G CTS (ref E,F) Clay6

Dow n-Flow Filters 12" depth*** at w et pond or dry basin Tire Crumb5

pervious pave, tree w ell, rain garden, sw ale, and strips Sand7 & Topsoil9 90% 60% 90% 1.0 in/hrB&G CTS (ref E,F) Clay6

Dow n-Flow Filters 24" depth*** at w et pond or dry basin Tire Crumb5

pervious pave, tree w ell, rain garden, sw ale, and strips Sand7 & Topsoil9 95% 75% 95% 1.0 in/hr

PROJECTED TREATMENT PERFORMANCE * TYPICAL OPERATING

LIMITING FILTRATION RATE

(in/hr)

COMPUTATIONAL AIDS

• FDEP Harper Report (FDEP, 2007) addressing Florida conditions and average annual conditions, and is site specific, uses look up tables, does not address series and parallel configurations

• Computer Programs• SMADA, stormwater management and design aids.• SWMM , primarily hydraulic and peak flow oriented with additions for pollution control.• State Manuals, like from Virginia, New Hampshire, D.C., Colorado, Texas, etc. • Municipal Manuals, like from Orange, Duval and Pinellas Counties, Nashville, etc.• Proprietary usually regional and for one or a few BMPs separately.• None address BMP placement in series or parallel.• None or very limited calculations for TMDL, some event based.• BMPTRAINS, application of FDEP Harper Report of 2007 with evaluation and

performance data for new BMPs since 2017

RETENTION EFFICIENCY CALCULATIONS• Calculation of runoff in the BMPTRAINS model uses the tabular retention

efficiency relationships developed by Harper and Baker (2007) – App. D

NOTE: There are 80 of these tables.

MODELS THAT CONSIDER LID BMPsHOWEVER AVERAGE ANNUAL REMOVAL (TMDL) NOT ADDRESSED

Stormwater Model / BMPs

Ret

entio

n B

iore

tent

ion

Dry

Dete

ntio

n

Swal

e

Gre

en R

oof

Filte

r Str

ip &

B

uffe

rPe

rmea

ble

Pave

men

t

Sand

Filt

er

Wat

er

Har

vest

ing

Wet

Det

entio

n

Bui

lt W

etla

nd

Rai

n G

arde

n

Exfil

tratio

n

Jordan/Falls Lake Model x x x x x x x x x x

BMP SELECT Model x x x x x x x xClinton River SET x x x x x x x xVirginia Runoff

Reduction x x x x x x

DES Simple Method Pollutant Loading x x x x x x x x x x

Colorado x x x x x x x xD.C. Green x x x x

SMADA x x x xBMPTRAINS x x x x x x x x x x

WHAT WOULD BE NEEDED TO DESIGN EFFECTIVE STORMWATER BMP TREATMENT TRAINS AND QUANTIFY LOAD

REDUCTIONS?• Current “presumptive BMP design criteria” do not achieve high

level of treatment needed for discharges to impaired water bodies – need LID BMPs to expand toolbox

• Must be able to quantify the pre-development stormwater loadings

• Must be able to quantify the post-development stormwater loadings

• Must be able to quantify and demonstrate effectiveness of each BMP, including LID BMPs, in treatment trains

• AND.. Calculate relative costs of various BMP combinations

WHY BMPTRAINS MODEL

• Model developed in cooperation with DEP, WMDs, consultants, and DOT• Model is in the public domain• Model incorporates the latest information relative to designing stormwater

treatment systems in Florida:• Florida annual rainfall by zones and location• Includes local watershed soil and cover conditions• Statewide Event Mean Concentrations• Statewide stormwater BMP effectiveness data • Latest LID BMP effectiveness data• Stormwater LID BMP design criteria (developed for Statewide

Stormwater Rule)

USE OF THE BMPTRAINS MODEL

• Evaluates whether a project is meeting Net Improvement• Evaluates site planning/BMP treatment train options• Evaluates load reduction of BMP treatment train options• Evaluates costs of BMP treatment train options• Used to evaluate ERP/BMP options for projects in Lee

County, Pinellas County• Used to evaluate BMP options for St. Joe Sector Plan in

Bay County • Used to evaluate LID options in ERP aps to DEP & WMDs• Used by FDOT and their consultants

SUMMARY

• The LID BMPs in the Pinellas County LID Manual provide new tools that reduce the volume and pollutant loading of stormwater discharges.

• The five highlighted LID BMPs in the Manual reduce the volume of stormwater discharge thereby reducing stormwater pollutant loadings. Pervious pavements and rain gardens function as storage with infiltration areas. The volume of runoff decreases when the impervious area is reduced or is disconnected

using pervious areas for pre-treatment. Greenroof storage adds to evapotranspiration, thus reduces discharge volume. Swales partly infiltrate, and usually are part of the transport drainage system.

