Prepared in cooperation with the 

Massachusetts Department of Environmental Protection, the 

U.S. Environmental Protection Agency, and the City of Cambridge

Potential Reductions of Street Solids and Phosphorus 

in Urban Watersheds from Street Cleaning, 

Cambridge, Massachusetts, 2009–11

Scientific Investigations Report 2012–5292

U.S. Department of the Interior

U.S. Geological Survey
Front cover. Photographs showing regenerative-air street cleaner and storm drain. 

Back cover. Photograph of rotary gutter broom of a regenerative-air street cleaner in action.
Potential Reductions of Street Solids 

and Phosphorus in Urban Watersheds 

from Street Cleaning, Cambridge, 

Massachusetts, 2009–11

By Jason R. Sorenson

Prepared in cooperation with the

Massachusetts Department of Environmental Protection, the

U.S. Environmental Protection Agency, and the City of Cambridge

Scientific Investigations Report 2012–5292

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: 2013

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

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as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Sorenson, J.R., 2013, Potential reductions of street solids and phosphorus in urban watersheds from street cleaning, 

Cambridge, Massachusetts, 2009–11: U.S. Geological Survey Scientific Investigations Report 2012–5292, 66 p., plus 

appendix 1 on a CD–ROM in pocket. (Also available at http://pubs.usgs.gov/sir/2012/5292/.)
iii

Acknowledgments

This work was supported in part by the Massachusetts Department of Environmental Protection 

(08E4MA2441101801), the U.S. Environmental Protection Agency (DW-14-95772401-0), and 

the City of Cambridge as American Recovery and Reinvestment Act Grantee 2009-08/ARRA 60 

(10E4MA24410120).

The author wishes to extend his gratitude to Owen O’Riorden, John Nardone, Paul Tulley, 

George Stylianopoulis, John Fitzgerald, Lenny Silva, and Wendy Robinson of the Cambridge 

Department of Public Works; Gary Gonyea and Tom Maguire of the Massachusetts Department 

of Environmental Protection; Mark Voorhees and Michael Borst of the U.S. Environmental 

Protection Agency; Kenneth Young, Gary Young, Bryan Young, Bob Hatfield, and Jeff O’Malley 

of TYMCO Regenerative Air Sweepers, Inc.; Jon Casey, Warren Leonard, and Joseph Arena, of 

Casey and Dupuis; student intern Eli Yuan-Vogel of the University of Massachusetts at Amherst; 

and Northeastern Co-op students Andrew Ingalls, Marine Langreney, A.J. Spiers, and Melissa 

Weil. Many thanks to Sgt. James Crowley, Alicia Popovics, and the many police officers of 

the Cambridge Police Department who helped maintain traffic safety. Special thanks to Roger 

Bannerman of the Wisconsin Department of Natural Resources for his insight and guidance.

The author also wishes to thank Paul Buono, Tony Cannarsa, Leslie DeSimone, Gregory Granato, 

Jennifer Savoie, Marcus Waldron, Phillip Zarriello, and Robert Breault of the U.S. Geological 

Survey (USGS). Many thanks also to USGS Volunteers for Science Mary Gowins and Sandra 

Petrakis. Special thanks to Judy Horwatich, William Selbig, and Kirk Smith of the USGS for their 

guidance and thoughtful reviews.
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v

Contents

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

Introduction.....................................................................................................................................................2

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

Description of the Study Area ............................................................................................................2

Previous Studies ...................................................................................................................................4

Street-Solid Collection, Processing, and Chemical Analysis.................................................................7

Street-Solid Sample Collection ..........................................................................................................7

Street-Solid Sample Processing and Chemical Analysis ..............................................................8

Street-Solid Sample Processing ...............................................................................................8

Performance Evaluation Sample Analysis ............................................................................13

Blank Sample Analysis .............................................................................................................13

Replicate Sample Analysis.......................................................................................................13

Street-Cleaner Efficiency Sample Collection and Processing....................................................15

Characterization of Street Solids ..............................................................................................................16

Street-Solid Mass...............................................................................................................................16

Particle-Size Distribution...................................................................................................................17

Spatial Distribution of Street Solids.................................................................................................19

Street-Solid Accumulation................................................................................................................21

Street-Solid Washoff..........................................................................................................................21

Regenerative-Air Street Cleaner Removal Efficiency ..................................................................24

Street-Solid Chemistry.......................................................................................................................27

Accumulation Rate Estimates of Organic Carbon and Elements.......................................30

Washoff Estimates of Organic Carbon and Elements..........................................................30

Estimates of Regenerative-Air Street Cleaner Removal of Organic Carbon and 

Elements ........................................................................................................................33

Potential Reductions of Street Solids and Phosphorus Achievable by Street Cleaning .................33

Description of Commercial Land-Use Subcatchment ..................................................................33

Source Loading and Management Model......................................................................................35

Relative Contributions of Source Areas.................................................................................35

Model Output Compared to 1999–2000 Runoff and Water-Quality Data...........................35

Model Output Compared to 2009–2011 Street-Solid Yield Data.........................................38

Model Simulations..............................................................................................................................38

Street-Cleaning Program Performance .................................................................................38

Summary and Conclusions.........................................................................................................................42

References Cited..........................................................................................................................................44

Appendix 1. Supplemental Data Tables (CD–ROM)............................................................................59

Appendix 2. Source Loading and Management Model for Windows (WinSLAMM)....................61
vi

Figures

1. Location map of A, the City of Cambridge, Massachusetts, and B, land-use 

distribution, and municipal street-cleaning districts..............................................................3

2. Aerial photograph showing the boundary between municipal street-cleaning districts 

D and E, approximate location of multifamily and commercial study street sections, 

locations of city construction and private development, and location of the predominantly commercial land-use subcatchment used in the Source Loading and 

Management Model, Cambridge, Massachusetts..................................................................6

3. Photograph of curb-to-curb street-solid composite sampling equipment and 

municipal police detail to ensure traffic safety, Cambridge, Massachusetts....................9

4. Photograph of A, two cleaned vacuumed paths typical of street-solid composite 

sampling, and examples of a rough street-surface and a poor street-surface 

condition, and B, a smooth street surface with good street-surface condition, curband-gutter drainage system, and an example of unusual loading avoided during 

sampling, Cambridge, Massachusetts....................................................................................10

5. Photograph of A, a street-solid composite sample contained within a 0.1 micrometer 

paper filter bag being extracted from the vacuum, folded, and placed into a labeled 

clear plastic ziplock bag, Cambridge, Massachusetts, and B, stainless steel riffle 

splitter and receiving pans used for large volumes or heterogeneous street-solid 

sample ..........................................................................................................................................11

6. Photograph of a TYMCO Dustless Sweeping Technology-6 regenerative-air street 

cleaner in Cambridge, Massachusetts ...................................................................................16

7. Graph showing daily precipitation and average street-solid yields between 

March 2010 and 2011 measured within multifamily and commercial land-use types 

during periods of dry weather and bracketed rainstorms from curb-to-curb 

composite samples, and estimated yields during removal-efficiency experiments 

from single side composite samples .......................................................................................18

8. Boxplot showing seasonal and end-of-winter street-solid yields, in pounds per 

curb-mile from streets in A, multifamily, and B, commercial land-use types, 

Cambridge, Massachusetts ......................................................................................................20

9. Boxplot showing accumulation rates by grain-size fraction and total solids, in 

pounds per curb-mile per day from streets in A, multifamily and B, commercial landuse types, Cambridge, Massachusetts...................................................................................22

10. Graphs showing street-solid yield by grain-size fraction and total yield, in pounds 

per curb-mile per day as a function of time in days since the last rain or street 

cleaning on streets in multifamily and commercial land-use types, Cambridge, 

Massachusetts............................................................................................................................23

11. Boxplot showing percent washoff of street solids by grain-size fraction estimated for 

storms with a recorded rainfall volume range of 0.32 to 1.71 inches, from streets in 

A, multifamily and B, commercial land-use types, Cambridge, Massachusetts..............25

12. Graphs showing average percent washoff for each grain-size fraction, and average 

total washoff for storms with a recorded rainfall volume range of 0.32 to 1.71 inches 

as a function of A, total rain depth, and B, rainfall intensity from streets in multifamily 

and commercial land-use types, Cambridge, Massachusetts............................................26

13. Boxplot showing street-solid yields before and after a single pass of a 

regenerative-air street cleaner on streets in A, multifamily and B, commercial 

land-use types, Cambridge, Massachusetts..........................................................................28
vii

14. Graphs showing A, removal efficiency plot of a regenerative-air street cleaner 

making a single pass on streets with smooth to rough street-surface conditions 

and heavy on-street parking with monthly parking controls, in multifamily and 

commercial land-use types Cambridge, Massachusetts ....................................................29

15. Boxplot showing total phosphorus yields, in pounds per curb-mile, by season from 

streets representing predominantly A, multifamily and B, commercial land-use types 

in Cambridge, Massachusetts..................................................................................................31

16. Predominantly commercial land-use subcatchment in Cambridge, Massachusetts, 

and U.S. Geological Survey flow and water-quality monitoring station (USGS ID: 

01104677), over a 0.5-meter color orthophoto obtained from MassGIS ............................34

17. Graphs showing cumulative relative percent contributions of major source areas 

within the A, multifamily, B, institutional, and C, commercial land-use types contained 

in the modeled commercial subcatchment, Cambridge, Massachusetts.........................36

18. Plots of A, rainfall depth as compared to runoff depth, and B, runoff coefficient as 

compared to rainfall depth from commercial subcatchment observations, March to 

December 2000, Cambridge, Massachusetts (USGS ID: 01104677) ...................................37

19. Graph showing simulated runoff depth as compared to observed runoff depth, 

March to December 2000, Cambridge, Massachusetts (USGS ID: 01104677)..................39

20. Graph showing time series of simulated outfall discharge from the commercial 

land-use subcatchment as compared to observed runoff volume, March to 

December 2000, Cambridge, Massachusetts (USGS ID: 01104677) ...................................39

21. Graph showing simulated as compared to observed street-solid yields for multifamily 

and commercial land-use areas, Cambridge, Massachusetts (2010 data only)..............40

22. Graphs showing simulated and observed street-solid yields, April 2010 to 

March 2011 for A, multifamily and B, commercial land-use types within the modeled 

subcatchment, Cambridge, Massachusetts ..........................................................................41

Tables

1. Land-use types and percent of total area for Cambridge, Massachusetts........................4

2. Characteristics of study-street sections, Cambridge, Massachusetts...............................5

3. Target analytes and analytical techniques for samples submitted to SGS 

Laboratories, Toronto, Ontario, Canada..................................................................................12

4. Median values and relative standard deviations for selected concentrations of 

total and total-recoverable trace elements in quality-control samples............................14

5. Selected analytical results of graded unground silica sand used as blank material 

sourced from Ottawa, Illinois....................................................................................................15

6. Summary of Cambridge, Massachusetts, street-solid yields by land-use type and 

grain-size fraction.......................................................................................................................19

7. Comparison of Cambridge, Massachusetts, street-solid yields by land-use type to 

those in other areas of the United States...............................................................................19

8. Average, median, maximum, and minimum removal efficiency, in percent, of a 

regenerative-air street cleaner on multifamily and commercial land-use streets in 

Cambridge, Massachusetts ......................................................................................................27

9. Total and grain-size fraction median constituent total-recoverable concentrations 

and masses constituent masses from composite street-solid samples collected 

from streets representing A, multifamily and B, commercial land-use types in 

Cambridge, Massachusetts ......................................................................................................48
viii

10. Street-solid composite sample collection dates, sample type, antecedent rain conditions, sampled storm volume, street-solid yield, and total phosphorus yields from 

streets in Cambridge, Massachusetts ....................................................................................32

11. Accumulation rates for constituents measured in street-solid composite samples, 

by grain-size fraction and land-use type collected before and after precipitation 

events in pounds per curb-mile per day, Cambridge, Massachusetts..............................52

12. Percent washoff of constituent masses in terms of grain-size fraction and land-use 

type from street-solid composite samples collected before and after 6 storms with a 

recorded rainfall volume range of 0.32 to 1.71 inches, Cambridge, Massachusetts.......54

13. Median percent reductions for total and grain-size fractions of constituents 

measured in seasonal composite of street-solid yields collected before and after a 

single pass of a regenerative-air street cleaner on streets representing multifamily 

and commercial land-use types in Cambridge, Massachusetts ........................................56

14. Source Loading and Management Model estimated percent reductions of total and 

particulate solids and phosphorus using single passes by three different streetcleaning technologies at various frequencies in a predominantly commercial 

subcatchment, Cambridge, Massachusetts ..........................................................................42
ix

Conversion Factors, Datum, and Abbreviations

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 2.59 square kilometer (km2)

acre 0.4047 hectare (ha)

acre 4046.94 square meter (m2)

Volume

gallon (gal) 3.79 liter (L)

gallon (gal) 0.003785 cubic meter (m3)

cubic inch (in3) 0.01639 liter (L)

cubic foot (ft3) 0.02832 cubic meter (m3)

Mass

ounce, avoirdupois (oz) 28.35 gram (g)

pound avoirdupois (lb) 0.4535 kilogram (kg)

pounds per curb-mile (lbs/curb-mi) 0.2819 grams per curb-meter (g/curb-m)

tons per day (ton/d) 0.9075 metric ton per day (mt/d)

Flow

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

cubic feet per minute (ft3/min) 0.02831685 cubic meter per minute (m3/min)

Speed

miles per hour (mph) 1.609 kilometer per hour (kmph)

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

 °F=(1.8×°C)+32

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Altitude, as used in this report, refers to distance above the vertical datum.

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

or micrograms per liter (μg/L).

Concentrations of chemical constituents in solids are given either in milligrams per kilogram 

(mg/kg), or as a percent (%).
x

List of Abbreviations

COV coefficient of variation

CTC curb-to-curb

EIA effective impervious area

HE high efficiency

NIST National Institute of Science and Technology

NOAA National Oceanic and Atmospheric Administration

NRCS National Resource Conservation Service

NURP National Urban Runoff Program

PES performance evaluation sample

RA regenerative air

RPD relative percent differences

SCM stormwater control measures

SLAMM Source Loading and Management Model

SS single sided

SSC suspended solids concentration

TMDL total maximum daily load

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey
Potential Reductions of Street Solids and Phosphorus 

in Urban Watersheds from Street Cleaning, Cambridge, 

Massachusetts, 2009–11

By Jason R. Sorenson

Abstract

Material accumulating and washing off urban street 

surfaces and ultimately into stormwater drainage systems 

represents a substantial nonpoint source of solids, phosphorus, 

and other constituent loading to waterways in urban areas. 

Cost and lack of usable space limit the type and number 

of structural stormwater source controls available to 

municipalities and other public managers. Non-structural 

source controls such as street cleaning are commonly used 

by cities and towns for construction, maintenance and 

aesthetics, and may reduce contaminant loading to waterways. 

Effectiveness of street cleaning is highly variable and potential 

improvements to water quality are not fully understood. In 

2009, the U.S. Geological Survey, in cooperation with the 

Massachusetts Department of Environmental Protection, 

the U.S. Environmental Protection Agency, and the city of 

Cambridge, Massachusetts, and initiated a study to better 

understand the physical and chemical nature of the organic 

and inorganic solid material on street surfaces, evaluate the 

performance of a street cleaner at removing street solids, and 

make use of the Source Loading and Management Model 

(SLAMM) to estimate potential reductions in solid and 

phosphorus loading to the lower Charles River from various 

street-cleaning technologies and frequencies.

Average yield of material on streets collected between 

May and December 2010, was determined to be about 

740 pounds per curb-mile on streets in multifamily land use 

and about 522 pounds per curb-mile on commercial landuse streets. At the end-of-winter in March 2011, about 2,609 

and 4,788 pounds per curb-mile on average were collected 

from streets in multifamily and commercial land-use types, 

respectively. About 86 percent of the total street-solid yield 

from multifamily and commercial land-use streets was greater 

than or equal to 0.125 millimeters in diameter (or very fine 

sand). Observations of street-solid distribution across the 

entire street width indicated that as much as 96 percent of total 

solids resided within 9 feet of the curb. Median accumulation 

rates of street solids and median washoff of street solids after 

rainstorms on multifamily and commercial land-use streets 

were also similar at about 33 and 22 pounds per curb-mile per 

day, and 35 and 40 percent, respectively. Results indicate that 

solids on the streets tested in Cambridge, Mass., can recover 

to pre-rainstorm yields within 1 to 3 days after washoff. The 

finer grain-size fractions tended to be more readily washed 

from the roadway surfaces during rainstorms. Street solids 

in the coarsest grain-size fraction on multifamily streets 

indicated an average net increase following rainstorms and are 

likely attributed to debris run-on from trees, lawns, and other 

plantings commonly found in residential areas.

In seven experiments between May and December 2010, 

the median removal efficiency of solids from street surfaces 

following a single pass by a regenerative-air street cleaner 

was about 82 percent on study sites in the multifamily landuse streets and about 78 percent on the commercial land-use 

streets. Median street-solid removal efficiency increased 

with increasing grain size. This type of regenerative-air street 

cleaner left a median residual street-solid load on the street 

surface of about 100 pounds per curb-mile. 

Median concentrations of organic carbon and total phosphorus (P) on multifamily streets were about 35 and 29 percent greater, respectively, than those found on commercial 

streets. The median total mass of organic carbon and total P 

in street solids on multifamily streets was 68 and 75 percent 

greater, respectively, than those found on commercial streets. 

More than 87 percent of the mass of total P was determined 

to be in solids greater than or equal to 0.125 millimeters in 

diameter for both land-use types. The median total accumulation rate for total P on multifamily streets was about 5 times 

greater than on commercial streets. Total P accumulation in 

the medium grain-size fraction was nearly the same for streets 

within both land-use types at 0.004 pounds per curb-mile 

per day. Accumulation rates within the coarsest and finest 

grain-size fractions on multifamily streets were about 11 and 

82 times greater than those on the commercial streets. Median 

washoff of total P was 58 and 48 percent from streets in 

multifamily and commercial land-use types, respectively, and 

generally increased with decreasing grain size. Total P median 

reductions resulting from a single pass of a regenerative-air 

street cleaner on streets in multifamily and commercial landuse types were about 82 and 62 percent, respectively, and were 

similar in terms of grain size between both land-use types. 
2 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

A Source Loading and Management Model for Microsoft 

Windows (WinSLAMM) was applied to a 21.8 acre subcatchment in Cambridge, Mass. The subcatchment area consists of 

mostly commercial and multifamily land-use types to evaluate 

the potential reductions of total and particulate solids, and P 

attributed to street cleaning. Rainwater runoff from rooftops 

represented between 20 and 50 percent of the total basin runoff. Street surfaces only accounted for about 20 percent of the 

total basin runoff. 

Monthly applications of mechanical-brush and vacuumassisted street cleaners within the subcatchment as defined by 

SLAMM for areas with long-term (24-hour) on-street parking 

and monthly parking controls using five average climatic years 

resulted in total solid reductions of about 3 and 5 percent, 

respectively. Simulating the regenerative-air street cleaner 

tested as part of this study resulted in total solid reductions of 

about 16 percent. Increasing street cleaning frequency to three 

times weekly increased total solids removal for mechanicalbrush, vacuum-assisted, and regenerative-air street cleaners to 

about 6, 14, and 19 percent, respectively. Monthly applications 

of mechanical-brush, vacuum-assisted, and regenerative-air 

street cleaners within the subcatchment resulted in total P 

reductions of about 1, 3, and 8 percent, respectively. A street 

cleaning frequency of three times each week for each of the 

three street-cleaner types increased total P removal to about 3, 

7, and 9 percent, respectively.

Introduction

A TMDL (Total Maximum Daily Load) for total phosphorus (P) has been established for the lower Charles River 

basin (Massachusetts Department of Environmental Protection 

and others, 2007). To meet the total P criteria in this TMDL, 

the city of Cambridge, Massachusetts, is expected to achieve 

more than a 65-percent reduction in total P loading contributed 

to the Charles River from all city sources. Part of this reduction is expected from the management of stormwater runoff. 

Structural stormwater control measures (SCMs) are one type 

of nonpoint source runoff management, but urban areas are 

limited by the lack of usable space and high installation costs, 

thus making nonstructural SCMs, such as street cleaning (or 

street sweeping) a more practical alternative. Street cleaning 

may provide some load reduction, but monitoring these reductions in urban runoff as a result of a street cleaning program 

is difficult. Moreover, in Cambridge, Mass., which receives 

rain about every 3.5 days (National Oceanic and Atmospheric 

Administration, 2011), the effectiveness of street cleaning to 

reduce phosphorus loads to the lower Charles River is further 

minimized. To better quantify the potential benefits and limitations of street cleaning programs in urban areas at reducing 

total solids and P loads, a study was initiated in 2009 with the 

U.S. Geological Survey (USGS), in cooperation with the 

Massachusetts Department of Environmental Protection 

(MassDEP), the U.S. Environmental Protection Agency 

(USEPA), and the city of Cambridge, Mass.

Purpose and Scope

This report describes the physical characteristics of the 

solids found on street surfaces in predominantly high-density/

multifamily residential and commercial land-use areas within 

Cambridge, Mass., during 10 months of sampling between 

August 2009 and March 2011. Analytical results of organic 

carbon and 32 elements including total P for selected samples 

also are presented. The report contains discussions of the 

physiochemical characteristics of street-solid samples before 

and after rain storms and during periods of dry weather to 

estimate street-solid accumulation and washoff because of precipitation. The development of removal efficiency coefficients 

based on street solids collected before and after a single pass 

of a regenerative-air street cleaner as part of a monthly streetcleaning program is presented. The report also documents the 

construction and evaluation of the model WinSLAMM version 

9.4.0 (Pitt and Voorhees, 2002) to provide total and particulate solids and total and particulate P load reduction estimates 

resulting from three street-cleaning technologies operated at 

various frequencies within a predominantly commercial landuse subcatchment.

Description of the Study Area

The city of Cambridge is a 7.1 square mile (mi2) urban 

municipality located in eastern Massachusetts along the 

northern bank of the Charles River (fig. 1A). The city of 

Boston borders Cambridge to the south and east. The cities of 

Watertown, Belmont, Arlington, and Somerville also border 

Cambridge. Watertown lies to its southwest, Belmont and 

Arlington border the west, and Somerville borders Cambridge 

to the north. Topographically, the city generally slopes upward 

toward the west. Elevation to the northwest at Porter Square 

and to the southwest at Fresh Pond are about 47 to 40 feet 

(ft) above sea level, respectively, (Porter Square observation 

point, Weather Underground, 2011), and USGS Fresh Pond 

gage (USGS ID: 422302071083801). Fresh Pond, located in 

southwest Cambridge (fig. 1B) is a kettle pond with a 2,000 to 

3,000 foot-wide moraine to its south that trends northwest. The 

surficial geology of the remainder of the city is characterized 

as outwash sands and gravels overlying tills associated with 

drumlins (Skeehan, 2001). Based on Boston climatic data 

between 1872 and 2002, the average annual temperature range 

for the area is about -6.1 to 27.2 degrees Celsius (°C) (21 to 

81 degrees Fahrenheit). Total annual precipitation is about 

42 inches (in.), which is evenly distributed throughout the 

year as rainfall and snow (National Oceanic and Atmospheric 

Administration, 2011). 

The 2000 census determined there were about 

15,936 persons per square mile in Cambridge, making it the 

fifth most densely populated city in the United States at that 

time (U.S. Census Bureau, 2010, table C–1), and the fifth 

most populated city in the State. High-density/multifamily 

residential and commercial land-use areas make up more than 
Introduction 3

CONNECTICUT

4 NEW YORK

VERMONT

NEW HAMPSHIRE

MAINE

RHODE 

ISLAND

Basemap data, 1999 land use coverage, MassGIS. 

Northings and eastings in state plane meters. 

0 760 1,520 2,280 3,040 METERS

228,000 229,000 230,000 231,000 232,000 233,000 234,000 235,000 236,000

900,000 901,000 902,000 903,000 904,000 905,000 906,000

50,000 120,000 190,000 260,000 330,000

800,000 850,000 900,000 950,000 1,000,000

Watertown

Belmont

Somerville

Boston

Arlington

Boston

Boston

Fresh Pond

Charles River

A

Major land use types (MassGIS):

Cambridge municipal, and 

street-cleaning district 

boundaries and district 

designation

Roads

D

Residential, Multifamily

Residential, High-density

Residential, Low-density

Commercial

Institutional

Industrial

Water

Water-based recreation

Forest

Wetland

B

EXPLANATION

B

D A

E

F

H

G J

J

K J

C

0 2,493 4,987 7,480 9,974 FEET

Figure 1. Location map of A, the City of Cambridge, Massachusetts, and B, land-use distribution, and municipal street-cleaning districts.
4 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

40 percent of the total area of the city of Cambridge (table 1, 

fig. 1B). Three streets representing predominantly highdensity/multifamily residential (referred to as multifamily) 

and three streets representing predominantly commercial 

land-use types were selected within municipal street-cleaning 

districts D and E based on cleaning frequency, geographic 

orientation, traffic volume, street-surface condition, proximity 

to locations with existing stormwater loading data, and 

overall safety (table 2, fig. 2). Institutional and industrial, and 

residential and institutional land-use types also were present 

in the multifamily and commercial study street sections, 

respectively. Basic characteristics of the three multifamily and 

three commercial land-use street sections, including pavement 

condition index and 24-hour daily traffic count data where 

available (written commun., city of Cambridge), are listed in 

table 2. The lengths of the street sections ranged from 750 to 

1,304 ft. The average street width was between 25 and 43 ft. 

