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EWEB identifies abandoned ‘partial’ drill hole as root cause of blasting incident

Contractor will use flags to improve communication between drill, blast crews
Blasting could resume next Tuesday, Nov. 9

Nov. 3, 2021

Dear East 40th Neighbors,

On Nov. 2, EWEB’s contractor conducted a controlled underground blast at the E. 40th water storage site. An incident occurred during the blast which resulted in flying rock and debris.

While there were no injuries, a house adjacent to the construction site sustained some cosmetic damage.

Although blasting is performed through a professional subcontractor, EWEB is ultimately responsible for the overall project and is taking this incident very seriously. We are committed to doing our part to maintain a safe and well-managed worksite, and to protect the safety of our customers.

EWEB’s project manager was on-site at the time of the incident. The immediate response was:

1. Safety – check on neighbors who were in the area when the incident occurred.
2. Cease work – contractors were instructed to stop all work on the site.

A Root Cause Analysis Report was performed by the blasting contractor to determine what happened, why it happened and what the contractor can do to make sure it doesn’t happen again.

The analysis determined the incident resulted from an oversight by a drill operator.

The operator drilled a partial hole, then abandoned the hole without placing a visual marker to alert the blasting crew. Because the partial hole was unknown, the blasting crew did not take measures, such as packing and fully covering the hole with blasting mats, to prevent material from being ejected during the blast.

No problems were identified with the design, material or equipment used in the blast.

A few neighbors noticed that the Nov. 2 blast was louder or stronger than the previous test blast on Oct. 28.

Seismographs show that the vibration levels on Nov. 2 were not significantly different than the test blast last week. However, the air pressure from yesterday’s blast not being contained underground may explain why this blast felt stronger. Having said that, we understand that sound and vibration are experienced differently for everyone. Some folks are more sensitive and may wish to be away from home during future blasting events.

The contractor has submitted a plan to EWEB for preventing similar incidents from occurring in future blasts.

The plan includes expanding the footprint of blast mats to extend 20 feet past the last loaded hole, and retraining workers to ensure they mark any drill hole anomalies with visible flags.

EWEB’s Safety Officer has reviewed the contractor’s plan and we are satisfied that these corrective actions are appropriate to prevent future incidents. Once we have verified that all required remedies are done and in place, we will authorize the contractor to resume blasting. We expect this will happen this week, allowing blasting to resume on Tuesday, Nov. 9. If that changes, we will let you know.

We understand that even with these measures in place, you may have additional questions and concerns about site safety. Whenever a safety incident occurs on a job site, EWEB expects all involved parties to step up, provide a full and honest accounting of events, take responsibility for their part in what happened, and then work together to take corrective actions. That’s exactly what is happening here.

We have asked the contractor to prepare a letter to neighbors with additional information about the Nov. 2 blasting incident, their analysis and safety measures. We will forward the letter to you as soon as we have it.

What to expect at the site this week

While the contractor is finalizing their remediations, we will continue with some other work on the site beginning tomorrow, Nov. 4.

Workers will be preparing the entrance of the site for paving. This is intended as an additional erosion control measure to reduce the amount of sediment leaving the site and entering the gutter.

As part of the paving, workers will begin drilling a perforated grid in the rock at the entrance. This drilling work will happen tomorrow and is necessary to prepare for the pipeline that will eventually be installed down Patterson St.

Paving will occur on Friday or Monday.

There will be no excavation or blasting until at least next week.

As always, please don’t hesitate to reach out to the project team if you have questions.

Contact us with questions

If you have questions or input, please don’t hesitate to reach out to the project team at 541-685-7899 or Emails sent to this address will reach:

Laura Farthing, Project Manager/Senior Civil Engineer
Jen Connors, Communications Supervisor
Jeannine Parisi, Customer Relationship Manager
Wally McCullough, Water Engineering Supervisor

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