MAINTENANCE COST EFFECTS OF CALCIUM CHLORIDE TREATMENT AND AGGREGATE ON UNSEALED ROADS

Treating aggregate surfaced roads with chloride dust suppressants or building them up by adding good quality surfacing aggregate is generally believed to reduce surface maintenance costs by creating a more durable surface. This paper quantifies reductions in routine blade maintenance costs by analyzing nearly seven years of cost data from the Johnson County (Wyoming) Road and Bridge Department. Over the past decade, Johnson County has experienced considerable oil and gas drilling, substantially impacting the county’s aggregate surfaced roads. Initial analyses assess the expenditures on the county’s unsealed road network’s highest volume roads, with an average of around 350 vehicles per day and a very high proportion of heavy trucks. The average annual cost of $9,167 per mile per year [$5,696/km-yr] to maintain these roads is high for an unsealed road, though the traffic volume is also relatively high for unsealed roads. The county’s maintenance cost data was used to perform a regression analysis that predicts the dependent variable, routine blade maintenance costs. The independent variables used to predict these costs are: the time since aggregate addition; the time since calcium chloride treatment; traffic; and recent precipitation. This model is used to predict cost savings as a percent of the initial chloride treatment cost. Savings range from 24% at 200 vehicles per day to 79% at 650 vehicles per day. This represents only part of the benefits from these treatments, since lower user costs, safer roads, environmental benefits, and lowered aggregate replacement frequency are additional, but not often quantified, benefits from good quality aggregate and dust suppression.