I was wondering how folks are regulating temporary construction dewatering from applicable MS4 sites and non-MS4 sites. Are you relying on the contractor to obtain coverage under COG080000 or have the regulations in place to require contractors to seek coverage under COG080000? Or does your MS4 have specific dewatering requirements or even a dewatering permit? Do you have the ability or have tried to request sample results from contractors?

I am increasingly dealing with illicit discharges from construction dewatering and besides utilizing our illicit program for enforcement do not have other enforcement options, and outreach has not been very effective. Even when the discharge is covered under COG080000 the required sampling frequency being once a week is somewhat of a joke. At any point in time especially when starting up pumps, sediment can be released for days until they decide to collect their weekly sample.

Also, its challenging to determine at what point a dewatering discharge becomes an illicit discharge even if covered under COG080000. I make my determination based on the visual turbidity difference between the discharge and the receiving water which so far has stood up in court based on our illicit discharge ordinance but at some point, will likely be challenged. How do other folks make their determinations?

Any thoughts or comments would be appreciated. Thank You

Scott Slamal, Stormwater Specialist and Engineering Inspector, City of Steamboat Springs

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Hi Scott, all good questions.  This is the time of year when a dewatering operation can cause an ice dam, public nuisance, depending on where their discharge locations are.  My philosophy about dewatering has shifted a bit over the years.  Although we do require our permittees to obtain a dewatering permit once they get their Geotech back to determine the depth, I don’t monitor the actual activity too much anymore.  As you know, ground water belongs to the state, which is why we don’t issue our own dewatering permits, as we do with stormwater permits.  The information that I provide at precons is, that a dewatering permit will be required if the permittee feels as though they may encounter ground water.  I also add that smaller amounts of ground water can be used for beneficial use on site, such as filling up water trucks or using it for dust control and compaction, providing it doesn’t have the ability to reach our MS4 or State waters.  I specifically rechecked this option with Al a year or so ago. 

I ask our permittees to supply us a copy of their dewatering permit so that, 6 months from now, I’m reminded that they have one, and I’m also interested in what discharge locations the State gives them and how often they require DMRs. If the discharge location runs through our MS4,which it occasionally does, I feel more compelled to look at the quality of the product they’re exporting.  Does that make sense? As well, if the project is a CIP project the City is a dual signatory on that COR permit, and we therefore have more of a stake in assuring their discharge isn’t sediment loaded, or TSS etc.  I often check filter bags and their placements to ensure that they’re not sediment loaded (need to be replaced) or that they have more than one hose running into the bag (Filter bags aren’t designed for more than one hose at a time and will usually leak out of the opening with two hoses). 

You also asked about enforcement.  In Longmont, if a permittee has a City stormwater permit (SCAP) any enforcement related to dewatering would be addressed through that permit. And, I’m been known to issue stop work orders when needed. For example, if a permittee was discharging ground water without a permit to our MS4, or to the neighbor next door.  If a ground water discharge is occurring on a small build site which does not have a City stormwater permit, they’re still required to obtain a dewatering permit and use control measures, in which I would ask them for proof of that rather than searching endlessly through ECHO.  If it was minor thing, I would probably first attempt a little education and outreach and advise them that small amounts of ground water can be directed back onto their limits of disturbance (LOD) to percolate back into a vegetated area, providing it doesn’t have the ability to leave their site.  If that small build site without a permit was conducting a larger scale dewatering operation to our MS4 without a permit, I would then use our municipal code for illegal discharges to engage in enforcement, yes. 

Hopefully this is useful, but if I missed anything please let me know.

Jon Allen, (IDDE) Illegal Discharge Detection and Elimination Coordinator, City of Longmont

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I would suggest leaning into the MS4 IDDE permit requirements for basis.  The permit either allows CDPS permitted discharges or, if they’re not permitted, but should be, the permit identifies them as illicit discharges for which the enforcement can be notification to the Division:

I.E.2.a.v. Discharges that can be Excluded from being Effectively Prohibited:

• (G) Uncontaminated pumped groundwater (Note: Discharges containing groundwater that comes into contact with construction activity is not considered “uncontaminated” due to the potential for sediment content.)
• (V) Discharges authorized by a CDPS or NPDES permit

I.E.2.a.vi. Removing an Illicit Discharge: When an illicit discharge is identified, the permittee must remove or require the removal of the source of the illicit discharge. The permittee must also cease or require the cessation of the illicit discharge. After the illicit discharge has been ceased, the permittee must also minimize surface contamination by removing or requiring the removal of surface residue or other type of pollutant source. The removal requirement can be met by notifying the Division through a written report when CDPS or NPDES general permit coverage is available for a discharge and the discharge is not subject to prohibitions against issuance of a permit in regulation 61.8(1). The permittee must also have written procedures for requiring cleanup from the operator and procedures for cleanup conducted by the permittee, when necessary, to remove materials associated with the illicit discharge.

Hope that’s helpful?

Tracey Pond, Stormwater Program Manager, City of Golden