Rehabilitating Houston’s Above-Grade, Large-Diameter Water Lines (Source: WaterWorld)
By Christine Kirby, P.E.
Houston is the fourth most populous city in the U.S. with a population of about 2.3 million extending across 600 square miles. The city produces and distributes more than 146 billion gallons of water per year, enough to fill the Astrodome four times per day. Within the massive water system comprised of water lines from 4 inches to 96 inches in diameter, there are more than 300 above-grade crossings that are 12 inches in diameter and larger, some of which have been in service for nearly 80 years.
In 2012, the city’s corrosion engineering consultant inspected every above-grade crossing to determine the condition of the existing coating, and determine if hazardous materials, including heavy metals and asbestos, were present. Of the crossings that were inspected, various types of coatings were found, including paint, tape wrap and coal tar enamel.
During this study, more than 200 crossings were identified for rehabilitation or replacement, with 21 of these crossings being 24 inches in diameter and larger. In 2014, as part of the city’s Surface Water Transmission Program (SWTP), Lockwood, Andrews & Newnam Inc. (LAN), a planning, engineering and program management firm, was hired to conduct a field assessment and provide recommendations for the 21 large-diameter crossings.