U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2009–5196 

Prepared in cooperation with the Wisconsin Department of Transportation and the 

Wisconsin Department of Natural Resources 

Parking Lot Runoff Quality and Treatment Efficiency 

of a Stormwater-Filtration Device, Madison, Wisconsin, 

2005–07 
Cover: A stormwater-filtration device installed in an employee parking lot in downtown Madison, Wisconsin. (Photograph from 

Earth Tech, Inc., September 2004.) 
Parking Lot Runoff Quality and Treatment 

Efficiency of a Stormwater-Filtration Device, 

Madison, Wisconsin, 2005–07 

By Judy A. Horwatich and Roger T. Bannerman 

Prepared in cooperation with the Wisconsin Department of Transportation and 

the Wisconsin Department of Natural Resources 

Scientific Investigations Report 2009–5196 

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Horwatich, J.A., and Bannerman, R.T., 2010, Parking lot runoff quality and treatment efficiency of a stormwater-filtration device, Madison, Wisconsin, 2005–07: U.S. Geological Survey Scientific Investigations Report 2009–5196, 50 p. 
iii

Contents 

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................2

Site Description.....................................................................................................................................3

Previous Investigations........................................................................................................................4

Design of the Stormwater-Filtration Device..............................................................................................4

Methods...........................................................................................................................................................6

Water-Quality Sampling and Analysis ..............................................................................................6

Precipitation...........................................................................................................................................7

Flow Monitoring ....................................................................................................................................8

Calibration of Gage Height .........................................................................................................8

Calibration of Flow.......................................................................................................................9

Inlet Flows............................................................................................................................9

Outlet Flows .........................................................................................................................9

Monitoring Complications ........................................................................................................10

Quality Control.....................................................................................................................................10

Processing of Water-Quality Samples ............................................................................................11

Particle-Size Analysis ........................................................................................................................11

Treatment Efficiency of the Stormwater-Filtration Device ...................................................................11

Precipitation Data...............................................................................................................................12

Stormwater-Flow Data.......................................................................................................................13

Number of Events with Water-Quality Data ...................................................................................13

Particle-Size Distributions.................................................................................................................13

Water-Quality Data for the Inlet and Outlet....................................................................................14

Efficiency Calculations ......................................................................................................................16

Efficiency Ratio....................................................................................................................................17

Summation of Loads...........................................................................................................................18

Summary........................................................................................................................................................20

Acknowledgments.......................................................................................................................................20

References Cited..........................................................................................................................................21

Appendix 1. List of References for Previous Investigations .............................................................23 

Appendix 2. Tables of Sample Analyses Results.................................................................................26

Figures

1. Aerial photograph showing the study area including the drainage area of the 

parking lot, and location of the islands, manholes, and flow-splitter box and 

storm-sewer pipes........................................................................................................................3

2. Photograph showing the flow-splitter box upstream from the stormwater-filtration 

device, representing the inlet pipe, the overflow weir, and the bypass pipe.....................4
iv

3. Diagram showing the components of the stormwater-filtration device .............................5

4–6. Photographs showing:

4. The flow spreader and the modification made to the internal bypass weir 

of the stormwater-filtration device...................................................................................5

5. Automatic sampling equipment.........................................................................................6

6. Inlet pipe with stabilization bar.........................................................................................8

7. Graph showing dye-dilution flow in relation to area-velocity flow at the inlet of 

the stormwater-filtration device.................................................................................................9

8. Photograph showing the dye-dilution equipment.................................................................10

9. Graph showing the cumulative precipitation for the study period (2005–07) 

in relation to the cumulative frequency for all precipitation greater than 

0.19 inches (1949–92) based on the National Oceanic and Atmospheric 

Administration precipitation gage at Dane County Regional Airport, Madison, Wis......13

10. Graph showing the stormwater volumes at the inlet of the stormwaterfiltration device corrected by dye dilution in relation to outlet volumes, 

Madison, Wis., 2007....................................................................................................................14

Tables

1. Limits of detection and analytical methods for inorganic constituents analyzed 

in samples collected at the stormwater-filtration device, Madison, Wis. ..........................7

2. Limits of detection and analytical methods for polycyclic aromatic hydrocarbons 

analyzed in samples collected at the stormwater-filtration device, Madison, Wis. .........8

3. Monthly precipitation at the U.S. Geological Survey raingage and the National 

Oceanic and Atmospheric Administration precipitation gage at the Dane County 

Regional Airport, Madison, Wis., 2005–07 ..............................................................................12

4. Average particle-size distribution in stormwater samples collected from the 

inlet and outlet of a stormwater-filtration device, Madison, Wis.......................................14

5. Summary statistics for selected water-quality constituents in samples collected 

from a stormwater-filtration device, Madison, Wis..............................................................15

6. Summary statistics for individual polycyclic aromatic hydrocarbons in 15 

samples collected from a stormwater-filtration device, Madison, Wis. ...........................16

7. Efficiency ratios for selected constituents in samples from a stormwaterfiltration device, Madison, Wis., 2005–07 ...............................................................................17

8. Efficiency ratios for selected polycyclic aromatic hydrocarbons in samples from 

a stormwater-filtration device, Madison, Wis., 2005–07......................................................18

9. Summation of loads of selected constituents and percent efficiency for a 

stormwater-filtration device, Madison, Wis., 2005–07 .........................................................19

2–1. Concentrations of selected constituents in equipment-field-blank data collected 

from a stormwater-filtration device, Madison, Wis., 2005–07.............................................26

2–2. Relative percent difference for concentrations of selected constituents in field 

replicate samples collected from a stormwater-filtration device and sample, 

Madison, Wis., 2005–07 .............................................................................................................27

2–3. Precipitation during sampling events from a stormwater-filtration device, 

Madison, Wis., 2005–07 .............................................................................................................29

2–4. Outlet flow volumes, percent runoff, and peak discharge for sampled events at 

a stormwater-filtration device, Madison, Wis., 2005–07......................................................34
v

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

millimeter (mm) 0.03937 inch (in.)

Area

acre 4,047 square meter (m2)

square foot (ft2) 929.0 square centimeter (cm2)

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3)

cubic foot (ft3) 0.02832 cubic meter (m3)

liter (L) 61.02 cubic inch (in3)

Flow rate

foot per second (ft/s) 0.3048 meter per second (m/s)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

milliliter per second (mL/s) .00003531 cubic foot per second (ft3/s)

Mass

pound, avoirdupois (lb) 0.4536 kilogram (kg)

gram (g) 0.03527 ounce, avoirdupois (oz)

Conversion Factors and Abbreviations

2–5. Concentrations of suspended solids, suspended sediment, volatile solids, and 

dissolved solids in stormwater samples collected from a stormwater-filtration 

device, Madison, Wis., 2005–07 ...............................................................................................36

2–6. Concentrations of selected constituents and physical properties in stormwater 

samples collected from a stormwater-filtration device, Madison, Wis., 2005–07...........38

2–7. Mean concentrations of selected polycyclic aromatic hydrocarbons in samples 

collected from a stormwater-filtration device, Madison, Wis., 2005–07...........................40

2–8. Particle-size distributions in samples collected from a stormwater-filtration 

device, Madison, Wis., 2005–07 ...............................................................................................42

2–9. Loads of suspended solids, suspended sediment, volatile solids, and dissolved 

solids in stormwater samples collected from a stormwater-filtration device, 

Madison, Wis., 2005–07 .............................................................................................................44

2–10. Loads of selected constituents in stormwater samples collected from a 

stormwater-filtration device, Madison, Wis., 2005–07 .........................................................46

2–11. Loads of selected polycyclic aromatic hydrocarbons in stormwater samples 

collected from a stormwater-filtration device, Madison, Wis., 2005–07...........................48

2–12. Parking lot comparison of geometric concentrations from several studies in 

Wisconsin ....................................................................................................................................50
vi

Abbreviations used in this report 

Cl chloride

COD chemical oxygen demand

DCRA Dane County Regional Airport

DCOD dissolved chemical oxygen demand

DCu dissolved copper

DP dissolved phosphorus

DZn dissolved zinc

EMC event mean concentration

LOQ limit of quantification

MCTT Multi-Chamber Treatment Tank

NOAA National Oceanic and Atmospheric Administration

NURP Nationwide Urban Runoff Program

PAH polycyclic aromatic hydrocarbon

PSD particle-size distribution

QA/QC quality-assurance/quality-control

RPD relative percent difference

SFD stormwater-filtration device

SOL summation of loads

SRS standard reference sample

SS suspended sediment

TCu total copper

TDS total dissolved solid

TP total phosphorus

TSS total suspended solid

TZn total zinc

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

WDNR Wisconsin Department of Natural Resources

WisDOT Wisconsin Department of Transportation

WinSLAMM Windows Source Load and Management Model

WSLOH Wisconsin State Laboratory of Hygiene

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows: 

°C=(°F-32)/1.8

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).

Particle sizes of sediment are given in micrometers (μm). A micrometer is one-thousandth of a 

millimeter.

Concentrations of sieved solids as a dried weight are in milligrams per kilogram (mg/kg). 
Abstract

To evaluate the treatment efficiency of a stormwaterfiltration device (SFD) for potential use at Wisconsin Department of Transportation (WisDOT) park-and-ride facilities, a 

SFD was installed at an employee parking lot in downtown 

Madison, Wisconsin. This type of parking lot was chosen 

for the test site because the constituent concentrations and 

particle-size distributions (PSDs) were expected to be similar 

to those of a typical park-and-ride lot operated by WisDOT. 

The objective of this particular installation was to reduce loads 

of total suspended solids (TSS) in stormwater runoff to Lake 

Monona. This study also was designed to provide a range of 

treatment efficiencies expected for a SFD. Samples from the 

inlet and outlet were analyzed for 33 organic and inorganic 

constituents, including 18 polycyclic aromatic hydrocarbons 

(PAHs). Samples were also analyzed for physical properties, 

including PSD. Water-quality samples were collected for 51 

runoff events from November 2005 to August 2007. Samples 

from all runoff events were analyzed for concentrations of 

suspended sediment (SS). Samples from 31 runoff events were 

analyzed for 15 constituents, samples from 15 runoff events 

were analyzed for PAHs, and samples from 36 events were 

analyzed for PSD.

The treatment efficiency of the SFD was calculated 

using the summation of loads (SOL) and the efficiency ratio 

methods. Constituents for which the concentrations and (or) 

loads were decreased by the SFD include TSS, SS, volatile 

suspended solids, total phosphorous (TP), total copper, total 

zinc, and PAHs. The efficiency ratios for these constituents are 

45, 37, 38, 55, 22, 5, and 46 percent, respectively. The SOLs 

for these constituents are 32, 37, 28, 36, 23, 8, 

and 48 percent, respectively. The SOL for chloride was -21 

and the efficiency ratio was -18. Six chemical constituents or 

properties—dissolved phosphorus, chemical oxygen demand, 

dissolved zinc, total dissolved solids, dissolved chemical 

oxygen demand, and dissolved copper—were not included 

in the efficiency or SOL, because the difference between 

concentrations in samples from the inlet and outlet were not 

significant. Concentrations of TP and TSS were inexplicably 

high in samples at the inlet for one event.

Introduction

An Administrative Rule has been established by the 

Wisconsin Department of Transportation (WisDOT) (Wisconsin Administrative Code, 2002) to control the stormwaterquality runoff from transportation facilities, such as highways, 

airports, and railroads. The rule was established to comply 

with the administrative rules for non-agricultural and runoffmanagement performance standards established by the Wisconsin Department of Natural Resources (WDNR) (Wisconsin 

Administrative Code, 2004). A major element of the administrative rule is the control of total suspended solids (TSS) in 

stormwater runoff from post-construction sites and developed 

urban areas. For new development, the performance standard 

requires that loads of TSS be reduced by at least 80 percent for 

those facilities constructed after January 1, 2003 (Wisconsin 

Administrative Code, 2002). The rule requires a performance 

standard of at least a 40-percent reduction in loads of TSS 

for highway reconstruction and non-highway redevelopment 

(Wisconsin Administrative Code, 2002). To evaluate post-construction performance, the WDNR allows the use of a computer simulation model, such as the Windows Source Load 

and Management Model (WinSLAMM) to determine TSS 

load reduction. In addition, the U.S. Environmental Protection 

Agency Phase I and Phase II stormwater regulations result 

in additional focus on the quality of flow from transportation 

facilities (U.S. Environmental Protection Agency, 2000).

To find the most cost-effective ways of complying 

with the TSS performance standard, WisDOT has supported 

evaluations of several devices that reduce contaminants from 

freeways. These include street-cleaning devices evaluated in 

Milwaukee (Waschbusch, 2003) and Madison (Wendy Braun, 

Wisconsin Department of Transportation, written commun., 

2006). Two prefabricated devices were evaluated in Milwaukee; these include a stormwater-filtration device (SFD) (similar to the one used in this study) and a hydrodynamic settling 

device (U.S. Environmental Protection Agency, 2004; 2005).

Parking Lot Runoff Quality and Treatment Efficiency 

of a Stormwater-Filtration Device, Madison, Wisconsin, 

2005–07 

By Judy A. Horwatich and Roger T. Bannerman1 

________________

1

 Wisconsin Department of Natural Resources
2 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

To evaluate the treatment efficiency of a SFD for WisDOT transportation facilities—for example, a park-and-ride 

lot—a SFD was installed in an employee parking lot. The 

objective of this particular installation was to reduce loads 

of TSS in stormwater runoff to Lake Monona. This site has 

a similar rate of usage as a park-and-ride lot. Because the 

WisDOT has already tested a SFD that treated runoff from 

a freeway, it was considered important to select a WisDOT 

facility with different levels of contaminants and a different 

distribution of mean particle size from those at the freeway 

site. Therefore, WisDOT, Madison Gas and Electric Company 

(MGE) (owner of the parking lot), WDNR, and the U.S. Geological Survey (USGS) developed this cooperative study to 

determine the reductions of contaminants when a SFD is used 

at a typical parking lot facility. This study also was designed to 

provide a range of treatment efficiencies expected for a SFD.

A SFD is among the emerging prefabricated stormwatercontrol devices designed to provide at least a 40-percent 

reduction of TSS without requiring a lot of space. Space can 

be a limitation at some transportation facilities, such as parkand-ride lots in highly urbanized areas. Many facilities in 

highly urbanized areas will need to meet the 40-percent TSS 

performance standard at redevelopment sites and in developed 

urban areas. To save space, most of the devices are installed 

underground or above ground as a landscaping feature. 

Because single-chamber settling devices, such as catchment 

basins, have not achieved TSS reductions of 40 percent 

(Waschbusch, 1999; U.S. Environmental Protection Agency, 

2005), most of the newer devices incorporate filters to achieve 

higher levels of TSS reduction in a relatively small space.

Bioretention systems and Multi-Chamber Treatment 

Tanks (MCTTs) are two examples of newer non-structural 

stormwater-control devices using filtration as part of the treatment process (Prince George’s County, 2002; Pitt and others, 

1999). Bioretention systems are a landscaping feature capable 

of reducing the TSS load by at least 80 percent (Hunt, 2006). 

This stormwater-control feature usually has a mixture of sand, 

compost, and native soil that is 3 ft thick and serves drainage 

areas of less than 2 acres. More study would be needed of 

the maintenance requirements, filter thicknesses, and mixture 

to improve TSS reduction. Bioretention systems are gaining 

widespread acceptance in Wisconsin as a method for treating 

stormwater runoff from parking lots. A 98-percent load reduction in TSS was achieved by an MCTT installed underground 

in a maintenance yard in Milwaukee, Wisconsin (Corsi and 

others, 1999). The MCTT contained a mixture of sand, peat 

moss, and activated carbon. Because limited technical and 

maintenance support are available, MCTTs have been installed 

in only a few places around the country.

Prefabricated devices are an alternative to the non-structural ones. Advantages to using prefabricated devices include 

technical support from the manufacturer and they are usually 

designed for easy maintenance. However, the TSS reductions 

for these devices have not been verified and any testing has 

been limited by site-specific characteristics of the stormwater 

runoff.

Prefabricated filtration devices installed underground 

have achieved at least a 40-percent reduction in TSS load at a 

hospital parking lot in Green Bay, Wisconsin, and on a freeway in Milwaukee, Wisconsin (Horwatich and others, 2004; 

U.S. Environmental Protection Agency, 2004). A prefabricated 

pressurized sand filter reduced the TSS load by 80 percent in 

runoff from a hospital parking lot. The SFD at the freeway site 

reduced the TSS load by 50 percent.

The ability of the SFD to exceed a 40-percent TSS load 

reduction at a freeway site does not guarantee that the filter 

will achieve the same level of TSS load reduction at other 

types of WisDOT facilities, such as park-and-ride lots and 

maintenance yards. Each type of facility may have different 

levels of contaminants and particle-size distributions. Testing the SFD at the employee parking lot in Madison will help 

quantify the efficiencies of using this filter at park-and-ride 

lots. It also may provide the additional data needed to calibrate 

and verify the SFD efficiency equations in an urban stormwater-runoff model. 

Purpose and Scope

This report describes the process of monitoring stormwater runoff at the inlet, outlet, and bypass pipes of a stormwaterfiltration device installed at an employee parking lot in downtown Madison, Wis. The report also describes the methods for 

determining the efficiency of the device.

Precipitation, flow-volume, particle-size, and concentration data collected from November 5, 2005, to August 18, 

2007, are reported. Precipitation erosivity, antecedent dry 

days, and peak flow data are presented in appendixes. Precipitation, flow volume, and concentrations of suspended sediment 

were recorded for 51 storm events. Concentrations in samples 

collected during 31 runoff events are reported for 15 constituents analyzed including dissolved and particulate solids, 

inorganic compounds, organic compounds, and recoverable 

metals. Particle-size distributions are presented for 36 runoff 

events and concentrations of 18 polycyclic aromatic hydrocarbons (PAHs) are presented for 15 runoff events.

New methods are presented for determining particle-size 

distributions and processing samples with a churn splitter 

are presented. Constituent concentrations in samples from 

the SFD inlet were compared with concentrations from other 

source areas, such as a high-turnover parking lot at a hospital.

A goal of the current project was to verify the results of 

the WinSLAMM model. Data from the parking lot study and 

the Milwaukee freeway studies can be modeled in WinSLAMM using TSS reduction devices. For example, WinSLAMM simulates hydrodynamic settling devices (such as the 

one evaluated in Milwaukee) utilizing Stokes law equation, 

which is based on particle-size distribution and flow velocity to determine the particle-size dropout rate through the 

device (Pitt, 2003). The efficiency of other stormwater-control 

devices can be affected depending on which particle-size 

distribution is applied in the model. The manufacturer of the 
Introduction 3

SFD used in the study and the developers of WinSLAMM are 

cooperatively designing the algorithm to include their SFDs in 

the model. If the calibration and verification are successful, the 

model could be used to estimate the efficiencies from a SFD at 

any transportation facility when appropriate source-area data 

are available.

This report also adds to the understanding of stormwater 

quality and quantity in an urban environment. Concentrations 

of constituents in samples from storm-sewer inlets are compared with concentrations from other types of source areas, 

such as a high-turnover parking lot at a hospital. These results 

help identify the relative importance of different source areas 

and characterize the potential impact of the stormwater on 

receiving waters.

Site Description

In June 2003, MGE installed a stormwater-filtration 

device called a StormFilter at an employee parking lot in 

downtown Madison, Wis. (fig. 1). The filter cartridges were 

replaced in May 2005, just before sampling began. The area 

of the parking lot was originally determined to be 1.3 acres 

(using an available surface-elevation map) but was later 

revised to 0.91 acres. The asphalt parking lot has 181 parking 

stalls occupied mostly by employees’ cars with a few stalls for 

visitor parking. On weekends and weeknights, the parking lot 

is used for overflow parking of downtown businesses. Most 

contaminants deposited on the parking lot are delivered by 

cars and atmospheric deposition. Salt is applied in the winter 

as needed. Stormwater from the site flows from a 15-in. stormsewer pipe, then into a 48 by 76-in. storm-sewer culvert, 

and then flows to Lake Monona. The maintenance plan for 

the parking lot states that a layer of seal coat is to be applied 

periodically. A seal coat of coal tar was last applied in 2000 

(James Montgomery, Madison Gas and Electric Company, oral 

commun., 2006).

The parking lot is divided into three areas, and each area 

has about the same number of stalls. A 4-ft-wide gravel island 

separates the areas from each other, and there is an island at 

each end of the parking lot. When parked, all the cars face an 

island. Stormwater draining from the parking lot flows into 

storm-sewer grates in the north and south islands. These grates 

are attached to a 15 in.-diameter storm-sewer pipe that flows 

to the SFD (fig. 1).

"

Manhole #2

Manhole # 1

FlowSplitter

Device

Islands

Islands

Islands

Figure 1. Study area including the drainage area of the parking lot (outlined in red), and location of the islands, 

manholes, and flow-splitter box and storm-sewer pipes (lined in yellow). 
4 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

The gravel islands do not have curbs, so the stormwater 

from the parking lot can flow into the islands. Underneath the 

gravel is a sheet of thick black plastic. An inspection revealed 

that holes have developed in the plastic, which could allow 

additional infiltration through the islands. The gravel islands 

consist of 0.06 acres. The islands probably contribute runoff 

during large, intense runoff events but store water during small 

events.

