Sheetflow Erosion Control Erosion Control for the CESCL

June 30, 2020

Sand Bag Berm Around Catch Basin

Photo: David Jenkins

You can’t get a good seal with a sand bag berm. Dirty water down the drain.

May 7, 2020

Turbidity 1-25-250 NTUs

Photo: David Jenkins

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.

February 25, 2020

Construction Erosion Inspection-Turbid Discharge

6000 NTUs Photo: David Jenkins

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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