• Efficiencies of LID BMPs and BMP treatment trains vary throughout the State due to variability in rainfall and runoff characteristics. Site specific data is available for Pinellas County.

• Computational aids should simplify and validate the calculations for a project site. BMPTRAINS model satisfies all requirements for a reasonable prediction of performance.

B Y : C L AR K H U L L , E R I C L I V I N G S T O N AN D M AR T Y W AN I E L I S T A

QUESTIONS, REMARKS AND DISCUSSION

2017Pinellas County

Pinellas County Stormwater Management Manual Training

Workshop

Characteristics of Rainfall Events at Selected Meteorological Sites

- Rainfall is highly variable in the number of “small” and “large” events -This impacts both runoff generation as well as treatment system

performance efficiency

Bra

nfor

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Cro

ss C

ity

Ft.

Mye

rs

Jac

kson

ville

Key

Wes

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Mel

bour

ne

Mia

mi

Orla

ndo

Pen

saco

la

Tal

laha

ssee

Tam

pa

Perc

ent o

f Ann

ual R

ainf

all E

vent

sLe

ss T

han

1 in

ch (%

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94 B

ranf

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Mye

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Tam

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Num

ber o

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ual R

ainf

all E

vent

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160

Highest: 158 events in MiamiLowest: 104 events in Cross City

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Mel

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Mia

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Orla

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Mea

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dant

Dry

Per

iod

(day

s)

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Dry Season Wet Season

VARIABILITY IN INTER-EVENT DRY PERIOD

Variability in rainfall inter-event

times impacts:

- Runoff C values

- Recovery and performance efficiency of stormwater management systems, especially dry retention

4.40

2.27

3.96

3.03

4.143.92

3.59

4.87

5.63

3.36

3.73

4.65

1.42

FLORIDA EMC VALUESLand Use CategoryEMC (mg/l)

Total N Total PLow Density Residential1 1.645 0.27

Single Family 2.07 0.327

Multi-Family 2.32 0.520

Low Intensity Commercial 1.13 0.188

High Intensity Commercial 2.40 0.345

Light Industrial 1.20 0.260

Highway 1.52 0.200

Agricultural

Pasture 3.51 0.686

Citrus 2.24 0.183

Row Crops 2.65 0.593

Mining/Extractive 1.18 0.150

Range land/park land 1.15 0.055

Natural vegetative community 1.22 0.213

- Values reflect discharge concentrations without any

pre-treatment

NOTE: In BMPTRAINS, there is an overwriteto the these default concentrations and check with reviewers for overwrite conditions

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

LD R

es.

SF R

es.

MF

Res.

LI C

omm

.

HI C

omm

Indu

stria

l

High

way

Past

ure

Citr

us

Row

Cro

ps

Min

ing

Comparison of Typical Nitrogen Concentrations in Stormwater from Developed Lands

Typical natural

area conc.Tota

l Nitr

ogen

Con

c. (m

g/L)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

LD R

es.

SF R

es.

MF

Res.

LI C

omm

.

HI C

omm

Indu

stria

l

High

way

Past

ure

Citr

us

Row

Cro

ps

Min

ing

Comparison of Typical PhosphorusConcentrations in Stormwater from Developed Lands

Typical natural

area conc.

Tota

l Pho

spho

rus C

onc.

(mg/

L)

Monitored State Parks Used for Natural Area EMCs

Source: ERD, Orlando

SUMMARY OF FLORIDA UPLAND LAND USE CLASSIFICATIONS(SOURCE: FFWCC)

ClassificationArea

(acres)Percent of Total

Coastal Strand 15,008 0.1Dry Prairie 1,227,697 11.4

Hardwood Hammock/Forest 980,612 9.1Mixed Pine/Hardwood Forest 889,010 8.3

Pinelands 6,528,121 60.7Sand Pine Scrub 194,135 1.8

Sandhill 761,359 7.1Tropical Hardwood Hammock 15,390 0.1

Xeric Oak Scrub 146,823 1.4Totals: 10,758,155 100.0

Monitored natural areas include more than 92% of upland land covers in Florida

Land Type N Total N(µg/l)

Total P(µg/l)

Dry Prairie 12 2,025 184Marl Prairie 6 684 12

Mesic Flatwoods 30 1,087 43Ruderal/Upland Pine 5 1,694 162Scrubby Flatwoods 13 1,155 27Upland Hardwood 79 1,042 346

Wet Flatwoods 76 1,213 21Wet Prairie 23 1,095 15Xeric Scrub 3 1,596 156

Natural Land Use Runoff Concentrations

SCS CURVE NUMBER (CN)METHODOLOGY

• Common methodology used in many public and proprietary models, Ref: NRCS TR-55 document titled “Urban Hydrology for Small Watersheds”