The parking lot was built in 1986. Over time, depressions 

have formed in the pavement. Small depressions have formed 

in many of the stalls where the wheels of cars sit. Larger 

depressions have formed in the driving lanes between stalls. 

Deposited sediment was observed in most of the depressions. 

Puddles formed in these depressions after rainfall.

Underneath the parking lot, the soil profile from bottom 

upward consists of a fibrous peat and organic soil mixture at 

7.5 ft; above that is 5.5 ft of fill material consisting of dark 

brown silty sand with pebbles. The next layer is 1.25 ft of fill 

material, consisting of concrete rubble with sand; above that is 

a base course 7 in. deep. The parking lot surface layer is 2 in. 

of asphaltic concrete. The water table is approximately 6 ft 

below the parking lot.

Previous Investigations

The USGS has a long history of conducting urban 

water-quality investigations in Wisconsin. In 1978, the 

U.S. Environmental Protection Agency (USEPA) established 

the Nationwide Urban Runoff Program (NURP) to assess the 

water-quality characteristics of urban runoff. When the city of 

Milwaukee, Wis., was chosen by the USEPA as a NURP site, a 

partnership between the WDNR and the USGS was developed 

to evaluate urban runoff in Milwaukee. Since the NURP study, 

the USGS and the WDNR have continued their partnership 

and have completed more than 15 studies in at least 6 cities 

to assist the State of Wisconsin in characterization of urban 

stormwater runoff. See appendix 1 for a list of references for 

these investigations.

Design of the Stormwater-Filtration 

Device

The SFD removes contaminants through filtration and 

sedimentation. Filtration, considered the primary method of 

treatment, is done by means of a filter media that physically 

removes particles by retaining contaminants through sorption. 

Each of the 26 filter cartridges in the SFD was filled with ZPG 

media, a mixture of zeolite, perlite, and granular activated 

carbon. The filter media was designed to remove sediments, 

recoverable metals, organic compounds, phosphorus, oils, and 

greases. Sedimentation of larger particles occurs in a pretreatment chamber and on the bottom of the cartridge-filter bay.

The device was designed to treat stormwater runoff 

from an impervious area of 1.3 acres, but runoff coefficients 

measured during the study indicated that the drainage area had 

not been determined correctly. The runoff coefficients using 

the 1.3 acres averaged about 40 percent, which was much 

lower than the expected runoff coefficients—around 70 percent (Horwatich and others, 2004). The correct drainage-area 

divides were determined by watching the direction of flow 

when water was applied with a hose. The correct area of the 

watershed was 0.91 acres; therefore, the SFD was over-sized 

for the site.

Stormwater from the parking lot enters into a precast 4-ftlong flow-splitter-box manhole (figs. 1 and 2). An adjustable 

external-weir plate is set in the center of the box at a height of 

2.17 ft. At 90 degrees from of the weir plate, a 6-in.-diameter 

low-flow inlet pipe transfers stormwater into the device 

(fig. 2). If the stormwater rises more than 2.17 ft in the flowsplitter box, it bypasses the SFD through a 15-in.-diameter 

pipe; this stormwater is not treated.

Figure 2. Flow-splitter box upstream from the stormwaterfiltration device, representing the inlet pipe, the overflow weir, and 

the bypass pipe (top view). 

The SFD was housed in a concrete structure that was 

6 in. thick, 16 ft long, 8 ft wide, and 5.5 ft deep (fig. 3). Stormwater enters from the inlet pipe into a 2 ft wide, 1.67 ft deep 

inlet bay, which acts as a pretreatment chamber and energy 

dissipater (fig. 4). It then flows through a flow spreader that 

disperses water evenly into a 7.4-ft-long cartridge bay.

Flow rates were controlled through the filter cartridges 

by a siphon action, and the water exited the cartridge through 

an underdrain manifold. Each cartridge was designed to treat 

a peak flow of 0.033 ft3/s, and combined, the cartridges could 

treat a peak flow of 0.87 ft3/s. When inlet flows exceeded 

0.87 ft3/s, water bypassed the filter cartridges by way of the 

high-flow bypass weir at a height of 1.83 ft (fig. 3). Treated 

water from the underdrain manifold and untreated internal bypass water entered the outlet bay area (8 ft long by 

2.3 ft wide) and then flowed through a 6-in.-diameter outlet 

pipe (James Bachhuber, Earth Tech, written commun., 2004).

External weir plate

Bypass 

pipe

Inlet into the device
Design of the Stormwater-Filtration Device 5

Figure 3. Components of the stormwater-filtration device (U.S. Environmental Protection Agency, 2004). 

Figure 4. The flow spreader and the modification made to the internal bypass weir of the stormwater-filtration device. Each 

black cylinder contains a filter cartridge. 

Access doors

Inlet pipe

Energy dissipator

Flow spreader

Ladder

Flow spreader

Outlet pipe

Discharge

High flow bypass

StormFilter cartridge Filtration bay

Internal bypass 

weir

Flow spreader
6 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

The manufacturer recommended that sediment be 

removed from the pretreatment chamber as necessary and 

that the filters be inspected once a year to determine whether 

replacement was needed. However, the filters did not need 

replacement during the project in part for the following reasons: (1) the device was designed to treat runoff from 1.3 acres 

rather than the effective runoff area of 0.91 acres, and (2) the 

removal efficiencies of the device were not observed to diminish during the monitoring period. Personnel from the manufacturer inspected the SFD on August 17, 2007, the day after 

sampling was completed, and determined the device remained 

in good working order.

Methods

Stormwater runoff was measured and collected at the 

inlet, outlet, and bypass pipes of the SFD. Each pipe was 

equipped with automated stormwater-quality samplers and 

instruments to measure water level and velocity. Precipitation 

data was collected by use of a tipping-bucket raingage. Measurement, control, and storage of data were done by means 

of electronic dataloggers. Data were automatically retrieved 

twice daily using telephone modems. Descriptive statistics for 

stormwater runoff events from the SFD are detailed in appendixes 2–3 and 2–4.

Water-Quality Sampling and Analysis 

Water-quality samples were collected from the inlet, 

outlet, and bypass pipes of the SFD over 2.5 years. Station 

identification numbers and names for each sampling location 

are 430440089223500, MGE Stormwater Filter Inlet at Madison, Wis.; 430440089223400 MGE Stormwater Filter Outlet 

at Madison, Wis.; and 430440089223401, MGE Stormwater 

Filter Bypass at Madison, Wis.

Automatic samplers (fig. 5) were programmed to collect 

flow-weighted samples from the three pipes. The datalogger in 

the monitoring station was programmed to initiate a subsample 

for a predefined volume of flow; consequently, more subsamples were collected for large-volume runoff events than for 

small-volume runoff events. Flow-weighted sampling allowed 

for the collection of one composite sample for a stormwater 

runoff event, consisting of numerous subsamples collected 

throughout the course of the event. This approach resulted in a 

single flow-weighted or “event mean” concentration for each 

runoff event. The sample tubing of the inlet automatic sampler 

was installed 1 ft upstream from where the flow entered the 

device, and the outlet sample line was installed 3 ft downstream from where the flow exits the device. All sample lines 

were perpendicular to flow and approximately 1 inch from the 

bottom of the pipe. The bypass area-velocity flowmeter and 

sample tubing used to collect bypass stormwater were housed 

in separate pipes. Velocities were too high in the bypass pipe 

for the sampler to work properly, so the bypass sample tubing 

was placed 5 ft upstream from the flow-splitter box.

Outlet and bypass samplers

Inlet sampler

Velocity meter

Data logger

Figure 5. Automatic 

sampling equipment. 
Methods 7

The volume between subsamples was determined such 

that a minimum of five 1-L subsamples were collected for 

each event. The maximum sampler capacity was 40 1-L subsamples. For events greater than or equal to 0.2 in. of precipitation and a minimum of five 1-L subsamples, the subsamples 

were processed for all constituents (tables 1 and 2); otherwise, 

subsamples were processed for concentrations of suspended 

sediment (SS), total suspended solids (TSS), and total dissolved solids (TDS). Samples were processed according to the 

churn-splitting procedure described by Horowitz and others 

(1997).

The constituents investigated were selected on the basis 

of the performance information from the manufacturer and 

the regulated constituents that the WisDOT might want to 

control in the future (tables 1 and 2). Samples were analyzed 

at the Wisconsin State Laboratory of Hygiene (SLOH), which 

participates in the USGS Standard Reference Sample (SRS) 

program (Woodworth and Connor, 2003).

Precipitation

A tipping-bucket raingage was used for continuous 

precipitation measurement. A datalogger recorded the number 

of bucket tips (0.09 in. per tip) every 60 seconds. This gage 

was not designed to record frozen precipitation, so data during 

periods of snowfall and freezing rainfall were not used. Calibration data showed there was no need to adjust precipitation 

data. All precipitation data collected for each site are listed in 

appendix 2–3. To accurately record precipitation amounts during varying intensities, a microprocessor in the raingage used 

a built-in polynomial to correct for the intensity, which was 

based on the tipping bucket’s mechanism (Design Analysis 

Associates, 2001).

The raingage was attached to the back of the monitoring 

station. It was mounted on a 2-in.-diameter pipe raised 10 ft to 

avoid interference from nearby structures and to prevent vandalism. During two raingage calibrations, debris was cleaned 

from inside the raingage.

Table 1. Limits of detection and analytical methods for inorganic constituents analyzed in samples 

collected at the stormwater-filtration device, Madison, Wis.

[mg/L, milligrams per liter; P, phosphorus; μg/L micrograms per liter; NA, not applicable]

Constituent or characteristic Unit Limit of 

detection

Limit of 

quantification1 Method

Dissolved solids, total mg/L 50 167 2SM2540C

Suspended solids, total mg/L 2 7 3EPA 160.2

Volatile solids, total mg/L 2 7 3EPA 160.2

Suspended sediment mg/L 2 7 2ASTM D3977–97

Phosphorus, dissolved mg/L as P .005 .016 3EPA 365.1

Phosphorus, total mg/L as P .005 .016 3EPA 365.1

Chemical oxygen demand, total mg/L 14 28 3EPA Method 410.4

Chemical oxygen demand, dissolved mg/L 14 28 3EPA Method 410.4

Chloride, dissolved mg/L .6 2 2,1SM4500CL

Calcium, total recoverable mg/L .02 .07 2EPA 200.7

Magnesium, total recoverable mg/L .03 .7 2EPA 200.7

Zinc, dissolved μg/L 16 50 2EPA 200.9

Zinc, total recoverable μg/L 16 50 2,1EPA 200.9

Copper, dissolved μg/L 1 3 2SM3113B

Copper, total recoverable μg/L 1 3 2SM3113B

Wet-sieve of sediment NA NA NA 4Burton

Coulter counter of sediment NA NA NA 4Burton

Laser diffraction of sediment NA NA NA 4Burton

Microfiltration of sediment NA NA NA 4Burton

1

 Limit of quantification is the low standard in the calibration curve.

2

 American Public Health Association and others, 1989; SM (Standard Methods).

3

 U.S. Environmental Protection Agency, 1986.

4

 Burton and Pitt, 2002. 
8 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

Flow Monitoring

Area-velocity flowmeters were installed that use continuous-wave Doppler technology to measure average velocity. 

The sensor transmits a continuous ultrasonic wave and then 

measures the frequency shift of returned echoes reflected by 

air bubbles or particles in the flow (Teledyne Isco, 2004). 

Three meters were installed to monitor flow in the 6-in.-diameter inlet pipe, 6-in.-diameter outlet pipe, and 15-in.-diameter 

bypass pipe. The area-velocity flowmeters at the inlet and 

outlet were installed 4 in. downstream from the sample intake 

tubes. 

Because laminar flow was necessary to produce accurate 

measurements from the area-velocity meter, an additional 3-ft 

length of pipe was attached to the inlet pipe (fig. 6). The outlet 

area-velocity flowmeter was 3 ft downstream from the device 

in a 6-in.-diameter pipe. The area-velocity meter was placed 

downstream from the external bypass weir in a 15-in.-diameter 

pipe that graded at a 29-percent slope.

A stand-alone stage pressure transducer and temperature 

probe were installed in May 2006. The transducer and probe 

were installed 2 ft in front of the SFD internal bypass weir 

(fig. 4). The recorded depth indicated the height of flow in the 

filtration bay.

Cameras were installed at five locations to identify problems with sampling equipment or to detect a change in flow 

regimen at (1) the flow-splitter box to detect bypass flows, 

(2) the inlet pipe to detect debris on the meter, (3) the pressure 

transducer and device weir to detect overflows, (4) the bypass 

pipe to detect movement of the meter, and (5) the exit manhole, where the bypass pipe and the device outlet pipe flow, to 

detect back-water flow. Digital recordings were controlled by 

an inlet stage threshold that turned the cameras on and off.

Calibration of Gage Height

Corrections were applied to stage measurements (for 

June 22, 2005; July 13, 2006; and June 11, 2007) that reflect 

differences between water-surface elevations measured manually and those measured with the area-velocity flowmeters. 

To generate two sets of elevations for comparison, the meters 

were placed in separate buckets. Water levels then were 

increased in each bucket, and measurements were made at 

various levels, representing the entire depth of the pipe. Ten to 

15 readings were taken at each meter. Results from this procedure were used to make stage corrections throughout the entire 

monitored period of record (November 2005–August 2007). 

Accuracy of the records, on average, was estimated to be 

within ± 2 percent.

Table 2. Limits of detection and analytical methods for polycyclic 

aromatic hydrocarbons analyzed in samples collected at the 

stormwater-filtration device, Madison, Wis.

[All data in micrograms per liter, determined by use of method SW8310 in 

American Public Health Association and others, 19891]

Constituent or characteristic Limit of 

detection

Limit of 

quantification2

1-Methylnaphthalene 0.064 0.2

2-Methylnaphthalene .049 .16

Fluorene .52 1.7

Acenaphthene .064 .20

Acenaphthylene .11 .34

Anthracene .031 .1

Benzo[a]anthracene .093 .30

Benzo[a]pyrene .16 .52

Benzo[b]fluoranthene .13 .41

Benzo[g,h,i]perylene .14 .44

Benzo[k]fluoranthene .12 .38

Chrysene .027 .09

Dibenzo[a,h]anthracene .034 .11

Fluoranthene .11 .35

Indeno[1,2,3-cd]pyrene .093 .30

Phenanthrene .093 .30

Pyrene .11 .34

Naphthalene .042 .13

1

 American Public Health Association and others, 1989; SM (Standard 

Methods).

2

 Limit of quantification is the low standard in the calibration curve. 

Figure 6. Inlet pipe with stabilization bar. 
Methods 9

Calibration of Flow

Stormwater runoff was measured at the inlet, outlet, and 

bypass pipes of the SFD. A dye-dilution system was installed 

to calibrate flow rate at the inlet. The outlet meter was corrected using the calibrated inlet flows. It was not necessary to 

correct bypass flows because no bypass event samples were 

processed.

Inlet Flows

In October 2006, an automatic dye-dilution system was 

installed to calibrate flow. A separate gage house for sampling 

dye, fluorometer, and datalogger to record dye-dilution data 

was located adjacent to the sampling gage houses. The injection site for known dye concentrations was 20 ft upstream 

from the inlet area-velocity flowmeter (fig. 6). A dye-sampling 

tube was placed 1 in. downstream from the inlet-sampling tube 

for a uniform mixture of stormwater and dye. The mixture was 

pumped to the fluorometer to measure the concentration of 

dye fluorescence. A dye dilution occurred when a given stage 

threshold was reached at the inlet area-velocity flowmeter.

The equation used to convert dye measurements to flow 

is

Q q = ⋅C c , (1)

where

Q is flow being measured, in cubic feet,

q is injection rate, in milliliters per minute,

C is concentration of injected dye, in percent 

by volume, and

c is concentration of measure, in micrograms 

per liter.

In 2007, more than 200 sample points were recorded 

for calibration at the inlet meter from six events (April 25, 

May 15, July 3 and 26, and August 4 and 5). Comparison of 

the data points from the inlet area-velocity meter and the dyedilution flow indicated that the inlet area-velocity meter was 

reading low by an average of 18 percent (fig. 7). To correct 

the inlet flow measurements, a plot of dye-to-metered-flow 

data points was used to produce a correction equation with an 

R2=0.9825:

Inlet corrected flow = 1.5689 * (Inlet flow measured) – 0.0469

Outlet Flows

It was not possible to calibrate the outlet area-velocity 

meter owing to the short mixing zone between the flow exiting 

the cartridge bay and the outlet area-velocity meter. Because 

there was no external bypass through the filtration device for 

most events, the outlet meter could be corrected using the 

inlet-corrected event volumes.

Figure 7. Dye-dilution flow in relation to area-velocity flow at the inlet of the stormwater-filtration device. 

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1

AREA-VELOCITY FLOW, IN CUBIC FEET PER SECOND

DYE-DILUTION FLOW, IN CUBIC FEET PER SECOND

line of best fit

line of of 1:1 correspondence

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

1.1
10 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

Monitoring Complications

Bypass meter. The external bypass flow exited through a 

15-in.-diameter PVC pipe that was set at a 29-percent slope. 

The area-velocity meter was attached to a spring band and 

placed 3 ft upstream from the exit manhole. During a runoff 

event on August 25, 2005, the high velocities of runoff forced 

the meter downstream. Subsequently, screws were used to 

secure the spring band. On August 21, 2006, the probe of the 

area-velocity meter was replaced because the unit was recording negative values.

High-flow weirs. The SFD was designed with 

external and internal high-flow bypass weirs. During July–

October 2005, stormwater runoff was measured for 16 events; 

8 of the events produced external bypassing, and 4 produced 

internal bypassing. The manufacturer decided that additional 

stormwater could be passed to the filter by increasing the 

heights of both weir plates. The task of increasing the heights 

of the weir plates was completed on November 1, 2005. This 

adjustment reduced the number of bypasses to three during the 

rest of the study period.

Datalogger. Programming changes between the datalogger and the velocity meter were added that omitted data spikes 

during non-events. Communications from the area-velocity 

meter to the datalogger were managed through serial string 

translation. During non-events, data were recorded for the first 

minute of the hour. When particles were not available for the 

area-velocity meter, the meter could not correctly determine 

the velocity within that minute; therefore, the datalogger translated the velocity data as an extremely high or low data point. 

To replace the high or low data point with the last valid velocity recorded by the area-velocity meter, high and low cutoff 

thresholds were programmed into the datalogger. To validate 

removal of these high or low data points, the velocity data 

recorded by the datalogger were compared to velocity data 

recorded by the internal memory of the area-velocity meter. 

The area-velocity meter stores 15-second data for approximately 2 days, then overwrites it with new data. Programming 

changes were made in April 2006.

Dye-dilution system. From October through December 

2006, four dye-dilution events were recorded (fig. 8). These 

data were not used because the ratios of dye dilution to areavelocity flow were inconsistent. Review of the video revealed 

that the stage-flow relation was distorted by large volumes of 

stormwater that shifted the extended inlet pipe downward. To 

correct this problem, a stabilization bar was attached from the 

SFD wall to the extended inlet pipe (fig. 6). The stabilization 

bar was added on April 29, 2007. Because of the shifting of 

the inlet pipe during large-volume events, there were probably 

some errors in the data collected before the inlet pipe was stabilized. Also, during one runoff event, debris became draped 

over the meter.

Quality Control

The field-equipment blank and replicate samples were 

collected at the inlet and outlet of the SFD and analyzed for 

the same constituents as those for runoff samples (appendix 2–1). The equipment blank procedure passed deionized 

water through the sampler and processed through the churn 

to validate clean sampling procedures (Wilde, 2006). Blanks 

were collected at the beginning and midpoint of the project to 

validate clean-sampling procedures. 

Three equipment blank samples were collected to validate clean-sampling procedures: the first was collected before 

sampling began (blank 1), the second between events 18 and 

19 (blank 2) and the third between events 40 and 41 (blank 3). 

Blank 1 contained detectable concentrations of dissolved copper (DCu) and total copper (TCu), but these concentrations 

were below the limit of quantification (LOQ ) for the inlet and 

outlet. Blank 2 had detectable concentrations of total phosphorus (TP) and dissolved phosphorus (DP) from the inlet, outlet, 

and bypass, and dissolved zinc (DZn) from the outlet, but all 

concentrations were below LOQ. In blank 2, from the outlet, 

the concentration of DCu exceeded the LOQ. Quality-control 

samples collected directly from the sampler and from the jar of 

blank water were analyzed, but analyses resulted in no detects 

(appendix 2–1). Blank 3 had no detectable concentrations.