In addition, observations of pavement texture and condition, 

and measurements of percent canopy closure were made at 

each of the six asphalt streets.

Table 1. Land-use types and percent of total area for 

Cambridge, Massachusetts (Based on 1999 land-use coverage).

[<, less than]

Land-use type Area 

(acres)

Percent 

of total 

area

Cropland 1.0 0.0

Forest 71.7 1.6

Wetland 42.5 0.9

Open land 33.3 0.7

Participation recreation 245.3 5.4

Water-based recreation 5.9 0.1

Residential, multifamily 1,304.6 28.5

Residential, high density (lots <0.25 acre) 360.2 7.9

Residential, median density (lots 0.25–0.5 acre) 34.2 0.7

Commercial 590.9 12.9

Industrial 551.5 12.0

Urban open 31.0 0.7

Transportation 105.0 2.3

Waste disposal 10.4 0.2

Water 460.9 10.1

Golf 67.1 1.5

Urban public (schools, churches, govt offices) 505.4 11.0

Transportation facilities 68.3 1.5

Cemeteries 95.0 2.1

Total 4,584.2 100

The city uses a monthly street-cleaning program between 

April and December making use of primarily mechanicalbrush sweepers, but during April and November, a tandem 

approach using a mechanical-brush followed by a regenerative-air street cleaner as a means to pick up extra street load 

associated with end-of-winter (EOW) and leaf-fall seasons. 

Monthly cleaning is scheduled such that even- and oddnumbered sides of the streets in a district are usually cleaned 

throughout the course of two days. Street cleaning activities 

are carried out by contractors and the public works department. Although certain squares, commercial streets, and 

surrounding areas with limited or no on-street parking are 

swept weekly or more, most city streets are grouped into welldefined monthly street-cleaning districts (fig. 1). In calendar 

years 2009 and 2010, about 1,605 and 1,042 tons of material 

were removed from Cambridge streets, respectively (written 

commun., Cambridge Department of Public Works, 2011).

Previous Studies

The National Urban Runoff Program (NURP) conducted 

from the late 1970s and through the early 1980s provided the 

basis for understanding of street cleaning effects on urban 

stormwater runoff. Sartor and Boyd (1972) performed the 

earliest direct experiments to determine street-solid accumulation and washoff. Pitt (1979) developed sampling techniques 

to better understand the nature of street-surface solids that are 

essentially still used. As part of the NURP projects, the U.S. 

Environmental Protection Agency (USEPA; 1983) determined 

that urban stormwater runoff contains high concentrations of P 

that contribute to eutrophication. The USEPA (1983) and Pitt 

(1987) reported that mechanical-brush sweepers were determined to be only 10 to 30 percent effective at removal of street 

solids. Since the NURP era, an increasing number of studies 

have examined the physical and chemical nature of urban runoff and the potential environmental benefits of street cleaning. 

Pitt and others (2004) provide tables of selected studies and 

their respective results in terms of material accumulation and 

washoff from street surfaces. Discussion of several selected 

studies investigating P in runoff and water-quality benefits of 

street cleaning follows below. 

Steuer and others (1997) determined that Marquette, 

Michigan lawns were the dominant source (26 percent) of total 

P loading in the basin, yet only represented 6 percent of the 

total runoff. Waschbusch and others (1999) determined lawns 

and streets in Madison, Wisconsin, were the largest sources of 

total and dissolved P and total P loads from these source areas 

and were proportional to the percentage of runoff at one site 

(37 percent) and about one-half the percentage of runoff at 

the second site (14 percent). They also observed that 75 percent of the street-dirt mass was greater than 250 micrometers 

(μm) in diameter, and less than 5 percent was less than 63 μm 

in diameter.
Introduction 

5

Table 2. Characteristics of study-street sections, Cambridge, Massachusetts. Daily traffic count data and pavement-condition index data courtesy of the Cambridge Department of Public Works.[ft, feet; --, no data]

Street name

Study 

section 

length 

(ft)

Average 

width 

(ft)

Predominant 

land-use type

24-hour 

average daily 

traffic counts

Traffic type, 

direction

24-hour 

on-street 

parking

Pavement 

condition 

index-entire 

street 

(percent)

Observed pavement texture* 

within the study 

street section only

Observed pavement 

composition/

condition†

within the study 

street section only

Canopy 

closure 

(percent)

Broadway 1,210 40 Multifamily 220,500 2-way, east/west Both sides 67–80 Smooth Asphalt/good 15Highland Avenue 1,072 25 Multifamily -- One way, south Both sides 81–92 Intermediate Asphalt/fair 55Fayette Street 1,287 25 Multifamily -- One way, north Both sides 81–92 Rough Asphalt/poor 54Cambridge Street 1,304 43 Commercial 114,500 2-way, east/west Both sides 81–92 Smooth Asphalt/good 24Mount Auburn Street 1,278 30 Commercial 29,860 One way, east, 2 lanes One side 81–92 Intermediate Asphalt/fair 17Green Street 750 25 Commercial -- One way, west Both sides 93–100 Rough Asphalt/poor 23

1Cambridge, DPW traffic-count data, 2000.2Cambridge, DPW traffic-count data, 2002.†Observations of the smoothness or roughness of the street surface.*Street-construction type/observations of breaks and open features in the street surface.
6 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11 231,800 232,400

902,400 902,000

2

2A

Street-Cleaning

District D

Street-Cleaning

District E

Highland Ave

Fayette Street

Cambridge Street

Charles River

Broadway/Ellery Drainage End Date

—October 2010

High School RenovationSpring/Summer 2010

Harvard Square Surface Enhancement Start Date—October 2010

Chapter 90 Contract 11

End Date October 2010 —

Cambridge Housing AuthoritySummer/Fall 2010

75-77 HancockSpring/Summer 2010

Common Manhole Contract 4End Date

—October 15, 2010

CMH 4 and 6 Surface RestorationStart Date

—October 1, 2010

Fog MuseumSummer, 2010

Green Street

Broadway

Mount Auburn Street

Ellery Street

Mass. Ave. 

Harvard Street

Model subcatchment

Basemap data, MassGIS. Northings and eastings in state plane meters. 

0 140 280 420 560 METERS0 459 919 1,378 1,837 FEET

Figure 2. Aerial photograph showing the boundary between municipal street-cleaning districts D and E, approximate location of multifamily (green) and commercial (blue) study street sections, locations of city construction (red lines) and private development (red circles), and location of the predominantly commercial land-use subcatchment used in the Source Loading and Management Model, Cambridge, Massachusetts.
Street-Solid Collection, Processing, and Chemical Analysis 7

Breault and others (2005) conducted a study examining 

the organic and inorganic chemistry and accumulation rates 

of street dirt in residential areas, and evaluated the relative performance of a mechanical-brush and vacuum street 

cleaners as part of a pilot study in New Bedford, Mass. (not 

shown). An accumulation rate of about 50 pounds per curbmile per day (lbs/curb-mi/day) was reported, and coarser size 

fractions between 2.0 and 0.250 millimeter (mm) appeared 

to accumulate most rapidly. About 93 percent of the material 

was determined to be greater than very fine sand (greater than 

0.125 mm). Organic and inorganic constituent concentrations of street solids were similar to those reported in other 

studies, and total P was about 3.60 milligrams per kilogram 

(mg/kg) with the highest concentrations attributed to size 

fractions less than 0.125 mm in diameter. The vacuum street 

cleaner removal efficiencies were between 62 and 92 percent 

compared to removal efficiencies between 20 and 31 percent 

observed for the mechanical-brush street cleaner.

Selbig and Bannerman (2007) used a paired-basin 

approach (Clausen and Spooner, 1993) in Madison, Wis., to 

evaluate street-dirt particulate and stormwater loading under 

control conditions without street cleaning and under streetcleaning conditions using multiple frequencies and three 

different street-cleaning technologies. Average and median 

residential street-dirt yields were reported to be about 614 and 

569 lbs/curb-mi, respectively, or about 1.6 times the national 

average reported by Sartor and Boyd (1972). Comparison of 

paired-basin results indicated that potential load reductions 

from street cleaning are likely limited by the extreme variability in stormwater runoff loads. The removal efficiency of street 

cleaners was determined to increase with increasing street-dirt 

yield. Average street-dirt removal efficiencies of regenerative-air and vacuum-assist cleaners were 25 and 30 percent, 

respectively. Weekly operation of mechanical-brush sweepers 

reduced average street-dirt loads by 5 percent. An increase 

in street-dirt particles less than 0.250 mm in diameter was 

reported after street cleaning. The largest and most evenly 

distributed yield of street dirt was measured during the spring. 

Law and others (2008) conducted sampling and chemical 

analysis of street solids from streets in a control and treatment subcatchment in Baltimore, Md. A conceptual model of 

pollutant removal rates for weekly and monthly frequencies 

of mechanical and regenerative/vacuum-assist treatments was 

developed. A street cleaner removal efficiency of 14 percent 

was reported, and the lower value was attributed to frequent 

and intense storms and the twice weekly cleaning frequency 

during their experimental period. An average street-solid load 

of 645 lbs/curb-mi for their treatment area and an average 

street-solid load of 1,100 lbs/curb-mi was estimated from the 

control area, which was not swept. Law and others (2008) 

determined that particle-size distribution was similar for 

before- and after-cleaning street-solid load samples. They 

reported about 40 percent of sampled street-solid load particles 

were between 0.250 to 1.0 mm in diameter, and 70 percent 

of the total street-solid load consisted of particles larger than 

0.250 mm in diameter. Lead (Pb) and total P concentrations 

were determined to be significantly higher in their unswept 

control basin. The concentration of total P and total Kjeldahl 

nitrogen (TKN) was greater for solids larger than 0.250 mm in 

diameter. This tendency was attributed to organic matter, such 

as leaf litter that often contains substantial amounts of these 

constituents, in their samples. The resulting estimated range of 

reductions for total solids, total nitrogen, and total P as a 

result of street cleaning were 9 to 31, 3 to 8, and 3 to 7 percent, respectively.

Seattle Public Utilities and Department of Transportation 

(2009) sponsored a 1-year paired-basin study in 2006 to determine the effectiveness of street cleaning to reduce the mass of 

organic and inorganic constituents to urban waterways and the 

effectiveness of reducing the frequency of catch-basin cleaning. Median yields of street solids that included organic matter 

ranged from 69 to 2,200 lbs/curb-mi on streets that were swept 

twice per month. Analysis of grain-size fractions of street solids showed between 43 and 95 percent of the total mass was 

greater than 0.250 mm in diameter. Monthly samples of solids 

from streets in residential land-use areas had organic carbon 

concentrations between 6 and 38 percent. TKN and total P 

dry-weight concentrations in street-solid samples ranged from 

49 to 36,600, and 191 to 1,610 mg/kg, respectively. Although 

reductions in street-solid yields resulting from bi-monthly 

street cleaning ranged from 48 to 90 percent in Seattle, no significant reductions in constituent concentrations or reductions 

in catch-basin cleaning were reported.

Street-Solid Collection, Processing, 

and Chemical Analysis

Street-solid samples were collected from the surfaces 

of six street sections (table 2 and fig. 2). Three streets were 

selected in predominantly high-density/multifamily residential 

land-use areas (referred to as multifamily) and three streets 

were selected in predominantly commercial land-use areas. 

Study street sections were selected based on land-use designation, safety considerations, and street-cleaning frequency. 

Samples were collected to characterize the accumulation of 

street solids, the washoff of street solids because of rainfall 

runoff, the removal efficiency of street solids by a regenerative-air street cleaner, and the concentrations of organic carbon 

and 32 elements including P in street solids.

Street-Solid Sample Collection

Samples were collected to represent average street-solid 

characteristics found in the two land-use types. Sampling 

methods were the similar to those used by Pitt (1979) and 

Burton and Pitt, (2002), and the same equipment used in this 

study was used by Selbig and others (2007). Four 9-gallon, 

stainless steel wet/dry vacuums with a maximum air flow of 

92 cubic feet per minute were used to collect the samples. 
8 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

Each street had a dedicated intake-hose setup that included a 

6-inch wide aluminum intake nozzle attached to a 6-foot long 

stainless steel wand connected to the vacuum by a 2-in. diameter reinforced black neoprene hose between 15 and 35 ft long 

(fig. 3). All equipment was kept in the bed of a pickup truck 

and covered with a hard cap. Aluminum nozzles wore down 

and their intake width narrowed with use over the rough street 

surfaces. Nozzle widths were measured before each sampling 

event and recorded on field sheets. When nozzle widths were 

less than 5 inches, they were replaced.

Ten subsamples also were collected from each street 

and weighed individually to determine the variability in 

street-solid yields (Selbig and others, 2007), and were used 

to calculate the number of subsamples needed in a composite 

sample to accurately represent street-solid yields as described 

by Hansen and others (1984). Using an allowable error of 

0.50 (or plus or minus (±) 50 percent), the calculated number 

of samples needed was less than 7; however, if the allowable 

error was reduced to 0.25, the number of subsamples increased 

to 49. For this study 10 subsamples were collected for all composites on all streets. Unusual loading conditions such as piles 

of debris, potholes or areas near construction track out were 

avoided during sampling to maintain the representativeness of 

the composite sample. Although 10 markers were painted on 

the vertical side of the curb on each street section, the sampling locations varied for each sampling event because of the 

heavy on-street parking, which often limited where sampling 

crews could collect subsamples. The reproducibility of the 

street-solid sample collection procedures was evaluated using 

a Mann-Whitney/rank-sum test. Twelve street-solid composite 

sample pairs were used and results indicated no significant 

difference between the pairs of samples (p = 0.68). The good 

precision between sample pairs indicates that sources of variability in street-solid yields were not introduced by samplecollection techniques.

A single subsample involved vacuuming from curb to 

curb across the street moving at about 1 foot per second or less 

with increasing street surface roughness. It was common to see 

a cleaned path where material was removed following a vacuumed pass (fig. 4A). Autumn brought a large amount of leaf 

material to street surfaces that would often clog the intake nozzle. Under these conditions, leaves along the sample path were 

manually sampled and placed into pre-weighed and labeled 

plastic bags. Eleven composite samples were collected during 

the summer of 2009, and were collected in a manner similar 

to the procedure described by Selbig and others (2007) where 

street-dirt material was collected directly into the vacuum 

stainless steel canisters, its cloth filter was brushed off, shaken 

into the canister, then all material was brushed out into preweighed clear plastic bags. Sample collection was modified 

for all 2010–2011 vacuumed composite samples, which were 

collected in pre-weighed 0.1 μm paper filter bags. Paper filter 

bags were chosen to limit field crew exposure to particulate 

matter, minimize loss of finer fraction to the air, and reduce 

overall time spent in the field. Composite samples contained 

in the 0.1 μm paper filter bags were removed from the vacuum 

canisters, the intake port closed, and material within the bag 

was allowed to settle to the bottom before it was folded and 

sealed inside a labeled clear plastic ziplock bag (fig. 5A). 

Street-Solid Sample Processing and Chemical 

Analysis

Street-solid samples were processed and prepared for 

shipment to SGS Environmental Services Laboratory in 

Ontario, Canada for analysis of 32 elements and organic carbon. Performance evaluation samples (PESs), equipment blank 

samples, and replicate samples also were prepared and submitted for analysis. Street solids in this study are defined as all 

material collected on street surfaces including all gravel and 

asphalt and all organic material to as much as about 50 mm in 

diameter. All visible anthropogenic material such as plastic, 

metal, and cigarette butts was not included.

Street-Solid Sample Processing

Samples were taken to the USGS Northborough, 

Massachusetts laboratory, where they were weighed and dried 

within the paper filter bags for 14 hours at 105 °C. Dried 

samples were weighed again and separated into three grainsize fractions herein designated as: “coarse,” or material 

greater than or equal to 2 mm, “medium,” or material less 

than 2 mm to greater than or equal to 0.125 mm, and “fine,” 

or material less than 0.125 mm in diameter using stainless 

steel sieves. A 4-mm stainless-steel sieve was used to screen 

out larger material before sieving; when the sample material 

was too great for a single set of sieves, multiple sets were 

used. Sieves were washed using phosphate-free detergent and 

rinsed with tap water, followed by three rinses with deionized 

water, then dried before each use. Emptied paper filter bags 

were weighed again and the difference between its tare weight 

and the weight of the emptied bag was added to the less than 

0.125-mm size fraction (defined as very fine sand). The sample 

mass results for each street are listed in appendix tables 1–15 

and 1–16 (on CD–ROM at back of report). Data were omitted 

if the relative percent difference between the sum of the three 

grain-size fraction masses and the initial total dry mass was 

more than 15 percent. 

About 10 to 20 grams (g) of representative street-solids 

material was subsampled from each of the three separated 

grain-size fractions, placed into labeled Whirl-pak bags and 

shipped to SGS laboratories for analysis of organic carbon, 

total P, and 31 other elements (table 3). In cases where there 

were large amounts of material or the material was too heterogeneous to be subsampled representatively, a riffle splitter 

(fig. 5B) was used to yield representative subsamples for analysis. Although leaves and organic debris were not removed 

from street-solid subsamples, all visible anthropogenic debris 

and litter was removed before submission for chemical analysis. Resulting total-recoverable concentrations of all curbto-curb (CTC; composite samples collected by vacuuming 
Street-Solid Collection, Processing, and Chemical Analysis 9Figure 3. Photograph of curb-to-curb street-solid composite sampling equipment and municipal police detail to ensure traffic safety, Cambridge, Massachusetts. 
10 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

Vacuumed strips

Rough street-surface texture

Broken/cracked 

street-surface condition

Curb-and-gutter 

drainage

A

B

Smooth street-surface texture and good street condition

Curb-and-gutter 

drainage

Unusual street-dirt

loading (not sampled)

Figure 4. Photograph of A, two cleaned vacuumed paths typical of street-solid composite sampling, and 

examples of a rough street-surface and a poor street-surface condition (photo courtesy of Tom Maguire, 

MassDEP), and B, a smooth street surface with good street-surface condition, curb-and-gutter drainage 

system, and an example of unusual loading avoided during sampling, Cambridge, Massachusetts. 
Street-Solid Collection, Processing, and Chemical Analysis 11

B A

Figure 5. Photograph of A, a street-solid composite sample contained within a 0.1 micrometer paper filter bag being extracted from the vacuum, folded, and placed into a labeled clear plastic ziplock bag, Cambridge, Massachusetts (photo courtesy of Tom Maguire, MassDEP), and B, stainless steel riffle splitter and receiving pans used for large volumes or heterogeneous street-solid sample.
12 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

Table 3. Target analytes and analytical techniques for samples submitted to SGS Laboratories, 

Toronto, Ontario, Canada.

[MDL, method detection limit; USEPA, U.S. Environmental Protection Agency; ICP-MS, Inductively Coupled 

Plasma-Mass Spectrometry; ppm, parts per million]

Analyte Units Analytical 

techniques MDL USEPA method

Aluminum, recoverable ppm ICP-MS 100 EPA IC3050B/ICP40

Antimony, recoverable percent ICP-MS 5 EPA IC3050B/ICP40

Arsenic, recoverable ppm ICP-MS 3 EPA IC3050B/ICP40

Barium, recoverable ppm ICP-MS 1 EPA IC3050B/ICP40

Beryllium, recoverable ppm ICP-MS 0.5 EPA IC3050B/ICP40

Bismuth, recoverable ppm ICP-MS 5 EPA IC3050B/ICP40

Cadmium, recoverable percent ICP-MS 1 EPA IC3050B/ICP40

Calcium, recoverable ppm ICP-MS 100 EPA IC3050B/ICP40

Chromium, recoverable ppm ICP-MS 1 EPA IC3050B/ICP40

Cobalt, recoverable ppm ICP-MS 1 EPA IC3050B/ICP40

Copper, recoverable ppm ICP-MS 0.5 EPA IC3050B/ICP40

Iron, recoverable percent ICP-MS 100 EPA IC3050B/ICP40

Lanthanum, recoverable percent ICP-MS 0.5 EPA IC3050B/ICP40

Lead, recoverable ppm ICP-MS 2 EPA IC3050B/ICP40

Lithium, recoverable ppm ICP-MS 1 EPA IC3050B/ICP40

Magnesium, recoverable percent ICP-MS 0.01 EPA IC3050B/ICP40

Manganese, recoverable ppm ICP-MS 2 EPA IC3050B/ICP40

Molybdenum, recoverable ppm ICP-MS 1 EPA IC3050B/ICP40

Nickel, recoverable percent ICP-MS 1 EPA IC3050B/ICP40

Phosphorus, recoverable ppm ICP-MS 100 EPA IC3050B/ICP40

Potassium, recoverable percent ICP-MS 100 EPA IC3050B/ICP40

Scandium, recoverable ppm ICP-MS 0.5 EPA IC3050B/ICP40

Silver, recoverable ppm ICP-MS 0.2 EPA IC3050B/ICP40

Sodium, recoverable ppm ICP-MS 100 EPA IC3050B/ICP40

Strontium, recoverable ppm ICP-MS 0.5 EPA IC3050B/ICP40

Tin, recoverable ppm ICP-MS 10 EPA IC3050B/ICP40

Titanium, recoverable percent ICP-MS 100 EPA IC3050B/ICP40

Tungsten, recoverable ppm ICP-MS 10 EPA IC3050B/ICP40

Vanadium, recoverable ppm ICP-MS 2 EPA IC3050B/ICP40

Yttrium, recoverable ppm ICP-MS 0.5 EPA IC3050B/ICP40

Zinc, recoverable ppm ICP-MS 0.5 EPA IC3050B/ICP40

Zirconium, recoverable ppm ICP-MS 0.5 EPA IC3050B/ICP40

Total organic carbon percent Coulometric titration 0.01 EPA 9060
Street-Solid Collection, Processing, and Chemical Analysis 13

across the street from one curb to the opposite curb) and single 

sided (SS; composite samples collected by vacuuming 9 ft out 

from the curb) street-solid composite samples can be seen in 

appendix tables 1–17, 1–18, 1–19, and 1–20 (on CD–ROM at 

back of report).

Performance Evaluation Sample Analysis

Six National Institute of Standards and Technology 

(NIST) standard reference soil 2710 samples and five NIST 

standard reference soil 2781 samples served as PESs, and 

were submitted to SGS laboratories with street-solid samples 

to determine potential contamination bias and overall method 

performance. The median analytical results and relative standard deviations shown in table 4 are of selected constituents 

for two types of analyses performed on standard reference soil 

samples consist of the following: total concentrations, measured in samples fully digested by hydrofluoric acid, and totalrecoverable concentrations, measured in samples digested by 

less aggressive acid mixtures. The USEPA has determined that 

the total-recoverable concentration represents the bioavailability of elements in the environment (U.S. Environmental 

Protection Agency, 1986). Most analytical results included in 

this report were obtained using the total-recoverable digestion. 

Concentrations certified by the NIST are based on several 

measurements using two or more techniques from multiple 

laboratories using hydrofluoric acid to achieve a complete 

digestion. About 26 percent of the median total concentrations of elements associated with the NIST reference soil 

2710 certified values, and about 12 percent of the median total 

concentrations of elements associated with NIST reference 

soil 2781 certified values that were measured were within 

their respective certified concentration ranges (table 4). The 

elements with median concentrations outside the certified 

concentration ranges were within 16 percent or less of the 

lower range of certified values of NIST reference soil 2710, 

and within 15 percent or less of the lower range of certified 

values of NIST reference soil 2781 (table 4). The relative standard deviations for blind sample concentrations of total P and 

six other elements of concern (shaded values seen in table 4) 

were between 4 and 16 percent for the NIST 2710 results and 

between 2 and 20 percent for the NIST 2781 results. 

Total-recoverable element concentrations obtained 

using the milder digestion described above resulted in 

concentrations that were generally lower than the totalrecoverable concentrations for both NIST standard soils 

2710 and 2781 (table 4). However, median total-recoverable 

concentrations of all constituents in NIST standard 2710 were 

within about 30 percent or less of the lower range of certified 

values except for aluminum (Al), barium (Ba), calcium (Ca), 

potassium (K), sodium (Na), antimony (Sb) and titanium 

(Ti), which were between 45 and 94 percent less than the 

lower range of certified values. All median total-recoverable 

concentrations of constituents in NIST standard 2710 were 

within the recovery range except for K, P, Ti, and vanadium 

(V). Concentrations of Ti, K, and V were 18, 14, and 4 percent 

greater than the upper limit of the recovery range, respectively. 

The median concentration of P was about 18 percent less than 

the lower limit of the recovery range for analyses of NIST 

standard 2710, indicating a potential negative bias in the totalrecoverable concentrations for P. Median total-recoverable 

concentrations of all constituents in NIST standard 2781 

were within about 9 percent or less than the upper limit of the 

recovery range except for Al, cadmium (Cd), chromium (Cr), 

iron (Fe), magnesium (Mg), and manganese (Mn), which were 

1 to 28 percent greater than the upper limit of the recovery 

range. Total P was about 7 percent less than the noncertified 

value of NIST standard 2781, supporting the potential 

negative bias in the total-recoverable concentrations for total P 

indicated by the results for NIST standard 2710.

