We’d been trying to figure out where the pervasive smell of heating oil was coming from. Turns out someone’s tipped 20 gallons of used engine oil into a storm drain along the street. It’s all collected in our community sewage treatment plant at the edge of the woods just down the hill. From there the smell must have found its way back up the sewers into the houses and other neighbours have the same problem. They’ve also destroyed all the microorganisms in the sewage tank and polluted the stream.
Absolutely no idea how they could have done this without anyone noticing. The drains are right outside the houses.
Northumbrian water came on Sunday to pump out the pollutants but the smell persists. Any ideas how we might safely flush it out of our system?

A biodegradable Citrus degreaser would get rid of the oil residue and the smell from the system, you can then flush the system with water to get rid of the degreaser.  But it’s a question of how much you’d need to clean the whole lot…?

Do any of your neighbours have a habit of doing their own car servicing?

In time the bacteria in the plant will recover and ones that can digest the remaining oil will multiply and get rid of it. But it takes time.

The shortcut is to get a few drums from an oil refinery’s anaerobic treatment plant (I presume your tank is anaerobic) as they’ll already have the right bacteria.

I’d be wary of flushing vast amounts of bleach, degreaser, or anything else to try and flush it out.  Water treatment plants are their own ecosystem, given enough time something will colonize it that will break down anything that’s present and they can react to changes in the effluent. But only slowly, gallons of oil all at once is a problem, someone being an idiot and pouring their jam jar of chain cleaning white spirit down the drain, or residual cooking oil likely wouldn’t be. Chucking a load of any chemicals down there now will only make things worse.

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Northumbrian water came on Sunday to pump out the pollutants but the smell persists. Any ideas how we might safely flush it out of our system?

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Go back to them and complain?

You say community treatment plant, who is responsible for it? Northumbrian water or the residents?

Do any of your neighbours have a habit of doing their own car servicing?

20 gallons though?

How much is a gallon in metric 5L? That’s about what my car takes in oil.

Can WCA account for his whereabouts?

20 gallons though?

less than a normal-sized oil drum so would make sense if someone had been tipping it into one bit by bit in their garage then decided to get shot of the lot in one go.

doesn’t help with the current problem but has anyone got doorbell cameras/CCTV?

I was wondering why a storm drain goes into a small sewage works ?

Put your issue to a buddy of mine who is a water treatment specialist with Thames  Water, here’s his response.

Washing up liquid. Sounds stupid. But it’s a degreaser, breaks down oil, and will clear the pipes. If the water board have already pumped the pollutants out then it’s just residual in the pipes. Don’t go and dump 20 gallons down, just a little bit of washing up liquid and then hot water. If they all did it once or twice a day it will clear really quick and the bacteria in the sewer is capable of coping with the soap.

If it is impacting on the stream you should tell the Env Agency (in England) if you haven’t already. You can call them on 0800 807060

I assume it is a private treatment system? If so, does it have an environmental permit and who is the permit holder?

You also need to make sure that whatever you do does not exacerbate the situation and cause more pollution.  Detergent may help the oil mix with water and pass through the treatment system and into the stream.

I was wondering why a storm drain goes into a small sewage works ?

Does seem a bit odd.

My guess is they’ve lifted a manhlole cover and tipped it into the raw sewage system. Explains why no one saw them tipping it down a drain in the street. How do you know it was 20gallons – did they leave the drum somewhere? If so, any clues as to the source of the drum?

I was wondering why a storm drain goes into a small sewage works ?

Does seem a bit odd.

off topic alert

road gullies and surface water drains were frequently plumbed into a combined sewer – thought process was that a good storm would flush debris down stream to clean them out.

This is no longer best practice and a combined drainage system should be built for any new build. Certainly north of the border there is work underway to systematically reduce the number of combined systems in operation. This increases system capacity and also reduces flood risk – climate change has already happened when you look at rainfall patterns and intensity in that regard

<span style=”font-size: 0.8rem;”>However whilst laying new pipes is easy enough (all be it expensive and disruptive) it’s often not possible to physically find land to physically fit a SUDS pond to provide treatment of surface water and provide storm flow attenuation into the receiving water course. For these older streets & neighbourhoods they will remain on combined sewers for the foreseeable.
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as you were

I deal with domestic heating oil spills for insurance companies.

Firstly I’d say this could be within thier purview. Its worth calling them to discuss. Obviously depends on the specifics of your policy.

How you manage this depends on how much is left in the package treatment works. Domestic systems are aerobic based and the bacterial colonies are usually killed by suffocation due to being coated with oil.

Long chain mineral oil, complete with post combustion products will take a bloody age to naturally attenuate if its present in any more than an irridescent sheen.

If there’s anything approaching a layer you’ll need to get it pumped out at great expense.

Typically these systems drain to soakaway or a surface water somewhere. Whilst putting detergent into the system will work for residue, the down stream environment is likely to receive deleterious impacts from this. Normal practice is to block the discharge point, sluice and recover, like washing out a sealed vessel.

Lastly, used mineral oil from engines smells nothing like heating oil because VOCs are materially absent. If is does smell like heating oil (kerosene) then its got something else in it too.

Lastly, used mineral oil from engines smells nothing like heating oil because VOCs are materially absent. If is does smell like heating oil (kerosene) then its got something else in it too.

More than likely a cocktail of vehicle fluids, even more so if its a home mechanic. Chances of them separating waste liquids from a vehicle?

I would say that someone has more than likely just poured it down the foul water manhole inside thier property rather than poured it down a road gully. Which is why you wouldn’t have noticed them doing it.

Oh, and I’d report it to the Environment Agency (if it’s England).

If you are off grid for sewage are you also off grid for gas and use oil for heating?  Is it definitely engine oil?

This is no longer best practice and a combined drainage system should be built for any new build

Ours is 9 years old and has a combined drainage system.

Thanks for all your replies, wise and helpful as usual. To answer a few questions: I live on a Terrace of 18 former mining cottages, which stands alone next to a B road. The  little sewage works deals with our street and probably a couple of other houses further up the hill.

The information about what was tipped, where and how much came from the Northumbrian Water people who came to pump it out. They said they removed 20 gals of dirty engine oil from the settlement tank. They own this and are responsible for our sewage too.
I guess what scruff9252 says is true: it’s a combined storm drain/sewage works. Not sure when it was built but probably when people started getting indoor netties in the 60’s or 70’s.
As someone asked, we don’t have mains gas here so some people do use oil including both our neighbours so at first we suspected a leak. It possible that this is true and we have two problems to deal with, but since others people at houes further along the street have also complained about a smell of oil in the house it would seem a weird coincidence.

The only guy who does his own mechanicking has lived here over 40 years and is as sound as they come. Their house is one that’s been hit by the smell and they alerted NW while I called the Environmental Agency. NW say they are treating it as a major incident which means they will investigate it but who knows what that might amount to.
The whole thing seems very strange. Why would anyone choose to tip the oil into the drains on a street directly overlooked by all the houses?
We had already thought about calling our insurance company and I think that might be the next step.
The worst smell is in the cupboard where our washing machine lives and it’s too heavy and confined for me to pull it out.

It possible that this is true and we have two problems to deal with

If it was a leaking oil tank it would still be leaking into the drain.

As far as I know they’re not repairable…… Anyone got a new tank?

I’ve just had a new heating oil tank installed – came to about £2000. It is a plastic bunded 1250 litre tank and they took the 30year old steel tank away and transferred the contents to the new tank.

Just background info to answer sharkbait.

Steel would be repairable but I wouldn’t fancy welding or plating it given that it would normally fail on a weld, and plastic isn’t repairable – at least not reliably