Underground Injection Wells

This follows up on my ion exchange post from a couple weeks back.

The wastewater division at the state refused to let us put our IX backwash effluent into the septic system. He is concerned with the impact of the high nitrate and sodium water on the treatment efficiency and the potential for soil swelling. Basically, there's nothing we can do to get him on board with this.

So we are proposing to build our own little leachfield to dispose of the nitrate laden water, by microbial action and dilution. We are designing it exactly like a leachfield, except here's the catch. Since it's not sewage, it's permitting under the underground injection control rules. Essentially they are calling this a Class V well.

Anyone ever designed or permitted something like this? The design is going fairly smoothly and simply, but I haven't done this before and was wondering if anyone has any experince in this they'd like to share?

I have reviewed/approved the design and use of Class V injection wells as part of in-situ remediation projects. In my experience, the injection points are used as the point of entry for fluids that will enhance biodegradation of chlorinated solvent species. Most of the injectates are strong oxidizers (potassium permanganate, hydrogen peroxide, sodium persulfate, etc.) or a substrate/food source (lactate, food grade oil, etc).

My state provides criteria for which Class V monitoring wells must be constructed, operated, and monitored - check out Florida Rule 62-528.605, .610, .615, F.A.C. and to some less extent (for your purposes) Florida Rule 62-528.620, .625, .630, .635, .640, and .645, F.A.C. You can check out this rule at Rule 62-528, F.A.C. - Undeground Injection Control

In a larger number of cases I have also used provisions of 62-528.705, F.A.C. so that the injection systems are setup as a close-loop system as an added measure to ensure the injectate does not move beyond the zone of discharge allowed for constituents in the injectate that might violate groundwater quality criteria based on the quantity injected into the aquifer.

As far as your design is concerned you are obviously concerned about nitrates - I assume that you are treating to the groundwater criteria at the point of injection? If not, you would need to know what areal extent you are allowed to exceed that criteria to allow for attenuation.

Also, do you have a good feeling for the groundwater quality in the area you are injecting? Are there any other parameters that are elevated or exceeding criteria - (e.g. chlorides, sulfates, TDS, etc.)? One other thing - in Florida there has been a problem with mobilizing Arsenic with injected water. That is why the so-called Aquifer Storage Resevoir (ASR) hasn't panned out as a viable solution for the water crisis here. I don't know if Arsenic presents itself as a water quality problem in VT but here it is a nightmare for both water and soil contamination.

Post follow-ups if you have any questions

JR

Hmm... I think it might be a stretch to call that an injection well, but it can be done by a regulator willing to go that route. Or, if the state regulations for injection wells are made more broad... But at any rate, it doesn't matter what you call it. You're going to have to deal with the regualtor guy and solve your problem. Even here, where I wouldn't call this a Class V well, I would still call it "land disposal of wastewater" and require the same level of scrutiny/permitting.

I'm not surprised at all that they won't let you discharge into a septic system. I wouldn't let you do that either, and would have advised against it if I had known that was what you were proposing. Shame! :15:

As far as the dedicated disposal field goes, don't count too heavily on microbial action knocking down the nitrate levels. Conditions for de-nitrification are very unlikely to occur if you're in sandy soils, as you said before. But now you say the regulator is worried about swelling clays. Could you provide us a description of the soil profile at the site? Groundwater depth? Underlying geology? Have you done the soil investigation yet?

You're probably going to just have to count only on dilution of the nitrate in the groundwater. I mean, come on Mr. State regulator: the whole purpose of the IX system is treat groundwater that is high in nitrate, right? Where does he think the removed nitrate is going to go? It's going to be the same problem if you go with reverse osmosis. I'm not sure about the other nitrate removal methods, but it might help your cause with the state if you can do a quick comparison of available removal technologies and show them that the disposal of nitrate-rich effluent is an unavoidable outcome, no matter what you choose.

Otherwise, if the state continues to give you a hard time, you might not have any option but to hire a hydrogeologist to model the nitrate dispersal under the site, and show what levels it will cause at (any?) nearby water wells.

