Environment, Coasts, Oceans, & Infrastructure

We're starting to see plans calling for AstroTurf rooftop dog parks and are running into a bit of a conundrum when it comes to treating this runoff.  This particular example is going on the 6^th floor of a new development building and runoff is designed to be directed into roof drains (as per the norm for buildings). We are skeptical about this going into the sanitary system because it would contain large amounts of rain water, the pipe is only a 12-inch and we don't want to overwhelm the system.  We don't really want that running into the storm system untreated either.  Technically, ground level dog parks aren't treated either (but they do get some overland flow/natural ground cover treatment). 

Has anyone run into this kind of issue before or have any ideas of where we can look for a solution?

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Sara DeGroot ENV SP, P.E., M.ASCE
CIVIL ENGINEER III
Alexandria VA
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Sara,

This is a unique problem, but one that we've run into before.  You're right that many dog parks on ground level have area drains that go directly to storm.  Whether you're allowed to go to storm versus sanitary is likely going to be dependent on the location of the project.  If a city has a combined storm/sanitary system, they may not care too much either way.  Regardless, I would recommend looking at a natural systems approach.  This could be ground cover treatment/swales like you mentioned, coupled with a stormwater wetland. This would help address both the water quality and quantity by reducing the peak flow and removing nutrients.  Of course, this would require a bit of dedicated area which may or may not be available for your project.  Best of luck.


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Justin Lyon P.E., LEED AP, M.ASCE
Biohabitats
Philadelphia PA
(973)262-1819
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Justin, 

Have you done a natural systems approach on a rooftop?  Like a different type of green roof coupled with the dog park?

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Sara DeGroot ENV SP, P.E., M.ASCE
CIVIL ENGINEER III
Alexandria VA
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Original Message:
Sent: 07-31-2018 11:47
From: Justin Lyon
Subject: Rooftop Dog Park Runoff

Sara,

This is a unique problem, but one that we've run into before.  You're right that many dog parks on ground level have area drains that go directly to storm.  Whether you're allowed to go to storm versus sanitary is likely going to be dependent on the location of the project.  If a city has a combined storm/sanitary system, they may not care too much either way.  Regardless, I would recommend looking at a natural systems approach.  This could be ground cover treatment/swales like you mentioned, coupled with a stormwater wetland. This would help address both the water quality and quantity by reducing the peak flow and removing nutrients.  Of course, this would require a bit of dedicated area which may or may not be available for your project.  Best of luck.


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Justin Lyon P.E., LEED AP, M.ASCE
Biohabitats
Philadelphia PA
(973)262-1819
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Haven't run into this situation but it sounds like the perfect fit for a stormwater detention tank at ground level perhaps with a septic tank on the outlet end or built in to the detention tank. The septic part could be connected to the Sanitary Sewer system.

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James Anderson, MASCE
Principal
Anderson Consulting
North Richland Hills, TX
817-946-9943
James
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James,

Interesting idea.  We don't normally allow septic tanks in the city (we're a very urban city with sanitary sewer system available throughout the city for all development to connect to) so this isn't something we had thought of.  We'll have to look into this some more.


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Sara DeGroot ENV SP, P.E., M.ASCE
CIVIL ENGINEER III
Alexandria VA
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Original Message:
Sent: 07-31-2018 12:30
From: James Anderson
Subject: Rooftop Dog Park Runoff

Haven't run into this situation but it sounds like the perfect fit for a stormwater detention tank at ground level perhaps with a septic tank on the outlet end or built in to the detention tank. The septic part could be connected to the Sanitary Sewer system.

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James Anderson, MASCE
Principal
Anderson Consulting
North Richland Hills, TX
817-946-9943
James
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Similar to the prior idea, you could have a roof drain that goes to a ground-level biofiltration chamber, like a tree box filter or other similar device.  After some amount of ground-level treatment it can discharge to the storm drain.  Also, on the roof, suggest some additional physical barriers close to the drain blocking larger material from dropping into it.

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Saul Nuccitelli P.E., M.ASCE
Chief Hydraulics Engineer
Texas Department of Transportation
Austin TX
(512)416-2219
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While I'm unsure of your local regulations, some jurisdictions view stormwater differently depending on source. For example, in Washington State, runoff from vehicle space and chemically-treated landscaping is viewed as pollution-generating, which requires water quality treatment in addition to flow control; whereas runoff from other hard surfaces (e.g., rooftops) is considered non-pollution generating and requires only flow control.  

Given the rooftop use as a dog park, that space would fall into the pollution-generating category, requiring water quality treatment.  Perhaps you could do something like a "modular wetland", sand filter, or similar.  And of course, source control in the form of signage, public outreach to tenants, and bag dispensers and trash receptacles couldn't hurt.

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Eric Pilcher P.E., M.ASCE
Bonney Lake, WA
eric.pilcher@...
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