By Ashley Beyer
When natural disasters, power surges, accidents, or general equipment failures threaten the reliability of the power grid, maintenance crews must be able to quickly and safely access transmission lines and substations to make repairs. Designing resilient energy infrastructure that ensures power companies have a reliable, regular supply of energy and contingency measures in place in the event of a power failure is crucial to their business and the communities they serve.
Build sustainable roads for utility transmission and substation access
Accessing sites in remote or undeveloped areas can present several challenges for the energy industry when it comes to building, operating, and maintaining power transmission lines and substations. Soft soils and low-water crossings can make it difficult for utility vehicles to safely and effectively reach sites for routine maintenance and emergency repairs. The Presto GEOWEB 3D Soil Stabilization System is ideal for shallow ground improvement applications and can easily be incorporated into unpaved access roads for transmission lines and substations. The geocells, made from an all-weather high-density polyethylene (HDPE) material, are durable, chemical resistant, and outperform standard two-dimensional geosynthetics through lateral confinement of infill materials, facilitating what is known as the “mattress effect” for distributing loads across weak subgrades.
The system offers an economical way to construct low-maintenance unpaved access roads that are fast to install and require less maintenance than their unreinforced counterparts. The geocell-confined aggregate is stable and resistant to shoving and movement that can occur with unpaved access roads subjected to heavy-traffic loading conditions. With the system, roads are built with 50% less aggregate to support heavy vehicles with minimal environmental impact. The use of low-cost, local infill—such as sand or limestone—lowers the overall project cost, and the geocell reinforcement extends the life of the unpaved road and reduces annual maintenance costs.
Reduce touch and step hazards at substations
Aggregate is commonly used for electrical substation pavements and transformer pads to create a safe, nonconductive insulation layer between workers and the ground. This aggregate must contain fines to create a stable surface to resist heavy vehicle stresses, and the presence of these fines can create touch and step hazards. The system allows the use of an open-graded base course (OGBC) with no fines, providing greater surface permeability and a more stable driving surface that resists rutting.
The permeable geocell confinement system delivers exceptional drainage, which prevents the accumulation of dangerous surface water ponding. Roads and substation pads constructed with the geocell system require virtually no maintenance and provide a safer environment for workers.
Case study: Geocells stabilize soil and manage stormwater for hospital power line installation
The Alabama Power Co. (APC) saw a need to install a second substation to provide a reliable alternative power source for Providence Hospital in Mobile, Ala.; however, wetlands near the project site complicated installation of the substation and power line. Construction of the access road was also wrought with environmental and regulatory concerns from citizens and local officials.
Construction is strictly governed in wetland areas, so APC could not fill the wetland for soil stability. City of Mobile regulations required the project to establish stormwater retention areas due to its size. Rather than retain the water in ponds, however, APC used Presto Geosystems’ GEOWEB confinement system to stabilize the soil to ensure the access road was permeable in the upland portion of the project.
The geocellular system stabilizes the aggregate, preventing movement under vehicle loads, and allows stormwater to drain into the soil rather than runoff and create problems for residents and the environment.
Because water so easily infiltrated the access road, the City of Mobile did not require APC to build the retention pond per its regulations. Had an impervious surface been installed, stormwater would deviate from established flows, and nearby residences likely would have complained about stormwater on their properties.
The substation provided Providence Hospital with two sources of power. In the event of a power failure at one, electricity would shift to the other, keeping the hospital’s vital machinery online.
This article originally appeared on the Presto Geosystems blog, www.prestogeo.com/blog.