CR1000 

datalogger 

enclosure

SCUFA

fluorometer

Dye-injection site

Watercollection

pump

Housing for dyeinjection pump and 

rhodamine dye

Figure 8. Dye-dilution equipment. 
Treatment Efficiency of the Stormwater-Filtration Device 11

Replicate samples were collected during several stormwater events to quantify the variability or precision of sampling procedures. Analytical precision was a measurement of 

how much an individual measurement deviates from a mean of 

replicate measurements. The relative percent difference (RPD) 

was calculated to evaluate precision in procedures after sample 

collection.

The relative percent difference equation is

% [ RPD = − ( ) X X 1 2 / ] X ×100 , (2)

where

X1 is concentration of constituent in a sample,

X2 is concentration of a constituent in a duplicate 

sample, and

X is mean value of X1

 and X2.

Replicate samples were collected during events 1, 9, 23, 

and 44 to quantify variability in the sampling process. The 

RPD target for TSS was 30 percent or less; for recoverable 

metals, the RPD target was 25 percent or less (appendix 2–2). 

In replicates for event 9 the RPD target of 25 percent was 

exceeded for total zinc (TZn), and for event 23 the RPD target 

of 25 was exceeded for TCu. For all of the dissolved constituents, a relatively low RPD was reported, but RPDs that were 

greater than the target were reported for some of the particulate constituents.

Processing of Water-Quality Samples

A new procedure was used to improve the accuracy and 

precision of measured quantity of particulate constituents in 

samples that contained a large amount of sand-sized particles 

(>125 μm). Previous studies have shown that using a churn to 

partition samples with large quantities of sand had the potential to cause a positive bias and to lower the precision of constituent concentrations associated with particulates (Horowitz 

and others, 1997). The use of a wet-sieving process decreased 

these errors for sediment-associated constituent concentrations 

(Selbig and others, 2007). This process consisted of pouring a 

known quantity of sample through sieves of 125 μm, 250 μm, 

and 500 μm before churning the aqueous portion. Material 

collected on sieves was sent to the SLOH in individual bottles 

to be dried and weighed. Dried material from each of the 

sieves was then combined and processed for total recoverable 

metals and phosphorus. This process was used for six events, 

which were determined by stirring the samples and observing at least 2 g of material at the bottom of the bottle after 

1 minute. For samples from these six events, large amounts of 

material dropped to the bottom of the glass jar within 1 minute 

of stirring the sample. The aqueous portion of the sample that 

passed through the sieves was processed using typical USGS 

churning procedures (Horowitz and others, 1997). All concentrations of SS presented in this report include sieved material.

Sample results of the sieved mass were added back to 

the aqueous portion to determine a mean concentration for 

the event by using the following equation (Selbig and others, 

2007):

C S I = (( ) m C / / 1000 s V ) , (3)

where

CI is concentration of sieved solids, in mg/L,

Sm is mass of sieved solids after drying, in grams,

Cs is concentration of sieved solid, in mg/kg, and

V is volume of sieved water, in liters.

Particle-Size Analysis

In July 2004, the USGS Wisconsin Water Science Center 

adopted a new method for particle-size analysis. Previous 

methods required a large sample volume to provide enough 

sediment for analysis. Previous methods were not designed for 

the relatively low levels of sediment observed in stormwater 

samples. The new method requires only about a liter of sample 

and has been incorporated into this project. The new particlesize analysis uses a two-step process developed by the SLOH.

The first step was to wet sieve the sample for the particle 

sizes of 500, 250, 125, 63, and 32 μm. The material on the 

sieves was then dried and weighed. The second step was to 

separate the particles less than 32 μm into particle-size fractions of 16, 8, 4, and 2 μm. For the first 30 samples a laser 

counter was used to identify the quantity of the four smaller 

particle sizes. For later samples a Coulter counter (Beckman 

Coulter Multisizer 3 particle-size counter; Graham, 2003) 

was used to determine the quantity of smaller particles. Other 

researchers have used a Coulter counter to evaluate particle 

sizes in stormwater (Burton and Pitt, 2002). The Coulter 

counter was calibrated by microfiltering replicate samples with 

polycarbonate filters.

Treatment Efficiency of the 

Stormwater-Filtration Device

Rainfall, flow, particle-size, and water-quality data were 

important in evaluating the effectiveness of the filtration 

device. A comparison of monitored event rainfall depths and 

long-term trends in rainfall depths helped evaluate if the monitoring data were representative of rainfall patterns in Madison. 

The flow data were needed to determine the volumes of runoff 

entering and leaving the filtration device. Efficiencies of the 

SFD were evaluated by first determining if the inlet and outlet 

concentrations were significantly different. For those that were 

significantly different, the concentrations and loads were used 

to determine efficiency ratios and sum of the loads.
12 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

Precipitation Data

Precipitation data collected at the site were compared to 

National Oceanic and Atmospheric Administration (NOAA) 

data collected at the Dane County Regional Airport (DCRA). 

Precipitation data collected by both gages were comparable to 

the long-term average at DCRA (table 3). DCRA was approximately 4 mi northeast of the SFD.

The difference between the total from the USGS (onsite) precipitation data and the 2005–07 totals from the DCRA 

precipitation data was less than 20 percent. Larger differences 

generally occurred during the summer months when precipitation amounts can vary substantially over distances as small 

as 4 mi, owing to a predominance of localized convective 

events. For precipitation in 2005, the USGS precipitation data 

recorded was 5.9 in. less than the long-term average at DCRA, 

whereas in 2006 and 2007, the USGS precipitation averages 

were 5.9 and 4.6 in. higher, respectively, than the long-term 

average at DCRA.

Because flow rates can affect the performance of a 

stormwater-control practice, a project determining the treatment efficiency of a practice would benefit by sampling a mix 

of precipitation depths and intensities. Ideally, the distribution 

of precipitation depths for a project would be comparable to 

the long-term distribution of precipitation depths. It would 

not be a valid test of a treatment device if the sampled events 

favored either all small or all large precipitation depths for the 

observed area (Bachhuber and others, 2001). To assess how 

the mix of precipitation events during the project period compared to long-term precipitation patterns, the distribution of 

monitored precipitation depths from this study was compared 

to the historical distribution of precipitation depths from the 

NOAA DCRA site (1997).

Probability distributions for both data sets were constructed by use of the Weibull plotting position (Helsel and 

Hirsch, 1992). Precipitation amounts for individual events 

were computed for both data sets. Precipitation greater than or 

equal to 0.19 in. (the minimum amount recorded during this 

project) were ranked from lowest to highest. A cumulative 

probability distribution then was computed for both data sets 

by use of the formula 

P i n R R = + / 1 ( ) , (4)

where

R is precipitation event,

PR is probability of an event having a 

precipitation less than that of event,

i

R is ranking of event R, and

n is total number of events in the data set.

Although the distribution for this study tends to be a little 

higher than the historical distribution, the distribution for this 

study would still be considered very similar to the historical 

distribution (fig. 9).

Table 3. Monthly precipitation at the U.S. Geological 

Survey raingage and the National Oceanic and Atmospheric 

Administration precipitation gage at the Dane County Regional 

Airport, Madison, Wis., 2005–07. 

[Precipitation is presented in inches; USGS, U.S. Geological Survey; 

NOAA, National Oceanic and Atmospheric Administration; DCRA, Dane 

County Regional Airport; --, no data]

Month USGS 

precipitation

NOAA 

hourly 

DCRA

NOAA 

DCRA 

long-term 

average1

July 2005 2.5 3.9 3.9

August 2005 1.5 1.2 4.3

September 2005 2.1 2.0 3.1

October 2005 .6 .76 2.2

November 2005 3.2 3.4 2.3

December 2005 -- -- --

Partial year total 2005 9.9 11.3 15.8

January 2006 -- -- --

February 2006 -- -- --

March 2006 2.0 2.3 2.3

April 2006 6.2 4.2 3.4

May 2006 4.4 4.6 3.2

June 2006 3.0 2.3 4.0

July 2006 7.0 4.2 3.9

August 2006 5.7 5.4 4.3

September 2006 3.2 3.3 3.1

October 2006 2.1 2.2 2.9

November 2006 2.2 2.3 2.3

December 2006 1.2 1.7 1.7

Partial year total 2006 37.0 32.5 31.1

January 2007 -- -- --

February 2007 -- -- --

March 2007 2.5 3.4 2.3

April 2007 3.7 4.7 3.4

May 2007 1.5 1.4 3.2

June 2007 3.9 4.8 4.0

July 2007 1.2 2.7 3.9

August 2007 12.9 15.1 4.3

Partial year total 2007 25.7 32.1 21.1

1

Average for 1971 to 2000 data for Dane County Regional Airport, Wis. 
Treatment Efficiency of the Stormwater-Filtration Device 13

Stormwater-Flow Data

Volumes of stormwater measured at the outlet ideally 

were the same as volumes at the inlet because there was no 

external bypassing after the flows entered the SFD. To verify 

that the outlet area-velocity flowmeter was recording flow 

correctly, volumes from the outlet were compared to corrected 

inlet volumes (fig. 10). Only 2007 event volumes were used 

for the comparison, because the inlet meter produced some 

inconsistencies in the stage-flow relation before the inlet pipe 

was secured. On average the outlet volumes were 5 percent 

lower than the inlet volumes, so no correction was applied to 

the outlet. Flows for the outlet were not affected by a shifting 

pipe in 2005 and 2006, so the outlet flows were used to calculate event volumes.

Number of Events with Water-Quality Data

From November 5, 2005, until August 18, 2007, 51 

runoff events were monitored for water quality and water 

quantity. The precipitation for these sampled events ranged 

from 0.19 to 4.93 in. (appendix 2–3). The maximum 15- and 

60-minute precipitation intensities were 7.01 and 

3.79 in/hr, respectively. For the drainage area without 

gravel islands, the precipitation volumes ranged from 250 to 

15,210 ft3. The volume of stormwater that passed through the 

filtration system ranged from 235 to 8,210 ft3 (appendix 2–4). 

On average, 63 percent of the precipitation resulted in direct 

runoff from the site. There were two events during which 

stormwater bypassed the SFD after heights of the weirs were 

increased, but data from those events are not included in the 

report. For one event, flow at the inlet, outlet, and bypass 

were poorly sampled. For the second, only one sample was 

collected; therefore, bypassing events are not included in the 

report.

Particle-Size Distributions

Sufficient sample volume was available to do particlesize analysis for 36 events (appendix 2–8). The particle-size 

distributions (PSD) at the inlet and outlet varied for each 

event. For the inlet samples the portion of silt- and clay-sized 

particles (<63 μm) ranged from 29 to 80 percent. A similar 

range occurred for the outlet samples; the portion of silt- and 

clay-sized particles ranged from 33 to 94 percent. On the basis 

of average particle sizes for all events, slightly more silt- and 

clay-sized particles were present in the inlet water than sandsized particles (table 4). At the Milwaukee SFD site, silt- and 

clay-sized particles averaged only 20 percent of the sediment 

(U.S. Environmental Protection Agency, 2004).

CUMULATIVE FREQUENCY FOR ALL PRECIPITATION GREATER THAN 0.19 INCH

CUMULATIVE PRECIPITATION, IN INCHES

Historical

This study

0.0 0.2 0.4 0.6 0.8 1.0

5

4.5

4

3.5

3

2.5

2

1.5

1

0.5

0

Figure 9. Cumulative precipitation for the study period (2005–07) in relation to the cumulative frequency 

for all precipitation greater than 0.19 inches (1949–92) based on the National Oceanic and Atmospheric 

Administration precipitation gage at Dane County Regional Airport, Madison, Wis. 
14 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

Figure 10. Stormwater volumes at the inlet of the stormwater-filtration device corrected by dye dilution in relation 

to outlet volumes, Madison, Wis., 2007. 

Table 4. Average particle-size distribution in stormwater samples collected from the inlet and outlet of a stormwater-filtration 

device, Madison, Wis. 

[All data are in percent by mass; μm, micrometer]

Sampling 

location

Percent of particles less than each particle size

500 μm 250 μm 125 μm 63 μm 31 μm 16 μm 8 μm 4 μm 2 μm

Inlet 90 81 71 57 43 36 31 27 17

Outlet 94 87 82 68 54 47 41 35 24

Outlet flows contained a greater percentage of fine particles than the inlet flows. There was a shift to a larger percentage of the smaller particles because the larger particles were 

trapped in the SFD. The average percentage of particles less 

than 63 μm increased from 57 percent at the inlet to 68 percent 

at the outlet (table 4).

In previous studies of stormwater-control practices, 

particle-size distribution had some effect on the reduction 

of TSS and SS achieved by the device (Waschbusch, 1999; 

Horwatich and others, 2004). The average distribution of 

particles at the inlet indicated about a 20-percent reduction 

in concentrations of TSS and SS was possible by controlling 

all the particles greater than 250 microns. About a 40- and 

an 80-percent reduction might be possible by trapping all the 

particles greater than 63 and 4 μm, respectively. The average 

particle-size distribution is necessary to enter in some models, 

such as WinSLAMM, which is designed to predict the TSS 

reduction in stormwater-control devices. A PSD for each transportation facility appears to be a necessary input to determine 

device efficiency in such models.

Water-Quality Data for the Inlet and Outlet

Constituent concentrations for each stormwater event are 

listed in appendix 2 (appendixes 2–5 through 2–7). Thirtythree constituents were analyzed for the inlet and outlet 

samples. Eighteen of the constituents were individual PAH 

compounds. Samples from 31 runoff events were analyzed for 

all constituents except PAHs. Samples from 15 stormwater 

events were analyzed for PAHs.

OUTLET VOLUME, IN CUBIC FEET

CORRECTED INLET VOLUME, IN CUBIC FEET

0 100 200 300 400 500 600 700 800 900 1000

1,000

900

800

700

600

500

400

300

200

100

0
Treatment Efficiency of the Stormwater-Filtration Device 15

Non-detectable compounds composed a substantial proportion of the total PAH results. Non-detectable compounds 

were below detection limits for samples from the outlet more 

often than samples from the inlet. To calculate summary statistics for individual PAH compounds that had non-detects less 

than 80 percent, the Kaplan-Meier analysis was used (Helsel, 

2004). Non-detectable compounds that were greater than 

80 percent detection were the following 7 of the 18 PAHs: 

1-methylnaphthalene, 2-methylnaphthalene, acenaphthylene, 

acenaphthene, fluorene, dibenzo[a,h]anthracene, naphthalene; 

summary statistics were not computed for these compounds. 

To calculate the summary statistics for total PAHs, a method 

was needed to account for the non-detected concentrations. 

Methods included using the limit of detections, one-half the 

limit of detections, and zero. To be consistent with other 

USGS studies, the total PAH concentrations were calculated 

by using zero (Mahler and others, 2005).

Constituent concentrations followed a log-normal 

distribution from inlet and outlet samples. The Shapiro-Wilk 

statistic was used to test for normality (Helsel and Hirsch, 

1992). Runoff data from many urban sites around the country 

exhibited similar distributions for event-mean concentrations; these concentrations were either log-normal or could 

be approximated as log-normally distributed (Driscoll and 

others, 1990). Data sets that were log-normally distributed are 

better estimated by the median because it reduces the influence 

of a few extreme observations. The mean concentrations are 

also reported because they are used to calculate the efficiency 

ratio. These are typical reporting methods used to determine 

removal efficiencies for urban stormwater best-management 

practices (Strecker and others, 2003). The minimums, 

maximums, medians, and means for all the constituents are 

presented in table 5, and the statistics for individual PAHs are 

presented in table 6. 

Table 5. Summary statistics for selected water-quality constituents in samples collected from a stormwater-filtration device, Madison, 

Wis.

[mg/L, milligrams per liter; <, less than; ( ), number of nondetects; { }, without total suspended solids for runoff event 12 and total phosphorus for runoff 

event 8—concentrations for these events appeared to be in error; --, not computed; μg/L micrograms per liter; PAHs, polycyclic aromatic hydrocarbons]

Constituent

Number of 

samples

Minimum Maximum Median Mean Inlet Outlet Inlet Outlet Inlet Outlet Inlet

Outlet

1

Solids, suspended total, mg/L 44 <2.0

(2.0)

<2.0

(2.0)

190 50 15 12 27

{24}

15

Sediment, suspended, mg/L 50 2.0 1.9 82 62 19 9.0 23 14

1

Solids, volatile suspended, mg/L 28 <2.0

(1.0)

<2.0

(2.0)

55 23 7.0 5.0 10 6.0

1

Solids, dissolved, mg/L 43 <50

(39)

<50

(39)

55 23 <50 <50 -- --

1

Chemical oxygen demand, total, mg/L 30 <9.0

(6.0)

<9.0

(3.0)

52 58 18 16 22 20

1

Chemical oxygen demand, dissolved, mg/L 23 <9.0

(12)

<9.0

(14)

41 46 <9.0 <9.0 -- --

Phosphorus, total, mg/L 31 .019 .022 2.0 .11 .058

{.055}

.050 .12

{.057}

.054

Phosphorus, dissolved, mg/L 31 .0080 .012 .085 .064 .030 .026 .034 .028

Chloride, mg/L 38 .80 .80 39 41 1.8 2.1 4.3 5.1

1

Copper, dissolved, μg/L 31 <1.0

(15)

<1.0

(14)

4.0 5.0 1.9 1.9 2.1 2.0

1

Copper, total recoverable, μg/L 31 <2.0

(2.0)

<2.0

(2.0)

13 8.0 4.2 3.5 4.7 3.7

1

Zinc, dissolved, μg/L 29 <16

(1.0)

<16

(1.0)

22 20 8.0 11 8.6 12

1

Zinc, total recoverable, μg/L 29 <16 <16 51 54 20 16 24 23

Calcium, total recoverable, mg/L 31 2.6 2.6 8.6 7.1 4.2 4.0 4.6 4.4

Magnesium, total recoverable, mg/L 31 .70 .70 4.0 2.9 1.2 1.0 1.5 1.2

PAHs, total, μg/L 15 -- -- -- -- 54 24 64 34

1

Kaplan-Meier analysis for non-detects was used to calculate summary statistics (Helsel, 2005). 
16 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

The mean concentrations for TSS, SSC, TP, DP, TZn, and 

TCu were lower for this site than those for other parking lots 

in Wisconsin and Michigan (appendix 2–12) (U.S. Environmental Protection Agency, 2004; Horwatich and others, 2004; 

Steuer and others, 1997; Bannerman and others, 1992; Bannerman and others, 1983). For example, the mean TSS, TP, and 

TCu concentrations measured at a retail parking lot in Madison, Wis., were 91 mg/L, 0.26 mg/L, and 47 μg/L, respectively 

(Bannerman and others, 1992), compared to the results of this 

study: 20 mg/L, 0.11 mg/L, and 25 μg/L, respectively. These 

were 2 to 7 times greater than the concentrations for the study 

presented in table 5. Concentrations of PAHs measured during 

this study were much higher than those measured for retail 

parking lots in Madison, Wis. (Selbig and others, 2007), but 

the concentrations were similar to a parking lot in Marquette, 

Mich. (about 260 mi to the northeast) (Steuer and others, 

1997).

Efficiency Calculations

Two of the methods typically used by investigators to 

determine the removal efficiency of constituents by a SFD are 

the efficiency ratio and summation of loads (SOL) (National 

Cooperative Highway Research Program, 2006). The 

efficiency ratio uses event-mean concentration of contaminants sampled from the study. The SOL is used to evaluate the 

treatment efficiency on a percentage basis by comparing the 

sum of the influent and effluent loads (the product of multiplying the constituent concentration by the runoff volume) for all 

monitored events.

Each method uses data from the inlet and outlet to produce a single number that is designed to represent removal 

efficiency of the device. Unfortunately, these methods are not 

designed to evaluate the statistical differences in the data, so 

there is insufficient information generated by the methods to 

determine whether the differences in water-quality measurements for samples from the inlet and outlet are significant. 

These efficiency calculations can be supplemented with a statistical test, indicating whether the medians for nonparametric 

concentrations are statistically significant (Helsel and Hirsch, 

1992).

A paired statistical test was used to determine whether the 

constituent concentrations at the inlet were greater than those 

at the outlet. A paired statistical test was considered valid for 

this data set because concentrations at the inlet and outlet 

were paired for each event. Most of the constituents were lognormally distributed; therefore, the nonparametric one-sided 

Wilcoxon signed-rank test was applied (Helsel and Hirsch, 

Table 6. Summary statistics for individual polycyclic aromatic hydrocarbons in 15 samples collected from a stormwaterfiltration device, Madison, Wis.

