Community- Ornamental Pond, mitigating storm spillage/overflow 4

[injunear457]

Hi guys...Firstly I am an EE so my knowledge of this kind of thing is limited.
I'll preface my question with this description of what we currently have in our community to manage storm overflow of a relatively large (approx 300'x150' by 8'?depth) ornamental fish pond.

When (severe) inclement weather occurs it appears, and I assume, that the pond's rising level is mitigated by a riser/overflow pipe connected to storm drain piping and subsequently to a smaller detention pond nearby.

The problem is that the smaller detention pond's also used for storm water (watershed) of the 'typical' surfaces, blacktop and green space and *I* believe that it is sized for the ordinary runoff rate. It always performs flawlessly until the ornamental pond overflows and then the detention pond is overwhelmed and floods private property at lower elevations by sourcing water(and fish) via the storm drain grates at street level, all of which are also connected to the aforementioned detention pond.
It appears to me, and again I'm an EE so I don't know much about this stuff, that this is 'flooding by design'. It appears to intentionally divert the larger pond overflow to lower elevations as a ‘circuit breaker’ without regard to flow rate.

My question(s) is this:

1) Is this the 'typical' hookup to mitigate overflow of an ornamental pond?

2) Am I correct in my assertion that all the methodologies used to size, volumetrically, the detention basin are 'thrown out the window' when making this extraneous riser/storm drain connection to the larger pond?

3) Any other ways that this might be implemented (I think pumps and controls) would be better to divert the overflow to a different detention pond a short distant away under controlled flow rate to share the burden.

I might of course follow up with a couple more questions later...

Oh, and thanks in advance!

 

[TerryScan]

There are many possible issues here. One distinct possibility is that if the one pond is truly "ornamental" and not regulatory in any way, it may have been designed without modeling how it affects anything. The overflow connection could be little more than an afterthought that wasn't sized to any specific criteria.

Before going to mechanical solutions, it would probably be a good idea to have the existing conditions modeled and seeing if non-mechanical changes (different sized pipes or structures) could be made in the system related to both ponds(this is typically much cheaper to construct and especially to maintain).

It would probably be a good idea to get the local agency responsible for stormwater involved to be sure one doesn't cause regulatory problems.

 

[beej67]

The answers to your questions should be documented in a hydrology study performed by the civil engineer who designed your development. They may have accounted for it, and may not have. The downstream pond may be designed to catch your fish pond overflow, and may not have. See if you can get a copy of that hydrology study, and the accompanying grading&drainage plans from the plan set. Your answers should be in there, if you know what you're looking for. If you don't, you could always hire a CE to do a peer review and site investigation. We need the work.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[injunear457]

There are many possible issues here. One distinct possibility is that if the one pond is truly "ornamental" and not regulatory in any way, it may have been designed without modeling how it affects anything. The overflow connection could be little more than an afterthought that wasn't sized to any specific criteria.

The pond is wholly Ornamental. I think you hit the nail on the proverbial head in that this may have been an afterthought. Something like this was mentioned anecdotally by someone else in the community.

The answers to your questions should be documented in a hydrology study performed by the civil engineer who designed your development. They may have accounted for it, and may not have. The downstream pond may be designed to catch your fish pond overflow, and may not have. See if you can get a copy of that hydrology study, and the accompanying grading&drainage plans from the plan set. Your answers should be in there, if you know what you're looking for. If you don't, you could always hire a CE to do a peer review and site investigation. We need the work.

Good information, I'll pursue the report if it exists. It is hard to believe that they could have accounted for the fish pond as the detention pond's capacity is, just by sight, about 1/2 to 1/3 capacity of others (about 200) elsewhere in the community that handle 'typical' runoff sans any extraneous connections from ornamental fixtures in the landscape.

Umm, hiring a CE? We’re individuals on the receiving end of this flooding. The HOA operates the fixture so we cannot afford to initiate any studies. Our only hope is to force a defiant HOA to improve on this system by obtaining an injunction to shut the pond down until such time they find a way to manage its overflow/spillage.

 

[beej67]

Sounds to me from your abbreviated description like its possible the civil engineer did account for the fish pond, including the potential storage in the fish pond, and used that to reduce the size of the downstream detention pond. The fish pond does have storage after all.

