1. Public Meeting February 19, 2009
Total Maximum Daily Load Development for Mill Creek, Northampton County, VA
Public Meeting
February 19, 2009

2. Why We Are Here Learn about the water quality of Mill Creek
Discuss the Total Maximum Daily Load (TMDL) development
Gather comments and encourage public participation

3. The TMDL Process
DEQ routinely monitors the quality of waters across the state and publishes a list of impaired waters every 2 years
Virginia is required by law to establish a TMDL for each pollutant causing an impairment
A TMDL is the amount of a particular pollutant that a stream can receive and still meet Water Quality Standards
Recreation
Aquatic life
Fishing
Shellfishing
Drinking water
Wildlife
Designated Uses
Water Quality Standards
Water Quality Criteria

4. Dissolved Oxygen (DO) TMDL for Mill Creek
Designated Use: Aquatic Life
Intended to protect the “propagation and growth of a balanced, indigenous population of aquatic life, including game fish, which might reasonably be expected to inhabit them.”

5. DO Observations in Mill Creek
(7-MCR002.00)
Water Type
Criteria
Listing Year
Class III
Nontidal
Minimum: 4 mg/l;
Daily Average: 5 mg/l
1998

6. Land Use Distribution: Dominated by Agriculture (63.4%) and Forest (27.9%)

7. Water Quality Data Analysis

8. Water Quality Data Analysis

9. Monthly DO Distribution

10. Values EPA Recommended
Causes of the Problem
Duration
Count
Mean
Standard
Deviation
1Background Value
For Natural Condition
Values EPA Recommended DO
(mg/L) 34
4.98
2.16 TN 37
5.87
3.01
<1.0
0.71
NH4+ 38
0.06
0.07
NO23-
5.26
3.15
<0.6 TP
0.10
0.18
<0.1
0.03
BOD5 30
1.70
0.64
Chl a
(ug/L) 7
5.42
7.50 pH
6.22
0.41
<6
1 Water Quality Assessment Guidance Manual, VA-DEQ, 2008,

11. Causes of the Problem Low flow Low re-aeration High temperature
Inflow of nitrogen and organic carbon
High organic carbon deposition and sediment oxygen demand
Decay of vegetative material (35% pH <6)
Human impact is the dominant causes of the problem

12. TMDL Development Source assessment
Linked watershed and in-stream modeling approach
Simulate daily nutrients and carbon loadings from watershed
Discharge loads to in-stream model
Use in-stream water quality model to simulate DO dynamics
Calibrate water quality model
Compute allowable loads and determine load reductions

13. Source Assessment Sources Approach Agricultural Human Pets Livestock
Wildlife
Approach
GIS land use data (land use, population, pets, septic systems)
Wildlife survey data (animal density, animal habitat)
Observations

14. Source Assessment Results
Sub-watershed 1 2 3 4
Human 58 26 27
Dog 14 6 7
Livestock
Cattle
<1
Swine
Horse
Sheep
Chicken*
Wildlife
Duck 36 16 17
Geese 12 13
Deer 8
Raccoon
* The current data are not available. The numbers do not include new chicken farms added in the watershed in past 2 years.

15. Source Assessment Ground water input Atmospheric deposition
Eastern Shore provide a range of values for total Nitrogen of mg/L and total Phosphorus of mg/L (Reay, 1996)
Atmospheric deposition
Based on local information the estimated amount of N-fertilizer applied to the cropland can be up to ~125 lb/acre/year.

16. Modeling Approach Conduct source analysis
Analysis nutrients and carbon inputs from different sources
Use LSPC to simulate watershed processes
Use a spatially varying water quality model (EFDC) to simulate in-stream DO processes

17. Watershed Model
The Loading Simulation Program C++ (LSPC) model was used for simulating flow and nutrients loads
The nutrients (TN, TP, TC) were initially specified using acreage loading estimated from data and literature values. These values were adjusted during model simulations
The daily precipitation values between were used
The flow was calibrated using reference watershed based on USGS Gage

18. Land-Water Connection
X 100 acres
X 900 acres
X 300 acres

19. 1993-1994 Flow Calibration Results

20. 1985 - 1994 10-year Water Budget for the Reference Flow Station

21. Water Quality Model
Environmental Fluid Dynamic Code (EFDC) numerical model was used for the model simulations
The model is a general 3D model capable of simulating flow, nutrients, and DO in estuaries and rivers
The model was driven by daily flow and nutrient loading from the watershed

22. Eutrophication Processes

23. State variables selected for the simulation
Algae (green)
Nitrogen
Particulate organic N
Dissolved organic N
NH4
NO3
Phosphorus
Particulate organic P
Dissolved organic P
PO4
Carbon
Particulate organic C
Dissolved organic C
Dissolved oxygen
Chemical oxygen demand

24. Model Results

25. TMDL Endpoints
Mill Creek is influenced by both human impact and natural condition and
The water quality criteria of a minimum of 4.0 mg/L and a daily average of 5.0 mg/L DO were set as the endpoint
Use in-stream nutrient criteria to set the target of nutrient reduction: EPA recommended level of TN= 0.7 mg/L and TP =0.03 mg/L
Select DO criteria as the endpoint

26. Preliminary Results of Current Load and Estimated Load Reduction
Pollutant
Current Load
(lb/day)
Allowable Load
Reduction
(%)
TOC
76.34
30.53
60% TN
25.18
10.07 TP
0.77 0%

27. TMDL Nutrient TMDL = LA + WLA FA MOS TOC 30.53 29.00 N/A 1.53 TN 10.07
9.57
0.50
TMDL = Total Maximum Daily Load;
LA= Load Allocation (Nonpoint Source);
WLA = Waste Load Allocation (Point Source);
FA= Future Allocation;
MOS= Margin of Safety (5%)

28. DO Distribution After 60% Load Reduction of TN and TOC

29. Questions?