1. Fecal Coliform Bacteria TMDL for Four Mile Run
Northern Virginia Regional Commission
Don Waye
March 25, 2002

4. Perception v. Perspective
Four Mile Run Bacteria
Perception v. Perspective
Source: Center for Watershed Protection

5. Fecal Coliform Bacteria Densities in Fairfax County
Average of Annual Geometric Mean,

6. GW Parkway Bridge near National Airport
Columbia Pike Bridge

7. Arlington WWTP discharge easily meets its permit limit of 200 monthly geometric mean.

8. Arlington County MS4 Data

9. Four Mile Run Watershed Characteristics
Size: 20 square miles
Population: 183,000 (2000 Census)
Population density: >9,000/sm
Land Use: 0% agriculture; 100% urban (from medium density residential to high density commercial, highways, roads, stream valley park system, 1 golf course); 35-45% impervious

10. A TMDL is due May 1, 2002
Total Maximum Daily Load (TMDL) Regulations: A TMDL or Total Maximum Daily Load is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards, and an allocation of that amount to the pollutant's sources.
Water quality standards are set by States, Territories, and Tribes. They identify the uses for each waterbody, for example, drinking water supply, contact recreation (swimming), and aquatic life support (fishing), and the scientific criteria to support that use. The Clean Water Act, section 303, establishes the water quality standards and TMDL programs.

11. Timeline for Meeting CWA Goal
: DNA bacteria source investigation
: Optical brightener monitoring
: TMDL development
Next Steps:
Develop draft Implementation Plan
Public review for IP/Final actions/adoptions by EPA, Virginia and local governments
Achieve CWA goals/ attain w.q. standards

12. Timeline for TMDL Development
June 01: Begin contract; 1st public meeting
June-Dec 01: TMDL model dvpt. & calibration
Sept 01-May 02: Storm drain regrowth research
Jan-Feb 02: Determine & model allocation scenarios
March 2002: Draft TMDL presented for public comment, present plans at 2nd public meeting
April 9: end of public review period
May 1: Address comments from EPA and others; Final TMDL due

13. Two Complementary Efforts
1. Optical Brightener Monitoring
involves cotton
and black light
2. DNA Source Tracking
involves animal scat and expensive lab gizmos
Photo by Don Waye

14. Bacteria Source Identification Using DNA Fingerprinting
Dr. George Simmons pioneered this technique with work in Virginia’s Eastern Shore
E. coli-specific testing
PFGE DNA profiling (like barcoding)
Photo by Don Waye

16. Limits of PFGE Technique
Results independently reviewed by 5 local naturalists
Naturalists concurred with most findings, but unanimously raised questions about waterfowl species & location of deer matches
Relatively small DNA source library may be technique’s Achilles Heel
Some E. coli strains may be found in multiple host species or PFGE may not differentiate adequately

17. Isolates by “Probable” Species
N = 302

18. Isolates by “Probable” Species
Baseflow Sampling
N = 302

19. Conclusions
DNA work confirms low microbial biodiversity (large population of E. coli clones)
Limited matches with species absent in watershed fosters general confidence in technique (waterfowl may be problematic, however)
Storm drains and sediments seem to promote higher levels of bacteria
Waterfowl, raccoons, humans and dogs are the main sources

20. Is Regrowth a Possibility?
Doctor’s Run
Occum’s Razor—the simplest answer that fits the data
Highest bacteria counts from storm drain outfalls and sediments
Need more comparative data on bacteria strain variability (e.g., paired watershed study)

21. BASINS Modeling Approach

22. Land Use: A Key Model Input

23. Land Use: A Key Model Input

24. Precipitation Stations: A Key Model Input

25. GenScn Facilitates Model Post-Processing

26. Hydrology Calibration Plot
Calibration period selected based on best available observed data

27. Hydrology Calibration Plot

28. Hydrology Calibration Plot: Flow-Duration Analysis

29. Summary Statistics for Hydrology Calibration
Total Simulated Runoff, Avg. Daily Flow in cfs, 1/1/ /31/2001
Total Observed Runoff, Avg. Daily Flow in cfs, 1/1/ /31/2001
58.910
Total Simulated Runoff, inches, 1/1/ /31/2001
58.386
Total Observed Runoff, inches, 1/1/ /31/2001
0.90%
Error in Total Volume
38.367
Total of Highest 10% of Simulated Flow, inches, 1/1/ /31/2001
37.142
Total of Highest 10% of Observed Flow, inches, 1/1/ /31/2001
3.30%
Error in Total of Highest 10% of Flows
5.375
Total of Lowest 50% of Simulated Flow, inches, 1/1/ /31/2001
5.024
Total of Lowest 50% of Observed Flow, inches, 1/1/ /31/2001
6.98%
Error in Total of Lowest 50% of Flows
16.682
Simulated Summer Flow Volume, inches, 6/21-9/21/ /21-9/21/2000
16.578
Observed Summer Flow Volume, inches, 6/21-9/21/ /21-9/21/2000
0.62%
Summer Flow Volume Error
15.560
Simulated Winter Flow Volume, inches, 1/1-3/19/ /22/1999-3/19/ /22/2000-3/19/2001
15.120
Observed Winter Flow Volume, inches, 1/1-3/19/ /22/1999-3/19/ /22/2000-3/19/2001
2.91%
Winter Flow Volume Error
138.5
Observed Avg. Daily Peak Flow
142.3
Simulated Avg. Daily Peak Flow

30. Observed Bacteria Data at Columbia Pike for Model Calibration

31. Mean Fecal Coliform Counts for Nontidal Four Mile Run by Season

32. Bacteria Calibration Plot

33. Bacteria Calibration Plot

36. Reduction in Loadings from Existing Conditions (%)
% Days
Geometric
Mean > than
190 counts/100ml
Waterfowl
Raccoon
Human
Dog
Other
Wildlife
Existing
Conditions
65%
Scenario 1 95 95
54%
Scenario 2 50 50 95 95
41%
Scenario 3 80 80 98 98 80 8%
Scenario 4 95 95 98 98 95 0%

37. Annual Fecal Coliform Loadings (counts/year) Used for
Developing the Fecal Coliform TMDL for Four Mile Run
Parameter
WLA LA
MOS*
TMDL
Fecal coliform
2.04E+13
9.61E+14
4.91E+13
1.03E+15
* Five percent of the TMDL

39. The End