Seismic and Storm-Resistant Ductile Iron Pipe, Valve, and Hydrant System - Part 1

A much-earlier version of this content which did not include diameters larger than 12-inch nor any information about storm resilience was presented at an ASCE Pipelines conference and an AWWA infrastructure conference. Since those presentations, the diameter range has been expanded and testing has been completed. An application to storm environments has also been recognized.

This is the first of six postings in a series and the seventh publication will include the entire presentation. Today, we will look at seismic principles in an overview manner.

Abstract

Half the United States’ population lives in an area of moderate to high risk of seismic activity. In addition to that sobering statistic, counties directly on the coast of the United States account for 10% of the land area but 39% of the 2010 population, a density six times greater than inland areas. That coastal county population is projected to increase 10 million, or 8%, by 2020. (NOAA, 2017)

We have seen in recent hurricanes and floods that pipelines can be exposed, separated, over-deflected, and otherwise compromised. Also, buried water lines are doubly important immediately following a seismic event. Water is the first defense against fires, a major cause of additional destruction following an earthquake. Water is also essential for public health and the sustenance of life. We can exist without power for days, and many have done so, but when our supply of clean water is interrupted, we must soon restore it. This is often manifested through wide-spread disease generally in less developed countries following natural disasters.

This is a paper presenting a new joint assembly for ductile iron pipe, fire hydrants, and valves through 24-inch diameter manufactured by AMERICAN Ductile Iron Pipe and AMERICAN Flow Control that provides for longitudinal joint expansion and contraction within limits of positive restraint, and radial joint deflection. Performance characteristics of the joint assembly will be noted and discussed, and the performance of ductile iron pipe, fire hydrants, and valves during seismic activity and following storm exposure will be presented. A video of the joint in motion may be seen on our website. While this joint was originally intended for seismic application, numerous water professionals have commented how additionally suitable it is for more traditional demanding environments such as hurricane and flood zones.

Introduction

While water utilities and communities strive to replace rapidly aging water service infrastructure and install new appurtenances to supply populations for generations to come, it is of the utmost importance that owners and operators be proactive and responsible with material and product selection.  It is important to build with quality and for the long-term. A responsible approach helps ensure current budgets are wisely allocated to materials that are long-lasting and dependable, standing the dual tests of time and environment. For example, when choosing waterworks materials, one is responsible to consider the conditions in which those products must perform and also what environmental stresses and challenges they may experience during their time of service. Obvious conditions include static pressure, internal surge and external transient stresses, depth of cover, fatigue resistance, and other fairly well-known variables. Often overlooked performance criteria is the ability to withstand seismic activity, more commonly known as earthquakes. Fortunately, this need is growing in awareness as is the need for pipelines to withstand exposure during washout conditions.

At the 2014 ASCE Pipelines conference, the closing plenary session was led by Mark Knudson of Tualatin Valley Water District in the Portland, Oregon, area. (ASCE Pipelines Conference Program, 2014) In this presentation, Mr. Knudson presented sobering facts about the impact a major seismic event will have on lives, the economy, and even national security. In 2012, the Oregon legislature charged the Oregon Seismic Safety Policy Advisory Commission to develop a strategic plan to improve Oregon’s ability to withstand and recover from a 9.0 temblor. The report predicted extensive damage to regional water supply systems and the near certainty of months to restore service. In his address, Mr. Knudson indicated some models predicted as long as two years for complete restoration of water services.

Given recent floods and hurricanes, some insurance agencies are asking utility operators to harden their underground infrastructure to withstand the demands of once-in-a-generation weather. This joint system does that.

Seismic Overview

We all know water is crucial for public health. In fact, clean water is the greatest advancement in public health in the history of mankind. We can inconveniently get along without power for some time, but not drinking water. The lack of safe and clean drinking water following an earthquake can result in widespread disease and death. (Lemonick, 2011)

Figure 1. Damage from a post-quake fire is often more than damage from the seismic event alone.

Because container water and portable treatment processes can be brought in, one can say that water for fire protection is more urgent immediately after an earthquake than clean drinking water. Regardless, the availability of a functioning public fire protection system and water supply following an earthquake will significantly mitigate fire damage and death toll. Hence, the need to further improve the resilience of common water distribution and fire protection systems, irrespective of the potential cause of interruption.

Why is this important beyond isolated areas and the usual seismic-area suspects? The United States Geological Survey says 50 percent of the United States’ population lives in an area subject to moderate or severe risk of seismic activity. (Jaiswal, 2015) Further, the Washington Post recently reported that 28 million Americans live in areas of high seismic potential and 58 million in areas of moderate potential. (Izadi, 2015) No matter which assessment you consider, a sizable portion of our population and economy is at some risk. Figure 2 provides a visual representation of seismic risk in the United States.

Figure 2. Seismic risk in the United States.

Seismology 101

Let’s look now at an overview of seismic phenomena. Generally speaking, there are three types of seismic activity: shaking of the ground, fault displacement or ground surface rupture, and ground failure such as liquefaction or landslides. (Housner, n.d.)

Damage from shaking is proportional to horizontal and vertical ground acceleration plus its duration. Fault displacement, or rupture of the ground, is when the earth moves up, moves down, or moves apart. Ground failure can occur at the surface or below ground and involves less solid mass, in other words material such as silt, sand, or gravel. This is common in areas of landfill, whether deep or shallow. Many high-risk west coast cities have substantial property built on fill. Figures 3, 4, and 5 are representative of these three phenomena.

Figure 3. Results of ground shaking.

Figure 4. Results of fault displacement.

Figure 5. Results of ground failure in the form of liquefaction. 

In each of these manifestations of seismic activity, flexibility and strength are paramount to resilience and survivability. Buildings are designed and built to both sway and be strong. We should do the same for our underground public water supply by designing it to be flexible and capable of deflection and also resistant against end-wise separation. Those attributes protect service from wash-outs, too, and the AMERICAN Earthquake Joint System does just that.

Next week in Part 2, we will look at a specific earthquake which many remember and I survived, as well as the utility systems in that area. Feel free to Like, Share, Comment, and also to contact me.