Garrison Dam Spillway – West Abutment Lignite Drain

The project involves the installation of an 812-foot long, 12-inch slotted PVC drain surrounded by a two-stage gravel and sand filter, two cleanouts, and a manhole that connects the new drain to an existing 18-inch PVC collector pipe in the 3A lignite outcrop in the west abutment at Garrison Dam, North Dakota. The work includes mobilization, demobilization, excavation, placement of embankment fill, moisture conditioning, compaction, disposition of excess excavated material, topsoil placement, seeding, erosion control blanket, surveying, and as-built drawings. The contractor will be responsible for the protection of the work area from damage and for the removal of all buildings and facilities constructed by the contractor upon completion of the work. • Installation of 812-foot long, 12-inch slotted PVC drain • Two-stage gravel and sand filter • Two cleanouts • Manhole connection to existing 18-inch PVC collector pipe • Mobilization and demobilization • Excavation and placement of embankment fill • Moisture conditioning and compaction • Disposition of excess excavated material • Topsoil placement and seeding • Erosion control blanket and surveying • As-built drawings