Transcript Deriving Reliable Pollutant Removal Rates for Municipal

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
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
www.cwp.org
www.stormwatercenter.net
Project Partners
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UMBC (Engineering, CUERE)
City of Baltimore, DPW
Baltimore County, DEPRM
USDA Forest Service, Baltimore Ecosystem
Study
Topics to be Covered
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Purpose of the study
Nature of the study area
Project study tasks
Initial pollutant removal rates
Findings from Chesapeake Bay survey
Other CWP resources
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
Watershed 263
Catchment F
Watershed 263
Catchment O
Location Map
Watershed 263 Catchments
Catchment characteristics
F
O
Total Area (Acres)
38.4
38.7
Impervious Cover
68%
77%
Pervious Cover
32%
23%
Catchment F
Catchment O
Assessment of Relative Dirtiness of
Streets in Catchment O (CWP 2005)
Storm EMCs for TSS, TN and TP
Median pretreatment water quality
Parameter
(mg/L)
Catchment O
Stormflow
Catchment O
baseflow
Catchment F
stormflow
Catchment F
Baseflow
National
Storm EMC
Suspended Solids
93.0
3.0
52.0
9.0
58.0
0.33
0.40
0.30
0.07
0.27
3.2
5.62
2.11
2.60
2.0
Total P
Total N
Streets and Storm Drain Inlet
Conditions
The Good
The Bad
The Ugly
Project Study Tasks
Task 1:
Task 2:
Literature Review and Reference Tracking
System
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
Catchment Monitoring
Street Sweeping
Treatments
Rain gauge at
Harlem Park E.S.
Elgin Whirlwind vacuum
Street sweeper
Water quality sampling
(ISCO sampling station)
Street Sweeping Treatments
Catchment F
Catchment O
• Treatment #1 = moderate
street sweeping effort (status
quo)
• Treatment #2 = 85%
reduction in curb miles
swept.
• 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
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)
Task 5: Characterization of storm drain sediment
– 100 accumulation samples
Accumulation rate sample design.
Residential
Commercial/Industria
l
Gwynns Falls (Piedmont)
25 inlets
25 inlets
Baltimore Harbor (Coastal
Plain)
25 inlets
25 inlets
Task 5: Characterization of storm drain sediment
• Total 100 accumulation
samples
• Subset 16 for chemical
analyses
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TSS, TS
TKN, NO2+NO3
TP, PO4
BOD, COD
Total Cu, Pb, Zn, Cd
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
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).
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 on the
streets
What’s available
to be picked up
by street Sweeper
How well can the
street sweeper remove
the street dirt?
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
LEGEND
(+) Processes and material contributing to
street dirt load
(-) Processes and factors that remove
street dirt or is not picked-up by street
sweepers
DISPOSED
SEDIMENT
lb/square feet
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
Weekly
5%
Twice a Week
8%
5%
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
CB Municipal Practice Survey
• 4 sections
• 43 questions
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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
Street Sweeping Findings
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.
• $14.75 to $75/curb mile
• 85% of Phase I and II communities sweep more
frequently than annually (17)
• How frequent?
Percentage of communities (not streets) that sweep
streets more frequently than 1x/yr
2x/year
(14%)
Other
(26%)
Monthly
(20%)
Daily
(14%)
Weekly
(17%)
2x/month
(9%)
Most Common Street Sweeping Technology
used by Phase I CB Communities (n=17*)
Vacuum (12%)
Regenerative air
with vacuum assist
(18%)
M echanical Brush
(29%)
M echanical Brush
with vacuum assist
(29%)
*Total surveys responded to this questions is 16, but one community had an equal
number of two different technologies.
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
0
6.3% (1)
31.3% (5)
62.5% (10)
Most Common Storm Drain Cleanout
Methods (n=27*)
Other (4%)
Bucket loaders
(15%)
Manual (19%)
Hydraulic suction
(15%)
Vacuum (48%)
(includes Vacon)
*Total surveys responded to this questions is 16, but some communities
indicated more than one type of technology
Next Steps
• Review Requested on Memos 1 & 2
• Close gaps
• Planned work next 6 to 9 months
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Source area sampling of streets
Sediment data from County
Load estimates from Catchments O and F (DPW)
Refine pollutant removal rates
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
The Small
Watershed
Restoration
Manual Series
Check availability
at www.cwp.org
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
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 http://dnr.maryl
and.gov/watersheds/pubs/userguide.html
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
Download for free at www.cwp.org
Download for free at www.cwp.org
Catchment F
(38.43 acres)
Monitoring
Station
Catchment O
(38.7 acres)
Monitoring
Station