Nebraska Department of Roads Conference 2012 Presented by Dr. Tian Zhang

1. Monitoring Roadway Runoff and
Development of a Design Guide for
Roadway BMPs
John Stansbury, Ph.D., P.E.
Massoum Moussavi, Ph.D., P.E., and Tian Zhang, Ph.D., P.E.

2. Outline
• Introduction
• Field Study
• BMP Design Guide
• Summary

3. Regulatory Background
• Clean Water Act (CWA, 1972): requires NPDES permit
(National Pollutant Discharge Elimination System).
– Municipal Separate Storm Sewer System (MS4)–
discharges/regulation: MS4 defined as: A system of
conveyances owned/operated by a public body.
– Designed or used for collecting or conveying stormwater.
– Not a combined sewer & not part of a POTW.
• MS4s discharges are regulated nonpoint source pollution.
– MS4s regulation is part of the CWA (1987 amended):
Phase I (passed in 1990): requires MS4s to submit Storm
Water Pollution Prevention Plans (SWPPP) to the US EPA.
– Phase II (passed in 1999): requires 6 minimum BMPs.
– The objective of MS4s is to reduce pollutant effluents to
the Maximum Extent Practicable (MEP) (so not linked with
numeric limits).

4. Regulatory Background
• NDOR is a non-traditional MS4 and is required to manage roadway
runoff pollution within MS4 boundaries.
• NDOR is required (by NDEQ): To capture/treat the first 0.5″ Water
Quality Volume (WQV) that runs off of any new/redeveloped
impervious area.
• Currently treatment levels are only required to be the Maximum
Extent Practicable (MEP).

5. Project Objectives
• Determine water quality of runoff.
• Evaluate performance of the existing BMPs.
• Improve design guidelines of treatment BMPs.

6. Field Study
• Location and six sub-basins
• Methods:
– Flow Measurement
– Sampling Sites
– Sample Analysis
• Results

7. Location
• Intersection between I-80 and I-680
in Omaha, Nebraska

8. Sub-basins and Sampling
Ports

9. Sub-basin 1: Construction
Debris Lot

10. Sub-basin 2: Ditch

11. Sub-basin 3: West Pipe
Tributary Area

12. Sub-basin 4: Grass Strip along
I-80

13. Sub-basin 5: East Pipe
Tributary Area

14. Sub-basin 6: Detention Basin

15. Flow Measurement
• Construction debris lot: Rectangular weir
• Ditch: V-notch weir
• West, east and basin outlet pipes: AV (area
velocity) flow modules and sensors

16. Sampling Sites A and B
Site A: Construction debris lot inlet Site B: Ditch toward 108th Street

17. Sampling Sites C and D
Site C: Northwest outlet
Site D: Northeast outlet

18. Sampling Site E
Site E: Detention basin outlet

19. Sampling Protocol
• Storm identification: The Weather channel website
• NOAA website
• AccuWeather website
• Weather Underground website
• Grab (first flush) and composite (event mean)
samples

20. Hydrologic Model
• HEC-HMS 3.4
• Eight sub-basins
• Hydrographs for each sampling point
• Flows used in the compositing process

21. Chemical/Biological Analysis
• Heavy metals
• Petroleum hydrocarbons
• BTEX
• PAHs
• Road salts
• Total suspended solids
• Total dissolved solids
• BOD and COD.

22. Results
Arithmetic Mean and Median for First Flush and Event Mean
Concentrations for Site A for All Sampled Events

23. Comparison with Similar Studies

24. Results
• Metals (Cu, Cd, and Zn), COD, TSS, & TDS are the major contaminants found in
the highway runoff.
• SVOCs and VOCs were below the detection limits.
• A weak correlation between concentrations, TSS, antecedent dry period (ADP),
total rainfall, and volume of runoff.
• Roadside vegetation (site B) is very efficient to reduce runoff/pollution via
infiltration.
• The existing BMP (detention pond) seems to be somewhat effective in reducing
heavy metals, chloride, COD and TSS loads.

25. BMP Design Manual
• Introduction to BMPs
• NDOR Chapter 3
• Design Guide

26. Introduction to BMPs
BMPs defined as:
– schedules of activities
– prohibitions of practices
– maintenance procedures
– structural and/or managerial practices that, when used
singly or in combination, prevent or reduce the release of
pollutants to waters of the US.
Six minimum BMPs (control measures) identified by CWA:
– Public participation and involvement
– Public education and outreach
– Illicit discharge
– Construction site storm water runoff control
– Post-construction storm water runoff control
– Municipal operations pollution prevention and good
housekeeping

27. NE Stormwater Management
Program

28. Chapter 3: Post Construction
Stormwater Control
• Treatment BMPs include:
– Permanent structural BMPs, such as:
• Settling of particulate matter
• Filtration
• Biological uptake
• Soil adsorption
• Non-structural BMPs for source control such as policies/ordinances
that:
– Provide requirements and standards
– Protect sensitive areas (wetlands and riparian areas)
– Maintain/increase open space
– Provide buffers along sensitive water bodies
– Minimize impervious surfaces
– Minimize disturbance of soils and vegetation