Blank Sample Analysis

Analyses of organic carbon, total P, and 31 other elements also were done on samples of graded unground silica 

sand. Median results of selected elements were at or below 

the method detection limit, indicating the silica sand was an 

appropriate blank material (table 5). The silica sand was then 

exposed to a precleaned aluminum intake nozzle, neoprene 

hose, and a preweighed 0.1-μm paper filter bag weighed and 

dried and then stored for more than 48 hours in a similar manner as street-solid samples collected in the field. The samples 

were then emptied into stainless steel sieves and shaken for 

30 minutes. Analytical results of total P and other selected elements in the equipment blank silica sand were also at or below 

the method detection limit and demonstrate the sampling 

equipment, filter bags, and processing equipment were not a 

source of sample contamination.

Replicate Sample Analysis

Mean and median RPDs between the sum of the sieved 

fractions and the total dried mass were 5.6 and 0.87 percent, 

and ranged between 0.02 and 70 percent. However, there 

were only five instances where the RPD was greater than 

25 percent. 

Replicate samples of the PESs (NIST 2710 and 2781 

described above) were analyzed using the total and totalrecoverable digestions. Median relative percent differences 

(RPDs) between certified values and resulting total concentrations were about 8 percent using NIST standard reference 

soil 2710 and about 15 percent using NIST standard reference 

soils 2781. Total P median concentration RPDs using NIST 

2710 and 2781 were about 6 and 3.4 percent, respectively. 

These results are within the 25-percent limit established by the 

quality assurance project plan (Sorenson, Quality Assurance 

Project Plan, written commun., accepted May 2010)

Thirty replicate splits of street-solid samples were 

submitted for analysis and the median RPD of resulting 

total concentrations for all elements was about 2 percent and 

about 10 percent for total-recoverable concentrations of all 
14 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11 Table 4. Median values and relative standard deviations (RSD) for selected concentrations of total and total-recoverable trace elements in quality-control samples. [Shaded rows represent major elements of concern; NIST, National Institute of Standards and Technology; ppm, parts per million; RSD, relative standard deviation; ±, plus or minus; --, no data; >, greater than] Analyte NIST standard reference soil 2710 reported concentrations NIST standard reference soil 2710 blind sample analytical results NIST standard reference soil 2781 reported concentrations NIST standard reference soil 2781 blind sample analytical results Certified total value (ppm) Leach range concentrations (ppm) Total concentration Total-recoverable concentration Certified total value (ppm) Leach range concentrations (ppm) Total concentration Total-recoverable concentration Median con- centration (ppm) RSD Median con- centration (ppm) RSD Median con- centration (ppm) RSD Median con- centration (ppm) RSD Aluminum 64,400 ± 800 12,000–26,000 61,200 4 23,250 66 16,0001 980–8,040 14,700 115 10,300 31 Arsenic 626 ± 38 490–600 625 2 554 9 7.82 ± 0.28 -- 11 -- 12 -- Barium 707 ± 51 300–400 693 1 347 48 -- 65–570 579 -- 517 -- Calcium 12,500 ± 300 3,800–4,800 12,100 2 4,150 71 39,0001 1,830–36,440 12,100 3 36,100 5 Cadmium 21.8 ± 0.2 13–26 24 7 24.5 8 12.78 ± 0.72 1-2 11 11 12 4 Cobalt 101 6.3–12 8 16 7 25 101 -- 5 -- 5 -- Chromium 381 15–23 31 16 22 39 2021 15–23 152 20 142 25 Copper 2,950 ± 130 2,400–3,400 2,600 9 2,730 5 627.4 ± 13.5 16–601 550 9 585 5 Iron 33,800 ± 1,000 22,000–32,000 31,300 5 27,750 14 28,000 ± 1,000 2,100–24,300 24,200 10 24,600 9 Lanthanum 341 -- 26.5 18 22.4 29 -- -- 17.6 -- 17.4 -- Potassium 21,100 ± 1,100 3,700–5,000 19,700 5 5,700 81 4,9001 -- 4,100 13 2,500 46 Magnesium 8,530 ± 420 4,300–6,000 7,600 8 5,950 25 5,9001 4,850–290 5,200 9 5,000 12 Manganese 10,100 ± 400 6,200–9,000 9,460 5 7,960 17 -- 33–745 733 -- 765 -- Molybdenum 191 13–27 17 8 15.5 14 46.7 ± 3.2 -- 37 16 38 15 Sodium 11,400 ± 600 490–620 10,600 5 600 127 2,1001 -- 1,900 6 900 57 Nickel 14.3 ± 1.0 8.8–15 12 12 11.5 15 80.2 ± 2.3 6.3–72.3 67 13 69 11 Phosphorus 1,060 ± 150 1,060–1,100 1,000 4 900 12 24,2001 -- 23,400 2 22,600 5 Lead 5,532 ± 80 4,300–7,000 4,910 8 5,085 6 202.1 ± 6.5 15–183 173 11 179 9 Antimony 38.4 ± 3 -- 35 7 6 103 -- -- 10 -- 5 -- Scandium 8.71 -- 8.6 1 4.8 42 -- -- 64 -- 8.7 -- Silver 35.3 ± 1.5 24–30 >10 -- >10 -- 981 1.7–86.3 >10 -- >10 115 Strontium 3301 94–110 317 3 105 73 -- -- 215 -- 206 -- Titanium 2,830 ± 100 920–1,100 2,300 15 1,300 52 3,2001 -- 2,400 20 300 117 Tungsten 931 -- 110 12 35 64 -- -- 10 -- 10 -- Vanadium 76.6 ± 2.3 37–50 64 13 52 28 -- 3.8–81.9 77 -- 80 --

Yttrium 231 -- 17.4 20 14.5 32 -- -- 20.4 -- 17 --Zinc 6,952 ± 91 5,200–6,900 6,340 7 6,010 10 1,273 ± 53 34–1,120 1,090 11 1,090 11

1Noncertified value.
Street-Solid Collection, Processing, and Chemical Analysis 15

Table 5. Selected analytical results of graded unground silica sand used as blank material (determined using one-half the detection 

limit for “less than” values) sourced from Ottawa, Illinois (U.S. Silica Company).

[ppm, parts per million; n, number of samples; E, estimated]

Constituent in ppm 

n =15

Organic 

carbon Cadmium Chromium Copper Nickel Phosphorus Lead Zinc

Detection level 500 1.00 1.00 0.50 1.00 100 2.00 1.00

Maximum E250 E0.05 3.00 0.90 1.00 E50 2.00 4.70

Median E250 E0.05 4.00 0.25 1.00 E50 1.00 1.80

Average E250 E0.05 2.78 0.40 0.94 E50 1.22 1.94

Minimum E250 E0.05 1.00 E0.25 E0.50 E50 1.00 E0.25

32 elements. The median RPD for organic carbon analyses 

was about 8 percent. Evaluation of replicate sample RPDs by 

grain-size fraction indicate median RPDs of the greater than 

or equal to 2 mm (coarse), less than 2 mm to greater than or 

equal to 0.125 mm (medium), and less than 0.125 mm (fine) 

size fractions of about 23, 15, and 5 percent, respectively. 

Smaller RPDs are likely due to the more homogeneous 

material of the smaller grain-size fractions. Gravel and 

organic debris such as leaves or sticks were common in the 

larger grain-size fraction material. Median RPDs of total P 

for all samples were near zero, but ranged from zero to about 

111 percent. The larger RPD was associated with the coarse 

size fraction. The median RPDs for total P by grain size from 

coarse to fine were about 26, 11, and 7 percent, respectively.

Street-Cleaner Efficiency Sample Collection and 

Processing

Both sides of Mount Auburn Street (fig. 2) were swept 

in a single day each month after the city adjusted the cleaning schedule of the southern side of the street from weekly to 

monthly cleaning for consistency. However, street sweepers 

were seen operating on Mount Auburn Street by field crews at 

a frequency greater than the established monthly schedule on 

two occasions, which may have affected street-solid accumulation observations. Washoff sampling was done within 24 

hours or less and removal-efficiency sampling was typically 

done within 4 hours or less, minimizing the effect of unscheduled street cleaning operations.

On days scheduled for cleaning, the sampling crew would 

collect single-sided subsamples from 10 locations along each 

street before the street cleaner made a single pass. Each vacuumed strip was 108 in (9 ft) from the curb, which represents 

the width of the street affected by the street cleaner in a single 

pass. Following the collection of the “pre-treatment” samples, 

a regenerative-air street cleaner was operated over the street 

at 5 miles per hour (mph) or less using a single gutter broom 

(fig. 6). Although waterless operation would have provided 

the most effective removal of all particles, water was applied 

to the gutter broom, not to the street surface, to minimize 

pedestrian dust exposure. Immediately following the single 

street cleaner pass (within about 30 minutes), a second composite sample was collected and labeled as a “post-treatment” 

sample. The difference between the pre- and post-sample 

masses allowed the determination of the street cleaner removal 

efficiency. All samples were collected after the street cleaner 

made a single pass except for samples collected on November 

9 and 12, 2010, when the leaf load on the streets required two 

passes by the regenerative-air street cleaner. On the same dates 

on non-study streets, mechanical-brush sweepers made two to 

four passes before a smaller vacuum-assist machine, operating 

in tandem with the brush sweeper, made its single pass. No 

samples were collected on November 10, 2010, because 

of rain.

Post-treatment samples contained about 48 g of material and when separated into three grain-size fractions, did 

not yield sufficient material to subsample for submission 

to the laboratory for analysis. Seasonal composite samples 

were created to provide sufficient material by combining and 

thoroughly mixing pre- and post-treatment street-cleaner 

efficiency samples within the following spring, summer and 

fall periods: May to June, July to September, and October to 

December. Samples were combined into large labeled clear 

plastic ziplock bags and sealed. The seasonal composite 

sample was then shaken and rotated until a homogeneous 

color and texture was achieved. Representative subsamples 

of these seasonal composites were obtained using the riffle 

splitter (fig. 5B) and were submitted for chemical analysis as 

described above. 
16 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

Pick-up head

Gutter broom 

Figure 6. Photograph of a TYMCO Dustless Sweeping Technology-6 (DST-6) regenerative-air street cleaner in Cambridge, 

Massachusetts (photo courtesy of Tom Maguire, MassDEP). 

Characterization of Street Solids

Street-solid loadings are the result of deposition 

and removal rates plus “permanent storage” and seasonal 

components such as leaf-fall and accumulation of material 

including winter deicing and maintenance materials (Pitt 

and others, 2004). Thirty-five CTC street-solid sampling 

events yielded 195 total mass composite samples collected 

in July and August 2009, between May and December 2010, 

and March 2011. Another 98 single sided (SS) street-solid 

sampling events yielded 194 total mass composite samples 

collected between May and December 2010. Estimates of 

accumulation and washoff of street solids were determined 

using the CTC street-solid sample composites, and removal 

efficiency estimates were calculated using street-solid sample 

composites collected from one side of the street (SS) before 

and after a single pass of a regenerative-air street cleaner. 

Although some samples were collected from late July to early 

September 2009, most samples were collected between May 

and December 2010. The two additional sampling events in 

early March 2011 represent an end-of-winter (EOW) load. 

SS street-solid composite samples representing pre- and 

post-street cleaning street-solid yields were used to develop a 

productivity function, or removal efficiency equation for the 

regenerative-air street cleaner. 

Street-Solid Mass

The average mass of CTC street-solids composite 

samples for 132 selected composite samples from multifamily 

and commercial streets between May and December 2010 

was 612 ± 8 and 427 ± 3 g, respectively. With the inclusion 

of the large amounts of street solids collected in March 

2011, the average mass of street solids for the two land-use 
Characterization of Street Solids 17

types increased to 742 ± 10 and 720 ± 13 g, respectively. 

Comparison of initial sample mass and the mass following 

14 hours at 105 °C in samples from multifamily and 

commercial streets indicate the street solids had an average 

moisture content of about 21 and 14 percent, respectively. 

Although sampling protocols required street surfaces to be dry 

for the collection of composite samples, and areas where water 

ponded were avoided, substantial water content was observed 

within organic debris along curb areas and during several 

cold-weather sampling events, water was frozen to the streetsolid material itself.

Pitt (1979) reported that street-dirt yield was a better unit 

of measure for street cleaner performance as it represents the 

actual mass removed from the street surface. In keeping with 

this convention, all collected street-solid mass composites 

were converted to a composite street-solid yield lbs/curb-mi 

using the following expression:

P

M

WN

L

L

ft i

n

mi i

n

=

 ×



 



 



 

 = 

=

∑

∑

0 0022

2

1

1

.

(1)

where

P is the mass of the dirt on a street, in pounds 

per curb-mile;

n is the total number of streets in each basin;

i is an index to each street sampled in the study 

area;

M is the total mass of sampled street-dirt, in 

grams;

W is the width of the vacuum nozzle, in feet;

N is the number of individual strips vacuumed 

per street;

Lft is the length of each street, in feet; and

Lmi is the length of each street, in miles.

0.0022 is the unit conversion factor between grams and 

pounds, and dividing by 2 accounts for two curblanes. This 

expression also was used to determine yields from singlesided street-solid composite masses but the numerator was not 

divided by two.

Sample composite yields and rain events that occurred 

from May 2010 to March 2011 are shown in figure 7. Street 

solids sampled in Cambridge, Mass., by land-use type and 

grain-size fraction are summarized in table 6. Street-solid 

yields for multifamily and commercial streets in Cambridge, 

Mass., are compared to other studies in the United States 

in table 7. Average multifamily street-solid yield was about 

740 lbs/curb-mi. Median multifamily street-solid yield was 

about 602 lbs/curb-mi. Commercial land-use average and 

median street-solid yields were about 522 and 467 lbs/curbmi, respectively. Average multifamily and commercial yields 

are about 1.9 and 1.7 times the national average (Sartor and 

Boyd, 1972), respectively (table 7). Average and median 

multifamily and commercial street-solid yields increased to 

about 898 and 615, and 887 and 498 lbs/curb-mi, respectively 

when including the large amounts of EOW material collected 

in March 2011. Including the EOW samples increased average 

multifamily and commercial yields to about 2 to 3 times the 

reported national average, respectively. Evaluation of average street-solid yields on a seasonal basis required combining 

results between May and June, July to September, October 

to December 2010, and March 2011, street solid yields from 

each land-use type to represent spring, summer, fall, and EOW 

periods, respectively. The distribution of these seasonal sample 

groups are seen as boxplots in figure 8. Although there are 

only two sampling events on each street in March to represent 

the EOW, an annual street-solid yield cycle is seen in both 

land-use types that is lowest in the spring following spring 

washoff and EOW cleanup, then yields increase through the 

summer and into autumn before the end of the street-cleaning 

season in December, which allows yields to reach their peak 

levels at the EOW. Median street-solid yields from commercial streets were about 16 and 22 percent greater than those 

from multifamily streets for spring and EOW periods, respectively. Summer yields from both land-use types were within 2 

percent of each other. However, multifamily median streetsolid yields were about 42 percent greater than those in commercial streets in the fall. Individual CTC sample dates and 

resulting masses and yields for streets in both multifamily and 

commercial land-use types are seen in appendix table 1–15 (on 

CD–ROM at back of report).

Particle-Size Distribution

Samples were split into three grain-size fractions: coarse, 

medium, and fine, using stainless-steel sieves and sieve shaker. 

The median percent distribution of material in the three grainsize fractions found on the multifamily and commercial streets 

from coarse to fine was about 30, 61, and 9 percent and about 

15, 71, and 14 percent, respectively. It is likely the greater 

proportion of coarse street solids in multifamily street samples 

is due to the tree density and other plantings on those streets 

compared to commercial streets (table 1). In addition, median 

organic carbon yields on multifamily streets were about 

2.5 times greater than those from commercial streets. About 

87 percent of the composite samples from both land-use types 

consisted of material coarser than very fine sand (or greater 

than 0.125 mm). These results are similar to those determined 

in other studies. Waschbusch and others (1999) reported about 

75 percent of sampled street-solid mass in Madison, Wis., was 

greater than 0.250 mm and less than 5 percent was less than 

0.063 mm in diameter; Breault and others (2005) reported 

more than 93 percent of the street solids was greater than 

0.125 mm in diameter in New Bedford, Mass.; and Law and 

others (2008) reported about 70 percent of the street solids was 

greater than 0.250 mm in diameter in Baltimore, Md.
18 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

76543210 0

1,0002,0003,0004,0005,0006,000

SEHCNI NI , NOI TATI PI CERP

b mile r ucr ep sdnuop ni , dl ei y Street-solid

PrecipitationMF yield-CTCMF yield-SSCOM

M yield-CTC

COM

M yield-SS

03/11/10

04/05/10

04/30/10

05/25/10

06/19/10

07/14/10

08/08/10

09/02/10

09/27/10

10/22/10

11/16/10

12/11/10

01/05/10

01/30/10

02/24/10

03/24/10

EXPLANATION

Date

Figure 7. Daily precipitation and average street-solid yields between March 2010 and 2011 measured within multifamily (MF) and commercial (COMM) land-use types during periods of dry weather and bracketed rainstorms from curb-to-curb (CTC) composite samples, and estimated yields during removal-efficiency experiments from single side (SS) composite samples. Precipitation data courtesy of the Cambridge Department of Public Works.
Characterization of Street Solids 19

Table 6. Summary of Cambridge, Massachusetts, street-solid 

yields by land-use type and grain-size fraction.

[n, number of samples; mm, millimeters; coarse, greater than or equal to 

2 mm; medium, less than 2 mm greater than or equal to 0.125 mm; fine, less 

than 0.125 mm in diameter]

Street-solid yield, in pounds per curb-mile

Statistic Total Coarse Medium Fine

Multifamily

n = 65

Mean 740.1 301.0 346.9 63.6

Median 601.5 129.2 277.4 37.9

Minimum 168.8 11.7 95.1 6.1

Maximum 3,847.5 2,935.1 974.6 280.9

Commercial

n = 64

Mean 521.5 111.6 331.2 64.5

Median 466.7 65.1 305.0 60.7

Minimum 179.7 21.0 126.6 4.2

Maximum 1,471.0 707.3 918.7 307.2

Spatial Distribution of Street Solids

Distribution of material on street surfaces is highly variable and controlled by many factors including presence of 

berms or curbing, condition of street-surface texture, prevailing winds, traffic density, on-street parking, and parking 

controls. Sartor and Boyd (1972) and Pitt (1979) observed 

that on smooth streets with moderate to heavy traffic without 

on-street parking, about 90 percent of the material was located 

within 1 foot of the curb. Pitt (1979) also reported street dirt 

on rough-textured streets typically is distributed more evenly 

as more material is retained within cracks and pits on the 

surface. In addition, they reported on-street parking can act to 

buffer traffic action and prevailing winds to further limit consolidation of street solids near the curb. Seasonal effects also 

determine street solids distribution. This is demonstrated in 

areas with relatively cold winters requiring street maintenance 

during snow events in the form of deicers or sand. Although 

the Cambridge Department of Public Works (DPW) does not 

apply maintenance sand to their streets during snowstorms, 

maintenance sand tracked into the city from daily traffic and 

use of sand to improve traction on sidewalks and other pedestrian areas may be available to “wash on” to street surfaces. 

Selbig and Bannerman (2007) collected curb samples 

from 3 ft out from the curb in addition to the crown (or center 

lane). Their streets had minimal on-street parking, and they 

reported an even distribution of street material at the EOW 

such that the crown contained a greater proportion of material 

than the curb lanes; however, by early summer 75 percent of 

the street dirt was confined to within 3 ft of the curb. 

Table 7. Comparison of Cambridge, Massachusetts, street-solid yields by land-use type to those in other areas of the United States 

(Modified from Selbig and Bannerman, 2007).

[--, no data; all values in pounds per curb-mile]

Statistic Cambridge, 

Massachusetts

Madison, 

Wisconsin1

Champaign, 

Illinois2

Bellevue, 

Washington3

Seattle, 

Washington4

San Jose, 

California5

Baltimore, 

Maryland6 U.S. Nationwide7

Multifamily

Mean 740 614 408 815 970 310 645 391

Median 602 569 -- 705 1,060 -- -- --

Commercial

Mean 522 -- -- -- -- 509 -- 302

Median 467 -- -- -- -- -- -- --

1

Selbig and Bannerman, 2007.

2

Bender and Terstriep, 1984.

3

Pitt, 1985.

4

Seattle Public Utilities and Herrera Environmental, 2009.

5

Pitt, 1979.

6

Law and others, 2008.

7

Sartor and Boyd, 1972.
20 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11 Number of values Upper adjacent 75th percentile Median 25th percentile Lower detached

5

EXPLANATION

B. COMMERCIAL A. MULTIFAMILY

400200

100

4,0002,0001,000

10,000 12 31 16

Spring

Summer

Fall

EOW

Spring

Summer

Fall

EOW

5

Street-solid yield, in pounds per curb-mile

12 31 19 6

Figure 8. Seasonal and end-of-winter (EOW) street-solid yields, in pounds per curb-mile from streets in A, multifamily, and B, commercial land-use types, Cambridge, 

Massachusetts. Time periods represent samples collected during SPRING, May to June 2010; SUMMER, July to September 2010; FALL, October to December 2010; and EOW, March 2011.
Characterization of Street Solids 21

Three sets of street-solid distribution samples were 

collected on each street in Cambridge in July and October 

2010, and in March 2011, such that one portion of the 

composite represented a curb lane and a second composite 

represented the remaining center lane or crown of the street. 

July composite samples represented street-solids within 3 ft 

of the curb and the remaining street crown. About 57 percent 

of the total street-solids was found within 3 ft of the curb and 

about 43 percent of the total street-solids was found in the 

street crown. About 67, 55, and 63 percent of street solids 

from the coarse, medium, and fine grain-size fractions were 

within 3 ft of the curb, respectively. Within the crown, the 

distribution of street solids from coarse to fine grains were 

about 33, 45, and 37 percent, respectively. Samples were 

collected from the curb extending 9 ft towards the crown in 

October 2010. About 95 percent of total street solids were 

observed within 9 ft of the curb, and the remaining 5 percent 

resided within the crown. Distribution of street solids by 

grain size indicated 97, 91, and 94 percent of material in the 

coarse, medium, and fine grain-size fractions were within 9 ft 

of the curb, respectively. The remaining 3, 9, and 6 percent of 

the coarse to fine grain-size fractions were within the crown, 

respectively. EOW samples were collected 6 ft from the curb 

in March 2011, and about 74 percent of the total material was 

within this area. From coarse to fine grain-size fractions, 81, 

72, and 75 percent of street solids was within 6 ft of the curb, 

respectively. These samples suggest a fairly even distribution 

of street solids throughout the year in Cambridge on the 

smooth to rough-textured streets with heavy on-street parking. 

The most even distribution was observed within the two 

grain-size fractions greater than or equal to 0.125 mm, which 

represents more than 86 percent of the total mass of street 

solids on both multifamily and commercial streets.

Street-Solid Accumulation

Street-solid composite samples from each street were 

used to estimate the accumulation rate (build-up rate or deposition loading) of street solids on street surfaces by dividing 

the difference in total yields between successive samples 

before and after a rainstorm by the number of days between 

sampling events. Accumulation results for Mount Auburn 

Street were negative, indicating a loss of material with time 

rather than a buildup, although results from the five other 

streets were positive. Considering the additional street cleaning by mechanical-brush street cleaners observed outside the 

monthly schedule on this street, commercial accumulation-rate 

estimates exclude data from Mount Auburn Street, which may 

exhibit a negative bias resulting from additional street cleaning activity. 

Accumulation rates from streets in each land-use type 

are shown in figure 9. Overall accumulation patterns were 

similar between land-use types by grain-size fraction and total 

yield. Median total accumulation rates were 33 and 

22 lbs/curb-mi/day, and ranged between -43 to 84 and -23 to 

308 lbs/curb-mi/day for multifamily and commercial land-use 

streets, respectively (extreme values truncated in figure 9). 

Median multifamily accumulation rates were largest within 

the medium grain-size fraction at about 19 lbs/curb-mi/day, 

though the coarse and fine grain-size fractions accumulate 

similarly at about 7 lbs/curb-mi/day. Median commercial accumulation rates for the medium grain-size fraction were about 

15 lbs/curb-mi/day, the fine grain-size fraction was about 

6 lbs/curb-mi/day and the coarse grain-size fraction was the 

smallest at about 2 lbs/curb-mi/day. 

