Finding of No Significant Impact

The NPS signed a Finding of No Significant Impact (FONSI) after analyzing impacts in an environmental assessment (EA).

The selected alternative will resolve the degraded road conditions and also address unstable slopes, pumping of subgrade over impermeable clays, dissolution voids in embankment fill and the subsequent piping of fine fill material, and poor subgrade soils.

Under the selected alternative, the Federal Highway Administration, Central Federal Lands Highway Division (FHWA-CFLHD) and NPS will reconstruct approximately 6.15 miles of Scenic Loop Drive from mile marker 22 to mile marker 28 for longevity and resilience. The selected alternative includes specific treatment options (roadway reconstruction; subgrade excavation, replacement, and stabilization; drainage improvements; structural improvements; and pull-out area improvements) for repairing this section of the road to address existing problems. These treatment options are based on existing data, geological and soil studies, field exploration, survey and mapping of surface features, groundwater and hydraulics analyses, geotechnical analysis, and stability analyses. All proposed treatment options will occur within the project area, with possible exceptions for stormwater drainage requirements.

The selected alternative also includes landslide mitigation and minimization measures, such as stabilization, that will protect natural aesthetics and reduce environmental impacts.

Document Content:

03_2022 03 14_THRO_Appendix D_Wetlands Floodplains SOF.pdf   (3.9 MB, PDF file) MOA Signature Page.pdf   (23.8 KB, PDF file) 02_2022 04 12_THRO_SULR_FONSI_ERRATA_DONI_MOA.pdf   (3.9 MB, PDF file) Disclaimer: Links within the above document(s) were valid as of the date published. Note: Some of the files may be in PDF format and can be viewed using the Adobe Acrobat Reader software. You may download a free copy of from Adobe Systems.