Stormwater Containment

What is stormwater containment?

Stormwater runoff is rain or snowmelt that accumulates and flows over the landscape. This water is reabsorbed into the earth and enters our rivers, oceans, and groundwater. Because of human changes to the environment like roads and sidewalks, this runoff cannot always be reabsorbed. This has led to some dangerous consequences. 

Stormwater runoff becomes contaminated when it’s not properly managed. After it’s contaminated, it can enter our waterways. It can also cause issues like flooding, waterway sedimentation, habitat loss, sewer overflow, stream-flow changes, and erosion.

In order to manage these issues, the EPA created the Clean Water Act in 1987, which requires stormwater management by state and federal regulations. The purpose of stormwater management is to make sure that different facilities are doing their part to protect the environment and prevent nonpoint source pollution.

The EPA recommends certain stormwater containment and management solutions that are compliant and protect the environment.

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TrapBags used for a retention pond

What is a stormwater detention basin?

A stormwater detention basin is an area that has been excavated so that during storms, excess water can be held. This helps prevent runoff from flooding in and out of rivers and streams and overflowing the sewer systems. 

Detention basins are not always full. They dry out between storms because they have an orifice at the bottom through which the water can flow. Detention basins are created using a slight slope.  These ponds can hold a large amount of water, which then slowly drains through the bottom of the structure. The advantages of detention basins include the cost. Detention basins are less expensive to implement.

The disadvantages of detention basins include their large space requirement. They also are unable to improve water quality. Unfortunately, detention basins often become breeding grounds for mosquitos and detract from property values.

How does stormwater get polluted?

Stormwater becomes polluted because it flows throughout cities and landscapes collecting pollutants, which it then carries into other waterways. When stormwater runoff can’t absorb into the ground because impervious surfaces like sidewalks and roads block absorption, it must continue to flow.

Areas with higher populations require more rigorous stormwater management because pollution is higher. Urban areas have more people, garbage, cars, pavement, flooding, and infrastructure which all lead to higher levels of pollution in stormwater.

What is the difference between a retention and detention pond?

The basic difference between retention and detention ponds are that retention ponds remain full/wet, whereas detention ponds dry out between storms.

How does a detention pond work?

Retention ponds work to control stormwater by retaining and treating contaminated stormwater runoff. Retention ponds naturally improve water quality and remove pollutants. They are surrounded by natural vegetation which helps prevent erosion. 

Retention ponds are fed by underground pipes, which allows high quantities of water to fill the pond. A small outlet allows some water to flow out so that the pond does not overflow.

Retention ponds have pros and cons like detention ponds. They are able to retain and improve water quality, are easy to create, and help form new habitats. They can also be used for recreational activities.

The disadvantages of retention ponds include a large land requirement. They can also negatively impact water quality if they are designed poorly.

Both detention ponds and retention ponds require maintenance to prevent flooding.

Are detention ponds hazardous?

Detention ponds can pose many safety hazards. These include drowning, exposure to contaminants, and a higher amount of mosquitos which can cause increased disease.

In order to prevent these hazards from causing a negative impact, detention ponds must be well maintained and built properly.

What is a detention easement?

A detention or drainage easement allows others to access and or use your property. Specifically, they allow part of your land to be set aside for drainage purposes to protect your home and surrounding areas from water damage.

Utility and governments can access the area to maintain drainage. You cannot use this area for structures or build impervious surfaces (like driveways) on it. You must also maintain the slope and keep the area maintained.

What is extended detention?

An extended detention basin is a detention basin built to hold stormwater runoff for up to 48 hours. Extended detention ponds are designed to promote pollutant settlement. 

“Extended detention basins are used to address both the stormwater runoff quantity and quality impacts of land development. The lower stages of an extended detention basin can detain runoff from the stormwater quality design storm for extended periods of time, thereby promoting pollutant removal through sedimentation. Higher stages in the basin can also attenuate the peak rates of runoff from larger storms for flood and erosion control. Extended detention basins are designed for complete evacuation of runoff and normally remain dry between storm events.” (njstormwater.org)

How does TrapBag® work for stormwater detention?

TrapBags® can form a containment pool or large pond in a short time. “Rapidly Deployable”

You are able to install pipes through TrapBags which make them very useful for flow control on stormwater detention projects.

A reservoir made from single or stacked TrapBag® barriers can be installed quickly for emergency, semi-permanent, or permanent needs. These reservoirs are suitable for water storage for agricultural use or to create temporarily water reservoirs for fire fighting in bush fire sensitive areas.

The TrapBag® containment systems have become the protection and prevention barrier of choice for governments, businesses, the U.S. Army Corps of Engineers and others who need a cost-effective, proven system that is rapidly deployable to protect their location against flooding.

 

Resources:

https://www3.epa.gov/npdes/pubs/industrial_swppp_guide.pdf

https://info.wesslerengineering.com/blog/stormwater-basins-detention-retention-ponds

https://www.cleanwateraction.org/features/stormwater-pollution

https://www.delawareriverkeeper.org/sites/default/files/resources/PressReleases/Safety%20Detention%20Basins%20Annotated%20Biblio.pdf

http://www.ucdenver.edu/faculty-staff/jguo/Documents/papers/(SP6)SAFETY%20OF%20DETENTION%20AND%20RETENTION%20PONDS.pdf

https://www.njstormwater.org/pdf/tech_manl_6_4_extended_detention_basins.pdf

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