The average accumulation of street solids on the study 

streets increased quickly within a few days of a street cleaning 

or rainstorm in both multifamily and commercial land-use 

types (fig. 10). The drop in yields after nearly two days 

on streets in both plots is attributed to sample loss during 

processing that resulted in an average accumulation value 

based on only one street for multifamily and commercial 

streets. These results indicate that the street solids on 

multifamily and commercial streets in Cambridge can 

accumulate to near median yields within 1 to 3 days after the 

streets are cleaned or following a rainstorm (fig. 10). After this 

steep increase, the estimated street-solid yield in each land-use 

type remained somewhat consistent. The overall accumulation 

pattern of these data is similar to the early research of Sartor 

and Boyd (1972) for both land-use types with a steep increase 

within the first few days of a washoff or street-cleaning event, 

then increasing more slowly and reaching maximum yields in 

about 5 days. Yields also became constant after about 7 days 

in Bellevue, Washington, an area where rainfall occurs about 

every 3 days (Pitt, 1985). Burton and Pitt (2002) suggest that 

yields of street solids on roadways in areas such as Bellevue, 

Wash., remain close to the initial yields and do not increase 

with time. 

Street-Solid Washoff

The washoff of street solids from roadway surfaces and 

mobilization of local soils adjacent to streets are dependent 

on the initial load, and the rainfall intensity or volume of 

stormwater on the roadway to loosen dirt and other solids 

from the pavement and transport it off/from the street (Pitt and 

others, 2004). Pitt and others (2004) also suggest that urban 

stormwater runoff during small and less intense rainstorms 

represent most of the solid load resulting from wear of the 

road surface and the deposition of traffic-related materials. 

Furthermore, Pitt and others (2004) reported that washoff is 

affected by distribution of street solids on road surfaces and 

extent of armoring (or the sheltering of smaller particles by 

larger ones). 

Street-solid composite samples were collected before 

and after rainstorms. The time between the end of a rainstorm 

and when samples were collected varied, and percent washoff 

from streets in the two land-use types was estimated based 

on samples collected between 3 and 23 hours of the end of 

six rainstorms. The narrow window between the collection 
22 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11 of of of of of of of of 16 16 16 16 11 11 11 11 14 14 14 14 9 9 9 9

Coarse

Medium

 Fine

Accumulation rate, in pounds per curb-mile per day

A. MULTIFAMILY B. COMMERCIAL

 Total

Coarse

Medium

 Fine

 Total

-20

0

80604020

100

Number of values used as compared to total number of valuesTruncated 10th and 90th valuesUpper adjacent75th percentileMedian25th percentileLower detached

5

of

10

EXPLANATION

Figure 9.

Accumulation rates by grain-size fraction and total solids, in pounds per curb-mile per day from streets in A, multifamily and B, commercial land-use types, 

Cambridge, Massachusetts. COARSE represents all solids greater than or equal to 2 mm; MEDIUM, less than 2 mm to greater than or equal to 0.125 mm; FINE, less than 0.125 mm in diameter. TOTAL represents sum of all grain-size fractions. COARSE solids include all organic material and gravel up to about 50 mm in diameter. Commercial plots do not include data from Mount Auburn Street.
Characterization of Street Solids 23

Street-solid yield, in pounds per curb-mile

Days since last rain or street cleaning

0

100

200

300

400

500

600

700

800

900

1,000

0 2 4 6 8 10 12 14

0

100

200

300

400

500

600

700

800

900

1,000

Coarse ≥ 2mm

Medium < 2mm to ≥ 0.125mm

Fine < 0.125mm

Total

Sartor and Boyd

EXPLANATION

Multifamily

Commercial

Figure 10. Street-solid yield by grain-size fraction and total yield, in pounds per curb-mile per day as a function 

of time in days since the last rain or street cleaning on streets in multifamily and commercial land-use types, 

Cambridge, Massachusetts. U.S. nationwide residential and commercial results from Sartor and Boyd (1972) also 

are shown. Commercial plots do not include data from Mount Auburn Street.
24 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

of prestorm and poststorm samples likely eliminated effects 

of unscheduled street cleaning on Mount Auburn Street. The 

average amount of street solids removed from the roadway by 

rainfall (washoff) was calculated by subtracting the difference of street-solid mass in total composite samples and by 

grain-size fraction before and after a rainstorm for six sample 

pairs. Total storm volumes and rainfall intensities based on 

the Cambridge DPW rain gage on Hampshire Street ranged 

between 0.32 to 1.71 inch and 0.027 to 0.185 inches per hour 

(in/hr), respectively. Net increases of street solids following 

rainstorms result in negative washoff values. One of the six 

composite sample pairs bounds a rainstorm during heavy leaffall season, which may explain the negative washoff values. 

Deposition of leaves/seeds/woody debris from trees, dirt, soils, 

and other debris transported from impervious surfaces or saturated pervious surfaces adjacent to the street surface, and dirt 

and soils tracked in from construction vehicles (track-out) are 

possible sources that may increase the amount of street solids 

after a rainstorm. Every effort was made to avoid areas with 

unusual loading or obvious additional street solids from active 

construction sites (fig. 2) during sampling. 

The percent washoff of street solids from each street in 

terms of grain-size fraction, and an average percent washoff of 

all three grain-size fractions from each street as a result of the 

six rainstorms are presented as boxplots in figure 11. Percent 

washoff of solids from streets in multifamily and commercial 

areas increased similarly with decreasing grain-size. Median 

average street-solid washoff also was similar between land-use 

types at about 36 and 42 percent for multifamily and commercial streets, respectively. 

An average percent washoff for each grain-size fraction 

and an average total washoff from both land-use types for 

each of the six storms were calculated and plotted as a function of rainfall volume and intensity (fig. 12). Plots in figure 

12A show the percent washoff is generally highest in the fine 

grain-size fraction, and there were two instances with negative 

washoff of primarily coarse street solids on multifamily streets 

and one instance of negative washoff of fine size fraction 

street solids on commercial streets. Observed storm intensities 

in figure 12B were less than 0.20 in/hr, and the highest percent 

washoff values are seen in the fine fraction at intensities less 

than 0.10 in/hr. Negative washoff of primarily coarse street 

solids are observed only from streets in the multifamily landuse type and washoff occurs at lower intensities compared to 

negative washoff from streets in commercial land use.

Regenerative-Air Street Cleaner Removal 

Efficiency

The removal efficiency of a TYMCO Dustless Sweeping 

Technology-6 (DST-6) regenerative-air street cleaner, herein 

referred to as the “RA street cleaner,” was determined by comparing the difference between street-solid composite samples 

collected before and after the streets were cleaned by a single 

pass of the machine in multifamily and commercial land-use 

areas. 

The difference between pre- and post-median yields of 

total street solids from multifamily streets was 82 and 78 percent on commercial streets (table 8). Removal efficiency of the 

RA street cleaner decreased with smaller grain-size fractions, 

and was nearly the same for streets in both land-use types. 

The median percent removal efficiency for the machine on 

multifamily and commercial streets was 92, 83, and 53 percent, and 92, 79, and 51 percent for the coarse, medium, and 

fine grain-size fractions, respectively. Negative values, or 

net increases in material were occasionally observed within 

the fine grain-size fraction. However, this typically occurred 

on streets with rough surfaces, and is possibly a result of the 

action of the street cleaner’s gutter broom removing coarse 

dirt and other material from cracks and holes near the curb, 

exposing finer material in addition to fine-grained material left 

behind by the wet gutter broom. Median street-solid yields 

before a single RA street cleaner pass within 9 ft of the curb 

on multifamily and commercial streets were 735 and 521 lbs/

curb-mi, respectively. Street-solid yields before street cleaning ranged from about 269 lbs/curb-mi in both land-use types 

to 1,685 to 1,377 lbs/curb-mi on multifamily and commercial 

streets, respectively (fig. 13). Median residual yields after the 

street was cleaned were nearly identical for streets in both 

land-use types at about 100 lbs/curb-mi, but ranged between 

18 and 513 lbs/curb-mi, and 46 and 222 lbs/curb-mi on multifamily and commercial land-use streets, respectively. Individual removal efficiency (or single-sided) sample dates and 

resulting masses and yields for streets in both multifamily and 

commercial land-use types are seen in appendix table 1–16 (on 

CD–ROM at back of report).

A residual yield of street solids always remained on the 

street surface following a single street cleaner pass in the 

study sections as a function of the initial yield. Evaluation 

of the removal efficiency data based on season, individual 

streets, land-use type, street condition, and traffic volume did 

not present any clear patterns, and resulted in poor relations. 

Closer inspection of available removal efficiency data indicate 

a nonnormal, cloud-like pattern without a strong linear relation, whether or not the data was corrected for the whole street 

or not. The Kendall-Thiel robust line, described by Helsel and 

Hirsch (2002), is a nonparametric regression technique that 

is less affected by outliers and nonnormality of residuals that 

commonly characterize hydrologic datasets (Granato, 2006). 

The Kendall-Thiel Robust Line program (KTRLine-version 

1.0; Granato, 2006) was used to develop a regression of 

residual yield (post-street cleaning) and initial yield (prestreet cleaning) or productivity function data corrected for the 

whole street for the regenerative-air street cleaner. The slope 

is calculated as the median of all possible pairwise slopes and 

the intercept is calculated so that the line will run through the 

median of the input data (Granato, 2006). The slope of the 

regression between street-solid yield before and after street 

cleaning is low, and the data indicate that the efficiency of the 

street cleaner increased with increasing initial yields, but also 
Characterization of Street Solids 25

Coarse Medium Fine Average Coarse Medium Fine Average

 Washoff, in percent

A. MULTIFAMILY B. COMMERCIAL

Upper adjacent75th percentileMedian25th percentileLower detached

5

of

10

EXPLANATION

-50

50

0

150100

of of of of of of of of

14 14 14 14 15 15 15 1512 12 12 12 13 13 13 13

Number of values used as compared to total number of valuesTruncated 10th and 90th values

Figure 11. Percent washoff of street solids by grain-size fraction estimated for storms with a recorded rainfall volume range of 0.32 to 1.71 inches, from streets in A, multifamily and B, commercial land-use types, Cambridge, Massachusetts. COARSE, represents all solids greater than or equal to 2 mm; MEDIUM, less than 2 mm to greater than or equal to 0.125 mm; FINE, less than 0.125 mm in diameter. AVERAGE represents the range of average percent washoff for each street. COARSE solids include all organic material and gravel up to about 50 mm in diameter.
26 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

-100

-80-60-40-2

00

20406080

100

Coarse ≥ 2mmMedium < 2mm to ≥ 0.125mmFine < 0.125mmTota

EXPLANATION

l

Coarse ≥ 2mmMedium < 2mm to ≥ 0.125mmFine < 0.125mmTota

EXPLANATION

l

Average washoff, in percent

Total precipitation, in inches

A. Total rain depth B. Rainfall intensity 

-100

-80-60-40-2

00

20406080

100

0.0 0.5 1.0 1.5 2.0 2.5

MULTIFAMILY

COMMERCIAL

MULTIFAMILY

COMMERCIAL

Precipitation intensity, in inches per hour

0.00 0.05 0.10 0.15 0.20

Figure 12.

Average percent washoff for each grain-size fraction, and average total washoff for storms with a recorded rainfall volume range of 0.32 to 1.71 inches as a function 

of A, total rain depth, and B, rainfall intensity from streets in multifamily and commercial land-use types, Cambridge, Massachusetts.
Characterization of Street Solids 27

Table 8. Average, median, maximum, and minimum removal 

efficiency, in percent, of a regenerative-air street cleaner on 

multifamily and commercial land-use streets in Cambridge, 

Massachusetts.

[Negative values indicate an increase in material following a single regenerative-air street-cleaner pass; n, number of samples; mm, millimeter; coarse, 

greater than or equal to 2 mm; medium, less than 2 mm greater than or equal 

to 0.125 mm; fine, less than 0.125 mm in diameter]

Removal efficiency, in percent

Total Coarse Medium Fine

Multifamily

n = 33

Average 83.3 89.5 82.6 49.8

Median 86.2 95.8 88.5 65.9

Maximum 98.3 99.8 96.9 94.9

Minimum 35.7 75.1 42.8 -87.1

Commercial

n = 39

Average 78.2 92.4 79.4 48.6

Median 79.7 94.1 80.1 63.6

Maximum 92.6 99.3 95.9 92.8

Minimum 43.8 63.9 45.3 -86.7

left a consistent residual yield regardless of the initial streetsolid yield. The slope (0.066), and y-intercept (69.57) of the 

KTRLine (fig. 14) represent the productivity function coefficients applied in the SLAMM model to simulate the performance of the regenerative-air street cleaner evaluated in 2010.

Street-Solid Chemistry

Constituents on street surfaces in urban areas may come 

from a variety of sources and may vary depending upon 

the age of the materials used for construction. For example, 

fiberglass and asphalt roof types are known to have better 

runoff quality than slate tile, rubber, or galvanized metal 

(Davis and others, 2000). Average concentrations of copper 

(Cu), Pb, and zinc (Zn) in samples of bulk rainfall collected 

from a rubberized roof in Ipswich, Mass., were 2.8, 5.9, and 

7.9 micrograms per liter (μg/L), respectively (Zimmerman 

and others, 2010). The concentrations of total P in bulk 

rainfall were 0.01 milligrams per liter (mg/L). Average 

concentrations of Cu, Pb, and Zn in samples of rainfall runoff 

from the rubberized roof were about 53, 692, and 514 μg/L, 

respectively, and about 0.10 mg/L was reported for total P. In 

addition, roofing and siding materials from buildings has been 

associated with substantial concentrations of Cd, Cu, Pb, and 

Zn (Davis and others, 2000).

Smith (2010) conducted an extensive study of stormwater 

runoff from Massachusetts highways of various traffic densities. In addition to exhaustive stormwater sampling, samples 

of maintenance sand, maintenance salt (sodium chloride), 

liquid calcium chloride, berm soil, and grass clippings were 

submitted for analysis of elements, polyaromatic hydrocarbons, and phthalates. Grasses were determined to possess 

relatively high concentrations of Ca, K, and P. Washed off 

solids greater than 0.250 mm in diameter, including sands and 

gravels, but consisting mostly of leaves, were also relatively 

high in these elements (Smith, 2010). Average concentrations 

of P, other elements, and suspended sediments in composite 

samples of highway runoff were reported to be 3 to 11 times 

greater in winter runoff compared to runoff during warmer 

months (Smith, 2010). The large difference between winter 

and nonwinter runoff concentrations in highway runoff was 

attributed primarily to the application of maintenance sand. 

Although maintenance sand constituent concentrations were 

small, the large amount of sand applied during the winter 

resulted in large increases of many elements in runoff, including a 94-percent increase in winter P concentrations (Smith, 

2010). Low temperatures, increased vehicle component wear, 

and entrained material in snowbanks are all additional sources 

of increased winter loading. Smith (2010) reported exhaust 

emissions from gasoline engines at highway speeds represented less than 3 percent of P concentrations in stormwater 

runoff, background soils accounted for about 37 percent of the 

median P concentration, and that erosion or presence of soils 

onto the paved surface could be a large source of P and other 

elements in stormwater runoff. 

Urban and suburban traffic patterns have more frequent 

stops and accelerations. This type of vehicle operation is associated with less efficient combustion by gasoline engines and 

increased vehicle component and road wear. These conditions 

in urban and suburban areas may result in greater concentrations of Cu and Zn associated with brake and tire wear (Davis 

and others, 2000). Average emission rates of Cr, Cu, Nickel 

(Ni), and Pb were similar to major particulate-associated 

polyaromatic hydrocarbon (PAH) emission rates, but P, Fe, 

and Zn were about 6 to 38 times greater than their respective 

PAH emission rates (Cadle and others, 2001).

Median concentrations of organic carbon, P, and 31 other 

elements in street-solid composite samples from multifamily 

and commercial streets in Cambridge, Mass., were normalized by the mass of the respective grain-size fraction. Median 

total-recoverable concentrations and respective standard 

deviations of all CTC composite samples of street solids for 

each grain-size fraction for the two land-use types are listed in 

table 9 (in back of report). Concentrations of organic carbon 

and 12 elements were greater in composite samples collected 

from multifamily streets than in composite samples collected 

from commercial streets. Median concentrations of organic 

carbon and total P were about 35 and 29 percent greater than 

the median concentrations calculated for composite samples 

collected from commercial streets. Individual total-recoverable 

concentrations of street-solid composite samples for streets in 
28 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

x

o

x

x

0

500

1,000

1,500

2,000

2,500

40 40 43 43

PRE

POST

Street-solid yield, in pounds per curb-mile

POST

PRE

A. MULTIFAMILY B. COMMERCIAL

Figure 13. Street-solid yields before (PRE) and after (POST) a single pass of a regenerative-air street cleaner on streets in A, multifamily 

and B, commercial land-use types, Cambridge, Massachusetts.

both multifamily and commercial land-use types are seen in 

appendix tables 1–17 and 1–18, respectively (on CD–ROM at 

back of report).

The total mass of constituents in composite samples 

collected from multifamily streets also were somewhat greater 

than the total mass of constituents in composite samples 

collected from commercial streets (table 9, in back of report). 

The total mass of constituents generally increased with 

decreasing grain size, except for organic carbon, Ca, K, Mg, 

P, and strontium (Sr), in samples from streets in both land-use 

types. These constituents had higher concentrations in the 

coarse size fraction.

Concentrations of organic carbon, Ca, and K, from 

the medium fraction also were greater than concentrations 

in the fine fraction, although the difference was slightly 

greater in the multifamily street solid composite samples. 

Concentrations of organic carbon, Ca, K, P in samples of 

unwashed leaves collected from residential streets were 

higher than finer grain-size fractions of street solids. Similar 

concentrations of these constituents also were found in 

bulk samples greater than 0.250 mm in diameter, consisting 

predominantly of leaves, collected at the outlet of a catch 

basin along Massachusetts highways (Smith, 2010). About 

13.3 and 1.5 percent of the total P mass is within the finest 

fraction (less than 0.125 mm) for multifamily and commercial 

land-use types, respectively. The total mass of organic carbon 

and P in composite samples of street solids from multifamily 

streets was about 68 and 75 percent greater than the mass 

of the constituents in composite samples collected from 

commercial land-use streets, respectively. The mass of P on 

multifamily streets was greater than that on commercial streets 

by about 1.4 and 11.5 times in the medium and fine grain-size 

fractions, respectively. Total P on commercial streets was 

about 0.8 times (or about 20 percent) greater than total P on 

multifamily streets within the coarse grain-size fraction. About 

87 and 98 percent of the total P mass was observed within 

material greater than very fine sand (greater than 0.125 mm in 

diameter), for streets in multifamily and commercial, landuses, respectively.
Characterization of Street Solids 29

y = 0.066x + 69.566

R2 = 0.9737

10

100

1,000

100 1,000 10,000

Residual yield, in pounds per curb-mile

Initial yield, in pounds per curb-mile

Kendall-Theil Robust Line

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000

no-change line

A

B

Figure 14. A, Removal efficiency plot of a regenerative-air street cleaner making a single pass on streets with smooth to rough 

street-surface conditions and heavy on-street parking with monthly parking controls, in multifamily and commercial land-use types 

Cambridge, Massachusetts. All data below the 1:1 no-change line represent reductions in street-solid yields. B, Productivity function 

(green dotted line) of the regenerative-air street cleaner using the Kendall-Theil Robust Line (KTRLine version 1.0), where 0.066 is the 

slope and 69.566 is the y-intercept.
30 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

Total P yields (fig. 15, table 10) generally follow the pattern of street solid yields (fig. 8, table 10). Following spring 

cleaning, P yields are reduced to low levels by street cleaning 

and washoff events during the spring and summer. Yields of 

P increase in autumn during leaf-fall season and maximum 

yields of P were measured on streets in both land-use areas at 

this time (fig. 15, table 10); however, median yields of P were 

highest at the EOW in March 2011 (fig. 15).

Accumulation Rate Estimates of Organic Carbon 

and Elements

Accumulation rate estimates were calculated for concentrations of organic carbon, total P, and 31 elements by first 

normalizing by mass to determine the load of constituents 

in grams. The resulting mass was then used to determine the 

yield of each constituent in lbs/curb-mi using the process 

described in the “Street-Solid Mass” section. Resulting yields 

were divided by the total number of days between sampling 

events to further obtain estimates of constituent accumulation 

rates in lbs/curb-mi/day. Average, median, maximum, and 

minimum accumulation rates for each constituent in streetsolid samples were estimated for each grain-size fraction by 

land-use type (table 11, in back of report). Sample concentrations from commercial streets do not include Mount Auburn 

Street data. Median concentrations of organic carbon and element accumulation rates for the multifamily land-use type are 

greater than those observed on commercial land-use streets for 

24 of the 33 constituents for the coarse and fine fractions, and 

for 14 of the 33 constituents for the medium fraction. Median 

accumulation rates from coarse to fine in samples from the 

multifamily land-use type were greater than those from streets 

in the commercial land use for 31, 24, and 16 of the 33 constituents, respectively (table 9, in back of report). 

Accumulation rates of most constituents were generally smallest within the coarse grain-size fraction, except for 

yields of organic carbon. The largest accumulation rates for 

most constituents appear to vary between the medium and 

fine grain-size fractions (table 10). Accumulation rates from 

streets in multifamily land-use areas were generally greater 

than streets in commercial land-use areas. In particular, the 

median accumulation rates of Cr, Cu, P and Pb in total solids 

from streets in multifamily areas were about 1.9, 1.4, 5.0, and 

12.7 times greater than those from streets in commercial areas, 

respectively; however, median accumulation rates of Cd, Ni, 

and Zn from streets in commercial areas were greater than the 

those from multifamily streets by about 2.0, 1.9, and 1.5 times, 

respectively. Kaufman and others (2011) also reported high 

concentrations of metals including Pb in residential as compared to commercial land-use types in urban areas.

The median accumulation rate estimated for organic 

carbon for all grain-size fractions from multifamily streets 

was 1.4 lbs/curb-mi/day and ranged between about -10 to 

17 lbs/curb-mi/day. The median accumulation rate and range 

for organic carbon for all grain-size fractions in commercial 

data was 0.067 lbs/curb-mi/day, and ranged between about 

-12 to 4 lbs/curb-mi/day. Accumulation rates of organic carbon 

were highest within the medium grain-size fraction, followed 

by the coarse grain-size fraction for both land-use types 

reflecting the dominant effect of larger organic debris within 

the coarser fractions. 

The median total P accumulation rate for total solids 

in multifamily data was 0.002 lbs/curb-mi/day and ranged 

between about -0.017 and 2.36 lbs/curb-mi/day. Accumulation rates of P increased from coarse to fine grain-size fractions. From coarse to fine, multifamily median accumulation 

rates of P are about 0.001, 0.004, and 0.010 lbs/curb-mi/day, 

respectively. The median accumulation rate for total P for 

total solids in commercial data was 0.0004 lbs/curb-mi/day, or 

about 5 times less than the multifamily accumulation rate, and 

ranged between about -0.003 to 0.030 lbs/curb-mi/day. Median 

commercial accumulation rates of total P in the coarse to fine 

grain-size fractions are about 0.0001, 0.004, and 0.0001 lbs/

curb-mi/day, respectively. Although the accumulation rate of 

total P for the medium size fraction was nearly the same on 

streets in both land-use types, the accumulation rate on multifamily streets in the coarse and fine size fractions were about 

11 and 82 times greater than those on commercial streets.

Washoff Estimates of Organic Carbon and 

Elements

The amount of washoff for each constituent was determined by multiplying the element concentrations by their 

respective mass of each grain-size fraction from the six 

composite sample pairs. Table 12 (in back of report) shows the 

average, median, maximum, and minimum percent washoff 

of organic carbon and 32 elements for each grain-size fraction 

within the multifamily and commercial land-use types. Median 

percent washoff for organic carbon and elements on streets in 

multifamily land-use areas was greater than those on commercial land-use streets for 24 of the 33 constituents in the coarse 

and fine grain-size fractions, and for 14 of the 33 constituents 

in the medium grain-size fraction. Negative washoff was 

observed for several rainstorms in all grain-size fractions, but 

was most common in the coarse and fine grain-size fractions. 

These rainstorms likely are associated with organic debris and 

“washon” from other source areas onto the streets. 

Median total washoff for total P on streets in multifamily 

areas was 58 percent and ranged between about -1,120 to 

93 percent. Median percent washoff of total P from streets in 

multifamily areas was about 39 percent for the two coarser 

fractions greater than 0.125 mm, and about 76 percent for the 

fine grain-size fraction. Median washoff of total P from streets 

in commercial areas was about 48 percent and ranged between 

about -214 to 99 percent. Median washoff of P from coarse 

to fine grain-size fractions are about 34, 51, and 77 percent, 

respectively.
Characterization of Street Solids 31

xxx

xxxx

ooo

xx

x

ooooxxx

ooo

x

35 105 47 14 34 100 57 18

Phosphorus yield, in pounds per curb-mile

A. MULTIFAMILY B. COMMERCIAL

Spring

Summer

Fall

EOW

6543

21

0

Spring

Summer

Fall

EOW

Number of valuesUpper detachedUpper outsideUpper adjacent75th percentileMedian25th percentileLower detachedLower outsideLower adjacent

EXPLANATION

18

xx

Figure 15. Total phosphorus yields, in pounds per curb-mile, by season from streets representing predominantly A, multifamily and B, commercial land-use types in Cambridge, Massachusetts. Time periods represent composite samples collected during: SPRING, May to June 2010; SUMMER, July to September, 2010; FALL, October to December, 2010, and EOW, March 2011.
32 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

Table 10. Street-solid composite sample collection dates, sample type, antecedent rain conditions, sampled storm volume, street-solid 

yield, and total phosphorus yields from streets in Cambridge, Massachusetts. 

