Aging Infrastructure

Electric utility executives identify Aging Infrastructure as a critical strategic issue, with the potential to impair financial performance and service reliability. Fifty-six percent of respondents to a recent Black & Veatch survey classified their systems as being "near the end, at the end, past or well past the end" of their service lives. Osmose services and products are designed to extend the reliable and economic service lives of aging poles, towers and other system assets for many additional years past expected.


It is generally accepted that utilities built new lines at a significantly faster pace during the 1950's, 60's and 70's than the pace of replacement for the past thirty years. The result is a "Baby-Boomer" like asset age curve. The components of T&D systems most often associated with aging infrastructure include underground distribution cable, transformers, steel towers and wood poles.


The "perfect storm" depicted by some combines increasing risks to reliability and safety together with significantly increased construction and O&M costs, converging with a departing, aging workforce. Absent any prior or current preventative maintenance intervention, it is expected that these aging components will soon experience higher failure rates and contribute to unacceptable increases in replacement spending.


Age may have a direct correlation to failure rates for some T&D assets. But age alone may not be a good predictor of the future performance for poles or towers. Condition, as defined by decay and corrosion rates, should be assessed together with age distribution data to identify the point when age becomes critical. Below are graphs of age and reject rates for the combined pole plants of two Midwest utilities, prior to initiating preventative maintenance programs.

Age Distribution - Wood Poles

Age Distribution - Wood Poles

There are no significant risks apparent by viewing the age distribution data alone. Potential safety and financial risks do emerge when pole age is combined with the data describing pole condition. In this population escalating reject rates begin within the 20 to 29 year age band. The NESC defines a reject pole as one with less than 67% of its required strength, calling for rehabilitation or replacement. 

Aging Infrastructure Risk - Wood Poles

Aging Infrastructure Risk - Wood Poles

In this population, a large number of poles between 20 and 50 years of age are significantly weaker than their design strength and might be at risk of failing during storms or other unusual load situations. Accelerated pole restoration and replacement will be needed to restore the durability of this population to acceptable levels.


Decay and corrosion rates vary significantly and are dependent on a variety of material and environmental conditions as well as maintenance history. Mass planned replacement of poles or towers based solely on age would be an inefficient investment. The following steps can help to predict potential risks associated with aging structures.

  1. Plot the age distribution of poles or towers
  2. Align historical decay and corrosion rates with the age groups
  3. Analyze the current inspection, maintenance and rehabilitation programs to determine their sustainability

Effective responses to aging infrastructure will likely include strategic use of maintenance, repair and rehabilitation to minimize unnecessary replacement. Osmose can help you design a sustainable program.


Contact Osmose with your Aging Infrastructure questions.