00014024_Attachment E_DDIR_Sitkum Lane.pdf

This document is a Detailed Damage Inspection Report (DDIR) for Emergency Relief (ER) Storm Damage prepared by Shannon & Wilson, Inc. for Coos County Public Works in Oregon, focusing on storm damage at two specific locations: Fairview Sumner Lane at Milepost 4.7 and Sitkum Lane at Milepost 6.7. The report documents storm damage from January 12-19, 2024, when the area experienced 6.78 inches of precipitation, causing shoulder and river bank failures. The project involves emergency and permanent repairs to restore highway facilities to pre-disaster conditions, with proposed mitigation strategies including installing soldier pile retaining walls, removing compromised roadway subgrade, replacing culverts, and restoring road surfaces.

The betterment benefit-cost analyses conducted by Shannon & Wilson demonstrate that the proposed repairs meet the Federal Highway Administration's (FHWA) Emergency Relief Program guidelines. The total estimated repair costs are approximately $1,032,405, with engineering and construction expenses broken down into emergency repairs totaling $1,041.66 and permanent repairs estimated at $1,032,405. The analysis considered multiple scenarios with different recurrence intervals and inflation rates, ultimately concluding that the benefit-cost ratios exceed 1.0 for both sites, justifying the proposed repair and betterment strategies. The project is funded through the Title 23 Emergency Relief Program and is scheduled for implementation in 2024, with a focus on preventing future landslide and road infrastructure failures.