[Street-solid yields from single-side (SS) sample composites are estimated; in, inches; lb/curb-mi, pounds per curb-mile; P, phosphorus; SS, single side; CTC, 

curb-to-curb; --, no data]

Sample 

date

Sample 

type

24-hour 

precipitation depth 

(in)

48-hour 

precipitation depth 

(in)

72-hour 

precipitation depth 

(in)

Sampled 

storm depth 

(in)

Multifamily Commercial Multifamily Commercial

Street-solid 

yield

(lb/curb-mi)

Street-solid 

yield

(lb/curb-mi)

Total P yield

(lb/curb-mi)

Total P yield

(lb/curb-mi)

05/11/10 SS 0.00 0.00 0.00 0.00 1,077.6 -- -- --

05/12/10 SS 0.00 0.00 0.00 0.00 286.2 -- -- --

05/13/10 SS 0.00 0.00 0.00 0.00 -- 529.9 -- --

05/14/10 SS 0.45 0.00 0.00 0.00 -- 198.2 -- --

05/18/10 CTC 0.00 0.00 0.00 0.00 476.1 388.8 -- --

05/19/10 CTC 1.48 0.00 0.00 1.54 233.0 198.6 -- --

06/08/10 SS 0.00 0.00 1.38 0.00 630.2 -- -- --

06/09/10 SS 0.05 0.00 0.00 0.00 220.0 -- -- --

06/11/10 SS 0.00 0.13 0.05 0.00 -- 529.2 -- --

06/12/10 SS 0.33 0.00 0.13 0.00 -- 162.1 -- --

06/24/10 CTC 0.21 0.11 0.00 0.00 504.4 466.2 0.28 0.14

06/24/10 CTC 0.21 0.11 0.00 0.32 298.8 306.1 0.21 0.12

07/07/10 CTC 0.00 0.00 0.00 0.00 819.7 565.3 0.57 0.21

07/08/10 SS 0.00 0.00 0.00 0.00 -- 553.0 -- --

07/09/10 SS 0.00 0.00 0.00 0.00 -- 182.2 -- --

07/13/10 SS 0.14 0.01 0.05 0.00 568.4 -- -- --

07/14/10 SS 0.01 0.05 0.14 0.00 179.3 -- -- --

07/28/10 CTC 0.00 0.00 0.00 0.00 839.4 628.2 0.54 0.23

07/29/10 CTC 0.05 0.00 0.00 0.05 637.3 419.2 0.37 0.12

08/10/10 SS 0.06 0.00 0.00 0.00 760.1 -- -- --

08/11/10 SS 0.00 0.06 0.00 0.00 185.0 -- -- --

08/12/10 SS 0.00 0.00 0.06 0.00 -- 692.8 -- --

08/13/10 SS 0.00 0.00 0.00 0.00 -- 195.4 -- --

08/26/10 CTC 0.00 3.38 1.01 0.00 379.6 542.0 0.02 0.02

08/27/10 CTC 0.00 0.00 3.38 0.00 268.6 274.9 0.01 0.01

08/30/10 CTC 0.00 0.00 2.39 0.00 613.1 664.7 0.03 0.03

09/01/10 CTC 0.00 0.00 0.00 0.00 697.8 635.7 0.04 0.03

09/03/10 CTC 0.00 0.00 0.00 0.00 752.7 937.5 0.47 0.37

09/05/10 CTC 0.00 0.54 0.00 0.54 747.6 720.3 0.46 0.30

09/08/10 SS 0.48 0.00 0.00 0.00 410.2 -- -- --

09/09/10 SS 0.00 0.48 0.00 0.00 98.2 667.6 -- --

09/10/10 SS 0.00 0.00 0.48 0.00 -- 160.6 -- --

09/27/10 CTC 0.12 0.00 0.00 0.00 618.9 356.3 0.49 0.19

09/29/10 CTC 0.98 0.12 0.00 1.10 542.8 248.7 0.35 0.11

10/02/10 CTC 0.95 0.02 0.00 0.95 667.6 387.7 0.42 0.21

10/08/10 SS 0.00 0.00 1.66 0.00 -- 639.0 -- --

10/09/10 SS 0.00 0.00 0.00 0.00 -- 138.7 -- --

10/12/10 SS 0.06 0.00 0.00 0.00 1,264.9 -- -- --

10/13/10 SS 0.00 0.06 0.00 0.00 213.9 -- -- --

11/04/10 CTC 1.07 0.00 0.00 0.00 2,433.6 1,015.9 2.96 2.39

11/06/10 CTC 0.00 0.64 1.07 0.00 1,445.4 567.3 0.98 0.29

11/16/10 CTC 0.05 0.00 0.00 0.00 505.3 508.9 0.48 0.22

11/18/10 CTC 0.03 1.23 0.05 1.28 727.2 489.2 0.76 0.25

11/30/10 CTC 0.00 0.00 0.00 0.00 871.3 716.1 0.92 0.32

12/02/10 CTC 0.57 0.00 0.00 0.57 666.6 289.1 0.53 0.10

12/08/10 SS 0.00 0.00 0.00 0.00 808.6 652.2 -- --

12/09/10 SS 0.00 0.00 0.00 0.00 127.7 146.8 -- --

03/04/11 CTC 0.00 0.00 0.00 0.00 2,588.1 4,310.1 1.24 1.24

03/08/11 CTC 0.00 0.71 0.00 0.71 2,639.4 5,266.7 1.52 1.61
Potential Reductions of Street Solids and Phosphorus Achievable by Street Cleaning 33

Estimates of Regenerative-Air Street Cleaner 

Removal of Organic Carbon and Elements

Percent reductions of constituent load on streets, as 

a result of a single pass from the RA street cleaner, were 

estimated by using the median values of each constituent 

measured in 48 to 72 pre- and post-RA street cleaner 

composite samples of street solids formulated to represent 

the constituent mass for spring, summer, and fall street-solids 

(table 9, in back of report). The median percent reduction in 

total yields and three grain-size fractions for organic carbon 

and 32 elements from seasonal samples of pre- and poststreet cleaner operation composite samples for multifamily 

and commercial, respectively, is shown in table 13 (in 

back of report). Percent reductions generally decrease with 

decreasing grain size, with slightly less removal of constituent 

mass during the spring and summer months. This likely is a 

reflection of lower street-solid yields available for removal 

during the summer compared to the larger EOW cleanup and 

autumn leaf-fall yields. Percent reductions for total samples 

are greater on multifamily streets in all seasons for all or 

nearly all constituents. Percent reductions from multifamily 

streets were greater than those on commercial streets in all 

seasons for nearly all constituents in coarse and medium grainsize fractions with the exception of the coarse size fraction in 

the spring and the medium size fraction in the fall where about 

one-half of constituent reductions are greater on commercial 

streets. Nearly all constituent reductions are greater on 

commercial streets in the fine grain-size fraction for summer 

and fall composites, and for about two-thirds of constituents in 

the spring fine fraction. Negative values indicate an increase 

in the mass of a constituent following street cleaner use, and 

are seen almost entirely in the less than 0.125 mm grain-size 

fraction from multifamily streets in the fall composite results 

(table 13, in back of report). Net increases within the fine 

grain-size fraction are seen for tin (Sn), Pb, Ni, Cu, chromium 

(Cr) and arsenic (As). The range of reductions on multifamily 

streets for all constituents is between 50 and 98 percent during 

the spring, -37 and 100 percent for the summer, and -1,050 and 

99 percent for the fall. Commercial street reductions indicated 

one negative value for cobalt (Co) within the coarse grain-size 

fraction for the spring. Spring, summer, and fall reductions of 

all constituents ranged between -8 to 98, 14 to 99, and 60 to 

99 percent, respectively. 

Median total P reductions for total samples were 82 and 

62 percent on streets in multifamily and commercial land-use 

types, respectively. Percent reductions generally increased 

with increasing grain size for both land-use types. Multifamily street reductions from coarse to fine were about 94, 86, 

and 64 percent in spring composites, 100, 99, and 97 percent 

in summer composites, and 96, 93, and 66 percent in fall 

composites. Reductions of total P on commercial streets from 

coarse to fine grain-size fractions were 96, 73, and 63 percent, 

respectively, in the spring, and 99, 97, and 98 and 97, 89, and 

79 percent, respectively, in summer and fall. Total-recoverable concentrations for pre- and post-street cleaner seasonal 

composite samples for streets in both multifamily and commercial land-use types are seen in appendix tables 1–19 and 

1–20, respectively (on CD–ROM at back of report). 

Potential Reductions of Street Solids 

and Phosphorus Achievable by Street 

Cleaning

Potential reductions in P associated with various street 

cleaning practices were simulated for a predominantly commercial land-use subcatchment in Cambridge, Mass., that 

ultimately drains to the lower Charles River. Street-solid data 

collected as part of this study and geographic information provided by the city of Cambridge and other sources were used to 

develop the model specifically for the study area. Street-solid 

washoff and total P concentration data collected as part of this 

study were not used in the model.

The Source Loading and Management Model for 

Microsoft Windows (WinSLAMM, referred to as SLAMM) 

version 9.4.0 (Pitt and Voorhees, 2002) is capable of 

continuously simulating stormwater runoff volume, loads of 

suspended sediments and other constituents, and the effects of 

stormwater-control measures. SLAMM has been successfully 

used to evaluate the performance of many types of stormwater 

control measures, including street cleaning, in locations across 

the United States and Canada. A more complete description of 

SLAMM and the input data used for the following simulations 

are in appendix 1 (included in accompanying CD–ROM).

Version 9.4.0 of SLAMM does have several limitations, 

including the inability to simulate base flow or snowmelt 

conditions, evaluate in-stream processes that affect constituent 

mass, or model erosion from pervious areas and construction 

sites. The model also uses simplified drainage system routing compared to the detailed water routing through certain 

stormwater control measures such as grass swales or detention ponds, and it cannot currently (ver 9.4.0) simulate rural 

areas effectively or run design storm analyses. The model has 

limited particle size information representing leaf matter and 

other organic debris and model runs appeared insensitive to 

seasonal effects such as leaf-fall.

Description of Commercial Land-Use 

Subcatchment

The subcatchment representing mostly commercial land 

use was selected for this study because of the existing level, 

flow, and constituent loading data at its outfall that was available from previous USGS studies (Breault and others, 2002; 

Zarriello and others, 2002) and is shown in figure 16. In addition, street-solid data were collected from streets in and around 

this subcatchment (fig. 2). Massachusetts Avenue and Mount 

Auburn Street are the two major routes that cross the basin, 
34 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

0 50 100 150 200 METERS

0 164 328 492 656 FEET

MASSACHUSETTS AVENUE

MOUNT AUBURN STREET

MASSACHUSETTS AVENUE

USGS ID: 01104677

BROADWAY

EXPLANATION

Commercial subcatchment 14.6 acres

Commercial subcatchment 21.8 acres

USGS flow and water-quality station 1999–2000

BANKS STREET

231,700

902,000 902,100 902,200 902,300 902,400 902,500 902,600

231,800 231,900 232,000 232,100 232,200

Northings and eastings in state plane meters. Basemap source, Mass GIS

Figure 16. Predominantly commercial land-use subcatchment in Cambridge, Massachusetts, and U.S. Geological Survey 

flow and water-quality monitoring station (USGS ID: 01104677), over a 0.5-meter color orthophoto obtained from MassGIS.
Potential Reductions of Street Solids and Phosphorus Achievable by Street Cleaning 35

and 24-hour traffic counts from 2002 were 11,670 and 9,860, 

respectively (city of Cambridge, written commun., 2009). 

Areas of Massachusetts Avenue are swept daily and weekly. 

The southern side of Mount Auburn Street has a dedicated 

bicycle lane that is typically swept weekly, while the northern side is swept monthly following the schedule for Streetcleaning district E (fig. 2). The street-cleaning schedule for 

both sides of Mount Auburn Street was changed to monthly 

between May and December 2010.

The outfall monitoring location for the commercial landuse station (USGS ID: 01104677) was a 3-ft diameter concrete 

storm drain located on Mount Auburn Street near Banks 

Street representing about 77 percent commercial land use and 

about 24 percent multifamily land use (fig. 16). During 1999 

and 2000, 14 dry- and 10 wet-weather sample events were 

collected from the 14.6 acre (0.023 mi2) subbasin (Breault 

and others, 2002); however, other areas may have contributed 

additional runoff to the monitoring location during some storm 

events and the resulting total area increased to 21.8 acres 

(Zarriello and Barlow, 2002). Zarriello and Barlow (2002) 

also determined the commercial subbasin contained about 

86 percent effective impervious area (EIA). Multifamily and 

institutional land-use types also are present in the 21.8 acre 

subcatchment; however, the model treats commercial and 

institutional land-uses similarly, therefore the effective 

commercial land-use area is about 64 percent (appendix 2, 

table 2–1).

Several limitations need to be considered when using 

the previous data: (1) level and velocity records from the site 

were incomplete, and estimation techniques were needed to 

fill these data gaps (Zarriello and Barlow, 2002); (2) Zarriello 

and Barlow (2002) used the limited level and discharge data 

from the commercial subbasins to develop rainfall-runoff 

relations from low-intensity storms with rainfall-runoff coefficients less than 1.0; (3) water-quality samples were collected 

in a flow proportional manner from a fixed location pointing 

downstream on the bottom of the drainage pipe. Under these 

conditions sand-sized particles (greater than 0.063 mm) generally form a vertical gradient (Smith, 2002; Bent and others, 

2000), and sampling in this manner potentially resulted in a 

large positive bias in total suspended-sediment concentrations 

and other constituents associated with high concentrations of 

coarse-grained sediment concentrations, such as P, also were 

potentially affected by the vertical gradient formed within the 

water column at the time of sampling.

Source Loading and Management Model

The general order of calibration begins with runoff, 

followed by particulate solids, and then constituents. Initial 

SLAMM simulations were evaluated using the special *.RAN 

file to guide modifications to the *.RSV file to match existing runoff data from 2000 (appendix 2, table 2–2). Only after 

acceptable agreement between simulated and observed runoff 

was achieved, were evaluations of simulated and observed 

street-solid yields from 2009–2011 possible. 

Relative Contributions of Source Areas

The special *.RAN file based on 62 years of precipitation 

record at Boston Logan Airport (COOP ID: 190770, appendix 2, table 2–2) yielded relative runoff contribution data seen 

graphically as cumulative columns for each of the three landuse types in the subcatchment in figure 17A–C. Multifamily 

(fig. 17A) runoff is dominated by roof source areas, which 

contribute about 35 to 55 percent of the total runoff for this 

land-use type. Paved parking areas represent the next largest 

fraction of runoff (25 to 30 percent), followed by streets (20 to 

15 percent), sidewalks and walkways (about 15 percent), and 

landscaped areas (about 7 percent). Landscaped areas, and to a 

much lesser extent, roof runoff disconnected from the drainage 

system (draining onto about 20 ft or more of pervious area), 

contribute small amounts of runoff during small storms, but 

contribute substantially more runoff when storms are greater 

than 1 inch.

The relative contribution of institutional land-use runoff 

(fig. 17B), although treated in the same manner as commercial land use by the model, has a runoff distribution similar 

to multifamily land use; however, the overall contribution 

of paved parking areas is greater and they are the dominant 

runoff source area for storm less than 0.3 inches. Walkways 

and landscaped areas contribute less to institutional runoff as 

compared to runoff in multifamily land use. Disconnected roof 

runoff is also much lower compared to runoff from multifamily land use. 

The commercial land-use percent contribution is seen 

in figure 17C. Rooftops contributed between about 23 to 

48 percent, street surfaces and paved parking areas contribute 

similar amounts of runoff, but both source areas contribute 

greater volumes in storms less than 0.3 inches. Walkway 

percent contribution was similar to that in multifamily land 

use. Commercial land use contained only a small amount of 

landscaped area and such pervious surfaces do not appear to 

contribute any runoff. Disconnected rooftops also are not a 

contributor of runoff.

Available runoff data were collected for storm depths 

between 0.25 and 2.0 in., and model runoff estimates outside 

of this range are associated with greater uncertainty. Modifications to runoff coefficients were, therefore, based only on 

simulation results between these precipitation depths. Modifications were made in a stepwise manner beginning with runoff 

coefficients from source areas with the greatest relative contribution and ending with those areas contributing the least. 

Model Output Compared to 1999–2000 Runoff and 

Water-Quality Data

The 13 runoff observations from 2000 were first evaluated to determine the quality of the data for comparisons 

with simulated runoff. Plots of rainfall depth as compared to 

runoff depth and runoff coefficient as compared to rainfall 

depth, respectively, are shown in figures 18A and B. Although 
36 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

A

B

C

Landscaped areas

Streets

Walkways

Paved parking

Disconnected roofs

Connected roofs

Relative contribution, in percent

Precipitation, in inches

EXPLANATION 

0

10

20

30

40

50

60

70

80

90

100

0.0

0.1

0.3

0.4

0.5

0.8

1.0

2.0

2.5

3.0

4.0

5.0

0

10

20

30

40

50

60

70

80

90

100

0

10

20

30

40

50

60

70

80

90

100

Figure 17. Cumulative relative percent contributions of major source areas within the A, multifamily, B, institutional, and 

C, commercial land-use types contained in the modeled commercial subcatchment, Cambridge, Massachusetts.
Potential Reductions of Street Solids and Phosphorus Achievable by Street Cleaning 37

Runoff coefficent

y = 0.3651x + 0.4886

R2 = 0.609

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 0.5 1 1.5 2 2.5

Observed precipitation depth, in inches

B

y = 0.6651x + 0.4407

R2 = 0.5846

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 0.5 1 1.5 2 2.5

Precipitation depth, in inches

Observed runoff depth, in inches

A

Figure 18. Plots of A, rainfall depth as compared to runoff depth, and B, runoff coefficient as compared to rainfall depth 

from commercial subcatchment observations, March to December 2000, Cambridge, Massachusetts (USGS ID: 01104677).
38 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

there is some scatter, the general trend appears reasonable for mostly directly connected areas associated with the 

subcatchment. 

Initial SLAMM simulations were run using the parameter 

files provided with SLAMM and 10 years of Boston Logan 

Airport data, and resulted in a mean runoff depth percent error 

between simulated and observed runoff of about 33 percent 

and the sum of the percent differences was about 28 percent. 

Following examination of the relative contribution plots 

seen in figure 17, the selected *.RSV file was modified in a 

stepwise manner until an acceptable agreement was obtained 

between simulated runoff and the 13 observations from 

1999–2000. 

The observed runoff as compared to simulated runoff of 

commercial subcatchment is shown in figure 19. Despite the 

scatter about the 1:1 line, the mean runoff depth percent error 

improved to about -11 percent and the sum of the percent 

differences was -2.31 percent. The comparison of simulated 

runoff data to observed runoff data is shown in figure 20. 

Initial simulations of particulate solid concentrations 

and loads resulted in mean percent error between simulated 

and measured total suspended solids (TSS) of about -43 and 

-140 percent, respectively. Simulations using the modified 

*.RSV file resulted in a minor improvement in particulate 

solid concentrations to about -40 percent and further decreased 

in particulate solids loads to about -163 percent. Because of 

the potential high bias in the measured TSS values, and the 

high number and quality of the particulate solids concentration 

data contained in the WI_AVG01.PSC (Roger Bannerman, 

Wisconsin Department of Natural Resources, oral commun., 

2011), there was little support for modifications to the *.PSC 

file to further improve the particulate solid simulation results.

In terms of particulate P, the initial model resulted in 

mean percent error between simulated and observed particulate P loads of about 54 percent. Simulations using the modified *.RSV file resulted in an improved mean percent error 

between simulated and observed particulate P loads of about 

16 percent.

Model Output Compared to 2009–2011 StreetSolid Yield Data

The base model equipped with the modified *.RSV 

file was run using 3 years of precipitation data from the 

Cambridge DPW and the USGS to match street-solid 

sampling between August 2009 to March 2011. Resulting 

simulated street-solid output data were compared to streetsolid observations as a form of verification of model 

performance. Productivity function coefficients M = 0.07 

and B = 70 corresponding to the RA street cleaner were input 

and the model was run. A plot of simulated street-solid yields 

compared to observed street-solid yields for streets in areas 

characterized as multifamily and commercial land use with the 

2010 data only is shown in figure 21. Average percent error 

between simulated and measured yields of street-solids for 

the multifamily land-use streets is about 22 percent, and for 

the commercial land-use streets is about -13 percent. The sum 

of the percent differences between simulated and measured 

was about -7 and 11 percent for multifamily and commercial 

streets, respectively. Removal of data collected in November 

during the highest periods of leaf-fall from both land-use 

types improved the mean percent error for multifamily and 

commercial streets to about 6.4 and 6.5 percent, respectively. 

However, the sum of the percent differences between 

simulated and observed street-solid loads for multifamily 

streets increased to about -19 percent, although commercial 

streets decreased to less than -2 percent. A time series plot 

of multifamily and commercial/institutional land use streetsolid yield simulations compared with their respective field 

observations is shown in figure 22. Gaps in simulated data 

correspond to street-solid sampling dates not simulated by the 

model. These plots show reasonable agreement between some 

simulated and observed points. However, the model under 

simulates the autumn period of leaf-fall, which is associated 

with some of largest street-solid loadings. Elevated street-solid 

loadings under simulated by the model during summer months 

are perhaps associated with construction track out, deposition 

of organic material, the highly variable nature of the street 

material, or some combination of these.

Model Simulations

The SLAMM model was used to estimate potential 

reductions of total solids and total P resulting from various 

street-cleaning technologies and frequencies. Mechanicalbrush and vacuum-assisted street cleaners were simulated 

using productivity function coefficients supplied with 

SLAMM. Simulations using a second “vacuum-assisted” 

street cleaner using productivity function coefficients developed from the removal efficiency experiments described in the 

Regenerative-Air Street Cleaner Removal Efficiency section 

represented the regenerative-air street cleaner.

Street-Cleaning Program Performance

The five average years *.RAN file was used to simulate 

mechanical-brush, vacuum-assist, and regenerative-air street 

cleaners at the following frequencies: monthly, bi-monthly, 

weekly, and 3 days per week. Mechanical-brush and vacuumassist productivity function coefficients were generated by 

SLAMM based on long-term, on-street parking conditions 

with parking controls specified. Mechanical-brush street 

cleaner productivity function coefficients were M = 0.73 and 

B = 310. Vacuum-assist coefficients were M = 0.70 and 

B = 41. Coefficients for the RA street cleaner evaluated on 

Cambridge streets were the same as those used to match 

simulated street solids to observed street solids: M = 0.07 and 

B = 70.
Potential Reductions of Street Solids and Phosphorus Achievable by Street Cleaning 39

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Simulated runoff depth, in inches

Observed runoff depth, in inches

Figure 19. Simulated runoff depth as compared to observed runoff depth, March to December 2000, Cambridge, 

Massachusetts (USGS ID: 01104677).

03/13/00

04/07/00

05/02/00

05/27/00

06/21/00

07/16/00

08/10/00

09/04/00

09/29/00

10/24/00

11/18/00

12/13/00

0

50,000

100,000

150,000

200,000

250,000

300,000

Runoff volume, in cubic feet

Simulated

Observed

EXPLANATION

Figure 20. Time series of simulated outfall discharge from the commercial land-use subcatchment as compared to observed runoff 

volume, March to December 2000, Cambridge, Massachusetts (USGS ID: 01104677).
40 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

100

1,000

100 1,000

Observed street-solid yield, in pounds per curb-mile

Simulated street solid yield, in pounds per curb-mile

MF

COMM

EXPLANATION

Figure 21. Simulated as compared to observed street-solid yields for multifamily (MF) and commercial (COMM) land-use 

areas, Cambridge, Massachusetts (2010 data only).
Potential Reductions of Street Solids and Phosphorus Achievable by Street Cleaning 41

0

1,000

2,000

3,000

4,000

5,000

Simulated

Observed

04/09/10

05/09/10

06/09/10

07/09/10

08/09/10

09/09/10

10/09/10

11/09/10

12/09/10

01/09/11

03/08/11

03/08/11

5,267

(outside of graph)

03/04/11

4,310

Date

EXPLANATION

EXPLANATION

03/08/11

2,639

03/04/11

2,588

0

1,000

2,000

3,000

4,000

5,000

Simulated

Observed

A. MULTIFAMLY

B. COMMERCIAL

Street-solid yield, in pounds per curb-mile

Figure 22. Simulated and observed street-solid yields, April 2010 to March 2011 for A, multifamily and B, commercial land-use 

types within the modeled subcatchment, Cambridge, Massachusetts.
42 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

The estimated percent reduction of total and particulate 

solids, and total and particulate P following singles passes 

from each street cleaner type under each operational frequency 

are summarized in table 14. The percent reduction of total and 

particulate solids, and P as estimated by SLAMM is for the 

entire subcatchment at its outfall rather than a percent reduction of solids and P as measured specifically on only street 

surfaces. The model appears insensitive to leaf-fall effects 

and could be underestimating the total P load reductions from 

street cleaning programs, particularly in multifamily areas 

where tree density was greatest. Simulations of monthly 

mechanical-brush street cleaning resulted in reductions of 

total and total particulate solids and of about 2.7 and 4.2 percent, respectively. Total and particulate P reductions were 

about 1.4 and 2 percent, respectively. Estimated reductions 

resulting from mechanical-brush street cleaning 3-times per 

week resulted in total and particulate solids of about 6 and 

9.5 percent, respectively, and total and particulate P reduction 

estimates of about 3.0 and 4.5 percent, respectively. 

