Deriving Reliable Pollutant Removal Rates for Municipal Street
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 • • UMBC (Engineering, CUERE) City of Baltimore, DPW Baltimore County, DEPRM USDA Forest Service, Baltimore Ecosystem Study
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
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 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 Baltimore Harbor (Coastal Plain) 25 inlets
Task 5: Characterization of storm drain sediment • Total 100 accumulation samples • Subset 16 for chemical analyses – – – TSS, TS TKN, NO 2+NO 3 TP, PO 4 BOD, COD Total Cu, Pb, Zn, Cd
Street Sweeping Review Key Findings • 75 monitoring and modeling studies were reviewed from the 1970 s 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 – – 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 1 x/yr 2 x/year (14%) Other (26%) Monthly (20%) Daily (14%) Weekly (17%) 2 x/month (9%)
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.
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*) *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 – 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 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
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