Geology Along the Trans-Missouri River Tunnel, Kansas City, Missouri

Abstract

The subsurface geology of the Missouri River Valley at Kansas City is represented in cross-sectional profile to a depth of 400 ft (122 m) from the borehole and construction site data along the alignment of the 2.74 mi (4.41 km) long Trans–Missouri River Water Tunnel. The rock section is divided into two broad categories: a) surficial materials, and b) bedrock. The surficial materials include unconsolidated to poorly consolidated deposits of alluvium and glacial debris (Holocene and Pleistocene Series, Quaternary System). The surficial materials, mostly alluvial sand with lenses of gravel, fill the lower 180 ft (51 m) of the “buried” bedrock valley. The lower several feet of the alluvium is boulders and coarse sand, referred to informally as the “boulder” bed. A deep narrow trench near the center of the bedrock valley is partially in-filled with glacial ablation till, the bottom of the trench is 186 ft (57 m) below the elevation of the floodplain. The section of bedrock (Pennsylvanian System) consists predominately of consolidated beds of limestone and silty to sandy gray shale arranged in cyclical sequences. The exploratory borings from the site investigation for the Trans-Missouri River Tunnel project provided the data to make a detailed stratigraphic analysis of the Pennsylvanian bedrock that included the complex interrelationships of the strata comprising a hydrocarbon-bearing, channel-fill deposit over 100 ft (30 m) thick. The 11-ft (3.4-m) diameter tunnel bore is constructed in bedrock, predominately silty to sandy gray shale and passes through a small oil and gas pool 325 ft (99 m) below the Missouri River floodplain.