Sheetflow Erosion Control Erosion Control for the CESCL

March 18, 2020

What’s the Point of Sweeping?

Photo: David Jenkins

What’s the point of sweeping? Okay, lets sweep, pick up as much sediment as we can, drive around a whole bunch, re-apply the sediment, drive around some more, pick up the same sediment… job security maybe. This is the result of not maintaining the sweeper. The door gasket is damaged and needs to be replaced. This sweeper also had rust holes in the hopper door. I told the contractor to remove it from the project and don’t return it until it’s fixed.

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.

October 21, 2019

“Means and Methods” vs. Best Management Practices

Demolition of landside crane rail on a shipping container terminal.

In my experience, managing contractor “means and methods” is more important than using the “right” best management practices. When turbidity is the standard for measuring water quality compliance, as in Washington state, site cleanliness is the key to prevention and compliance.

This contract requires that catch basin inserts be installed in all catch basins within the project boundaries. However, inserts are not at all effective in reducing turbidity in runoff. While removing the crane rail on this container terminal project, the contractor could clean up as the work progresses, place all material removed from the trench onto plastic for later removal, load into a Bobcat bucket, and pick up small debris with a shop vac. I can require these things in the contract that the contractor bids. It may cost extra; the extra cost may be worth it if it reduces my risk. If I tell the contractor after the contract is awarded, I will pay more.

I can also make suggestions during the work, pointing out that keeping things really clean will keep them in compliance with their NPDES permit. If framed in a way that shows benefit to the contractor, meaning reducing risk and cost, they will probably follow the suggestion.

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