ROCKVILLE – Urban runoff is a major problem that affects water quality across Montgomery and Prince George’s County.
Impervious surfaces cause sediment, bacteria, and pesticides to wash into the natural and urban water systems.
What constitutes urban runoff ranges from natural ambient soils to concrete, rubber crumbs, and metal chips; all of which come from a variety of urban and man-made sources.
The impact varies greatly and depending on the quantity, the effects can be ecologically destructive and affect regional water quality.
By far one of the most common substances in runoff are soils and dust, which are abundant in urban and suburban areas.
It is usually carried by the wind and tends to land on roads, highways, and rooftops.
Once on these surfaces, it is typically washed off by rain and travels into the natural and urban water systems. When it contacts water, it tends to create turbidity creating a gray or brown color.
“With a large amount of runoff, this can happen within minutes,” says Allen Davis, a civil engineering professor at the University of Maryland.
Davis said sediment could cause a strain on the treatment and urban water system, but that treatment plants are “designed to handle the load.”
According to Stephen MacAvoy, a professor of Environmental Science at American University, said one of the most basic impacts can cause a deprivation of light which in turn decreases the amount of oxygen in the water thus cutting off supply and eventually killing aquatic life forms.
Jay Apperson, a spokesman for the Maryland Department of Environment, sent documents outlining the state’s permitting program which regulates discharges into the water system.
It reveals that both Montgomery and Prince George’s counties experience runoff issues typical of major metropolitan areas.
Of the specific issues, Apperson pointed out at the time, the program was initiated in the early 1990s, both counties suffered and continue to experience extensive metal, sediment, and oil runoff across the region.
Both the environmental departments from Montgomery and Prince George’s counties have taken active steps to also limit additional erosion in the natural water system encouraging residents to invest in rain gardens and other natural filtration measures.
“Since the precipitation enters the streams (and) channels very quickly, there is a lot of energy delivered to the streams in a short amount of time. This scours the banks, digging out sediments and causes flooding” MacAvoy said.
Sediment can also carry nutrients which, if reach a level of overabundance can cause imbalances in the ecosystem causing an overpopulation of algae.
Two of the main substances are phosphorous and nitrogen.
MacAvoy, who specializes in geochemistry, pointed out excessive algae growth deprives other organisms of oxygen.
“Once the algae die, they suck the oxygen out of the water which eventually kills the invertebrates and knocks out the food supply for fish,” MacAvoy said.
Human and animal feces introduce bacteria into the environment and when an ecosystem fails to properly cleanse the water, an overpopulation of bacteria can cause pollution effects which threaten the water supply.
An overabundance of dying aqua life, according to MacAvoy, invites more bacteria and other imbalances on the local ecosystem eventually creating additional effects in the water quality.
“We don’t really have a good handle on bacteria and where it comes from,” said Davis. “There (are) a lot of theories out there but I haven’t seen too much research.”
By contrast, metal concentrations have led to a large amount of research.
“There is a large suite of metals which end up in runoff,” said Davis.
The three main substances include lead, zinc and copper.
Lead has gained the most attention with the contamination issues in Flint, Mich.
Its effects are damaging to both human and water-borne animal health.
In humans, lead is well documented to damage the liver, nervous, and digestive systems as well as eventual death. Aquatic life tends to be poisoned and killed in large amounts.
Zinc, by contrast, has little health effects on humans, however, it tends to kill aquatic life at higher proportions than lead.
Copper, a common roofing material, also contains lead and creates significant runoff that has shown to have a similar impact on aquatic life.
Research shows that sources of the metal runoff tend to be vehicles, roofs, buildings, and outdoor metal storage. Much of this tends to wash down roads, highways, parking lots, and driveways which eventually enter the natural water system.
One of the more obscure substances in runoff is pesticides.
Although pesticides, as well as insecticides, are regulated by state, county, and municipal governments; and their poisonous effects are well known to humans and animals, Davis notes there is a lack of research on how they move through and are removed from the water system by treatment plants.
MacAvoy notes that pesticides and insecticides, when traveling through the natural water system, tend to kill aquatic life forms.
When looking at solutions, runoff tends to be a multistate issue.
Given the geography of Montgomery and Prince George’s counties, runoff tends to travel across county lines often requiring state level involvement.
Since the Chesapeake Bay is the destination for much of the runoff, pollution mitigation may also require federal involvement.
Davis noted that in many aspects of runoff pollution, “regulations aren’t being enforced” but Maryland is “a pretty progressive state” when it comes to the more immediate and apparent environmental effects.
MacAvoy added the District of Columbia has taken “active steps to curb the settlement of runoff with urban gardens.”
The Clean Water Act of 1972 requires federal, state, and local governments to regulate and curb water pollution which also includes runoff.
Under the Clean Water Act, Maryland’s Department of Environment is empowered to set state level water quality standards which are in turn enforced by the county governments.
Guidelines published by the Prince George’s and Montgomery County outline extensive programs to provide financial credits for rain garden’s, tree planters, and other landscaping features to prevent runoff from entering the urban water system.
Davis said solving and mitigating runoff is “a big job to ask of the counties.
“The costs are in the millions and billions,” said Davis. “I think the important part is to invest in the research side so we can understand this issue.”
To view “Water Supply Challenges,” Part 1 of 5, “Get the Lead Out,” click here: https://www.thesentinel.com/mont/newsx/local/item/4143-get-the-lead-out
To view “Water Supply Challenges,” Part 2 of 5, “It’s Not Sexy,” click here: https://www.thesentinel.com/mont/newsx/local/item/4186-it-s-not-sexy
To view “Water Supply Challenges,” Part 3 of 5, “Something We Battle,” click here: https://www.thesentinel.com/mont/newsx/local/item/4225-something-we-battle