Source: Study Plan: Straight Creek Use Attainability Analysis
If waters are clean enough for the above uses, presumably the waters are clean enough for industrial and municipal water supplies. If a stream segment, reservoir, or estuary is "impaired," then the state must conduct a Total Maximum Daily Load (TMDL) study to determine which pollutants are excessive and must be reduced in order to meet Federal standards established by the Environmental Protection Agency (EPA), under the Clean Water Act. After being sued, EPA and Virginia agreed to complete TMDL's on 644 impaired stream segments by 2010. Based on the 2006 report to EPA on impaired waters in Virginia, the state needs to complete about 2,000 TMDL's.
There is a way to meet EPA's requirements without cleaning up a stream completely. Virginia can change designate uses for a stream, and that alters the requirements (and costs) for clean-up. After completing a Total Maximum Daily Load (TMDL) clean-up plan and Use Attainability Analysis for surface water bodies that do not meet water quality standards, the State Water Control Board could redefine the intended use and lower the standard (and the costs) to make waters "clean."
Maryland, Virginia, and EPA completed a Use Attainability Analysis and redefined the designated uses for the Chesapeake Bay and its tidal tributaries. The old standard requiring 5 mg/L dissolved oxygen year-round throughout all tide-influenced waters did not fully reflect natural conditions. The government agencies decreased the required water quality in the deepwater channels of the bay, allowing a lower level of dissolved oxygen, and increased standards in other areas of the bay.
An aquatic life Use Attainability Analysis was initiated on Straight Creek (a tributary of Powell River that flows through St. Charles in Lee County) in 2006, because of doubts that the creek could achieve water quality goals under natural, human-caused, and economic conditions. The unregulated sewage discharges and failing septic systems could be addressed to correct for excessive bacteria, but flood control projects since the mid-1960's have straightened the channel, removed the tree canopy. The flood control effort facilitated development that has created an unnatural channel, with many human structures encroaching on the flood plain. It may be unrealistic to correct the sedimentation and Total Dissolved Solids (TDS) problems and restore a balanced, indigenous population of aquatic life in Straight Creek.
Most pollution is triggered by human-caused impacts. When we strip the vegetation and expose raw soil, rain washes sediment into streams. When our cattle deposit manure on farm pastures (and suburban residents mimic that process by applying fertilizer to lawns), excessive nitrogen and phosphorous moves downhill into our waterways. When ocean-going freighters discharge ballast water in the Chesapeake Bay, we introduce non-native (and sometimes invasive) species.
After coal burns to generate electricity, sulfur escaping up the smokestack creates acid rain. Mercury vaporized by coal cimbustion is redeposited across the land and directly into lakes, poisoning every waterbody in Virginia. When we hit the brake pedal, the brake pads and tires deposit heavy metals on roadways. Even when cars sit idle, they ooze grease and other petroleum products that migrate into our lakes and creeks.
In developed areas, wastewater treatment plants minimize but do not eliminate contamination from sewage. The basic problem is population growth, with incremental impacts from every new resident. As more people that move into a watershed, the waters experience greater impacts. As the population continues to increase in Virginia, the environmental impacts will grow and grow even if each resident adopts a "greener than average" lifestyle.
People are not the only polluters. Wildlife (deer, geese, mice, snakes, etc.) excrete wastes, but Mother Nature and Father Time can handle the natural levels of pollution. Exposure to sunlight or oxygen as water runs down natural streams will kill harmful bacteria and viruses.
Fortunately, wildlife is rarely concentrated enough to create sufficient waste that affects water quality - predators ensure the critters stay separated from each other. However, urbanizing counties in Northern Virginia and Tidewater are removing massive amounts of natural habitat, concentrating critters unnaturally in the few remaining forested strips along stream channels. Occasionally, DNA tests of water samples that come back with high levels of fecal coliform show the source of the bacterial contamination was geese, raccoons, or other wildlife that had no other place to live or "to go" besides next to the stream.
 wild rice in Quantico Creek estuary |
 test well for contaminants at Occoquan Bay National Wildlife Refuge |
Some phosphorous, nitrogen, and other chemicals occur naturally in Virginia waters. Those chemicals dissolved into solution as the rainwater percolates through the soil and as the groundwater interacts with the bedrock and soil. In karst environments, water is typically "hard" (high in dissolved calcium ions) due to the natural process of limestone being affected by acidic groundwater, which etches away at the bedrock and occasionally forms caves.
In southeast Virginia, the natural decaying organic matter in the Dismal Swamp may interact with the chlorine used in drinking water purification plants. That interaction can create a high level of trihalomethanes, a chemical that could create serious health effects. Residents of the City of Chesapeake claimed that miscarriages were caused by high levels of trihalomethanes in the drinking water from the Northwest River Water Treatment Plant.
Some chemicals have been introduced into the environment, or concentrated far beyond natural "background" levels. For example, rainwater that washes off a lawn, golf course, or soccer field that has just been fertilized will carry nitrates into the local streams and lakes. If someone dumps old motor oil onto a driveway, after changing the oil in their car, then that pollution will seep into the ground and contaminate the water. Plumes of gasoline and heating oil pollution have been mapped, showing the spread of the chemical from leaking undergroud storage tanks.
When we put fertilizer on our lawn, golf course, or farm fields, we add valuable nutrients to the soil for plants to use in growing. Fertilizers advertised as "10-10-10" are advertising the relative percentages of nitrogen, phosphorous, and potassium. (You might also see N-P-K on the bag, using the chemical symbols of those elements.)
However, too much of a good thing can create a problem. If a rainstorm washes the fertilizer that we just spread on the lawn out into the gutter/ditch, those nutrients have been wasted and will end up growing weeds in a ditch, or flow all the way to a stream and change its chemistry rather than help you grow grass or crops.