Emergency Storm Drain Repair

By Chris Poston | April 18, 2023

Excavation Shoring

 

Before joining the team here at D.H. Charles Engineering, I had only briefly heard of excavation shoring. Dig a hole, install supports, and ensure that the walls of soil don’t cave in. Although that is technically true, it barely scratches the surface of just how crucial and complex these systems can be. As a new engineer on staff at DHC, I was given the opportunity to work on an excavation shoring project that would set the tone for my early career by providing valuable tools and skills, highlighting the multitude of expertise and experience of the staff here at DHC, and demonstrating how crucial teamwork is to our success.

 

The project was located in Chula Vista, California, just south of San Diego, and our team was tasked with designing a shoring system that would allow access to a set of 84-inch diameter storm drain pipes located deep underground below a shopping plaza parking lot. These storm drain pipes and connecting junction box structure were in need of serious repair and after ironing out the layout and details, we got a sense of just how large this pit needed to be. And to highlight that magnitude, here are the statistics:

 

  • 60-foot max excavation depth
  • 31’-6” wide
  • Nearly 215-feet long
  • Largest design steel size: W14x233
  • Largest soil pressure load: 1,370 lbs/sq ft
  • Largest design load: 812,000 lbs

 

The main challenges behind this project came from the level of complexity and detail that went into designing the shoring pit. Accounting for angled brace levels, sloping soils, and large equipment/slope surcharges, there were quite a few conditions to consider in the design, and as a newer engineer, those challenges felt daunting. But very quickly those nerves subsided as support was never far away. With help from my team, I was able to dive deep into the details of geotechnical loading and steel design and really begin to grasp an understanding of these systems and the engineering theory behind them.

 

When it was all said and done and the dust settled, we were able to take a site visit out to see the shoring pit in person. Standing almost unassuming at the rear corner of the parking lot was the fenced in construction site. However, as we walked into the area and closer to the edge of the pit, the depth of the pit grew. Standing at the guardrail along the edge of the pit, the true size of it came into view. The sheer size and depth of the pit was enough to make you nervous and the massive beams seemed to magically suspend in the air. Having never seen an excavation shoring pit up close, this was undoubtedly one of the highlights of my early career.

 

This project was a great testament to the work that is done here at DHC. Trusting in each other’s abilities and relying on seamless teamwork, it has been a special opportunity to be a part of DHC.

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