[All constituents in micrograms per liter; <, less than; --, not computed]

Constituent 

Number of 

non-detects Minimum Maximum Median Mean

Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet

2-Methylnaphthalene 11 13 <0.049 <0.049 0.11 0.12 -- -- -- --

1-Methylnaphthalene 15 15 <.064 <.064 <.64 <.20 -- -- -- --

Acenaphthylene 15 15 <.11 <.11 <1.1 <.33 -- -- -- --

Acenaphthene 9 13 <.064 <.064 .17 .24 -- -- -- --

Anthracene1 1 4 .052 <.031 .97 .49 0.25 0.074 0.27 0.13

Benzo[b]fluoranthene 0 0 1.7 .91 18 11 5.2 2.7 6.4 3.8

Benzo[k]fluoranthene 0 0 .68 .36 8.2 4.8 2.4 1.1 2.9 1.6

Benzo[a]pyrene 0 0 .66 .33 12 6.4 3.6 1.1 3.7 1.9

Chrysene 0 0 1.4 .62 17 9.5 4.7 2.3 5.7 3.1

Fluoranthene 0 0 3.7 1.6 47 25 13 5.9 16 3.3

9H-Fluorene 15 15 <.52 <.52 <.52 <.52 -- -- -- --

Indeno[1,2,3-cd]pyrene 0 0 1.1 .61 13 7.6 3.8 1.9 4.3 2.6

Phenanthrene 0 0 1.4 .60 26 13 5.8 2.6 6.8 3.5

Pyrene 0 0 2.5 .99 36 19 9.2 4.0 11 5.9

Benzo[ghi]perylene 0 0 1.2 .53 14 8.4 4.1 2.0 4.8 2.8

Benzo[a]anthracene1 3 4 .17 <.093 5.0 2.5 1.5 .38 1.3 .63

Dibenzo[a,h]anthracene 14 14 <.12 <.12 .47 .47 -- -- -- --

Naphthalene 15 15 <.042 <.042 <.042 <.042 -- -- -- --

1

Kaplan-Meier analysis for non-detects was used to calculate summary statistics (Helsel, 2004). 
Treatment Efficiency of the Stormwater-Filtration Device 17

1992). A test for significance and efficiency ratios calculations 

was not done for calcium and magnesium, because these concentrations are only used in the calculation of hardness.

Concentrations of 8 of the 15 inorganic constituents 

(excluding PSD) analyzed for the SFD were significantly 

different at the 95-percent confidence level for the inlet and 

outlet samples. Concentrations of DP, DCOD, TCOD, TDS, 

DCu, and DZn were not significantly different for the inlet 

and outlet samples. All the constituents that were significantly 

different were significantly higher in samples from the inlet, 

except for chloride (Cl), which was significantly higher in the 

outlet samples, probably owing to winter practices. Eleven of 

the 18 PAH compounds also were significantly different at the 

95‐percent confidence level.

Efficiency Ratio

The efficiency ratio method of calculating efficiencies of 

a SFD weights all runoff events equally. For example, a large 

volume of flow with high constituent concentrations has the 

same weight as a small volume of flow with low constituent 

concentrations.

The efficiency ratio comparison evaluates treatment 

efficiency on a percentage basis by dividing the constituent 

concentration at the outflow by the concentration at the inflow 

and multiplying the quotient by 100. The efficiency ratio was 

calculated for each constituent (and physical property) and 

each individual runoff event.

The calculation is represented by the following equation:

Efficiency Ratio = 1 - (average outlet concentration/

 average inlet concentration). (5)

Efficiency ratios were calculated for constituents at 

the 95-percent confidence level (table 7). Efficiencies were 

calculated for runoff events after November 2005 and did not 

include bypass events. Runoff events before this date were 

affected by a lower height of the weir plates for the internal and external bypasses. Efficiency ratios for TSS and TP 

decreased significantly when the concentrations for one runoff 

event were removed from the calculations. The inlet TSS 

concentration (191 mg/L) for runoff event 12 (appendix 2–5) 

was not only 2 to 3 times higher than the closest concentrations, but it was higher than the inlet concentration of SS 

(14 mg/L). The SS concentrations were similar or higher than 

the TSS concentrations for this study. The TP inlet concentrations (2.0 mg/L) for runoff event 8 (appendix 2–6) was at 

least 20 times that of any other event. A high TP concentration for event 8 was not accompanied by an increase in DP, 

which would be expected to increase in most instances. Both 

of these concentrations were inexplicably high, so an alternate efficiency ratio was determined without the concentrations from the two events (table 7). The efficiency ratios for 

TSS, SSC, TZn, TCu, and total PAHs for the Madison SFD 

site were much lower than those for the Milwaukee SFD site 

(U.S. Environmental Protection Agency, 2004). As with the 

Milwaukee site, the efficiency ratio for Cl was negative.

Table 7. Efficiency ratios for selected constituents in samples 

from a stormwater-filtration device, Madison, Wis., 2005–07.

[Significantly different at the 95-percent level; mg/L, milligrams per liter; 

--, significance could not be determined; ( ), efficiency ratio without total 

suspended solids for runoff event 12 and total phosphorus for runoff event 8—

concentrations for these events appeared to be in error; μg/L, micrograms per 

liter; PAHs, polycyclic aromatic hydrocarbons]

Constituent

Are inlet and 

outlet pairs 

significantly 

different for 

median 

concentration?

Efficiency 

ratio1,

in percent

Total dissolved solids (mg/L)1 No --

Total suspended solids (mg/L)1 Yes 45

(37)

Suspended sediment 

concentrations (mg/L)

Yes 37

Volatile solids (mg/L) Yes 38

Dissolved phosphorus (mg/L) No --

Total phosphorus (mg/L) Yes 55

(6)

Dissolved chemical oxygen 

demand (mg/L)

No --

Total chemical oxygen 

demand (mg/L)

No --

Dissolved copper (μg/L) No --

Total copper (μg/L) Yes 22

Dissolved zinc (μg/L) No --

Total zinc (μg/L) Yes 5

Dissolved chloride (mg/L) Yes -18

Total PAHs Yes 46

1

 Efficiency was calculated when the inlet and outlet of that constituent was 

sampled for a runoff event. 

A total PAH is the sum of 18 compounds analyzed for a 

runoff event. Several of the 18 compounds were reported as 

“non-detects”; therefore, a method was needed to sum a total 

PAH. Methods used to fill in non-detects include using the 

value of the detection limit, using one-half the detection limit, 

or using a zero for the detection limit. A total PAH concentration was summed by using 11 significant compounds, and 

excluding the 7 compounds that were insignificant (greater 

than 50 percent of the values were non-detects), for all 15 

events. Substituting zero for non-detect values, the total PAH 

concentration was 955 μg/L at the inlet and 512 μg/L at the 

outlet, which resulted in an efficiency ratio of 46 percent—this 

is the lowest estimate. Substituting a non-detectable concentration for non-detect values, the total PAH concentration was 

984 μg/L at the inlet and 531 μg/L at the outlet resulting in the 

same efficiency ratio—this is the highest estimate. Because 

there is much debate on which method to use for substitutions of non-detected values, the total PAH is assumed to fall 
18 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

somewhere between these two extremes. To be conservative, 

this report relies upon the first method, which is a method used 

in previous USGS reports (Mahlar, 2004).

Summation of Loads

The SOL method of calculating efficiencies is weighted 

by the runoff volume event. This method puts emphasis on the 

load of contaminants leaving a filtration device rather than the 

concentration. The outlet volumes were used to calculate both 

the inlet and outlet loads because of the previously described 

problem with the shifting of the inlet pipe. The SOL is used 

to evaluate the treatment efficiency on a percentage basis by 

comparing the sum of the influent and effluent loads (the product of multiplying the constituent concentration by the runoff 

volume event) for all monitored events.

The equation for calculating the summation of loads is

Summation of loads = 1 - (sum of outlet loads/

 sum of inlet loads). (6)

 SOLs were calculated for constituents at the 95-percent 

confidence level for a pair test; results indicated that there was 

a difference in the median concentration (tables 7 and 8 and 

appendixes 2–9, 2–10, and 2–11). Non-detectable concentrations were substituted with zero to compute loads. As with 

the efficiency ratios, the SOL for TSS and TP decreased when 

the TSS loads for event 12 and the TP loads for event 8 were 

removed from the calculations. For event 12, the TSS concentration runoff at the inlet was about 11 times the median; 

the small volume (770 ft3) of the event resulted in a relatively 

small change in the SOL (appendix 2–4). Despite the relatively small volume for runoff event 8 (685 ft3

), removing the 

inlet TP concentration that was about 33 times the median 

significantly decreased the SOL (table 9).

Table 8. Efficiency ratios for selected polycyclic aromatic 

hydrocarbons in samples from a stormwater-filtration device, 

Madison, Wis., 2005–07.

[Significantly different at the 95-percent level; --, significance could not be 

determined; all constituents in micrograms per liter]

Constituent

Are inlet and 

outlet pairs 

significantly 

different for 

median 

concentration?

Efficiency 

ratio1,

in percent

2-Methylnaphthalene No --

1-Methylnaphthalene No --

Acenaphthylene No --

Acenaphthene No --

Anthracene Yes 56

Benzo[b]fluoranthene Yes 41

Benzo[k]fluoranthene Yes 44

Benzo[a]pyrene Yes 48

Chrysene Yes 45

Fluoranthene Yes 49

9H-Fluorene No --

Indeno[1,2,3-cd]pyrene Yes 40

Phenanthrene Yes 49

Pyrene Yes 49

Benzo[ghi]perylene Yes 42

Benzo[a]anthracene Yes 54

Dibenzo[a,h]anthracene No --

Naphthalene No --

1

 Efficiency was calculated when the inlet and outlet of that constituent was 

sampled for a runoff event. 
Treatment Efficiency of the Stormwater-Filtration Device 19

Efficiency ratios and SOL were similar for total PAHs, 

TZn, TCu, and Cl. If the events with the inexplicably high 

TSS and TP concentrations were removed from the calculations, efficiency ratios and SOLs were similar for both TSS 

and TP. Only SS and volatile suspended solids had as much as 

a 10-percent difference between the efficiency ratio and SOLs. 

Compared to the SFD site in Milwaukee (U.S. Environmental 

Protection Agency, 2004), the SOLs for TSS, SS, TZn, and 

TCu were much lower at the Madison site. As for the Milwaukee site, the SOL for Cl was negative, as it was at the Madison 

site.

The SOL for total PAHs (table 9) was computed using the 

same approach as the efficiency ratio; that is, computing the 

extreme low and extreme high estimates and assuming that the 

totals fell somewhere between these extremes. Replacement 

of non-detects with zero resulted in an inlet load of 0.087 lb 

and an outlet load of 0.045 lb. Replacement of non-detects 

with the limit of detection (table 2) resulted in an inlet load of 

0.09 lb and an outlet load of 0.047 lb. To be conservative with 

estimates for total PAH load, table 9 reports the replacement of 

non-detects with zero.

Table 9. Summation of loads of selected constituents and 

percent efficiency for a stormwater-filtration device, Madison, 

Wis., 2005–07.

[lb, pounds; SOL, summation of loads; %, percent; --, significance could not 

be determined; ( ), SOL without total suspended solids for event 12 and total 

phosphorus for event 8—concentrations for these events appeared to be in 

error; PAHs, polycyclic aromatic hydrocarbons]

Constituent

Loads at 

inlet 

(lb)

Loads at 

outlet 

(lb)

SOL1, 

(%)

Total dissolved solids -- -- --

Total suspended solids 1103 

(94)

1

70 32 

(26)

Suspended sediment 1116 173 37

Volatile solids 21 15 28

Dissolved phosphorus -- -- --

Total phosphorus .27 

(.18)

.17 36 

(6)

Chemical oxygen demand -- -- --

Dissolved chemical oxygen 

demand

-- -- --

Dissolved copper -- -- --

Total copper .016 .012 23

Dissolved zinc -- -- --

Total zinc .080 .074 8

Dissolved chloride 13 16 -21

Total PAHs 2.087 2.045 48

1

Summation of loads was calculated for only those events when both constituents were sampled. 

2

Total PAH was summed using 11 significant compounds and by replacing 

non-detect values with zero. 
20 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

Summary

This study was conducted in cooperation with the 

Wisconsin Department of Transportation (WisDOT) and 

the Wisconsin Department of Natural Resources to evaluate 

the performance of a stormwater-filtration device (SFD). A 

SFD was installed in 2003 by the Madison Gas and Electric 

Company in one of its employee parking lots in June 2003. 

This type of parking lot was chosen for the test site because 

the constituent concentrations and particle-size distributions 

were expected to be similar to those of typical park-and-ride 

lots operated by the WisDOT. The asphalt parking lot has 181 

parking stalls covering 0.91 acres.

The SFD is a concrete structure (16 ft long by 8 ft wide 

and 5.5 ft deep) that was installed underneath the parking lot, 

and contains 26 filter cartridges. Each cartridge was filled with 

a ZPG media composed of zeolite, perlite, and granular activated carbon. Together the cartridges could treat a peak flow 

of 0.87 ft3/s. When inlet flows exceeded the peak flow, the 

water bypassed the cartridges by way of an internal weir.

Fifty-one runoff events were monitored for flow and 

water quality from November 5, 2005, to August 18, 2007. 

The precipitation depths for these sampled events ranged 

from 0.19 to 4.93 in. The event average runoff coefficient 

was 63 percent. Thirty-three constituents were analyzed in 

samples from the inlet and outlet of the device. Eighteen of the 

constituents were polycyclic aromatic hydrocarbons (PAHs). 

Samples from 31 runoff events were analyzed for all the constituents except PAHs, which were analyzed in samples from 

15 events.

Treatment efficiency of the device was calculated using 

summation of loads (SOL) and the efficiency ratio methods. 

Constituents for which concentrations and loads were significantly decreased by the SFD included total suspended solids 

(TSS), suspended sediment (SS), volatile suspended solids 

(VSS), total phosphorus (TP), total copper (TCu), total zinc 

(TZn), and total PAHs. The efficiency ratios for these constituents were 45, 37, 38, 55, 22, 5, and 46 percent, respectively. 

The SOLs for these constituents were 32, 37, 28, 36, 23, 8, and 

48 percent, respectively. Both methods resulted in a negative 

efficiency ratio and SOL for chloride (Cl) (about 20 percent). 

For dissolved phosphorus, total chemical oxygen demand, 

dissolved chemical oxygen demand, dissolved zinc, total 

dissolved solids, and dissolved copper, efficiency ratios and 

SOLs were not calculated because the differences between the 

inlet and outlet concentrations were determined to be statistically insignificant.

Efficiency ratios and SOLs were similar for total PAHs, 

TZn, TCu, and Cl. When two inexplicably high inlet concentrations were removed from the calculations, the TSS 

and TP for SOLs and efficiency ratios were also similar. The 

SOLs and efficiency ratios for TP became 5 and 6 percent, 

respectively, and the ratios for TSS became 26 and 37 percent, 

respectively. Only SS and VSS had as much as a 10-percent 

difference between the efficiency ratio and SOL.

Results from this study can be used to estimate the ability of cartridge filters to reduce the loads of TSS and other 

contaminants from WisDOT park-and-ride lots. Because of 

the two inexplicably high inlet concentrations for TSS and 

TP, the efficiency ratios and SOLs without these high concentrations might better represent the expected reductions 

for these two contaminants. A different level of performance 

would be expected for the cartridge filter, at a facility with a 

different particle-size distribution. For example, the cartridge 

filter tested by WisDOT in Milwaukee achieved a higher TSS 

reduction of about 50 percent compared to about 30 percent 

for this study. For the Milwaukee SFD, the average percent 

sand in the runoff was about 80 percent, but for this study the 

average percent sand was about 40 percent.

Models can be used as tools for predicting the level 

of control to be expected for different types of stormwatercontrol devices, including a SFD. By collecting representative 

field data at a few locations, a model can be calibrated and 

verified to perform with moderate reliability for similar sites. 

Results from this study provide an opportunity to calibrate and 

verify urban watershed models capable of predicting contaminant loads from various source areas such as parking lots. 

Models can also be used to predict reduction in loads from 

different kinds of stormwater-control devices, such as a SFD. 

Constituent concentrations in samples from flows to the inlet 

of the SFD provide the data needed to verify the concentrations and runoff predicted by a model. The particle-size distributions, flows, and the reductions in constituent concentrations are needed to evaluate any reduction relation developed 

for a SFD. Unfortunately, none of the available urban runoff 

models, including WinSLAMM, include a pollutant reduction 

relation for a SFD. Results from this project could be instrumental in developing algorithms to predict the efficiency of 

a SFD based on inlet concentration, particle size, filter media 

type, and flow rates.

Acknowledgments

The authors thank David Owens and Mari Danz of the 

USGS for their tireless efforts in the collection and processing of data. Wendy Braun from the Wisconsin Department of 

Transportation is thanked for providing project support. The 

authors also thank James Montgomery of Madison Gas and 

Electric Company for providing access to the site, for support 

of the installation of the stormwater-filtration device, and for 

additional project support. Special thanks also are extended to 

Jim Bachhuber of Earth Tech, Inc., for his time assisting with 

the coordination of this project.
References Cited 21

References Cited

American Public Health Association and others, 1989, Standard methods for the examination of water and wastewater 

(17th ed.): Washington, D.C., American Public Health 

Association [variously paged].

Bachhuber, J., Corsi, S., and Bannerman, R., 2001, Test plan 

for the verification of Arkal Filtration Systems, Inc.—Pressurized stormwater filtration system, St. Mary’s Hospital, 

Green Bay, Wis.: U.S. Environmental Protection Agency, 

Office of Research and Development [variously paged].

Bannerman, R.T., Baun, K., Bohn, M., Hughes, P.E., and 

Graczyk, D.J., 1983, Evaluation of urban nonpoint source 

pollution management in Milwaukee County, Wisconsin—Volume 1 for U.S. Environmental Protection Agency, 

Region V: Wisconsin Department of Natural Resources 

Publication PB 84-114164 [variously paged].

Bannerman, R.T., Dodds, R.B., Owens, D.W, and Hughes, 

P.E., 1992, Source of pollutants in Wisconsin Stormwater—Volume 1 for U.S. Environmental Protection Agency 

Region V: Wisconsin Department of Natural Resources 

Grant number C9995007–01 [variously paged].

Burton, G.A., Jr., and Pitt, R.E., 2002, Stormwater effects 

handbook—A toolbox for watershed managers, scientists, 

and engineers: Boca Raton, Fla., Lewis Publishers, 929 p.

Corsi, S.R., Greb, S.R., Bannerman, R.T., and Pitt, R.E., 1999, 

Evaluation of the multi-chambered treatment train, a retrofit 

water-quality management practice: U.S. Geological Survey 

Open-File Report 99-270, 24 p.

Design Analysis Associates, 2001, “Smart” SDI-12 Tipping 

Bucket Rain Gauge—Model H-340SDI: WATERLOG 

Series Owner’s Manual, Version 1.1, 26 p.

Driscoll, E.D., Shelley, P.E., and Strecker, E.W., 1990, Pollutant loadings and impacts from highway stormwater runoff, 

Volume I—Design procedure: Federal Highway Administration Final Report FHWA-RD-88-006, 61 p.

Graham, M.D., and Beckman Coulter, Inc., 2003, The Coulter 

Principle—Foundation of an Industry: Journal of the Association for Laboratory Automation, v. 8, issue 6, p. 72–81.

Gray, J.R., Glysson, D.G., Turcois, L.M., and Schwarz, G.E., 

2000, Comparability of suspended-sediment concentrations 

and total suspended solids data: U.S. Geological Survey 

Water-Resources Investigations Report 00–4191, 14 p.

Helsel, D.R., 2004, Nondetects and data analysis—Statistics 

for censored environmental data: Wiley-Interscience, 268 p.

Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in 

water resources: New York, Elsevier, 522 p.

Horowitz, A.J., Hayes, T.S., Gray, J.R., and Capel, P.D., 1997, 

Selected laboratory tests of the whole-water sample splitting capabilities of the 14-liter churn and the Teflon cone 

splitters: U.S. Geological Survey Office of Water Quality 

Technical Memorandum 97.06, 28 p.

Horwatich, J.A., Corsi, R.S., and Bannerman, R.T., 2004, 

Effectiveness of a pressurized stormwater filtration system 

in Green Bay, Wisconsin—A study for the Environmental 

Technology Verification Program of the U.S. Environmental Protection Agency: U.S. Geological Survey Scientific 

Investigations Report 2004–5222, p 19.

Hunt, W.F., Jarrett, A.R., Smith, J.T., and Sharkey, L.J., 2006, 

Evaluating bioretention hydrology and nutrient removal at 

three field sites in North Carolina: ASCE Journal of Irrigation and Drainage Engineering, v. 132, no. 6, p. 600–608.

Mahler, B.J., Van Metre, P.C., Bashara, T.J., Wilson, J.T., and 

Johns, D.A., 2005, Parking lot sealcoat—An unrecognized 

source of urban polycyclic aromatic hydrocarbons: Environmental Science and Technology, v, 39, no., 15, p. 5560–

5566.

National Cooperative Highway Research Program, 2006, 

Evaluation of best management practices for highway 

runoff control: Washington, D.C., Transportation Research 

Board, NCHRP Report 565, 111 p., 2 app.

National Oceanic and Atmospheric Administration, 1997, 

National Climatic Data Center, Dane County Regional Airport Madison precipitation records, 1949-2007: Asheville, 

N.C., National Climatic Data Center, 42 p.

