1. Deriving Reliable Pollutant Removal Rates for Municipal Street Sweeping and Storm Drain Cleanout Programs
A project funded by U.S. EPA Chesapeake Bay Program
Urban Stormwater Work Group
June 27, 2006

2. About the Center for Watershed Protection
Non-profit 501(c)3, non-advocacy organization
Work with watershed groups, local, state, and federal governments
Provide tools communities need to protect streams, lakes, and rivers
20 staff in Ellicott City, MD

3. Project Partners UMBC (Engineering, CUERE) City of Baltimore, DPW
Baltimore County, DEPRM
USDA Forest Service, Baltimore Ecosystem Study

4. Topics to be Covered Purpose of the study Nature of the study area
Project study tasks
Initial pollutant removal rates
Findings from Chesapeake Bay survey
Other CWP resources

5. Study Purpose
Muncipalities are sweeping and cleaning storm drains – can it make a difference in reducing nutrient loads to Bay?
Very limited and conflicting data on the performance of these practices in removing nutrients and other pollutants
Need more reliable estimates of the potential nutrient and sediment reductions achieved by municipal street sweeping and storm drain cleanouts

6. Watershed 263 Watershed 263 Location Map Watershed 263 Catchments
Catchment F
Watershed 263
Catchment O
Location Map
Watershed 263 Catchments

7. Catchment characteristicsF O
Total Area (Acres)
38.4
38.7
Impervious Cover
68%
77%
Pervious Cover
32%
23%
Catchment F
Catchment O

8. Assessment of Relative Dirtiness of Streets in Catchment O (CWP 2005)

9. Storm EMCs for TSS, TN and TP
Median pretreatment water quality
Parameter
(mg/L)
Catchment O
Stormflow
baseflow
Catchment F
stormflow
Baseflow
National
Storm EMC
Suspended Solids
93.0
3.0
52.0
9.0
58.0
Total P
0.33
0.40
0.30
0.07
0.27
Total N
3.2
5.62
2.11
2.60
2.0

10. Streets and Storm Drain Inlet Conditions
The Bad
The Ugly
The Good

11. Project Study Tasks Task 1: Literature Review and Reference Tracking
System
Task 2: Basin-wide Municipal Practices Survey
Field monitoring program
Task 3: Paired Street Sweeping Treatment
Task 4: Street Source Area Sampling
Task 5: Characterization of Stormdrain Sediment

12. Catchment Monitoring Street Sweeping Treatments Rain gauge at
Harlem Park E.S.
Elgin Whirlwind vacuum
Street sweeper
Water quality sampling
(ISCO sampling station)

13. Street Sweeping Treatments
Catchment F
Treatment #1 = moderate street sweeping effort (status quo)
Treatment #2 = 85% reduction in curb miles swept.
Catchment O
Treatment #1 = moderate street sweeping effort (status quo)
Treatment #2 = 48% increase in curb miles swept
Treatment #3 =48% increase in curb miles swept and storm drains cleanout

14. Task 4: Source Area Sampling of Streets
4 treatment street sections
2 controls street sections
3 samples types
S: after street sweeping
A: accumulation
W: washoff
(From Burton and Pitt 2001)

15. Task 5: Characterization of storm drain sediment
100 accumulation samples
Accumulation rate sample design.
Residential
Commercial/Industrial
Gwynns Falls (Piedmont)
25 inlets
Baltimore Harbor (Coastal Plain)

16. Task 5: Characterization of storm drain sediment
Total 100 accumulation samples
Subset 16 for chemical analyses
TSS, TS
TKN, NO2+NO3
TP, PO4
BOD, COD
Total Cu, Pb, Zn, Cd

17. Street Sweeping Review Key Findings
75 monitoring and modeling studies were reviewed from the 1970s to present
Few studies provided sufficient data to quantify a removal rate
Considerable differences in scope, extent and design of field or modeling studies.
Pollutant removal rates vary widely based on sweeping frequency, sweeper technology and operation, street conditions, and the chemical and physical characteristics of street dirt.
New street sweeping technology can pick up more than 90% of street dirt under ideal conditions, BUT does not guarantee water quality improvements

18. Review of Catchbasin Studies
Only a handful of studies monitored the pollutant reduction and the optimal frequencies for cleanouts at a catchment scale.
Cleanouts may reduce pollutants by 5 to 25% depending on catchment conditions, cleaning frequency and type of pollutant.
Pollutant removal capability of catchbasins is constrained by the design which retains coarse grained sediments but bypass finer grained sediment (containing higher loads of nutrients).

