Attachment B Plans~8.pdf

This document is a set of engineering drawings and specifications for horizontal drainage systems at three locations along US Highway 101 (MP 315.89, MP 332.55, and MP 344.44) prepared by the Oregon Department of Transportation for Curry County in July 2025. The project involves the installation of horizontal drains to address slope stability and drainage issues along the Oregon Coast Highway, including the construction of drilling pads, storm sewer pipe installations ranging from 12" to 24" diameter, and connections to existing drainage infrastructure. The drawings detail drilling pad typical sections for two different cases, storm sewer pipe assembly connections, collection line details, and comprehensive plan views showing the locations of multiple drilling pads (labeled A through H) with associated horizontal drain layouts and topographical information.

The project specifications include detailed technical requirements such as drill pad dimensions (25 feet wide by 30 feet long minimum for horizontal drains), construction of temporary access roads, erosion and sediment control measures, and compliance with Oregon Standard Specifications for Construction. The drawings indicate extensive coordination with existing utilities, maintenance of temporary access for future operations, and specific construction sequencing requirements. The project encompasses multiple areas of interest with varying topographical challenges, as evidenced by the detailed contour mapping and cross-sectional views provided in the engineering drawings, suggesting a comprehensive approach to addressing drainage and slope stability issues along this coastal highway corridor.