Whether he did that right or not, though, depends on the math. Could have done it right, but there's lots of potential things he could have done wrong. Hard to say. Do keep in mind that pond size is a function of watershed area and land cover. You can't say a pond is undersized without analyzing the watershed.

A peer review of the hydro study with a site investigaton might not be too expensive. (Maybe a grand if you can get all the info together) In lieu of that, sharpen your pencil and learn a new profession. Hydrology isn't any less complicated than electrical engineering. You wouldn't (shouldn't) trust me to identify what's wrong with a circuit. Reverse applies as well. In my experience, it typically costs about half as much to engineer a solution than it does to hire a lawyer.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[injunear457]

including the potential storage in the fish pond, and used that to reduce the size of the downstream detention pond. The fish pond does have storage after all.
Whether he did that right or not, though, depends on the math. Could have done it right, but there's lots of potential things he could have done wrong.

Yes, I thought of the storage of the fish pond itself and the fact that it rises considerably before finally spilling over.
The fact that it floods on average every 3 to four years, and it does cause property damage to private property, seems to suggest that he didn't get it right in my opinion.

it typically costs about half as much to engineer a solution than it does to hire a lawyer.

Agreed, but you have to have parties that are mutually cooperative to do that. The HOA refuses to discuss at all.

Thanks again.

 

[cvg]

my first thought is that the detention basin is way too small. Flood control detention basins are generally required to be designed for 100-year storm runoff, not "ordinary" flows. If it is overflowing every 3 to 4 years, than it only has capacity for a very much smaller storm. (or you are having 100-year storms every 3 -4 years)

Regardless if the ornamental pond is part of the flood control system or not, the entire system should be designed to function adequately for a design storm which is much greater than 3- or 4-year rainfall.

 

[beej67]

To add to that, no pond should be discharging dead fish downstream. That's probably technically a Clean Water Act violation.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[injunear457]

my first thought is that the detention basin is way too small. Flood control detention basins are generally required to be designed for 100-year storm runoff, not "ordinary" flows. If it is overflowing every 3 to 4 years, than it only has capacity for a very much smaller storm. (or you are having 100-year storms every 3 -4 years)

Regardless if the ornamental pond is part of the flood control system or not, the entire system should be designed to function adequately for a design storm which is much greater than 3- or 4-year rainfall.

Yes, that's what I've intuitively known for awhile....thanks

To add to that, no pond should be discharging dead fish downstream. That's probably technically a Clean Water Act violation.

Well, some probably died but I didn't see any dead fish but all were actually alive, some swimming in pools, at or near my home foundation to the street level where they came from...They seemed to be able to find their way back (probably 1000+ feet) as the water recedes over time, into the larger pond.

 

[gbam]

I would suspect that neighborhood cats or birds got those fish.

 

[beej67]

Holy moly. If this overflow is flooding swimming pools downstream, you definitely need to hire an engineer.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[injunear457]

Holy moly. If this overflow is flooding swimming pools downstream, you definitely need to hire an engineer.

LOL, not quite....I meant that the fish are schooling, in groups, and swimming in about 18~24 inches of water in front of my home and nearly up to the top of the driveway....Hard to explain here but no flooded swimming pools....

 

[LincolnPE]

"Our only hope is to force a defiant HOA to improve on this system by obtaining an injunction to shut the pond down until such time they find a way to manage its overflow/spillage."

Hmmm, this has me wondering if the HOA made the illegal connection to the detention pond. Maybe an overzealous board member or two taking things into their own hands?

Now you don't want to be responsible for any illegal connections, as you mention you are considering connecting to another pond. You are not suppose to transfer drainage problems to another area and could get sued. There is a design in place somewhere more than likely, a storm drainage circuit network design if you will.

I would first go give an earful to your city or county engineer that you are being adversely impacted and see demand they look into it. If they say it's all private and they are out of it, then you will need to protect yourself with effective legal representation if you are truly being adversely impacted.

 

[injunear457]

Well, this just gets worse....
The latest is that the HOA just repaired what they say was a shoreline erosion problem. I'll give them the benefit of the doubt but it seems to me that if it indeed eroded then all the material that comprised the shoreline before is still there within the confines of the pond.

Their contractor just added materials to the pond to produce a higher shoreline boundary, some sort of wrap and lots of stones. They removed no materials from the pond so the pond's effectively smaller in volumetric capacity.....the Community pond's designated, on the County Map (aerial photo), as a DRA in of itself.

