stormwater management

More than Tunnel Vision

by Jennie Saxe

Green roof at Ft. Reno reservoir.

Green roof at Ft. Reno reservoir

A few months ago, we blogged about the massive engineering project to construct tunnels beneath the District of Columbia using giant tunnel boring machines. These tunnels are being constructed to hold onto stormwater and reduce combined sewer overflows, which can result in harmful bacteria in the District’s waterways.

“Gray” solutions, like tunnels and treatment plant upgrades, are not the only part of the District’s plans. Last week, EPA officially gave the green light to DC Water’s plans to add a significant amount of green infrastructure to the mix to protect the Potomac and Rock Creek watersheds. Fittingly, this announcement was made atop the green roof at DC Water’s Ft. Reno reservoir. Using green with gray provides stormwater management capacity while creating a healthier urban environment. In addition, the implementation of these green infrastructure projects will result in water quality benefits during the installation process.  This is very different from grey infrastructure where the benefit is only realized at completion of construction.

To follow the progress of the Clean Rivers project, check out DC Water’s Clean Rivers Project website, or follow the tunnel boring machines – Nannie, Lady Bird, and Lucy – on Twitter.

 

About the author: Dr. Jennie Saxe joined EPA’s Mid-Atlantic Region in 2003 and works in the Water Protection Division on sustainability programs.

 

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

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Wetlands: Earth’s Kidneys

By Marguerite Huber

Stream restoration research

Stream restoration research

Our organs are vital to our health, with each one playing a significant part. Kidneys, for instance, filter our blood to remove waste and fluid. Wetlands are often referred to as “Earth’s kidneys” because they provide the same functions, absorbing wastes such as nitrogen and phosphorous. When excess amounts of these substances—nutrient loading—flow into waterways it can mean harmful algal blooms, hypoxia, and summer fish kills.

Recognizing the importance of wetlands, many communities are taking steps to protect, restore, and even create wetlands.

For example, many stream restoration projects include constructing wetlands to absorb stormwater runoff and absorb excess nutrients and other pollutants that flow in from a host of sources across the watershed (known collectively as nonpoint source pollutants).

These constructed wetlands can provide key elements to urban stormwater management because they help reduce the impacts of runoff after a rainstorm or big snowmelt event. Such runoff typically transports high concentrations of nitrogen and phosphorous and suspended solids from road surfaces into waterways.

One such type of wetland that may provide these kinds of benefits is the oxbow lake, so named because of their curved shape. These form naturally when a wide bend in a stream gets cut off from the main channel, but EPA researchers are taking advantage of a couple of oxbow wetlands created during stream restoration activities at Minebank Run, an urban stream in Baltimore County, MD.

The researchers are studying the oxbow wetlands to quantify how effective such artificially created wetlands are at absorbing nitrogen and phosphorous in an urban setting. If these types of wetlands are effective, then deliberately constructing oxbow wetlands could be an important nutrient management strategy in such landscapes.

From May 2008 through June 2009, the researchers analyzed water, nitrate (a form of nitrogen pollution), and phosphate flow during four storms to better understand the impacts of hydrology on the potential for the two oxbow wetlands and the adjacent restored streambed to absorb or release nutrients.

The results suggest that oxbow wetlands in urban watersheds have the potential to be “sinks” that absorb and store nitrogen. They also reinforced information pointing to the dynamic hydrologic connection linking water and nutrient flow between streams and nearby oxbow wetlands, findings that if confirmed through further investigation can be used to improve restoration efforts that improve water quality across entire watersheds.

When it comes to phosphorus, the researchers found that oxbows don’t function as “sinks,” but “sources,” that contribute a net increase of the nutrient. They hypothesize that this is because the nutrient is released from wetland sediments during storms or other similar events. Future studies are needed to investigate the magnitude of phosphorous release, and how important that contribution is across the watershed.

Just like how our kidneys are an essential aspect of the human body, wetlands are an important aspect of nature. Retaining additional nutrients and treating non-point source pollutants help give natural and constructed wetlands the affectionate nickname of “Earth’s Kidneys.”

About the Author: Marguerite Huber is a Student Contractor with EPA’s Science Communications Team.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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EPA Releases Resource to Help Guide Green Infrastructure

By Lahne Mattas-Curry

Rain barrel captures roof runoff in Santa Monica, CA. (Copyright Abby Hall, US EPA)

Rain barrel captures roof runoff in Santa Monica, CA. (Copyright Abby Hall, US EPA)

Imagine you are a municipal sewer system operator in an urban area. You probably would be well aware of the millions of gallons of untreated water that enter your combined sewer systems creating a big old mess in your local water bodies. But what if there was a cost effective solution available? And even better than low-cost, what if the solution made your community pretty and created a great community for people to live, work and play? You would jump on it, right?

Well, many communities with combined sewer overflows have been using green infrastructure – rain barrels, rain gardens, greenways, green roofs etc. – as an attractive way to reduce the stormwater runoff that goes into a sewer system. (We have blogged about it many times before.)  Green infrastructure helps reduce capital costs – traditional grey infrastructure made of pipes and other systems is often cost prohibitive – and has been shown to also reduce operational costs at publicly owned treatment works.

EPA scientists helped develop a resource guide to help more communities manage stormwater and wastewater with green infrastructure. The resource, released Greening CSO Plans: Planning and Modeling Green Infrastructure for Combined Sewer Overflow (CSO) Control (pdf),” will help communities make cost-effective decisions to maximize water quality benefits. The resource explains how to use modeling tools such as EPA’s Stormwater Management Model to optimize different combinations of green and grey infrastructure to reduce both sewer overflow volume and total number of overflow events.  The guide also has relevant case studies to showcase how different communities are using green infrastructure.

Hopefully using this resource can help you plan green infrastructure solutions and provide a variety of tools that can help you measure and reduce stormwater runoff.

For more information about green infrastructure at EPA, please visit: http://water.epa.gov/infrastructure/greeninfrastructure/index.cfm

You can also learn more about green infrastructure research and science here:

http://www2.epa.gov/water-research/green-infrastructure-research

 

About the author: Lahne Mattas-Curry works with EPA’s Safe and Sustainable Water Resources team, drinks a lot of water and  communicates water research to anyone who will listen.

 

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action.

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