Low Overhead Secant Piles Drilled from within a Shaft-Paper

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The Romeo Arm Interceptor Segment 5 project in Sterling Heights, Michigan, created access to a 50-foot-deep sewer for rehabilitation after a 2016 sinkhole exposed the risk of further ground collapse. Overhead high-voltage power lines and limited site access prevented conventional construction of a deep water-cutoff shaft.<br /><br />The team designed a two-level circular support system: steel ribs and wood lagging for the upper 42 feet, with a 34.5-foot-diameter secant-pile shaft constructed from inside it. This arrangement provided room to operate drilling equipment below the power lines. The 60 overlapping piles formed a stiff compression ring, avoiding internal bracing and external tiebacks. Careful control of pile overlap and verticality was essential to maintain the required effective wall thickness.<br /><br />Installing and assembling a 200,000-pound drill rig within the shaft required a detailed crane and rigging plan. Drilling also had to accommodate changing ground conditions: dry silty clay, water-bearing sand, and deeper impermeable clay. Flooded holes, full-depth casing, and appropriate drilling tools controlled groundwater and ground movement. Spoils, concrete, reinforcement, and steel beams had to be handled within severe space and lifting constraints.<br /><br />Despite reduced production and complex logistics, the secant-pile cutoff wall successfully excluded groundwater and limited movement of surrounding soils, providing safe access to the existing sewer.

Keywords

Romeo Arm Interceptor

Sterling Heights

Michigan sewer rehabilitation

sinkhole

secant-pile shaft

groundwater cutoff wall

deep excavation

high-voltage power lines

steel ribs and wood lagging

drill rig installation