Pitt, R., 2003, The Source Loading and Management Model 

(SLAMM), A water quality management planning model 

for urban stormwater runoff—Chapter 4, Stormwater quality controls in WinSLAMM, accessed [July 2004] at http://

rpitt.eng.ua.edu/SLAMMDETPOND/WinSlamm/Ch4/Ch4.

html

Pitt, R., Harrison, R., Henry, C.L., Xue, D., and O’Connor, 

T., 1999, Enhanced infiltration performance of disturbed 

urban soils using compost amendments: Water Environment 

Federation, 72nd Annual Conference & Exposition, New 

Orleans, La., October 9–13, 1999.

Prince George’s County, 2002, Bioretention design specifications and criteria: St. George, Md., Prince George’s County.

Rantz, S.E., 1982, Measurement and computation of streamflow—Volume 2, Computation of discharge: U.S. Geological Survey Water-Supply Paper 2175, p. 285–631.
22 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

Selbig,W.R., Bannerman, Roger, and Bowman, George, 2007, 

Improving the accuracy of sediment-associated constituent 

concentrations in whole-stormwater samples by wet sieving: 

Journal of Environmental Quality, v. 36, no. 1, p. 226–232.

Steuer, J.J., Selbig, W.R., Hornewer, N.J., and Prey, J., 1997, 

Sources of contamination in an urban basin in Marquette, 

Michigan, and an analysis of concentrations, loads, and data 

quality: U.S. Geological Survey Water-Resources Investigations Report 97–4242, 25 p.

Strecker, E.W., Quigley, M.M., and Urbonas, Ben, 2003, A 

reassessment of the expanded EPA/ASCE National BMP 

Database, in Proceedings, National Conference on Urban 

Storm Water—Enhancing Programs at the Local Level, 

Chicago, Ill., February 17–20, 2003: U.S. Environmental 

Protection Agency, Office of Research and Development, 

EPA/625/R–03/003, p. 555–574.

Teledyne Isco, 2004, 2150 Area velocity flow module and sensor—Installation and operation guide: Teledyne Isco, Inc.

U.S. Environmental Protection Agency, 1983, Results of 

the Nationwide Urban Runoff Program, Volume 1—Final 

report: Washington, D.C.,Water Planning Division, available from the National Technical Information Service as 

PB84-185552 [variously paged]. 

U.S. Environmental Protection Agency, 1986, Test methods 

for evaluation of solid waste (3d ed.): Washington D.C., 

Office of Solid Waste and Emergency Response [variously 

paged].

U.S. Environmental Protection Agency, 2000, Storm water 

phase II final rule—An overview: U.S. Environmental Protection Agency EPA 833-F-00-001, Fact Sheet 1.0, 4 p.

U.S. Environmental Protection Agency, 2004, Environmental Technology Verification Report—Stormwater source 

area treatment device—The stormwater management 

StormFilter using ZPG filter media: 04/17/WQPC-WWF, 

EPA/600/R-04/125, 65 p., accessed [July 2004] at http://

www.nsf.org/business/water_quality_protection_center/pdf/

SMI_Riverwalk_Verification_Report_Final.pdf

U.S. Environmental Protection Agency, 2005, Environmental Technology Verification Report—Stormwater source 

area treatment device—Vortechnics, Inc., Vortechs system, 

model 1000: 05/24/WQPC-WWF, EPA 600/R–05/140, 

66 p., accessed [September 2005] at http://www.nsf.org/

business/water_quality_protection_center/pdf/Vortechs_

Verification_Report.pdf

Waschbusch, R.J., 1999, Evaluation of the effectiveness of 

urban stormwater treatment unit in Madison, Wisconsin, 

1996-97: U.S. Geological Survey Water-Resources Investigations Report 99-4195, 49 p.

Waschbusch, R.J., 2003, Data and methods of a 1999–2000 

street sweeping study on an urban freeway in Milwaukee 

County, Wisconsin: U.S. Geological Survey Open-File 

Report 03-93, 41 p. 

Wilde, F.D., ed., 2006, Collection of water samples, in

National field manual for the collection of water-quality 

data: U.S. Geological Survey Techniques of WaterResources Investigations, book 9, chap. A4 [variously 

paged].

Wisconsin Administrative Code, 2002, Wisconsin Department of Transportation, Construction site erosion control 

and storm water management procedures for department 

actions—Chap. TRANS 401 [variously paged]. 

Wisconsin Administrative Code, 2004, Wisconsin Department 

of Natural Resources—Runoff management—Chap. NR151 

[variously paged].

Woodworth, M.T., and Connor, B.F., 2003, Results of the 

U.S. Geological Survey’s analytical evaluation program 

for standard reference samples distributed in March 2003: 

U.S. Geological Survey Open-File Report 03–261, 109 p. 
Appendix 1 23

Bannerman, R.T., Baun, K., Bohn, M., Hughes, P.E., and 

Graczyk, D.J., 1983, Evaluation of urban nonpoint source 

pollution management in Milwaukee County, Wisconsin—Volume 1 for U.S. Environmental Protection Agency, 

Region V: Wisconsin Department of Natural Resources 

Publication PB 84–114164 [variously paged].

Bannerman, R.T., Dodds, R.B., Owens, D.W, and Hughes, 

P.E., 1992, Source of pollutants in Wisconsin Stormwater—Volume 1 for U.S. Environmental Protection Agency 

Region V: Wisconsin Department of Natural Resources 

Grant number C9995007–01 [variously paged].

Bannerman, R.T., Legg, A.D., and Greb, S.R., 1996, Quality 

of Wisconsin stormwater 1989–94: U.S. Geological Survey 

Open-File Report 96–458, 26 p.

Bannerman, R.T., Owens, D.W., Dodds, R.B., and Hornewer, 

N.J., 1993, Sources of pollutants in Wisconsin stormwater: 

Water Science Technology, v. 28, no. 3–5, p. 241–259.

Corsi, S.R., Greb, S.R., Bannerman, R.T., and Pitt, R.E., 1999, 

Evaluation of the multi-chambered treatment train, a retrofit 

water-quality management practice: U.S. Geological Survey 

Open-File Report 99–270, 24 p.

Horwatich, J.A., Corsi, R.S., and Bannerman, R.T., 2004, 

Effectiveness of a pressurized stormwater filtration system 

in Green Bay, Wisconsin—A study for the Environmental 

Technology Verification Program of the U.S. Environmental Protection Agency: U.S. Geological Survey Scientific 

Investigations Report 2004–5222, p 19.

House, L.B., Waschbusch, R.J., and Hughes, P.E., 1993, Water 

quality of an urban wet detention pond in Madison Wisconsin, 1987–88: U.S. Geological Survey Open-File Report 

93–172, 57 p.

Legg, A.D., Bannerman, R.T., and Panuska, J., 1996, Variation 

in the relation of rainfall to runoff from residential lawns in 

Madison, Wisconsin, July and August 1995: U.S. Geological Survey Scientific Investigations Report 96–4196, 11 p.

Owens, D.O., Jopke, P., Hall, D.W., Balousek, J., and Roa, A., 

2000, Soil erosion from two small construction sites, Dane 

County, Wisconsin: U.S. Geological Survey Fact Sheet 

FS–109–00, 4 p.

Selbig, W.R., and Bannerman, R.T., 2007, Evaluation of street 

sweeping as a stormwater-quality management tool in three 

residential basins in Madison, Wisconsin: U.S. Geological 

Survey Scientific Investigations Report 2007–5156, 103 p.

Selbig, W.R., and Bannerman, R.T., 2008, A comparison of 

runoff quantity and quality from two small basins undergoing implementation of conventional and low-impactdevelopment (LID) strategies, Cross Plains, Wisconsin, 

water years 1999–2005: U.S. Geological Survey Scientific 

Investigations Report 2008–5008, 66 p. 

Selbig, W.R., Bannerman, R.T., and Bowman, G., 2007, 

Improving the accuracy of sediment-associated by wet-sieving: Journal of Environmental Quality, v. 36, no. 1, 7 p.

Steuer, J.J., Selbig, W.R., and Hornewer, N.J., 1996, Contaminant concentration in stormwater from eight Lake Superior 

basin cities, 1993–94: U.S. Geological Survey Open-File 

Report 96–122, 16 p. 

Steuer, J.J., Selbig, W.R., Hornewer, N.J., and Prey, J., 1997, 

Sources of contamination in an urban basin in Marquette, 

Michigan, and an analysis of concentrations, loads, and data 

quality: U.S. Geological Survey Water-Resources Investigations Report 97–4242, 25 p.

U.S. Environmental Protection Agency, 1983, Results of 

the Nationwide Urban Runoff Program, Volume 1—Final 

report, Water Planning Division: Washington, D.C., 

National Technical Information Service PB84–185552 

[variously paged]. 

Walker, J.F., Graczyk, D.J., Corsi, S.R., Owens, D.W., and 

Wierl, J.A., 1995, Evaluation of nonpoint-source contamination, Wisconsin; land-use and best-management-practices 

inventory, selected streamwater-quality data, urban-watershed quality assurance and quality control, constituent loads 

in rural streams, and snowmelt-runoff analysis, water year 

1994: U.S. Geological Survey Open-File Report 95–320, 

21 p. 

Waschbusch, R.J., 1995, Stormwater-runoff data in Madison, 

Wisconsin, 1993–94: U.S. Geological Survey Open-File 

Report 95–733, 33 p. 

Waschbusch, R.J., 1999, Evaluation of the effectiveness of 

urban stormwater treatment unit in Madison, Wisconsin, 

1996–97: U.S. Geological Survey Water-Resources Investigations Report 99–4195, 49 p.

Waschbusch, R.J., 2003, Data and methods of a 1999–2000 

street sweeping study on an urban freeway in Milwaukee 

County, Wisconsin: U.S. Geological Survey Open-File 

Report 03-–93, 41 p. 

Waschbusch, R.J., Selbig, W.R, and Bannerman, R.T., 1999, 

Sources of phosphorus in stormwater and street dirt from 

two urban residential basins in Madison, Wisconsin, 1994–

95: U.S. Geological Survey Water-Resources Investigations 

Report 99–4021, 47 p. 

Appendix 1. List of References for Previous Investigations 
This page is intentionally blank.
Appendix 2. Tables of Sample Analyses 

Results 
Table 2–1. Concentrations of selected constituents in equipment-field-blank data collected from a stormwater-filtration device, Madison, Wis., 2005[LOD, limit of detection; LOQ, limit of quantification; mg/L, milligrams per liter; <, less than; --, no sample processed for event; μg/L, micrograms per liter] Constituent Unit Blank1 7/7/2005 Blank 2 7/13/2006 Blank 3 6/11/2007 

Inlet

Outlet

Bypass

Inlet

Outlet

Bypass

Inlet

Outlet

Bypass

Suspended solids, total (mg/L) mg/L <2 <2 <2 <2 <2 <2 <2 <2 <2 Suspended-sediment concentration mg/L <2 <2 <2 <2 <2 <2 <2 <2 <2 Volatile solids, total mg/L -- -- -- -- -- -- <2 <2 <2Dissolved solids, total mg/L <50 <50 <50 <50 <50 <50 <50 <50 <50 Phosphorus, dissolved mg/L <.005 <.005 <.005 .012 .011 .011 <.005 <.005 <.005 Phosphorus, total mg/L <.005 <.005 <.005 .011 .011 .01 <.005 <.005 <.005 Chemical oxygen demand, total mg/L 10 <9 <9 <9 <9 <9 <9 <9 <9 Chemical oxygen demand, dissolved mg/L -- -- -- <9 <9 <9 <9 <9 <9 Chloride, dissolved mg/L <.6 <.6 <.6 <.6 <.6 <.6 <1 <1 <1 Copper, dissolved μg/L 1.3 <1 1.0 <2 <1 <1 <2 <2 <2 Copper, total recoverable μg/L 1 1 2 <1 <1 -- <2 <2 <2 Zinc, dissolved μg/L <16 <16 <16 <1 6 <1 <1 <1 <1 Zinc, total recoverable μg/L <16 <16 <16 <3 <3 <3 <3 <3 <3 Calcium, total recoverable mg/L <.2 <.2 <.2 <.1 <.1 <.1 <.1 <.1 <.1 Magnesium, total recoverable mg/L <.2 <.2 <.2 <.1 <.1 <.1 <.1 <.1 <.1 
Table 2–2. Relative percent difference for concentrations of selected constituents in field replicate samples collected from a stormwater-filtration dMadison, Wis., 2005–07. —Continued[Target, minimum criteria for acceptance of quality-control-sample data without qualification; %, percent; Rep, replicate; RPD, relative percent difference; mg/L, milligrams per --, no sample processed for event; <, less than; μg/L, micrograms per liter]

Constituent Target (%) Site

Event 1 

11/05/2005

Event 9 

4/16/2006

Event 23 

8/23/06

Rep 1a Rep 1b RPD (%) Rep 2a Rep 2b RPD (%) Rep 3a Rep 3b RPD (%) R

Suspended 

solids, total (mg/L)

30 Inlet

Outlet

13

8

14

8

-7

0

3420

3520

-3

0

22

11

2317

-4

-43

11

Suspended sediment 

concentration (mg/L)

na Inlet

Outlet

13

7

13

7

00

5320

4520

16

0

33

9

32

9

30

11

Volatile suspended 

solids, (mg/L)

na Inlet

Outlet

----

----

----

96

10

6

-11

0

75

75

00

Suspended solids, 

dissolved (mg/L)

30 Inlet

Outlet

<50<50

<50<50

----

<50<50

<50<50

----

<50<50

<50<50

----

<5

5

Phosphorus, dissolved 

(mg/L)

30 Inlet

Outlet

.062.07

.061.064

.16

9.0

.02.012

.02.012

00

.026.031

.028.030

-7

3

Phosphorus, total (mg/L) 30 Inlet

Outlet

.089.079

.089.079

00

.058.040

.059.044

-2

-10

.052.043

.053.041

-2

5

Chemical oxygen 

demand, total (mg/L)

na Inlet

Outlet

1917

<9

15

--

13

2021

2613

-26

47

1522

2833

-60-40

45

Chemical oxygen 

demand, dissolved (mg/L)

na Inlet

Outlet

16

--

15

--

6

--

2215

<9

23

--

-42

41

<9

4320

-5

--

44

Chloride, dissolved 

(mg/L)

25 Inlet

Outlet

1.72

1.72

00

1.92.1

1.81.9

5

10

.8--

.8--

0

--

Copper, dissolved (μg/L) 25 Inlet

Outlet

1.91.8

1.81.9

5

-5

<1

1

<1

1

--

0

<2<2

<2<2

----

Copper, total recoverable 

(μg/L)

25 Inlet

Outlet

33

33

00

43

43

00

32

43

-29-40
Table 2–2. Relative percent difference for concentrations of selected constituents in field replicate samples collected from a stormwater-filtration dMadison, Wis., 2005–07. —Continued [Target, minimum criteria for acceptance of quality-control-sample data without qualification; %, percent; Rep, replicate; RPD, relative percent difference; mg/L, milligrams per --, no sample processed for event; <, less than; μg/L, micrograms per liter] Constituent Target (%) Site Event 1 11/05/2005 Event 9 4/16/2006 Event 23 8/23/06 

Rep 1a Rep 1b RPD (%) Rep 2a Rep 2b RPD (%) Rep 3a Rep 3b RPD (%) R

 Zinc, dissolved (μg/L) 25 Inlet Outlet <16 <16 <16 <16 ---- 611 611 00 710 810 -130 2

2

Zinc, total recoverable (μg/L) 25 Inlet Outlet <16 <16 <16 <16 ---- 2421 4320 -575 2418 2719 -12-5 3

3

Calcium, total recoverable (mg/L) 25 Inlet Outlet 4.2 4.3 4.2 4.2 02 4.5 3.6 8.6 3.5 -633 3.8 3.3 3.9 3.4 -3-3 Magnesium, total recoverable (mg/L) 25 Inlet Outlet 1.2.9 1.3.9 -80 1.7 1.1 2.2 1.1 -260 1.2.8 1.2.8 00 
Appendix 2 29

Table 2–3. Precipitation during sampling events from a stormwater-filtration device, Madison, Wis., 2005–07. —Continued

[mm, month; dd, day; yyyy, year; hh, hour; mm, min, minute; in., inch; in/h, inch per hour; ft-lb/acre, foot per pound per acre; ft3, cubic foot]

Sampling 

event 

number

Start date 

and time 

(mm/dd/yyyy 

hh:mm)

End date 

and time 

(mm/dd/yyyy 

hh:mm)

Precipitation 

duration 

(hh:mm)

Total 

precipitation 

(in.)

Max 

15-min 

intensity 

(in/h)

Max 

30-min 

intensity 

(in/h)

Erosivity 

index 

(hundreds 

of ft-lb/

acre/in/hr)

Precipitation 

volume 

(ft3)

Antecedent 

dry times

(dd hh:mm)

1 11/05/2005 17:27 11/05/2005 23:52 06:25 1.01 0.324 0.27 2.4 3,370 06 01:55

1 11/06/2005 01:33 11/06/2005 05:28 03:55 .23 .14 .11 .21 720 00 01:41

1 11/12/2005 16:14 11/12/2005 17:08 00:54 .09 .25 .14 .11 280 06 10:46

1 11/12/2005 21:47 11/12/2005 22:05 00:18 .07 .22 -- -- 220 00 04:39

1 11/14/2005 18:38 11/14/2005 21:16 02:38 .08 .07 .07 .05 250 01 20:33

2 11/15/2005 13:09 11/15/2005 20:23 07:14 .77 .32 .31 2.0 2,390 00 15:53

2 11/15/2005 21:25 11/16/2005 01:16 03:51 .05 .04 .02 .01 170 00 01:02

2 11/23/2005 08:58 11/23/2005 09:28 00:30 .06 .14 .13 .07 190 07 07:42

2 11/27/2005 06:58 11/27/2005 11:20 04:22 .16 .11 .07 .10 500 03 21:30

3 11/28/2005 03:09 11/28/2005 07:30 04:21 .63 .54 .43 2.3 1,940 00 15:49

3 12/23/2005 08:45 12/23/2005 12:13 03:28 .17 .11 .11 .15 530 25 01:15

3 01/01/2006 20:21 01/01/2006 22:47 02:26 .10 .07 .05 .04 310 09 08:08

3 01/02/2006 06:58 01/02/2006 14:23 07:25 .73 .29 .25 1.5 2,250 00 08:11

3 01/24/2006 09:06 01/24/2006 10:09 01:03 .10 .18 .14 .12 310 21 18:43

3 01/28/2006 05:16 01/28/2006 06:04 00:48 .08 .18 .13 .08 250 03 19:07

3 01/28/2006 09:02 01/28/2006 09:30 00:28 .05 .14 -- -- 170 00 02:58

3 01/28/2006 12:34 01/28/2006 17:22 04:48 .23 .11 .09 .17 720 00 03:04

3 01/28/2006 19:48 01/29/2006 08:42 12:54 .80 .18 .14 .95 2,470 00 02:26

3 02/03/2006 05:29 02/03/2006 06:13 00:44 .05 .11 .09 .04 170 04 20:47

3 03/06/2006 14:01 03/06/2006 16:05 02:04 .22 .25 .20 .37 690 31 07:48

4 03/08/2006 17:52 03/08/2006 22:35 04:43 .85 .44 .38 2.7 2,620 02 01:47

4 03/12/2006 21:52 03/13/2006 00:10 02:18 .34 .28 .24 .69 1,050 03 23:17

4 03/13/2006 02:35 03/13/2006 03:34 00:59 .11 .16 .12 .11 340 00 02:25

4 03/17/2006 12:07 03/17/2006 13:13 01:06 .10 .24 .18 .15 310 04 08:33

4 03/23/2006 16:00 03/23/2006 17:24 01:24 .10 .16 .12 .10 310 06 02:47

4 03/30/2006 22:42 03/31/2006 02:10 03:28 .18 .16 .12 .18 560 07 05:18

4 03/31/2006 12:52 03/31/2006 13:32 00:40 .07 .12 .12 .07 220 00 10:42

5 04/02/2006 11:02 04/02/2006 13:10 02:08 .25 .28 .20 .42 770 01 21:30

6 04/02/2006 20:32 04/02/2006 22:06 01:34 .37 .40 .36 1.1 1,140 00 07:22

6 04/02/2006 23:31 04/03/2006 05:25 05:54 .72 .24 .20 1.2 2,220 00 01:25

7 04/06/2006 22:00 04/07/2006 07:54 09:54 1.61 .88 .72 10 4,970 03 16:35

8 04/12/2006 05:06 04/12/2006 07:45 02:39 .44 .48 .36 1.3 1,360 04 21:12

8 04/13/2006 21:37 04/13/2006 21:40 00:03 .10 -- -- -- 310 01 13:52

9 04/16/2006 03:37 04/16/2006 04:29 00:52 .11 .24 .18 .17 340 02 05:57

9 04/16/2006 09:18 04/16/2006 10:22 01:04 .09 .24 .14 .11 280 00 04:49

9 04/16/2006 13:23 04/16/2006 16:40 03:17 .75 .96 .74 4.9 2,310 00 03:01
30 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

Table 2–3. Precipitation during sampling events from a stormwater-filtration device, Madison, Wis., 2005–07. —Continued

[mm, month; dd, day; yyyy, year; hh, hour; mm, min, minute; in., inch; in/h, inch per hour; ft-lb/acre, foot per pound per acre; ft3, cubic foot]

Sampling 

event 

number

Start date 

and time 

(mm/dd/yyyy 

hh:mm)

End date 

and time 

(mm/dd/yyyy 

hh:mm)

Precipitation 

duration 

(hh:mm)

Total 

precipitation 

(in.)

