The City of Salisbury, Maryland, the largest city on the Eastern Shore of Maryland, recently used helical piles in an underpinning application to address infrastructure issues at their Park Water Treatment Plant facility. Buildings at this municipal utility were experiencing settlement and a low impact, non-intrusive, no vibration underpinning system was required. Like many municipalities, the city did not use prime real estate when choosing the location for the water plant; accordingly, the borings indicated soft, low blow-count soils. In addition, the architecture of this plant, which was constructed in 1926, is protected under a historical trust easement. Hillis Carnes, the engineer of record, are both engineers and contractors and have been installing or specifying helicals for a variety of reasons on projects for years. They recognized that the gentle installation of helicals made them the perfect choice for the Salisbury WTP and the extra care required on historic preservation projects.
Click here to read further about helicals for Historic Preservation.
Avon Corporation, the installing contractor, was established in 1979 as a site and specialty contractor serving the Baltimore/Washington area. They have evolved over the years into a multi-faceted GC, who perform most of their work themselves, while still providing specialty services as well. On this project, Avon was able to combine their extensive helical underpinning experience with the sensitivity required for both their Historic Restoration/Preservation work and work in the public sector. Avon Corporation was founded by long term helical veteran Mark Avon, who recently announced his intention to step down soon and pass the baton to his son, Michael. Mark has been instrumental in the growth and acceptance of helicals in this large metro market, taking them from residential repair to million dollar private and public projects. You don’t enjoy a successful track record, such as Mark’s, without a few hard knocks and helical lessons learned along the way. One was a lesson many contractors have learned about protecting yourself in the bidding process, even when you have good soil information and are working with a trusted client.
The borings indicated that the 45 Kip design load (90 K ultimate) would be reached at approximately 35 feet. A 10” 12” 14” lead (3.5” round shaft) followed by a 14” trailer was specified to help achieve the 45-ton ultimate at 35 feet. Mark Avon, the old veteran, insisted on a “add on” provision in the contract just in case the helicals went deeper. “The beauty of helicals,” said Avon, “is that they tell you when you need to terminate the installation based on the torque to capacity relationship, regardless of any predetermined depth indicated by the borings.” Having seen it go both ways, he concluded, “it’s fair to the owner and the contractor to protect yourself and include an add-on to the base bid in case the helicals go deeper.” Ultimately, installation torque was achieved between 55’ and 60’, confirming the wisdom of Avon’s contract provision.
Click here to read the Salisbury MD water treatment plant case history.
Overall, 28 helicals were installed on four buildings to arrest the settlement and stabilize the foundations. Given the complicated nature of site issues on public utilities and existing ground conditions, the IDEAL Counter-Force brackets were encased in concrete for further protection.
Click here for information on the use of helical piles for utilities.
The ownership of Avon Corporation will officially pass on to Mark’s son Mike in February 2024, but Mark plans to make himself available in one crucial aspect of the business for a while longer. “There are a few wildcards in bidding helical projects, such as the depth, which you have to be very clear about, so there are no surprises or unhappy owners or engineers at the conclusion of the job,” stated Avon. “I’ve learned some lessons the hard way and can identify some curveballs up front and spare Mike and his foreman, so that there are no problems on the back end,” he concluded.
