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Helicals for Power Plants
by Pat Haffert
Danbro Vice President
If the various advantages and benefits of specifying helical piles and anchors for deep foundations could be condensed into two words, they would probably be “site friendly.” Never would this characterization be more accurate than when the “sites” in question are in the Energy or Power Production Industries. In the U.S., these industries are individually considered a “natural monopoly” due to high infrastructure cost, capital investments, and other barriers to entry, relative to the size of the market. The quasi-government companies involved in nuclear, coal, or gas-fired plants, and electric generation, transmission, and distribution, are heavily regulated as their product is deemed essential for the public good. Most facilities, located in population centers to reduce transmission costs, are often built in less desirable areas on poor soils. No one wants to live next door to a nuclear power plant, but it needs to be in relative proximity to its service area. Security, safety, and reliability are major concerns and the players in these fields must maintain high standards. Like any highly regulated business, rules and regulations are … well, the rule. With the constraints on construction in these highly restrictive plants and facilities, helicals are often the deep foundation of choice due to the elimination or mitigation of access, mobilization, and vibration concerns. Danbro and its installer network have participated in many projects over the years in this arena. A brief recap of some of these jobs, the motivation for the specification of helicals, and the issues overcome are informative.
Our installers have worked for PECO, Pepco Holdings, Exelon, Delmarva, Con Edison (both 15th Street & Cherry Street in New York City), National Grid in Massachusetts & Long Island, and others in power generation. Delmarva Power’s Edgemoor substation in Wilmington, DE was typical of our substation work. Pads to support new transmission towers and generators needed to be supported on deep foundations as weight of hammer soils were encountered to 85’. Driven piles would have caused unacceptable vibration, required big cranes, and necessitated shutdowns due to overhead safety concerns. Helical piles provided a viable solution to all the concerns raised by timber. A 1 ¾” square shaft with a 6” PVC grout-filled sleeve was installed to depths of 100’ to support the pads while dealing with lateral concerns. No shutdowns were required. https://www.danbro.com/portfolio/delmarva-edgemoor-substation/
Commonly, work for Electric Utilities involves the use of helical anchors as tie-downs. This was the case in Stevensville, MD where electrical power posts were compromised in a storm and needed to be better secured. Environmental sensitivity was paramount, so the work needed to be done from the road to avoid intrusion into wetlands. A custom bracket was produced to facilitate a difficult anchor-to-post connection in a marine environment. https://www.danbro.com/portfolio/cox-creek/
In a related vein, most of our work on Cell Towers has been retrofitting existing towers to provide increased capacity. These applications utilize helical anchors for tie-downs. https://www.danbro.com/?s=Cell+Tower
We also have provided helical support for electrical duct banks for Utilities and in the private sector. https://www.danbro.com/?s=duct+bank.
Helical piles for rack and pipe supports, similar to duct banks, are a popular choice for gas or chemical pipelines. Elizabethtown Gas, PSE&G, and National Grid have all used helicals at their facilities. The usual suspects, namely restricted/confined sites, weak soils, high loads, small equipment, and no vibration drove the decisions to use helicals. https://www.danbro.com/portfolio/maspeth-gate-station-national-grid/
Similar application and restrictions exist in the private sector as evidenced by our multiple visits over the years to the Kinder Morgan chemical plant in Carteret, NJ. https://www.danbro.com/?s=Kinder+Morgan
The Limerick Nuclear Generating Station in Limerick Township, Montgomery County, Pennsylvania is located next to the Schuylkill River, northwest of Philadelphia. Underground tanks needed to be removed and replaced and many of the tanks were adjacent to security barrier walls. There were concerns that the walls may be undermined and experience settlement during the excavation. Helical underpinning piers were chosen for their many already detailed virtues. In addition, plant activities sometimes required “no notice” demobilizations for things like valve inspections, which were easily accommodated with a helical install. Plant rules needed to be strictly followed, including an approximately five minute to ten minute pause for a mandatory safety review between each piling install.
In all instances when working in Power Plants or for Utilities, small equipment with low overhead, no-vibration, and easy mobilization/demobilization were the critical factors in the specification of helical piles and anchors. High loads and poor soils were a given. Safety and security were a must. Many key players in the power industries in the Northeast have come to rely on Danbro, its installation network, and IDEAL helical piles to meet their stringent requirements and ease construction woes!
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