2006-06-12_REVISION - M1978314 (2)

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April 25, 2005 Mr. Carl Luppens Page 4 Truck traffic has a large impact on roads. An American Society of Civil Engineers (ASCE) publication (8) has the following to say about factors affecting surface performance for local low volume roads and streets (LLVRS): "Traffic is one of the most important factors which must be considered. The average dairy traffic (ADT), peak hour volumes, etc., which are important for geometric design are of little value in surface design. The number and type of truck loads which will use the LLVRS over the design life are the most important information for surface layer design. A single 18,000 Ib. single axle load (18 kip SAL) will cause as much damage as 2,000 large passenger cars (~) " A conversation with a Larimer County engineer revealed that paving is the preferred treatment when volumes increase to more than 200 vpd. Larimer County requires paving when volumes are above 200 vpd due to the costs and problems with getting private participation for on-going maintenance. The following statement is included in the Larimer County Transaortation Plan: (8) "According to current State Health Department dust abatement guidelines, rural roads with an average daily traffic volume greater than 200 vehicles should be paved or treated for dust abatement. The County has found that dust abatement loses its effectiveness quickly, so that frequent treatments are needed, causing high maintenance costs. Therefore, this plan includes paving of roads with volumes that require paving or dust abatement. These maximum volume thresholds can be used to define the capacity of gravel roads. A relatively small number of roads in the County have been treated with achip-seal technique. Chip-seal is an inexpensive treatment which creates an adequate roadway surface for small volumes of traffic, but which wears down quickly with higher traffic volumes." A conversation with a Weld County engineer revealed similar procedures. They have found that magnesium chloride (MgCI) and chip and seal do not hold up if volumes are higher than 300 vpd. Weld County uses MgCI treatment between 200 and 300 vpd. When a road reaches 300 vpd, it is included in the county's paving program. Unpaved roads in Weld County typically carry up to 10% trucks. The LSC report (March 2005 -Table 1) shows that the gravel mine would add an unfactored volume of 158 vehicles per day (128 trucks per day) during the peak month. Adding this sRe volume to a future background volume of approximately 125 vehicles per day shows a total volume of just less than 300 vehicles per day (283) with over 45°~ trucks. Based on our research, we have found ample evidence to conclude that CR 5 should be paved because dust treatments (MgCI or chip and seal) at this level of truck traffic will be very expensive. Paving will reduce Routt County maintenance costs and the impact to county taxpayers from this special use. Paving should be seriously considered at a lower level of increase above the existing level of activity, certainly at 50,000 tons per year. Both the memorandum and the LSC report state that CR 5 should be 30-feet wide. County standards (g) normally call for a pavement width of 24 feet, but paving the shoulders to keep the edge of pavement from raveling is justified due to the truck volumes.