Max 

15-min 

intensity 

(in/h)

Max 

30-min 

intensity 

(in/h)

Erosivity 

index 

(hundreds 

of ft-lb/

acre/in/hr)

Precipitation 

volume 

(ft3)

Antecedent 

dry times

(dd hh:mm)

9 04/19/2006 04:28 04/19/2006 05:47 01:19 0.16 0.56 0.28 0.42 490 02 11:48

9 04/22/2006 01:26 04/22/2006 01:41 00:15 .09 .36 -- -- 280 02 19:39

10 04/29/2006 18:39 04/29/2006 22:22 03:43 .33 .28 .20 .76 1,020 07 16:58

10 04/29/2006 23:27 04/30/2006 09:30 10:03 1.19 .44 .36 3.6 3,670 00 01:05

11 05/01/2006 20:34 05/01/2006 21:36 01:02 .41 1.36 .78 3.0 1,270 01 11:04

11 05/09/2006 10:37 05/09/2006 12:24 01:47 .05 .07 .05 .02 170 07 13:01

12 05/09/2006 13:46 05/09/2006 17:22 03:36 .41 .29 .25 .84 1,250 00 01:22

12 05/11/2006 06:12 05/11/2006 09:18 03:06 .07 .11 .07 .04 220 01 12:50

13 05/11/2006 12:01 05/11/2006 23:12 11:11 .62 .11 .11 .56 1,920 00 02:43

13 05/12/2006 00:44 05/12/2006 03:44 03:00 .07 .07 .05 .03 220 00 01:32

13 05/13/2006 10:40 05/13/2006 11:32 00:52 .05 .11 .07 .03 170 01 06:56

13 05/13/2006 15:38 05/13/2006 16:45 01:07 .10 .14 .11 .09 310 00 04:06

13 05/15/2006 15:38 05/15/2006 15:45 00:07 .06 -- -- -- 190 01 22:53

14 05/16/2006 14:49 05/16/2006 15:42 00:53 .10 .32 .18 .15 310 00 23:04

14 05/16/2006 17:50 05/16/2006 17:59 00:09 .09 -- -- -- 280 00 02:08

15 05/17/2006 15:25 05/17/2006 16:13 00:48 .36 .83 .50 1.7 1,110 00 21:26

15 05/24/2006 18:37 05/24/2006 19:03 00:26 1.83 6.13 -- -- 5,660 07 02:24

15 05/24/2006 21:11 05/24/2006 21:37 00:26 .10 .36 -- -- 310 00 02:08

15 05/30/2006 13:26 05/30/2006 13:33 00:07 .05 -- -- -- 170 05 15:49

15 06/06/2006 05:37 06/06/2006 08:16 02:39 .14 .14 .11 .13 440 06 16:04

15 06/08/2006 10:50 06/08/2006 11:56 01:06 1.28 1.22 1.19 14 3,940 02 02:34

16 06/09/2006 23:59 06/10/2006 06:46 06:47 .69 .32 .31 1.8 2,140 01 12:03

16 06/14/2006 11:27 06/14/2006 13:03 01:36 .13 .25 .13 .13 390 04 04:41

16 06/18/2006 07:19 06/18/2006 09:39 02:20 .08 .11 .07 .05 250 03 18:16

16 06/18/2006 12:16 06/18/2006 13:11 00:55 .09 .25 .14 .11 280 00 02:37

16 06/21/2006 05:52 06/21/2006 06:49 00:57 .09 .32 .16 .12 280 02 16:41

16 06/24/2006 08:51 06/24/2006 11:02 02:11 .06 .07 .05 .03 180 03 02:02

17 06/25/2006 17:40 06/26/2006 06:16 12:36 .45 .12 .10 .38 1,390 01 06:38

18 07/11/2006 07:17 07/11/2006 16:08 08:51 1.87 .86 .76 12 5,770 15 01:01

19 07/20/2006 02:33 07/20/2006 06:59 04:26 .88 1.44 .90 7.4 2,720 08 10:25

19 07/22/2006 16:31 07/22/2006 17:51 01:20 .16 .48 .28 .39 490 02 09:32

19 07/25/2006 23:47 07/26/2006 01:08 01:21 .05 .11 .05 .02 170 03 05:56

19 07/27/2006 11:44 07/27/2006 13:42 01:58 4.05 7.01 5.23 106 12,500 01 10:36

20 08/06/2006 05:43 08/06/2006 11:08 05:25 .87 .47 .32 2.3 2,690 09 16:01

21 08/09/2006 18:42 08/09/2006 19:04 00:22 .21 .79 -- -- 640 03 07:34

22 08/17/2006 15:02 08/17/2006 17:23 02:21 .22 .61 .36 .67 670 07 19:58
Appendix 2 31

Table 2–3. Precipitation during sampling events from a stormwater-filtration device, Madison, Wis., 2005–07. —Continued

[mm, month; dd, day; yyyy, year; hh, hour; mm, min, minute; in., inch; in/h, inch per hour; ft-lb/acre, foot per pound per acre; ft3, cubic foot]

Sampling 

event 

number

Start date 

and time 

(mm/dd/yyyy 

hh:mm)

End date 

and time 

(mm/dd/yyyy 

hh:mm)

Precipitation 

duration 

(hh:mm)

Total 

precipitation 

(in.)

Max 

15-min 

intensity 

(in/h)

Max 

30-min 

intensity 

(in/h)

Erosivity 

index 

(hundreds 

of ft-lb/

acre/in/hr)

Precipitation 

volume 

(ft3)

Antecedent 

dry times

(dd hh:mm)

23 08/23/2006 22:26 08/23/2006 23:55 01:29 0.34 0.72 0.58 1.7 1,060 06 05:03

23 08/24/2006 01:22 08/24/2006 06:53 05:31 1.17 1.82 1.14 13 3,610 00 01:27

24 08/24/2006 13:00 08/24/2006 15:00 02:00 1.22 2.28 1.28 16 3,760 00 06:07

24 08/25/2006 05:11 08/25/2006 06:51 01:40 .26 .32 .28 .61 800 00 14:11

24 08/25/2006 08:23 08/25/2006 08:47 00:24 .07 .20 -- -- 220 00 01:32

25 08/25/2006 10:53 08/25/2006 11:09 00:16 .86 3.40 -- -- 2,650 00 02:06

25 08/25/2006 13:27 08/25/2006 13:40 00:13 .28 -- -- -- 860 00 02:18

25 08/26/2006 01:22 08/26/2006 01:30 00:08 .10 -- -- -- 310 00 11:42

25 08/28/2006 13:59 08/28/2006 16:30 02:31 .07 .08 .06 .04 220 02 12:29

26 09/03/2006 18:29 09/03/2006 21:21 02:52 .36 .28 .20 .61 1,110 06 01:59

26 09/04/2006 05:31 09/04/2006 08:20 02:49 .23 .40 .22 .43 710 00 08:10

26 09/10/2006 14:41 09/10/2006 23:30 08:49 .38 .16 .12 .38 1,170 06 06:21

26 09/11/2006 11:30 09/11/2006 11:57 00:27 .07 .20 -- -- 220 00 12:00

26 09/11/2006 15:20 09/11/2006 20:07 04:47 .38 .60 .36 1.2 1,170 00 03:23

26 09/12/2006 02:10 09/12/2006 06:02 03:52 .53 .40 .28 1.3 1,640 00 06:03

26 09/12/2006 09:37 09/12/2006 11:38 02:01 .17 .24 .20 .29 520 00 03:35

26 09/12/2006 13:30 09/12/2006 17:22 03:52 .69 1.04 .86 5.3 2,130 00 01:52

26 09/21/2006 21:39 09/21/2006 22:50 01:11 .06 .08 .06 .03 190 09 04:17

26 09/22/2006 05:16 09/22/2006 06:48 01:32 .11 .16 .12 .11 340 00 06:26

26 09/23/2006 14:17 09/23/2006 16:45 02:28 .17 .20 .16 .23 520 01 07:29

27 10/04/2006 05:36 10/04/2006 07:26 01:50 .24 .52 .34 .76 740 10 12:51

27 10/04/2006 08:43 10/04/2006 10:03 01:20 .09 .20 .10 .08 280 00 01:17

27 10/10/2006 19:31 10/11/2006 00:24 04:53 .21 .12 .10 .18 650 06 09:28

28 10/16/2006 22:58 10/17/2006 07:13 08:15 .75 .28 .22 1.4 2,310 05 22:34

28 10/18/2006 14:36 10/18/2006 16:02 01:26 .07 .08 .08 .05 220 01 07:23

28 10/18/2006 17:11 10/18/2006 18:20 01:09 .07 .16 .12 .07 220 00 01:09

29 10/21/2006 12:30 10/21/2006 14:25 01:55 .08 .12 .06 .04 250 02 18:10

29 10/21/2006 15:32 10/22/2006 01:49 10:17 .50 .12 .12 .51 1,540 00 01:07

29 10/26/2006 17:11 10/26/2006 18:59 01:48 .06 .08 .04 .02 190 04 15:22

30 11/10/2006 12:01 11/10/2006 14:27 02:26 .55 .36 .32 1.5 1,700 14 17:02

30 11/12/2006 11:31 11/12/2006 18:46 07:15 .44 .16 .14 .52 1,360 01 21:04

30 11/26/2006 20:12 11/26/2006 20:55 00:43 .08 .20 .12 .08 250 14 01:26

31 11/26/2006 22:21 11/27/2006 01:36 03:15 .21 .20 .14 .25 650 00 01:26

32 11/27/2006 19:43 11/28/2006 04:00 08:17 .76 .32 .24 1.5 2,340 00 18:07

32 11/29/2006 02:52 11/29/2006 04:39 01:47 .10 .16 .12 .10 310 00 22:52

32 11/29/2006 18:04 11/29/2006 20:03 01:59 .06 .08 .04 .02 190 00 13:25
32 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

Table 2–3. Precipitation during sampling events from a stormwater-filtration device, Madison, Wis., 2005–07. —Continued

[mm, month; dd, day; yyyy, year; hh, hour; mm, min, minute; in., inch; in/h, inch per hour; ft-lb/acre, foot per pound per acre; ft3, cubic foot]

Sampling 

event 

number

Start date 

and time 

(mm/dd/yyyy 

hh:mm)

End date 

and time 

(mm/dd/yyyy 

hh:mm)

Precipitation 

duration 

(hh:mm)

Total 

precipitation 

(in.)

Max 

15-min 

intensity 

(in/h)

Max 

30-min 

intensity 

(in/h)

Erosivity 

index 

(hundreds 

of ft-lb/

acre/in/hr)

Precipitation 

volume 

(ft3)

Antecedent 

dry times

(dd hh:mm)

32 12/20/2006 19:45 12/21/2006 03:39 07:54 0.23 0.08 0.08 0.16 710 20 23:42

33 12/21/2006 06:26 12/21/2006 13:52 07:26 .47 .24 .20 .79 1,450 00 02:47

34 12/22/2006 12:54 12/22/2006 15:39 02:45 .23 .36 .28 .54 710 00 23:02

34 12/31/2006 07:12 12/31/2006 10:24 03:12 .23 .28 .24 .47 710 08 15:33

34 01/26/2007 13:45 01/26/2007 14:44 00:59 .14 .28 .20 .24 430 26 03:21

34 02/25/2007 06:09 02/25/2007 15:46 09:37 .46 .16 .12 .47 1,420 29 15:25

34 02/26/2007 14:04 02/26/2007 16:04 02:00 .10 .08 .08 .07 310 00 22:18

34 03/01/2007 10:11 03/01/2007 14:34 04:23 .31 .40 .30 .78 960 02 18:07

34 03/09/2007 15:02 03/09/2007 18:38 03:36 .20 .12 .10 .17 620 08 00:28

34 03/14/2007 16:38 03/14/2007 18:37 01:59 .06 .08 .04 .02 190 04 22:00

34 03/21/2007 03:16 03/21/2007 05:45 02:29 .11 .20 .14 .13 340 06 08:39

34 03/21/2007 08:32 03/21/2007 10:33 02:01 .07 .12 .08 .05 220 00 02:47

34 03/21/2007 17:39 03/21/2007 18:37 00:58 .12 .24 .14 .16 370 00 07:06

34 03/22/2007 01:24 03/22/2007 03:14 01:50 .54 1.16 .82 4.1 1,670 00 06:47

34 03/28/2007 12:36 03/28/2007 14:40 02:04 .09 .16 .10 .08 280 06 09:22

35 03/31/2007 08:31 03/31/2007 09:14 00:43 .09 .28 .16 .12 280 02 17:51

35 03/31/2007 12:10 03/31/2007 14:10 02:00 .35 .64 .34 1.1 1,080 00 02:56

35 03/31/2007 20:37 03/31/2007 22:48 02:11 .60 .68 .54 2.9 1,850 00 06:27

36 04/03/2007 00:03 04/03/2007 07:31 07:28 1.58 1.04 .60 8.2 4,880 02 01:15

36 04/11/2007 00:03 04/11/2007 06:50 06:47 .20 .08 .08 .14 620 07 16:32

36 04/12/2007 11:20 04/12/2007 14:38 03:18 .18 .12 .08 .13 560 01 04:30

36 04/22/2007 20:07 04/22/2007 20:30 00:23 .08 .28 -- -- 250 10 05:29

37 04/23/2007 00:25 04/23/2007 05:48 05:23 .49 .40 .32 1.4 1,510 00 03:55

38 04/24/2007 13:23 04/24/2007 23:18 09:55 .35 .16 .12 .35 1,080 01 07:35

38 04/25/2007 00:21 04/25/2007 04:43 04:22 .27 .12 .10 .23 830 00 01:03

38 04/25/2007 20:20 04/25/2007 21:13 00:53 .06 .08 .06 .03 190 00 15:37

38 04/25/2007 23:19 04/26/2007 00:59 01:40 .06 .08 .06 .03 190 00 02:06

39 04/26/2007 08:57 04/26/2007 12:43 03:46 .32 .16 .14 .38 990 00 07:58

39 04/30/2007 20:37 04/30/2007 20:56 00:19 .08 .28 -- -- 250 04 07:54

39 05/13/2007 05:41 05/13/2007 09:50 04:09 .32 .20 .14 .38 990 12 08:45

40 05/15/2007 12:23 05/15/2007 16:06 03:43 .59 .56 .48 2.4 1,820 02 02:33

40 05/16/2007 16:56 05/16/2007 17:09 00:13 .08 -- -- -- 250 01 00:50

41 05/24/2007 16:38 05/24/2007 18:24 01:46 .49 .84 .70 3.2 1,510 07 23:29

41 05/26/2007 14:41 05/26/2007 15:09 00:28 .06 .20 -- -- 190 01 20:17

41 06/01/2007 16:44 06/01/2007 17:30 00:46 .20 .64 .38 .71 620 06 01:35

41 06/02/2007 06:36 06/02/2007 08:13 01:37 .23 .40 .28 .55 710 00 13:06
Appendix 2 33

Table 2–3. Precipitation during sampling events from a stormwater-filtration device, Madison, Wis., 2005–07. —Continued

[mm, month; dd, day; yyyy, year; hh, hour; mm, min, minute; in., inch; in/h, inch per hour; ft-lb/acre, foot per pound per acre; ft3, cubic foot]

Sampling 

event 

number

Start date 

and time 

(mm/dd/yyyy 

hh:mm)

End date 

and time 

(mm/dd/yyyy 

hh:mm)

Precipitation 

duration 

(hh:mm)

Total 

precipitation 

(in.)

Max 

15-min 

intensity 

(in/h)

Max 

30-min 

intensity 

(in/h)

Erosivity 

index 

(hundreds 

of ft-lb/

acre/in/hr)

Precipitation 

volume 

(ft3)

Antecedent 

dry times

(dd hh:mm)

41 06/03/2007 16:56 06/03/2007 19:42 02:46 0.70 1.12 0.66 4.3 2,160 01 08:43

41 06/03/2007 20:55 06/03/2007 22:50 01:55 .36 .56 .36 1.1 1,110 00 01:13

41 06/04/2007 06:00 06/04/2007 07:48 01:48 .27 .28 .20 .46 830 00 07:10

41 06/04/2007 08:56 06/04/2007 09:56 01:00 .14 .48 .26 .32 430 00 01:08

41 06/06/2007 15:02 06/06/2007 17:12 02:10 .06 .08 .04 .02 190 02 05:06

41 06/11/2007 09:10 06/11/2007 09:49 00:39 1.21 2.08 2.02 25 3,730 04 15:58

41 06/18/2007 15:46 06/18/2007 16:14 00:28 .09 .24 -- -- 280 07 05:57

41 06/18/2007 18:44 06/18/2007 19:02 00:18 .11 .40 -- -- 340 00 02:30

41 06/21/2007 16:31 06/21/2007 17:16 00:45 .06 .20 .10 .06 190 02 21:29

42 06/21/2007 18:23 06/21/2007 22:53 04:30 .43 .56 .30 1.1 1,330 00 01:07

43 07/03/2007 20:12 07/03/2007 23:31 03:19 .47 .32 .28 1.1 1,450 11 21:19

44 07/26/2007 10:20 07/26/2007 10:28 00:08 .12 -- -- -- 370 22 10:49

44 07/26/2007 22:57 07/27/2007 01:20 02:23 .53 .68 .56 2.6 1,640 00 12:29

44 07/27/2007 07:07 07/27/2007 07:20 00:13 .06 -- -- -- 190 00 05:47

45 08/04/2007 17:01 08/04/2007 19:52 02:51 .47 .52 .44 1.8 1,450 08 09:41

45 08/04/2007 21:05 08/05/2007 05:10 08:05 1.31 .88 .68 7.6 4,040 00 01:13

46 08/06/2007 21:58 08/07/2007 05:55 07:57 .60 .20 .12 .17 1,850 01 16:48

47 08/09/2007 04:09 08/09/2007 05:54 01:45 .86 1.28 .96 7.5 2,650 01 22:14

48 08/12/2007 00:58 08/12/2007 02:25 01:27 .68 2.04 1.20 8.0 2,100 02 19:04

49 08/14/2007 02:31 08/14/2007 05:09 02:38 .56 .44 .40 1.7 1,710 02 00:06

50 08/15/2007 07:42 08/15/2007 12:58 05:16 .35 .24 .20 .26 1,080 01 02:33

51 08/18/2007 11:34 08/19/2007 12:16 00:42 4.93 1.96 1.64 68 15,210 02 22:36

51 08/22/2007 01:29 08/22/2007 03:47 02:18 .28 .47 .27 .64 860 02 13:13

51 08/22/2007 15:55 08/22/2007 16:32 00:37 .15 .33 .24 .32 480 00 12:08

51 08/22/2007 18:31 08/22/2007 21:19 02:48 .40 .47 .36 1.2 1,220 00 01:59

51 08/23/2007 04:29 08/23/2007 05:11 00:42 .07 .14 .13 .08 220 00 07:10

51 08/23/2007 07:02 08/23/2007 08:38 01:36 .34 .40 .38 1.1 1,060 00 01:51

51 08/23/2007 17:34 08/23/2007 17:43 00:09 .05 -- -- -- 170 00 08:56

51 08/24/2007 02:49 08/24/2007 04:22 01:33 .61 1.09 .94 5.3 1,870 00 09:06

51 08/24/2007 16:15 08/24/2007 16:53 00:38 .73 1.87 1.37 9.8 2,250 00 11:53

51 08/27/2007 08:57 08/27/2007 11:41 02:44 .50 .47 .32 1.4 1,560 02 16:04
34 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

Table 2–4. Outlet flow volumes, percent runoff, and peak discharge for sampled events at a stormwater-filtration 

device, Madison, Wis., 2005–07. —Continued 

[mm, month; dd, day; yyyy, year; hh, hour; mm, minute; in., inch; ft3, cubic foot; ft3/s, cubic foot per second]

Sampling 

event 

number

Start date 

and time 

(mm/dd/yyyy 

hh:mm)

End date 

and time 

(mm/dd/yyyy 

hh:mm)

Total 

precipitation 

(in.)