But wait, it gets worse yet. I found in the minutes of the "grounds commitee" meeting a comment that states that a SWTMUDD ((Sothwest Water District) technician advised them to run the pond at a higher level to prevent future erosion.
The Community Pond is now in what I call a perpetual flood state as there's several inches of water in the DRA pond at all times now, regardless of rainfall.

So I'm not sure where to go with this from here. I'm going to visit the SWTMUDD to poke around and see if I can't recover the Hydrolgy study/model information but my neighbor and I don't have the wherewithal to hire a CE whereby the HOA has unfettered legal expenses and money (our HOA dues/money)....

Any advice? Perhaps I can post some photos (Aerial) and whatever else I can get my hands on so that I can (hopefully) not look too stupid when/if I need to take this in front of a judge to obtain an injunction.....

Thanks again.

 

[LincolnPE]

The "hydrology study" for your subdivision is called the Drainage Report. It was prepared by the civil engineer who completed the construction plans for the roads, utilites and grading.

Go down to the County Engineer if you're in the County, or the City Engineer if you're in the City, and ask for a copy. Also, ask for a copy of the final approved civil construction plans for your subdivision.

 

[cvg]

as a HOA board member myself, I can assure you they do not have unfettered budget with respect to legal fees. This is not something most boards reserve a lot of budget for and once the budget is gone, they would have to authorize the spending from the reserve account or voting on a special assessment to pay a lawyer. Not likely to happen. As a board member, I would be very leary about getting into a legal battle, especially if there was a good chance that the HOA may be at fault.

But dont assume they are malicious in not cleaning out the bottom of the pond. Unless they have an O&M plan for the pond or an engineer on the board, they simply hired a landscaper to replace the riprap at minimum cost. They probably are not fully aware of the ramifications.

 

[injunear457]

That would be the South West Florida Water Mangement District office (SWFWMD)...

I'm headed there this afternoon.....

 

[injunear457]

cvg said:
as a HOA board member myself, I can assure you they do not have unfettered budget with respect to legal fees. This is not something most boards reserve a lot of budget for and once the budget is gone, they would have to authorize the spending from the reserve account or voting on a special assessment to pay a lawyer. Not likely to happen. As a board member, I would be very leary about getting into a legal battle, especially if there was a good chance that the HOA may be at fault.

They have already referred the matter to their attorney as a result of our insistence that if they don't act then we would seek an injunction. This argument stems from their insistence that we (my neighbor and I) simply need to suck it up and put up with recurrent flooding (every 3~5 years) from their operation of an ornamental fish pond. We asked them to allocate money to study ways to improve on the performance of the drainage system. That request was made long before this recent modification....(read through the entire thread)

cvg said:
But dont assume they are malicious in not cleaning out the bottom of the pond. Unless they have an O&M plan for the pond or an engineer on the board, they simply hired a landscaper to replace the riprap at minimum cost. They probably are not fully aware of the ramifications.

Well, no they used an engineering firm, Coastal. Not clear to me if they actually did the shovel work or just consulted because the minutes don't specify.

Curiously, they are 28k over on legal expenses in their budget for this year already. They (HOA) have a propensity to make up for their own bad management by leaning heavily on the association's law firm. They are litigating a grass cutting complaint, a geo-thermal pool heater installation gone wrong and a couple other capital projects gone wrong, mostly due to their own misconceptions and ignorance.

 

[msquared48]

Sounds like the ornamental pond needs to flow into a new regulated pond, if there is room, to catch the overflow. The overflow needs to go only to the new pond, with the normasl outflow going to the existing regulated pond. Any discharge from the new regulated pond could be sent into the existing regulated pond at a reduced rate. You might even want to psrtly regulate the ornamental pond, driving it to overflow sooner, depending what happens downstream.

There are many other solutions here... but all require a Civil experienced in Hydrolology. Good luck.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[LincolnPE]

Yes, the Drainage Report and the civil construction plans are created and submitted at the same time for municipal approvals. They work specifically and interactively together. Make sure you get the FINAL approved copies of both. There are a few rounds of submittals and comments for the drainage report and construction plans in the municipal review process before they are approved for Final. There can be various versions floating around by accident, or just poor bookkeeping practices.

Make sure you get the FINAL stamped and approved editions of both.