Throughout her successful and storied career, Ms Staheli has served in many trenchless industry roles in all corners of the United States.
Her trenchless career began almost as soon as she finished her undergraduate studies.
Upon graduation from Rensselaer Polytechnic Institute in upstate New York, she was hired by a trenchless contractor who had purchased microtunnelling equipment approximately three months prior.
“I spent a tremendous amount of time in the field, learning the ropes as a young engineer on microtunnelling projects and seeing how the construction industry worked from the contractor’s perspective,” she recounted to Trenchless Australasia.
Ms Staheli later moved to Seattle in the Pacific Northwest, to work for another contractor who owned microtunnelling equipment.
“With this contractor I gained some experience with project bidding and resource management. They had a “÷you bid it – you build it’ policy, so I got a quick lesson in stressÉ If you ever wondered why most superintendents have grey hair!”
Ms Staheli’s trenchless repertoire expanded considerably at her next posting, working with the United States Army Corps of Engineers down south at the Waterways Experiment Station (now called ERDC) in the geotechnical laboratory in Vicksburg, Mississippi.
“During my time there we performed full-scale research projects on both microtunnelling and horizontal directional drilling (HDD). The results of this research culminated with technical reports to give the COE guidance for the use of trenchless technologies beneath critical structures.
“At the Corps we worked extremely hard – both physically and mentally. But it was also some of the most fun work in which I have ever participated.”
Following her time at the Corps, Ms Staheli returned to Seattle where she founded her own consulting business, Staheli Trenchless Consultants.
Along the way to Seattle, Ms Staheli’s spent time in Sacramento, California, and Atlanta, Georgia.
“While in Atlanta I took a brief timeout to complete a PhD in Civil Engineering at Georgia Tech,” said Ms Staheli.
“My research and dissertation completely focused on the trenchless field, the culmination of which was the development of an equation to estimate frictional jacking loads on various pipe material based on pipe surface roughness characteristics and frictional soil properties.”
Risky business
These days, Ms Staheli is looking into further developing specific trenchless techniques such as pipe ramming, a particular challenge in her home state of Washington due to the region’s soil conditions and high levels of groundwater.
“We are finding that pipe ramming, even under significant groundwater pressure, and high percentages of gravel, cobbles, and boulders, is able to successfully install steel casings,” she said.
For Ms Staheli, pipe ramming is a technology still in its engineering infancy.
“It is within the last ten years that engineers and scientists have been studying the mechanisms that govern the forces that are applied to the casing during ramming,” she continued.
“Tremendous advances have been made on measuring the force waves that travel down the casing, hit the tip of the cutting shoe and rebound back to the hammer connection. Great strides have been made on the engineering design parameters of the cutting shoe, and equations have also been developed for determining the distance that can be rammed in a particular soil with a given pipe diameter and hammer size.”
As well as installation techniques such as pipe ramming, Ms Staheli has also divided her time examining the risk profiles for each Trenchless Technology.
“Lowering risk on trenchless projects is a subject that I have focused on over the last 15 years of my career,” continued Ms Staheli.
“My goals have been to assist in the selection of the most appropriate Trenchless Technology on parameters other than just cost. I urge others to look not solely on initial price but rather on a balanced price that includes two components: one for initial price and one for risk price.”
To determine risk price, the first step is to evaluate the feasible trenchless technologies for the specific project conditions, explained Ms Staheli.
Specific risks are then developed for each technology and the probability of the risk occurrence is determined relative to the trenchless installation method.
The impact (or cost) of the remediation measure is determined should the risk occur.
“Finally, the risk cost is determined by evaluating the probability times the impact,” said Ms Staheli.
“The owner can then select the technology based not only on the initial cost, but also based on the probability of a significant risk occurring and the risk mitigation costs, should the risk occur.”
Trenchless trends
To keep a weather eye on the evolutions and changing trends of the trenchless industry, Ms Staheli has shrewdly watched the behaviours and activities of the thousands of attendees at the NASTT No-Dig shows.
“We study their movements and check attendance numbers to see what technical sessions they attend,” she explained.
“From our analysis, it is clear that municipalities are trending toward rehabilitation methods rather than installation of new methods. It is also clear that if pipelines are installed with new methods, they are likely to be installed with HDD.”
Ms Staheli and the rest of the NASTT board have also noticed a significant trend towards the rehabilitation of water pipelines.
“Evidently, the industry is looking for some innovative ways to rehabilitate high pressure water and gas lines.”
Mesmerising advances
For Ms Staheli, the challenges and ever-changing technologies of the trenchless industry keep her an active, interested participant.
“The advances in the technology are mesmerising,” she said. “Things that were not possible last year are being successfully accomplished today.”
Because of this rapidly changing field, it takes a certain type of person to thrive in the trenchless industry – one who is not afraid to think outside the square and is willing to take chances, concluded Ms Staheli.
“You must be innovative, creative, and have the wisdom to know when to take a calculated risk and when to walk away,” she said.
“Of course, there are winners and losers when it comes to the game of risk. However, the result is an opportunity for constant learning – something that keeps me going.”