29. Remediation Techniques
• Primary BMPs
– Vegetated Filter Strips
– Vegetated Swales
– Bioretention
– Sand Filter
– Horizontal Filter

30. Guidance Manual Format
• Fact Sheets
– Pollutant removal potential
– Construction and maintenance costs
– Siting constraints
– Maintenance operation
• Design Guides
– Design criteria
– Design process
– Example

31. Vegetated Filter Strip Design Criteria
• WQV flow depth < 1 inch
• WQV velocity below < 1 ft/s
• Slopes in flow direction from 2–15%
• Minimum 15 foot flow path
• 80% Vegetated Cover

32. Bioretention Design Criteria
• Media: compositions depending on needs
• Can be designed as infiltration
• Flexible layout

33. Horizontal Filter Design
Criteria
• Media filled trench in ditch bottom
• Temporarily store WQV in media
• Cobble armoring (1ft above flow depth)

34. Project Overview
• Three-year project (July 2008–March 2011)
• Six events sampled each year.
– Two samples in spring, summer, and fall
seasons
– Total:
• 12 storms for sampling sites A, C, D, and E
• 10 for site B
• Data analysis
• Development of design manual

35. Summary
• Metals (Cu, Cd, and Zn), COD, TSS, & TDS were the
major contaminants found in the highway runoff.
• SVOCs and VOCs were below the detection limits.
• There was a weak correlation between
concentrations, TSS, antecedent dry period (ADP), total
rainfall, and volume of runoff.
• Roadside vegetation (site B) was very efficient in
reducing runoff/pollution via infiltration.
• The existing BMP (detention pond) seems to be
somewhat effective in reducing heavy
metals, chloride, COD, and TSS loads.
• Effectiveness of different BMPs needs to be evaluated.
• BMP design is case sensitive, but development of
general design procedures is possible.

36. Summary
• NDOR defines priority stormwater outfalls as:
Concentrated stormwater flow locations directly
discharging from state ROW to the following:
• Streams (Perennial and
Intermittent)/Lakes/Wetlands/MS4s
• Ephemeral drainage that directly discharges to one
of the above within 500 feet beyond the ROW line

37. Chapter 3: Post construction
Stormwater Control
• Responsibility: Treatment of first ½” of runoff (first flush).
– Runon
– New Development
• BMPs selection criteria (NDOR):
– Primary treatment: 80% removal TSS
– Metals are secondary treatment concern
– Low maintenance
– Cost Effective
– No open water
– Implement BMP within existing right of way as much as
possible
– Infiltration should not be a primary removal mechanism
near roadway
– Aesthetics

38. Summary of Sub-basins

39. Results
Arithmetic Mean and Median for First Flush and Event
Mean Concentrations for Site C for all Sampled Events

40. Results
Arithmetic Mean and Median for First Flush and Event
Mean Concentrations for Site E for all Sampled Events

41. Results
Arithmetic Mean and Median for First Flush and Event
Mean Concentrations for Site C for all Sampled Events

42. Results
Arithmetic Mean and Median for First Flush and Event
Mean Concentrations for Site D for all Sampled Events

43. Results
Arithmetic Mean and Median for First Flush and Event
Mean Concentrations for Site E for all Sampled Events

44. Load Calculation
• L= C • V
– L = Event Pollutant Load (Kg/event)
– C = Event Mean Concentration (Kg/m3 )
– V = Volume of Runoff (m3 /event)

45. Pollutant Loads for Site A

46. Pollutant Loads for Site C

47. Pollutant Loads for Site D

48. Pollutant Loads for Site E

49. Cr Concentration versus TSS Concentration
for the West Pipe Outlet

50. Cr Concentration versus TSS Concentration
for the East Pipe Outlet

51. Cr Concentration versus TSS Concentration
for the Basin Outlet Pipe

52. Conclusions of Field Study
• Roadside vegetation showed strong potential to
reduce runoff via infiltration.
• Metals (Cu, Cd, and Zn), COD, TSS, and TDS are
the primary contaminants found in the highway
runoff.
• SVOCs and VOCs were below the detection limits.
• A weak correlation between
concentrations, TSS, antecedent dry period
(ADP), total rainfall, and volume of runoff.
• The existing BMP seems to be somewhat effective
in reducing the heavy metals, chloride, COD, and
TSS loads. Effectiveness is limited to low intensity
rainfall events.

53. Vegetated Swale Design
Criteria
• WQV flow depth < 4 inches
• WQV velocity <1 ft/s
• Flow through BMP
• Check dams

54. Sand Filter Design Criteria
• Sediment basin protects filter
• Filter media should be low in fines
• Sediment basin drainage < 24 hours
• Filter bed drainage < 40 hours

55. CREDITS
John Stansbury, Ph.D., P.E.
Massoum Moussavi, Ph.D., P.E.,
and Tian Zhang, Ph.D., P.E.
Slide design © 2009, Mid-America Transportation Center. All rights reserved.