Quantifying Damage from Utility Cuts in Asphalt Pavement by Using San Francisco’s Pavement Management Data

Abstract

The City and County of San Francisco is one of the oldest cities in the United States. Over time, the roads and underground utilities have grown into a complex network of infrastructure that encompasses 1746 centerline km (1,100 centerline mi) of utilities and 18 million m² (195 million ft²) of pavement. The estimated annual maintenance cost of a square meter of pavement is $23.03 ($2.14 per square foot). With a 20-year service life, the streets of San Francisco are worth over $8 billion today. In 1984, the Department of Public Works and pavement experts designed a Pavement Management and Mapping System (PMMS), which was intended to reduce a $78 million backlog of rehabilitation projects and allocate funds for annual street maintenance. Since that time, engineers and repair crews have observed deterioration of the pavement surrounding restored trenches. During the last decade, the city spent an average of $12 million per year for maintenance. Even with an aggressive program of resurfacing and slurry sealing, the backlog of substandard streets has grown by 60 percent. Clearly, the overall deterioration of San Francisco’s streets is not the product of traffic and weather alone. The purpose of this study is to determine if utility trenches are a notable cause of pavement deterioration. Statistical analysis of the condition data reveals that utility cuts result in a significant, immediate decrease in the condition of the pavement. This damage is roughly equivalent to several years of normal wear. City administrators and economists can use this information to quantify the pavement damage and develop policies and financial plans for pavement restoration.

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