New EPA Turbidity Discharge Limits

[ClarkBart]

Hi:

I was wondering if anyone has been able to decifer just what EPA is trying to propose with its new turbidity effluent limitation for construction sites. It doesn't seem to be a hard proposal for a regulation but more of a request for comment on several proposals. Anyone have any insight on this? This is the link to the announcement:

http://www.epa.gov/ost/guide/construction/

Thanks, Bart

 

[Drumchaser]

Hey

This is what would be invasive to us.



..."establish a limit of 13 nephelometric turbidity units (NTUs) for construction sites 30 acres or more (total project area) in areas with an annual R factor of 50 or more, and soil with 10% or more clay"...
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NTU
A unit measuring the lack of clarity of water, used by water and sewage treatment plants, in marine studies, and so on. Symbol, NTU, or ntu. Water containing 1 milligram of finely divided silica per liter has a turbidity of 1 NTU. The NTU replaced the Jackson turbidity unit.

The NTU is measured with an electronic instrument called a nephelometer. The water to be measured is placed in a standard container. A light beam passes through the water and strikes a sensor on the other side of the container. A second sensor is mounted at right angles to the beam, measuring light scattered by particles in the water. From the ratio between the light intensities at the two sensors the turbidity in NTU can be calculated.

To calibrate the device a standard solution is needed. An early approach was to suspend a measured mass of silica in a measured volume of distilled water. In another approach, defined quantities of reagents were mixed to produce a fine precipitate. The current technique employs microspheres of polymer, which led to a new turbidity unit, the Formazin turbidity unit (FTU). Measurements in NTU and FTU are roughly equivalent

Not that I can quantify in real terms how this will effect industry, it is safe to assume it will cost more $$$ and time to comply with reg.s

 

[ClarkBart]

Thanks for the review on turbidity measurement. The mechanics of getting measurements is going to be a challenge some regulators in NYS insist that current state laws would require the samples be done by a certified lab. This seems a little inconsistent with other programs where certified operators can measure turbidity and report it on their permit DNRs.

As far as the one line you picked up on from the EPA notice, "13 NTU", I saw that but also saw much more. So much more I got to the point I couldn't really tell what EPA was proposing any more. I guess I'll have to study it more. Unfortunately, I'm not sure how much utility there is in studying this regulation if it will be changed in the future and am not sure how much impact I could have by making a comment on their proposal if I can't understand their proposal in its entirety.

Anyone know of an informational session concerning this proposal in the NY or CT area?

 

[TerryScan]

Clarkbart,

Regarding lab testing: One of the two reasons EPA gives for choosing turbididty as a standard was that it could be measured in the field:
"turbidity can be easily measured in the field while TSS requires collection of a sample and analysis in a laboratory. Since most BMPs and treatment systems are flow-through systems, TSS would not be a practical means of estimating compliance because permittees would not be able to verify whether or not they had met the standard before discharging. With turbidity, permittees can measure turbidity levels in discharges continuously and adjust treatment parameters accordingly or recycle effluent if they are in danger of exceeding the turbidity limit."

 

[ClarkBart]

Turbidity measurements are taken and used for reporting by operators in other NPDES permit programs; however, most states require that those who take these measurements be done by licensed operators or certified laboratories. This seems to argue for certification/licensing or the person taking the turbidity measurements on construction sites. I'd feel a lot more comfortable about the reliability of the measurements if they were done by someone with at least a little training in the use and care of the "continuous" monitoring equipment and sampling protocols. For the size of the sites that they are talking about, this does not seem to be a huge burden. If it applied to very small site, certification/licensing would be a real problem.

In NYS, there is no licensing of contractors, but, there is a training requirement. In CT, there is a contractor "registration", but the training requirements haven't been in the construction permit. What's in like in other areas?

 

[TerryScan]

In Delaware, every job site must have at least one person onsite at all times that has taken a Contractor Certification Course. Additionally, most sites (not small projects like typical single family lots), require the developer to hire a Certified Construction Reviewer (CCR) who is under the supervision of a PE. The CCR makes inspections at specified stages of construction discussed at a pre-construction meeting as well as on a periodic basis. The CCR submits reports to the agency delegated to enforce sediment & stormwater regulations.

http://www.swc.dnrec.delaware.gov/Pages/SedimentStormwater.aspx