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

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

Fecal Coliform Bacteria Densities in Fairfax County Average of Annual Geometric Mean, 1998 - 2000

GW Parkway Bridge near National Airport Columbia Pike Bridge

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

Arlington County MS4 Data

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

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.

Timeline for Meeting CWA Goal 1998-2000: DNA bacteria source investigation 1999-2001: Optical brightener monitoring 2001-2002: 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

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

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

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

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

Isolates by “Probable” Species N = 302

Isolates by “Probable” Species Baseflow Sampling N = 302

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

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)

BASINS Modeling Approach

Land Use: A Key Model Input

Land Use: A Key Model Input

Precipitation Stations: A Key Model Input

GenScn Facilitates Model Post-Processing

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

Hydrology Calibration Plot

Hydrology Calibration Plot: Flow-Duration Analysis

Summary Statistics for Hydrology Calibration 21376.9 Total Simulated Runoff, Avg. Daily Flow in cfs, 1/1/1999 - 5/31/2001 21186.6 Total Observed Runoff, Avg. Daily Flow in cfs, 1/1/1999 - 5/31/2001 58.910 Total Simulated Runoff, inches, 1/1/1999 - 5/31/2001 58.386 Total Observed Runoff, inches, 1/1/1999 - 5/31/2001 0.90% Error in Total Volume 38.367 Total of Highest 10% of Simulated Flow, inches, 1/1/1999 - 5/31/2001 37.142 Total of Highest 10% of Observed Flow, inches, 1/1/1999 - 5/31/2001 3.30% Error in Total of Highest 10% of Flows 5.375 Total of Lowest 50% of Simulated Flow, inches, 1/1/1999 - 5/31/2001 5.024 Total of Lowest 50% of Observed Flow, inches, 1/1/1999 - 5/31/2001 6.98% Error in Total of Lowest 50% of Flows 16.682 Simulated Summer Flow Volume, inches, 6/21-9/21/1999 + 6/21-9/21/2000 16.578 Observed Summer Flow Volume, inches, 6/21-9/21/1999 + 6/21-9/21/2000 0.62% Summer Flow Volume Error 15.560 Simulated Winter Flow Volume, inches, 1/1-3/19/1999 + 12/22/1999-3/19/2000 + 12/22/2000-3/19/2001 15.120 Observed Winter Flow Volume, inches, 1/1-3/19/1999 + 12/22/1999-3/19/2000 + 12/22/2000-3/19/2001 2.91% Winter Flow Volume Error 138.5 Observed Avg. Daily Peak Flow 142.3 Simulated Avg. Daily Peak Flow

Observed Bacteria Data at Columbia Pike for Model Calibration

Mean Fecal Coliform Counts for Nontidal Four Mile Run by Season

Bacteria Calibration Plot

Bacteria Calibration Plot

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%

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

The End