Iowa Highway 86 vertical alignment improvement study

761047984Environmental assessment and section 4(f) de minimis impact finding.PDFTech ReportSTP-086-1(10)--2C-30Environmental impactsEnvironmental impact analysisHighway planningTransportation planningCounty roadsPrimary highwaysState highwaysIowaIowa. Dept. of TransportationIowa. Dept. of TransportationUnited States. Federal Highway AdministrationNTL-ENERGY AND ENVIRONMENT-Environment ImpactsNTL-PLANNING AND POLICY-PLANNING AND POLICYUS Transportation CollectionThe Iowa Department of Transportation (Iowa DOT) and the Federal Highway Administration (FHWA) are evaluating potential alternatives to maintain, improve, or replace a 3.9-mile segment of IA 86 from Iowa Highway 9 (IA 9) to near the Minnesota border within Dickinson County, Iowa (the Project). Iowa DOT proposes to improve IA 86 by constructing two 14-foot-wide driving lanes, and 8-foot-wide shoulders (4 feet paved and 4 feet granular). Foreslopes are a graded part of the roadway cross section that extend outside of the shoulders to ensure the stability of the roadway and to provide a reasonable opportunity for recovery of an out-of-control vehicle. Foreslopes having a grade of 6 feet horizontal for each foot of vertical decrease (a 6:1 ratio) would be constructed from the shoulder, and a 3:1 ratio from the edge of the 6:1 slope to drainage ditches. However, 4:1 foreslopes from the shoulder to the ditches would be constructed in areas where both sides of IA 86 are bordered by designated natural lands