• Curve numbers are empirically derived values which predict runoff as a function of soil type and land cover

• Can be used to predict runoff depths and volumes

• Runoff generation based on impervious area, soil types, and land cover

• Model incorporates two basic parameters:• Directly connected impervious area (DCIA)

• Percentage of impervious area with a direct hydraulic connection to the drainage system (0 – 100%)• Curve Number (CN)

• Measure of the runoff generating potential of the pervious areas (grass, landscaping, etc.) and impervious areas which are not DCIA (30 – 100)

HOURLY RAINFALL SITES USED FOR RUNOFF

MODELING

- 45 SITES TOTAL

- RUNOFF MODELING CONDUCTED FOR EACH RAIN

EVENT AT EACH SITE OVER AVAILABLE PERIOD OF

RECORD

Meteorological Sites Included in Runoff Modeling

C VALUES FOR VARIOUS COMBINATIONS OF CN AND DCIA IN PINELLAS COUNTY

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 10030 0.004 0.045 0.086 0.127 0.168 0.209 0.250 0.291 0.332 0.373 0.414 0.455 0.496 0.536 0.577 0.618 0.659 0.700 0.741 0.782 0.82335 0.007 0.048 0.089 0.129 0.170 0.211 0.252 0.293 0.333 0.374 0.415 0.456 0.497 0.537 0.578 0.619 0.660 0.701 0.741 0.782 0.82340 0.011 0.051 0.092 0.133 0.173 0.214 0.254 0.295 0.336 0.376 0.417 0.458 0.498 0.539 0.579 0.620 0.661 0.701 0.742 0.782 0.82345 0.016 0.056 0.096 0.137 0.177 0.217 0.258 0.298 0.339 0.379 0.419 0.460 0.500 0.540 0.581 0.621 0.662 0.702 0.742 0.783 0.82350 0.022 0.062 0.102 0.142 0.182 0.222 0.262 0.302 0.342 0.382 0.423 0.463 0.503 0.543 0.583 0.623 0.663 0.703 0.743 0.783 0.82355 0.030 0.070 0.109 0.149 0.189 0.228 0.268 0.308 0.347 0.387 0.427 0.466 0.506 0.546 0.585 0.625 0.664 0.704 0.744 0.783 0.82360 0.040 0.080 0.119 0.158 0.197 0.236 0.275 0.314 0.353 0.393 0.432 0.471 0.510 0.549 0.588 0.627 0.667 0.706 0.745 0.784 0.82365 0.054 0.092 0.131 0.169 0.208 0.246 0.285 0.323 0.362 0.400 0.438 0.477 0.515 0.554 0.592 0.631 0.669 0.708 0.746 0.785 0.82370 0.071 0.109 0.147 0.184 0.222 0.259 0.297 0.335 0.372 0.410 0.447 0.485 0.522 0.560 0.598 0.635 0.673 0.710 0.748 0.785 0.82375 0.096 0.132 0.168 0.205 0.241 0.277 0.314 0.350 0.387 0.423 0.459 0.496 0.532 0.568 0.605 0.641 0.678 0.714 0.750 0.787 0.82380 0.130 0.165 0.199 0.234 0.268 0.303 0.338 0.372 0.407 0.442 0.476 0.511 0.546 0.580 0.615 0.650 0.684 0.719 0.754 0.788 0.82385 0.182 0.214 0.246 0.278 0.310 0.342 0.374 0.406 0.438 0.470 0.502 0.534 0.566 0.599 0.631 0.663 0.695 0.727 0.759 0.791 0.82390 0.266 0.294 0.322 0.350 0.378 0.406 0.433 0.461 0.489 0.517 0.545 0.573 0.600 0.628 0.656 0.684 0.712 0.740 0.767 0.795 0.82395 0.429 0.449 0.469 0.488 0.508 0.528 0.547 0.567 0.587 0.606 0.626 0.646 0.665 0.685 0.705 0.725 0.744 0.764 0.784 0.803 0.82398 0.616 0.626 0.636 0.647 0.657 0.667 0.678 0.688 0.699 0.709 0.719 0.730 0.740 0.750 0.761 0.771 0.782 0.792 0.802 0.813 0.823

Percent DCIA

Zone 4Mean Annual Runoff Coefficients (C Values) as a Function

of DCIA Percentage and Non-DCIA Curve Number (CN)NDCIA

CN

Pensacola/Tallahassee

Curve Number

30 40 50 60 70 80 90 100

DCIA

0

10

20

30

40

50

60

70

80

90

100

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Runoff Coefficient

Key West

Curve Number

30 40 50 60 70 80 90 100DC

IA0

10

20

30

40

50

60

70

80

90

100

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Runoff Coefficient

Annual C Values as a Function of DCIA and non-DCIA Curve Number