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

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

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

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.”

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

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

Water Quality Data Analysis

Water Quality Data Analysis

Monthly DO Distribution

Values EPA Recommended Causes of the Problem Duration Count Mean Standard Deviation 1Background Value For Natural Condition Values EPA Recommended DO (mg/L) 1997-2003 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 1997-2001 30 1.70 0.64 Chl a (ug/L) 2001-2003 7 5.42 7.50 pH 6.22 0.41 <6 1 Water Quality Assessment Guidance Manual, VA-DEQ, 2008, http://www.deq.virginia.gov/waterguidance/wqam.html

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

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

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

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.

Source Assessment Ground water input Atmospheric deposition Eastern Shore provide a range of values for total Nitrogen of 2.0 - 7.0 mg/L and total Phosphorus of 0.02 - 0.03 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.

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

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 1998-2003 were used The flow was calibrated using reference watershed based on USGS Gage 01484800

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

1993-1994 Flow Calibration Results

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

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

Eutrophication Processes

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

Model Results

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

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%

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%)

DO Distribution After 60% Load Reduction of TN and TOC

Questions?