Update: Just finished everything I need to submit for my 2 permits on this one. Just have a fellow engineer familiar with the site giving it a once over.

This sure is a whole lot of crap to go through for 89 gpd of backwash water. :brickwall:

^^^ Heh .. I am getting flack from another regulatory agency because I have required an increase of 60 gpm capacity on a P&T operation to effectively capture a plume. Apparently the other agency feels that the increased recovery will alter (cause to dewater) an adjacent area classified as wetland. :wacko:

Now it is time to whip out our models and discuss flow patterns. Yippee! :happy:

JR

I was working with a guy from a water treatment company who is designing and furnishing the actual IX units. Based on that I laid out the injection area and process piping.

So I was talking with this guy yesterday, because I needed an estimate of the constituency of the backwash water, as requested by the state.

He made a great point. One way or the other, the same amount of NO3 is getting into the ground, whether it goes through you or through the IX units, so why are they making us jump through all these silly hoops.

As an aside, the fact that we are only putting 17.2 mg/L of NO3 into the ground is promising. I have no doubt whatsoever it will be well below the MCL of 10 once it reaches the property line.

VTEnviro said:

As an aside, the fact that we are only putting 17.2 mg/L of NO3 into the ground is promising. I have no doubt whatsoever it will be well below the MCL of 10 once it reaches the property line.

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How did they go about granting a zone of variance?

JR

By that I assume you mean an area where you are allowed to exceed the MCL?

This is the way they do it in Vermont at least.

You need to identify all wells within a 1/4 mile radius of your injection site, and evaluate if they are going to be impacted by your plume. This was fairly easy to do as most of these wells (11 or 12 of them) are hydrologically isolated from our plume for one reason or another. In other words there is a confining layer between where we are injecting out stuff, 3 feet below grade, and where most of the wells are cased, 200+ plus. This will prevent our water from getting down to where the other well intakes are. Also the topography of the site isolates a number of the wells.

Luckily, our firm did a big septic system project at this site 10 years ago. They hired a geologist to put together a hydro study showing the direction of groundwater flow. I was able to use that in this project to prove some of our points.

The other criterion here is you need to meet the MCL at the point of compliance, which in this case is the property line. We stuck 2 monitoring wells in the ground there to measure baseline levels. We are on the hook to either not exceed the MCL, or not to cause any further noncompliance if it is already is exceedance.

If you are interested in the technical stuff of what we did, I'd be happy to pass some of our work your way.

89 gpd is a joke. Anything under 55 gpd, we don't even bother to permit (as log as it isn't hazardous). I thought you were talking about substantially larger quantities.

But seriously, if the whole point of the IX system you isntalled is to treat groundwater that already exceeds the MCL, then the property boudary rule is a little absurd. And your friend was absolutely right about the mass balance thing. It does sound like you are dealing with a real PITA regulator.

Not a totally cool one like me. B)

But seriously, if the whole point of the IX system you isntalled is to treat groundwater that already exceeds the MCL, then the property boudary rule is a little absurd.

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Their rationale there is that if you are already in exceedance of the MCL at the point of compliance, then your discharge can't worsen the noncompliance. Based on the water chem calcs, it looks like we will be injecting 17.2 mg/L of NO3 into the ground. Most of the the recent GW samples in the area have been 3-4 mg/L range so I'm sure there will be ample dilution.

Not a totally cool one like me.

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The thing I've noticed about regulators around here are the ones that are really sharp and know their stuff are the ones most likely to waive a requirements or let you do some non-standard technique. It's the ones that aren't as proficient and competent that hide behind the rulebook.

Well the permit applications went out to the UIC and Water Supply divisions of the state DEC today. So I'm off the hook on this job for a couple months or however it takes to hear comments back from them. I haven't dealt with UIC here so I'm not sure what to expect.

Overall the project went pretty smoothly. We had a vendor provide us with all the treatment equipment and specs, which I just slapped onto a pipin diagram. I'll be interested to see what the state thinks of things.

Update: Got the UIC permit. No comments, even got complimented by the lady at the state!