Laserfiche WebLink
• The subgrade soils generally consisted of either natural sandy clays, sandy silts or sandy clay fill <br />materials, which typically classified as CL to ML soils in accordance with the Unified Soil Classification <br />System. The clays and silts will generally provide poor to fair subgrade support for the pavement <br />sections. The clay till materials, natural clays and silts encountered beneath the Haul Road B Extension <br />and Fish Creek Borehole Access Road were typically sandy, dry to moist, stiff and low to moderately <br />plastic. The clay fill materials encountered beneath the West Refuse Pile Haul Road were contaminated <br />with coal, loose to soft, moist to very moist and low to moderately plastic. The namral clays <br />encountered beneath this roadway were generally sandy, moist to very moist and soft to medium stiff. <br />• <br />lJ <br />Free groundwater was not encountered in any of the test holes at the time of this investigation; however, <br />[he test holes were backfilled immediately upon completion of the drilling or excavation. <br />The road base gravel and subbase gravel thicknesses aze shown in [he following table, along with the <br />type of subgrade soil encountered and the location of the test holes. <br />Tes[ Location Road Base Subbase subgrade <br />Hole Denth Deoth Soil Tvoe <br /> <br /> West Refuse Pile Haul Road <br />I West End 0" 0" FILL: Sandy Clay (CL) <br />2 West l/2 -Bottom of Hill 0" 5" FILL: Clay (CL) <br />3 Eas[ 1/2 -Top of Hill 0" 24" CLAY (CL) <br />4 East End 0" 12" CLAY (CL) <br /> Haul Road B Extension <br />5 Eas[ End 9" 12" FILL: Sandy Clay (CL) <br />6 West End 6" 12" FILL: Sandy Clay (CL) <br /> Fish Creek Borehole Access Road <br />13 0.2 miles southeast of Borehole 9" 0" CLAY (CL) <br />l4 0.6 miles southeast of Borehole 6" 0" CLAY (CL) <br />15 1.0 miles southeast of Borehole 5" 0" CLAY (CL) <br />16 1.4 miles southeas[ of Borehole 8" 0" SILT (ML) <br />Pavement Section Recommendations: Based on our observations of the current traffic use pa[terns and <br />condition of the roads, the da[a obtained from the field and laboratory investigations and our experience <br />wi[h similar projects we believe [hat the majority of the problems associated with the subject roadways <br />are at[ributed to inadequate drainage conditions, poor subgrade soils and an inadequate gravel section. <br />For the adequate performance of any roadway, positive drainage must be provided and maintained. This <br />includes periodic cleaning and regrading of the drainage ditches along the edges of the roadways. In <br />addition, the roadway surface should also be graded on a periodic basis to ensure that sufficient crown or <br />super elevation is maintained so that [he gravel surface adequately drains to the ditches. Ponding along <br />[he roadway surface mus[ be avoided. <br />Job No. 99-1004 Northwest Colorado Consultants, Inc. Page 7 <br />