Simulated reductions of total and particulate solids 

associated with monthly use of vacuum-assist street cleaning 

technology were about 5.2 and 8.2, respectively. Total and particulate P reductions were about 2.7 and 4.0 percent, respectively. Simulated reductions in total and particulate solids and 

total and particulate P associated with a vacuum-assist street 

cleaner with 3-times per week frequency were about 14 and 

24, and 7.4 and 11 percent, respectively. 

Estimated reductions of total and particulate solids using 

RA street cleaning technology at a monthly frequency were 

about 16 and 27 percent, respectively. Monthly total and 

particulate P estimated monthly reductions were about 8 and 

12 percent, respectively. RA street cleaning three-days per 

week resulted in estimated reductions of total and particulate 

solids of about 19 and 32 percent, respectively. Total and 

particulate P percent reductions were about 9.3 and 14 percent, 

respectively. 

Summary and Conclusions

In 2009, the U.S. Geological Survey, in cooperation with 

the city of Cambridge, Massachusetts, the Massachusetts 

Department of Environmental Protection, and the U.S. 

Environmental Protection Agency, conducted a study to better 

understand the physical and chemical nature of the material 

on street surfaces, evaluate the performance of a regenerativeair street cleaner, and estimate potential reductions of total 

particulate solid and total phosphorus loading to the Lower 

Charles River expected from various street cleaning practices. 

Street-solid composite samples from the three streets 

within each land-use type provided an average value for 

Cambridge, Mass., asphalt streets characterized by heavy 

on-street parking, monthly parking controls, intermediate 

surface texture, and fair surface condition within multifamily 

and commercial land-use areas. Street-solid samples included 

gravel and asphalt, and all organic material up to about 

50 millimeters in diameter.

The median yield of street solids on multifamily and 

commercial streets between May and December 2010, 

was about 602 and 467 pounds per curb-mile, respectively. 

Including the large amounts observed in March 2011, 

following the winter season, median yields increased to 

about 616 and 498 lbs/curb-mi, respectively. Average streetsolid yields on multifamily and commercial land-use streets 

between May and December 2010, were about 1.9 and 

1.7 times the national average, respectively, and about 2 

to 3 times the national average when including large endof-winter street-solid yields in March 2011. Street-solid 

yields were greatest during leaf-fall and end-of-winter for 

multifamily and commercial streets, respectively.

Table 14. Source Loading and Management Model (SLAMM) 

estimated percent reductions of total and particulate solids 

and phosphorus using single passes by three different streetcleaning technologies at various frequencies in a predominantly 

commercial subcatchment, Cambridge, Massachusetts.

Constituent

Mechanical brush 

streetcleaning 

percent 

reduction

Vacuumassist 

streetcleaning 

percent 

reduction

Regenerative-air 

streetcleaning 

percent 

reduction

Monthly street cleaning

Total solids 2.7 5.2 16

Total particulate solids 4.2 8.2 27

Total phosphorus 1.4 2.7 8.0

Total particulate phosphorus 2.0 4.0 12

Bimonthly street cleaning

Total solids 3.3 7.0 18

Total particulate solids 5.1 11 30

Total phosphorus 1.7 3.7 8.3

Total particulate phosphorus 2.5 5.4 12

Weekly street cleaning

Total solids 4.2 9.6 18

Total particulate solids 6.6 15 31

Total phosphorus 2.1 5.0 8.7

Total particulate phosphorus 3.1 7.5 13

Street cleaning three times per week

Total solids 6.0 14 19

Total particulate solids 9.5 24 32

Total phosphorus 3.0 7.4 9.3

Total particulate phosphorus 4.5 11 14
Summary and Conclusions 43

Street-solid samples were separated into three grainsize fractions: (1) coarse, (2) medium, and (3) fine. About 

86 percent of all street-solids were greater than the fine grainsize fraction (or very fine sand) for each land-use type. The 

coarse solid fraction was higher on multifamily streets and 

likely from increased tree density on these streets. Routine 

on-street parking in Cambridge likely causes a more even 

distribution of material on the streets compared to areas 

without on-street parking, and as much as 96 percent of the 

material was measured within 9 feet of the curb. 

Median accumulation rate estimates of total street solids 

were about 33 and 23 pounds per curb-mile per day for multifamily and commercial land-use streets, respectively, but 

ranged widely from -43 to 308 lbs/curb-mi/day. Median accumulation rates by grain-size fraction were also similar between 

land-use types, and the medium grain-size fraction accumulated the most rapidly. Accumulation was also slightly greater 

on multifamily streets for the two coarser grain-size fractions. 

Results indicate that street solids in Cambridge, Mass., can 

recover within 1 to 3 days after a rainstorm or street cleaning.

Washoff sample pairs were collected for storms between 

0.32 and 1.71 inches and rainfall intensities between 0.027 and 

0.185 in/hr. Median average washoff from streets in multifamily and commercial land-use types were similar at about 35 

and 40 percent, respectively. The distribution of street solids 

in the washoff also was similar for all streets in magnitude. 

Washoff generally increased with decreasing grain size; however, observed net increases of street solids were attributed 

to overland flow and transport of organic debris from source 

areas other than streets. Net increases of street solids following rainfall events were largest in the coarse grain-size fraction 

on multifamily streets and in the fine grain-size fraction on 

commercial streets.

Median concentrations of organic carbon and total P on 

multifamily streets were determined to be 35 and 29 percent 

greater, respectively, than those commercial streets. Median 

concentrations of organic carbon and total P were highest 

within the fine grain-size fraction on streets in both land-use 

types, followed by the coarse and medium grain-size fractions. Median total masses of organic carbon and total P on 

multifamily streets were determined to be 68 and 75 percent 

greater, respectively, than those on commercial streets. About 

87 and 98 percent of the mass of total P was determined to be 

within the two larger grain-size fractions for multifamily and 

commercial streets, respectively. The median total accumulation rate of total P on streets in multifamily land use was 

about 5 times greater than on commercial streets. The largest 

total P accumulation rate by grain-size fraction was within 

the medium grain-size fraction and was the same for streets 

within both land-use types at 0.004 lbs/curb-mi/day. Accumulation rates within the coarse and fine grain-size fractions on 

multifamily streets were about 11 and 82 times greater than 

those on the commercial streets, respectively. Multifamily and 

commercial median washoff of total P was 58 and 39 percent, 

respectively, and ranged widely from -1,120 to 99 percent. 

Median washoff of total P by grain-size fraction was also similar between both land-use types.

Median street-solid removal efficiencies of a regenerative-air street cleaner were 82 and 78 percent for multifamily and commercial land-use types, respectively. Removal 

efficiency decreased with decreasing grain size of the street 

solids. Median removal efficiency of solids by the regenerative-air street cleaner by grain-size fraction was also similar 

between land-use types. Negative values, or net increases in 

material, were occasionally observed within the fine grainsize fraction, and typically occurred on streets with rough and 

damaged surfaces. Increases in street solids following a street 

cleaner pass is likely the result of the wet gutter broom of the 

cleaner dislodging coarser material from inside cracks and 

holes within the street surface and exposing finer materials, 

as well as pasting fine materials back onto the street surface, 

which would then be available for washoff. The regenerativeair street cleaner tested left a consistent median residual yield 

regardless of the initial yield on the streets of both land-use 

types of about 100 lbs/curb-mi. Total P median reductions 

resulting from a single pass of a regenerative-air street cleaner 

on streets in multifamily and commercial land-use types were 

about 82 and 62 percent, respectively, decreased with decreasing grain-size, and were similar in magnitude for the three 

grain-size fractions on streets in both land-use types. Constituent mass reductions as a result of regenerative-air street 

cleaning generally decreased with decreasing grain size, and 

reductions were slightly less during the spring and summer 

months, likely a result of lower available street-solid yields. 

Net increases of some constituent masses following a single 

regenerative-air street cleaner pass were seen almost entirely 

in the fine grain-size fraction results from multifamily streets. 

A Source Loading and Management Model for Microsoft 

Windows version 9.4.0 was applied to a 21.8 acre subcatchment in Cambridge, Mass., consisting of commercial, institutional and multifamily land-use types to evaluate the potential reductions of phosphorus as a result of street-cleaning 

practices. The model results were calibrated to runoff and 

water-quality data collected at the subcatchment outfall in 

2000 and street-solid yield data collected in 2010. Rooftop 

runoff was the dominant source of the total runoff simulated at 

the subcatchment outfall. Street surfaces in the subcatchment 

contributed about 20 percent of the total runoff at the outfall in 

the model.

Productivity function coefficients for mechanical-brush 

and vacuum-assisted street cleaners were generated by 

SLAMM based on long-term (24-hour), on-street parking with 

parking controls. Regenerative-air street cleaner productivity 

function coefficients were developed from field data under the 

same conditions. Simulations based on 5 years of average climatic conditions resulted in potential reductions of total solids 

of about 3 and 5 percent for monthly mechanical-brush and 

vacuum-assist street cleaner operation, respectively, and about 

16 percent for the regenerative-air street cleaner. Estimated 

total P reductions for monthly use of mechanical-brush and 

vacuum-assisted street cleaners were about 1 and 3 percent, 
44 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

respectively, and 8 percent for the regenerative-air machine. 

An operational frequency of three times per week increased 

potential reductions of total solids for mechanical-brush, 

vacuum-assist and regenerative-air street cleaners to about 6, 

14 and 19 percent, respectively. Simulated percent reductions 

of total P were about 3, 7, and 9 percent, respectively, when 

streets were cleaned 3 times per week. 

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Pitt, R.E., and Bozeman, M., 1982, Sources of urban runoff 

pollution and its effects on an urban creek: Cincinnati, 

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46 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

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Tables 9, 11, 12, and 13
48 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

Table 9A. Total and grain-size fraction median constituent total-recoverable concentrations and masses constituent masses from 

composite street-solid samples collected from streets representing A, multifamily and B, commercial land-use types in Cambridge, 

Massachusetts.

[Bold italicized values indicate less than one-half the detection limit was used to determine concentration and normalized mass. Note: concentrations converted 

to milligrams per kilogram and in this case are equivalent to concentrations in parts per million (ppm). n, number of samples; mg/kg, milligrams per kilogram; g, 

grams; mm, millimeter; coarse, greater than or equal to 2 mm; medium, less than 2 mm greater than or equal to 0.125 mm; fine, less than 0.125 mm in diameter]

Total 

n = 225

Coarse 

n = 76

Medium 

n = 74

Fine 

n = 75

Multifamily

Analyte

Detection limit 

(mg/kg)

Median 

concentration 

(mg/kg)

Standard 

deviation 

(mg/kg)

Median 

concentration 

(mg/kg)

Standard 

deviation 

(mg/kg)

Median 

concentration 

(mg/kg)

Standard 

deviation 

(mg/kg)

Median 

concentration 

(mg/kg)

Standard 

deviation 

(mg/kg)

Organic carbon 500 91,700 126,431 183,500 151,308 59,850 52,671 72,800 28,279

Silver 0.2 0.10 0.25 0.10 0.06 0.10 0.06 0.10 0.40

Aluminum 100 5,200 3,042 2,700 2,696 4,630 1,045 8,900 1,427

Arsenic 3.0 4.0 14 1.5 23 4.0 2.3 10.0 3.9

Barium 1 55 75 31 17 48 27 127 101

Beryllium 0.5 0.25 0.17 0.25 0.14 0.25 0.16 0.25 0.20

Bismuth 5 2.50 0.54 2.50 0.00 2.50 0.57 2.50 0.76

Calcium 100 9,400 7,462 11,732 11,360 8,150 2,906 10,200 3,642

Cadmium 1 0.50 0.41 0.50 0.08 0.50 0.64 0.50 0.31

Cobalt 1 4.0 16 3.0 27 4.0 1.1 8.0 1.6

Chromium 1 41 65 10 8 41 36 140 39

Copper 0.5 47 160 14 128 46 217 176 46

Iron 100 18,600 100,001 5,650 8,010 18,000 5,722 27,800 5,534

Potassium 100 1,700 1,276 2,400 1,751 1,100 552 1,800 522

Lanthanum 0.5 8.5 5.9 4.4 4.5 7.9 2.0 16.3 3.0

Lithium 1 8.0 4.6 5.0 5.0 7.0 1.8 13.0 2.3

Magnesium 0.01 0.34 0.36 0.24 0.61 0.28 0.06 0.44 0.07

Manganese 2 272 131 202 201 247 48 350 39

Molybdenum 1 2.00 2.05 0.50 0.92 2.00 1.39 5.00 1.05

Sodium 0.01 0.03 0.22 0.02 0.23 0.02 0.24 0.04 0.17

Nickel 1 15 21 8 26 14 7 41 8

Phosphorus 100 700 461 800 600 500 241 900 389

Lead 2 111 247 25 37 110 178 436 242

Antimony 5 2.5 3.1 2.5 5.2 2.5 0.3 2.5 0.8

Scandium 0.5 1.2 0.9 0.3 0.9 1.1 0.4 2.1 0.5

Tin 10 10 146 5 65 5 14 20 240

Strontium 0.5 40 21 43 28 34 15 44 12

Titanium 100 500 353 200 216 500 134 1,000 199

Vanadium 2 24 17 12 12 22 6 46 10

Tungsten 10 5.0 1.9 5.0 0.0 5.0 2.9 5.0 1.8

Yttrium 0.5 5.3 2.9 3.0 2.5 4.8 1.1 8.6 1.7

Zinc 0.5 169 185 76 79 160 97 427 137

Zirconium 0.5 2.7 2.8 1.2 1.9 2.7 1.5 5.9 2.8
Table 9A 49

Table 9A. Total and grain-size fraction median constituent total-recoverable concentrations and masses constituent masses from 

composite street-solid samples collected from streets representing A, multifamily and B, commercial land-use types in Cambridge, 

Massachusetts.—Continued

[Bold italicized values indicate less than one-half the detection limit was used to determine concentration and normalized mass. Note: concentrations converted 

to milligrams per kilogram and in this case are equivalent to concentrations in parts per million (ppm). n, number of samples; mg/kg, milligrams per kilogram; g, 

grams; mm, millimeter; coarse, greater than or equal to 2 mm; medium, less than 2 mm greater than or equal to 0.125 mm; fine, less than 0.125 mm in diameter]

Total 

n = 225

Coarse 

n = 76

Medium 

n = 74

Fine 

n = 75

Multifamily

Analyte Detection 

limit 

(mg/kg)

Median 

mass

(g)

Standard 

deviation

(g)

Median 

mass

(g)

Standard 

deviation

(g)

Median 

mass

(g)

Standard 

deviation

(g)

Median 

mass

(g)

Standard 

deviation

(g)

Organic carbon 500 13 92 22 148 19 15 2.9 5.9

Silver 0.2 0.02 0.05 0.01 0.05 0.03 0.04 0.01 0.06

Aluminum 100 0.59 1.41 0.35 1.11 1.25 1.78 0.37 0.80

Arsenic 3 0.43 5.9 0.30 9.9 1.1 1.8 0.40 0.93

Barium 1 7.9 17 3.6 19 12 18 5.6 9.4

Beryllium 0.5 0.03 0.09 0.03 0.10 0.07 0.09 0.01 0.04

Bismuth 5 0.31 1.16 0.28 0.98 0.67 1.6 0.10 0.22

Calcium 100 1.2 4.2 1.2 6.0 2.1 3.2 0.37 1.6

Cadmium 1 0.06 0.20 0.06 0.20 0.13 0.25 0.02 0.05

Cobalt 1 0.5 6.6 0.3 11 1.0 1.4 0.3 0.7

Chromium 1 4.1 15 1.1 4.0 12 21 6.0 11

Copper 0.5 6.5 48 1.5 53 13 62 7.6 13

Iron 100 1.8 5.4 0.7 2.6 4.4 7.5 1.1 2.4

Potassium 100 0.16 1.1 0.31 1.8 0.33 0.30 0.01 0.01

Lanthanum 0.5 0.91 2.5 0.45 1.6 2.03 3.3 0.66 1.3

Lithium 1 0.91 2.4 0.50 1.7 2.02 3.2 0.57 1.5

Magnesium 0.01 0.38 0.96 0.33 1.0 0.76 1.1 0.20 0.47

Manganese 2 33 88 28 113 67 85 13 28

Molybdenum 1 0.17 0.65 0.07 0.49 0.47 0.84 0.20 0.37

Sodium 0.01 0.03 2.3 0.02 1.5 0.05 3.6 0.02 0.77

Nickel 1 2.0 7.8 1.1 11 4.0 6.5 1.8 3.6

Phosphorus 100 0.08 0.29 0.08 0.45 0.14 0.15 0.03 0.08

Lead 2 16 29 2.1 17 28 34 20 25

Antimony 5 0.31 1.25 0.28 1.8 0.67 0.89 0.12 0.34

Scandium 0.5 0.13 0.33 0.06 0.24 0.30 0.43 0.08 0.21

Tin 10 1.6 5.7 1.4 5.1 2.7 5.7 0.71 6.2

Strontium 0.5 5.0 19 4.8 28 8.5 15 1.7 5.6

Titanium 100 0.05 0.16 0.02 0.08 0.12 0.22 0.04 0.09

Vanadium 2 2.72 8.2 1.31 6.6 5.5 10 1.9 5.3

Tungsten 10 0.60 1.7 0.55 2.0 1.3 1.8 0.20 0.37

Yttrium 0.5 0.54 1.67 0.35 1.52 1.23 2.09 0.37 0.80

Zinc 0.5 23 45 6.5 44 47 47 17 37

Zirconium 0.5 0.31 1.3 0.15 0.61 0.74 1.8 0.26 0.76
50 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

Table 9B. Total and grain-size fraction median constituent total-recoverable concentrations and masses constituent masses from 

composite street-solid samples collected from streets representing A, multifamily and B, commercial land-use types in Cambridge, 

Massachusetts.

[Bold italicized values indicate less than one-half the detection limit was used to determine concentration and normalized mass. Note: concentrations converted 

to milligrams per kilogram and in this case are equivalent to concentrations in parts per million (ppm). n, number of samples; mg/kg, milligrams per kilogram; g, 

grams; mm, millimeter; coarse, greater than or equal to 2 mm; medium, less than 2 mm greater than or equal to 0.125 mm; fine, less than 0.125 mm in diameter]

Total 

n = 221

Coarse 

n = 75

Medium 

n = 73

Fine 

n = 73

Commercial

Analyte

Detection limit 

(mg/kg)

Median 

concentration 

(mg/kg)

Standard 

deviation 

(mg/kg)

Median 

concentration 

(mg/kg)

Standard 

deviation 

(mg/kg)

Median 

concentration 

(mg/kg)

Standard 

deviation 

(mg/kg)

Median 

concentration 

(mg/kg)

Standard 

deviation 

(mg/kg)

Organic carbon 500 60,100 113,171 160,000 142,140 27,100 18,274 59,100 17,275

Silver 0.2 0.10 0.67 0.10 0.10 0.10 0.10 0.50 0.99

Aluminum 100 5,000 2,528 4,100 778 4,100 778 7,800 986

Arsenic 3 5.00 4.66 4.00 2.17 4.00 2.17 11.00 4.19

Barium 1 54 53 42 28 42 28 128 36

Beryllium 0.5 0.25 0.15 0.25 0.04 0.25 0.04 0.25 0.17

Bismuth 5 2.5 0.0 2.5 0.0 2.5 0.0 2.5 0.0

Calcium 100 8,600 5,613 6,100 1,631 6,100 1,631 10,000 3,237

Cadmium 1 0.50 0.21 0.50 0.26 0.50 0.26 0.50 0.26

Cobalt 1 5.0 29 4.0 4.6 4.0 4.6 8.0 49

Chromium 1 51 205 47 58 47 58 166 56

Copper 0.5 71.78 125.30 66 99 66 99 250 96

Iron 100 23,000 12,239 21,700 6,797 21,700 6,797 34,200 6,005

Potassium 100 1,100 878 700 254 700 254 1,400 296

Lanthanum 0.5 9.30 5.44 7.80 1.51 7.80 1.51 16.60 2.91

Lithium 1 8.00 4.19 7.00 1.95 7.00 1.95 11.00 3.09

Magnesium 0.01 0.33 0.20 0.26 0.07 0.26 0.07 0.40 0.07

Manganese 2 270 271 237 64 237 64 358 43

Molybdenum 1 3.0 3.0 2.0 1.7 2.0 1.7 7.0 1.9

Sodium 0.01 300 3,544 200 1,943 200 1,943 500 2,671

Nickel 1 18 25 15.00 31.58 15.00 31.58 48.00 9.08

Phosphorus 100 500 656 400 166 400 166 800 288

Lead 2 62 214 61 226 61 226 241 231

Antimony 5 2.50 0.92 2.50 0.00 2.50 0.00 2.50 0.67

Scandium 0.5 1.10 0.68 0.96 0.24 0.96 0.24 1.80 0.39

Tin 10 10 210 5.0 11 5.0 11 20 361

Strontium 0.5 33.30 24.34 22.40 6.68 22.40 6.68 40.10 10.42

Titanium 100 500 331 400 110 400 110 900 222

Vanadium 2 23 18 21 3.5 21 3.5 48 8.2

Tungsten 10 5.0 2.9 5.0 4.1 5.0 4.1 5.0 2.9

Yttrium 0.5 5.6 3.1 4.7 0.9 4.7 0.9 9.0 1.5

Zinc 0.5 146 219 132 56 132 56 521 147

Zirconium 0.5 3.9 4.0 3.5 1.0 3.5 1.0 8.7 2.3
Table 9B 51

Table 9B. Total and grain-size fraction median constituent total-recoverable concentrations and masses constituent masses from 

composite street-solid samples collected from streets representing A, multifamily and B, commercial land-use types in Cambridge, 

Massachusetts.—Continued

[Bold italicized values indicate less than one-half the detection limit was used to determine concentration and normalized mass. Note: concentrations converted 

to milligrams per kilogram and in this case are equivalent to concentrations in parts per million (ppm). n, number of samples; mg/kg, milligrams per kilogram; g, 

grams; mm, millimeter; coarse, greater than or equal to 2 mm; medium, less than 2 mm greater than or equal to 0.125 mm; fine, less than 0.125 mm in diameter]

Total 

n = 221

Coarse 

n = 75

Medium 

n = 73

Fine 

n = 73

Commercial

Analyte

Detection 

limit 

(mg/kg)

Median 

mass

(g)

Standard 

deviation

(g)

Median 

mass

(g)

Standard 

deviation

(g)

Median 

mass

(g)

Standard 

deviation

(g)

Median 

mass

(g)

Standard 

deviation

(g)

