Laserfiche WebLink
The existing road base materials classified as poor to good road base materials and will provide vaziable <br />• degrees of support. For design purposes, varying strength coefficients were used for the existing road <br />base materials. Strength coefficients ranging from 0.08 to 0.10 were used for the existing road base and <br />subbase gravels in [he design of the new gravel sections. <br />The subgrade soils obtained were somewhat vaziable and generally consis[ed of clays or silts, which <br />classified as CL to ML soils in accordance with [he Unified Soil Classification system and A-6 to A-7-6 <br />soils in accordance with [he American Association of Stale Highway Transportation Officials (AASHTO) <br />classification system. Using the group index values obtained on the subgrade soil samples, a correlated <br />soils resilient modulus of 5000 psi was used in the design process. <br />It is our understanding that the Fish Creek Borehole Access Road is not a haul road and is generally <br />subjected to a very low traffic volumes, typically consisting of pickup trucks and occasional delivery <br />tmcks or construction vehicles. Therefore, we have assumed an 18 kip equivalent single axle loading <br />(ESAL) of 6,500 for the access road. However, it is our understanding that the Haul Road B Extension <br />and the West Refuse Pile Haul Road will be subjected to daily trips of haul trucks and off-road earth <br />moving equipment, such as front end loaders and dozers. Therefore, we have assumed an ESAL of <br />120,000 for these roads. <br />The gravel sections presented below aze based on the field investigation, laboratory test results, the <br />assumed traffic loadings and the AASHTO Guide for Design of Pavement Structures (1986). The design <br />• calculations aze shown in Appendix A. <br />Haul Road B Extension: Based on the [wo tes[ holes advanced along the Haul Road B Extension, it <br />appears that this roadway had 6 [0 9 inches of existing road base gravels overlying approximately 12 <br />inches of subbase gravels. The road base and subbase gravels were in fair condition; therefore, strength <br />coefficients of 0.10 and 0.08 were used for the existing road base and subbase gravels, respectively, in <br />the design of the new gravel section. Based on our calculations, we recommend that this roadway be <br />surfaced with an additional 4 inches of Class VI base course. <br />Based on the horizontal and vertical profiles provided by the client for this roadway, i[ appears [hat the <br />width of the subject roadway ranges from approximately 20 to 25 feet and has been constructed with a <br />horizontal grade ranging from 0.5 to 3 percent down to the west. The crown on the roadway is variable <br />and should be improved when the new base coarse materials area added. <br />Fish Creek Borehole Access Road: Based on the four test holes previously advanced along the Fish <br />Creek Borehole Access Road, it appeazs that this roadway had 5 to 9 inches of existing road base gravels. <br />The road base gravels were in fair to poor condition; therefore, a strength coefficient of 0.08 was used <br />for the existing road base materials in the design of the new gravel section. Based on our calculations, <br />we recommend that this roadway be surfaced with an additional 6 inches of pit run gravels and 3 inches <br />of Class VI base course. <br />Horizontal and vertical profiles were not provided for this roadway. Therefore, we did not address these <br />• issues in this repott. <br />lab No. 99-0OOA Northwest Colorado Consultants, Inc. Page 4 <br />