
You can’t get a good seal with a sand bag berm. Dirty water down the drain.
You can’t get a good seal with a sand bag berm. Dirty water down the drain.
The sample on the left is just under 1 NTU, the middle is 25 NTUs, and the one on the right is 250 NTUs. In Washington state, the Construction Storm Water General NPDES Permit lists benchmarks that construction discharges must meet. These are: 0-25 NTUs everything is cool; 26 -249 NTUs not so good, upgrade your site best management practices (BMPs) and modify your SWPPP; 250 NTUs and above, call the Dept. of Ecology, upgrade BMPs, modify the SWPPP and monitor the water body that the project discharges to until you are in compliance.
My construction erosion inspection turned up a turbid discharge. A little bit of sediment track out each day builds up. The contractor was vacuum sweeping this area on a regular basis but the first rain shows how effective that was. I measured this discharge at 6000 nephelometric turbidity units (NTUs) using an old Hach 2100P turbidimeter. This meter only reads up to 1000 NTUs, so I had to dilute the sample 3 times to determine the actual reading.
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