Organic carbon 500 4.3 33 8.5 12 8.5 12 0.28 0.68

Silver 0.2 0.02 0.08 0.03 0.08 0.03 0.08 0.03 0.11

Aluminum 100 0.19 2.1 1.07 3.20 1.07 3.20 0.04 0.12

Arsenic 3 0.44 2.4 0.99 3.6 0.99 3.6 0.57 1.8

Barium 1 6.55 15 13 19 13 19 7.1 13

Beryllium 0.5 0.02 0.12 0.06 0.20 0.06 0.20 0.01 0.06

Bismuth 5 0.23 1.2 0.64 1.9 0.64 1.9 0.13 0.31

Calcium 100 0.60 3.3 1.8 4.6 1.8 4.6 0.05 0.26

Cadmium 1 0.05 0.25 0.13 0.40 0.13 0.40 0.03 0.06

Cobalt 1 0.52 6.6 1.0 3.6 1.0 3.6 0.47 11

Chromium 1 6.1 19 15 26 15 26 9.3 13

Copper 0.5 8.9 21 20 28 20 28 14 15

Iron 100 0.50 6.6 5.5 9.4 5.5 9.4 0.19 0.33

Potassium 100 0.08 0.46 0.22 0.55 0.22 0.55 0.01 0.03

Lanthanum 0.5 1.0 4.0 2.0 6.2 2.0 6.2 0.89 2.0

Lithium 1 0.78 3.9 2.0 5.8 2.0 5.8 0.58 2.7

Magnesium 0.01 0.19 1.27 0.77 1.91 0.77 1.91 0.02 0.08

Manganese 2 29 83 61 119 61 119 19 41

Molybdenum 1 0.27 0.60 0.66 0.68 0.66 0.68 0.39 0.57

Sodium 0.01 0.01 2.6 0.05 4.4 0.05 4.4 0.002 0.13

Nickel 1 2.1 7.5 4.2 11 4.2 11 2.6 4.5

Phosphorus 100 0.02 0.33 0.09 0.25 0.09 0.25 0.003 0.01

Lead 2 8.3 31 20 46 20 46 13 17

Antimony 5 0.24 1.2 0.64 1.9 0.64 1.9 0.13 0.31

Scandium 0.5 0.12 0.52 0.26 0.77 0.26 0.77 0.10 0.36

Tin 10 1.2 5.9 2.0 5.7 2.0 5.7 1.2 6.2

Strontium 0.5 3.2 12 6.7 14 6.7 14 2.1 9.0

Titanium 100 0.01 0.22 0.11 0.35 0.11 0.35 0.00 0.01

Vanadium 2 2.8 10 5.2 15 5.2 15 2.6 8.1

Tungsten 10 0.46 2.6 1.3 4.2 1.3 4.2 0.26 1.0

Yttrium 0.5 0.59 2.3 1.2 3.4 1.2 3.4 0.47 1.3

Zinc 0.5 23 51 38 66 38 66 26 48

Zirconium 0.5 0.49 2.0 0.83 3.0 0.83 3.0 0.45 1.4
52 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11 Table 11. Accumulation rates for constituents measured in street-solid composite samples, by grain-size fraction and land-use type collected before and after precipitation events in pounds per curb-mile per day, Cambridge, Massachusetts. [Negative values indicate a net loss of material. Commercial data does not include Mount Auburn Street; mm, millimeter; coarse, greater than or equal to 2 mm; medium, less than 2 mm greater than or equal to 0.125 mm; fine, less than 0.125 mm in diameter] Organic carbon Silver Alumi- num Arsenic Barium Beryl- lium Bismuth Calcium Cad- mium Cobalt Chro- mium Copper Iron Potas- sium Lantha- num Lithium Mutlifamily-all grain-size fractions Average 1.6 0.006 0.06 0.11 0.94 0.004 0.03 0.13 0.01 0.07 0.83 0.93 0.20 0.04 0.11 0.10 Median 1.4 0.002 0.06 0.06 0.43 0.003 0.03 0.09 0.004 0.05 0.68 0.43 0.11 0.03 0.09 0.06 Maximum 17 0.128 0.70 1.3 42 0.028 0.23 0.88 0.69 0.88 4.21 7.71 1.66 0.24 1.4 1.5 Minimum -10 -0.006 -0.49 -0.81 -29 -0.014 -0.14 -0.31 -0.51 -0.48 -10.98 -5.48 -1.22 -0.04 -0.70 -0.86 Coarse Average 1.3 0.001 -0.016 0.013 0.115 0.001 0.008 0.042 0.002 -0.023 0.046 0.016 -0.040 0.034 -0.007 -0.031 Median 1.4 0.001 0.012 0.014 0.204 0.001 0.014 0.019 0.003 0.009 0.047 0.081 0.029 0.032 0.036 0.024 Maximum 17 0.004 0.220 0.109 1.15 0.009 0.085 0.381 0.017 0.195 1.17 0.545 1.49 0.096 0.223 0.183 Minimum -10 -0.006 -0.489 -0.109 -1.97 -0.014 -0.139 -0.310 -0.028 -0.483 -1.14 -1.48 -1.22 -0.021 -0.627 -0.860 Medium Average 2.6 0.002 0.115 0.122 1.6 0.006 0.060 0.235 0.023 0.091 1.3 1.3 0.417 0.048 0.186 0.221 Median 2.9 0.002 0.089 0.176 0.311 0.005 0.049 0.163 0.010 0.076 2.3 1.2 0.385 0.049 0.177 0.141 Maximum 8.1 0.009 0.704 0.504 41.7 0.023 0.232 0.884 0.690 0.595 4.2 7.7 1.7 0.145 1.35 1.45 Minimum -1.8 -0.001 -0.289 -0.806 -29.4 -0.001 -0.015 -0.137 -0.508 -0.184 -11 -5.5 -0.663 -0.037 -0.698 -0.369 Fine Average 0.79 0.017 0.079 0.219 1.19 0.004 0.025 0.115 0.010 0.164 1.31 1.74 0.235 0.025 0.152 0.126 Median 0.64 0.003 0.074 0.148 0.866 0.002 0.017 0.079 0.003 0.075 1.30 1.39 0.199 0.002 0.187 0.100 Maximum 2.1 0.128 0.201 1.27 3.36 0.028 0.073 0.466 0.060 0.884 3.74 5.84 0.760 0.239 0.460 0.342 Minimum -0.01 0.000 -0.025 -0.191 0.003 -0.010 -0.002 0.006 -0.000 -0.001 -0.516 0.260 -0.106 -0.001 -0.078 -0.011 Commercial-all grain-size fractions Average 0.093 0.008 0.020 0.046 0.718 0.004 0.021 0.057 0.005 0.830 0.340 0.688 0.139 0.011 0.127 0.099 Median 0.067 0.003 0.007 0.031 0.506 0.002 0.018 0.010 0.004 0.050 0.460 0.315 0.026 0.001 0.069 0.062 Maximum 4.13 0.110 0.476 0.340 3.10 0.030 0.299 0.365 0.060 16.8 4.20 5.77 1.86 0.121 1.16 0.647 Minimum -11.6 -0.027 -0.271 -0.438 -0.874 -0.009 -0.141 -0.180 -0.028 -0.281 -8.58 -5.08 -0.723 -0.038 -0.516 -0.310 Coarse Average -0.436 0.000 -0.003 0.034 0.101 0.002 -0.002 0.063 -0.000 0.002 0.054 -0.117 0.027 0.015 0.004 0.036 Median 0.488 0.000 0.003 0.009 -0.016 0.001 0.005 0.054 0.001 0.003 0.007 0.072 0.013 0.005 0.004 -0.005 Maximum 3.59 0.006 0.216 0.314 1.60 0.014 0.066 0.292 0.013 0.265 0.491 0.413 0.664 0.121 0.238 0.647 Minimum -11.6 -0.006 -0.271 -0.063 -0.874 -0.009 -0.141 -0.180 -0.028 -0.281 -0.501 -1.933 -0.723 -0.038 -0.272 -0.310 Medium Average 0.334 0.004 0.121 0.027 0.925 0.008 0.082 0.161 0.034 0.593 1.84 0.625 0.659 0.026 0.280 0.239 Median 0.592 0.003 0.047 0.031 0.623 0.005 0.047 0.151 0.009 0.074 2.81 0.315 0.709 0.007 0.150 0.064 Maximum 4.13 0.037 0.568 0.711 3.10 0.030 0.299 0.365 0.117 4.75 12.6 5.77 1.86 0.136 1.24 1.68 Minimum -5.34 -0.027 -0.177 -0.438 -0.037 -0.007 -0.065 -0.022 -0.017 -0.078 -8.58 -5.08 -0.594 -0.020 -0.516 -0.377 Fine

Average 0.068 0.017 0.011 0.152 1.48 0.006 0.032 0.014 0.009 2.20 2.03 2.38 0.038 0.002 0.258 0.153Median 0.057 0.007 0.007 0.148 1.09 0.003 0.021 0.010 0.004 0.097 1.59 2.02 0.030 0.001 0.154 0.110Maximum 0.179 0.110 0.036 0.340 3.28 0.023 0.094 0.042 0.026 16.8 5.95 5.00 0.094 0.008 0.900 0.539Minimum -0.011 -0.019 -0.003 -0.070 -0.027 -0.000 -0.004 0.000 0.002 0.002 -0.658 0.130 -0.003 -0.000 -0.050 0.008
Table 11 53

Table 11. Accumulation rates for constituents measured in street-solid composite samples, by grain-size fraction and land-use type collected before and after precipitation events in pounds per curb-mile per day, Cambridge, Massachusetts.—Continued[Negative values indicate a net loss of material. Commercial data does not include Mount Auburn Street; mm, millimeter; coarse, greater than or equal to 2 mm; medium, less than 2 mm greater than or equal to 0.125 mm; fine, less than 0.125 mm in diameter]

Magnesium Man- ganese Molyb- denum Sodium Nickel Phospho- rus Lead Anti- mony Scan- dium Tin Stron- tium Tita- nium Vana- dium Tung- sten Yttrium Zinc Zirco- nium

Mutlifamily-all grain-size fractions

Average 0.14 3.28 0.02 0.015 0.29 0.071 3.1 0.03 -0.04 0.17 0.52 0.03 0.34 0.06 0.24 2.98 0.02Median 0.04 2.39 0.01 0.004 0.08 0.002 0.38 0.03 0.01 0.11 0.47 0.01 0.20 0.05 0.04 0.85 0.01Maximum 3.9 28.4 0.41 0.324 3.9 2.36 64 0.23 0.18 5.9 6.4 0.86 4.1 0.46 7.2 78 0.98Minimum -0.38 -25.5 -0.54 -0.018 -1.5 -0.017 -43 -0.14 -2.1 -9.1 -3.4 -0.05 -1.6 -0.28 -0.44 -53 -0.57

Coarse

Average -0.008 1.68 -0.001 0.002 -0.009 0.004 -1.28 0.008 -0.002 0.147 0.176 -0.001 -0.059 0.016 -0.009 0.157 0.006Median 0.021 1.45 0.002 0.001 0.024 0.001 0.070 0.014 0.003 0.069 0.197 0.001 0.063 0.029 0.015 0.463 0.007Maximum 0.204 28.4 0.017 0.022 0.863 0.025 0.913 0.085 0.034 0.655 1.26 0.020 0.294 0.170 0.174 2.04 0.191Minimum -0.377 -25.5 -0.028 -0.010 -0.924 -0.017 -19.2 -0.139 -0.094 -0.278 -1.65 -0.033 -1.51 -0.278 -0.435 -5.63 -0.173

Medium

Average 0.075 5.28 0.042 0.010 0.593 0.0145 5.96 0.060 0.026 0.319 0.962 0.011 0.673 0.120 0.100 4.62 0.028Median 0.041 3.23 0.060 0.012 0.648 0.0036 2.73 0.049 0.028 0.117 0.859 0.012 0.710 0.098 0.096 4.08 0.002Maximum 0.353 25.2 0.410 0.032 3.89 0.0518 64.1 0.232 0.179 2.30 6.36 0.078 4.07 0.464 0.770 77.6 0.980Minimum -0.094 -5.70 -0.537 -0.018 -1.48 -0.0001 -42.8 -0.015 -0.090 -2.69 -3.38 -0.053 -1.631 -0.029 -0.343 -53.4 -0.566

Fine

Average 0.429 2.73 0.038 0.039 0.291 0.24515 5.16 0.021 -0.194 -0.008 0.400 0.095 0.449 0.047 0.771 4.63 0.040Median 0.042 2.68 0.038 0.007 0.261 0.01018 5.44 0.017 0.019 0.365 0.337 0.013 0.459 0.034 0.099 3.49 0.037Maximum 3.92 8.68 0.139 0.324 1.24 2.3599 9.80 0.060 0.047 5.92 1.43 0.861 1.18 0.120 7.17 14.0 0.193Minimum -0.011 -1.41 -0.077 -0.000 -0.650 -0.00004 0.028 -0.002 -2.110 -9.095 -0.012 -0.009 -0.247 -0.004 -0.153 0.145 -0.141

Commercial-all grain-size fractions

Average 0.021 2.28 0.027 0.032 -0.000 0.0038 1.77 0.027 0.015 0.405 0.340 0.002 0.325 0.099 0.074 3.64 0.077Median 0.003 1.88 0.040 0.001 0.177 0.0004 0.083 0.019 0.013 0.157 0.241 0.001 0.218 0.036 0.061 2.34 0.016Maximum 0.263 20.5 0.244 0.782 1.397 0.0297 38.6 0.299 0.116 2.60 2.47 0.048 2.32 1.54 0.454 15.8 0.488Minimum -0.108 -11.664 -0.445 -0.470 -5.166 -0.0028 -23.0 -0.065 -0.050 -1.98 -0.899 -0.024 -1.280 -0.281 -0.174 -6.21 -0.193

Coarse

Average 0.019 -0.470 0.004 0.039 -0.004 0.0033 0.004 0.011 0.003 0.063 0.090 -0.000 -0.034 -0.004 0.003 -0.159 0.004Median 0.004 -0.002 0.002 0.002 0.010 0.0001 0.015 0.006 -0.000 0.009 0.093 -0.000 0.007 0.009 -0.001 0.254 0.003Maximum 0.156 4.14 0.076 0.365 0.400 0.0237 0.243 0.075 0.065 0.579 0.994 0.015 0.751 0.131 0.144 2.65 0.158Minimum -0.108 -11.7 -0.059 -0.014 -0.633 -0.0028 -0.242 -0.054 -0.036 -0.281 -0.899 -0.020 -1.28 -0.281 -0.119 -6.21 -0.148

Medium

Average 0.080 7.31 0.032 0.042 0.120 0.015 2.63 0.082 0.029 1.167 0.679 0.011 0.686 0.165 0.158 4.51 0.138Median 0.052 5.26 0.100 0.010 0.494 0.004 -0.051 0.047 0.017 0.174 0.131 0.007 0.338 0.094 0.073 3.22 0.046Maximum 0.263 20.5 0.244 0.782 2.14 0.077 38.6 0.299 0.123 5.27 2.70 0.052 2.32 0.597 0.611 10.5 0.574Minimum -0.055 -5.00 -0.445 -0.470 -5.17 -0.001 -23.0 -0.065 -0.050 -1.573 -0.799 -0.024 -0.337 -0.131 -0.174 -1.36 -0.193

Fine

Average 0.005 4.65 0.083 0.002 0.613 0.0008 1.85 0.032 0.027 0.455 0.571 0.001 0.641 0.214 0.150 7.18 0.153Median 0.003 3.29 0.059 0.001 0.423 0.0001 1.79 0.021 0.015 0.253 0.372 0.001 0.450 0.042 0.088 5.82 0.097Maximum 0.017 12.3 0.173 0.009 1.397 0.0042 7.65 0.094 0.093 1.685 1.93 0.005 1.98 1.54 0.454 15.8 0.467Minimum -0.000 -1.74 -0.013 -0.002 0.111 0.0000 -2.87 -0.004 -0.018 -0.241 -0.133 -0.003 -0.259 -0.007 -0.043 -0.152 -0.020
54 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11 Table 12. Percent washoff of constituent masses in terms of grain-size fraction and land-use type from street-solid composite samples collected before and after 6 storms with a recorded rainfall volume range of 0.32 to 1.71 inches, Cambridge, Massachusetts. [Negative values indicate a net increase of material; mm, millimeter; coarse, greater than or equal to 2 mm; medium, less than 2 mm greater than or equal to 0.125 mm; fine, less than 0.125 mm in diameter] Organic carbon Silver Aluminum Arsenic Barium Beryllium Bismuth Calcium Cadmium Cobalt Chro- mium Copper Iron Potas- sium Lantha- num Lithium Multifamily all grain-size fractions Average -25.83 -22.14 -37.64 10.53 -2.37 -138.48 -23.92 -14.53 -1.090 -42.06 -11.17 -27.92 -24.17 19.18 -83.33 -35.45 Median 59.49 39.29 49.43 62.10 49.96 37.99 39.75 54.02 39.75 59.76 59.83 50.88 54.77 64.86 48.65 51.80 Maximum 95.26 97.22 93.96 95.52 94.59 92.53 92.53 95.42 95.84 93.47 97.34 98.25 92.78 94.11 92.86 94.52 Minimum -1,454 -1,120 -1,243 -617 -1,487 -6,730 -1,420 -1,347 -1,120 -1,321 -886 -1,478 -1,082 -1,064 -2,799 -1,452 Coarse Average -48.33 -28.5 -85.7 4.17 9.05 -1.74 8.02 -25.9 8.02 -85.8 -48.0 -4.62 -60.3 29.8 -222.3 -79.5 Median 41.86 21.1 42.1 39.7 31.2 21.2 21.2 59.0 21.2 51.7 10.3 21.6 24.8 64.1 -31.80 49.1 Maximum 95.26 90.3 82.0 95.0 88.1 83.4 86.8 95.4 86.8 89.7 86.8 88.4 87.9 93.1 92.21 83.4 Minimum -1,196 -633 -966 -286 -339 -286 -286 -628 -286 -1,321 -824 -310 -958 -367 -2,799 -1,037 Medium Average 25.1 17.5 18.4 1.6 34 -11.6 25 27 25 9.95 44 -10.5 26 44 22 26 Median 44.0 43.2 35.9 47.7 41 33.2 34 30 34 33.7 60 51.6 52 36 40 34 Maximum 84.6 73.8 71.0 92.2 73 62.7 63 69 63 77.6 97 98.3 79 75 76 81 Minimum -106 -114 -122 -226 -27 -413 -64 -67 -64 -311 -38 -433 -81 -6.4 -93 -92 Fine Average -51.25 -54.95 -39.24 26.7 -51.4 -420.4 -109.0 -43.34 -37.44 -44.49 -24.35 -71.76 -33.19 -17.57 -30.65 -46.55 Median 69.86 83.17 75.60 80.8 75.2 79.16 75.38 76.31 75.38 75.85 77.08 76.80 75.52 76.44 78.56 80.41 Maximum 93.53 97.22 93.96 95.5 94.6 92.53 92.53 95.15 95.84 93.47 92.08 93.95 92.78 94.11 92.86 94.52 Minimum -1,454 -1,120 -1,243 -617 -1,487 -6,730 -1,420 -1,347 -1,120 -1,294 -886 -1,478 -1,082 -1,064 -1,094 -1,452 Commercial all grain-size fractions Average 32.8 -3.40 -25.3 -5.13 18.4 13.5 27.9 25.8 27.4 -12.6 -311.1 12.5 -18.8 39.3 -33.13 -12.4 Median 51.3 52.3 38.0 32.7 50.6 39.5 39.5 50.8 41.8 33.2 43.82 44.4 40.3 57.1 34.01 46.6 Maximum 96.4 99.2 96.0 96.0 96.8 96.7 94.8 95.6 94.8 95.5 94.26 96.9 94.6 96.9 95.48 96.4 Minimum -268 -772 -958 -590 -395 -752 -249 -332 -249 -629 -15,130 -354 -731 -323 -1,402 -819 Coarse Average 17.4 -5.40 -114 -28.2 -0.938 24 25 14.5 27 -85.4 -927.1 -2.86 -107 44 -146.9 -75.9 Median 41.4 34.8 -17.4 -5.84 26.2 18 20 28.6 20 -56.3 11.54 24.3 -15.4 46 -23.59 8.42 Maximum 89.0 90.3 89.4 96.0 90.2 89 89 92.9 89 89.4 83.01 94.2 94.5 97 95.48 89.4 Minimum -268 -772 -958 -405 -281 -31 -31 -118 -31 -629 -15,130 -354 -731 -8.9 -1,402 -819 Medium Average 45 -42.0 27.8 24.8 35 29 29 40 29 28 37 8.34 33 43 29 25.5 Median 52 21.6 37.9 44.4 47 41 41 51 41 32 55 38.6 40 57 38 24.0 Maximum 84 66.8 77.9 92.1 87 67 67 76 67 72 87 96.9 71 83 75 73.5 Minimum -30 -342 -106 -195 -75 -47 -47 -23 -47 -56 -75 -252.1 -24 -31 -36 -131 Fine Average 40.6 34.9 23.1 -7.59 25.5 -12.2 31.3 26.9 27.5 30.6 36.0 34.5 30.6 32.5 35.0 22.7

Median 79.1 84.5 70.2 78.0 77.0 73.7 73.7 73.1 73.7 74.1 75.5 79.9 72.3 73.9 71.0 75.5Maximum 96.4 99.2 96.0 93.7 96.8 96.7 94.8 95.6 94.8 95.5 94.3 95.3 94.6 96.9 95.1 96.4Minimum -253 -330 -389 -590 -395 -752 -249 -332 -249 -298 -197 -182 -259 -323 -236 -423
Table 12 55

Table 12. Percent washoff of constituent masses in terms of grain-size fraction and land-use type from street-solid composite samples collected before and after 6 storms with a recorded rainfall volume range of 0.32 to 1.71 inches, Cambridge, Massachusetts.—Continued[Negative values indicate a net increase of material; mm, millimeter; coarse, greater than or equal to 2 mm; medium, less than 2 mm greater than or equal to 0.125 mm; fine, less than 0.125 mm in diameter]

Magnesium Manga- nese Molybde- num Sodium Nickel Phospho- rus Lead Anti- mony Scan- dium Tin Strontium Titanium Vana- dium Tung- sten Yttrium Zinc Zirconium

Multifamily all grain-size fractions

Average -11.03 3.406 5.228 18.71 -7.953 -2.055 -44.70 -7.46 -30.02 -45.71 -6.181 -21.34 -69.38 17.77 -68.53 -42.05 -77.04

Median 60.39 56.31 59.53 68.99 46.58 57.97 48.48 37.99 54.93 50.77 56.85 53.48 51.29 39.75 52.32 43.51 32.72Maximum 98.09 93.48 93.78 97.05 91.77 93.28 96.44 92.53 95.13 99.12 94.44 92.53 93.99 92.53 93.42 95.43 97.33Minimum -1,211 -1,126 -876 -1,120 -1,088 -1,120 -1,913 -1,120 -1,204 -2,339 -1,412 -1,120 -2,884 -375 -2,799 -1,246 -2,725

Coarse

Average -13.6 11.8 -11.8 30.8 -16.0 -9.03 -20.7 -5.74 -57.07 -0.93 4.52 -48.9 -170.7 8.02 -168.3 -96.20 -78.3

Median 70.8 42.3 21.0 49.1 27.7 39.4 33.2 21.0 39.75 39.7 62.4 49.1 14.94 21.2 37.99 33.43 -30.6

Maximum 98.1 91.4 89.7 94.5 86.8 89.7 85.2 91.4 95.13 95.5 89.4 83.4 87.67 86.8 86.12 87.99 97.3Minimum -523 -230 -286 -163 -326 -467 -621 -286 -1,204 -358 -395 -468 -2,884 -286 -2,799 -1,020 -636

Medium

Average 18.4 29 44.1 44 32 31 -26.2 22 0.605 30.9 25 22.3 22.1 25 14.5 18.2 -23.5Median 20.3 46 59.5 63 45 39 28.3 33 47.9 43.2 29 43.2 43.9 34 39.4 37.0 22.7Maximum 71.5 64 93.4 86 89 66 70.0 63 86.7 95.2 63 76.7 69.0 63 75.7 84.6 78.2Minimum -106 -86 -110 -64 -85 -39 -467 -64 -426 -114 -64 -119 -128 -64 -248 -289 -558

Fine

Average -37.50 -31.27 -14.3 -20.53 -38.75 -27.32 -90.42 -39.31 -29.98 -173.1 -49.90 -33.72 -46.08 21.7 -38.48 -40.89 -129.2

Median 74.53 75.31 76.0 85.63 76.79 75.59 75.16 75.38 77.28 51.84 76.52 75.31 75.38 75.4 78.55 73.07 84.33Maximum 94.23 93.48 93.8 97.05 91.77 93.28 96.44 92.53 93.73 99.12 94.44 92.53 93.99 92.5 93.42 95.43 95.82Minimum -1,211 -1,126 -876 -1,120 -1,088 -1,120 -1,913 -1,120 -1,120 -2,339 -1,412 -1,120 -1,323 -375 -1,208 -1,246 -2,725

Commercial all grain-size fractions

Average -7.20 -9.65 -1.75 40.9 -0.433 29.9 12.32 27.7 -20.57 -34.49 32.7 -9.2 -10.5 26.3 -15.0 30.6 -31.27

Median 43.1 44.4 63.3 73.9 42.1 48.1 64.33 39.5 42.84 25.87 51.8 40.0 40.2 39.5 33.1 52.0 27.72Maximum 95.8 95.4 95.5 97.6 94.9 99.3 96.33 96.7 95.64 99.05 95.9 95.1 95.5 94.8 95.1 96.8 95.98Minimum -847 -911 -1,338 -365 -637 -214 -1,004 -249 -1,056 -2,360 -289 -557 -401 -249 -892 -410 -1,791

Coarse

Average -71.2 -79.3 -66.70 36.2 -20.7 15.9 26.1 24.6 -96.1 8.33 33 -77.1 -82.9 21 -89.8 31 -122.4Median 33.4 9.82 44.48 64.7 13.4 34.4 45.5 20.4 27.2 14.2 38 -44.9 -48.1 18 -43.5 42 -0.3969Maximum 93.8 92.4 89.38 97.6 84.1 99.3 89.9 89.4 89.4 94.4 89 89.4 89.4 89 87.3 92 91.66Minimum -847 -911 -1,338 -220 -393 -176 -118 -75 -1,056 -362 -83 -557 -401 -59 -892 -61 -1,791

Medium

Average 35 32 39.1 57 -12.9 40 -4.679 29 23 15 38 33 35 29 25 45 12Median 35 42 72.2 74 29.2 51 72.27 41 36 22 48 41 41 41 40 40 26Maximum 75 69 89.0 96 77.2 89 96.33 67 76 94 82 78 80 67 71 92 63Minimum -5 -40 -103 -13 -637 -18 -1,004 -47 -129 -89 -44 -96 -41 -47 -84 -12 -66

Fine

Average 24.3 29.3 33.0 33.4 34.1 38.3 13.5 31.5 22.6 -131.3 29.2 27.0 27.7 31.3 31.2 18.4 28.5Median 72.8 69.9 80.4 82.5 74.6 77.3 73.1 73.7 72.5 53.7 73.5 67.6 75.6 73.7 71.7 79.1 74.3Maximum 95.8 95.4 95.5 97.5 94.9 96.3 95.2 96.7 95.6 99.0 95.9 95.1 95.5 94.8 95.1 96.8 96.0Minimum -354 -265 -249 -365 -189 -214 -347 -249 -372 -2,360 -289 -336 -315 -249 -278 -410 -264
56 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

Table 13. Median percent reductions for total and grain-size fractions of constituents measured in seasonal composite of street-solid 

yields collected before and after a single pass of a regenerative-air street cleaner on streets representing multifamily and commercial 

land-use types in Cambridge, Massachusetts.