19. Conceptual Model
Conceptual model was developed to provide interim pollutant removal rates for TSS, TN and TP. The bounding conditions and assumptions were made based on the literature
What’s available
to be picked up
by street Sweeper
How well can the
street sweeper remove
the street dirt?
What’s on the streets

20. Atmospheric Deposition (+) Vehicle Emissions (+) Littering (+)
STREET DIRT LOAD
Runon (+)
Atmospheric Deposition (+)
Vehicle Emissions (+)
Littering (+)
Sanding (+)
Breakup of Street (+)
Organic Matter (+)
Others (+)
TREATABLE LOAD
Washoff (-)
Unswept Areas (-)
Street Cracks (-)
Curb (-)
SWEEPER EFFECTIVENESS
Frequency
Technology
Street Condition
Operator Effort
DISPOSED STREET DIRT
lb/curb-mile
INLET TRAPPING EFFICIENCY
Type of Inlet
Capacity of Inlet
CLEANOUT EFFECTIVENESS
Frequency
Removal Method
DISPOSED SEDIMENT
lb/square feet
LEGEND
(+) Processes and material contributing to
street dirt load
(-) Processes and factors that remove
street dirt or is not picked-up by street
sweepers

21. Interim Pollutant Removal Rates for Sweeping
Discounted for:
Solubility
Washoff & fugitive dust loss
Runon*
Frequency
Technology*
Parked cars
Street conditions
Frequency
TP removal
Monthly
4 %
Twice a month
5 %
Weekly
Twice a Week
8 %

22. Interim Rates for Catchbasin Cleanouts
Discounted for
Frequency
Particle size distribution of dirt load
% catch basin or inlet full
Cleanout method*
Frequency of cleanout
% TN Removal
Annual 5
Semi-annual 10

23. CB Municipal Practice Survey
4 sections
43 questions
Community condition
Street Sweeping practice
Stormdrain maintenance
Monitoring
73% response rate
Distribution of 37 surveys
Phase I communities and agencies (23, 16)
11 Maryland
11 Virginia
1 Pennsylvania
Phase II permit communities (6, 4)
1 Maryland
3 Virginia
1 West Virginia
Greater United States (8, 7)
Pennsylvania, Wisconsin, Minnesota, Florida, Texas, California

24. Street Sweeping Findings
$14.75 to $75/curb mile
85% of Phase I and II communities sweep more frequently than annually (17)
How frequent?
What proportion of public streets are swept at least on an annual basis?*
Proportion
100%
76-99%
50-75%
Up to 50%
Response
41.2% (7)
11.8 %(2)
29.4% (5)
17.6% (3)**
* no data for 3 surveys
** One community indicated different proportion of streets for urban vs rural.

25. Percentage of communities (not streets) that sweep streets more frequently than 1x/yr
2x/year
(14%)
Other
(26%)
Monthly
(20%)
Daily
(14%)
2x/month
(9%)
Weekly (17%)

26. Most Common Street Sweeping Technology used by Phase I CB Communities (n=17*)
*Total surveys responded to this questions is 16, but one community had an equal
number of two different technologies.

27. Key Findings: Storm drain cleanout
Of 20 responses,
8 regular schedule cleanouts
12 response to complaints or clogging
$1.39/linear ft; ~$55/catchbasin
What proportion of all storm drains, inlets or catch basins are cleaned out on an annual basis? (n=16)
Proportion
100%
75 < 100%
50< 75%
Up to 50%
Response
6.3% (1)
31.3% (5)
62.5% (10)

28. Most Common Storm Drain Cleanout Methods (n=27*)
*Total surveys responded to this questions is 16, but some communities
indicated more than one type of technology

29. Next Steps Review Requested on Memos 1 & 2 Close gaps
Planned work next 6 to 9 months
Source area sampling of streets
Sediment data from County
Load estimates from Catchments O and F (DPW)
Refine pollutant removal rates

30. Other CWP Work of Interest
Small Watershed Restoration Manual Series
Maryland Watershed Users Guide
Smart Watershed Benchmarking Tool
Urban Watershed Forestry Manuals
Wetland and Watersheds Articles

31. The Small
Watershed
Restoration
Manual Series
Check availability at

32. Manual 2. Methods to Develop Restoration Plans for Small Urban Watersheds
Step-by-step guidance to develop, adopt and implement restoration plans
Features 32 different desktop analysis, field assessment, stakeholder involvement and restoration management methods
Detailed info on plan scoping and budgeting

33. MD Watershed Users Guide
Unified approach to watershed planning
27 key planning principles
Step by step methods
Costs and load reductions
Over 20 planning tools
Get the latest version at and.gov/watersheds/pubs/userguide.html

34. Smart Watershed Benchmarking Tool
Developed to measure integration and activity of 14 municipal watershed restoration programs
56 individual benchmark questions, total 100 pts (plus extra credit)
Benchmarks based on survey of 50 communities across country
Tested in 4 communities in 2005

35. Download for free at www.cwp.org

36. Download for free at www.cwp.org

37. Catchment F
(38.43 acres)
Monitoring
Station

38. Catchment O
(38.7 acres)
Monitoring
Station