Volume 

(ft3)

Percent 

runoff

Peak 

discharge 

(ft3/s)

1 11/05/2005 17:40 11/06/2005 00:39 1.01 2,015 60 0.42

2 11/15/2005 13:38 11/15/2005 20:51 .77 1,640 64 .51

3 11/28/2005 03:18 11/28/2005 08:09 .63 1,165 55 .70

4 03/08/2006 18:08 03/08/2006 22:58 .85 2,240 79 .09

5 04/02/2006 11:19 04/02/2006 13:36 .25 380 46 .49

6 04/02/2006 20:45 04/03/2006 06:15 1.09 2,555 70 .88

7 04/06/2006 10:22 04/07/2006 08:56 1.61 3,930 73 .49

8 04/12/2006 05:36 04/12/2006 07:48 .44 685 46 .84

9 04/16/2006 04:17 04/16/2006 17:10 .95 2,125 67 .10

10 04/29/2006 18:28 04/29/2006 23:41 .33 630 57 .99

11 05/01/2006 21:09 05/01/2006 22:35 .41 1,045 76 .42

12 05/09/2006 14:26 05/09/2006 17:29 .41 770 57 .07

13 05/11/2006 13:32 05/12/2006 06:38 .62 1,840 89 .11

14 05/16/2006 15:23 05/16/2006 18:52 .19 335 53 .77

15 05/17/2006 15:30 05/17/2006 17:01 .36 845 70 .51

16 06/10/2006 00:58 06/10/2006 07:23 .69 985 43 .67

17 06/25/2006 17:57 06/26/2006 09:37 .45 1,600 106 .85

18 07/11/2006 08:48 07/11/2006 15:39 1.87 6,040 97 .80

19 07/20/2006 02:48 07/20/2006 07:44 .88 1,850 63 .60

20 08/06/2006 07:21 08/06/2006 11:29 .87 1,020 35 .68

21 08/09/2006 18:49 08/09/2006 19:19 .21 240 35 .71

22 08/17/2006 16:42 08/17/2006 17:23 .22 275 38 .86

23 08/23/2006 22:50 08/24/2006 07:47 1.51 2,680 53 .85

24 08/24/2006 13:11 08/24/2006 15:24 1.22 1,995 49 1.05

25 08/25/2006 10:57 08/25/2006 13:54 1.14 1,765 46 .07

26 09/03/2006 18:38 09/04/2006 08:58 .59 475 24 .73

27 10/04/2006 06:11 10/04/2006 10:56 .33 620 56 .45

28 10/16/2006 23:28 10/17/2006 07:32 .75 2,110 84 .06

29 10/21/2006 13:08 10/22/2006 01:48 .58 1,020 53 .59

30 11/10/2006 12:28 11/10/2006 14:54 .55 590 32 .08

31 11/26/2006 23:12 11/27/2006 02:05 .21 300 43 .71

32 11/27/2006 20:18 11/28/2006 08:19 .76 2,340 92 .49

33 12/21/2006 07:50 12/21/2006 13:43 .47 1,165 74 .71

34 12/22/2006 14:00 12/22/2006 15:34 .23 615 80 .79

35 03/31/2007 08:46 03/31/2007 23:20 1.04 2,585 74 .87
Appendix 2 35

Table 2–4. Outlet flow volumes, percent runoff, and peak discharge for sampled events at a stormwater-filtration 

device, Madison, Wis., 2005–07. —Continued 

[mm, month; dd, day; yyyy, year; hh, hour; mm, minute; in., inch; ft3, cubic foot; ft3/s, cubic foot per second]

Sampling 

event 

number

Start date 

and time 

(mm/dd/yyyy 

hh:mm)

End date 

and time 

(mm/dd/yyyy 

hh:mm)

Total 

precipitation 

(in.)

Volume 

(ft3)

Percent 

runoff

Peak 

discharge 

(ft3/s)

36 04/03/2007 00:13 04/03/2007 07:51 1.58 4,085 77 0.67

37 04/23/2007 00:54 04/23/2007 07:10 .49 1,035 63 .05

38 04/24/2007 17:27 04/24/2007 19:44 .35 235 20 .08

39 04/26/2007 09:37 04/26/2007 13:05 .32 665 62 .66

40 05/15/2007 12:39 05/15/2007 17:49 .59 1,235 63 .73

41 05/24/2007 16:43 05/24/2007 18:47 .49 830 51 .69

42 06/21/2007 19:01 06/21/2007 23:09 .43 560 39 .39

43 07/03/2007 20:54 07/03/2007 23:33 .47 590 37 .68

44 07/26/2007 10:28 07/27/2007 01:43 .65 1,185 55 .84

45 08/04/2007 17:30 08/05/2007 07:44 1.78 4,070 68 .76

46 08/06/2007 22:35 08/07/2007 06:33 .60 1,805 90 .92

47 08/09/2007 03:13 08/09/2007 07:14 .86 2,755 96 .81

48 08/12/2007 01:04 08/12/2007 02:48 .68 840 37 .88

49 08/14/2007 02:43 08/14/2007 07:03 .56 1,980 107 .10

50 08/15/2007 08:15 08/15/2007 14:32 .35 690 59 1.01

51 08/18/2007 14:21 08/19/2007 13:01 4.93 8,210 50 42
36 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

Table 2–5. Concentrations of suspended solids, suspended sediment, volatile solids, and dissolved solids in stormwater 

samples collected from a stormwater-filtration device, Madison, Wis., 2005–07. —Continued 

[All data are in milligrams per liter; --, no sample processed for event; <, less than]

Sampling 

event 

number

Suspended solids, total Suspended sediment Solids, volatile Solids, dissolved 

Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet 

1 14 8 22 7 -- -- <50 <50

2 10 7 18.2 6 -- -- <50 <50

3 42 27 53 26 -- -- 94 96

4 37 45 41 47 -- -- 58 80

5 34 13 34 14 -- -- 66 82

6 13 13 15 12 -- -- <50 <50

7 68 45 75 45 15 11 <50 <50

8 26 26 35 25 8 7 <50 <50

9 35 20 45 20 10 6 <50 <50

10 14 12 14 12 6 5 <50 <50

11 42 25 46 25 13 8 <50 <50

12 191 3 14 3 19 2 <50 <50

13 5 2 6 2 4 <2 <50 <50

14 80 12 82 12 -- -- <50 <50

15 102 34 77 30 55 15 -- --

16 13 8 21 7 5 3 <50 <50

17 14 8 22 7 5 3 <50 <50

18 8 6 14 5 3 2 <50 <50

19 24 19 31 15 8 6 <50 <50

20 8 4 7 3 3 <2 <50 <50

21 41 33 42 33 -- -- <50 50

22 17 16 17 14 -- -- <50 <50

23 23 17 32 9 7 5 <50 <50

24 20 7 19 6 6 -- <50 <50

25 15 16 12 11 8 5 <50 <50

26 <2 4 9 4 -- -- <100 <50

27 26 24 26 23 10 8 <50 <50

28 5 5 4 5 3 2 <50 <50

29 <2 <2 2 1.9 -- -- <50 <50

30 11 7 36 6 -- -- <50 <50

31 8 4 8 4 -- -- <50 <50

32 6 5 6 4 3 2 <50 <50

33 20 15 20 13 8 6 52 56

34 40 38 38 38 17 18 <50 <50

35 66 50 76 62 16 23 <50 <50

36 15 14 22 16 5 4 <50 <50
Appendix 2 37

Table 2–5. Concentrations of suspended solids, suspended sediment, volatile solids, and dissolved solids in stormwater 

samples collected from a stormwater-filtration device, Madison, Wis., 2005–07. —Continued 

[All data are in milligrams per liter; --, no sample processed for event; <, less than]

Sampling 

event 

number

Suspended solids, total Suspended sediment Solids, volatile Solids, dissolved 

Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet 

37 18 22 19 23 8 6 <50 <50

38 4 <2 4 3 <2 <2 <50 <50

39 3 2 4 3 -- -- <50 <50

40 18 12 18 10 7 4 <50 <50

41 40 23 44 26 14 8 <50 <50

42 -- -- -- -- -- -- -- --

43 10 5 10 5 4 2 <50 <50

44 15 13 12 10 7 5 <50 52

45 6 7 7 5 7 5 <50 <50

46 -- -- 9 5 -- -- -- --

47 -- -- 5 5 -- -- -- --

48 -- -- 13 9 -- -- -- --

49 -- -- 7 7 -- -- -- --

50 -- -- 5 3 -- -- -- --

51 -- -- 5 7 -- -- -- --
Table 2–6. Concentrations of selected constituents and physical properties in stormwater samples collected from a stormwater-filtration device, M2005–07. —Continued [mg/L, milligrams per liter; μg/L, micrograms per liter; <, less than; --, no sample processed for event] Sampling event number Chemical oxygen demand, total (mg/L) Phosphorus, total (mg/L) Phosphorus, dissolved (mg/L) Chloride, dissolved (mg/L) Copper, dissolved (μg/L) Copper, total recoverable (μg/L) Zinc, dissolved (μg/L) Zinc, total recoverable (μg/L) 

re

Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inl

1 <9 15 0.09 0.08 0.061 0.06 1.7 2 1.8 1.9 3.0 3.0 <16 <16 <16 <16 42 22 16 .08 .07 .05 .04 2.1 2.6 <1.0 <1.0 2 3 -- -- 18 18 33 -- -- -- -- -- -- 39 41 -- -- -- -- -- -- -- -- -4 -- -- -- -- -- -- 17 29 -- -- -- -- -- -- -- -- -5 -- -- -- -- -- -- 18 24 -- -- -- -- -- -- -- -- -6 8.8 43.4 .03 .03 .09 .02 3.8 3.9 1.9 1.7 4 3 -- -- 17 18 37 52 29 .09 .07 .02 .02 2.5 2.3 1.8 1.6 7 6 8 10 44 37 88 24 22 2.0 .05 .02 .02 4.3 4.6 2.7 2.4 5 4 6 11 23 25 59 26 13 .06 .04 .02 .01 1.8 1.9 <1.0 1.0 4 3 6 11 43 20 8

10 13 16 .05 .04 .02 .02 1.5 2.3 <1.0 <1.0 2 2 8 14 18 22 4

11 <9.0 17 .02 .05 .07 .02 1.3 1.3 <1.0 <1.0 3 2 6 9 25 22 4

12 24 16 .06 .04 .03 .03 1.8 2.2 2.5 2.6 4 4 8 11 19 14 413 <9.0 14 .06 .04 .04 .03 -- 1.9 4.0 2.3 3 3 12 13 13 15 314 -- -- -- -- -- -- 4.1 4.5 -- -- -- -- -- -- -- -- -15 48 36 .11 .09 .04 .03 1.9 -- 2.1 2.0 7 5 8 9 37 31 516 22 14 .06 .07 .04 .05 1.4 1.6 3.0 3.0 4 4 6 9 17 19 417 13 12 .05 .06 .03 .02 1.3 1.4 1.9 2.2 8 3 6 11 20 16 418 <9.0 <9.0 .03 .03 .02 .02 1.0 1.0 3.7 2.5 6 5 8 8 14 13 219 32 15 .08 .07 .05 .05 1.1 1.2 2.6 2.5 13 5 8 9 33 21 420 10 13 .04 .05 .03 .04 1.1 1.3 <2.0 <2.0 3 3 9 9 16 15 321 -- -- -- -- -- -- 2.1 2.5 -- -- -- -- -- -- -- -- -22 -- -- -- -- -- -- 1.1 1.7 -- -- -- -- -- -- -- -- -23 28 33 .05 .04 .03 .03 .80 -- <2.0 <2.0 4 3 8 10 27 19 324 15 -- .03 .03 .02 .02 .80 .90 <2.0 <2.0 3 2 9 9 20 15 3
Table 2–6. Concentrations of selected constituents and physical properties in stormwater samples collected from a stormwater-filtration device, M2005–07. —Continued [mg/L, milligrams per liter; μg/L, micrograms per liter; <, less than; --, no sample processed for event] 

Sampling 

event 

number

Chemical 

oxygen 

demand, 

total 

(mg/L)

Phosphorus, 

total 

(mg/L)

Phosphorus, 

dissolved 

(mg/L)

Chloride, 

dissolved 

(mg/L)

Copper, 

dissolved 

(μg/L)

Copper, 

total 

recoverable 

(μg/L)

Zinc, 

dissolved 

(μg/L)

Zinc, 

total 

recoverable 

(μg/L)

re

Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inl

25 13 19 0.02 0.02 0.01 <0.005 0.80 0.90 <2.0 <2.0 3 3 11 11 18 20 226 -- -- -- -- -- -- -- 2.0 -- -- -- -- -- -- -- -- -27 41 36 .10 .08 .06 .05 1.4 1.7 2.0 3.0 7.0 5 9 14 33 30 528 <9.0 <9.0 .04 .04 .03 .03 .80 .80 <2.0 <2.0 <2.0 <2.0 4.0 8.0 10 14 229 -- -- -- -- -- -- .90 .90 -- -- -- -- -- -- -- -- -30 -- -- -- -- -- -- 1.2 1.1 -- -- -- -- -- -- -- -- -32 24 14 .02 .03 .02 .01 .90 1.1 <2.0 <2.0 <2.0 <2.0 8 13 14 17 333 18 16 .05 .04 .02 .02 20 18 <2.0 <2.0 5.0 4.0 10 16 31 30 534 -- -- -- -- -- -- 8.8 10 -- -- -- -- -- -- -- -- -35 46 34 .08 .08 .02 .02 2.9 4.3 <2.0 <2.0 8 7 10 14 51 54 836 12 13 .03 .03 .01 .01 1.9 2.2 <2.0 <2.0 3 2 7 10 19 22 337 15 13 .05 .05 .02 .03 -- 3.4 <2.0 <2.0 4 4 6 11 22 29 438 <9.0 <9.0 .02 .02 .02 .02 2.3 2.7 <2.0 <2.0 2 3 5 13 11 19 440 26 24 .07 .08 .03 .03 2.2 2.3 4.0 4.0 5 3 11 17 27 28 441 46 31 .12 .11 .05 .04 2.9 3.6 4.0 5.0 8 8 14 19 40 41 643 33 36 .06 .07 .04 .04 1.2 1.3 2.0 2.0 4 3 8 13 19 19 444 44 58 .07 .08 .05 .04 1.9 2.1 4.0 3.0 6 4 22 20 33 30 4
Table 2–7. Mean concentrations of selected polycyclic aromatic hydrocarbons in samples collected from a stormwater-filtration device, Madison, W2005–07. —Continued [All concentrations in micrograms per liter; <, less than; --, no sample processed for event] 

Sampling event 

number

2-Methylnaph-

thalene

1-Methylnaph-

thalene

Acenaphthylene

Acenaphthene

Anthracene

Benzo[b] fluor-

anthene

Benzo[k]fluoran-

thene

Benzo[a]pyrene

Chrysene

Fluoranthene

9H-Fluorene

Indeno [1,2,3-cd] 

pyrene

Phenanthrene

Pyrene

Benzo [ghi] 

perylene

Inlet

10 <0.049 <0.064 <0.11 0.08 0.25 5.2 2.4 2.8 4.6 13 <0.52 3.8 5.8 9.2 4.0 

11 <.49 <.64 <1.1 <.64 .97 18 8.2 12 17. 47 <5.2 13 26 36 14 

13 <.049 <.064 <.11 <.064 .05 1.7 .68 .66 1.4 3.7 <.52 1.10 1.4 2.5 1.2 16 <.049 <.064 <.11 <.064 .19 4.0 1.7 1.8 3.6 11 <.52 2.80 4.1 7.1 3.0 17 <.049 <.064 <.11 .16 .32 5.2 2.3 1.9 4.8 15 <.52 3.80 7.3 10 4.1 18 <.049 <.064 <.11 <.064 .14 3.4 1.5 .78 3.1 8.9 <.52 2.40 3.2 5.9 2.6 19 <.049 <.064 <.11 .09 .36 7.5 3.6 4.1 7.0 19 <.52 5.30 7.2 14 5.7 23 <.049 <.064 <.11 <.064 .30 8.1 3.7 5.5 7.1 18 <.52 5.90 6.3 13 6.3 24 <.049 <.064 <.11 <.064 .24 5.4 2.5 3.9 4.7 12 <.52 4.10 4.2 9.0 4.3 25 <.049 <.064 <.11 <.064 .29 4.8 2.2 3.6 4.3 11 <.52 3.50 4.0 8.7 3.8 37 .11 <.064 <.11 -- .35 9.8 4.6 5.7 8.4 24 <.52 5.80 11 17 7.1 38 <.049 <.064 <.11 <.064 .06 2.1 1.1 .84 1.8 4.5 <.52 1.20 1.9 3.1 1.4 40 .09 <.064 <.11 .17 .25 6.4 2.8 3.7 5.5 18 <.52 3.60 6.6 11 4.4 41 .09 <.064 <.11 <.064 <.28 10 4.8 6.1 8.8 25 <.52 6.20 8.8 17 7.4 43 .09 <.064 <.11 .11 .25 3.8 1.8 2.4 3.6 11 <.52 2.40 4.1 7.3 2.8 

Outlet

10 <.049 <.064 <.11 <.064 .15 4.2 1.8 2.1 3.4 8.7 <.52 3.0 4.4 6.6 3.2 

11 <.15 <.2 <.33 .24 .49 11 4.8 6.4 9.5 25 <1.6 7.6 13 19 8.4 

13 <.049 <.064 <.11 <.064 <.031 .91 .36 .33 .62 1.6 <.52 .62 .60 .99 .53 16 <.049 <.064 <.11 <.064 .07 2.6 1.1 .85 2.2 5.9 <.52 1.8 2.7 4.0 1.9 17 <.049 <.064 <.11 <.064 .04 2.3 .93 .42 2.0 5.2 <.52 1.6 1.7 3.5 1.7 18 <.049 <.064 <.11 <.064 .09 2.3 .97 .38 1.9 5.7 <.52 1.6 2.1 3.7 1.7 
Table 2–7. Mean concentrations of selected polycyclic aromatic hydrocarbons in samples collected from a stormwater-filtration device, Madison, W2005–07. —Continued [All concentrations in micrograms per liter; <, less than; --, no sample processed for event] 

Sampling event 

number

2-Methylnaph-

thalene

1-Methylnaph-

thalene

Acenaphthylene

Acenaphthene

Anthracene

Benzo[b] fluor-

anthene

Benzo[k]fluoran-

thene

Benzo[a]pyrene

Chrysene

Fluoranthene

9H-Fluorene

Indeno [1,2,3-cd] 

pyrene

Phenanthrene

Pyrene

Benzo [ghi] 

perylene

Outlet—continued

19 <0.049 <0.064 <0.11 <0.064 0.12 3.2 1.4 1.1 2.7 7.0 <0.52 2.3 2.6 4.7 2.3 23 <.049 <.064 <.11 <.064 .07 2.7 1.1 1.4 2.3 5.7 <.52 1.9 1.8 3.9 2.0 24 <.049 <.064 <.11 <.064 .06 1.8 .77 1.1 1.5 3.5 <.52 1.3 1.2 2.6 1.4 25 <.049 <.064 <.11 <.064 .13 3.5 1.6 2.4 3.0 6.7 <.52 2.6 2.6 5.2 2.8 37 .12 <.064 <.11 .19 .44 9.6 4.6 6.2 8.0 22. <.52 6.2 10 16 7.2 38 <.049 <.064 <.11 <.064 <.031 1.2 .49 .42 .82 2.1 <.52 .61 .88 1.4 .76 40 .05 <.064 <.11 <.064 .11 3.7 1.7 2.0 3.1 8.9 <.52 2.1 3.1 5.4 2.6 41 <.049 <.064 <.11 <.064 <.15 6.2 2.7 3.4 5.2 14. <.52 5.0 5.0 9.6 4.5 43 <.049 <.064 <.11 <.064 <.031 1.1 .42 .46 .80 2.0 <.52 .65 .69 1.3 .75 
Table 2–8. Particle-size distributions in samples collected from a stormwater-filtration device, Madison, Wis., 2005–07. —Continued [All data are in percent by mass; <, less than; μm, micrometer] Sampling event number <500 μm <250 μm <125 μm <63 μm <31 μm <16 μm <8 μm <4 μm 

Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Out

1 99 96 98 92 48 80 29 64 18 48 15 32 14 29 12 22 98 90 95 80 49 70 29 36 13 10 10 10 9 10 8 14 97 96 74 91 50 87 48 67 41 58 29 50 26 47 22 47 97 96 84 92 81 88 78 78 70 74 46 48 39 40 29 38 99 99 89 97 86 93 73 79 64 79 37 62 27 53 18 39 79 97 74 94 69 88 57 66 44 45 31 33 27 31 22 2

