Not allowed to connect drain tile to storm sewer system.

[knae0015]

I am working on a project in the City of Minneapolis and they have started to not allow connecting building foundation drain tile or parking lot subdrains to the City storm sewer system. Has anybody else out there come across this in other cities?

They say that if a project needs drain tile, it needs to be pumped to grade before it discharges into the storm sewer system.

 

[MiketheEngineer]

Benn common in St. Louis County for years. St. Louis ity is different and have their sharre of problems. A few builders have been fined (heavily) for doing it.

It overloads the sanitary systems

 

[dhengr]

I’m not trying to second guess you, but I would think they are saying that foundation drain tiles and the like CAN NOT be connected to the sanitary sewer system, for obvious treatment cost reasons. They must run to day light or be pumped to the surface so they flow into the storm sewer system or a surface level drainage way. They may also be saying that they do not want random drain connections into the storm sewer lines, because of the added maintenance costs and difficulties.

 

[MiketheEngineer]

99% of the reason is overload!!

 

[msquared48]

OK:

The OP is not talking sanitary here, he is talking storm - two diffrerent systems. Unless it is a combined system, you do not dump stormwater into a sanitary sewer, period.......................

The reason for pumping the storm water from the foundation drain to the storm drain (there is no objection from the city as to disharging to the storm from what I read here, only HOW you do it) is that if this is a gravity discharge system the water backs up in the storm sewer. It will charge the foundation drains and wall. Not so with a pumped system.

My objection to this is that when the power goes out, the charging will happen anyway. I think a gravity drain system with a backflow prevention valve is the best solution here, but what do I know...

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[MrBachelor]

I have not run into this situation specifically where underdrains were not allowed to be directly connected to the storm sewer system. However, this regulation may have to do with stormwater quality. Perforated drains under the ground surface, while typically wrapped with a geotextile fabric to keep debris out, still have the potential to collect sediment, especially if installed incorrectly. A direct connection to the storm system offers no possibility for sediment filtering or removal. If the drains gravity discharge to the surface, there is possibility for the water to flow over grass to remove sediment or to be treated in the same way the surface water is treated.
Requiring the water to be pumped to the surface seems unnecessary as there are other means to treat the sediment-laden water before it gets into the storm sewer system. If stormwater quality is the reason for restricting the connection, the OP should investigate alternate means of treating the draintile water before connection to the public system. The municipality should be open to this method of reasoning.

Nate the Great

http://www.ceieng.com

 

[jgailla]

Is it possible the city was sued in the past when the city storm sewer surcharged and backed up into someone's basement?
When I think of building "drain tile" and parking lot "subdrains", I think of measures put in place to control groundwater, not stormwater drainage. These would be affected by pump failure, but the flow will be fairly steady and not exhibit a peak flow during storm events.

 

[cvg]

not sure about Minneapolis, but many larger, older cities have combined sewers. The storm and sanitary are combined. therefore overload at the treatment plant may in fact be the main reason. treatment plant expansions are extremely costly and can often by avoided by just removing these types of non-sanitary connections.
jgailla hit on another very likely reason and an additional one is that the city does not want every tom, dick and harry digging up the streets and punching holes in the storm drain. that would be a permitting, traffic, and operation and maintenance nightmare.

 

[knae0015]

Thanks for the replies.

What I originally posted was correct in that the City does not want to allow draintile connections directly to the STORM sewer system. Minneapolis does not have many combined sewers left, and this was not the issue. There apparent issue is that some buildings have been constructed where the draintile is in the groundwater table, so there is a constant flow into the storm pipes, and they don't have any way to bill the property owners for the constant use of the system.

I wanted to find out if any other cities also didn't allow this. Every other city that I have worked with allows the draintile connections to the storm sewer system.

 

[beej67]

What?

If they built the foundation in the groundwater table, then they'll be pumping to surface drainage (and therefore back to storm sewer) just as much as if they tied directly to storm sewer. The only way this thing makes any sense is if its for the reasons msquared mentions above.

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

http://www.campbellcivil.com

 

[cvg]

I have met resistance from cities not allowing any pumped discharge directly to a storm drain. they require an air gap so there can be no accidental pressurization of the gravity storm drain. for instance, underground detention storage which requires a lift station would need to discharge to a private catch basin and then gravity flow out to the storm drain

 

[dhengr]

Buy some pipe and pump that stuff right into the middle of R.T. Rybak’s office. By the time it filters through all the b.s. in City Hall, they will allow it to flow directly into the sanitary sewer system.

 

[ACtrafficengr]

I'm not in Minnesota, but we've adopted a similar policy. We are required to monitor our outfalls for pollutants, and track it back to the source if we find any. I'm not disparaging your clients or their tenants, but someone could put grey water, used motor oil, etc. into the building's sump. It's easier to find the illicit discharge if the connections are are accessible.

 

[concretemasonry]

Since the foundation water from the drain tile is assumed to be similar to moisture in the surrounding soil, some areas try to encourage/force surface distribution to recharge the ground water to recharge the ground water and aquifers, rather than pipe it to the river and let it go downstream. This seems to be common in areas where development has caused more paving and run-off and lowered groundwater levels and drier aquifers (ala Ogallahla(sp?) basin).

If there is excess water, it will run off to the municipal storm sewer system.

In India, it becoming common to separate the gray water and black water in the individual systems in each unit and collect it is separate systems for different levels of treatment. Very often the gray water is used for external cleaning and watering vegetation. Apparently, it is done because of the dramatic population growth and the need to slow the need for new complete plants.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[GoldDredger]

Doesn't make sense to me as far as the parking drains/tiles. The net result is the storm flows go into the underground storm system in both cases. By pumping, all they do is place the storm flows temporarily on the surface, where it then drains to the underground storm via surface inlets. All they get out of that is the potential nuisance to pedestrians with increased surface sheet or gutter flow (or overloaded inlets). In the case of deep parking garages, you'll probably have to pump anyway because it will be lower than the outside gravity lines.

For building foundation drains however, I imagine they are mostly pumped anyway, with the foundation collection point likely lower than the available gravity line in most cases. Also I wouldn't want foundation drains tied directly to outside storm anyway, because if that storm drain surcharges it could push water into the foundation area, or at the very least prevent gravity drainage away from the foundation.

There is nothing wrong with just asking your contemporary down at the City what the reasoning behind this is either.

 

[dicksewerrat]

I used to work there. We had lots of issues with suspended solids in the storm system. Spent lots of money installing grit chambers, settling ponds, cleaning out deltas at the out falls to the lakes and streams. The Mississipi has to be dredged to allow barge traffic.This may be a way to also require some settlement time before the storm water hits the City owned storm drain and the ability to find persons that might put something else into our lakes and rivers.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[civilman72]

I'm curious how long the city has been requiring that groundwater be discharged to the surface?

I live/work/design in a similiar climate to MINN, and can only imagine the freezing issues at all of these outlets, causing both unsafe (slippery) pedestrian conditions and numerous pump failures from backups/clogging in the pipes.