[Bold italicized values indicate less than one-half the detection limit was used to determine concentration and normalized mass. Negative values indicate a 

potential net increase of a constituent. n, number of samples; mm, millimeter; coarse, greater than or equal to 2 mm; medium, less than 2 mm greater than or 

equal to 0.125 mm; fine, less than 0.125 mm in diameter; spring, May to June, 2010; summer, July to September, 2010; fall, October to December, 2010]

Multifamily

Analyte Spring, n = 12 Summer, n = 17 Fall, n = 12

Total Coarse Medium Fine Total Coarse Medium Fine Total Coarse Medium Fine

Organic carbon 80 93 87 60 87 93 90 57 94 97 96 81

Silver 78 92 83 55 84 93 93 66 94 98 92 66

Aluminum 78 90 84 60 79 91 87 42 93 98 59 37

Arsenic 70 98 66 55 77 90 83 11 90 94 73 -171

Barium 85 91 85 62 80 90 83 12 93 98 92 46

Beryllium 78 92 83 55 84 93 86 66 94 98 92 66

Bismuth 78 92 83 55 84 93 86 66 94 98 92 66

Calcium 79 90 88 57 89 96 85 48 93 98 94 78

Cadmium 78 92 83 55 84 93 86 66 94 98 92 66

Cobalt 67 85 83 50 84 93 86 31 94 99 59 32

Chromium 55 87 76 60 80 89 82 18 98 97 84 -81

Copper 74 97 78 70 90 88 92 21 97 99 88 -141

Iron 75 89 81 58 80 90 86 48 95 95 49 23

Potassium 86 96 87 66 90 96 88 50 94 98 94 69

Lanthanum 76 88 81 54 71 88 85 23 92 81 4 11

Lithium 75 86 85 65 82 83 90 59 95 97 59 42

Magnesium 70 89 84 57 85 93 87 50 94 98 80 51

Manganese 75 88 84 58 81 88 88 57 94 96 87 51

Molybdenum 67 96 74 55 84 93 86 43 98 95 84 15

Sodium 85 92 83 67 84 93 72 -3 90 91 76 32

Nickel 69 85 77 58 80 90 83 10 95 97 85 -88

Phosphorus 82 94 86 64 99 100 99 97 94 96 93 66

Lead 70 94 62 64 80 85 83 -13 93 97 57 -18

Antimony 78 92 83 55 84 93 86 66 94 98 92 66

Scandium 72 81 84 62 84 88 86 44 95 98 64 32

Tin 94 96 97 70 92 97 44 -37 98 98 92 -1,050

Strontium 80 92 84 60 85 90 88 45 92 98 94 78

Titanium 82 92 86 60 84 91 86 48 94 98 51 24

Vanadium 72 87 81 53 79 91 86 31 95 98 63 26

Tungsten 78 92 83 55 84 93 86 66 94 98 92 66

Yttrium 78 90 84 54 79 88 86 41 94 91 61 27

Zinc 77 94 81 62 76 95 85 22 95 98 86 13

Zirconium 78 74 86 52 79 87 82 59 94 98 82 2
Table 13 57

Table 13. Median percent reductions for total and grain-size fractions of constituents measured in seasonal composite of street-solid 

yields collected before and after a single pass of a regenerative-air street cleaner on streets representing multifamily and commercial 

land-use types in Cambridge, Massachusetts.—Continued

[Bold italicized values indicate less than one-half the detection limit was used to determine concentration and normalized mass. Negative values indicate a 

potential net increase of a constituent. n, number of samples; mm, millimeter; coarse, greater than or equal to 2 mm; medium, less than 2 mm greater than or 

equal to 0.125 mm; fine, less than 0.125 mm in diameter; spring, May to June, 2010; summer, July to September, 2010; fall, October to December, 2010]

Commercial

Analyte Spring, n = 12 Summer, n = 17 Fall, n = 15

Total Coarse Medium Fine Total Coarse Medium Fine Total Coarse Medium Fine

Organic carbon 70 94 78 59 83 91 79 72 92 96 93 85

Silver 37 85 73 82 37 91 35 61 88 96 89 73

Aluminum 51 47 75 56 74 86 76 68 83 96 87 74

Arsenic 72 97 62 53 79 82 86 56 79 97 88 73

Barium 54 96 60 63 84 88 83 74 84 98 86 76

Beryllium 69 92 73 58 79 91 78 66 88 96 89 73

Bismuth 69 92 73 58 79 91 78 66 88 96 89 73

Calcium 54 92 74 61 71 73 82 70 83 98 93 79

Cadmium 69 92 73 58 79 91 78 66 88 96 89 73

Cobalt 45 -8 66 62 53 85 68 59 86 93 89 73

Chromium 59 80 64 66 66 84 65 68 93 97 87 73

Copper 30 90 11 60 31 84 29 62 90 97 87 60

Iron 64 82 65 61 74 84 73 62 86 93 86 68

Potassium 72 97 79 62 84 94 78 72 84 98 90 79

Lanthanum 68 92 68 60 74 86 73 67 86 87 89 74

Lithium 53 54 73 58 72 85 75 69 83 89 88 73

Magnesium 55 59 75 57 70 83 77 67 85 93 88 76

Manganese 58 94 71 59 76 83 78 64 87 94 85 72

Molybdenum 48 96 31 63 86 91 86 66 94 96 68 73

Sodium 69 96 73 58 79 63 78 81 83 98 89 77

Nickel 64 86 71 66 71 83 70 62 91 95 87 70

Phosphorus 62 96 73 63 97 99 97 98 83 97 89 79

Lead 73 98 76 66 65 90 63 57 93 98 95 78

Antimony 69 92 73 58 79 91 78 66 88 98 89 73

Scandium 53 54 75 58 77 88 74 66 83 88 87 79

Tin 84 92 73 58 58 82 14 66 94 96 89 91

Strontium 66 93 77 64 73 83 75 68 81 97 93 78

Titanium 61 61 73 58 74 77 73 63 80 94 85 77

Vanadium 61 50 70 58 72 87 75 65 87 94 88 76

Tungsten 69 92 73 58 79 91 78 66 88 96 89 73

Yttrium 73 93 77 59 73 87 75 69 86 87 89 75

Zinc 70 96 60 63 75 85 74 73 86 99 88 80

Zirconium 60 90 71 44 79 89 77 70 88 96 84 71
THIS PAGE INTENTIONALLY LEFT BLANK
Appendix 1 59

Appendix 1. Supplemental Data Tables

Tables included on accompanying CD–ROM

Tables

1–1. Curb-to-curb street-solid composite sample collection dates, start times, locations, 

intake nozzle widths and resulting masses and yields

1–2. Single-sided street cleaner removal efficiency composite sample pair collection 

dates, start times, locations, intake nozzle widths and resulting masses and yields

1–3. Curb-to-curb street-solid composite sample collection dates, start times, locations, 

intake nozzle widths and resulting total-recoverable concentrations by grain size 

for multifamily streets

1–4. Curb-to-curb street-solid composite sample collection dates, start times, locations, 

intake nozzle widths and resulting total-recoverable concentrations by grain size 

for commercial streets

1–5. Seasonal mixtures of single-sided street-solid composite samples, locations, and 

resulting total-recoverable concentrations by grain-size for multifamily streets 

before and after regenerative-air street cleaner operation

1–6. Seasonal street mixtures of single-sided street-solid composite samples, locations, 

and resulting total-recoverable concentrations by grain-size for commercial 

streets before and after regenerative-air street cleaner operation
THIS PAGE INTENTIONALLY LEFT BLANK
Appendix 2 61

Appendix 2. Source Loading and Management Model for 

Windows (WinSLAMM)

Functional Description of SLAMM

The Source Loading and Management Model for 

Windows (WinSLAMM) uses a mass balance approach to 

track particulate and dissolved constituents associated with 

as many as six different land-use types and their source 

areas, taking into account a variety of rainfall conditions 

and source-area control measures. Runoff, constituent mass 

discharge and effects of selected control practices are the 

primary model output. SLAMM also can output other types of 

information such as the relative contribution of source areas 

within each land-use type and generation of National Resource 

Conservation Service (NRCS) curve numbers that represent 

the modeled land-use and control measures. 

The model emphasizes the concept of small storm hydrology and particulate washoff to better simulate stormwater 

quality. This emphasis follows a major finding of the National 

Urban Runoff Program (NURP)-era work indicating small 

rainstorms represent the largest proportion of the annual urban 

runoff discharge quantities (U.S. Environmental Protection 

Agency, 1983; Pitt, 1987). The model also takes into account 

the findings of Maestre and Pitt (2005), where log-transformed 

constituent concentration data in stormwater generally have a 

lognormal distribution between the 5th and 95th percentiles. A 

Monte Carlo option in the model provides the means to determine variations in the constituent concentrations in source 

area runoff and provide median values used for mass balance 

calculations. This feature can be deactivated and discrete 

concentration can be used to allow evaluations of extreme 

concentrations. SLAMM also can be used with other models 

such as the Hydrologic Simulation Program Fortran (HSPF) 

and the StormWater Management Model (SWMM) to improve 

simulations of stormwater and water-quality controls.

Simulations in SLAMM require six input parameter files, 

which are based on actual data collected from many different 

studies across the United States and Canada since the late seventies and continue to be modified as new data become available. It is possible to simulate different stormwater control 

practices using precipitation data from a single year or several 

decades. SLAMM simulations can yield accurate predictions 

of stormwater quality for a drainage area with only limited 

ancillary information. 

Local outfall stormwater quantity and quality data from 

several watersheds with relatively homogeneous land uses 

should be collected and used to calibrate SLAMM. Ideally, 

data from one set of watersheds or subcatchments should 

be used to calibrate the model, and data from the remaining 

subcatchments used to verify model performance. Alternatively, a subset of data from a single location can be used for 

model calibration and any remaining data from the same location used for verification. These approaches assume availability of good quality data. However, available data for this study 

were limited in number and quality.

Input Data used for Modeling of Land-Use 

Subcatchments

Land-use types and their respective source areas as 

input to SLAMM are provided in appendix table 2–1. About 

36 percent of the commercial subcatchment is considered 

multifamily or high-density residential land use (referred to as 

multifamily), about 17 percent institutional, and about 47 percent commercial land use. The model treats institutional and 

commercial areas the same, so the effective commercial land 

use is about 64 percent. 

Drainage systems and other control practices must also 

be identified. SLAMM parameter files (table 2–2) must be 

input and modified as needed following their general order of 

calibration. Required information and the data contained in the 

parameter files used for SLAMM simulations of the commercial subcatchment are discussed in the following sections.

Delineation of Land-Use Types and SourceAreas

Characterization of land-use types and their respective 

source areas within the model subcatchments were delineated 

from impervious surface geographic information system (GIS) 

2010 coverages generated by the city of Cambridge/MassGIS 

basemap development project (Cambridge Department of 

Public Works, written commun., 2011, table 2–1). Using the 

municipal GIS layers, which provided greater source-area 

resolution than the 1-meter (m) impervious surface raster layers based on 2005 0.5-m color ortho mosaic index (MassGIS, 

2011), all constructed surfaces and areas of man-made compacted soils were considered impervious. All surface waters, 

wetlands, natural and man-made vegetated areas were considered pervious. Roof, driveway, and other impervious surface 

drainage were further evaluated in the field to determine connectivity. If runoff drained less than 20 feet of pervious area, 

the drainage was considered directly connected.
62 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

Table 2–1. Source-area designations and respective areas as input to SLAMM model within the commercial subcatchment, 

Cambridge, Massachusetts (Based on 2010 land-use coverages, city of Cambridge/MassGIS basemap development project).

[--, no data]

Subcatchment source areas

Mutlifamily and high-density 

residential land use

(acres)

Commercial 

land use

(acres)

Public/urban/institutional land use

(acres)

Total area

(acres)

Source area 

proportion of total 

(percent)

Roofs flat 1.69 3.17 1.37 6.24 28.66

Roofs-flat, disconnected 0.47 -- -- 0.47 2.16

Roofs-pitched 0.57 0.56 0.13 1.26 5.80

Roofs-pitched, disconnected 0.01 0.09 0.05 0.15 0.68

Paved parking/storage 0.62 1.73 0.47 2.81 12.93

Driveways 0.61 0.76 0.04 1.41 6.50

Driveways-disconnected 0.04 -- -- 0.04 0.18

Sidewalks/walks 0.54 1.22 0.11 1.87 8.59

Sidewalks/walks-disconnected 0.07 -- 0.14 0.21 0.98

Street area 0.82 2.23 0.46 3.52 16.15

Large/small landscaped area 2.48 0.40 0.90 3.78 17.37

Total subcatchment area (acres) 7.93 10.16 3.67 21.76

Proportion of total area (percent) 36.45 46.70 16.86

Soils

Soils in the subcatchment area (Middlesex County) typically are considered disturbed urban glacio-fluvial outwash 

(U.S. Department of Agriculture, 1995). Despite highly 

permeable classifications of parent soils, pervious areas were 

represented as “silty” rather than “sandy” within the model to 

account for the effects of compression and buildup of fugitive 

dust that substantially reduce native soil permeability (Pitt and 

others, 2008).

Control Practices

The city has a well-defined curb-and-gutter drainage 

system equipped with about 15-inch (in.) high granite curbstone set at roughly 90 degrees to the road surface (fig. 4). 

Catchbasins are incorporated into the drainage system and are 

cleaned about twice a year. SLAMM version 9.4.0 is unable 

to simulate catchbasins and street cleaning simultaneously, 

and catchbasins were not specified. The city uses a monthly 

street-cleaning program with parking controls between April 

and December that uses mechanical brush sweepers. The 

tandem street cleaning approach (mechanical brush followed 

by vacuum assist) applied during the months of April and 

November was not simulated. In addition, many commercial 

areas and city squares that are swept weekly or daily were also 

not included in the model. 

Base model simulations used to compare with flow and 

water-quality data collected in 1999–2000 were run by specifying monthly mechanical-brush street cleaning in the model. 

Productivity function coefficients provided with SLAMM 

for mechanical-brush street cleaners (slope, M = 0.85 and 

y-intercept, B = 310) were used. Model performance also was 

evaluated by comparing simulated street-dirt yield to streetdirt observations from 2009–2011. These simulations specified monthly vacuum-assist street cleaning using productivity 

function coefficients developed from the regenerative-air street 

cleaner observations in Cambridge.

Street-Solid Accumulation

The observations of material accumulation on street 

surfaces in Cambridge collected in 2010–2011 were used to 

populate SLAMM accumulation coefficients. The average 

accumulation rate for streets in multifamily areas (M) was 

set to 30 pounds per curb-mile per day (lbs/curb-mi/day), 

the intercept load (B) was set to 225 lbs/curb-mi, and the 

maximum load (C) was set to 3,800 lbs/curb-mi. The endof-winter (EOW) load for residential land-use streets was set 

at 2,600 lbs/curb-mi. Commercial and institutional land-use 

accumulation coefficients M, B, C and EOW were set to 20, 

225, 1,400, and 4,800, respectively.
Appendix 2 63

Table 2–2. Parameter files and other model data required to develop SLAMM for the commercial subcatchment Cambridge, Massachusetts.[SSC; suspended sediment concentrations]

Parameter file name File type Description Initial data source Regional source data

Rain *.RAN Rainfall depths, durations and interevent time 

periods; Special rain file contains typical rain duration data to determine percent contribution of runoff from each source area for various rain events

National Climatic Data Center, Boston Logan Airport; 

Cambridge Department of Public Works; U.S. Geological Survey MA-RI WSC

National Climatic Data Center, Boston 

Logan Airport

Runoff coefficient *.RSV Contains volumetric runoff coefficients for 

each surface type for various rain depths. Must be calibrated before any other parameter files are evaluated.

Bannerman and others, 1983; Pitt and others, 2005a, 

b, and c; Pitt and Shawley, 1981; Pitt, 1982; Pitt and McLean, 1984; and Shelley and Gadboury, 1985

Verified runoff coefficients from 8 

study sites in Milwaukee and 2 sites in Toronto. Modified verified runoff coefficient file to better match 1999–2000 runoff data and runoff data

Particulate solids 

concentration

*.PSC Describes SSC for each source area and land 

use for several rain categories (except road and highway surfaces)

Bannerman and others, 1983; Pitt and others, 2005a, 

b, and c; Pitt and Shawley, 1981; Pitt, 1982; Pitt and McLean, 1984; and Shelley and Gadboury, 1986

No modifications

Particulate residue reduction (Particulate 

solids delivery)

*.PRR Calibrates source-area predictions of SSC to 

outfall observations to account for deposition of particulates within the storm drainage system

Bannerman and others, 1983; Pitt and others, 2005a, 

b, and c; Pitt and Shawley, 1981; Pitt, 1982; Pitt and McLean, 1984; and Shelley and Gadboury, 1986

Not used-obselete file

Street-dirt delivery *.STD More accurately accounts for deposition of 

street-dirt washoff material

Bannerman and others, 1983; Pitt and Shawley, 1981; 

Pitt, 1982; Pitt and McLean, 1984; and Shelley and Gadboury, 1986

No modifications

Pollutant probability 

distribution (Event particulate solids loading)

*.PPD Particulate pollutant concentrations related to 

particulate and filterable pollutant concentrations for each source area and land use (optional unless modeling chemical constituents)

Bannerman and others, 1983; Pitt and others, 2005a, 

b, and c; Pitt and Amy, 1973; Pitt, 1979; Pitt and Shawley, 1981; Pitt, 1982; Pitt and Bozeman, 1982; Pitt, 1985; Pitt and McLean, 1984; Sartor and Boyd, 1972; Shaheen, 1975; Shelley and Gadboury, 1986; and Terstriep and others, 1982

No modifications

Particle size diameter *.CPZ Critical particle size U.S. Environmental Protection Agency, 1983 Not used for street-cleaning simulations
64 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

231,700 231,800 231,900 232,000 232,100 232,200

902,000 902,100 902,200 902,300 902,400 902,500 902,600

Northings and eastings in state plate meters

Orthophoto 2005, MassGIS, land-use coverage 2010, City of Cambridge 

BROADWAY

MASSACHUSETTS AVENUE

MOUNT AUBURN STREET

MASSACHUSETTS AVENUE

USGS ID: 01104677

0 50 100 150 200 METERS

0 164 328 492 656 FEET

EXPLANATION

Commercial subcatchment 14.6 acres

Commercial subcatchment 21.8 acres

USGS flow and water-quality station 

1999–2000

Commercial land use

Multifamily residential and use

Institutional/Public urban land use

High-density residential and use

Participation recreation land use

Industrial land use

BANKS STREET

Figure 2–1. Predominantly commercial land-use subcatchment in Cambridge, Massachusetts, and United States 

Geological Survey flow and water-quality monitoring station (1999–2000; USGS ID: 01104677). Orthophoto 2005, MassGIS, 

and land-use coverages 2010, based on city of Cambridge/MassGIS basemap development project.
Appendix 2 65

Rainfall

Initial model runs used 62 years of rainfall data from 

Logan Airport in Boston, Massachusetts (1948–2010 COOP 

ID: 190770) available through the National Climatic Data 

Center (NCDC, 2011). Storms with rainfall less than 0.1 inch 

were omitted from all *.RAN files, (that is, only runoff 

producing storms were considered). A special *.RAN file was 

created from the long-term Logan Airport data to determine 

the average storm duration of storm depths between 0.10 to 

5.00 in. SLAMM runs using the special *.RAN file estimated 

the relative contribution of runoff from each source area 

through the range of storm volumes and provided the basis 

for any modifications to runoff coefficient *.RSV parameter 

files. Logan Airport rainfall data were also used to evaluate 

simulated outfall runoff and loading compared to waterquality data collected in 1999–2000. Additional *.RAN files 

developed using precipitation records from the Cambridge 

Department of Public Works (DPW) Hampshire Street 

gage supplemented by the USGS Fresh Pond gage (USGS 

ID: 422302071083801) during winter months were used to 

evaluate model performance in terms of street-dirt loading 

observations in 2009–2011. 

The base model that provided acceptable estimates 

of runoff and street-dirt loading was run using 5 years of 

precipitation data from Logan Airport. The five average years 

were selected by comparison of annual discharges from the 

USGS Aberjona River at Winchester, Mass. gage (USGS gage 

ID: 01102500, located about 7 miles north of Cambridge) 

with the 70-year mean annual flow of 31 cubic feet per second 

(ft3/s) reported at the gage (Bent and others, 2009). Years with 

annual average discharge within 4.5 percent of the 70-year 

mean annual flow at the USGS Aberjona River at Winchester, 

Mass. gage were 1948, 1953, 1961, 1986, and 1991. Model 

runs using a *.RAN file based on these data allowed SLAMM 

to generate average estimates of street cleaner performance 

in terms of total and particulate solid and phosphorus 

(P) reductions.

Runoff

Runoff coefficient (Rv) parameter files (*.RSV) contain 

ratios of runoff quantity to rainfall volume for all modeled 

surface types for rain depths measuring from 0.01 to 5 in. The 

WI_SL06 Dec06.RSV file provided with the model initially 

was used, and examination of the relative contribution of 

source areas generated by the model run using the special 

*.RAN file, runoff coefficients were modified in a stepwise 

manner to improve agreement between simulated results and 

runoff data from 1999–2000. Runoff coefficient increases 

between 0.05 and 0.10 were determined to be sufficient to 

better match simulated and observed outfall flows. 

Particulate Solids Concentration

Suspended solids concentrations (SSCs) associated with 

source areas from each land use over a range of rain depths 

is contained in the particulate solids concentrations (*.PSC) 

file. Build-up and washoff functions directly predict roads 

and highway surface SSCs, and are not included in the *.PSC 

file (Pitt and Voorhees, 2000). The WI_AVG01.PSC file 

(appendix table 2–2) provided with the model is based on data 

from Madison, Wisconsin, that represents the best average 

particulate solids information. No new outfall SSC data were 

collected in Cambridge to support modifications to this *.PSC 

file, and therefore the WI_AVG01.PSC file was used for 

calibration and subsequent SLAMM simulations. 

Two additional parameter files are used to describe 

the transport of particulates in SLAMM. The first file is the 

particulate residue reduction file (*.PRR), and was designed to 

account for the deposition of particulates in the storm drainage 

system before the outfall or outfall controls (Pitt, 2008; Pitt 

and Voorhees, 2000). Particulate deposition in the storm 

drainage system, however, is now directly calculated, making 

the *.PRR file obsolete (Pitt, 2008). SLAMM still requires a 

*.PRR file to be specified, and the file WI_DLV01.PRR, set 

to zero, was used as a placeholder in the model. The second 

additional file is the street-dirt delivery file (*.STD). These 

files account for the fraction reduction in street dirt yield 

during washoff events measuring from 0.04 to 3.2 in. Fraction 

washoff is applied to street surfaces with textures ranging 

from smooth to rough within each land-use type. The files 

WI_Res and Other Urban Dec06.STD, WI_Com Inst Indust 

Dec06.STD, and Freeway Dec06.STD were used in the model. 

These files typically show 100-percent washoff for all surface 

types for storm depths greater than 0.60 inches. Changes to 

washoff coefficients are not possible in SLAMM version 9.4. 

Washoff data calculated as part of this study are not used in 

the following simulations.

Pollutant Concentrations

The *.PPD file contains particulate and dissolved pollutant concentrations associated with each source area for each 

land-use type specified in the model. This file only needs to be 

specified for constituents other than particulate solids. Coefficient of variation (COV) values included for each constituent 

for Monte Carlo simulations (Pitt, 2008; Pitt and Voorhees, 

2000). The WI_GEO01.PPD file (appendix table 2–2) was 

applied to model the Cambridge commercial subcatchment. 

The critical particle size file (*.CPZ) is primarily designed to 

assist evaluations of wet detention ponds and other structural 

stormwater control measures SCMs. SLAMM comes with several *.CPZ files that describe particle size ranges in areas associated with low to high particulate residue concentrations as 

well as files that contain the average of the NURP-era studies 

and a regionally-specific *.CPZ file. The critical particle size 

parameter file was not necessary for SLAMM simulations of 

street cleaning in this study, and no *.CPZ file was specified. 
66 Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009–11

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Prepared by the Pembroke and Rolla Publishing Service 

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For more information concerning this report, contact:

Office Chief

U.S. Geological Survey

New England Water Science Center 

Massachusetts-Rhode Island Office

10 Bearfoot Road

Northborough, MA 01532

dc_ma@usgs.gov

or visit our Web site at:

http://ma.water.usgs.gov
Sorenson—Potential Reductions of Street Solids and Phosphorus from Street Cleaning, Cambridge, Massachusetts, 2009−11—Scientific Investigations Report 2012–5292

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