Inspection to verify the elevation of a buried raw water intake

A client contacted Hibbard Inshore in need of an inspection of a new raw water intake pipe that had been installed to draw water out of a major river in order for it to be treated as drinking water for the surrounded community. During the installation, it was suspected that the pipe may have floated in the soft mud at the construction site potentially causing it to be out of proper alignment. The pipe was 16.5” in diameter, was fully flooded, and could not be dewatered for inspection. In order to survey the line, Hibbard Inshore proposed to use a precision depth sensor to determine the elevation of the pipeline along its distance so that it could be compared to the construction drawings. The pipeline could be accessed from a shaft on the shoreline, but the presence of bolts at the elbow into the lateral pipeline had previously prevented an inspection with a crawling ROV. Because of this, it was determined that the best way to access the line would be from the water side at the intake with divers assisting with the insertion of the ROV into the line.

Due to the relatively small 16.5” diameter of the pipe, two of the ROV’s thrusters had to be removed to fit the vehicle inside the pipeline. Hibbard Inshore marked the tether at various increments of length, using the diver to determine the ROV’s exact location within the pipe. High accuracy depth measurements were taken at regular increments to plot a profile of the pipeline along its length. Due to this inspection, the customer was able to determine that the pipeline had not had significant issues with the alignment at installation and would function as specified.

Hibbard Distance vs. Depth