Cold Weather Integrity Dig on a Scenic River, Northern Michigan

摘要

A pipeline integrity dig was recently completed during the early winter months of 2013 in the Upper Peninsula of Michigan. In addition to snowfall, extreme temperatures, and difficult access, the integrity investigation required excavation within a designated National Wild and Scenic River flowing into Lake Superior. The integrity investigation required an excavation 9 feet deep and 16 feet in length to expose a section of 30 inch pipeline. The excavation extended out approximately two thirds of the way into the river, requiring several design considerations and extensive environmental permitting. During the initial design phase, two main methods were evaluated for excavation support and river diversion, including sheet piling and cofferdams with trench box support. Due to the high gravel and cobble content of the riverbed, sheet piling was ruled out, and a HEC-2 water profile analysis program was utilized to predict the water elevations of varying storm events for cofferdam placement. Upon completion of design, permitting was approved over the next 12 months by seven different government agencies. The final approval was received in late 2012, and mobilization to the project site commenced in early 2013 due to the nature of the integrity investigation. The contractor, United Piping Inc., completed the project safely and successfully while dealing with temperatures ranging from -18 to 42 degrees Fahrenheit, with wind chills dropping to -42 degrees Fahrenheit. This paper details the initial site evaluation, conceptual plans, hydraulic design, and environmental permitting, as well as the unique construction techniques and safety practices employed to successfully complete the project.