Leak Location and Repair Cost for Underground Heat Distribution Systems

Abstract

The expected cost of leak location and repair is estimated for shallow trench and directly buried underground heat distribution systems. Leaks in shallow trench systems can be found during a visual search using a bisection method to determine the sequence of slabs to be lifted, while directly buried systems generally require sensors and often extensive excavation. The cost advantage for shallow trench systems is estimated to be $4,863 per mile per year (expressed in year 1985 dollars) for the baseline scenario, taking into account observed (historical) differences in average failure rates. If directly buried systems could somehow be guaranteed to have the same failure rate as shallow trench systems, the cost advantage would become negligible. Several scenarios regarding sensor effectiveness were entertained, with the cost advantage changing by less than 20%. Differences in capital costs and operating costs reported in other studies are offered for purposes of comparison. Since operating costs due to heat loss increase dramatically when there is a leak in a directly buried system, it is imperative that regular inspections be carried out to discover leaks and permit timely location and repair.