10 98 96 78 91 74 87 56 66 38 39 27 33 23 30 16 2

11 97 96 85 91 76 76 53 45 38 28 21 23 15 21 10 1

12 88 97 85 94 77 84 59 61 40 38 26 28 19 25 14 213 69 91 62 81 52 72 33 62 25 53 23 43 3 40 3 315 92 88 84 75 64 63 42 50 27 38 22 33 20 28 17 116 66 98 62 96 56 88 43 63 29 43 20 31 16 26 12 217 86 97 78 95 59 92 41 65 29 38 18 29 14 26 9 218 55 94 52 89 47 83 37 72 26 58 23 57 22 53 19 419 81 93 70 86 52 80 45 73 24 50 19 46 17 39 16 320 94 97 67 94 61 90 48 82 35 79 24 62 19 48 15 323 77 96 71 93 54 89 34 67 22 47 18 42 14 35 12 324 95 90 72 80 67 71 53 61 40 51 31 49 22 49 18 425 70 95 68 90 60 78 40 60 24 47 23 47 23 45 22 426 97 92 80 85 77 77 61 62 37 45 34 42 32 40 31 327 98 98 96 96 87 94 78 87 63 76 43 59 32 45 25 328 91 93 83 85 74 78 66 70 57 63 31 45 24 39 21 329 89 89 77 77 66 66 55 55 43 43 36 34 34 27 27 130 96 94 82 89 73 89 60 89 48 70 44 64 34 49 27 432 94 90 82 79 76 79 70 79 58 79 53 71 48 63 43 533 89 97 87 94 84 94 80 94 74 87 71 82 65 75 53 6
Table 2–8. Particle-size distributions in samples collected from a stormwater-filtration device, Madison, Wis., 2005–07. —Continued [All data are in percent by mass; <, less than; μm, micrometer] 

Sampling 

event 

number

<500 μm <250 μm <125 μm <63 μm <31 μm <16 μm <8 μm <4 μm 

Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Out

34 98 97 91 94 80 82 61 69 49 58 48 55 44 49 38 436 97 97 94 95 91 87 76 70 63 52 59 43 51 32 46 237 91 86 82 71 73 71 73 71 73 71 71 69 67 66 62 638 97 95 84 90 71 90 42 65 27 45 26 44 25 41 24 340 99 98 88 96 79 91 59 71 36 48 34 47 31 45 29 441 97 67 94 33 90 33 79 33 57 33 55 33 52 33 49 342 95 90 90 79 86 79 67 79 52 79 50 73 47 65 46 543 90 95 84 90 77 90 66 70 51 52 48 48 46 41 43 344 90 95 87 90 84 90 71 79 55 60 53 53 51 45 48 345 93 91 87 82 80 82 60 82 45 57 43 54 41 46 39 4
44 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

Table 2–9. Loads of suspended solids, suspended sediment, volatile solids, and dissolved solids in stormwater samples collected 

from a stormwater-filtration device, Madison, Wis., 2005–07. —Continued 

[All data in pounds; --, no sample processed for event]

Sampling

event

number

Suspended solids, 

total 

Concentrations of 

suspended sediment Solids, volatile Solids, dissolved 

Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet 

1 1.8 1.0 2.8 0.9 -- -- -- --

2 1.0 .7 1.9 .6 -- -- -- --

3 3.1 2.0 3.9 1.9 -- -- 6.9 7.0

4 5.2 6.3 5.8 6.6 -- -- 8.2 11.3

5 .8 .3 .8 .3 -- -- 1.6 2.0

6 2.1 2.1 2.4 1.9 -- -- -- --

7 16.8 11.1 18.5 11.1 3.7 2.7 -- --

8 1.1 1.1 1.5 1.1 .3 .3 -- --

9 4.7 2.7 6.0 2.7 1.3 .8 -- --

10 .6 .5 .6 .5 .2 .2 -- --

11 2.8 1.6 3.0 1.6 .9 .5 -- --

12 9.2 .1 .7 .1 .9 .1 -- --

13 .6 .2 .7 .2 .5 -- -- --

14 1.7 .3 1.7 .3 -- -- -- --

15 5.4 1.8 4.1 1.6 2.9 .8 -- --

16 1.5 .9 2.5 .8 .6 .4 -- --

17 .9 .5 1.4 .4 .3 .2 -- --

18 .8 .6 1.4 .5 .3 .2 -- --

19 9.3 7.1 11.8 5.7 3.0 2.3 -- --

20 .9 .5 .8 .3 .3 -- -- --

21 2.6 2.1 2.7 2.1 -- -- -- 3.2

22 .3 .2 .3 .2 -- -- -- --

23 .4 .3 .6 .2 .1 .1 -- --

24 3.4 1.2 3.2 1.0 1.0 -- -- --

25 1.9 2.0 1.5 1.4 1.0 .6 -- --

26 .1 .4 1.0 .4 -- -- -- --

27 .0 .7 .8 .7 .3 .2 -- --

28 .2 .2 .2 .2 .1 .1 -- --

29 .1 .1 .3 .3 -- -- -- --

30 .7 .4 2.3 .4 -- -- -- --

31 .3 .1 .3 .1 -- -- -- --

32 .1 .1 .1 .1 .1 .0 -- --

33 2.9 2.2 2.9 1.9 1.2 .9 7.7 8.2

34 2.9 2.8 2.8 2.8 1.2 1.3 -- --

35 2.5 1.9 2.9 2.4 .6 .9 -- --

36 2.4 2.3 3.6 2.6 .8 .6 -- --
Appendix 2 45

Table 2–9. Loads of suspended solids, suspended sediment, volatile solids, and dissolved solids in stormwater samples collected 

from a stormwater-filtration device, Madison, Wis., 2005–07. —Continued 

[All data in pounds; --, no sample processed for event]

Sampling

event

number

Suspended solids, 

total 

Concentrations of 

suspended sediment Solids, volatile Solids, dissolved 

Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet 

37 4.6 5.7 4.9 5.9 2.1 1.5 -- --

38 .3 .1 .3 .2 -- -- -- --

39 .0 .0 .1 .0 -- -- -- --

40 .8 .5 .8 .4 .3 .2 -- --

41 3.1 1.8 3.4 2.0 1.1 .6 -- --

42 -- -- -- -- -- -- -- --

43 .4 .2 .4 .2 .1 .1 -- --

44 1.1 1.0 .9 .7 .5 .4 -- 3.9

45 1.5 1.8 1.8 1.3 1.8 1.3 -- --

46 -- -- 1.0 .6 -- -- -- --

47 -- -- .9 .9 -- -- -- --

48 -- -- .7 .5 -- -- -- --

49 -- -- .9 .9 -- -- -- --

50 -- -- .2 .1 -- -- -- --

51 -- -- 2.6 3.6 -- -- -- --
Table 2–10. Loads of selected constituents in stormwater samples collected from a stormwater-filtration device, Madison, Wis., 2005–07. —Continu[All loads in pounds; --, no sample processed for event] Sampling event number Chemical oxygen demand, total Phosphorus, total Phosphorus, dissolved Chloride, dissolved Copper, dissolved Copper, total recoverable Zinc, dissolved 

Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet 

1 0.6 1.9 0.011 0.010 0.0077 0.008 0.22 0.25 0.0002 0.0002 0.0004 0.0004 0.0010 0.0010 2 2.3 1.6 .0086 .0071 .0047 .0043 .22 .27 .00005 .00005 .00021 .00031 -- -- 3 -- -- -- -- -- -- 2.84 3.01 -- -- -- -- -- -- 4 -- -- -- -- -- -- 2.41 4.08 -- -- -- -- -- -- 5 -- -- -- -- -- -- .44 .57 -- -- -- -- -- -- 6 1.4 7.0 .0050 .0048 .0137 .0024 .61 .63 .00031 .00027 .00064 .00048 -- -- 7 13 7.2 .0213 .0161 .0054 .0059 .62 .57 .00044 .00040 .00173 .00148 .00198 .00248 1.0 .94 .0858 .0021 .0009 .0009 .18 .20 .00012 .00010 .00021 .00017 .00026 .00049 3.5 1.7 .0079 .0059 .0027 .0016 .24 .25 .00007 .00013 .00053 .00040 .00080 .0014

10 .52 .63 .0019 .0016 .0009 .0008 .06 .09 .00002 .00002 .00008 .00008 .00032 .0005

11 .30 1.1 .0012 .0034 .0045 .0014 .09 .09 .00003 .00003 .00020 .00013 .00039 .0005

12 1.2 .77 .0028 .0018 .0016 .0013 .09 .11 .00012 .00013 .00019 .00019 .00039 .000513 .52 1.6 .0067 .0051 .0049 .0035 -- .22 .00046 .00027 .00035 .00035 .00139 .001514 -- -- -- -- -- -- .09 .10 -- -- -- -- -- -- 15 2.6 1.9 .0059 .0047 .0021 .0014 .10 -- .00011 .00011 .00037 .00027 .00043 .000416 1.4 .87 .0037 .0045 .0027 .0029 .09 .10 .00019 .00019 .00025 .00025 .00037 .000517 1.3 1.2 .0051 .0056 .0031 .0023 .13 .14 .00019 .00022 .00080 .00030 .00060 .001118 1.7 1.7 .0129 .0125 .0084 .0087 .38 .38 .00140 .00095 .00228 .00190 .00304 .003019 3.7 1.7 .0094 .0084 .0053 .0059 .13 .14 .00030 .00029 .00151 .00058 .00093 .001020 .64 .83 .0028 .0034 .0019 .0025 .07 .08 .00006 .00006 .00019 .00019 .00058 .000521 -- -- -- -- -- -- .03 .04 -- -- -- -- -- -- 22 -- -- -- -- -- -- .02 .03 -- -- -- -- -- -- 23 4.7 5.6 .0089 .0069 .0047 .0051 .13 -- .00006 .00006 .00067 .00051 .00135 .001624 1.9 -- .0038 .0033 .0020 .0019 .10 .11 .00006 .00006 .00038 .00025 .00113 .001125 1.4 2.1 .0022 .0024 .0009 .0003 .09 .10 .00006 .00006 .00033 .00033 .00122 .001226 -- -- -- -- -- -- -- .06 -- -- -- -- -- -- 
Table 2–10. Loads of selected constituents in stormwater samples collected from a stormwater-filtration device, Madison, Wis., 2005–07. —Continu[All loads in pounds; --, no sample processed for event] 

Sampling 

event 

number

Chemical 

oxygen 

demand, 

total

Phosphorus, 

total

Phosphorus, 

dissolved

Chloride, 

dissolved

Copper, 

dissolved

Copper, 

total 

recoverable

Zinc, 

dissolved

Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet 

27 1.6 1.4 0.0037 0.0032 0.0023 0.0020 0.05 0.07 0.00008 0.00012 0.00027 0.00020 0.00035 0.000528 .60 .60 .0048 .0050 .0038 .0038 .11 .11 .00013 .00013 .00013 .00013 .00053 .001029 -- -- -- -- -- -- .06 .06 -- -- -- -- -- -- 30 -- -- -- -- -- -- .04 .04 -- -- -- -- -- -- 32 3.5 2.1 .0032 .0037 .0022 .0021 .13 .16 .00015 .00015 .00015 .00015 .00118 .001933 1.3 1.2 .0037 .0032 .0013 .0012 1.45 1.29 .00007 .00007 .00037 .00029 .00073 .001134 -- -- -- -- -- -- .34 .40 -- -- -- -- -- -- 35 7.5 5.5 .0135 .0130 .0024 .0024 .47 .70 .00016 .00016 .00130 .00114 .00162 .002236 3.1 3.3 .0080 .0082 .0033 .0036 .49 .57 .00026 .00026 .00077 .00051 .00180 .002537 .98 .85 .0029 .0030 .0015 .0017 -- .22 .00007 .00007 .00026 .00026 .00039 .000738 .07 .07 .0004 .0004 .0002 .0003 .03 .04 .00001 .00001 .00003 .00004 .00007 .000140 2.0 1.9 .0052 .0063 .0023 .0024 .17 .18 .00031 .00031 .00039 .00023 .00085 .001341 2.4 1.6 .0063 .0057 .0028 .0021 .15 .19 .00021 .00026 .00042 .00042 .00073 .000943 1.2 1.3 .0023 .0025 .0015 .0016 .04 .05 .00007 .00007 .00015 .00011 .00030 .000444 3.3 4.3 .0054 .0057 .0039 .0028 .14 .16 .00030 .00022 .00045 .00030 .00164 .0014
48 Parking Lot Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wisconsin, 2005–07

Table 2–11. Loads of selected polycyclic aromatic hydrocarbons in stormwater samples collected from a stormwater-filtration 

device, Madison, Wis., 2005–07. 

[All data in pounds; --, no sample processed for event] Sampling event number 2-Methylnaphthalene, water, unfiltered, recoverable 1-Methylnaphthalene, water, unfiltered, recoverable Acenaphthylene, water, unfiltered, recoverable Acenaphthene, water, unfiltered, recoverable

Anthracene, water, 

unfiltered, recoverable

Benzo[b]fluoranthene, water, 

unfiltered, recoverable

Benzo[k]fluoranthene, water, 

unfiltered, recoverable

Benzo[a]pyrene, water, 

unfiltered, recoverable

Chrysene, water, 

unfiltered, recoverable

Inlet

10 -- -- -- -- 9.91131E-06 0.000206155 9.51486E-05 0.000111007 0.000182368

11 -- -- -- -- 6.3742E-05 .001182841 .00053885 .00078856 .001117127

13 -- -- -- -- 6.01522E-06 .000196651 7.86605E-05 7.6347E-05 .000161948

16 -- -- -- -- 1.17632E-05 .000247647 .00010525 .000111441 .000222882

17 -- -- -- -- 3.21507E-05 .000522448 .000231083 .000190895 .00048226

18 -- -- -- -- 5.31464E-05 .001290698 .000569425 .000296101 .001176812

19 -- -- -- -- 4.18393E-05 .000871653 .000418393 .000476503 .000813542

23 -- -- -- -- 5.0507E-05 .001363688 .000622919 .000925961 .001195332

24 -- -- -- -- 3.01087E-05 .000677445 .000313632 .000489266 .000589628

25 -- -- -- -- 3.2129E-05 .00053179 .000243737 .000398842 .000476395

37 -- -- -- -- 2.28096E-05 .000638669 .000299783 .000371471 .00054743

38 -- -- -- -- 8.35809E-07 3.0793E-05 1.61296E-05 1.23172E-05 2.6394E-05

40 -- -- -- -- 1.94153E-05 .000497032 .000217452 .000287347 .000427137

41 -- -- -- -- -- .000521362 .000250254 .000318031 .000458799

43 -- -- -- -- 1.22194E-06 1.85735E-05 8.79799E-06 1.17307E-05 1.7596E-05

Outlet

10 -- -- -- -- 5.94679E-06 .00016651 7.13615E-05 8.3255E-05 .000134794

11 -- -- -- -- 3.21996E-05 .000722847 .000315424 .000420566 .000624277

13 -- -- -- -- -- .000105266 4.16438E-05 3.81735E-05 7.17199E-05

16 -- -- -- -- 4.39574E-06 .000160971 6.81029E-05 5.2625E-05 .000136206

17 -- -- -- -- 4.42072E-06 .000231083 9.34379E-05 4.21978E-05 .000200942

18 -- -- -- -- 3.22674E-05 .000873119 .000368228 .000144254 .000721272

19 -- -- -- -- 1.39464E-05 .000371905 .000162708 .000127842 .000313795

23 -- -- -- -- 1.24584E-05 .000454563 .000185192 .000235699 .00038722

24 -- -- -- -- 7.02536E-06 .000225815 9.65987E-05 .000137998 .000188179

25 -- -- -- -- 1.44026E-05 .000387763 .000177263 .000265895 .000332368

37 -- -- -- -- 2.86749E-05 .000625635 .000299783 .000404056 .000521362

38 -- -- -- -- -- 1.7596E-05 7.18502E-06 6.15859E-06 1.20239E-05

40 -- -- -- -- 8.54274E-06 .000287347 .000132024 .000155323 .00024075

41 -- -- -- -- -- .000323245 .000140768 .000177263 .000271108

43 -- -- -- -- -- 5.37655E-06 2.05286E-06 2.24837E-06 3.91022E-06
Appendix 2 49

Table 2–11. Loads of selected polycyclic aromatic hydrocarbons in stormwater samples collected from a stormwater-filtration 

device, Madison, Wis., 2005–07. —Continued 

[All data in pounds; --, no sample processed for event] Sampling event number Fluoranthene, water, unfiltered, recoverable 9H-Fluorene, water, unfiltered, recoverable Indeno[1,2,3-cd]pyrene, water, unfiltered, recoverable

Phenanthrene, water, 

unfiltered, recoverable

Pyrene, water, 

unfiltered, recoverable

Benzo[ghi]perylene, water, 

unfiltered, recoverable

Benzo[a]anthracene, water, 

unfiltered, recoverable

Dibenzo[a,h]anthracene, water, 

unfiltered, recoverable

Naphthalene, water, 

unfiltered, recoverable

Inlet

10 0.000515388 -- 0.000150652 0.000229942 0.000364736 0.000158581 4.75743E-05 -- --

11 .003088528 -- .000854274 .001708548 .002365681 .000919987 .000328567 -- --

13 .000428006 -- .000127245 .000161948 .000289193 .000138813 1.96651E-05 -- --

16 .000681029 -- .000173353 .000253838 .000439574 .000185735 -- -- --

17 .001507063 -- .000381789 .000733437 .001004709 .000411931 -- -- --

18 .003378591 -- .000911081 .001214774 .00223974 .000987004 -- -- --

19 .002208187 -- .000615968 .000836786 .001627085 .000662456 .000220819 -- --

23 .003030418 -- .000993304 .001060646 .002188635 .001060646 .000303042 -- --

24 .001505434 -- .000514356 .000526902 .001129075 .000539447 .000188179 -- --

25 .001218684 -- .000387763 .000443158 .000963869 .000421 .000188342 -- --

37 .001564087 -- .000377988 .000716873 .001107895 .000462709 .000110789 -- --

38 6.59849E-05 -- 1.7596E-05 2.78603E-05 4.54563E-05 2.05286E-05 4.98553E-06 -- --

40 .001397903 -- .000279581 .000512564 .000854274 .00034171 8.54274E-05 -- --

41 .001303406 -- .000323245 .000458799 .000886316 .000385808 9.38452E-05 -- --

43 5.37655E-05 -- 1.17307E-05 2.00399E-05 3.56807E-05 1.36858E-05 4.74114E-06 -- --

Outlet

10 .000344914 -- .000118936 .000174439 .000261659 .000126865 2.25978E-05 -- --

11 .001642834 -- .000499422 .000854274 .001248554 .000551992 .000164283 -- --

13 .000185084 -- 7.17199E-05 6.94064E-05 .00011452 6.13089E-05 -- -- --

16 .000365279 -- .000111441 .000167162 .000247647 .000117632 -- -- --

17 .000522448 -- .000160753 .0001708 .000351648 .0001708 -- -- --

18 .002163816 -- .000607387 .000797196 .001404583 .000645349 -- -- --

19 .000813542 -- .000267307 .000302173 .000546236 .000267307 4.41637E-05 -- --

23 .000959632 -- .000319877 .000303042 .000656591 .000336713 6.06084E-05 -- --

24 .000439085 -- .000163089 .000150543 .000326177 .000175634 4.01449E-05 -- --

25 .00074229 -- .000288053 .000288053 .000576105 .000310211 8.53079E-05 -- --

37 .001433746 -- .000404056 .000651703 .001042725 .000469226 .000143375 -- --

38 3.0793E-05 -- 8.94462E-06 1.29037E-05 2.05286E-05 1.11441E-05 1.437E-06 -- --

40 .000691185 -- .000163089 .00024075 .000419371 .000201919 4.19371E-05 -- --

41 .000729907 -- .000260681 .000260681 .000500508 .000234613 4.64012E-05 -- --

43 9.77554E-06 -- 3.17705E-06 3.37256E-06 6.3541E-06 3.66583E-06 6.3541E-07 -- --
Table 2–12. Parking lot comparison of geometric concentrations from several studies in Wisconsin. [mg/L, milligrams per liter; μg/L, micrograms per liter; --, no data available] Study Total suspended solids (mg/L) Suspended sediment concentration (mg/L) Dissolved phosphorus (mg/L) Total phosphorus (mg/L) Total copper (μg /L) 

Madison Gas and Electric Company, Madison 20 21 0.03 0.11 4.9 City of Madison Water Utility, Madison (U.S. Environmental Protection Agency, 2004) 96 121 .088 .20 5.1 St. Mary’s Hospital parking lot, Green Bay (Horwatich, 2000) 36 127 .021 .082 -- City maintenance yard, Madison (Waschbusch, 1999) 180 -- .12 .34 17 City garage & parking lot, Milwaukee (Corsi and others, 1999) 259 -- .011 .26 30 Commercial strip, Madison (Waschbusch and others, 1999) 50 -- .016 .09 -- Commercial strip, Marquette, Mich., (Steuer and others, 1997) 138 -- .22 .21 25 Commercial strip, Madison (Bannerman and others, 1993) 58 -- .05 .19 9 Commercial strip, Milwaukee (Bannerman and others, 1983; Post Office) 116 -- .05 .26 -- Shopping Center, Milwaukee (Bannerman and others, 1983; Rustler) 38 -- .026 .101 -- 
Publishing support provided by the U.S. Geological Survey 

Publishing Network, Columbus Publishing Service Center

For more information concerning the research in this report, contact the 

Director, Wisconsin Water Science Center 

U.S. Geological Survey 

8505 Research Way 

Middleton, Wisconsin 53562 

http://wi.water.usgs.gov/
Horwatich and Bannerman—Runoff Quality and Treatment Efficiency of a Stormwater-Filtration Device, Madison, Wis., 2005–07—Scientific Investigations Report 2009–5196